Antony van Leeuwenhoek and his "Little animals"; being some account of the father of protozoology and bacteriology and his multifarious discoveries in these disciplines;

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LONDON.

Lip VAN DE

20 SA

ANTONY van LEEUWENHOEK
AND HIS “LITTLE ANIMALS”

BEING SOME ACCOUNT OF THE FATHER

OF PROTOZOOLOGY AND BACTERIOLOGY

AND HIS MULTIFARIOUS DISCOVERIES
IN THESE DISCIPEINES

COLLECTED, TRANSLATED,
AND EDITED) “FROM is
PRINTED WORKS, UNPUB-
LISHED MANUSCRIPTS, AND
CONTEMPORARY RECORDS

BY

CLIFFORD DOBELL, F.R.S.

Protistologist to the Medical Research Council, London
Foreign Member of the R. Accademia dei Lincei, Rome
Sometime Fellow of Trinity College, Cambridge

PUBLISHED ON THE
300th ANNIVERSARY OF HIS BIRTH

HARCOURT, BRACE AND COMPANY

383 MADISON AVENUE, NEW YORK

MCMXXXII

ALL RIGHTS, INCLUDING THOSE OF

TRANSLATION OR REPRODUCTION IN

OTHER LANGUAGES, RESERVED BY
THE AUTHOR

PRINTED IN GREAT BRITAIN

FRATRI CARISSIMO

D’ARCY WENTWORTH THOMPSON
SCOTO
HAEC ACTA MORTVI BATAVI
D.D.D.
EDITOR ANGLVS

anmatcvivm ELEPHANTI
NECNON

FRATERCVLO AEQVE CARO NOTHOQVE

PAUL bE KRUIF
AMERICANO

ANIMALCVLVM ANIMALCVLO

CONTENTS

PAGE
The Epistle to the Reader : : : : : : 3 ; i
PART I.—LEEUWENHOEK
The Life of Antony van Leeuwenhoek . 5 ‘ : eS)
PARRY i— THe. LITTLE ANIMALS ”
Chapter 1.—The First Observations on “ Little Animals ”’
(Protozoa and Bacteria) in Waters . : : ; . 109
Chapter 2.—EHpilogue to Letter 18. Further Observations
on the Free-living Protozoa and Bacteria . : . WOK
Chapter 3.—The First Observations on Entozoic Protozoa
and Bacteria ; ; : : é : : ‘ aly!

Chapter 4.—The Later Observations on Free-living Protozoa 256

Elucidations and Annotations

(i) Leeuwenhoek’s name : : : : ; 3° 300

(ii) Leeuwenhoek’s language ’ ; , : : 305

(iii) Leeuwenhoek’s microscopes and microscopical mations 313

(iv) Leeuwenhoek’s dwelling . , , eas

(v) Leeuwenhoek’s draughtsmen . : ; : ‘ . 342

(vi) The portraits of Leeuwenhoek : : ‘ . 3846

(vii) Leeuwenhoek’s “ first 27 unpublished eee: ig : . 306

(viii) Leeuwenhoek’s seals : : ; , ; 359
Envoy : Leeuwenhoek’s Place in Protozoology and Bacteriology . 362
Short List of Leeuwenhoek’s Writings . : : : : . 888
Other References and Sources . ; ‘ : : : ‘ . 398
Acknowledgements. : ' : ‘ ; : é : . 423
Index , ‘ A ; ; ' : ; : ; : . 426

42976

CHRONOLOGICAL NOTE

The Gregorian correction of the Julian Calendar was not made simul-
taneously in England and the Netherlands, and during Leeuwenhoek’s
lifetime two different systems of dating—known as ° Old Style ” and “ New
Style ’’—were current in these countries.

“New Style” dating was adopted in the Provinces of Holland (wherein
Delft is situated) and Brabant on 5 December 1582, which was called the
15th of the month—thus advancing the Calendar by 10 days: though other
Provinces of the Netherlands (Gelderland, Utrecht, Overyssel, Groningen,
Friesland) did not recognize the new system until 1700. But in England
the change was made even later, for it was not until 1752 that the Old
Style ” was abolished by Act of Parliament. The discrepancy between the
Julian and the Gregorian systems having become 11 days in the year 1700,
the English Calendar was corrected by calling the 3rd of September (1752)
the 14th. At the same time, the old Anglican method of commencing the
year on March 25 (instead of January 1) was ended. Good Friday was
New Year's Day in Delft before 1575, but not afterwards.

All Leeuwenhoek’s own dates are therefore “New Style’’, and agree
with modern reckoning. English dates of his period are, however, usually
“Old Style’, and consequently to be understood as 10 days (from 1632 to
1700) or 11 days (from 1700 to 1723) later in actual time. In the present
work all dates of importance are given, as far as possible, in present-day
form (N.S.) unless old-style dating (O.S.) is indicated.

(vi)

LIST OF PLATES

I.—Antony van Leeuwenhoek : from the mezzotint portrait by

J. Verkolje (1686). , ; Frontispiece
II.—_Leeuwenhoek’s birthplace . : : ; facing page 20
IIJ.—Registration of Leeuwenhoek’s baptism . : : ota
1V.—Oude Delft : . : ; . 25
V.—Leeuwenhoek’s bill to P. Heeeieecer (1659) é ' . 80
VI.—The Town Hall of Delft . j : : F 4 3S) oe
VII.—Vermeer’s View of Delft . : 2 : : ; . | do
VIII.—Portrait of Henry Oldenburg, Sec. R. S. . : : > oS
IX.—Portrait of Dr Reinier de Graaf ‘ 40
X.—Last lines of Leeuwenhoek’s Letter 2 (MS. 15 mae 1673) 49,
XI.—Portrait of Leeuwenhoek: from Verkolje’s oil-painting . 49
XII.—Miniature portrait of Leeuwenhoek by J. Goeree (1707) . 76
XIII.—Last lines of Maria’s letter to the Royal Society : , 99
XIV.—The Old Church at Delft . ; : : 5 a Oe
X V.—Leeuwenhoek’s tomb in the Old Oia ‘ : : ec
XV1I.—Portrait of H. Poot by T. van der Wilt . J 5 HO?
XVII.—Facsimile of a passage from MS. of Letter 6. : 110
XVIII.—First page of Oldenburg’s printed translation of Letter 18. 113
XIX.—Facsimile of first page of MS. of Letter 18 ; : eG
XX.—A House in Delft, after J. Vermeer . : : . 125
XXI.—The Shore at Scheveningen, after J. v. Ruisdael . : s) £29
XXII.—Illustration to Leeuwenhoek’s Letter 32 . , ; PtSi
X XIIJI.—Leeuwenhoek’s pictures of Protozoa in Frogs . ; 233
XXIV.—Leeuwenhoek’s pictures of Bacteria in the Human Macen 239
XXV.—A page of the MS. of Letter 39 . : : 240
XXVI.—Leeuwenhoek’s figures illustrating his account ee rane
(Letter 122) . 259
XXVII.—The figures of Dances ind Aes (Lewes 125 é 144) 263
XXVIII.—The Animalcules on Duckweed . ; F 277
XXIX.— Last page of Letter about Duckweed (MS. 25 Thee 1702) . 285
XXX.—The figures of Anthophysa vegetans (MS. 5 Feb. 1703) . 289
XX XI.—Leeuwenhoek’s “ microscope’”’ . : F ; J . S28

XX XIT.—Leeuwenhoek’s seals. : : E : . . 7 SoG
(vii)

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fae VAUTHOR'S © EPISTLE TO... THE . “READER:
Introducing Mynher ANTONY van LEEUWENHOEK
of Delft in Holland, Fellow of the Royal Society of London
in England.

Dear READER: I know full well that you and everyone else
must have met Mr van Leeuwenhoek many a time before ; but
please let me reintroduce him to you, for he is a man worth
knowing more intimately. Though he was born exactly 300
years ago he ws still very much alive, and would be glad to make
your better acquaintance—provided only that you are “a true
lover of learning” (as of course you are). But as his fleshly
body ceased to work and dissolved in dust about a century
before your grandfather came into the world, and as he himself
knows no language but very old-fashioned Dutch, I think
you will agree that an introducer and interpreter may not be
superfluous and might even be helpful? So please let me tell
you how I first met Mr Leeuwenhoek, and why I now presume
to take these onerous offices wpon myself without any obvious
call or qualification. Let me tell you why I, an almost un-
known living Englishman, wish to make you more nearly
familiar with a famous old Hollander who wrought and died
long before we were born.

When I was a very young man I began to study, for my
own amusement, the microscopic creatures in organic infusions ;
and in the cowrse of some desultory reading I then, to my
surprise, discovered—a thing I ought, naturally, to have known—
that these “ little animals” had originally been observed more
than two centuries earlier by somebody called, more or less,
Leeuwenhoek. (J say“ more or less” because I found his name
spelled in a great variety of ways: and being then only some
20 years of age, and having no knowledge of Dutch, I could not
tell which way was right.) On looking into the matter, I found
of course that this man with the strange patronymic was really
a well-known figure in the History of Biology—notwithstanding

I!

2 LEEUWENHOEK AND HIS “LITTLE ANIMALS”’
my teachers had never told me of him (possibly, I now think,
because they were wnable to utter his name). I found that he
was honourably mentioned as a pioneer in many different fields
of scientific research—his discovery of the Protozoa in infusions
being only one of his many noteworthy achievements. An odd
circumstance, which (I remember) struck me forcibly at the time,
was that this old Hollander—for some reason unexplained—
apparently made a practice of publishing his observations in
English in our Philosophical Transactions, and was himself
actually a Fellow of our own Royal Society of London. This
then seemed to me very queer and inexplicable: yet had it not
so happened, the present book would never have been written.

After this my first meeting with Leeuwenhoek, 2 chanced
that my studies led me away from the protozoa in infusions to
those living inside frogs. I spent two or three painful years in
their pursuit ; and in reading up the writings on the subject, I
found again, to my astonishment, that the earliest observations
on these organisms too had been made by the same person—
Leeuwenhoek once more. This revived my interest in hin, and
caused me to look into his publications anew. But I made little
progress in my inquiries, because his original records were at that
time inaccessible; and the second-hand sources of information
then at my disposal were mostly worthless and contradictory—
different authors supplying different references and statements,
most of which turned out to be so incorrect that they led me
nowhere. When I tried to find out something about the man
himself, I met with no better success. Most writers agreed m
calling him “well-known” or even “ celebrated”, and many
called him “microscopist”’ or “naturalist” (all excellent epithets,
as I now know). But some people said that he was “ a maker
of lenses” and even “ the inventor of the microscope” (which
even then I knew to be wrong), while others said he was a
“physician”: and had I then looked further, I should have
found that still others called him “ surgeon” and even“ Doctor”
and “ Professor.” Yet all writers seemed to be wn agreement on
one point, expressed or implied: and that was that they knew
next to nothing about Leeuwenhoek himself, despite his alleged
celebrity. No two writers gave the same account of him—even
when copying one another.

My own next researches (forgive me, dear Reader, for ob-
truding myself in this fashion : it is unfortunately necessary for
the present narrative) were largely concerned with the Bacterta—

THE AUTHOR'S EPISTLE TO THE READER 3

including those in the human mouth, and more especially the
Spirochaetes. And here again I found—this time to my amaze-
ment—that all these organisms also had first been seen and
described by Leeuwenhoek. It seemed impossible ; so again I
attempted to ascertain who this person really was, and what
precisely he had discovered in this connexion. But I failed
once more.

Somewhat later, I turned my attention particularly to the
intestinal protozoa of man—only to find that thevr first observer
was, incredible though it seemed, again Leeuwenhoek. :
To make a long story short, I continually found that whatever
protozoa or bacteria I worked at, I was always forestalled and
led back to the same mysterious and eluswe indiwidual who had
somehow succeeded in registering the first observations on almost
every kind of microbe I attempted to investigate.

It is now some 25 years since I first began to try and find
out something about Leeuwenhoek and his discoveries in proto-
zoology and bacteriology. The task has always been hard, but
because of my personal interest it has never been irksome. My
interest has, indeed, grown with my knowledge; and the more
I have found out, the more I have ever wanted to find out about
this truly marvellous man and his works. From the very
beginning, I have been able to get little or no help from the
writings of others (most of whom merely led me astray), so that
I have always had to do the best I could for myself. Conse-
quently, the first few years of my labours were woefully barren :
they yielded me little else than imperfect copies of Leeuwenhoek's
publications in Latin, and their garbled English version—the
“Select Works” of Hoole. As I soon detected the shortcomings
(also the merits) of the latter, I applied myself at first to the
study of the “ original” Latin texts.

Thad barely begun to read the Latin letters of Leeuwenhoek,
however, when I met with a serious setback. I found that
these letters were not written in the Latin which I learnt at
school, but in a language I could scarcely wunderstand—a
language bristling with difficulties for a man like myself, whose
‘“ Latin” was little more than a fading recollection of the
dialect used by writers of the Augustan age. Yet long before
I had mastered Leeuwenhoekian Latin I received a far worse
shock: I discovered that Leeuwenhoek himself knew no Latin
at all (of any kind or sort), and that all his own writings were
really in Dutch. Profoundly discowraged, I therefore began a
new search for the Dutch originals.

4 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”

When I finally succeeded in obtaining a copy of the Dutch
edition of Leeuwenhoek’s works, 7¢ was only to find that I
could make out hardly anything of what he had written: for
af the instructors of my youth had taught me a Latin in-
adequate to my needs, they had never even pretended to teach
me one single word of the languages spoken in the Netherlands.
So I made a foolhardy attempt to learn Dutch by myself—
using Leeuwenhoek’s printed Dutch letters as a text, and
checking my interpretations by the Latin editions of the same
letters and the old Dutch Bible. When JI had made some little
progress in this study, and had got a smattering of seventeenth-
century Dutch and Latin, I made the worst (and the best)
discovery of all: I discovered that Leeuwenhoek’s own original
Dutch letters—written by his very own hand, and many of
them even now unpublished—are still, for the most part, extant
among the manuscripts belonging to the Royal Society in
London. I therefore went, all excited, to consult them
and found that nearly all those most important for my purpose
were inscribed in a script which, for all I could make of tt,
might just as well have been Hebrew or Arabic. I could not
read a single word.

This was a blow which staggered me completely: and as we
were then in the midst of the Great War, and my time was
more than fully occupied with other and more urgent duties, I
momentarily gave up all hope of ever being able to read
Leeuwenhoek in the original.

But after the War, when my own work was temporarily at
a standstill, I returned one day—‘ merely out of curiosity” (as
he would say)—to the library of the Royal Society, and puzzled
over those tantalizing manuscripts. After a bit, I found that
I could make out a word here and there: in a few days I could
even read, now and then, a whole sentence. So I became—
almost unconsciously—an amateur palaeographer, and at last
attempted to find and decipher and copy all the passages which
specially interested me in Leeuwenhoek’s letters. T'o an un-
prepared and wholly inexperienced person like myself it was a
task nearly as great as that which faced the first readers of the
Rosetta Stone, and it was accomplished by similar methods.
You may laugh, dear Reader, but it is true. You, who are
doubtless familiar with Dutch and Latin and English of all
periods, and for whom the deciphering of ancient manuscripts
holds no terrors, must please try to put yourself in my ignorant

THE AUTHOR’S EPISTLE TO THE READER 5

position and consider my handicaps. I knew—to my shame
and sorrow—little Latin, less Dutch, and not much more
Finglish of Leeuwenhoek’s time. I had nobody to help me,
and therefore made the most pitiable mistakes. But I perse-
vered, and ultimately attained my object (more or less). I also
learnt afresh the truth contained in the Dutch-Latin proverb
nil volentibus arduum—or, as we say in English, ‘‘ where
there’s a will there’s a way.”

When I had finally discovered where to look for Leeuwen-
hoek, my serious work began. Having possessed myself—after
long search and many bitter disappointments—of perfect copies
of the Dutch and Latin editions of his writings, and with all
the Royal Society’s manuscripts and Transactions available
for study, I began my real hunt for the man himself and his
protozoological and bacteriological knowledge. Whilst reading
the various versions of his numerous letters, in quest of passages
relating to protozoa and bacteria, I learnt much about himself
and his multifarious other activities. In addition, naturally,
I ransacked every accessible book and paper and manuscript
for further information. And at last, after encountering
obstacles at every turn, and surmounting difficulties which often
seemed at first insuperable, I met Mynheer Antony van
Leeuwenhoek his very self; and he told me all—or nearly all—
that he knew about the Protozoa and the Bacteria. To my
surprise and delight I found not only that he knew no language
but Dutch, but also that he knew no “ science”; for he was
merely an ordinary shopkeeper, holding a few minor municipal
appointments, in the little old town of Delft. In the world of
science he was no better than an ignorant and bungling
amateur—self-taught but otherwise uneducated. He did every-
thing by himself, alone and unaided: so that when he wished
to make a microscopical discovery, he had first to make himself
a nucroscope; and when he wished to describe this discovery, vt
often turned out to be something so novel that he had no words
wherewith to express it. Consequently, though we both strove
hard, I often found it very difficult to understand what he kept
trying to tell me: for he was terribly short of words, and could
only talk in the commonest and most ungrammatical and old-
fashioned language—often using expressions which are not in
any modern Dutch-English dictionary (or if they are, have now
a different meaning). How such a man ever became famous as
a “scientist,” and even a Fellow of the Royal Society of
London, is a curious story which I shall retell you presently.

6 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS”

My own chief interest in Leeuwenhoek has always been in
his observations on protozoa and bacteria—as I have already
told you. But this is because these “ little animals’ (as he
called them) have engaged my own attention all my life, being
the favourite objects of my own researches. His own tastes
were more catholic : indeed, he studied almost everything that
can be looked at through a lens, and thereby found out some-
thing new about it too. His inquisitiveness was insatiable, and
his discovery of the Protozoa and the Bacteria was merely an
incident in a life crowded with discovertes—real and imaginary.
For example, Leeuwenhoek’s observations on insects, rotifers,
and a host of other ‘‘animalcules,”’ are equally remarkable ;
his researches on blood-corpuscles and the capillary circulation
are already classics; his comparative studies of spermatozoa
now stand as a landmark in the History of Biology; his dis-
covery of parthenogenesis (in aphids) and of budding im an
animal (Hydra) are too notorious almost for comment : while
his other investigations in anatomy, histology, physiology, em-
bryology, zoology, botany, chemistry, crystallography, and
physics, only await editors for their proper appreciation. He
made the maddest experiments, and attempted to see things that
nobody would now even dream of seeing. I imagine, for instance,
that nobody before (or after) Leeuwenhoek ever thought of
watching the explosion of gunpowder under the microscope - yet
he devised an apparatus for this purpose, and though he nearly
blinded himself he succeeded in seeing what he wanted. And
he actually discovered protozoa and bacteria in organic infusions
in the course of a crazy attempt to find out, by the microscopic
examination of macerated peppercorns, why pepper ts hot !

But these are only a few of Leeuwenhoek’s astonishing
doings, and I need say nothing further about them here. In
the pages which follow I merely attempt to assemble and edit
all his observations on protozoa and bacteria. Originally I
collected—simply for my own information and pleasure—every-
thing that I could find on these matters, both published and
unpublished, in his extant writings. I had no thought of
making a book for others to read. Yet after a time I found
that I had amassed a body of records which seemed to me so
surprisingly great and original, that I felt it my duty to share
my findings with other protozoologists and bacteriologists : so
my own private notes gradually grew into the work now before
you.

THE AUTHOR’S EPISTLE TO THE READER 7

At first I thought merely to print or reprint all the relevant
passages 1n Leeuwenhoek’s writings in the languages (Dutch,
Latin, or English) in which they now survive: but on second
thoughts I realized that this would be futile. I realized that it
would be useless, for example, to reprint the Dutch and Latin
words already accessible to everybody, and by everybody still
unread or misunderstood. So I resolved to put everything into
Finglish, in order that every man who can read my mother-
tongue shall henceforth be able to read and understand what
Leeuwenhoek himself recorded in his own language. My
translations of his words are, I know, imperfect : but they are
to be excused as a first attempt to reduce all his protozoological
and bacteriological knowledge to a uniform and intelligible
modern system, and vn every case they are accompanied by exact
references to original sources, so that you can—if you have the
time and patience—verify my own words for yourself. A certain
amount of editing and rearrangement has been unavoidable,
and indeed essential to my plan; but I have, I hope, reduced
my apparatus criticus to a minimum.

The difficulties which I have encountered in translating
Leeuwenhoek into modern English—or, at least, into English
sufficiently modern to be nowadays intelligible—have been very
great. I could have rendered his words much more easily in
the English of his own period—interlarded as it was with
Capitals and wtalics and irregular and curious spellings and
the queerest punctuation. But this, while superficially pre-
senting an old-world appearance, would have been nowise
satesfactory to You, dear modern Reader. Rather would it
have recalled the false ancientry of William Morris, whose
“Old English” was often no better than anachronism: for I
emagine that many of Morris’s “ translations” —such as his
version of Beowulf—are written in a language which no other
Englishman ever employed. They remind me unpleasantly of
“Ye Olde Englishe Petrole Pumpe,” from which (I am told)
motorists can now fill their tanks within 20 miles of London
Town.

All my translations of Leeuwenhoek (as you will soon ob-
serve) are compromises between ancient and modern. I adopt
old words and old phrases (used by his own English contempor-
aries) whenever they are understandable at the present day, but
I eschew—on principle—all unfamiliar expressions. I want
you, dear English Reader, to read Leeuwenhoek in his own

8 LEEUWENHOEK AND HIS “LITTLE ANIMALS”

words—as nearly as possible—but above all I want you to
understand him; and I do not forget the warning issued to the
translators of the Targums (the Aramaic versions of the old
Hebrew testament): “He who translates quite literally is a
liar, while he who adds anything is a blasphemer.” The Rev.
Dr Pusey hit the nail on the head, I think, when he said (in-
troducing his English rendering of St Augustine) that a
translation of an author should be “a re-production’ in another
language, ‘with as little sacrifice as may be of what is peculiar
to him”: adding feelingly that “it is very difficult to avoid
introducing some slight shade of meaning, which may not be
contained in the original.” This, and more than this, I dis-
covered for myself many years ago. Long ago I realized the
truth of the Italian saying “ traduttore traditore ”—a trans-
lator is no better than a traitor. Instinctively I dislike and
distrust translations, and it is only by the trony of fate that I
now appear before you in the garb of a translator myself. I
would also add, in the words of another interpreter of St
Augustine (the Rev. Marcus Dods): “That the present trans-
lation also might be improved, we know; that many men were
fitter for the task, on the score of scholarship, we are very
sensible ; but that anyone would have executed it with intenser
affection and veneration for the author, we are not prepared to
admit.”

In making my translations for you I have always tried—
with what success you must judge—to preserve the flavour of
Leeuwenhoek’s own writings, yet at the same time to satisfy
the requirements of the most up-to-date protistologist : and
when I have had to translate the words of other authors, or of
old documents, I have always tried to preserve their individual
peculiarities in a like manner. My ideal has not (I know) been
attained, but it is probably unattainable : nevertheless, you will
(I hope) perhaps allow me some small credit for possessing, in
these uninspired times, even an ideal, towards which I have
ever striven. No similar attempt has ever been made by
another—despite its crying need. No protozoologist or bactert-
ologist has ever before so much as read, or even pretended to
read, all Leeuwenhoek’s extant writings on these subjects ; and
those authors who have previously offered to interpret his dis-
coveries have usually gone ludicrously astray themselves (whereof
I shall give you many instances). Almost everything that has
yet been written about Leeuwenhoek’s work on protozoa and

THE AUTHOR’S EPISTLE TO THE READER 9

bacteria is glaringly inaccurate. His fame has consequently
suffered, though the reputations of his translators and traducers
are bound to suffer far more in the end. If I succeed only in
showing you his own immeasurable superiority over all his
commentators (including, of course, myself), my work will not
have been wholly wasted.

And now, dear Reader, after prejudicing my case with these
disparaging remarks, Imust cast myself wpon your mercy. I
am forced to confess that, had I fully understood the difficulties
of my present undertaking at the outset, I would never have
embarked upon it: for it is a work suited to a linguist, his-
torian, antiquary, and man of leisure, and unhappily I possess
none of these necessary qualifications. The only qualification
which I can justly claim is that I have spent all my time and
energies, all my life, in studying the micro-organisms which
Leeuwenhoek discovered ; and consequently I imagine that I
know the subject-matter of his writings on protozoa and bacteria
as no mere scholar or philologist can ever hope to know it. I
freely admit that my knowledge of Dutch, Latin, Greek, French,
German, Italian, and even English, is unscholarly and defective :
but I venture to assert that nobody, however skilled he may be
in these tongues, can ever comprehend Leeuwenhoek’s writings
on protozoology and bacteriology unless he be himself a working
protozoologist and bacteriologist. And this I conceive to be the
primary and indispensable qualification for anybody who would
rightly interpret his discoveries in these disciplines. But no
man can do everything : and a modern protozoologist has little
time for studying the classics or for learning languages. He
has not even time to read all the current literature on his own
subject. I can but plead, therefore, that my knowledge of
Dutch and Latin and English would (I hope) have been greater
uf Thad not applied all my chief energies, all day and every
day, to the practical study of protozoa and bacteria. The study
of Leeuwenhoek ?s really an occupation—to use his own words—
“for a whole man, which my circumstances did not allow of :
and I have devoted only my spare time to rt”.

Yet very seldom, dear Reader, in the course of my working
life have I had anything that you could fairly call “ spare time”.
For many years I have had to work for seven days in every week
and for fifty weeks in every year at my own researches : conse-
quently, I have had little opportunity to edit Leeuwenhoek’s—
or even to read his voluminous writings. Most of the lines

10 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ’”’

which I now offer for your indulgent perusal have been written
at odd moments in the course of other studies of my own.
Weeks, months, and even years, have often elapsed between sen-
tences and paragraphs which now run consecutively in the
following pages—long periods filled with most concentrated
work on subjects but distantly related. I beg you, therefore, to
bear this ever an mind, but especially when you detect inconsts-
tencies (whereof there are, I fear, many) in the several sections
of this book. it has been some 20 years a-writing, and I am
not now the same person that I was 20 years ago.

If you are disposed (which is like enough) to find fault with
my poor scholarship, Iintreat you to consider kindly what I
have already published of my own researches (which ws but a
small fraction of what I have done), and to remember that the
present publication of Leeuwenhoek’s work has been an addi-
tional charge upon these my own most exacting labours. The
whole of this book has been written at irregular intervals and
under very great difficulties—mostly at the dead of night
(between midnight and 8 a.m.) after a hard day’s work at my
own researches, and with another similar day in the laboratory
before me. IPf you find that I have done my task badly, please
remember that it has been almost impossible for me to do vt at
all. Icannot even tell you now how I have achieved it: but
to show you the shifts to which I have been put wm order to
carry out this undertaking, however wll, I may tell you that one
of the following translations (and that, I think, not the worst)
was made during several long and interrupted nights im the
Great War, when German airplanes were trying to drop their
bombs on London. Any one of these random missiles might
well have fallen upon Burlington House and utterly destroyed
all Weeuwenhoek’s priceless original letters (not to mention
myself). . . . But he said himself prophetically that he
“never trusted people, especially Germans”; though he also
said more generously elsewhere, in another connexion, “ yet
theyre to be forgiven, for they know no better”’.

I know that I cannot paint you a true picture of Leeuwen-
hoek’s protozoology and bacteriology without framing it with
some authentic account of himself. This also I have therefore
attempted. But almost every veridical record of his life ts
buried in obscurity: almost every biographer of this great dis-
coverer seems to have taken delight in burying his own findings
in almost inaccessible places, where others could discover them

THE AUTHOR’S EPISTLE TO THE READER i a

only by chance or inspiration. Consequently, much still
remains to be unearthed. I have only scraped the surface here
and there—through lack of opportunity to delve more deeply—
and must reluctantly leave the rest of the work to others. You
will therefore please remember, dear Reader, that my present
“life” of our great Delvenaar makes no pretence to be more
than a preliminary collection of materials for the use of some
more competent future historian.

About Leeuwenhoek himself the greatest ignorance still
prevails—not only in England but even in his native country.
Only one full-length biography (by Haaxman) has yet been
printed ; though Bovrtet, van Haastert, Halbertsma, Harting,
and more recently Bouricius, Schierbeek, and others, have
published many valuable data. ‘T'o Haaxman’s booklet all
students will forever be deeply indebted: but none can swppose
that the Rotterdam apothecary, writing more than half a
century ago, was in a position to say the last word about
Leeuwenhoek, or to appraise his scientific achievements at their
true worth. Outside of Holland little has been written about
him which is not almost comically inaccurate. The biographi-
cal dictionaries are stuffed with ridiculous statements, and
most historians of biology have hitherto been content to misprint
their mistakes.

Leeuwenhoek himself is, indeed, now almost unknown—
notwithstanding his celebrity. If yow doubt wt, dear Reader,
go to his native town of Delft, and make inquiries for yourself.
Ask any man wm the street about him, and he will probably
direct you to a modern road which now bears his name—a
road outside the old town in which he lived, and leading to
the railway station. Or your informant will possibly send you
to a spot where a bronze effigy of our hero now hangs on the
railings surrounding the playground of a girls school. “Here”’,
you may read, ‘‘ Leeuwenhoek, the discoverer of the Infusoria,
lived and worked in the year 1675 "—the year (presumably) of
the discovery. Yet he never lived in that street, nor was the
discovery made wn that year. The whole memorial is mistaken
and misplaced. If you still doubt my words (when I say that
Leeuwenhoek zs comparatively unknown, even to his own
countrymen), let me tell you a story for whose truth I can
vouch. A few years ago, a party of Dutch physicians visited
the Institute where I work. One of them, on hearing from
a colleague that I had been studying Leeuwenhoek’s letters,

He. LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

expressed a desire to meet me: and on being introduced he
said “I am glad to make your acquaintance, as I also am
interested in Leeuwenhoek; I understand that you knew hum
personally ?”’.

To appreciate Leeuwenhoek properly, it is (I submit) need-
ful to know not only the particular history of many sciences but
also the general history of his own times: and to see him in
his true perspective it is even necessary to understand the
relations of Holland and England in his day, and the peculiar
circumstances which led to the founding of the Royal Society
and to his connexion with that learned assembly. I confess
I do not fully comprehend any of these things myself, so I can
here do no more than indicate a few sources of my own imperfect
information.

Most men of my acquaintance seem to know little more of
the history of Holland than is contained in those ever-popular
English classics written by John Motley (an American), whose
great stories end where Leeuwenhoek’s life begins. Yet
Leeuwenhoek’s period is well documented on the English side :
for it is covered by such deservedly famous and widely read
records as the Diaries of gay Samuel Pepys and gentle John
Evelyn ; John Ray’s unadventurous but instructive Travels ;
dear Dorothy Osborne’s entrancing Letters to her future
husband William Temple; the entertaining Epistles of the
Welsh scholar James Howell; Gilbert Burnet’s solid History
of his own Times ; and the indiscreet Scottish-French Memoirs
of Count Grammont written by Anthony Hamilton. (I may
perhaps remind you that Pepys, Evelyn, Ray, and Howell all
travelled in Holland: that Sir William Temple was once our
Ambassador at The Hague: and that Bishop Burnet not only
lived in Holland but even married a Dutchwoman—of noble
Scottish descent. Pepys, Evelyn, Ray, and Burnet were, as of
course you know, once distinguished Fellows of the Royal
Society.) What little I have been able to learn of life in
England and Holland in Leeuwenhoek’s day has been derived
from these and other contemporary writers, rather than from
professional modern historians. Nevertheless, I have not
neglected to study (I hope with profit) the excellent works of
Motley and Edmundson and Bense and others, and the well-
known Histories and Record of the Royal Society compiled
by Sprat, Birch, Thomson, Weld, and the rest. I have even
learned something from the scribblings of men like Ned Ward,

THE AUTHOR'S EPISTLE TO THE READER 13

the London publican and sinner, who left us the common mans
view of the Royal Society and its Fellows at the time when
Leeuwenhoek was in his prime. I regret that space will not
allow me to quote at length Ned’s description of a typical
Fellow of his period, who “could see as far into a millstone
as another :” or of the Society’s musewm at “ Wiseacres’ Hall”
[Gresham College|\—a “warehouse of Egyptian mummies,
old musty skeletons, and other antiquated trumpery :
skeletons of men, women and monkeys, birds, beasts, and
fishes; abortives put up in pickle, and abundance of other
memorandums of mortality.”

Tempora mutantur, nos et mutamur in illis—the times are
changed, and with them we ourselves. ’tis a hackneyed phrase,
dear Reader, and as you know a misquotation, but none the less
true. Today an Englishman must almost apologize for reintro-
ducing an ancient Hollander to his own countrymen, and for
presuming to revive und interpret his long-forgotten words.
Yet England and Holland were once more closely goined—both
geographically and spiritually. Only 250 years ago the links
of language and spiritual endeavour needed no emphasis: vt
would then even have been unnecessary to explain the manifest
connextons between certain bits of Holland (such as Delft and
Leeuwenhoek) and allied bits of England (such as London
and its Royal Society). Today, alas! we are apt to forget
our common heritage of race, language, religion, and even
science. . . . The times are changed indeed.

You will doubtless exclaim that I exaggerate the affinities
between the Dutch and English nations: and you will (with
some show of justice) oppose my statements with familiar argu-
ments from certain memorable wars—both old and new. But
please do not forget that those old contests for naval and
colonial supremacy were fought in the days before we had
learned to express our rwalry in the form of tennis and
football: and if you should perchance remind me of South
Africa, pray remember also that Christianity was originally
implanted in Holland herself chiefly by monks from Britain,
and that the struggle for religious freedom—and its ultimate
success—ran sympathetically parallel in both countries. Hven
when England and Holland were at war, Englishmen and
Scotsmen (as you know) once fought on both sides against the
common enemy : it was once no inconsistency, during an Anglo-
Dutch war, for British troops to fight simultaneously side-by-

14 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS”’

side with Hollanders against Spain or France or Germany.
You will remember too, I hope, that an English nobleman
(Dudley, Earl of Leicester) was once Governor-General of
Holland—after his mistress, our good Queen Hlizabeth, had
been offered (and had refused) the sovereignty of the States.
Had Cromwell’s dream—a little later—come true, Englishmen,
Scotsmen, Irishmen, Welshmen, Hollanders, Zealanders, and
Frieslanders, might even now be living together in the first
“United States”. Just think of that! And of more personal
and private relations, let me recall the beautiful friendship of
Erasmus and Thomas More—a Dutchman and an Englishman
who were true brothers. Let me remind you also that the first
President of the Royal Society (Sir Robert Moray) was formerly
a soldier in the Netherlands, where he had many friends, and
could speak the language; that a very celebrated Hollander
(Christiaan Huygens) was among the first Fellows; and that
the Royal “ Patron and Founder” of our Society was himself
an exile in Leeuwenhoek's land during his lifetime.

But you will ask (very properly) what all this has got to do
with Leeuwenhoek himself and with this book? I will tell you.
In reintroducing plain Mr van Leeuwenhoek, the Dutch draper
and amateur micrographer, I want also to vmpress upon you
that there are still blood-brothers in every different nation.
Barriers erected by birth and prejudice and education are
blown sky-high before the fire of common human aims and
interests. Language and land and lineage are no bars to
mutual and native understanding. An honest man in any
country is linked to all other honest men in all other countries.
-_ When a true man like Antony van Leeuwenhoek ?¢s born, the
heavens are opened. Even when he dies he is not dead: his
spirit glows with the divine light forever, and will forever be
seen and understood—somewhere, sometime, by somebody. No
Princes, Popes, politicians, or even prophets, can unite man-
kind in universal brotherhood; but the disinterested and simple
men everywhere can (and perhaps eventually will) unknowingly
draw warring nations together, and may ultimately save
humanity from the fate of the Triassic reptiles. As surely as
Leeuwenhoek, the old Dutch draper, has—after centuries of
misunderstanding—established connexion with me, a modern
English biologist, and has awakened my sympathy with himself
and his countrymen; just as surely will other men of other
nations and other interests be drawn together by the endearment

THE AUTHOR'S EPISTLE TO THE READER 0S)

engendered by common enterprise and common human endeavour.
This is the real League of Nations—the only one that can ever
succeed or survive.

Therefore, dear Reader, meet Mr van Leeuwenhoek (a
simple and ordinary dead Dutchman) and shake him by the
hand and hearken to what he has to say. When you have
done that, you will not only know the true meaning of that
misused term “ scientific research”, but you will also realize
(I hope) that you have already gone further along the path of
peace and progress than some of the more sophisticated people
now sitting solemnly at Geneva or at the meetings of the most
learned and modern and Royal and scientific societies (God
bless and prosper them all!).

For my own part, I will only add—though it must now
be obvious—that the making of this book has been to me a
labour of love: and as such it is offered with all its manifest
imperfections to You, good Reader, and to all other lovers of
Leeuwenhoek and of his “little animals” and of all else
that such love implies.

Farewell.

16

MEMORABILIA

Philips v. Leeuwenhoek married Margriete Bel v.d. Berch

Their son Antony van Leeuwenhoek born at Delft
baptized
Father buried
Mother remarried
Apprenticed to draper in Amsterdam
Draper and haberdasher in Delft .
Married Barbara de Meij
Maria his daughter born
Appointed Sheriffs’ Chamberlain of Delft
Mother buried :
First wife (Barbara) died
Appointed Surveyor
Married Cornelia Swalmius . :
Addressed first letter to Royal see of London
Discovered the Protozoa
and the Bacteria
Executor of Vermeer’s estate
Wine-gauger of Delft
Fellow of the Royal Society

Second wife (Cornelia) buried
Correspondant de l Académie des Sciences, Paris
Died at Delft
and buried in the Ola Chasen
Tomb erected
Maria died

Microscopes sold .

30 Jan. 1622
24 Oct. 1632
4 Nov. 1632
8 Jan. 1638

18 Dec. 1540
1648

circa 1654

29 July 1654

. 22 Sept. 1656

26 Mar. 1660
3 Sept. 1664
11 July 1666
4 Feb. 1669
25 Jan. 1671 ©
Apr. 1673
1674

1676

. 380 Sept. 1676

15 Aug. 1679

29 Jan. 1679/80 O.S.
= 8 Feb. 1680 N.S. ]

6 Jan. 1694
4 Mar. 1699
26 Aug. 1723
31 Aug. 1723
: 1739
25 Apr. 1745
29 May 1747

PART I

LEEUWENHOEK

A very civil complesant man, & douptless
of great natural Abileties; but contrary
to my Expectations quite a stranger to
letters, .. . which is a great hindrance
to him in his reasonings uppon his Obser-
vations, for being ignorant of all other
Mens thoughts, he is wholy trusting to
his own.—Dr Thomas Molyneux (1685).

18

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19

THE LIFE OF
ANTONY VAN LEEUWENHOEK

NTONY VAN LEEUWENHOEK,’ the hero of the

A following pages, was born at Delft in Holland on

24 October 1632. He died in his native town on

26 August 1723; being then aged—as his epitaph informs

us, with appropriate numerical particularity—‘ 90 years,
10 months, and 2 days.”

The year of Leeuwenhoek’s birth is memorable, to
Englishmen and Hollanders alike, as that in which several of
our other great men—of widely different genius—were also
born: our philosophers John Locke (1632—1704) and Baruch
de Spinoza (1632—1677); the architect Christopher Wren
(1632—1723); and the famous painters Jan Vermeer of Delft
(1632—1675) and Nicolaes Maes (1632—1693). It is also
remembered by historians as the year of the Siege of
Maestricht, which marks approximately the middle of the
Thirty Years’ War. The unhappy Charles I was then King
of England; the great Prince of Orange Frederik Hendrik,
whose period is called a “golden age”’ by Dutch writers, was
Stadholder of the United Netherlands: and for both Holland
and HKngland the times were big with coming developments in
politics, religion, and commerce—no less than in science,
philosophy, and art. Verily astrange hour for the birth of one
who, while leading in the midst of wars the peaceful life of a
provincial tradesman, was to win immortal fame by his amateur
activities as a man of science.

Of Leeuwenhoek’s parents not much is certainly known.
His father was named Philips Antonysz. van Leeuwenhoek’,

* For orthography, derivation, and pronunciation of the name, see
p. 300.

* 7.e., Phillip, son of Antony v. L. The name is sometimes given as

Philips (or Philippus) Antony, but this is a mistake. Of. Boitet (1729),
Haaxman (1875), and Soutendam (1875). In an old genealogical tree—
which I have seen—in the possession of the Haaxman family, the name is
written as given above: but in the archives of Delft he is styled simply
“Philips Thonisz.” (Bouricius, 1924, 1925.)

20 LEEUWENHOEK AND HIS “LITTLE ANIMALS”

and was a basket-maker living in the East-End (Oosteinde) of
Delft—near the now long-vanished TLeeuwenpoort’. He
appears to have been a craftsman of good Dutch stock, but of
no personal or social distinction. His own father (Antony
Philipszn.) was likewise a basket-maker *.

Leeuwenhoek’s mother was Margaretha, daughter of Jacob
Sebastiaanszoon Bel van den Berch’, a Delft brewer*. She
belonged to a good family, and was related to other Dutch
families of equally good standing’. The brewers then, as now,
were no inconsiderable folk in Holland; and it thus seems
clear that any claims which our Antony may have to gentle
birth must rest upon his mother’.

Philips van Leeuwenhoek and Margaretha Bel van den
Berch were married in 1622. Their betrothal (ondertroww)
was formally announced on January 15, and the marriage took
place on the 30th of the same month—as Bouricius has now

‘ Cf. p. 338 sq., infra. The house in which he is believed to have
lived, and in which L. was born, is shown in Plate II.

® fide Bouricius. The Leeuwenhoeks, for several generations at least,
were consistently named Phillip and Antony alternately. (Cf. the family
tree, p. 18.) This system of alternate nomenclature seems to have been
common in Dutch families at that period. (L. himself made three unsuccess-
ful a to rear a son called Phillip—as will be evident in the family
tree.

* alias Berg, or Bergh. The name is spelled variously. Margaretha’s
forename is also given as Margriete (cf. Schierbeek, 1930) and Grietge (cf.
Plate III).

* Cf. Boitet (1729), Soutendam (1875), Haaxman (1875), and Bouricius
(1924, 1925). lL. himself tells us (Send-brief XXII, 16 May 1716) that his
grandfather and great-grandfather were brewers, and that his grandmother
was the daughter of a brewer. But his grandfather on the father’s side
(another Antony) was, as just noted, only a basket-maker.

* Namely, the families of Hoogenhouk, Bleiswijk, Swalmius, and
Mathenesse. Cf. Boitet (1729), Halbertsma (1843), and Haaxman (1875).

® Boitet (1729), only six years after L.’s death, records that he came
from ‘‘zeer deftige en eerlyke ouders’’; but this was perhaps merely a
euphemistic way of saying that he was born of respectable parents. It can
hardly be taken to prove that he belonged to the aristocracy. Although it
would be unusual to call a basket-maker “ zeer deftig”’ at the present day,
such hyperbolic expressions were as customary in Holland as they were in
England at the date when Boitet’s book was published. It must be
remembered, also, that his book was not issued with the object of belittling
Delft and her burghers.

PILATE,

THE HOUSE IN WHICH LEEUWENHOEK WAS BORN (1632)

in the East-End (Oosteinde) of Delft: as it appeared in November, 1926.
[Identified by Mr L. G. N. Bouricius. Now demolished. |

facing p. 20

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facing p. 21

BIRTH AND PARENTAGE P|

ascertained definitively. Antony, their first son and fifth
child, was born to them ten years later. He was born on
24 October, and was baptized in the New Church at Delft on
4 November’, a.D. 1632. (See Plate IIT.)

It is recorded that Antony had four® surviving sisters—
Margriete, Geertruyt, Neeltge, and Catharina—though very
little is now known about any of them. We know,‘ however,
that Margriete [Margaret] the eldest (born 1623), married one
Jan Molijn,’ and herself bore five children; and one of these,
named Maria (like Leeuwenhoek’s own daughter), married
a certain Cornelis Haaxman from whom Leeuwenhoek’s
biographer, P. J. Haaxman, claimed descent. Geertruyt
[Gertrude] was born in 1626, and Catharina in 1637°, and

1 See Bouricius (1924, 1925). The date ‘5/30 Jan.” given by Schier-
beek (1980) is incorrect, and should read “ 15/30.”—It has recently been
alleged by Naber that L.’s father had previously tried to marry one of the
daughters of the adventurer Cornelis Drebbel (1572—1633), who is
regarded by some admirers as the inventor of the microscope. Naber even
avers (p.32) that L.'s father was ‘‘one of Drebbel’s lens-grinders”; and
would insinuate apparently that what L. himself knew about lenses was
learned from his father, who in turn derived it from Drebbel. But this
story is apocryphal. We now know that L.’s father was not a lens-grinder
but a basket-maker, and that he died when Antony was only 5 years old:
and we now know also—thanks largely to Jaeger (1922)—a good deal about
Drebbel. Dr Schierbeek, who first drew my attention to Dr Naber’s
statements, wrote to ask for his evidence: and as a result of this correspon-
dence (which Dr Schierbeek kindly allowed me to read) and of my own
inquiries, I can only conclude that no evidence exists. Cf. Jaeger (1922,
especially p. 7) and Bouricius (1924).

* Schierbeek (1923), Bouricius (1924, 1925). Schierbeek (1930), through
a misprint, wrongly gives the date of baptism as Nov. 14.

* Haaxman (1875), Schierbeek (1930). Two other children—a sister
(Maria) and a brother (Jacob)—died in infancy. Haaxman mentions only
3 sisters, but Bouricius has since discovered the existence of the fourth
(Neeltge), who apparently attained maturity. The names of Margriete and
Geertruyt are spelled ‘ Margaretha” and “‘Geertruida”’ by Haaxman.

* Haaxman (1875), Bouricius (1924).

* This Jan Molijn (alias du Molyn), who married L.’s sister Margaret
on 10 May 1643, was himself the son—by an earlier marriage—of the
Jacob Molijn whom L.’s mother (also named Margaret) married after the
death of her first husband (L.’s father): fide Bouricius, in litt.

° According to Bouricius (1924) and Schierbeek (1930).—Catharina, who
was married to Claes Jansz. van Leeuwen in 1655, is referred to by L.
himself in unpublished postscripts to Letter 13a (22 Jan. 1676) and
Letter 39 (17 Sept. 1683), in both of which he requests that the Phil. Trans.

22, LEEUWENHOEK AND HIs ‘‘ LITTLE ANIMALS’”’

both married subsequently. Neeltge | Nellie] apparently died
young. (See the Family Tree, p. 18.)

All the trustworthy evidence now available thus shows
that Antony was a true Hollander of decent though not of
aristocratic descent—a child of fairly well-to-do tradespeople.
Richardson’s statement (1885)—unhesitatingly accepted by
Locy (1901, 1910), Plimmer (1913), and others—that he was
of ‘ Jewish Saxon ” extraction, is nothing but a wild specu-
lation’: and the evidence against the guess that Leeuwenhoek
was a Jew, or of Jewish origin, is overwhelming. Mr Bouricius
assures me’ that “‘there were practically no Jews in Delft”
at that date: and if there were any, they certainly did not
then engage in basket-making or in brewing, nor did they hold
any municipal appointments (from which they were debarred).
Moreover, the baptisms and marriages and burials of all
members of the families concerned (whose names are obviously
not Jewish) were entered in the registers of the Reformed
Church; while Leeuwenhoek was, of course, himself baptized
in the New Church and buried in the Old Church at Delft.
Mr Bouricius, who speaks with authority, says: “In geen
geval was van Leewwenhoek een jood’’—Leeuwenhoek was no
Jew anyway.

When our Antony was only five years old, his father Philips
died,’ leaving his mother in sole charge of their little family.
But soon afterwards (18 December 1640) she married again—
her second husband, Antony’s stepfather, being a painter
named Jacob Jansz. Molijn, who died in 1648. Antony’s
mother herself died 16 years later, and was buried in the Old
Church at Delft on 3 September 1664.’

may be forwarded to him through “ Mistress Catharine Leeuwenhoek,
widow . . . living in the High Street at Rotterdam.’ She had no
children (fide Bouricius). :

' Richardson’s ridiculous statement had no other foundation than his
own imagination. The “Jewish” and “ Saxon’”’ ancestors were divined by
inspection of L.’s portrait !

* in litteris.

* He was buried in the Old Church at Delft on 8 January 1638
(Bouricius, 1924). The exact date of his death I have been unable to
ascertain. Of. Schierbeek (1930).

“ The foregoing facts—imperfectly noted by earlier biographers—are
recorded in part by Bouricius (1924, 1925), and additional confirmatory
details have been kindly sent me by him in personal communications. Cf.
also Schierbeek (1929, 1930).

SCHOOLING 23

Somewhere about the time of her second marriage, Antony’s
mother put him to school at Warmond, a townlet a few miles
north of Leyden. After receiving his earliest education here,
he went—at what age is not exactly known—to live with an
uncle who was an attorney, and also town clerk, at Benthuizen.’
It has been said that young Antony was at this time con-
templating a similar career, and that he went to his uncle to
prepare himself for it.” But there appears to be very little
foundation for such a supposition ; and it has been judiciously
remarked * that, as he was never even taught Latin, it is un-
likely he was ever destined either for the law or for the
university.

But whatever his own or his family’s intentions may have
been at this date, we know certainly that Antony neither
progressed far in the study of the law nor did he prepare himself
for a university career. We may suppose, however, that his
education was not wholly neglected during his residence with
his uncle: and it was, perhaps, at this time that he acquired
those rudiments of mathematics and physical science in which
he so delighted to indulge himself in his later life. Yet it is
certain that he received no instruction in languages, for to the
end of his days he knew none but his own.*

In 1648° (the year in which his stepfather died) Antony,
being 16 years of age, was sent to Amsterdam—then, as now,
one of the great commercial cities of the world. He was there
placed in a linen-draper’s shop, in order to learn the business ;
and in a very short time he qualified himself as a draper and
rose to the position of book-keeper and cashier’—a post which
he held for several years at least. How long he remained in
the shop at Amsterdam is not known, and nothing is known
with certainty regarding his other doings at this period. But
it seems probable that during his sojourn in the capital he

’ Cf. Boitet (1729) and Haaxman (1875).—Benthuizen is a small place
some 9 miles N.H. of Delft.

* Boitet (1729), followed by v. Haastert (1823).

* Halbertsma (1843).

* Of. p. 305 infra.

° Schierbeek (1929) gives the year as 1638: but this is obviously a
misprint.

° According to Boitet (1729), who is copied by later biographers. There
are no known records extant relating to L.’s apprenticeship.

24 LEEUWENHOEK AND HIS “LITTLE ANIMALS”

made the acquaintance of Swammerdam,’ and perhaps of other
young men with congenial interests.

I may remind the reader that in 1648—the year in which
Antony went to serve in the shop at Amsterdam—the Treaty
of Minster, which ended the Thirty Years’ War, was signed.
This reminder will recall the posture of Kurope at the moment
—a moment when “ Holland had taken her place in the very
front rank in the civilised world, as the home of letters, science
and art, and was undoubtedly the most learned state in
Kurope.” °

About six years after his first apprenticeship in Amsterdam,
Leeuwenhoek returned to his native town: and here, for the
rest of his days, he remained. For nearly 70 years—from
1654 until the day of his death in 1723—he lived and worked
in Delft; so that when, in the fullness of time, he became
famous, he also became enduringly identified with his
habitation. During his later lifetime he was regarded as one o
the sights of the place—hardly less conspicuous than the Old
Church, and almost as permanent a fixture.

As Delft forms the background of all the scenes displayed
in this book, I must here say a little more about this fine old
town. ‘There are several descriptions and many pictures of
the place as it was in Leeuwenhoek’s day. We have, for
example, not only the compendious and valuable Dutch
accounts by Dirk van Bleyswijck (1667) and Reinier Boitet
(1729)—enriched with numerous engravings—but also various
shorter and less particular records contained in works such as
the earlier Latin “ Batavia” of Junius (1588) and “ Batavia
Illustrata”’ of Scriverius (1609), and in the anonymous but
once popular French guide-book called “Les Délices de la

* That L. was acquainted with Swammerdam we know from his own
statements (e.g., he refers to visits which Swammerdam paid him in Letter 6,
7 Sept. 1674). Haaxman has gone so far as to suggest (1875, p. 10 seq.)
that it was Swammerdam who, during L.’s residence in Amsterdam, first
aroused his interest in microscopic studies. But this appears improbable:
for, as Pijzel (1875, p. 108) points out, Swammerdam was only 11 years old
when L. went there, and not more than 16 or 17 when he left: and we can
hardly suppose, therefore, that L. received much guidance from so youthful
and junior a mentor.

* Edmundson (1922), p. 186. This is an indisputable fact which many
people nowadays—in many different countries—are all too apt to forget.

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PLATE IV

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facing p. 25

.
.

OUDE DELFT

On the left, the

the distance, the tower of the Old Church.

the main thoroughfare of the town, looking northwards.

in

East-India Company’s house
From an old engraving.

DELPHI BATAVORUM 25

Hollande.”* All old histories of Holland and of the House
of Orange” also contain repeated references to Delft—the
family’s stronghold in the Netherlands. Here William the
Silent was assassinated (you can still see the hole made by the
murderer’s bullet in the wall of the staircase of the Prince’s
Court): and here, in the New Church, is the mausoleum
wherein many of the most distinguished sons and daughters
of the House lie buried. Delft, in the time of Leeuwenhoek,
also forms the subject of one of the world’s pictorial master-
pieces.” But the best and shortest description of the town at
the time when Leeuwenhoek was in his prime—when Holland
and England were at settled peace under William III of
Orange and Great Britain—is, I think, that left to us by an
obscure Englishman, William Mountague, Hsq., who once
spent a holiday in Holland and afterwards wrote a lively
description of what he saw. From his little book (1696) I
may quote the following lines*:

Delftis a fair and populous City, very clean, well built,
and very pleasant; well seated in a Plain of Meadows,
which may be laid all round under Water, if they open
their Sluces, when the Wind is Kast-North-EHast. At
the Entrance of it stands a general Magazine of Warlike
Stores (but no Powder’) for the Publick Service. This
City was burnt to Ashes Anno 15386, but soon re-built, and
now in greater Glory than ever. The Hast-India Com-
pany of this Place have here a very good House and large
Ware-Houses; as also an eighth part of the Great or
General Stock, this being the Third Town of Holland,
having the Third Voice in the States, whither it sends
Deputies, as also to all the other Colleges. Here are very

' Pepys (Diary, 10 Dec. 1663) mentions that he bought a copy of this
work. I have read only the revised version of 1710.

* As examples I may mention the early Dutch histories of William
and Maurice (see Anonymus, 1662), and the Historia Nostri Temporis by
Brachelius (1666).

® See Plate VII, opp. p. 35. My small reproduction gives but a poor
idea of the splendour of the original painting.

“ Mountague (1696), p. 18 sq.
° Cf. footnote 3 on p. 55 infra.

26 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

fine Buildings, and amongst them the Town-House,' with
these two Verses on the Front.
Haec domus odit, amat, punit, conservat, honorat,
Nequitiam, Pacem, Crimina, Jura, Probos.

Here is a spacious Market-Place between this House
and the great Church,’ in which stands William‘ the
First Prince of Orange (Great Grand-Father to his Sacred
Majesty King William’) at full length, in Armor, in
Copper Effigie . . . ’Tis the most Magnificent Tomb
in all the Seventeen Provinces. Here that Prince kept
his Court, and here was that brave Prince assassinated in
the 5lst Year of his Age .. .

In the t’other Church’ is a Monument of Admiral
Trump’s' inrich’d with Miniature, and a fine Inscription

In the same Church is Myn Heer Pithin’s Tomb‘,
a very handsome one. . . . The Churches here, and in all
the Seven United-Provinces, are generally bigger than ours
in Hngland, but fewer in Number.

Here is a large and neat Market, or Flesh-Hall (as they
call it) for all sorts of Butchers Meat, which they have
very good . . . They have also a good Fish-Market
here, and another of Fruits, Roots, and Herbs.

The People in this City are rich, trade much to Sea, and
make much Porcelain, or fine Earthen Wares, to a great
Perfection, tho’ far short of China, which they pretend to
resemble, and brew good Beer here . . . yet it tastes

" The Stadhuis or Town Hall. See Pl. VI, opp. p. 32.

* “This House hates, loves, punishes, keeps, honours; Wickedness,

Peace, Crimes, Oaths, the Righteous.’ This inscription is no longer to be
seen—having been removed in the process of subsequent ‘‘ restoration.”

* The New Church.
* William I, the Silent (1533-1584); Stadholder.
* William III of England and Orange (1650-1702).

* The Old Church, where L. himself now also lies. See Pl. XIV, opp.
p. 100.

" Admiral Maarten Tromp (1598-1653).

* Admiral Piet Hein (1572-1629).—All the tombs and places mentioned
by Mountague can still be seen.

DELFT 27

insipid, and indeed is but weak, compar’d to the English,
having little or no relish of the Mault.’

Mountague forgot, however, to mention the trees and the
waterways which are still so typical of the town; so I
would complete his picture by adding a few touches from a
modern historian” who wrote of a time still earlier than
Leeuwenhoek’s :

It was a quiet, cheerful, yet somewhat drowsy little
city, that ancient burgh of Delft. The placid canals by
which it was intersected in every direction were all
planted with whispering umbrageous rows of limes and
poplars, and along these watery highways the traffic of
the place glided so noiselessly that the town seemed the
abode of silence and tranquillity. These streets were
clean and airy, the houses well built, the whole aspect
of the place thriving

And writing of the same period, the Earl of Leicester—
Queen EHlizabeth’s favourite, who was once, by a strange
freak of fortune, Governor-General of the Netherlands—even
describes Delft as “another London almost for beauty and
fairness.” *

But to return to our subject proper. On 29 July 1654*

’ Delft was always famous for her beer: but the author of Batavia
(1588) agreed with Mountague that it was inferior to the English—
“ Cerealis potus prima post Britannicum zythum laude,’ etc. (p. 260).
Dr Hadrianus Junius (alzas Adriaen de Jongh) doubtless knew what he was
talking about, for he was at one time resident family physician to the Earl
of Norfolk (ef. Bense, 1925, p. 198).

* Motley, Dutch Republic: last chapter ad init.

* Quoted by Motley, United Netherlands (1869), Vol. I, p. 352. The
words are from a letter written by Robert Dudley, Earl of Leicester (1532 ?-
1588), to Lord Walsingham on 26 Dec. 1585. He adds (fide Motley) “ the
other towns I have passed by are very goodly towns, but this is the fairest
of them all.”

“ Haaxman (1875, p.16) gives the date as 26 July 1654. Bouricius
(1924) says 29 June 1654: but in a letter he informs me that this is a
misprint, and that the date given above is correct. According to Mr
Bouricius the archives of Delft show that the marriage was formally
announced on 11 July 1654, and registered on the 29th of the same month.
Schierbeek (1930) correctly gives the date as “ 11/29 Juli 1654’"’"—July 11
being the date of the ondertroww (corresponding roughly with “calling the

28 LEEUWENHOEK AND HIs “LITTLE ANIMALS ”’

when he was not quite 22 years old, Leeuwenhoek married
Barbara, the daughter of Elias de Mey’ and Maria Virlin?—
a@ young woman three years his senior.» The marriage took
place at the New Church in Delft. From this union five
children were born—three sons and two daughters—all but one
of whom died in early infancy.*’ The one who survived was
Maria, the second child, born on 22 September 1656. She
lived to a great age, but never married. She stayed with her
father Antony all his life, and ultimately buried him in the
Old Church of Delft—in a tomb wherein she was herself
interred in 1745, aged close upon 89 years’. Maria van
Leeuwenhoek was no “‘ scientist,’”’ but she was a good daughter :
we shall meet her again later. She kept house when her
father was at work, she kept himself when he was weak, and
she housed his body when he was dead. She will not be
forgotten while her father is remembered.

The year of Leeuwenhoek’s marriage (1654) was long
recollected in Delft: for this was the year of the terrible
explosion of the powder-magazine—a disaster which wrecked
the whole town, and killed untold hundreds of the inhabitants’.
The Queen of Bohemia’, writing to Sir Edward Nicholas* from
The Hague a week later (19 October 1654), says :°

banns” in an English church), and July 29 that of the actual marriage
ceremony (huwelijk).

* It may be of interest to English readers to note that Elias was at one
time a cloth-merchant in Norwich (fide Bouricius).

* Maria’s surname is given as “ Viruly”” by Haaxman, but Mr Bouricius
assures me that this is incorrect. She came from Utrecht—not Delft.

* Barbara de Mey was born 20 Dec. 1629 (fide Haaxman and Bouricius ;
and cf. Schierbeek, 1930).

“The three sons—all named Philips—were born in 1655, 1663, and
1664. The daughter who died (1658) shortly after birth was named
Margriete. See the Family Tree, p. 18.

* Maria died on 25 April 1745. The dates of her birth and death, as
here given, are those graven on the tomb.

° Cf. Boitet (1729), p. 564 octies. The explosion involved some 80 or 90
thousand pounds of gunpowder and happened at 11.30 a.m. on Monday 12
Oct. 1654. The event is not mentioned—so far as I know—by L. Among
those who perished was Karel Fabritius, the famous painter—supposed by
some (on very slender evidence) to have been Vermeer’s master.

" Elizabeth Stuart (1596-1662), sister to Charles I of England.

* Edward Nicholas (1593-1669), Secretary of State to Charles I and
Charles II.

* Published in Bray’s edition (1827) of Evelyn’s Memoirs, Vol. V, p. 204.

FIRST MARRIAGE. BUSINESS 29

I was at Delft to see the wrack that was made by the
blowing up of the powder this day seuenight, it is a sad
sight, whole streets quite razed; not one stone vpon
another, ib is not yett knowen how manie persons are
lost, there is scarse anie house in the toune but the tyles
are off.

A happier event which occurred in the same year, however,
was the conclusion of peace—for a time—between Holland and
England.

At about this date Leeuwenhoek bought a house and shop
in Delft, and set up in business as a draper. For these
premises he paid altogether—including interest on the money,
which he had to borrow—5000 florins’. His house was
situated’ in a street still called the Hippolytusbuurt, running
parallel to the Oude Delft (the main canal and thoroughfare of
the town), and within sight of the Old Church and the New
Church’, and near to the Fish and Meat Markets and the
Town Hall—all which places are mentioned by Leeuwenhoek
and can still be seen by the inquiring traveller. But
Leeuwenhoek’s house itself is no longer there. According to
Bouricius, to whom the identification of the site is due, it
was the second one from the Nieuwstraat (which connects
Hippolytusbuurt with Oude Delft) and was called ‘‘ The Golden
Head” (Het Gouden Hoofd). A few further details regarding
it can be gathered from certain passages in the Letters.
Leeuwenhoek lived in this house for the rest of his life, and
there can be little doubt that it was here he made most of his
discoveries’.

By great good fortune, two of the bills which Leeuwenhoek
made out for his customers have recently been recovered.
They prove conclusively that he carried on business as a

" Cf. Schierbeek (1929a). The facts were ascertained by the late Mr
Bouricius.

* This was forgotten until quite recently, when it was rediscovered by
Morre (1919) and Bouricius (1924). Of. p. 338 infra.

* These Churches are still called “Old” and “ New,” as they were in
L.’s day. The “New” one, however, is not very new, as it was built
between 1391 and 1496; while the “ Old”’ Church was probably built about
1240. Cf. Boitet (1729) and Wildeman (1903).

* Cf. p. 338 infra.

30 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS ”’

draper and haberdasher, and are the earliest known examples
of his handwriting. The shorter of these bills is here
reproduced’ in Plate V: the longer and earlier shows similar
items (silk, cloth, buttons, tape, ribbon, braid, etc.) sold to
Johannis Heijnsbroeck in 1658. In view of its singular
interest I give a complete translation of the bill exhibited
in the Plate:

Praise be to God! the 19th day of December 1659. In Delft.
Mr. Pieter Heijnsbroeck debtor

To Antony Leeuwenhoeck for the following
— Shop-wares —

4t ells* red kersey - - - @ 26 stivers th’ell - - - | 5.| 10.{ 8.°
24 dozen buttons and button-loops - - - - - - - - pata i eel hese
1 ell white bombazine @ 9 stivers - - - - -- - - Ae a es
ogra cilicc= Case Stia ats cane eae too eee ou xia Gees
24th ditto | 2 ells wide filoselle [?] ribbon - - - - - - - - - - - =| (ta eos

Total, G2) L723:

The contents hereof paid unto me
this 15th day of June in the year 1660.
Antony Leeuwenhoeck

Leeuwenhoek’s wife Barbara died on 11 July 1666,* when
they had been married twelve years: and not long afterwards
—on 25 January 1671°—he contracted a second marriage with

*This little document has already been printed by Morre (1919), who
discovered it among the estate-papers relating to the Delft “court of
chancery ” (Boedelpapieren der Delftsch Weeskamer, dossier No. 105). It
has also been referred to by Mr Bouricius, to whose widow and Dr A.
Schierbeek I am indebted for the photograph from which my plate has been
made.

*The Dutch ell at this period was approximately a modern metre, and
therefore less than an English ell (45 inches).

*The columns stand respectively for florins (guilders), stwivers (stivers),
and pennings. 16 pennings—1 stuiver; and 20 stuivers = 1 florin (about
1/8 in modern English money).

* fide Haaxman. She was buried on July 14 in the Old Church
(Schierbeek, 1930).

° fide Bouricius.

PLATE V

= a ae , O° ~. ” N¢, ™ s° Py (5 Qn dae
ea 2 Cay a’ -
: ! rely Pe ated, Ve

utio | Me SHE noe ow Fi lL eg5)

VA — ad (we << fos PO Bes ath een

)
“ ean |

FACSIMILE (REDUCED) OF A BILL MADE OUT BY LEEUWENHOEK FOR ONE
OF HIS CUSTOMERS, AND RECEIPTED BY HIMSELF. It reads as follows:

Laus Deo adij 19°". Xmb. a°: 1659. In Delff
8S". Pieter Heijnsbroeck Debitt
Aen Antonj Leeuwenhoeck over volgende

—Winckelwaren—
47 el Root carsaij - - &4.26.st.d’el F5:10:8
2% dosijn Knoopen en Knooplussen - F'-: 6: -
fel Wit Bombasiin: 4.9 st.- = =< - |) 4A ee soee
Aen Roo Si. - =. = See Wea ls fou (aires
247; ditto. 2. el breet Wijasel Lint - - - - = #-: 6:
Sa eG he cS

Den Inhout deses mij voldaen
Adij 15. Junij a°: 1660
Antonj Leeuwenhoeck

facing p. 80

SECOND MARRIAGE. CAMERBEWAARDER 31

a kinswoman of hers named Cornelia Swalmius.’ It is said
that she bore him another child, who died in infancy :? and.
Bouricius states that Cornelia herself died in 1694.°

It is probable that Leeuwenhoek carried on his drapery
business for many years—from the time of his first marriage
(1654) onwards. We have no direct information about him
again, however, until six years later, when he was made
Chamberlain to the Sheriffs of Delft. He held this post for
39 years; and thereafter, till his death, continued to draw
the salary attaching to it. At the date of his nomination
Leeuwenhoek was only 27 years old: for according to an
entry in the town archives he was appointed—retrospectively,
as it appears—on 26 March 1660, in succession to one Jan
Strick (otherwise unknown). The full title of this office’ was
“Chamberlain of the Council-Chamber of the Worshipful
Sheriffs of Delft,’ and the terms of appointment were as
follows: °

‘alias Kornelia Zwalmius (sew van der Swalm). The name is spelled
variously. According to van Bakkenes (1873) and van der Baan (1874) she
was the daughter of Johannes Swalmius (1621-1661), a clergyman of Valken-
burg. The date of her birth is apparently unknown, but she must have
been much younger than L., as her father was only 11 years his senior.

* Boitet (1729), Haaxman (1871, 1875), and Bouricius (1924). It is said
by van Bakkenes (1873), however, that L.’s second marriage was childless.
In any case, no child of this marriage survived.

* Buried 6 Jan. 1694; fide Schierbeek (1930). That she was alive in 1677
can be inferred from a passage in a letter written in this year (Letter 22,
Nov. 1677. Phil. Trans. (1678), Vol. XII, No. 142, p. 1040): and that she
was dead in 1700 is directly attested by L. himself, who then refers to her
as ‘my late wife”’ (Letter 130, 27 June 1700).

“ Curiously enough, L.’s civil appointments are not mentioned in Boitet
(1729); and it is perhaps for this reason that Banga (1868, p. 610) refers
to him—incorrectly—as “a simple citizen of Delft, holding no office.”” L.’s
appointment as Chamberlain was first reported by van Haastert (1823), who
quotes no authority for his statement.

>“ Camerbewaarder der Camer van Heeren Schepenen van Delfi.” The

Schepens, or Sheriffs, were important civil dignitaries at this period. But
Schout and Schepen have no exact English equivalents, so I can translate
such words only approximately.

° This entry was extracted from the town records by Mr J. Soutendam,
sometime Town Clerk and Archivist (Archivaris en Secretaris) of Delft. It
has already been published in full by Haaxman (1871, p. 14 sq.; 1875, p. 20
sq.) and by Soutendam (1875), from whose printed Dutch transcriptions
I translate. The information on this subject which Richardson (1885),

32

LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS”’

Their Worships the Burgomasters and Magistrates of
the Town of Delft have appointed and do hereby charge
Antony Leewwenhoek to look after the Chamber wherein
the Chief Judge the Sheriffs and the Law Officers of this
Town do assemble: to open and to shut the foresaid
Chamber at both ordinary and extraordinary assemblies
of the foresaid Gentlemen in such wise as shall be required
and needful: ztem to show towards these Gentlemen all
respect honour and reverence and diligently to perform
and faithfully to execute all charges which may be laid
upon him and to keep to himself whatever he may over
hear in the Chamber: to clean the foresaid Chamber
properly and to keep it neat and tidy: to lay the fire at
such times as it may be required and at his own con-
venience and carefully to preserve for his own profit
what coals may remain unconsumed and see to it that
no mischance befall thereby nor from the hght of the
candles: and he shall furthermore do all that is required
of and that pertaineth to a good and trusty Chamberlain.
For the which service the foresaid Antony Leeuwenhoek
shall enjoy such wages benefits and emoluments as the
foresaid lamented Jan Strick his predecessor in office did
enjoy and shall enter into his duties upon the morning
of the 24th of January 1660 and his wages shall be paid
upon the same terms as those whereon the foresaid Jan
Strick’s were paid. Ordered by all the Burgomasters in
Council assembled this 26th day of March 1660 and
signed by

J. Camerling, Pensionary.

Locy (1901, 1910, 1925), and Plimmer (1913) give, and which is stated by
them to have been derived from the researches of Dr A. Wynter Blyth
[a writer on toxicology and food-analysis, and Medical Officer of Health for
St. Marylebone, London], is evidently nothing but a garbled version of
Haaxman. There is no evidence to support Locy’s statements (1910, p. 78;
1925, p. 207) that Wynter Blyth himself examined the town archives—
which seems to be merely a mistaken inference from Richardson’s loose
expressions.

facing p. 32

|

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wut

[ine os antiert |

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‘AE
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i

PLATE VI

THE TOWN HALL OF DELFT

The Sheriffs’

d from the Market Place.

vilewe

Eastern (front) aspect,

Chamber was in the second storey, on the north side (right in picture).

From an old engraving.

oe a

se hn
nae i
PAS oy
id ie

MUNICIPAL APPOINTMENTS ao

From the treasurer’s accounts it appears that the emolu-
ments attaching to this appointment amounted, in all, to 314
florins per annum.’ Later entries show, however, that by
1699 Leeuwenhoek’s grant had been increased to 400 florins
yearly ; while a still later entry,” in 1711, shows that at that
time he was receiving an additional salary of 50 florins for
his services as “ generaal-wykmeester’’—an office resembling
that of an English alderman. Both these municipal appoint-
ments were probably sinecures, and their menial obligations
performed by proxy. I note this in order not to convey the
impression that Leeuwenhoek was really—as Richardson and
Plimmer would have us believe—a sort of village beadle.* It
is hardly necessary to add that 450 florins represented a much
larger sum of money in the XVII Century than they do
today.

To preserve the historic perspective I must here venture
once more to remind the reader of contemporary affairs in the
world at large. In 1664, when Leeuwenhoek was 32 and had
been Chamberlain for some 4 years, his mother—as we have
already heard—died: but in this same year another memorable
event also occurred. England and Holland were then again
at war; and our Admiral Holmes* attacked and captured the
Dutch colony of New Amsterdam on Manhattan Island in
North America, and changed its name to New York in honour
of his chief—the Duke of York, afterwards our King James II.
Englishmen, Hollanders, and Americans—not to mention
men of other nations—therefore have good reason to
remember this epoch. But we must return to our real hero,
who wisely took not the least notice of politics or warfare.

It has recently come to light that Leeuwenhoek was not
only a draper and sheriffs’ chamberlain but also a qualified

‘The sum was made up as follows: For acting as Chamberlain,
260 florins; for cleaning the Chambers of the Sheriffs, Council, etc., and
on account of expenses necessarily incurred thereby, 54 florins. (Haaxman,
1875.)

* Quoted by Haaxman (1875).

* Bedellus immortalis Richardson (1885)—unblushingly borrowed by
Plimmer (1913)—is not only an unsuitable designation for L. but is in
addition (under the Rules of Nomenclature) an invalid synonym of the more
adequate name Homo sapiens Linnaeus.

“Sir Robert Holmes (1622-1692), a great but now almost forgotten
warrior who distinguished himself on many other occasions.

3

34 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS”

surveyor. This discovery illuminates various passages in
his letters, where he enters into arithmetical calculations
regarding areas, volumes, heights, magnitudes of organisms,
and so forth. ‘The act of his admission as_ surveyor
(landmeter) in 1669 is extant in the Dutch State Archives,
and seems sufficiently interesting to quote. It runs as
follows :”

FoRASMUCH AS ANTONY LEEUWENHOECK,° burgher and
denizen of the town of Delft, hath made petition unto the
Court of Holland, saying that he hath for some while
heretofore exercised himself in the art of Geometry, and
advanced so far that he deems himself capable to fulfil
henceforth the office of surveyor, and perform the service
and duty thereof, wherefore he humbly intreateth that
the Court be pleased to permit him to exercise the office
of surveyor, after previous examination and trial of his
ability : ACCORDINGLY, the said Court, having heard the
report of the commissioner appointed thereunto, in whose
presence the applicant was examined by the mathematician
Genesius Baen* as to his aptness for the performing the
foresaid office of surveyor, wherein he was found competent,
hath allowed the application and hereby authorizes the
applicant to perform the office and duty thereof, within
the jurisdiction of the Court ; and hath administered unto
him the statutory oath, that he acquit himself well and
truly therein, by the hands of Mr. Pieter Ockers,’ councillor

ee ———

‘ Ascertained by the late Mr Bouricius, though not published by him.
It appears that Dr Baart de la Faille, archivist of Haarlem, supplied him
with the reference to the relevant entry in the Archives. Cf. Schierbeek
(1929a, 19380).

2 Extract from 12de memoriaalboek van mr. Adriaens Pots, fol. 17.
Rijksarchief : fide Schierbeek (1929a, 1930). Dr Schierbeek first published
the entry from Mr Bouricius’s MS. remains; and the above is my English
translation of his printed versions, checked by a photographic copy of the
Dutch original which he has kindly sent me.

* The name is so spelled in the original.

4 Paen Schierbeek (1930) : a misreading.

5 Ochers according to Schierbeek (1930); but this is also an obvious
misreading or misprint.

Vil

7
4

PLATE

anDYET au.

‘(GLOIT-GE9T) teomtoA uve Aq Suyured-io ayy

MTHa HO MHIA

19qje

ygnos

iS)

gy Woy

SUILYSPUIND PAT

facing p. 35

SURVEYOR AND TRUSTEE 35

at Court, and commissioner appointed therefor. Ordered

in Council the 4th day of February 1669.

There is at least one direct reference to surveying in
Leeuwenhoek’s writings, and it now acquires new significance
in the light of the foregoing record. In the postscript to a
letter written in 1713—containing some celebrated remarks
on whales—he wrote: '

The height of the Tower of our New Church” was
measured many years ago by me and the late Surveyor
Spoors, each with his own quadrant, and found to be 299
feet high

For the year 1676 there is an entry in the Archives of Delft
which illuminates Leeuwenhoek from an entirely different
angle. Under date 30 September it is there recorded : °

Their Worships the Sheriffs of the Town of Delft do
hereby appoint Anthonij Leeuwenhouck* to be Trustee ”
for the estate and property of Catharina Bolnes, widow
of the late Johannes Vermeer (in his lifetime Master
Painter) and petitioner for a writ of insolvency,” for what
he remained possessed of . . . Ordered the 30th of
September 1676.

Now the incomparable artist Jan Vermeer was born at
Delft in the same year as Leeuwenhoek himself (1632), their

' Send-brief IV, 14 March 1713. To Jan Meerman, Burgomaster of
Delft. Published (Dutch) in Brieven, Vol. IV, p. 38; (Latin) Op. Omn.
Vol. IV, p. 38. (No MS. and not in Phil. Trans.)

* Visible in Vermeer’s view (Plate VII)—in the distance, to the right of
the middle line.

® Kamerboek der Stad Delft, 1671-1684: fide Obreen (1881-2), who has
published the entry (p. 295) and from whose printed Dutch version I translate.

* So spelled in original, fide Obreen.

> Curateur orig.

° Impetrante van mandement van cessie orig. These legal terms have no
exact equivalents in modern English, though their meaning seems plain.
According to Meijer’s Woordenschat (1745), impetrante = verkrijgster and
mandement = bevel: while ‘‘mandement van cessie’’ is there explained as
‘om zyne inschulders te mogen dagen’’, and “ Brieven van cessie’’ are defined
as ‘ Brieven van Boedel afstand te mogen doen.”

36 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”’

baptisms’ being entered on the very same page of the Register
of the New Church: and he married Catharina Bolnes (alias
Bolenes) on 5/20 April 1653. He was buried in his native
town on 15 December 1675 at the early age of 43, leaving his
widow with eight children (all under age), an insolvent estate,
and some of the world’s finest pictures. ‘To meet her creditors
Catharina Vermeer was forced to file a petition in bankruptcy
and realize her assets: whereupon—as we see—the Sheriffs
nominated Leeuwenhoek to act as “curator” or “ official
receiver”. Everything regarding this affair now ascertainable
from the Delft Archives has already been extracted and
published by Obreen (1881-2) and Bredius (1885) ; and as the
incident has but little present interest, | must refer readers
seeking further information to their publications.’

Obreen has inferred* that Leeuwenhoek’s appointment as
administrator of Vermeer’s estate was one of the “ pickings ”
to which he was entitled by virtue of his office as Chamber-
lain. Obreen may be right: but it seems hardly likely that
Leeuwenhoek derived any profit from his trusteeship of the
affairs of an insolvent family, and the extant records (as
published) show only that he met with worries and legal
difficulties in the discharge of his duty. To me the incident
appears rather to indicate that Leeuwenhoek may have been a
personal friend of the Vermeers, though it also shows clearly
that he himself must have held a solid position as a citizen of
Delft at that date; since it is inconceivable that the Sheriffs
could have nominated anybody but a respected fellow-
townsman to disentangle Vermeer’s involved finances.
For Vermeer—though soon forgotten and only recently
rediscovered—was then rightly regarded as a great artist and
ornament of the Town, and his wife apparently had well-to-do
connexions.

' Vermeer’s was registered on 31 Oct. 1632: so this was not the date
of his birth—as many writers state. The date of his birth is actually
unknown.

* I have had considerable difficulty in ascertaining the above particulars
about Vermeer and his relations to Leeuwenhoek, because most biographers
of both these great Delvenaars give little or no trustworthy information on
the subject. On Vermeer cf. also Plietzsch (1911), Vanzype (1921), Lucas
(1922), Chantavoine (1926).

* Obreen (1881-2), p. 295.

VERMEER. WINE-GAUGING om

One other municipal function which Leeuwenhoek is now
known to have discharged is that of wine-gauger (wijnroeijer)."
He was elected to this post on 15 August 1679, and apparently
occupied it (partly by proxy) for the rest of his life. The
terms of this office are too long to print here in extenso. It
must suffice to note that the wine-gauger had to assay all
wines and spirits entering the town, and to calibrate the
vessels in which they were contained; while he was himself
debarred from engaging in any trade connected with liquor.”
This appointment again throws some light upon our Leeuwen-
hoek: for his personal knowledge of wines—including their
effects and antidotes—will be evident to all attentive readers
of his letters.

From the date of his appointment as Chamberlain in 1660
nothing was heard of Leeuwenhoek outside of Delft for thirteen
years, though we may be sure that he was not idle during this
interval. But in 1673 we hear of him again in an altogether
unexpected connexion. Our Dutch Draper-Chamberlain is
now suddenly discovered to us as an amateur of science—
offering a paper, containing some modest original observations,
for publication in the Philosophical Transactions of the Royal
Society of London.

How this came about is soon told. The Royal Society,
then but recently founded,* was eager to get into communica-
tion with allmen—no matter what their rank or nationality—
who were working for “ the promotion of natural knowledge” : *
and in this endeavour it was successful, in no small measure,
through the efforts of its energetic secretary Mr Oldenburg

1 First recorded by Morre (1919) and Bouricius (1925). The latter has
kindly supplied me (from the archives of Delft) with full particulars—partly
given above—relating to the functions of a wine-gauger.—There is, I find,
an early Dutch work on gauging by Cornelis van Leeuwen (1663), with
which L. was probably familiar and which describes the technique fully.

? Since these lines were written Schierbeek (1929) has published the
regulations regarding the office of wine-gauger in greater detail.

° Readers desirous of knowing more about this historic event may be
referred specially to the works of Sprat (1667) and Weld (1848); and also
to the more recent Record of the Roy. Soc. (1912) and the posthumous
publication of Miss Ornstein (1928).

*“They [the Royal Society] exact no extraordinary praeparations of

Learning: to have found Senses and Truth, is with them a sufficient
Qualification” (Sprat, 2 ed. (1702), p. 435).

38 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”

(Plate VIII). His foreign correspondence was enormous, as
can be gathered from the manuscript letters to and from him
still preserved by the Society. Among the Roy. Soc. MSS.
(to mention no others) are drafts of more than 400 letters—
apart from numerous translations and many other documents—
written by Oldenburg to various more or less celebrated and
scientific persons between the years 1657 and 1677: while the
extant letters addressed to him well exceed 1200 in number.
Henry Oldenburg (1615 ?—1677),* first Secretary of the
Royal Society,” was a remarkable man. He was a German
of good family—a native of Bremen—who came to England
about 1640 and afterwards played a prominent part in con-
temporary English scientific life. He is now chiefly remem-
bered, however, as a translator and as the first editor of the
Philosophical Transactions and as a correspondent with nearly
all outstanding “ philosophers” and “virtuosi” of his day.
Curiously enough, no adequate biography of this influential
figure in the History of Science has ever yet been published.
It may be noted in passing that several scientific letters
written to Oldenburg—including some of Leeuwenhoek’s—
are addressed to ‘“‘ Mr. Grubendol”’. He sometimes used this
anagram when corresponding with foreigners, apparently, in
order to avoid suspicion through receiving too many com-
munications from abroad in his proper name. It was a
transparent subterfuge which reflects no discredit upon him:
but that his fears were well founded is clear from the fact
that he was actually imprisoned, as a suspected spy, towards
the end of June, 1667. Pepys,’ in his Diary, under the
date 25 June 1667, notes: “I was told, yesterday, that Mr.
Oldenburg, our Secretary at Gresham College, is put into the

‘For his life see Birch, Vol. III, p.3853; Rix (1893); and the Dict.
Nat. Biogr. The date of his birth is not certainly known; but it was not
1626, as usually stated.

> Jointly with John Wilkins (1614-1672), D.D.; Master of Trinity
College, Cambridge (1659); later Bishop of Chester (1668). Wilkins was
also a man of considerable parts. A collective edition of his ‘mathematical
and philosophical works”’ appeared in 1708 (with a portrait and the author’s
life prefix’d).

* Samuel Pepys (1633-1703) was elected Fellow of the Royal Society in
1665 and President in 1684.

PLATE VIII

Fioyal Society London
HENRY OLDENBURG (1615 ?-1677)

First Secretary of the Royal Society, 1663-1677

From an oil-painting by Jan van Cleef (1646-1716) made in the year 1668.

facing p. 38

ee we Kaw, | hs :
a

es nr) en re)

nN af Y , uy
| Y ee ieee a)

HENRY OLDENBURG, SEC. ROY. SOC. 39

Tower, for writing newes’ to a virtuoso in France, with
whom he constantly corresponds in philosophical matters;
which makes it very unsafe at this time to write, or almost
do anything.” Weld,’ who has given a more circumstantial
account of this incident, calls it “a very remarkable event
which seems to have had so much influence upon the Society
as to cause a suspension of the Meetings from the 30th May
to the 3rd October”. Yet the event appears less remarkable
when we remember that the citizens of London—already
severely shaken by the Great Plague and the Great Fire of
the two previous years—were listening, for the first time,
to the guns of a foreign fleet advancing up the Thames
at the moment when they clapped Oldenburg in jail. Evelyn
says*® “‘The alarme was so greate that it put both Country
and Citty into a paniq, feare and consternation, such as I
hope I shall never see more.”” But the Londoners were then
feeling far more afraid of the fierce Dutch Admiral de Ruyter
than of the mild German-English scientist, and poor Olden-
burg was soon exonerated. On his release from the Tower he
wrote to Boyle (8 September 1667): “I hope I shall live fully
to satisfy his majesty and all honest Englishmen of my
integrity, and of my real zeal to spend the remainder of my
hfe in doing faithful service to the nation to the very utmost
of my abilities’: which he did.

Among Oldenburg’s innumerable correspondents was the
youthful but already famous Dutch physician Reinier de
Graaf,’ a friend and fellow-townsman of Leeuwenhoek. (See

_ ‘Cf. also Evelyn (Diary, 8 Aug. 1677) : ‘‘ Visited Mr. Oldenburg, a close
prisoner in the Tower, being suspected of writing intelligence.”’

* Weld (1848), I, 201 sq.

* Diary, 18 June 1667. John Evelyn (1620-1706) was an original
Fellow of the Royal Society, and Secretary in 1672.

* Reinier [sew Regnerus ] de Graaf (1641-1673) was born at Schoonhoven,
studied under Sylvius at Leyden, and practised (and died) at Delft. His
anatomical researches——especially upon the organs of generation—are still
well known. The “ Graafian follicle’? of the ovary (which he regarded as
an egg) enshrines his memory. His Opera Omnia were first published
posthumously at Leyden in 1677. (L. has left it on record that his
untimely death was hastened by his embittered controversy with
Swammerdam over the priority of their anatomical discoveries.) He did
not live to be elected a Fellow of the Royal Society, but died at the age of
32, after a brief but brilliant career, in the very year in which he introduced L.

40 LEEUWENHOEK AND B!s “ LITTLE ANIMALS”

Plate [X.) During the silent ,eriod preceding the year 1673
Leeuwenhoek was evidently engaged—in his spare time, when
he was not selling buttons and ribbon—in making lenses, and
mounting them to form “ microscopes ”’ of simple pattern: and
after he had acquired much skill in the manufacture of these
curious instruments,’ and had taught himself how to grind and
polish and mount lenses of considerable magnifying power, he
began to examine all manner of things with their aid. Dr
de Graaf was personally acquainted with Leeuwenhoek’s work,
and had had. opportunities of inspecting various objects
through his glasses.

In the Philosophical Transactions for 1668 the editor had
published’ an extract from the Giornale dev Letterati, con-
taining an account of a new microscope made by Hustachio
Divini in Italy. With this instrument, it was claimed, he
had been able to discover “an animal lesser than any of those
seen hitherto.” It was doubtless as a counterblast to this
sweeping assertion, and with pardonable patriotism, that
de Graaf (28 April 1673) addressed himself to Oldenburg in
the following words :*

That it may be the more evident to you that the
humanities and science* are not yet banished from among
us by the clash of arms,’ I am writing to tell you that a

* Cf. p. 313 sq., infra.

* Phil. Trans. (1668), Vol. III, No. 42, p.842—then edited by Oldenburg.
Divini’s portrait can be seen in the work of Manzini (1660).

* The original letter, from which I here translate a part, is still preserved
by the Royal Society (MS. No. 1168; G.Z. 11). It is written in Latin, and
an extract—in English—was published in Phil. Trans. (1673), Vol. VIII,
No. 94, p. 6037. The letter was read at the meeting of the Society held on
7 May 1673 [0.S.], when L.’s first observations were also communicated.
Cf. Birch, Vol. III, p. 88.

* studia humaniora et philosophica MS.

° I may remind the reader that a European war was being waged at this
time, and that England was actually at war with Holland. Peace was not
concluded between us until February, 1674; but communications apparently
remained unbroken throughout—probably because “the Nations had been
at War without being angry; and the Quarrel had been thought on both
Sides rather of the Ministries than the People’”’ (Sir William Temple (1709),
Memoirs [1672-1679] p.3). Contemporary writers, both in England and
in Holland, afford numerous other gratifying instances of the lack of personal
enmity between our two peoples. For example, the Earl of Castlemain

PILATE) US

LNs itt

i

HA

ll

if Hi

a

iui
a
i
(i

it i |
‘il

REINIER DE GRAAF (1641-1673)

til

i EESERSS:

From the unsigned engraving prefixed to his posthumous Opera Omnia.

fucing p. 40

DE GRAAF AND THE ROYAL SOCIETY 41

certain most ingenious person here, named Leewenhoeck,'
has devised microscopes which far surpass those which
we have hitherto seen, manufactured by Eustachio Divini
and others. The enclosed letter from him, wherein he
describes certain things which he has observed more
accurately than previous authors, will afford you a sample
of his work: and if it please you, and you would test the
skill of this most diligent man and give him encourage-
ment, then pray send him a letter containing your
suggestions, and proposing to him more difficult problems
of the same kind.

The enclosed specimen of Leeuwenhoek’s work consisted
of various rather crude observations on Mould; on the sting
and mouth-parts and eye of the Bee; and on the Louse. It
was published in English in the Philosophical Transactions *
with some comments by Oldenburg, who wound up by
remarking (somewhat sardonically, I fear) “So far this
observer: who doubtless will proceed in making and imparting
more Observations, the better to evince the goodness of these
his Glasses’”—a prophecy which was actually fulfilled more
amply during the next fifty years than anybody could then
have thought possible. Yet the Fellows evidently liked the
observations, and Oldenburg was instructed to communicate
with their author. To his letter Leeuwenhoek sent the
following characteristic answer from “‘ Delff in Hollant”:*

(1671, p. 97) remarks “We have now finisht a sharp and bloody War, which
nevertheless leaves not the least rancor (that I know) in the heart of any
English man; and the reason of it is, because we have generally an affection
for these our neighbors [the Dutch], esteeming them an industrious and
sober people’’.

* So spelled in original.

2 Letter 1. See Phil. Trans. (1673), Vol. VIII, No. 94, p. 6037. The
original MS. has not been preserved by the Society, and is presumably no
longer extant.

® Translated from Letter 2 (15 August 1673). MS.Roy.Soc. The original
is in Dutch. Cf. Plate X. The drawings were engraved and published in
Phil. Trans. (1673), Vol. VIII, No. 97, but their originals are lost. The
part of this letter here translated has not been published previously, but
some extracts from the remainder were printed—in English, in two parts—
in Phil. Trans. (1674), Vol. IX, No. 102, pp. 21-25.

ce

42 LEEUWENHOEK AND HIS “LITTLE ANIMALS ”’

I have oft-times been besought, by divers gentlemen, to
set down on paper what I have beheld through my newly
invented Microscopia: but I have generally declined;
first, because I have no style, or pen, wherewith to express
my thoughts properly; secondly, because I have not been
brought up to languages or arts, but only to business; and
in the third place, because I do not gladly suffer contra-
diction or censure from others. This resolve of mine,
however, I have now set aside, at the intreaty of Dr Reg.
de Graaf; and I gave him a memoir on what I have
noticed about mould, the sting and sundry little limbs of
the bee, and also about the sting of the louse. This
memoir he (Mr de Graaf) conveyed to you; whereupon
you sent me back an answer, from which I see that my
observations did not displease the Royal Society, and that
the Fellows desired to see figures of the sting and the
little limbs of the bee, whereof I made mention. As I
can’t draw, I have got them drawn for me, but the
proportions have not come out as well as I had hoped to
see ’em; and each figure that I send you herewith was
seen and drawn through a different magnifying-glass. I
beg you, therefore, and those Gentlemen to whose notice
these may come, please to bear in mind that my observa-
tions and thoughts are the outcome of my own unaided
impulse and curiosity alone; for, besides myself, in our
town there be no philosophers who practise this art; so
pray take not amiss my poor pen, and the liberty I here
take in setting down my random notions.’

Exactly a week before Leeuwenhoek dispatched the fore-
going letter to the Royal Society, some further information
about himself had been sent to one of the Fellows by
Constantijn Huygens’—the once celebrated diplomatist and

" gedachten, die ick als overhoop hier onderstel MS. It is difficult to
render these words exactly in modern English.

* Constantijn Huygens (1596—1687), statesman, poet, musician, and
man of letters—‘ the most brilliant figure in Dutch literary history. Other
statesmen surpassed him in political influence . . . but his talents

PLATE X

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facing p. 42

LETTER 2. CONST. HUYGENS 43

poet who is now best known to men of science as father of
Christiaan Huygens the mathematician and astronomer. On8
August 1673, Sir Constantijn wrote (in English, as here given)
to Robert Hooke :*

Our honest citizen, Mr. Leewenhoeck—or Leawenhook,*
according to your orthographie—having desired me to
peruse what he hath set down of his observations about
the sting of a bee, at the requisition of Mr. Oldenburg,
and by order, as I suppose, of your noble Royal Society,
I could not forbear by this occasion to give you this
character of the man, that he is a person unlearned both
in sciences and languages, but of his own nature exceed-
ingly curious and industrious, as you shall perceive not
onely by what he giveth you about the bee, but also by
his cleere observations about the wonderfull and trans-
parent tuwbulc appearing in all kind of wood . . . His way
for this is to make a very small incision in the edge of
a box, and then tearing of it a little slice or film, as I
think you call it, the thinner the better, and getting it
upon the needle of his little microscope—a machinula of
his owne contriving and workmanship—brass*®’ . . . I
trust you will not be unpleased with the confirmations
of so diligent a searcher as this man is, though allways

were more varied, and his general accomplishments more remarkable than
those of any other person of his age, the greatest age in the history of the
Netherlands. Huygens is the grand seigneur of the republic’? (Edmund
Gosse). He was also the friend and confidant of L. King James I knighted
him in 1622—+ten years before L. was born.

* The original letter is preserved among the MSS. in the Royal Academy
at Amsterdam, and has been recently printed by J. A. Worp (1917), Brief-
wisseling van Const. Huygens, Vol. V1; No. 6909, p.330. A part has been
copied—not too accurately—by Vandevelde (1924a, p. 289), who wrongly
dates the letter Aug. 3—On Hooke see note 1 on p. 47 infra.

* Cf. p. 304 infra.

* This word (brass, following a dash) occurs thus in the MS. but is
omitted from the printed letter by the modern editor (Worp), who says it
is “‘ unintelligible”. To me, however, it appears very easy to understand:
Huygens meant that L.’s little microscope was “made of brass’’—as so
many of his instruments were.

44 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

modestly submitting his experiences and conceits about
them to the censure and correction of the learned.

The foregoing extracts show clearly how Leeuwenhoek’s
relations with the Royal Society originated: and they dis-
prove, I think, a statement which has been made elsewhere '
that he owed his introduction to Sir Constantijn Huygens.

From the time when his words quoted above were written
until the day of his death, fifty years later, Leeuwenhoek
continued to send letters to the Royal Society. They cover
an immense field, and contain observations on matters z0o-
logical, botanical, chemical, physical, physiological, medical,
and miscellaneous (unclassifiable). They are mostly—but not
entirely—concerned with observations and discoveries made
with the microscope. But this is not the place to speak of
their contents in detail: and I shall only add here that many
of them—but not all—were published, more or less curtailed,
in English (or occasionally in Latin) in the Philosophical
Transactions from 1673 to 1723; and that many of them—
but not all—were issued fully in Dutch and Latin,’ as separate
publications, in his lifetime. He himself spoke and wrote and
understood Dutch only,’ and versions of his views in any other
tongue suffer from the inevitable defects of translation and
interpretation. Consequently, one must be able to read old-
fashioned Dutch to read Leeuwenhoek: and for my own part

* In the @uvr. Compl. de Chr. Huygens, Vol. VII, p. 316 (footnote)—
published in 1897—it is averred (I know not by whom) that MS. letters at
Amsterdam, which passed between L. and Constantijn Huygens (pater), and
between the latter and Robert Hooke and Oldenburg, show that L.’s first
relations with the Royal Society were established through the intermediation
of Const. Huygens: but the documentary and other evidence at my disposal
seems to show incontrovertibly that the statements made above are correct.

* Tt is not now known who translated L.’s letters into Latin for the
editions of his works in that language. It is obvious—from the Latin
styles, and the period of time covered—that the translations were made by
more than one hand; but all my attempts to solve this problem have
hitherto been fruitless. At one moment I thought I had discovered the
name of one of his translators: for in an English MS. version (unpublished)
of one of his later letters there is a reference to the translator as © Mynheer
Aalder”’. But on consulting the original, I found that this was merely a
misreading of the words “de Heer vertaalder’’ [= the translator] in the
Dutch manuscript !

* See p. 305 sq., infra.

LETTERS 45

I would say that it is well worth the trouble of learning this
admirable language merely for the pleasure of reading this
admirable man’s admirable letters.

All Leeuwenhoek’s recorded observations were described
in letters. He never wrote a book or a scientific paper—only
letters, and still more letters, addressed to all manner of
people. His letters were all written by himself in his own
old-fashioned Dutch, though they were often translated by
others into other languages, published in many different ways,
and collected in various volumes at divers dates by different
editors. All his own original writings are distinguished by
a certain businesslike formality, but almost total lack of
coherence. After presenting his compliments, he just wrote
down what he wanted to say at the moment—recording now
perhaps a few experiments, with his speculations about their
significance, then adding a few personal remarks, and winding
up with a mass of further observations and thoughts on some
totally different topic. He wrote much as he must have
spoken, so that his letters have an extraordinarily colloquial
and familiar flavour which conveys—to me, at least—a strange
sense of intimacy. He wrote as loosely and discursively as
other people usually speak—just as though he were talking
to a friend who obviously understood his common everyday
speech: and he was always so intent on telling what he had
seen or thought that he had no time to worry about grammar
or the niceties of literary composition. Consequently, his
writings are more like conversations than formal letters. He
would certainly have agreed with his sweet English con-
temporary, Dorothy Osborne,’ when she said: “ All letters,
methinks, should be free and easy as one’s discourse; not
studied as an oration, nor made up of hard words like a charm.
Tis an admirable* thing to see how some people will labour
to find out terms that will obscure a plain sense... .”’ And
he would also have agreed with James Howell’ that “ we

* Dorothy Osborne (1627-1695) ; afterwards wife of Sir William Temple,
sometime English Ambassador to Holland. I quote from Letter 33 of
Parry’s edition of her letters to Temple. The words quoted were written at
some unknown date in 1653.

* Meaning, of course, “ wonderful” or ‘‘ marvellous’”’—not ‘‘ admirable”’
(=to be admired or approved) in the modern sense.
* James Howell (1594 ?-1666), celebrated author, linguist, and letter-

writer. I quote from the 1705 edition of his Hpistolae, p.1 (letter dated
25 July 1625).

46 LEEUWENHOEK AND HIS “LITTLE ANIMALS”’

should write as we speak; and that’s a true familiar Letter
which expresseth one’s Mind, as if he were discoursing with
the Party to whom he writes in succinct and short Terms.”
But whether serious scientific work should be published in so
plain and unceremonious a fashion is, of course, debatable
nowadays.

Yet there can be no doubts in the mind of anyone who
seriously studies his writings that Leeuwenhoek—as he so
often tells us—worked entirely by himself. He received no
help from contemporary microscopists, and was wholly
inspired by his own inborn genius. Indeed, he disliked and
resented interference, and distrusted the knowledge—and
sometimes the purpose—of people who went to see him or
who offered him advice: and for this he evidently had good
reasons. Writing to Oldenburg as early as 1675 he
remarked : *

Your Excellency recommends me to make use of the
services of other people, who are in a position to form a
proper judgement of such things. Sir, I must say that
there be few persons in this Town from whom I can get
any help; and among those who can come to visit me
from abroad, I have just lately had one who was much
rather inclined to deck himself out with my feathers,
than to offer me a helping hand.

It was not until 1680, after Oldenburg had died and when
he himself was in his 48th year, that Leeuwenhoek was
elected a Fellow of the Royal Society. As the date and other
details are frequently given wrongly by biographers I must
here briefly chronicle the relevant facts. For his election

* Carbone (1930) has recently tried to show that L. was inspired by the
Italian workers of his time. But Carbone’s only evidence for this is a
letter (attributed by him to L.) which he has “discovered”? among the
Magliabechi MSS. at Florence. It is certain, however, that this letter
(dated 2 May 1692) was not written by Leeuwenhoek but by Leibniz. (It
is in Latin, and unsigned: but it bears Leibniz’s seal, much internal
evidence of his authorship, was written from Hanover, and had previously
been published as an authentic Leibniz letter by Targioni-Tozzetti in 1746.)

*From Letter 12. 14 August 1675. To Oldenburg. MS. Roy. Soc.
Incompletely abstracted in English in Phil. Trans. (1675), Vol. X, No. 117,
p. 380. Not published elsewhere.

ELECTION TO THE ROYAL SOCIETY 47

was, to him, an event of the first magnitude, and an unfailing
source of encouragement for the rest of his life.

From letters still extant it appears that Hooke! wrote to
Leeuwenhoek early in 1680, and expressed surprise that his
name was not upon the list of Fellows of the Society: and he
also then offered, apparently, to propose him for election. To
this letter Leeuwenhoek replied” that he had “never had a
thought of pretending” to such a distinction, though he
would “thankfully have acceded if Mr Oldenburg, in his
lifetime,” had afforded any opening”: and he would regard
election to the Fellowship, he says, as “‘the greatest honour
in all the world”’.

This letter was written on 13 February 1680 [N.S.] in reply
to Hooke’s dated 23 January 1680 [O.S.]; but the election
actually took place on 29 January|O.S.|—before Leeuwenhoek’s
answer could have been received in England. Moreover,
Hooke was not the proposer : for it is recorded by Birch ‘—and
accurately, as reference to the minutes shows—that on 29
January 1679/80 [O.S.] “Dr. Heusch,° Mr. Firmin® and

* Dr Robert Hooke (1635-1703), an original Fellow of the Royal Society,
was also an original and eccentric genius and inventor. His contributions
to science are too well-known and numerous to mention; though his
influence on his contemporaries, and the part he played in the early days of
the Society, are only just beginning to receive their due recognition.
Inadequate accounts of his life will be found in Waller (1705) and the Dict.
Nat. Biogr.—also in some more recent publications. It is impossible and
unnecessary to discuss this remarkable man and his work here.

* Letter 29b. 18 February 1680 [N.S.] to R. Hooke. MS. Roy. Soc.
Unpublished. This letter was translated by Francis Aston, and read at a
meeting of the Society held on 12 Feb. 1680 [0.S.]. Cf. Birch, Vol. IV,
pel. j

* Oldenburg died, it will be recalled, in 1677. Hooke and Grew were
appointed Secretaries in the same year, while Gale succeeded to this office
in 1679.

; Bireh, Vol. FV, p.'6.

* Johann Christian Heusch, M.D., principal physician to the Elector
Palatine but otherwise apparently undistinguished. He attended a meeting
of the Society on 22 Jan. 1680, and subsequently signed his name in the
register. Cf. Birch, Vol. IV, pp. 5, 7.

* Thomas Firmin (1632-1697), citizen of London, remembered only as a
philanthropist. Though a Fellow of the Society he was not a man of
science. See Dict. Nat. Biogr. and life by Cornish (1780).

“cc

48 LEEUWENHOEK AND HIS “LITTLE ANIMALS”

Mr. Houghton’ were elected; as was also Mr. Leewenhoeck
upon the motion of Dr. Croune,’ and Dr. Gale* was desired to
draw up a diploma to be sent to him.”

There is thus ample documentary evidence to prove that
Leeuwenhoek was elected a Fellow of the Royal Society—a
full Fellow, and not a Foreign Member,’—on 29 January
1679/80 [0.8.]; that is, on 8 February 1680 according to
present-day reckoning [N.S.].’ He was proposed by Croone—
not by Hooke—and his election was unanimous.°

At the gathering of the Society on 12 February [0.S.]
1680, ‘‘ Dr. Gale was called upon for the diploma directed at
the meeting of January 29 to be sent to Mr. Leewenhoeck ;
and it was ordered, that the society’s seal should be affixed to
it, and that a silver box should be provided for it.”" Later, at
the same meeting, “Dr. Gale produced his draught of a
diploma for Mr. Leewenhoeck”’*: and on February 19, “it was
ordered, that the arms of the society be ingraved on the silver
box.”® Finally, at a meeting of Council on February 23,
it was directed “‘ That Mr. Hunt” prepare a silver box for the
diploma to be sent to Mr. Leewenhoeck ;”’" and on the 28th

* John Houghton (?—1705), now imperfectly known as a writer on
husbandry (especially on potatoes) and trade. See Dict. Nat. Biogr.

? William Croone [sew Croune] M.D. (1633-1684), educated at Emmanuel
College, Cambridge, was an original Fellow of the Royal Society and a well-
known physician in his day. The “Croonian Lectures”’ still serve to
perpetuate his memory. See Birch, Vol. IV, p. 339 and Dict. Nat. Buogr.
for further details of his life and legacies.

* Thomas Gale, D.D. See p. 193, note 2, infra.

* “ Foreign Members” were an invention of a much later date. Cf.
Nuttall (1921) and Dobell (1923).

° Boitet (1729, p. 766) wrongly gives the date as 26 February 1679, and
has been copied by Soutendam (1875) and others.

® So Hookeinformed him. See Letter 31a,13 May 1680. To R. Hooke.
MS. Roy. Soc. Unpublished. Cf. also p. 87 znfra.

" Birch, Vol. IV, p. 11.
* Birch, Vol. IV, p. 13.
* Birch, Vol. IV, p. 13.

* Henry Hunt was the Society’s ‘‘ operator,’ who assisted at demonstra-
tions and in other ways. He filled the offices of laboratory attendant,
assistant secretary, and general factotum—for £40 a year (when he could
get it)—and left the Society a legacy on his death.

” Birch, Vol. IV, p. 16.

PLATE XI

y '—_—_______. > -__ re - ‘ _ “i eicoses
F = F
C

fiijksmuseum Amsterdam

ANTONY VAN LEEUWENHOEK (1632-1723)

From the oil-painting made in 1686 by Johannes Verkolje (1650-1693).

facing p. 49

ANTONY VAN LEEUWENHOEK, F.R.S. 49

“The president’ took with him the diploma for Mr.
Leewenhoeck, and presented the Society with a screw-press for
sealing such diploma’s.” ®

Unfortunately the “‘ diploma,” though safely delivered * in
Delft, is now lost; but it is portrayed in Verkolje’s oil-painting
of Leeuwenhoek,* wherein it is shown as a vellum scroll with
a pendent red seal. Curiously enough, it was apparently
engrossed in Dutch’—not in Latin—in deference to the re-
cipient’s ignorance. On receipt of this document, with its big
red seal and in its engraved silver box, Leeuwenhoek returned
the following acknowledgement :°

Delft, 13th May 1680.
To the President, Council,
& Fellows of the Royal Society.
Gentlemen,

I was quite taken aback to hear that the members of
the Roy. Society had been pleased to confer upon me, all
undeservedly, so much honour and dignity as to admit me
a Fellow of the same most worthy College; as I first
learnt from a letter written by Mr Secretary Thos. Gale,
and a bit later through the receipt of a sealed Diploma ;
whereof both were full of expressions on my behalf that

Sir Joseph Williamson (1633-1701), statesman.
> Birch, Vol. LV, p. 21.

* Halbertsma (1843, p. 19) says he had heard [wt audivi’’—no
authority quoted] that L. received the diploma from the British Ambassador
at The Hague. This seems likely enough; but I have sought in vain for any
confirmation of the statement.

* Now in the Rijks-Museum (see Plate XI). It is not shown in Verkolje’s
mezzotint (see Frontispiece).

° Several words are clearly legible in the painting.

° Letter 31b. 13 May 1680 [N.S.]. To the Royal Society. MS.Roy.Soc.
Unpublished. The original is in Dutch, and the above is my translation :
but I confess my inability to convey to the modern English reader the
extraordinary mixture of formal and familiar, colloquial and commercial,
and above all genuine and sincere phraseology of the ancient original.
A similar letter (No. 31a, also unpublished) was sent to Robert Hooke
personally at the same time (dated 13 May 1680 [N.S.] MS.Roy.Soc.).
Both letters were communicated to the Society by Hooke on 13 May [0.8.].
Cf. Birch, Vol. IV, p. 37.

4

50 LEEUWENHOEK AND HIS “LITTLE ANIMALS”’

my merits must fall far short of. Under which protest
I notwithstanding hold myself most straitly pledged
hereby, by unalterable intent and promise, to the Fellows
of the said Society, for the signal favour they have shown
me, to strive with all my might and main, all my life
long, to make myself more worthy of this honour and
privilege.

Wherewith commending you, most noble Gentlemen,
one and all, to the merciful protection of Almighty God,

I remain, Gentlemen,
Your most humble servant
Antony Leeuwenhoek.

An amusing sidelight is thrown upon Leeuwenhoek at this
moment in his career by a passage in a letter to Christiaan
Huygens from his brother Constantijn." Writing on 13
August 1680 he says’:

Everybody here is still rushing to visit Leeuwenhoek, as
the great man of the century. A few months ago the
people of the Royal Society in London received him
among their number, which gave him some little pride ;
and he even seriously inquired of Sir Father* if, being
now invested with this dignity, he would be obliged in
future to take a back seat in presence of a doctor of
medicine !

Leeuwenhoek never came to London to sign the Register
of Fellows or attend any meeting of the Royal Society. He
was a busy man, and seldom went far from home—though he
tells us of occasional short excursions from Delft in some of
his letters. For example, in those here translated there are

* Constantijn Huygens filius (1628-1697), son of Constantijn pater—the
“grand seigneur”’ and English knight—and elder brother of Christiaan.

2 Printed in Clwres Compl. de Chr. Huygens (1899); No. 2226,
Vol. VIII, p. 295. The original MS. is in the University Library at Leyden,
and is written in French—from which I translate.

3 ql Signor Padre orig.—meaning Sir Constantijn, their father.
Constantijn jun. sometimes lapsed thus into Italian when writing in French
to his brother—whom he called occasionally “ fratello caro”’.

A VISIT TO ENGLAND 51

references to holidays spent at the seaside (Scheveningen) and
“in Brabant and elsewhere.” But he once, before his election,
visited London—though this is not generally known—and
recorded the circumstance in an unpublished passage in an
early letter (1674). What he there says is so interesting, in
more ways than one, that I must quote his words. In the
course of describing some microscopic observations on the
composition of chalk and clay, he unexpectedly adds’ :

About six years ago, being in England, out of curiosity,
and seeing the great chalk cliffs and chalky lands at
Gravesend and Rochester, it oft-times set me a-thinking ;
and at the same time I also tried to penetrate the parts
of the chalk.” At last I observed that chalk consisteth of
very small transparent particles*; and these transparent
particles lying one upon another, is, methinks now, the
reason why chalk is white.

Tt is clear from his own words that Leeuwenhoek spent a
holiday in England sometime during the year 1668." He came
to London—sailing up the Thames by way of Harwich,
Rochester, and Gravesend (after embarking probably at
Rotterdam)—and brought a microscope with him. From this
it seems legitimate to infer, therefore, that he was already
engaged in his microscopic studies in 1668—at least five years
before his first communication with the Royal Society. These

1 Brom Letter 6,7 Sept. 1674. To Oldenburg. MS.Roy.Soc. Incom-
pletely translated into English in Phil. Trans. (1674), Vol. IX, No. 108,
pp. 178-182 [misprinted 821]. From this translation the passage here
given was entirely omitted: and in the following paragraph (p. 181), where
L. speaks of the colour of the English soil, “ die ick aldaer tusschen Harwits
en Londen gesien heb”, his words have been altered to an impersonal
statement about ‘‘ that, which 7s found between Harwich and London” [my
italics].

2 de deelen van het krijt te penetreren MS. By this L. evidently means
that he attempted to study the microscopic structure of chalk. No other
interpretation—if the context be considered—appears to me possible.

® clootgens MS. It is hardly possible to doubt that some, at least, of
these “transparent particles” were fossil shells of Foraminifera.

‘ England and Holland were then temporarily at peace. The second
Anglo-Dutch War was concluded in July, 1667, and the third was not
declared until March, 1672.

ce

52 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”
observations on chalk are, so far as I have yet ascertained, the
earliest dated microscopic investigations recorded by Leeuwen-
hoek: and they dispose of a recent suggestion * that he began
his career as a microscopist under the influence of his second
wife—the “ blue-stocking’”’ Cornelia Zwalmius. He did not
marry this supposedly learned lady ° until 1671; but the fore-
going extract shows that he was already engaged in making
microscopic observations at least three years earlier, and when
we remember that he made all his microscopes and lenses with
his own hands it seems certain that he must have begun his
studies whilst his first wife was still alive.’

By the end of the XVII Century, when he had been
demonstrating the scientific possibilities of the microscope
for more than 25 years, Leeuwenhoek was actually the
only earnest microscopist in the whole world. It is a
remarkable fact that in all his later life he had no rivals
and hardly a single imitator. His observations excited
the greatest interest—but that was all. Nobody seriously
attempted to repeat or extend them. ‘The superexcellence
of his lenses, combined with the exceptional keenness of
his eye, killed all competition. As early as 1692, Robert
Hooke, discoursing on “the Fate of Microscopes”’,’ says
that they “‘are now reduced almost to a single Votary,
which is Mr. Leewwenhoek; besides whom, I hear of none that
make any other Use of that Instrument, but for Diversion and
Pastime”’:’ and he adds later that the microscope at that

* Schierbeek (1929).

* The only evidence that Cornelia was a highly-educated female appears
to be (1) that her father was a clergyman; (2) that her brother was a
doctor; and (3) that she once signed her name “ Swalmia” (instead of
Swalmius) on a legal document—which has been taken to prove that she
knew Latin. There is no evidence, however, to show that she changed the
gender of her patronymic on her own initiative: and it seems to me unlikely
that women were less dependent on their male relatives and friends 250
years ago than they are today.

° It is not known with certainty when L. began making “ microscopes.”’
The recent statements by Garrison (1921, p.835) in a learned work
(1673. Leeuwenhoek makes microscopes”’), and by Mrs Williams-Ellis
(1929, p.13) in a juvenile broadcast (1660. Leeuwenhoek has made
hundreds of microscopes’’), are equally misleading and gratuitous guesses at
the date.

* Published by Derham (1726) in Hooke’s Phil. Expts. é Obss.

® Ibid., p. 261.

L’ACADEMIE DES SCIENCES 53

date ‘‘is become almost out of Use and Repute: So that Mr.
Leeuwenhoek seems to be the principal Person left that culti-
vates those Enquiries. Which is not for Want of considerable
Materials to be discover’d, but for Want of the inquisitive
Genius of the present Age.” ’ These remarks were not due to
the circumstance that Hooke was growing an old man, and
therefore lawdator temporis actv: they are supported by all
scientific publications of the period.

It is often stated’ that Leeuwenhoek was elected a Fellow
not only of the Royal Society but also of the Académie des
Scrences of Paris. The date of his election is variously given
(usually 1697), and it is also sometimes stated that he wrote
a number of letters (usually said to be 26) to this other learned
and royal Society. But no authority is ever quoted for such
statements, and Leeuwenhoek’s name is not included—so far
as I have been able to ascertain—in the lists of Membres de
l’ Académie published prior to the reconstitution of this body
(1699). Moreover, all the ‘“ Letters from Leeuwenhoek” in
the Journal des Scavans appear to be merely extracts or quota-
tions in French from the Philosophical Transactions. I must
confess, however, that I have not searched all the early
publications of the Académie properly—the task appearing
somewhat unprofitable.

As I have not had access to the archives of the Académie
des Sciences—the only present source of authoritative inform-
ation—I have sought the help of my friend Professor F. Mesnil,
Membre del’ Académie, who has very kindly instituted inquiries
on my behalf. Asa result he tells me in a recent letter:* “I
have had the Archives of the Academy of Sciences searched
for information about Leeuwenhoek, and I have been shown

* Ibid., p. 268.

* e.g. by Richardson (1885), De Toni (1923), ete. No reference to the
subject is made by Halbertsma, Harting, Haaxman, or any reliable Dutch
author.

* Cf. Fontenelle (1709). Ornstein (1928) gives the history of the old
Academy (p. 139 sq.) and enumerates the early members (pp. 146, 156, 159).
Christiaan Huygens was the only original foreign member, though several
associate members (including Hartsoeker) were appointed later (1682). In
Godin’s Table Alphabétique the name of L. does not occur, nor is it included
in the elaborate tabulation of De Candolle (1885, p. 224 sq.).

* Letter dated 21 November 1930 (translated).

54 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS

the manuscript record of the proceedings of the meeting held
on 4 March 1699, at which each member ‘nominated his
correspondents’ (correspondant in the etymological sense of
the word). A physician, Burlet, nominated Leeuwenhoek—
‘well known by virtue of what he had been able to observe by
the use of the microscope.’ One may therefore say that
Leeuwenhoek was a ‘correspondant’ of the old Académie des
Sciences: his name also figures in some printed lists. Was he
informed of this officially? No letter of thanks from him is
in existence, nor is there any manuscript of his elsewhere in
our Archives.”

I conclude, therefore, that Leeuwenhoek was “ nominated”
as a “corresponding member”—but never elected a full
Member—of the Académie in 1699, and probably without his
knowledge: for I can find no reference to the subject in any
of his own letters, and there appear to be no extant letters of
his, either published or in manuscript, addressed to Burlet or
to the Academy or to any other member thereof (except
Huygens). In any case, the event was without influence upon
his activities. No scientific society except the Royal Society
enrolled him as a member during his lifetime, though many
have honoured him since his death.’ His name is forever
ae to the Royal Society of London, and to that Society
alone.

As soon as his discoveries became famous, Leeuwenhoek
was visited by all manner of people who wanted to look through
his glasses. The list of celebrities who went to see him is a
long one, and has been drawn up more or less completely and
accurately by various writers.” I need not give it here: for
nobody believes nowadays that scientific truth depends upon
literary or political authority or royal assent. Leeuwenhoek
himself—being a common man—naturally felt flattered when a
King or Queen of England, an Emperor of Germany, or a Tsar
of Russia called upon him. It impressed his fellow-citizens and
advanced his reputation, but he frankly confessed (in one of
his letters to Magliabechi) that he was bored by such interrup-
tions, and preferred to be left in peace to carry on his work.

" Cf. Harting (1876). The statement that L. was a Fellow of “ the Royal
College of Physicians in London” (Nieuwenhuis, 1859) is an error due,
apparently, to confusion of this body with the Royal Society.

* e.g. Halbertsma (1843), Haaxman (1875), etc.

PETER THE GREAT 55

As a sample of the recorded royal visitations I will only
mention the famous interview with Peter the Great—which
took place in 1698, and is noted by all biographers of this
renowned Russian monarch.’ The circumstances were recorded
by van Loon in the following words: ’

The Tsar’s departure from The Hague was made in a
canal-yacht passing by Delft, where he inspected with
very great attention the fine arsenal of the States of
Holland, and caused the boat to be stopped before the
powder-magazine’® of the States-General, nearby Delft:
and he sent two gentlemen of his retinue to the celebrated
Antoni van Leeuwenhoek, to bid him come to see him,
with his incomparable magnifying-glasses, on one of the
freight-ships in his train: and the Tsar would gladly have
gone himself to see him at his own house, had it not been
that he was apprehensive of the crowds, which he desired
to avoid. Leeuwenhoek repaired to His Majesty, and had
the honour of showing him among other remarkable
discoveries, through his particular glasses, the marvellous
circulation in the tail of an eel; which so delighted the
Prince, that in these and other contemplations he spent
no less than two hours, and on taking his leave shook
Leeuwenhoek by the hand, and assured him of his special
gratitude for letting him see such extreme small objects.

Peter I spoke Leeuweuhoek’s language fluently (if not
grammatically)—having picked it up by fraternizing with
Dutch seamen and shipbuilders. He mixed with all classes of
people whilst in Holland and England, and had an insatiate
curiosity to see things for himself. (It is recorded that the
words which fell from his lips most frequently were ‘“ Dat wil

' ¢.g. Barrow (1896), p. 67.

2 Translated from van Loon (1731). This description is trustworthy ;
for van Loon knew L. personally, and may well have heard the story from his
own lips.—On v. Loon see p. 80, note 2, infra.

> After the dreadful explosion of the former magazine inside the town (in
1654), it was rebuilt well outside the walls—in the direction of Rotterdam

(i.e. to the south): so Peter must have passed through Delft before he sent

back to summon L. into his presence. Cf. p. 28 supra.

56 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS”

ik zien”’..) Consequently, we may suppose that his interview
with Leeuwenhoek in the canal-yacht on the outskirts of
Delft was somewhat informal, and more satisfactory both to
the exhibitor and to his audience than some other like meetings
which required the presence of an interpreter. It is probable
that Leeuwenhoek, on this occasion, presented the T’sar with
some of his microscopes*—including his instrument for
examining the circulation in the tail of an eel: for at a later
date some similar apparatus of his manufacture was brought
back to Holland from Russia.’

What manner of man was this “ celebrated Leeuwenhoek ”’ ?
Unfortunately we get little direct information from the writings
of his contemporaries. Kings and princes, philosophers and
physicians and men of science, statesmen and clergymen, and
even common men, went to see him and looked through his
wonderful glasses: but few indeed left any written record of
what they saw, or of their impressions of the man himself.
Nevertheless, there are some extant descriptions of
Leeuwenhoek by people who actually interviewed him, though
only two are of any real importance. One of these is contained
in a manuscript letter written by a young Irish doctor,
Thomas Molyneux, who waited upon him early in 1685 on
behalf of the Royal Society; the other is a lengthier printed
account by one von Uffenbach, a German, who paid him a visit
in 1710 when he was already a very old man. But all the
records are interesting, and I shall therefore give them at
length. Here isthe first—that of Molyneux,’ whose autograph
letter is still preserved by the Royal Society. I give it word
for word, as he wrote it, though I take the liberty of expanding

1 “T want to see that.” Tsar Peter was evidently the father of “ the

man from Missouri.”’
* As he did to our Queen Mary II (ef. p. 317 infra).

° Discovered and recorded by Haaxman (1875), p.35. lL. never sold or
gave away microscopes to ordinary people.

* Thomas Molyneux (1661-1733), physician and zoologist, was brother
of William Molyneux the mathematician and writer on dioptrics. Thomas
was at Trinity College, Dublin, where he took his M.D. degree in 1687. He
became a Fellow of the Royal Society in 1686, President of the College
of Physicians of Ireland in 1702, Professor of Medicine at Dublin University
in 1717, and was madea Baronet in 1730. For further details of his life see
the Dict. Nat. Biogr. (art. by Norman Moore).

T. MOLYNEUX’S VISIT S|

the contractions in the original manuscript for typographical
reasons and for the convenience of the modern reader: '

I have hitherto delay’d answering your last, because I
could not give You any account of Myn Heer Leeuwen-
hoeck, but last week I was to wait uppon him in Your
name: he shew’d me several things through his Micro-
scopes, which ’tis in vain to mention here, since he him-
self has sent You all their descriptions at large. as to
his Microscopes themselves, those which he shew’d me,
in number at least a Dozen, were all of one sort, consisting
only of one smal Glas, ground, (this I mention because ’tis
generaly thought his Microscopes are blown at a Lamp,
those I saw I’m sure were not) placed between two thin
flat Plates of bras, about an Inch broad & an Inch & }
long ; in thees two Plates there were two Apertures one
before, the other behinde the Glas, which were larger or
smaler, as the Glas was more or less convex, or as it
macnify’d; just opposite to thees Apertures on one side was
placed sometimes a Needle, sometimes a slender flat body of
glas or opaque” mater as the occasion requir’d, uppon
which, or to it’s apex, he fixes whatever object he has to
look uppon, then holding it up against the Light by help of
two smal scrues he places it justin the Focus of his glass
and then makes his observations. Sutch were the Micro-
scopes which I saw, and thees are they he shews to the
Curious that come and vizite him, but besides thees he told
me he had an other Sort, which no Man living ever look’d
through setting aside himself, thees he reserves for his own

1 MS.Roy.Soc., No. 2445; M.1.103, dated from Leyden, 13 February
1685 [N.S.]. This letter has been printed previously, with slight inaccuracies
and amended spelling, by Birch (Vol. IV, p. 365). It was addressed to
Francis Aston, then Secretary of the Royal Society, and was read at the
meeting held on.11 February 1685 [0.S.]—not Feb. 4 (an impossible date)
as it appears in Birch, who here wrongly combined the proceedings of two
different meetings.

> In translating this letter—from Birch—Haaxman has made a slip.
He renders “ opaque” as “ doorschijnende ’’—instead of ondoorschijnende, as
he should have done. See Haaxman (1875), p.13, lin. penult.

58

——

1

2

sé

LEEUWENHOEK AND HIS “LITTLE ANIMALS”

private Observations wholy, and he assur’d me they per-
form’d far beyond any that he had shew’d me yet, but
would not allow me a sight of them, so all I can do, is
barely to belive, for I can plead no experience in the mater.
as for the Microscopes I looked through, they do not
magnify, mutch, if any thing, more, then several Glasses I
have seen both in England & Ireland: but in one
particular I must needs say they far surpas them all,
that is in their extreme clearness, and their representing
all objects so extrordnary distinctly. for I remember
we were in a dark rome’ with only one Window, and the
sun to, was then of a that,’ yet the Objects appeerd more
fair and clear, then any I have seen through Micro-
scopes, tho the Sun shone full uppon them, or tho they
receved more then ordnary Light by help of reflectiv
Specula or otherwise: so that I imagine tis chiefly, if not
allone in this particular, that his Glasses exceeds all
others, which generaly the more they magnify the more
obscure they represent the Object; and his only secret
I belive is making clearer Glasses, and giving them a
better pollish then others can do. I found him a very
civil complesant man, & douptless of great natural
Abileties; but contrary to my Expectations quite a
stranger to letters, master neither of Latin French or
English or any other of the modern tongues besides his
own, which is a great hindrance to him in his reasonings
uppon his Observations, for being ignorant of all other
Mens thoughts, he is wholy trusting to his own, which
I observe now and then lead him into extravagances,
and suggest very odd accounts of things, nay sometimes
sutch as are wholy irreconsilable with all truth. You
see Sir how freely I give You my thoughts of him
because You desired it.

2.€., room. :
“of a that’? = off of that, i.e. off the window—not on, or shining

through it.

W. MOLYNEUX 59

A little later Molyneux wrote again to the Society, and
gave a few further particulars—evidently in reply to a request
for additional information. From this letter, dated from
Leyden, 16 March 1685, I extract the following’:

The Glasses Mr Lewenhoeck shew’d me magnified
Objects no more then several other glasses I have seen
before, & therefore discover nothing but what may easily
be seen by help of other Microscopes, so an account of
them would be no ways satisfactory; ’tis only his owne
privat Glasses which make those more then ordnary
discoverys. I never heard he sold those glasses of his
more common sort; but I sha’nt returne suddenly into
England, for I designe, to have stayd some while in
France, & perhaps visite Italy before that time, so I
ca’nt serve You in this particular.”

When Thomas Molyneux visited Leeuwenhoek in 1685 he
was probably accompanied by his elder brother William S10
the latter has left a record of a similar visit—buried in a book
on optics, and consequently not generally known—which
affords some confirmation of the foregoing account. William
Molyneux’s words are as follows *:

The Heer Lewenhoeck of Delft in Holland, had lately
apply’d himself with great Diligence to the use of
Microscopes: of which Instrument he thinks he has a
better kind than was ever yet known. When I visited

ee

1 MS.Roy.Soc., No. 2446, M.1.104. Printed by Birch, Vol. IV, p. 384.
The letter was read at the meeting of the Royal Society on 1 April 1685
[O.8.]. I expand the contractions again, but otherwise give the exact words
of the original.

2 T take it that “this particular’ was a request to Molyneux that he
should endeavour to buy some of L.’s glasses for the Society.

§ William Molyneux (1656-1698). He was B.A. of Trinity College,
Dublin, and a “ philosopher” and mathematician. Elected F.R.S. in 1686—
the same year as his brother (though owing to the confusion of “old style”
and ‘‘ new style” dating, apparently a year earlier) : entered Middle Temple,
1675: M.P. for Dublin University, 1692 and 1695. For his life see the
Dict. Nat. Biogr. (in which the dates of election to the Roy. Soc. are given
wrongly for both brothers).

“ W. Molyneux (1692), p. 281.

ce

60 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

this Gentleman at Delft, he shew’d me several that indeed
were very curious; but nothing more than what I had
ordinarily seen before; being composed only of one single,
very minute Glass-Sphere or Hemisphere,’ placed between
two very thin pierced Laminae, or Plates of Brass, and
the Object was brought to its due distance before the
Glass by a fine Screw: But for his best sort, he beg’d our
Excuse in concealing them. The Observations he has
made with his Glasses are Printed in several Letters of
his in Dutch ; but for the most part, they are to be found
dispers’d in the Philosophical Transactions.

There is a more illuminating reference to Leeuwenhoek in
a letter written by Constantijn Huygens jun. to his brother
Christiaan in the year of Molyneux’s visit: and as it illus-
trates Leeuwenhoek’s extraordinary jealousy in guarding his
microscopes, is may be quoted here. Constantijn junior, in
this epistle, tells his brother that he has just seen one Willem
Meester * (a skilled Dutch mechanic), who had recently been
with the Landgrave of Hesse* to interview Leeuwenhoek.
Says Constantijn : *

He [Meester] had been with him [the Landgrave] to
Leeuwenhoek’s, who wouldn’t show him any of his
microscopes except those which he shows to everybody ;
whereof the little glasses had, at least, a focal distance
equal to the width of the back of a knife. And when the
Landgrave had asked him whether he could obtain some,
of his manufacture, he answered with much pride that he

* This is an error: for L.’s glasses were neither spherical nor hemi-
spherical, but ground biconvex lenses—as Thomas Molyneux correctly
observed.

* There are many other references to Meester in the Huygens corre-
spondence. He appears to have accompanied the Prince of Orange in his
campaigns. Cf. Huvr. Compl. de Chr. Huygens, Vol. VII, p. 439 note.

* Karl, Landgrave of Hesse-Cassel (1654-1730), an amateur of science.

* Printed in @uvr. Compl. de Chr. Huygens, Vol. 1X, p.38, No. 2408.
5 Nov. 1685. The original MS. is in the Leyden Library, and is in
French—from which I translate. Constantijn Huygens jun. (1628-1697)
was elder brother of Christiaan (1629-1695), both being sons of Constantijn
sen. (1596-1687).

THE REV. J. DE LA CROSE 61

never gave any to anybody, nor did he intend to do so:
and that if he were ever to submit to that, he would then
soon be the slave of everybody; with other expressions of
the like sort. When he had shown two or three of his
microscopes, he took them away, and went to look for as
many others; saying that he did this for fear lest any of
them might get mislaid among the beholders, because he
didn’t trust people, especially Germans: and he repeated
this two or three times. O what a brute!’

Another person who has left a brief contemporary account of
Leeuwenhoek and his microscopes—professedly from personal
knowledge—is the Rev. Jean Cornand de la Crose. This
gentleman was a French protestant refugee, who fled to
Holland after the revocation of the Edict of Nantes and later
settled in England, where he was received into the Anglican
Church.” In the year 1693 he published in London a curious
monthly magazine* in imitation of the Philosophical Trans-
actions: and in its May number he presented his readers with
an English translation* (neither complete nor accurate,
though written in a language which gives no cause for
complaint) of Leeuwenhoek’s famous letter’ on the capillary
circulation of the blood —the first version to appear in English.
At the end of this he added :”

Mr. Leeuwenhoek being so deservedly famous in the
learned World, the Ingenious will undoubtedly be glad to

* These final words are in Italian in the original. Cf. note 3 on p. 50.

? But little is now known of de la Crose (alias Croze seu Lacroze). His
own Memoirs etc. supply some information regarding his career, however, and
a few further details may be found in Agnew (1886), Vol. II, p. 270, and the
Nouv. Biogr. Gén. (Hoefer), Vol. XXVIII [s.v. Lacroze] .

* Memoirs for the Ingenious [etc.]. 1698. This work is now extremely
rare. Only one volume appeared: and an attempted continuation (The
Universal Mercury) expired with its first number in January, 1694.

* Ibid., Letter XIX, p. 145.

° Letter 65. Tothe Royal Society. 7 Sept. 1688. Published (complete)
in Dutch and Latin works: not in Phil. Trans. A full modern English
translation (with Dutch original reprinted) will be found in Opuscula
Selecta Neerlandicorum, Vol.1I, p.38 (Amsterdam, 1907), and a mutilated
bit of this in Fulton (1930).

° Mem. Ing., p. 152.

62

LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS”’

have an account of him. He is about 50 years of age,’ but
has already imployed 15 or 20 years in Observations as
curious as these, which I have here related. His Parents
designed him for a Chyrurgeon, which Profession he has
exercised some time with Honor.’ And as he rightly
conceived, that Anatomy was the foundation of that
useful Art, and that Microscopes were highly serviceable
to acquire the knowledge of it, he applied himself not only
to perfect those that were already in use, but even to
invent new ones, in which he has succeeded to admiration,
having discovered amongst other things more kinds of
invisible Animals, than the World before him knew there
were visible ones: and withal made an anatomical descrip-
tion of many of them. The perfection to which he has
brought his Microscopes, has atforded him great light.
For they are not big and cumbersom tools, as the ordinary
ones ; but light and portable, consisting only of a glass
or two at the end of a small and short tube,’ so that he
may manage them, and apply them to the object, as easily
as his own Hyes. And what is still more wonderful is,
That tho his Glasses magnify the Objects far beyond any
I have seen, yet they do not darken it.* To which if it
be added, that he is an able Surgeon, and has made it his
chief business during many years to dissect and view little
Animals, Plants, Seeds, Eggs, Saps, and the like, his
surprizing discoveries will become more credible. I know
some are apt to imagine, that this curious Observer of
Nature imposes at least upon himself, in several things

* In May 1693 L. was, of course, in his 61st year. Perhaps de la Crose

was reporting his recollection of the time when he was himself resident in
Holland.

* This is an extraordinary mistake: but no more remarkable or inex-

plicable than that made by one of L.’s own distinguished modern fellow-
countrymen (de Groot, 1910), who calls our hero “ physicist and surgeon of
Haarlem”! (ef. p. 352 infra).

An evident error.

* These words confirm what T. Molyneux wrote in 1685. Cf. p. 58

supra.

UFFENBACH 63

which appear to them undiscernible. But as to the
matter of fact he relates, I dare answer for his sincerity,
having myself tried his Microscopes, viewed several things
through them, and found them conformable to his relations.
Besides, he is very free to let Objects be viewed through
his Glasses, and to communicate his Observations to
Gentlemen of Learning and Credit, especially Travellers:
but he has made so many of them at all seasons and times
of the year, that the Thousandth part cannot be examined
by those that repair to him on that account. ‘There is a
Volume of his Observations printed in Latin, some of
which are inserted in the Philosophical Transactions, and
I have by me some other’ very curious, which I shall
publish in due time.’

The last important contemporary record is Uffenbach’s®
well-known account of his visit to Leeuwenhoek in 1710. It is
entertaining enough; but chiefly because of the fatuous com-
ments of this complacent German diarist, who was so satisfied
of his own superiority that he would be horrified if he could
hear that his condescending notes on our poor Dutch draper
are now the chief thing of interest in his tedious memoirs.
This is what he wrote: *

On the 4th December [1710] we’ went in the morning

* From other references, it appears that de la Crose possessed a copy of
the Dutch edition of L.’s letters of that period.

* A few further observations on the circulation of the blood were published
by de la Crose, but nothing else.

* Zacharias Conrad von Uffenbach (1683-1734) was a German jurist,
town-councillor of Frankfort, and a keen collector of books, coins, and
“curiosities”. His Travels were published posthumously in 1753-54 (ed.
Schelhorn), and much of his insignificant correspondence has also appeared
in print. His life is prefixed to his memoirs, and will also be found in the
Allg. Dtsch. Biogr.

* Translated from the German of Uffenbach (1754), Vol. ITT, pp. 349-360,
with immaterial omissions which are duly indicated. The full description
is too long-winded to give here in its entirety. In my translation I have
left the Latin words as Uffenbach gave them, in order to preserve his
pedantic style of expression. His mistakes are too evident for comment.

° “We” apparently denotes Uffenbach and his brother.

64

ce

LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS ”’

to see the famous observator microscopicus, Leeuwenhoek,’
by whom . . . we were most courteously received.
The only daughter that he has, a person of about forty,”
led us first into an antechamber, and told us that her
father, though he had discovered many new things with
his microscopia in recent years, did not wish to publish
any more of his observations during his lifetime, because
of the affronts he had suffered, presumably in the writings
of others ; for he has now and then been ridiculed for the
odd views expressed in his own writings, and has been
accused of seeing more with his imagination than with
his magnifying glasses. Mr. Leeuwenhoek is a man of
seventy-eight, but still hale and hearty, save that he
cannot much use his feet. We were surprised to find him
not at all shaky, and he still has almost incomparable
eyesight, though he taxes his eyes greatly with his
observations. He showed us the following experiments :
First, the circulation of the blood, very fine and clear, in
the tail of a quite little flounder (which is one of the
greatest delicacies among sea-fish). He was not only of
opinion that where the blood runs upwards, these are the
arteries, and where it runs downwards, the venae (of
which I justly doubted whether such a sweeping assump-
tion were allowable?), but also he maintained that
it is the venae and not the artervae which pulsate.
He also insisted that he could see with the naked
eye that the pulse at the wrist beats downwards
rather than upwards. Methinks, however, that herein
Mr. Leeuwenhoek does but show his ignorance of
anatomy; for the structure of the arteries sufficiently
proves that the valvulae in them undoubtedly cause the
pulse-beat, whereas the blood merely flows along and

‘ His name is spelled “ Leuwenhoeck” by Uffenbach throughout—a

mistake which I have taken the liberty of correcting wherever it occurs in
his narrative.

* Maria was really aged 54 at this time; and consequently Uffenbach’s

statement is an unintentional compliment on her personal appearance.

UFFENBACH’S INTERVIEW 65

through the venae, which have no valvulae. Besides, it
is surely impossible to distinguish whether the pulse at
the wrist beats downwards or upwards? But this by
the way.—Mr. Leeuwenhoek then cut off with a knife a
small bit from a mussel,’ such as they are here wont to
eat, and showed us that all its parts were in a continuous
motion ; just as a snake apparently continues to move
itself for a long time when freshly hacked to pieces with
a switch. In both cases this is due to the vital spirits,
which seek to escape, and so bring about the movements.
Afterwards Mr. Leeuwenhoek cut a mussel in two through
the middle, in order to show us how the eggs and young
mussels are generated. He also showed us certain black
dots, which he maintained were young mussels in their
black shells; but we couldn't take them for such, being
unable to distinguish them. He also cut the gut of a
mussel in two, and showed us, by means of his micro-
scopium, a great mass of sand in it, which the mussels
presumably take in with the slime in which they live.
Mr. Leeuwenhoek considered, and not unjustly, that this
sand serves for the formation of the shells of their young
ones, just as hens and other birds readily eat sand and
lime for the sake of their egg-shells. He wished also to
show us the circulation of the blood in an eel, only the
creature was too big and black. Mr. Leeuwenhoek makes
this experiment with an instrument which . . . is
simple, large, and not at all convenient. The one made
by Mez in Amsterdam, with a camera obscura, is better ;
with this one you are dazzled by the light and the glass.

Mr. Leeuwenhoek showed us the circulation of
fee blood very well with this machine, though it was
somewhat troublesome to manipulate, and would be even
worse for making observations lasting over a long time,
because you have to put the side of the mcroscopwwm,
where the lens is, against your forehead, and look

1 No doubt L. showed the ciliary motion on a portion of the gill of
Mytilus—as he well knew how.

5

66

LEEUWENHOEK AND HIS “LITTLE ANIMALS”’

upwards through the tiny glass; which, after some time,
would become tiresome. Mr. Leeuwenhoek afterwards
fetched some cases, in each of which were two
microscopia’ . . . likewise of quite a simple structure.

Each of these microscopia had a_ particular
curiosity stuck before it; but we saw the following:
First, in tubulo capillari, upwards of thirty small young
oysters 7m spiritu vint. These could be seen quite clearly,
and had the perfect form and structure of old and big
oysters. . . . We inquired how he introduced these
young oysters into his capillary tubes, which he
explained in the following fashion: He cuts off the
gut of an oyster, takes some of the stuff that is in it
on a pen-knife, and smears it on his thumb-nail; he
then pours a drop of spirits of wine upon it, and applies
the capillary tube thereto, whereupon the spirit runs up
the tube of itself, through the pressure of the air, and
takes the little oysters along with it, they being commonly
present in the substance that is in the beard or the gut
of the old oysters. He uses spirit for this purpose in
order that they may not so easily become foul, which,
being fish, they only too readily do, as happened indeed
formerly with him, when he used only water. This ex-
periment is one of the finest and most curious that we
saw at Mr. Leeuwenhoek’s. He showed us further a
“maggot”, as they are called, supposed to grow in the
port of the nose. . . . Through another microscopium he
showed us a sand-grain, which looked like the finest
crystal with facettes. ... In another microscopium he
had, on a bit of glass, a particle of gold, which he had
previously dissolved in aqua regia and then precipitated :
this appeared just like a little gold tree, and exceeding
pretty. . . . Next, Mr. Leeuwenhoek showed us, through
another microscopiwm, the scale of a fish, whose structure

* These may have been the silver instruments bequeathed to the Royal

Society. Cf. p. 96 wnfra.

EXTRAORDINARY NOTIONS (UFFENBACH) 67

was certainly wonderful. . . . At this point Mr. Leeuwen-
hoek remarked that he must show us that men also have
scales. Accordingly, he took a pen-knife, and scratched
his arm several times; then took a glass tube and with it
scraped several times the place that he had scratched.
He then let us look at this tube through his mzcroscopiwm,
whereupon many little particles, like scales, were visible
lying upon it. These the good man takes to be scales,
which a human being is provided with in order that the
extremities of the nerves may not be injured, as also to
prevent his sensations being too strong ; for if the nerves
were not so guarded, he would be unable to stand pain, or
irritation, nor could he do any work. It is surely quite
sufficient, however, that man is clothed with several skins,
as is known from anatomy, and he has no need of scales
like a fish: and what the good Mr. Leeuwenhoek takes for
scales are really only the particles, or scurf, from the outer-
most skin, which are commonly present, especially in per-
sons of adry habit, and particularly on the head, and which
are cast off from the cuticwla as it dries up and peels off
under the influence of the external air, but chiefly through
the internal heat of the body, though it always forms
anew underneath. Mr. Leeuwenhoek showed us further
the eye of a fly, which appeared very remarkable under
the microscopium, and had the appearance of veritable
hexagona lying alongside one another; which Mr.
Leeuwenhoek considers actually are eyes, and consequently
makes flies into something better than so many Arguses ;
for he is of opinion that a fly, according to his view, has
more than a hundred, nay, more than a thousand, eyes ;
which is only one of this good man’s extraordinary notions,
which seem wont to have more of ingenuity than founda-
tion. Further, he showed us the wing of a fly, which also
appeared very wonderful . . . The sting of a fly appeared
also very singular .. . Finally, Mr. Leeuwenhoek showed
us his cabinet, in which he had at least a dozen little
lacquered boxes, and in these quite a hundred and fifty of
the little cases before mentioned, in each of which there

68

LEEUWENHOEK AND HIS “LITTLE ANIMALS”’

lay two microscopes of the small sort. As we marvelled
at this large store, we asked him whether he never sold
any? as we would gladly have possessed ourselves of
some: but he said no, he would sell none in his lifetime.
He was also very secret about his work, and how he did
it: but we drew one thing and another out of him with
all manner of questions. Thus, when we asked him
whether all these mzcroscopia were identical? he said
they were all ground in the same grinding-cup, but
nevertheless there was a difference between the various
lenses, and as regards those ground last in any cup,
indeed, a great difference..... When we further
inquired of Mr. Leeuwenhoek whether he ground all his
lenses, and did not blow any? he denied this, but
displayed great contempt for the blown glasses. He
pointed out to us how thin his microscopia were, com-
pared with others, and how close together the laminae
were between which the lens lay, so that no spherical
glass could be thus mounted ; all his lenses being ground,
contrariwise, convex on both sides. He also had some
microscopia with double glasses, which, though they were
double, and the lenses separated inside at their proper
distance, presumably by another lamina, were nevertheless
not much thicker than the simple ones. Notwithstanding
that these are pretty troublesome to make, they yet are
not much better than the simple ones, excepting that
they magnify a little more; but only a little, as Mr.
Leeuwenhoek himself confessed. As regards the blown
glasses, Mr. Leeuwenhoek assured us that he had
succeeded, after ten years’ speculation, in learning how
to blow a serviceable kind of glasses which were not
round. My brother was unwilling to believe this, but took
it for a Dutch joke*; since it is impossible, by blowing,
to form anything but a sphere, or rounded end. Yet one
cannot sufficiently marvel at Mr. Leeuwenhoek’s great

' A pleasing German expression for a falsehood.

EXPLICIT UFFENBACHIUS. HARTSOEKER 69

diligence and industry, both in the making of observations
and in the grinding of lenses, as also in the manufacture
of the mechanical parts for his microscopia; albeit the
latter are simple, and badly worked, and for the most
part roughly fashioned, even the silver not being filed
smooth in a single one of them. We much wanted to ask
him why he made so many microscopia, though he would
not sell any ; but we feared we might get only a Dutch
answer.. Presumably jealousy lest anybody should get
hold of microscopes of his pattern, during his lifetime, is
chiefly at the bottom of this; but there is also some self-
interest, in that his daughter will one day be able to sell
them so much dearer, if they cannot be got during his
own lifetime.” As we were going, both this extraordinary
man and his daughter earnestly intreated us to tell no
one that we had been to see him, or seen anything
there; for the reason that he is old, and tired of being
pestered, especially by people who are not true lovers of
learning. .... We were told not only in Delft, but also
by many foreigners who had waited upon him in vain,
that he would see no one, still less show people anything :
and we were therefore greatly rejoiced that we saw so
many curious things at the house of this extraordinary
old man.
One final account of Leeuwenhoek by a man who met
him must, unfortunately, be mentioned. It was given by
Hartsoeker,’ an envious fellow-countryman, and was obviously

*7.e. none: another German pleasantry.

* As a comment on this unjust remark, it may be recalled that L.’s
microscopes were not put up for sale until 1747—two years after Maria’s
death. Cf. p. 320.

* Nicolaas Hartsoeker (1656-1725), physicist, astronomer, and mathe-
matician: son of Christiaan Hartsoeker (1626-1683), a minister of the
reformed Church. He had a variegated career, which is recorded in Dict.
Sct. méd. (1822), V, 85; N. Ned. Biogr. Woordenb. (1924), VI, 718; and
elsewhere. In Cwvres Compl. de Chr. Huygens (VIII, 58n) it is stated that
Hartsoeker was born on 25 March 1654: but this is contradicted by his own
statement in the Hzt. crit. (1730), p. 43, where he himself gives the date as
26 March 1656.

70 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

inspired by dislike and jealousy. I shall not quote his
words, as they have already been repeated by Haaxman
(1875) and others, and are not worthy of further consideration.
It is now abundantly evident that Hartsoeker had wronged
Leeuwenhoek, and therefore hated him; while on his side
Leeuwenhoek despised Hartsoeker and treated him with
contempt. All this can be read in their various references
to one another.” When he was very young, Hartsoeker—who
had visited Leeuwenhoek with his father, and had been
shown or had heard of the discovery of the spermatozoa—
went to Paris, and there tried to palm off this discovery as
his own. He did not succeed—though there are still
credulous or ignorant writers who accept his claims *—and
when the facts became known he was reduced to silence.
More than forty years later, when Leeuwenhoek had at last
died, Hartsoeker attempted to blacken his character and
reasserted his own priority *: but he himself died before his
malicious remarks were published (1730), so that he was
denied the final satisfaction of kicking Leeuwenhoek’s corpse
in public. Hartsoeker was a man of undoubted ability, but
quarrelsome and arrogant and in every way the very
antithesis of Leeuwenhoek. He attacked and found fault
with everybody he envied—not only Leeuwenhoek, but also
Newton, Leibniz, and even Christiaan Huygens (who had
befriended him)—and his foolish criticisms and _ personal
complaints are now best consigned to the oblivion which
they deserve. On his own confession he was virtually
turned out of the house by Leeuwenhoek when he last
attempted, by a subterfuge, to visit him. I _ shall
therefore treat Hartsoeker likewise here,’ and give him

"See Hartsoeker (1730), Extrait critique, passim.

* See L.’s letters and Hartsoeker’s publications passim: also Cuvres
Compl. de Chr. Huygens—especially Vol. VIII.

* Cf. Martin (1764), Launois (1904), ete.

“ Hartsoeker’s claims to the discovery of the spermatozoa have recently
been critically considered and correctly assessed by Cole (1930).

° I must add, however, that I have carefully and impartially read all the
available evidence concerning Hartsoeker’s relations with L. Consequently
I am well aware that much already written on this subject is incorrect,
though it seems to me unnecessary to discuss all the data here. French
writers especially—doubtless influenced by Fontenelle—have, in general,

HARTSOEKER. AUTOBIOGRAPHY [a

no further publicity. Leeuwenhoek’s own last comment
on him was’:

It has come to my ears that Hartsoeker hasn’t much
of a reputation among the learned: and when I saw that
he laid claim to untruths, and was stuck-up, I looked
into his writings no further.

The foregoing quotations show what some of Leeuwenhoek’s
contemporaries thought about him: but the best description
of himself is that unconsciously written by his own hand. His
own letters are filled with autobiography. On almost every
page he tells us of his thoughts, his feelings, his everyday
actions: so that we can now form a very clear and probably
correct picture of his personality. But it was all done quite
naturally and ingenuously; for he had no thought, when he
was writing, that be was often revealing himself rather than
some ‘“‘mystery of nature”. He sets down his views—
frequently quite mistaken and even ridiculous views—with
childish and charming simplicity, and he has no feeling of
embarrassment in telling the Royal Society the most intimate
details about his blood, his sweat, or his urine; or about his
sicknesses or his habits or his little vanities: because he
always imagines that he is recording matters of scientific
interest, and he knows by instinct that in registering his
observations he ought not to withhold any data which may
possibly have a bearing upon his findings. Yet he always
presents his results in a way which, despite the imperfections
of his language and his lack of scientific education, is a model
for all other workers. He never confuses his facts with his
speculations. When recording facts he invariably says “I
have observed . . .”, but when giving his interpretations he
prefaces them with “but I imagine...” or “I figure to
myself...” Few scientific workers—or so it seems to me—
have had so clear a conception of the boundary between
observation and theory, fact and fancy, the concrete and the
abstract.

given Hartsoeker far more credit than he deserves: Dutch writers are better
informed. (Fontenelle’s Hloge of Hartsoeker will be found reprinted at the
beginning of the latter's posthumous Cowrs de Physique, 1730.)

' Send-brief XVIII, 28 Sept. 1715, to Leibniz (Brieven, Vol. IV, p. 170).

72 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS”

But every reader of Leeuwenhoek’s letters must form his
own opinion of the man himself. Some have been—and will
be—revolted by his “‘grossness” and “ vulgarity”: others
will continue to delight in his very “ commonness”’, and will
even find in it something meritorious. For my own part, I
confess that I enjoy his most commonplace sayings, because
they satisfy my own craving for simplicity and common sense
in all things—especially in those called “scientific”. When
Leeuwenhoek makes casual “asides”? about the most trivial
affairs of his life, it does not offend me: it rather helps me to
understand him. I like to hear that he generally drank coffee
for breakfast and took tea in the afternoon, or that he shaved
himself twice a week and got a rash on his hands when he sat
in the sun: and I even laughed uproariously when I first read
the letter in which he gravely told the Royal Society—
evidently giving it as a tip to the Fellows—that he found it
advisable to drink a great many cups of extremely hot tea on
rising if he had had a drop of wine too much the night before
with a friend. But when he speaks of his little white long-
haired pet dog, or of his parrot “ which is moulting,” or of his
horse “‘ which is a mare”’, or incidentally remarks that he was
wont to throw bread to the sparrows when the snow was on
the ground, I feel that I really know the sort of man he was.
Little touches such as these bring the heavy-featured blue-
eyed Hollander of Verkolje’s painting very vividly before my
mind's eye, and explain—in an inexplicable and inexpressible
manner—his crude but inspired discoveries in protozoology
and bacteriology. They make me want to find excuses for all
his many mistakes. It is so obviously his works—not his
words—which count. I do not suppose that he ever read any
writings of his great contemporary John Bunyan: but had he
done so he would certainly have understood what Bunyan
meant when he wrote: ‘‘ Yea, if a man have all knowledge, he
may yet be nothing, and so consequently be no child of God.
When Christ said, Do you know all these things? And the
Disciples had answered, Yes: He addeth, Blessed are ye if ye
do them.” *

* John Bunyan (1628-1688), the immortal English tinker. I quote
from the first edition of the Pilgrim’s Progress (1678), p. 113—written in
Bedford jail.

LEEUWENHOEK THE MAN i3

Our Leeuwenhoek was manifestly a man of great and
singular candour, honesty, and sincerity. He was religiously
plain and straightforward in all he did, and therefore sometimes
almost immodestly frank in describing his observations. It
never occurred to him that Truth could appear indecent.
His letters, accordingly, are full of outspoken thoughts which
more “scientific ” writers would hesitate to put on paper: and
to the modern reader this is, indeed, one of his particular
charms—for he is far more childlike and innocent and
“modern” than any present-day writer. In his own similar
language he must often have said the beautiful prayer of
Thomas More: “‘ Our Lorde kepe me continuallye true faithfull
and playne, to the contrarye whereof I beseche hym hartelye
never to suffer me live.’’*

But Leeuwenhoek—like all honest workmen—took a pride
in his work. He jealously guarded what he believed to be
true, though always willing to change his opinions when
cogent arguments were advanced against them. All studious
readers of his letters will be able to call to mind a score or
more of places where he confesses his scientific faith. It is
impossible to quote all these passages here, but a few extracts—
taken at random—will illustrate this aspect of his personality.
Writing to the Royal Society in 1692 he says’:

I well know, Most Noble Sirs, that the propositions I
come to make, and which I’ve sent you from time to time,
do not all agree with one another, but contradictions are
to be found among them: so I will only say once more
that ‘tis my habit to hold fast to my notions only until
I’m better informed, or till my observations make me go
over to others: and I’ll never be ashamed thus to chop
and change.

ee ee

™ Tn one of Sir Thomas More’s letters written in prison to his daughter
Margaret. See More’s Utopia ete., ed. Sampson (1910) p.281. More was
born in 1478 and beheaded on 6 July 1535. His Utopia was first published
at Louvain in 1516. It is unlikely that L. had ever read it, though the
first Dutch translation appeared in 1653.

2 Letter 74, 12 August 1692. MS.Roy.Soc. Cf. Brieven, Derde Vervolg,
p- 507. Not published in Phil. Trans.

74 LEEUWENHOEK AND HIS “LITTLE ANIMALS”

A little later, in a letter to the Rev. George Garden’ he
wrote °:

I must say to you, as I’ve oft-times said already, that
‘tis not my intention to stick stubbornly to my opinions,
but as soon as people urge against them any reasonable
objections, whereof I can form a just idea, I’ll give mine
up, and go over to the other side: and especially because
my efforts are ever striving towards no other end than,
as far as in me lieth, to set the Truth before my eyes, to
embrace it, and to lay out to good account the small
Talent that I’ve received*: in order to draw the World
away from its Old-Heathenish superstition, to go over to
the Truth, and to cleave unto it.

The following characteristic passages * are all from the last
published series of Letters—the Send-brieven, written by
Leeuwenhoek to various people at various dates :

I have said before now, that, if ever I came to err in
my discoveries, I would make open-hearted confession
thereof.’

In the observations aforesaid I have spent a lot more
time than many people would believe: yet I made them
with pleasure, and paid no attention to people who say to
me ‘‘ Why take so much pains?” and ‘“‘ What’s the use

* George Garden (1649-1733), a Scottish divine, and minister at
Aberdeen till 1701—when he was deposed for writing an “ Apology’’ for
Antoinette Bourignon, the religious fanatic who assisted in Swammerdam’s
downfall. Garden was not a Fellow of the Royal Society.

* Quoted in Letter 81, to the Royal Society. 19 March 1694. Cf.
Brieven, 4de Vervolg, p.671-2. There is no extant MS. of this letter,
which was sent to the Society by L. in the form of a printed proof-sheet
and was not published in the Phil. Trans.

* The reference is obviously to Matth. XXV, 25 sq.—the parable of the
talents. Li. does not here use the biblical words, but his own have a strong
flavour of the Bible—as was only meet, in writing to a clergyman.

* I translate from the Dutch versions, as nearly as I can: for the flavour
of the originals is almost wholly lost in the more formal Latin translations.

> Send-brief II, p. 16.

ARTICLES OF FAITH 75

of it ?’’ because I don't write for such folks, but only for
Philosophers.’

Hereupon I must remark that it don’t seem strange to
me that there are still some who won’t accept of my
propositions regarding generation : for novelties oft-times
aren’t accepted, because men are apt to hold fast by
what their Teachers have impressed on ’em.”

A certain very understanding Gentleman in our Town,
who had been reading my printed Letters, said to me:
“Teeuwenhoek, you’ve got the truth, but it won't be
received in your lifetime”. And therefore it doesn’t
strike me as odd, that I meet with contradictions during
my life.”

Yet how the Tuba Fallopiana can perform any kind of
sucking is to me inconceivable: and though I must confess
I’ve often heard Doctors and Physicians talk about
things that seem to me to have no rhyme or reason, yet
of nothing worse than generation by an egestock and
the Fallopian tube. ‘I'would have been better if they'd
said “it’s a secret quality”: for of course it would have
been too silly for learned people just to say “we don’t
know ’’.*

I see well that I can’t bring many learned gentlemen
to believe in my true discoveries and also in my proposi-
tions: but herein I find more to comfort me than for

Be EEE ee

' Send-brief II, p. 22.

? Send-brief XVIII, p. 166.
® Send-brief XVIII, p. 168.
* Send-brief XXIII, p. 211.

76 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

quarrel, if I have but the luck (as I have) that many great
men also do accept of my discoveries.’

I’m well aware that these my writings will not be
accepted by some, as they judge it to be impossible to
make such discoveries: but I don’t bother about such
contradictions. Among the ignorant, they’re still saying
about me that I’m a conjuror, and that I show people
what don’t exist: but they’re to be forgiven, they know
no better.”

I well know there are whole Universities that won’t
believe there are living creatures in the male seed : but
such things don’t worry me, I know I’m in the right.’

These sayings are typical of Leeuwenhoek, though they
are but random samples: I will not rob his readers of the
pleasure of finding for themselves many another equally good.
Almost every letter he ever wrote contains some remark
which throws light upon his character—especially his last
letters, written when he was very old. ‘These, as might be
expected, are crammed with the reminiscences of a lifetime
spent in the solitary contemplation and interrogation of
Nature. All his long life he kept on asking questions of
Nature—whose own favourite child he was—in common
colloquial old-fashioned Dutch, and trying in his simple way
to understand her answers made in a pure and perfect language
which we still cannot interpret correctly. But it is for the
poet—not for the scientist or historian—to portray our Child
of Nature in communion with his Mother. I cannot even
attempt the task, and must now merely chronicle the last
chapters in a prosaic life packed with the stuff of scientific
and artistic dreams.

In 1707, when he was in his 75th year, the Royal Society
sent to ask after Leeuwenhoek’s health—being anxious because

" Send-brief XXX, p. 304.
* Send-brief XXXII, p. 317.
* Send-brief XLI, p. 405.

PLATE XII

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LEEUWENHOEK IN 1707, AGED 75 YEARS

Enlarged from a miniature portrait by J. Goeree (1670-1731), inset in the
engraved title-page of the last volume of the Letters (1718).

facing p. 76

eat
ra aiw isis juli

ath ae 7 ne

Pe reece rit eng uf
re YTS (Hin ry :
_ re
wut ; ‘
pines

1?

VISITS IN OLD AGE ea

they had received no letters from him for nearly a twelvemonth.
(He had evidently ceased to write merely because the Society
had not acknowledged his three previous communications.)
To their inquiries he returned the following reply, addressed
to John Chamberlayne’:

I received your acceptable Letter of the 20th of March,
deliver’d by your Nephew the 29th of April last, wherein
you are pleased to say, that the Honble. Royal Society
are very much concerned that they have had no account
of my health for a great while, and that you had com-
manded your Nephew to wait upon me and desired me to
let you know how I did.

Your Nephew delivered your Letter to my Daughter,
but I was not at home, and since that time I never saw
him again. I am thankfull for your Civilities.

As to my health, thanks be to God, as long as I sit still
I am without any pain, but if I do but walk a little I have
pains in my leggs,” but that is, I think, caused by former
colds and because they have carried my body so long.

In other letters of this period we hear of various other
visits paid to Leeuwenhoek in his old age by Fellows of the
Royal Society and other people. Most of these visitors—
notwithstanding Uffenbach’s statement *—seem to have been
kindly received, and entertained with divers microscopical
sights (especially the capillary circulation in the tail of a little
eel). His reasons for refusing to see people occasionally were
given by himself; and in this connexion the following un-
published passages from two otherwise published letters are

* From Letter dated 17 May 1707. To J. Chamberlayne, F.R.S. MS.
Roy. Soc. Unpublished. This interesting letter is peculiar in that the
original is in English. As no Dutch or Latin version accompanies it, and
as it is apparently written on L.’s own gilt-edged letter-paper (such as he
used at that time), I infer that the translation was made in Delft, by a
friend, and that the letter was sent in the form in which it now survives.
I transcribe the words of the MS. exactly, merely expanding a few
contractions in the original.—F'or Chamberlayne, see p. 270, note 2, infra.

" Cf. Uffenbach’s statement, p. 64 supra.
* Cf. p. 69 supra.

78 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

worth quoting. Writing to the Royal Society early in 1710
Leeuwenhoek remarks ’*:

I have received by the hands of Mr Stuart’ the six
several T'ransactions, for which gift I am most deeply
thankful, and wish I had the ability to do the Honourable
Society some service in return.

Mr Hans Sloane * recommended Mr Stuart to me, in his
letter, as a curious Gentleman who has travelled through
many countries ; and the same Gentleman had two other
Scottish gentlemen in his company, all of whom I gladly
received, and so will I do all those who have an introduc-
tion from Mr Sloane. But if I should receive everyone
who comes to my house, or tries to come, I should have
no freedom at all, but be quite a slave.

The second letter was written to James Petiver,* who
unsuccessfully attempted to see Leeuwenhoek in 1711. The
passage in question reads as follows’:

* Translated from Letter dated 14 January 1710. MS.Roy.Soc. Original
in Dutch. The rest of this letter, in English translation, appeared in Phil.
Trans. (1709 [1710]), Vol. XXVI, No. 323, p. 444: not published in Dutch
or Latin collective works.

? Alexander Stuart, M.D.; born about 1673, and died in 1742. He was
elected F.R.S. in 1714. As a young man he journeyed to the Far East as a
ship’s surgeon. He entered the University of Leyden, being then 36 years
old, on 14 Dec. 1709, and graduated M.D. there on 22 June 1711. After-
wards he settled in London, where he attained a position of considerable
eminence in the medical profession. For these and other biographical
details about Stuart—who is not mentioned in the Dict. Nat. Biogr.—I am
indebted to Dr W. Bulloch, F.R.S.

* Sir Hans Sloane, M.D. (1660-1753): Secretary of the Royal Society
from 1693 till 1712, and President from 1727 to 1741. His varied scientific
and other activities are too well known to require further notice here. For
his life see the Dict. Nat. Biogr.

* James Petiver (1663 ?-1718), a London apothecary. He was elected
F.BR.S. in 1695, and wrote much on plants, shells, and other subjects. His
vast collections were purchased by Sloane, and incorporated in his own.
His life will be found in the Dict. Nat. Biogr., where it is recorded that “ in
1711 he went to Leyden, mainly to purchase Dr Hermann’s museum for
Sloane’’. Cf. also Green (1914), who speaks highly of some of Petiver’s
work.

> Translated from Letter dated 18 August 1711. MS.Roy.Soc. Original

STUART AND PETIVER 79

I have received your Letter of the 2nd of August anno
1711, wherein you are displeased at not being welcomed
at my house. I beg you please not to take it ill, seeing
that we send off everyone who tries to visit me, unless
they have some sort of introduction.

I willingly received Mr Alexander Stuart Medicina?
Doctor, who presented me with the dissertation for his
degree, and had with him your T’ransactions, and a letter
from Mr Hans Sloane, and brought with him also two
other Gentlemen; and I let them see sundry observations
of mine. Since that time I would gladly have received
you on divers days; and if you had kept by you the letter
from Mr Hans Sloane, you would not have missed a
friendly entertainment at my house. And you were sent
away especially because you were not known, and because
some 8 or 10 days earlier no less than 26 people came to
see me within four days, all of them with introductions
(except a Duke and a Count, with their Tutor): which
made me so tired, that I broke out in a sweat all over.
This being so, I beg that you will not take it amiss
in me, that, to my great sorrow, you were turned away.
If my poor old legs could have stood it, I would have
looked you up in Rotterdam.

In 1716, when he was in his 84th year, the University of
Louvain officially honoured Leeuwenhoek by sending him a
medal in recognition of his work. ‘This incident—which
corresponds roughly, at the present time, with the conferring
of an honorary degree—is not uninteresting, and may there-
fore be noted here with Leeuwenhoek’s own comments.

in Dutch. The rest of this letter was published (in English) in Phil. Trans.
(1711), Vol. XXVII, No. 331, p.316. It is not in the Dutch or Latin
collective works.

So in original: “ medicina ” (for medicinae) is not a lapsus calami but
a mistake on L.’s part—for he knew no Latin, and makes similar mistakes
elsewhere.

* Stuart’s thesis for his medical degree at Leyden was entitled ‘‘ De
structura et motu musculari’’—a subject which greatly interested L. It
was published in 1711 (4°. Leyden), and afterwards reprinted more than
once.

80 LEEUWENHOEK AND HIS “LITTLE ANIMALS ”

Among the minutes of Mr J. van der Werff, onetime
notary public of Delft, the following entry has been found’:

Upon this day the 3rd of June 1716 appeared before
me, Jacob van der Werff, notary within the Town of Delff,
in presence of the witnesses hereinafter named, Mr.
Gerard van Loon, brewer at the Brewery called This
Cross-grained World, within this town; and declared that
by him present was duly received an epistle bearing the
superscription: J’o the Highly-honoured and Far-famous
Mr. ANTHONY LEEUWENHOEK, etc. at Delff, under cover ;
together with a little silver medal, having graven upon the
obverse thereof the lhkeness of the said Mr. Leewwenhoek
encircled by the words “ANTHONY LEEUWENHOEK
fteg: Societ: Angl: Membr:” and upon the reverse thereof
the Town of Delff in the background,’ with the subscrip-
tion “in tenut labor, at tenuis non gloria” (from Virgil *) :
being enclosed in a little horn box, lined inside with
velvet, and in a little bag of woven gold, sent to the
appearant (as he explained) by Mr. ANTHONY CINK,’ Pro-

* Quoted by Servaas van Rooijen (1904, p. 381), from whose transcript
I translate. I have not seen the original.

* Gerard van Loon (1683-1758), born at Delft: historian, lawyer, and
numismatist, as well as brewer. He is now best known for his monumental
work on Dutch historical medals (4 vols. folio, 1723-1731). Cf. N. Neder.
Biogr. Woordenb. (1930), VIII, 1070. L.’s Send-brief XXII (16 May 1716)
was addressed to v. Loon, and deals with hops—a subject of mutual interest,
as L. indicates: for he notes that v. Loon’s mother owned a brewery, while
his (Leeuwenhoek’s) grandfather and great-grandfather were brewers, and
his grandmother the daughter of a brewer, ‘so that my forefathers handled
much hops.” Cf. p. 20, supra.

* And in the foreground, I may add (since this explains the motto), a
beehive with bees actively at work collecting honey from a plant bearing
flowers.

* Georg. lib. IV, v. 6—the famous poem on the oeconomy of bees. The
application to L. is both obvious and apt.

° Antony Cinck (1668-1742), a Hollander born at ’s-Hertogenbosch
(Bois-le-Duc), was a remarkable man; and in addition to his qualifications
noted above was also sometime professor of pedagogics at Louvain, and of
rhetoric at Liége. Being a Jansenist, he was later excommunicated by the
Archbishop of Mechlin and fled back to Holland, where he died (at
Dordrecht). Cf. N. Nederl. Biogr. Woordenb. (1924), VI, 300; and S. van
Rooijen (1904).

THE MEDAL FROM LOUVAIN 81

fessor of Philosophy, Canon of Liége, Prebendary of St.
Peter's at Louvain, President of the College of Cranen-
donck,' etc. etc., with written accompaniment and urgent
request that the appearant should be pleased to take upon
himself the charge of delivering the foresaid letter, medal,
box, and bag, to the said Mr. Leeuwenhoek, on behalf of
Mr. Cink and the other Professors of Medicine and
Philosophy at Louvain, as an honourable gift and recogni-
tion of their appreciation of his (Mr. Leeuwenhoek’s)
never yet properly appreciated and celebrated discoveries
in Natural Philosophy: which foresaid letter, medal, box,
and bag, according to the charge aforementioned, on
receipt thereof from the appearant, hath been handed
over to Mr. Leeuwenhoek.

Appeared likewise before us, notary and witnesses, the
oft-mentioned Mr. Anthony Leeuwenhoek, who declared
that he had received each several article, furthermore
thanking Mr. van Loon.

This document was signed by van Loon, Leeuwenhoek,
the two witnesses, and the notary. The silver medal itself
can still be seen in the Municipal Museum at Delft, and has
been depicted by van Loon’* and by Haaxman.’ The former,
in his description of it, mentions that he himself handed it
over to Leeuwenhoek in person “in a ceremonious manner.”

Leeuwenhoek’s own acknowledgement of this honour is
contained in a letter * which he addressed on 12 June 1716 to

* One of the 43 colleges at Louvain: cf. Ray (1673), p. 13.
2 G. van Loon (1731), Vol. IV, p. 223.

* Haaxman (1875), p.116. The reproduction is not good, and the Latin
motto contains a misprint.

* Send-brief XXV. Printed in Brieven (1718), Vol. IV, p.220: and in
Latin in Op. Omn. (Epist. Physiol.), Vol. IV, p.219. [The Latin version
of the passage here quoted is not a good translation of the original.] A
previous communication with Cinck (through van Loon) is to be found in
Send-brief IX, 24 Oct. 17138.

6

82 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

‘Professors Cink, Narrez,’ Rega,’ and other Gentlemen of the
College of The Wild Boar”’.’ In this letter he wrote :

By the hand of Mr. Gerard van Loon, the advocate, I
have received an obliging letter from Your Excellencies,
dated 24 May last, and a purse made of cloth-of-gold ;
wherein lieth, in a little black box, a silver medal showing
my bust on one side of it, and an emblem with the Town
of Delft in the distance on t’other.

Along with this, in further explanation and as a
dedication, was enclosed a certain Latin Poem of praise,’
overflowing with elegant expressions; but notwithstand-
ing my praises be therein sung very high, yet the poet’s
cleverness deserveth still higher praise for screwing them
up to such a pretty pitch: and when I think on the
flatteries expressed in your letter, and in the poem, I
don’t only blush, but my eyes filled with tears too, many
a time: especially because my work, which I’ve done for
many a long year, was not pursued in order to gain the
praise I now enjoy, but chiefly from a craving after

————— eee

1 Ursmer Narez (1678-1744), M.D. Louvain (1718), in his day a
distinguished man. After devoting himself to religious studies in his youth,
he became lecturer on philosophy in the University; and after qualifying
as licentiate in medicine (1706) was successively professor of botany,
anatomy and surgery, and institutes of medicine. He was also head of the
hospital at Louvain. Cf. Biogr. Nat. Belg. (1899), XV, 471.

® Henri-Joseph Réga (1690-1754), M.D. Louvain (1718). Entered the
University of Louvain—where he was born and died—in 1707, and became
licentiate in medicine in 1712. He was afterwards professor of chemistry
(1716), anatomy (1718), and clinical medicine (1719), and is an influential
and outstanding figure in the history of medicine in Belgium. Cf. Brogr.
Nat. Belg. (1903), XVII, 842.

> °t wilt Swijn (= Het wilde Zwijn or Het Varken). There were formerly
four principal schools of philosophy in the University of Louvain—each
having a particular name and symbol. The members of © The Wild Boar ’”’
or “ Collége du Porc”’ took theirs from a sign-board opposite the house
where they first assembled in 1430. Cinck and van Loon (who was his
pupil) both belonged to this ‘‘ college” or “ pedagogy’, whose fellows were
known by the apparently uncomplimentary title of “ Porkers” (Porcenses).
Cf. Ray (1673, pp. 15-17), and S. v. Rooijen (1904).

* Composed by J. G. Kerkherdere: vide infra.

THANKS FOR THE MEDAL 83

knowledge, which I notice resides in me more than in
most other men. And therewithal, whenever I found out
anything remarkable, I have thought it my duty to put
down my discovery on paper, so that all ingenious people
might be informed thereof.

In conformity with the foregoing sentiments, our octo-
genarian microscopist here proceeds to record still further
discoveries which need not now detain us. But in his next
published letter, which was addressed to the writer! of the
panegyric poem just mentioned, he makes a remark which is
worth quotation. In this letter, after giving thanks for the
Latin verses in his honour, Leeuwenhoek adds”

I always know myself well enough to ee that I’m
not worthy of the hundredth part of the expressions you
make about my poor work: for it springs only from an
inclination I have to inquire into the beginnings of
created things, in so far as ‘twas ever possible for me to
do so.

And he then delivers to the uninterested Kerkherdere a
lengthy disquisition (occupying some 18 printed pages) on his
latest botanical observations.

Another letter, written a few months later in the same
year, gives some particulars of Leeuwenhoek’s health at
this period (1716). This letter was sent not to the Royal
Society nor to Louvain but to Dr Abraham van Bleys-wyk °*

"Den Heere J: G: Kerkherdere, syner Keyserlyke en Koninglyke
Mayjesteyts Historicus.’’—Jan Gerard Kerkherdere (1677-1738) of Louvain
was a theologian, grammarian, and classical scholar. By all accounts he
possessed a special aptitude for writing Latin verses, which he was able to
produce with great facility on all ceremonious occasions. He was appointed
historiographer to the Emperor Joseph I in 1708. See N. Nederl. Biogr.
Woordenb. (1924), VI, 878; and Biogr. Nat. Belg. (1886-7), IX; also Nouv.
Biogr. Gén. (Hoefer), sub voce “ Kerckherdére.”’

* Translated from Send-brief XXVI. 22 June 1716. Published in
Brieven (1718), Vol. IV, p. 232; and in Latin in Op. Omn. (Epist. Physiol.),
Vol. IV, p. 230.

* Abraham van Bleyswijk [alias Bleiswijk, Bleyswijck, etc.] was M.D.,
and lector anatomicus at Delft—as L. himself informs us. (Cf. Send- brief
XXXVI. 26 May 1717.) He was a pupil of Boerhaave, and took his

84 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

of Delft —whom he calls his “nephew” '—and is as
follows’:

When I had the honour of being visited by yourself
and Professors Boerhaave * and Ruysch,’ who took delight
in some of my discoveries; as Mr Boerhaave was taking
his leave, and wishing me health and long life, I made
objection to him that I couldn’t go on much longer;
because, in view of my advanced age, my insides (meaning
the guts) were just about worn out. But as it was time
for the Gentlemen to be off, my further reasonings were
interrupted: wherefore I now take the liberty of
explaining my last attack to you.

'Tis now above a sennight ago that I was very short of
breath, which was accompanied by a tightness of the
chest,’ pain (as I imagine) in the diaphragm and in the
stomach, and a rising of the gorge. Accordingly, I
ordered them to fetch me some warm water, to help me

degree at Leyden with a dissertation “qua in praxi felicitas mechanicorum
vindicatur’’ (4°. Lugd. Bat. 1708). Little else now appears to be known
about him: he is not mentioned in N. Nederl. Biogr. Woordenb. or by
Hirsch. Banga (1868, pp. 614,869) who also notes the foregoing particulars
adds that Bleyswijk helped L. in his anatomical studies—a statement for
which he gives no evidence, and which may be questioned. It seems
probable that Abraham was a kinsman of Dirk Evertsz. v. B. who published
the well-known description of Delft (1667).

‘ Neef—a term which (like “ cousin” in English) did not at that date
necessarily denote the relationship now implied. It was commonly bestowed
on any kinsman.

> Send-brief XXVII, 17 Sept. 1716. Printed in Brieven (1718), Vol. IV,
p. 254: Op. Omn. (Epist. Physiol.), Vol. IV, p.250. No MS. and not in
Phil. Trans. I translate the whole letter—relying chiefly on the Dutch
printed version.

* Herman Boerhaave. See p. 296, note 6, anfra.

* Frederik Ruijsch (1638-1731), the celebrated anatomist and injector :
Professor at Amsterdam. For his life see Banga (1868, p.514 szq.),
Scheltema (1886), and N. Nederl. Biogr. Woordenb. (1914), III, 1108. He
was elected F.RB.S. in 1715 (not 1720, as stated by Banga).

> benautheyt Dutch ed. pectoris angustia Lat.—The “shortness of
breath’ and “ tightness of the chest’’ here mentioned in the originals are
vulgar expressions usually denoting asthma. Cf. Blankaart (1748) and
Gabler’s Woordenboek.

ALIMENTARY PHYSIOLOGY 85

to be sick: and no sooner had I drunk the warm water,
than I vomited, and that very easily. Soon after I was
sick again with great violence, so that the food I brought
up (as they told me) came out of my mouth and nose:
but I knew not what I was doing. When I came to
myself, I examined the stuff I had cast up: and I found
it was not only the food I’d taken the evening before, but
even what I’d had the previous mid-day.

When I let my thoughts run regarding this, I imagine
that the cause of my attack was as follows: The
membranes, whereof the coats of the guts are composed,
are so made that they have divers motions, in order to
push the chyle, that’s in them, onwards towards the
outfall‘: to bring which about, a continual increase of
contraction” of the guts is needful, as long as there
remaineth any chyle in ‘em: and if there be no chyle in
the guts, they stay at rest. And in promoting this
pushing-on of the chyle, the bile, which is poured into
the gut, helps not a little: for the bile congeals in the gut
into sharp particles.

During this attack I was very costive, just as I had
been for a good month previous, notwithstanding I was
taking only bland food: and a full three days passed ere
the chyle brought me to stool.°

I’m therefore sure there was no proper motion in my
guts, and that the gut lying next the stomach was stuffed
with food, or chyle; wherefore the stomach was also stopt
with food: for if the guts don’t lie still, the stomach
strives to unburden itself of the food that’s entered it, by
squeezing itself together: so that I’m sure the stomach,

_

" afgang orig. [=evacuatio intestinorum]. The Latin translator evaded

the word, merely saying that the chyle is pushed ‘‘deorswm’’. Chyle = chyme:
see note 5 on p. 284 infra.

* Meaning peristalsis.
* This paragraph is so paraphrased in the Latin version that its import

is rather obscure. The Dutch is particularly frank.

86 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS ”’

in a well set-up body, must so contract, that how little
food soever be in it, ’tis ever full.

The stomach being now overladen with food, and
unable to get rid of it because the gut is full of chyle;
and these long strainings of the stomach being against
its natural shape: it arouses, by its strivings, a pain in
the midriff (which they call the Diafragma), which is
thereby hindered in its continual motion; which also
stirs up a second pain. The midriff accordingly presseth
on the lung; and thereby, the lung is prevented from
performing its office. And this being so, there must
follow a great tightness and a great vomiting: and such
violence is done to the body, to the stomach as well as to
the guts, that the chyle in the gut is thereby pushed
onwards; so that there followeth a motion in the gut
itself. And, as I imagine, when the gut is full up, the
gall-bladder can’t empty its bile into the gut, yet with
these onpushings of the chyle it pours a great quantity
of bile into the guts; therefore on the day when this
happens, four or five stools are brought off, whereas on
the other days there ensueth a constipation.

You have here the feeble notions I’ve hammered out
of my last distemper. Pray take it not amiss that I take
upon myself to argufy about it.

The foregoing lines are not only an interesting record of
Leeuwenhoek’s bodily condition in his 84th year, but also a
typical example of his own particular system of physiology.

References to his age and his infirmities become more
numerous with advancing years. He continues to make and
record observations and speculations, and to promise more:
but he often begs the Royal Society to make allowance for his
senescence, and sometimes qualifies his promises with expres-
sions such as “if my health permits”.' At the end of 1717
Leeuwenhoek thought his own end was near; and he therefore
inscribed a “last letter” to the Society, as an envoy to the

* met gesondheijt, ete.

‘“‘“DAST LETTER’’ TO THE ROYAL SOCIETY 87

final collective edition of his works. Concluding this letter
he wrote’:

Methinks these will be the last observations I shall
be able to send to you honourable Gentlemen; because
my hands grow weak, and suffer from a little shakiness,
which is due to my far advanced years, a good 85 having
passed by me. And so I send you with this my deep
thankfulness, because in the year 1679* you were so kind
as to elect me, quite beyond my competence, a Fellow
of the most worthy College of the Royal Society ; and to
send me a Diploma, together with two letters from the
Secretaries of the Society, which likewise made known
to me my election, by all the votes of the Fellows, then
gathered together at a very full meeting.”

I thank you also for the Philosophical Transactions,
which Your Excellencies have been so good as to send
me from time to time.

For all these honours and gifts aforesaid, I herewith
convey to you my gratitude once more.

But the end was not yet. After writing the foregoing
lines, Leeuwenhoek lived for nearly six years more ; and
during this period he sent the Society no less than 18 more
letters (including 2 posthumous epistles), containing a variety
of new microscopical discoveries. In a postscript to one of
these letters he says *:

1 From Letter dated 20 November 1717. To the Royal Society. There
is no MS. of this letter in the Roy. Soc. collection. It was not published
in the Phil. Trans., but was printed in both Dutch and Latin : Send-brieven
(1718), No. XLVI, p. 451; Opera Omnia [Epist. Physiol.] (1719), Vol. IV,
No. XLVI, p. 437. I translate from these published versions.—It is
remarkable that Miall (1912, p. 201) and several other students of L. have
assumed that this was really his last letter.

? 1680, according to present-day reckoning (N.S.). Cf. p. 48 supra.

* Cf. p. 48, note 6, supra.

‘From Letter dated 24 January 1721. To the Royal Society. MS.
Roy. Soc. (The postscript is in L.’s own hand, but the letter itself is in
different handwriting.) Original in Dutch—from which I translate. An
English version of this letter was published in Phil. Trans. (1721),

Vol. XXXI, No. 367, p.134. It is not in the Dutch or Latin collected
works.

88 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

I humbly beg that you will make some allowance for
me, my years having mounted to a great height. A
certain Gentleman, visiting me a few months ago,
besought me to make some further discoveries; adding,
that those fruits which ripen in the autumn last the
longest. And this is now indeed the Autumn of my
days, for they have today mounted up to 88} years.

Yet only three months later he wrote with characteristic
confidence—after describing some observations on the structure
of peas :*

"Tis my intention to inquire into these marvellous
structures more narrowly, just for my own amusement.’

Next year, after communicating other discoveries,
Leeuwenhoek sent the Society still further observations
together with the following unpublished personal remarks’:

The learned Dr James Jurin, Secretary of the Royal
Society,’ writes to me from London in your name, on
22 Feb. 1724, with so many expressions of satisfaction at
my discoveries, which I sent to your Fellows, that I stood
all abashed when the letter was read to me; nay, my
eyes filled with tears at all the great expressions, and

" The same remark is made by L. in his Send-brief XXXII, 2 March
1717, to Abraham y. Bleyswijk (printed in Dutch and Latin works): ef.
Brieven, IV, 317.

* From Letter dated 11 April 1721. To the Royal Society. MS. Roy.
Soc. Printed (in English) in Phil. Trans. (1721), Vol. XXXI, No. 368,
p.190. Not in Dutch or Latin collected works.

* alleen voor mijn plaijsier MS.

* Translated from Letter dated 21 April 1722. To the Royal Society.
MS. Roy. Soc. Partially published (in English) in Phil. Trans. (1722),
Vol. XXXII, No. 371, p.72. Not in Dutch or Latin collective works.
Original in Dutch, in L.’s own hand—showing evident signs of senility.

° De seer geleerde Heer Jacob Jurin, Secretaris van Hare Hoog Edele
Heeren Vergadering MS. It is impossible to translate these merely formal
expressions into literal English without making them appear rather
ridiculous, and so spoiling their intention: I therefore paraphrase.—James
Jurin (1684-1750) was a physician—sometime Fellow of Trinity College,
Cambridge, and President of the Royal College of Physicians of London. He
was elected F.R.S. in 1717, and became Secretary on 30 Nov. 1721. His
life will be found in the Dict. Nat. Biogr.

REPLY TO JAMES JURIN 89

respect that they have for my work, which I accomplish
alone by my own impulse and inclination. For no money
could ever have driven me to make discoveries, and I’m
only working out as ’twere an impulse that was born in
me, and I imagine I never meet with any other people
who would spend so much time and work in searching
into the things of Nature. And withal I had great pleasure
too at hearing that the learned and curious Mr James
Jurin’s investigations have made him eye-witness of my
discoveries."

The same Gentleman also said, that your Fellows very
earnestly desired, if ’twere possible, that my observations
should be confirmed and cleared up by repeating them, so
that the mouth of the unbelieving might be stifled.

On this matter I would reply to your Honourable
Fellows, that I have indeed inquired into many things of
one and the same nature, but not thought it needful to
describe them all, because the one must imply the others.
And those things that are not easy to believe, I have left
standing for days, nay years, before the magnifying-glass,
to let them be seen by as many people as possible; like
the vessels in the nerves, which have lain so long before
the magnifying-glass, that they have been all eaten up by
that little creature the Mite.”

By this time Leeuwenhoek was an old and sick and dying
man. But despite his age and his infirmities he still continued
to make observations and send letters to the Royal Society.
In two letters, written in March and May 1723, he even gave
the Society an account of the illness from which he suffered
in the last year of his life. Both letters were translated into
Latin, and they were the last he lived to sign: their Dutch
originals are now lost. As the relevant passages are of great
personal interest, I shall quote them at length. On19 March

“The whole of this paragraph is ungrammatical and very loosely
constructed in the original.

* The two foregoing paragraphs were paraphrased—not translated—in the
Phil. Trans., though their sense is there conveyed correctly.

90 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS”’

1723, after discussing the dimensions of blood-corpuscles, he
wrote :

This also I have to add: that notwithstanding my
advanced age cannot but hinder my sight, yet my right
eye, to my great annoyance, groweth somewhat dim. I
think this comes to pass for the reason that sundry
blood-corpuscles, floating in the crystalline humor,’ stray
in front of my sight; some whereof being joined together
in no or only an irregular order, with others floating
separately, cause an appearance of little clouds* in my
eye. Moreover, as I generally use my right eye, I
readily shut my left eye whilst making observations,
wherefore my eyesight is dimmer than ’twas wont to be.

Not so long ago, to wit this last January, I was seized
with a violent motion about that great and necessary
organ we call the diaphragm: indeed, ’twas such that
those present were not a little alarmed at it. When the
motion abated, and I sought to know the name of this
distemper, the Physician who was at hand replied that
it was a palpitation of the heart. But I thought the

*To Dr James Jurin, Sec. R.S. MS.Roy.Soc. Printed in Phil. Trans.
(1723), Vol. XXXII, No. 877, p.341; not printed in Dutch or Latin
collected works. I translate from the original Latin MS.—inscribed in an
unknown hand (not Hoogyliet’s).

? humor crystallinws—the old name for what is now called the “ crystalline
lens” (cf. Blankaart, 1748, swb voce). This structure was described in
detail, in many animals, by L.; and he knew that it was solid and stratified
and that it contained no blood-vessels or corpuscles. Consequently, I
cannot help thinking that in his original words—here mistranslated (?) into
Latin—he must really have referred to the vitreows humor: which would
obviously be nearer the truth.

* mibeculae Phil. Trans. mnubeculae MS. The printed word is meaning-
less, and greatly puzzled me until I discovered that it was merely a
misreading of the original. lL. was here referring, of course, to the familiar
entoptic phenomena called muscae volitantes—now known to arise from
shadows cast on the retina by strands in the vitreous humor. (Cf. Brewerton,
1930.) These appearances were first described by L. in his Letter 41,
14 Apr. 1684, to F. Aston (Ondervind. & Beschouw., 1684, p.19; also in
Latin editions; incomplete English translations in Phil. Trans. XIV, 790
[ =780], and Hoole, I, 241).

LAST SICKNESS 91

Physician was wrong; for whilst the motion lasted,
I off put my hand on my pulse, and could feel no
quickening of its beat. This violent motion, returning
at intervals, lasted for about three days; during which
time my stomach and guts ceased to perform their office
and motion, so that I was verily persuaded I stood at
death’s door.

In my opinion there was some obstruction, not less
than a crown piece in bigness,’ stopping my diaphragm.

On 31 May 1723 Leeuwenhoek actually sent the Royal
Society a description of the histology of the diaphragm, which
he had meanwhile studied (in sheep and oxen) in order to
support the opinions expressed in the foregoing letter. And
at the end of his account of the various muscles and tendons
and vessels observable in the midriff he added :*

Accordingly, the oftener I recall the foresaid distemper
which seized me last winter, and which I attributed
mostly to my diaphragm, the more am I of opinion that
our Physicians are mistaken when they call that
commotion, which we sometimes feel in the region of our
chest, a palpitation of the heart. For my part, | am
persuaded that such palpitations arise from a disorder
of the Diaphragm; howbeit this may be brought about
either by a deficiency of diet, or by obstruction of those
blood-vessels which run through the diaphragm in great
plenty. Such an obstruction can easily excite convulsive
motions in the tendons aforesaid; and I believe this was
the very cause of my own complaint.

Towards the middle of August, 1723, Leeuwenhoek had
another seizure; and now he was indeed—as he himself

‘non minorem nummo imperialt MS. I take nummus imperialis to mean
a rizksdaalder (—= 2% florins), which was roughly of the size and value of an
English 5-shilling piece.

* From Letter dated 31 May 1723. To the Royal Society. MS.Roy.Soc.
Printed in full in Phil. Trans. (1723), Vol. XXXII, No. 379, p.400. Not
in Dutch or Latin collective editions. Original MS. in Latin, from which
I translate.

92 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”

realized—at death’s door. Yet even Death’s proximity could
not abate his scientific zeal. Boitet the publisher—who
cannot always be trusted, but who here probably wrote from
recent personal knowledge—has left it on record that he
continued his researches to the very end. He says:?

Our Leeuwenhoek, who had a sound mind in a sound
body, felt however about a year before his death that his
bodily powers were getting noticeably weaker, owing to
an asthmatical chest and other symptoms: nevertheless,
he continued his course cheerfully to the end of his life
along the track of Science, to win a deathless name at
last, though forsooth he had won the race long before
during his lifetime. Six-and-thirty hours before his death,
when his limbs were already growing numb, the fire of
his ardour glowed still so bright, that, with lips stammer-
ing and well-nigh stiff, he directed his thoughts to be set
down on paper regarding a kind of sand which a certain
distinguished gentleman, a director of the East-India
Company, had handed over to him, to find out whether
any gold were concealed therein.

And this account is supported from another quarter. As
he lay dying, Leeuwenhoek summoned his friend Dr Jan
Hoogvliet * to his bedside, and requested him to translate a
couple of letters* into Latin and send them to the Royal Society
as a parting gift. The good doctor did so, and dispatched

* Boitet (1729), p. 768—translated. Z

* Little seems to be now known about Johannes Hoogvliet, who is not
mentioned by Banga or Hirsch or in the N. Nederl. Biogr. Woordenb. or any
other available works cf reference. I have been able to ascertain only that
he was a surgeon practising at Delft, and that he once published a work on
wounds (Konst om wonden te schouwen, etc. 8°. Rotterdam, 1749). He was
probably a kinsman (? brother) of the poet Arnold Hoogvliet (1687-1763) of
Vlaardingen, who wrote the panegyric poem prefixed to the Send-brieven,
and whose father—a shipowner and sheriff—was also called Johannes.

* On “corpuscles in the blood and in the dregs of wine” and “the
generation of animals and palpitation of the diaphragm.’”’ Published
posthumously in Phil. Trans. (1724), Vol. XXXII, No. 380, pp. 436-440:
not in Dutch or Latin collective works.

BOITET AND HOOGVLIET 93

them with the following covering note from himself to the
Secretary’ :

Our venerable old Leeuwenhoek, being already in the
throes of death, though none the less mindful of his art,
ordered me to be called to him ; and raising his eyes, now
heavy with death,’ kept asking me in half-broken words
if I would translate these two letters out of our native
tongue into Latin, and send them, most distinguished Sir,
to you. In obedience, therefore, to these commands of
so great a man, with whom I had been for some years on
terms of most intimate friendship*, I can do no less than
send you, most learned Sir, this final gift of my dying and
most dear friend: hoping that these his last efforts will
prove acceptable to you.

I pray that the Supreme Judge of all things may long
bless Your Excellency, and the Royal Society: Farewell.

Leeuwenhoek’s death was first made known to the

Fellows of the Royal Society by a letter from the minister of
his church—the Rev. Mr Peter Gribius.* His communication

1 MS. Roy. Soc., No. 1413; H. 3.112. Joannes Hoogvlietius to J. Jurin,
Sec. R.S., 4 September 1723. Printed fully (except last sentence) in Phil.
Trans. (1724), XXXII, 435. My translation is made from the original MS.
(very clearly written in good classical Latin), whose endorsement shows that
the letter was read at a meeting of the Society on 7 Nov. 1723 [O.S].

2 attollensque oculos jam gravatos morte MS. “ mij met reeds half gebroken
oogen aanstarende’”” Haaxman (1875, p.122)—a mistranslation.

= quo abhinc jam aliquot annos usus fueram faniliarissime MS. Haaxman,
ioc. cit., also misconstrues these words, which do not imply that Hoogvliet
had been accustomed to translate L.’s letters into Latin for several years.
The expression ‘ wtor aliquo”’ means “I enjoy the friendship of someone ”:
ef. Cicero—His Fabricius semper est wsus Oppianicus familiarissime (pro
Cluentio, XVI, 461, 46). Moreover, no other known letters of L. are extant
in Hoogvliet’s handwriting.

* He styled himself “ Petrus Gribius, Ecclesiae Delphensis pastor senex.”’
Gribius [alias Grybius] was born at Middelburg in 1651, and died at Delft
in 1739. He was educated in the Latin Schools of Amsterdam, Utrecht,
and Leyden, and before taking holy orders visited Oxford and Cambridge.
He became minister of the New Church at Delft in 1681 (Boitet, 1729,
p. 441), and retired in 1734. Some of his sermons and essays have been
published, and his portrait was painted by Thomas v. d. Wilt (cf. p. 345).
Further details of his life will be found in an article contributed by F. S.
Knipsheer to the N. Nederl. Biogr. Woordenb. (1924), VI, 634.

94 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

has never been published, and even its existence has hitherto
been overlooked. Yet it is a document of the greatest
interest: for it not only announced Leeuwenhoek’s death, but
also recorded the exact date thereof, and gave a few particulars
regarding his last illness and the cause of his decease —as
determined by his medical advisors. I shall therefore give
this letter in its entirety. The original is written in Latin,
and addressed to Dr James’ Jurin, Secretary of the Royal
Society. Dated from Delft, 30 August 1723, it runs as
follows >
I venture to interrupt you, most distinguished Sir, in
your very urgent engagements and duties, solely because
I am moved thereto by the tears of Maria, the only
daughter of her great father Antony van Leeuwenhoek ;
who, while he neither feared nor desired his last day,
peacefully concluded it upon the 26th of August; being
then over ninety, and thus, having reached arare old age,
neither unripe nor half-ripe, though verily more than
mature. For ’tis with man as with pear or apple, on a
tree laden with fruits, some whereof it letteth fall thickly
and perforce, while others, when they be more than ripe,
drop singly of their own accord.’ As the Poet’ elegantly
saith :

Kijpes ebeotaciw Oavaroto
Moupia, ds ovK gore huyeiv Bpotov, odd’ vroAnEat.”

" Gribius wrongly addressed him as “John” (Nobilissimo Viro Joanni
Jurin Regiae Societati a secretis Illustrissimo).

* MS. Roy. Soc., No. 1214; G.2.3. The translation of this letter has
been by no means easy: for it contains several classical quotations and
veiled allusions, and some unusual words and expressions—designed,
apparently, to show off the writer’s scholarship. Nevertheless, its latinity
seems not altogether irreproachable. In tracing the references to Homer
and Statius I have been greatly assisted by Prof. D’Arcy Thompson, F.R.S.

° The foregoing lines in the MS. are apparently a paraphrase of Cicero:
“quasi poma ex arboribus, cruda si sunt, vi avelluntur, si matura et cocta,
decidunt’’ (de Sen. lib. XIX, § 71 ad finem). Some modern texts read “ vix
evelluntur,’ but Gribius’s words indicate that he was familiar with the
older version.

* Homer, Ilias XII, 326-7.
° “Ten thousand fates of death do every way beset us, and these no

FIRST EPISTLE OF PASTOR GRIBIUS 95

Yet ’tis our duty to submit to the wise dispensations of
God, Whom we wrongfully defraud of His rights unless
we humbly suffer each one of ours to live and die according
to His will.

The notion possessed our good old man that he lay
a-dying of a distemper of his diaphragm, though in fact
‘twas of his lungs; and their gradual obstruction, turning
slowly into a suppuration, reached such a pitch that he
cast up purulent sputa and died when the lung had
festered, on the sixth day after he took to his bed.’ So
at least say our Physicians, who are highly skilled in
such matters: for my part, I know nought of diseases; a
cobbler should stick to his lasts.’

A little cabinet, furnished with some most select
glasses (commonly called Mcxpocxoma*), to be given after
his death to the Royal Society, will be sent to you within
six or seven weeks by his daughter, as she hath informed
me.

Amongst us he has left a reputation truly good, and
enshrined in the Temple of Memory, by virtue of his
indefatigable inquiries into Nature. To you, most noble
Sir, who hold an honorable office, and one worthy of
your deserts, I wish many a long year of life, that for the

mortal may escape nor avoid” (translation of Lang, Leaf, and Myers). The
last word of the quotation is given wrongly by Gribius: it should be
imanrvéat. (Cf. Ilias ed. Doederlein, Lips.-Lond. 1863.)

’ Ag the foregoing lines constitute the only known record of the cause of
L.’s death, the reader will doubtless desire to see the original words. The
MS. says: Bonwm senem tenwit opinio se moriturum diaphragmatis vitio,
sed pulmonum fuit, eorumque lenta obstructio sensim in suppurationem
vergens, adeo ut phlegmata purulenta ejecerit, et suppurato pulmone obierit,
seato postquam decubuit die. It is clear that L. died of broncho-pneumonia:
and there is much evidence (largely unpublished) in his later letters to show
that he had suffered for many years from chronic bronchitis.

= ne sutor ultra crepidas MS. This familiar proverb occurs in several
forms, and according to Pliny originated in a saying of the painter Apelles.
Pliny’s version is © e supra crepidam sutor judicaret”’ (Hist. Nat. XXXV,
[10]36. Fol. Genevae [1582] p. 629).

* = Microscopes. To write the word thus in Greek—even at that date—
was a ridiculous bit of pedantry.

96 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”’

public benefit you may live to equal, or even excel, those
grand old men of Troy.’

The cabinet of microscopes bequeathed to the Royal
Society—yreferred to in the foregoing letter—-had been briefly
described by Leeuwenhoek himself twenty-two years earlier.
In an unpublished passage in an otherwise published letter to
the Society he had written *:

I have a very little Cabinet, lacquered black and gilded,
that comprehendeth within it five little drawers, wherein
lie inclosed 13 long and square little tin cases, which I
have covered over with black leather; and in each of
these little cases lie two ground magnifying-glasses
(making 26 in all), every one of them ground by myself,
and mounted in silver, and furthermore set in silver,
almost all of them in silver that I extracted from the ore,
and separated from the gold wherewith it was charged ;
and therewithal is writ down what olject standeth before
each little glass.

This little Cabinet with the said magnifying-glasses, as
I may yet have some use for it, | have committed to my
only daughter, bidding her send it to You after my death,
in acknowledgement of my gratitude for the honour I
have enjoyed and received from Your Excellencies.

On 4 October 1723, Leeuwenhoek’s bequest was duly and
dutifully dispatched to the Royal Society by his daughter

1 ut... Iliacos aequare senes aut vincere possis MS. This is apparently

borrowed from the hexameter of Statius: “‘Iliacos aequare senes, et vincere
persta”’ (Silvae, lib. II, iii, 73). I take it that by these words Gribius
meant to say that he hoped Dr Jurin would live long enough to rival, by his
scientific performances, the doughty deeds of the heroes of ancient Greece
in the field of battle: but the comparison seems somewhat forced, to say
the least.

2 Brom Letter 140. 2 August 1701. MS.Roy.Soc. Printed (Dutch)
in Sevende Vervolg der Brieven (1702), p. 375; and (Latin) in Opera Omnia
(Contin. Arc. Nat.), Vol. III, p. 355. I translate from the Dutch MS.
(Words here italicized were underlined by L. himself in the original.)
Although this Letter was not published in the Phil. Trans., the passage
here given was translated into English and entered in the Society’s Letter-
books (Vol. XIII, p. 183), and this entry was long afterwards extracted and
printed by Weld (Vol. I, pp. 244-8).

SECOND EPISTLE OF GRIBIUS 97

Maria along with two covering letters. One of these was a
formal notification in Latin from the Rev. Mr Gribius; the
other was a simple Dutch letter from Maria herself. I shall
give them both.

Gribius wrote’:

In our present scientific age, 6 Maxapirns” Antony van
Leeuwenhoek considered that what is true in natural
philosophy can be most fruitfully investigated by the
experimental method, supported by the evidence of the
senses; for which reason, by diligence and tireless labour
he made with his own hand certain most excellent lenses,
with the aid of which he discovered many secrets of
Nature, now famous throughout the whole philosophical
World: of which sacred apparatus he bequeathed no
contemptible a share, inclosed by himself in this little
cabinet, to the Royal Society, with no other object than
to afford those ingenious and most erudite men a token
of his veneration, and as a mark of his gratitude for
having been enrolled among their learned Company.

His Daughter (a spinster of excellent repute, who has
preferred a single life to matrimony, in order that she
might ever continue to attend her father) earnestly begs
this one favour: that you disdain not to send back word
that this little present hath not gone astray, but is come
safe into your hands; which I likewise fully trust was
the lot of my own letter*® written to you, in no joyful
spirit, five weeks ago.

I pray God, most illustrious Sir, that He suffer you
long to continue shining as a great and singular light and
star of the first magnitude to Philosophy.

1 Translated from MS.Roy.Soc., No. 1215; G.2.4. Petrus Gribius,
Eccl. Delph. pastor senex, to J. Jurin, Sec. h.S.; 4 Oct. 1723. Original in
Latin: unpublished.

° = The blessed (7.e. in heaven).

° Referring to his communication of 30 August 1723-—p. 94 ante.
From this remark it must be inferred that the Secretary of the Royal Society
had neglected to acknowledge Gribius’s first epistle.

7

cc

98 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”

Maria’s letter was very different from the foregoing. It
made no pretensions to scientific knowledge or classical
scholarship, and was written not in Latin but in homely,
illiterate, and even ungrammatical Dutch. It was apparently
dictated—not written by herself—for it is inscribed in a
handwriting different from the somewhat shaky signature.’
(Maria was then 67 years of age.) But for all that it is one
of the most beautiful and pitiful letters I have ever read—
breathing sincerity and filial devotion in every word, and
eloquently testifying to Leeuwenhoek’s own qualities as a
man and father. Maria wrote’:

Most excellent Sirs

Instantly upon the sad death of my beloved father
Anthonij van Lewenhoek,* I took care to have this my *
loss made known to you by our reverenced and most
learned pastor, Peterus Griebius’; adding thereto, that
after the space of six weeks would be sent to the noble
and far famed Royal Society, at London, a little cabinet
with magnifying-glasses, made of silver wrought out of
the mineral by my dear departed father his very self;
which same is now sent to Your Excellencies, even as
my late father made it up, with six-and-twenty magnifying-
glasses in their little cases: truly in itself a poor present
to so celebrated a Royal Society, but meant to betoken
my father’s deep respect for such a learned Society,
whereof my most beloved and dear Father, of blessed

* Cf. Plate XIII.

* MS.Roy.Soc., No. 2137; Z.6.38. Maria van Leeuwenhoek to the
Royal Society, 4 Oct. 1723. Original in Dutch, from which the above is
a, translation—and a poor one: for I confess myself incompetent to turn the
pathetic but unscholarly expressions of Maria into intelligible modern
English faithfully.

* So spelled in MS.

‘In the MS. the words “this my” are reiterated: “dit mijn mijn dit
mijn’’—the second dit being scored out. Maria apparently hesitated, in
dictating the letter, between saying “mijn” or © dit mijn”: and in her
agitation she failed to notice that the word mijn was finally left written
thrice.

* So spelled in MS.

PLATE XIII

bane frag ad,
POY POLL, fe
ae ne f i aes os TY

‘UMOUY o[dulexe eos 9U}—oinjzeusis Joy SUIMOYS : (EGLT “9°90 F)

ALHIOOS IVAOU FHL OL YALLAT S.VIUVA AO SANIT ISvT

rere

Es ——— cay gl Baad 94
Preypuracion

. poring vag gheyrog oeg
? 7,

sg 2ehe we

DPAIIF fe

UCU

facing p. 99

MARIA’S LETTER 99

memory, hath had the honour to have been a fellow-
member. Your most humble servitress now begs Your
Excellencies, please to be so good as to let me have word
whether this trifling gift is come safe into the hands of
the far famous College, that I may rest content I have
fulfilled my Father’s wish.

Wherewith, most famous Gentlemen,

your most respectful Servitress

and my father’s Grief-stricken

Delft, the Daughter now and hereafter
4th October 1723 — will ever be and remains
New Style Your humble Servant

Maria van Leeuwenhoek
Antoni’s daughter

This letter needs no comment: it speaks for itself. I need
only add here that the little cabinet of microscopes was safely
received by the Royal Society: that it was examined and
reported upon by the Vice-President, and by one of the
Fellows at a later date: that it was treasured by the Society
for a century—and then lost." In return for the bequest, the
Council in 1724 sent Maria “a handsome silver bowl, bearing
the arms of the Society.” °

Leeuwenhoek was buried in the Old Church of Delft on
Sunday the 31st of August 1723—‘ with 16 pall-bearers and
with coaches and tollings of the bell at 3 intervals ’ ’—and his
grave was finally closed two days later (2 September).* He
was first laid to rest at a spot in the north church (section 19,
grave 12) where his second wife had previously been interred
(1694)°: but in 1739 his daughter Maria erected a monument

" Cf. p. 314 infra.

* Weld (1848), Vol. I, p. 245. This also has disappeared.

* “met 16 d°. en met koetsen en 3 poose luijens’’ (Begrafenisregister
Oude Kerk. No. 138 Archief Delft). I am indebted to Dr Schierbeek and
Mevr. Bouricius for this extract. From other entries in the Archives it
appears that L. was actually entitled to have 18 pall-bearers.

* This accounts for the different dates of burial given by Schierbeek
(1930)—31 Aug. and 2 Sept. 1723—as he informs me in a letter.

° Discovered by Jhr. mr. E. A. van Beresteijn, and communicated to

Dr Bouricius—from whose posthumous papers the details given above have
been published by Dr Schierbeek (1930).

ce

100 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”
to his memory—on the north side of the tower, in the north
transept—and the two bodies were then transferred to its foot
(section 22, graves 14 and 15), where they now he. Maria
was buried in the same sepulchre* on 30 April 1745.

The tomb of Leeuwenhoek is shown in Plate XV, which is
reproduced from an old engraving.” It is little altered at the
present day.” On the stone pedestal, which rests upon two
plinths and is surmounted by a white marble skull and
crossbones flanked by two spheres, is the inscription:

PATRI CHARISSIMO HOC MONUMENTUM FILIA
MARIA A LEEUWENHOEK MOERENS P.4

On the obelisk rising from the pedestal there rests a white
marble urn supporting a gilt torch; and a circular plaque
of similar marble, surrounded by decorative ribbon-work, 1s
affixed to the front. The plaque bears a profile portrait of
Leeuwenhoek. On the front of the obelisk is inscribed :

PIAE ET AET. MEM.
ANTONII A LEEUWENHOEK

REG. ANGL. SOCIET. MEMBRI
QUI NATURAE PENETRALIA ET PHYSICES ARCANA
MICROSCOPIIS AB IPSO INVENTIS ET MIRABILI ARTE FABRICATIS
ASSIDUO STUDIO ET PERSCRUTATIONE DETEGENDO ET IDIOMATE BELGICO
DESCRIBENDO DE TOTO TERRARUM ORBE OPTIME MERUIT.
NAT. DELPH. XXIV OCT. A®°, MVI°XXXII
IBIDEMQUE DENAT. XXVI AUGUSTI A° MVII°XXIII.®

1 This tomb was purchased by L. himself on 8 June 1686 (fide Schierbeek,
1930).
? Supplement to Boitet (1729)—not found in all copies of this work.

° The only recent description of the tomb is that of Harris (1921), who
appears to have visited it under unfavourable conditions and was con-
sequently displeased. But his knowledge of L. was obviously very
superficial, and his paper—in a popular journal—cannot be taken seriously.

‘Pp. = posuit. “To her most beloved Father this monument his
daughter Maria van Leeuwenhoek mourning has erected.”

> “mo the fond and everlasting memory of Antony van Leeuwenhoek,
Fellow of the English Royal Society, who, by detecting through diligent
application and scrutiny the mysteries of Nature and the secrets of natural
philosophy by means of microscopes invented and marvellously constructed
by himself, and by describing them in the Dutch dialect, has earned the

XIV

PLATE

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THE OLD CHURCH OF DELFT
West Front—viewed from Oude Delft.
From an engraving by P. Smith after C. Decker, published by Boitet (1729).

facing p. 100

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PLATE XV

LEEUWENHOEK’S TOMB IN THE OLD CHURCH

From an engraving by J. C. Philips (1740) after a drawing by the designer,
T. Jelgersma.

facing p. 101

MONUMENTAL INSCRIPTIONS 101

The monument is set in an arched niche, doubly recessed,
the pilasters of the inner arch bearing two stone lamps and
its apex the veiled head of a woman. ‘The whole is protected
by a decorative’ iron railing. On the floor, in front of the
railing, is a stone slab covering the tomb. Upon this is cut:

HIER RUST
ANTHONY VAN LEEWENHOEK,
OUTSTE LIT VAN DE KOONINCKLIJKE SOSYTEYT IN LONDE,
GEBOOREN BINNEN DE STADT DELFT OP DEN 24STEN OCTOBER 1632,

EN OVERLEEDEN OP DEN 26STEN AUGUSTY 1723,
OUT SYNDE 90 JAAR, 10 MAANDE EN 2 DAGEN.2

This is followed by some verses “ to the reader ”’ composed
by Leeuwenhoek’s young friend and fellow-townsman Hubert
Poot (1689-1733)—the rustic poet who has been called the
‘Bobbie Burns of Holland” (see Plate XVI)—which run

thus:
HEEFT ELK, 0 WANDELAER, ALOM

ONTZAGH VOOR HOOGEN OUDERDOM
EN WONDERBARE GAVEN,

Soo SET EERBIEDIGH HIER UW’ STAP:

HIER LEGT DE GRYSE WEETENSCHAP
In LEEWENHOEK BiGRAVEN.®

———————

highest approbation of the whole world. Born at Delft 24 October 1632, and
died in the same place 26 August 1723.”—The final words “de toto . . .
meruit”’ ave curiously mistranslated “by which he astonished the whole
world” by Wildeman (1903, p. 48).

' Morre (1912), following Wildeman (1903), describes this as “elegant ”’:
but Harris (1921) regards it as particularly nasty. I eall it “ decorative ”’
in a descriptive sense: the reader can form his own estimate of its artistic
merits from the illustration.

* “Here lieth Anthony van Leewenhoek, oldest Fellow of the Royal
Society in London, born within the town of Delft on the 24th of October
1632, and deceased on the 26th of August 1723, being aged 90 years, 10
months, and 2 days.”’ Note the spelling of L.’s name and the rest of the
inscription—-which has been “ corrected’ by every previous transcriber.

* “ Since everyone, O traveller,
Great age respecteth, everywhere,
And gifts of wondrous merit :
So here all reverently tread,
Where Science old and gray of head
In LEEWENHOKK lies buried.”

102 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

At the foot of the tombstone has been added an inscrip-
tion stating that along with her father lies “Maria van
Leeuwenhoek, his daughter, born at Delft the 22nd of
September 1656, and passed away the 25th of April 1745.”
There is also a carved flying eagle, clutching a shield on
which the coat-of-arms of the Leeuwenhoeks was probably
once emblazoned.’

The following entry’ relating to Leeuwenhoek’s tomb is
to be found in the Archives of Delft, from which it was
extracted and published by Soutendam (1875) *:

In the North Transept of the Old Church of Delft,
against the wali of the tower, was erected in the year 1739,
at the expense of Mistress Maria van Leeuwenhoek, in
memory of her late father the world-famed Mr. Anthony
van Leeuwenhoek (son of Phillip van Leeuwenhoek,
Anthony’s son, and of Margaret Bel van den Bergh,
James’s daughter), under the supervision and care of
Mr. William van der Lely, at that time Councillor
and Treasurer of the town of Delft, an Obelisk, simply
but bravely and elegantly designed by the artist Taco
Jelgersma, at Haarlem, and wholly wrought by the
stone-mason Gerrit van der Giesen.

There is little more to add: but after recording the handi-
work of Mr Gerard van der Giesen, the good Dutch mason,
T should like to recall a few lines left by the more sensitive
hand of an Englishman, Martin Folkes “Esq., Vice-President of
the Royal Society, in his report on the microscopes bequeathed
to the Society by Leenwenhoek. Folkes’s account of these

* See p. 305 infra.

? IT translate Soutendam’s transcription—not having seen the original.
It is not unlikely that our famous “ English” artist Sir Peter Lely was a
kinsman of the Willem van der Lely, sometime Burgomaster of Delft,
whose signature was appended to this document.

° I give it in full, because the information supplied by Boitet (1729,
supplement), Haaxman (1875), Morre (1912), and others, is incomplete.

* Martin Folkes (1690-1754) was an antiquary, and a distinguished man
in his day. He studied in France (Saumur) and later at Cambridge. He
was elected F.R.S. in 1714, Vice-President of the Society in 1723, and
was President from 1741 to 1753: he was also President of the Society of
Antiquaries (1750) and a member of the Académie des Sciences (1742)2 Oe
Dict. Nat. Biogr. and Rec. Roy. Soc.

XVI

PLATE

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1733

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facing p. 102

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MARTIN FOLKES, ESQ. 103

instruments will be considered later ': I shall here give only
what he says about their maker, because it shows how
Leeuwenhoek was regarded by the Society at that date and
will serve as a funeral oration—for want of any other or
better. In the Philosophical Transactions for November and
December, 1723, Folkes wrote’:

It is now above 50 Years, since the late Mr. Leewwenhoek
first began his Correspondence with the Royal Society ;
when he was recommended by Dr. Regnerus de Graaf, as
a Person already considerable by his Microscopical
Discoveries, made with Glasses contrived by himself,
and excelling even those of the famous Hustachio Divini,
so much talk’d of in the learned World: And as he has
ever since that Time apply’d himself, with the greatest
Diligence and Success, to the same Sort of Observations,
no Doubt can be made of the Excellency of those Instru-
ments he so long us’d, so much improv’d, and upon the
fullest Experience so often commended in his Letters ;
great Part of which, at his Decease, he thought fit to
bequeath to this Society, for whom he ever express’d
the greatest Esteem and Respect.

He had, indeed, intimated this Design in several of his
Letters, and in his last Will and Testament’* gave
Orders, that the Glasses should be delivered as soon as
conveniently might be after his Decease; which was
accordingly done, by the Directions of his surviving
Daughter, Mrs. Maria Van Leeuwenhoek, to whose great
Care we are obligd, for the safe and speedy Delivery of
this very curious and valuable Present.’

" See p. 314 sq., infra. * See Folkes (1724).

* According to Servaas v. Rooijen (1904, p. 384), L.’s will is still extant
in the protocols of the notary Jan de Vries at Delft. I have not seen this
document—executed jointly by Antony and Maria, “ both being sound of
mind and body,” on 30 November 1721.

* = Mistress: a title applied at that date, of course, to unmarried
women.

° Here follows an account of the cabinet of microscopes, and a list of
the objects placed before them. See p. 314 sq., infra.

104

LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

It were endless .... to give any Account of Mr.
Leeuwenhoek's Discoveries ; they are so numerous as to
make up a considerable Part of the Philosophical Trans-
actions, and when collected together, to fill four pretty
large Volumes in Quarto, which have been publish’d by
him at several Times: And of such Consequence, as to
have opened entirely new Scenes in some Parts of
Natural Philosophy, as we are all sensible, in that famous
Discovery of the Animalcula in Semine Masculino,' which
has given a perfectly new Turn to the Theory of
Generation, in almost all the Authors that have since
wrote upon that Subject.

But however excellent these Glasses may be jude’d,
Mr. Leeuwenhoek’s Discoveries are not entirely to be
imputed to their Goodness only: His own great
Judgment, and Experience in the Manner of using
them, together with the continual Application he gave
to that Business, and the indefatigable Industry with ,
which he contemplated often and long upon the same
Subject, viewing it under many and different Circum-
stances, cannot but have enabled him to form better
Judgments of the Nature of his Objects, and see farther
into their Constitution, than it can be imagined any
other Person can do, that neither has the Experience,
nor has taken the Pains this curious Author had so long
done.

Nor ought we to forget a Piece of Skill, in which he
very particularly excell’d, which was that of preparing
his Objects in the best Manner, to be view’d by the
Microscope; and of this I am perswaded, any one will be

* The discovery was announced in a letter written to the Royal Society
in November 1677—at the very moment when the marriage of William and
Mary was being celebrated in London.

2

Some further particulars of the microscopes themselves follow here:

ef. p. 317 wnfra.

FOLKES’S FINAL DISCOURSE 105

satisfied, who shall apply himself to the Examination of
some of the same Objects as do yet remain before these
Glasses ; at least, I have my self found so much Difficulty
in this Particular, as to observe a very sensible Difference
between the Appearances of the same Object, when
apply’d by my self, and when prepared by Mr.
Leeuwenhoek, tho’ view’d with Glasses of the very
same Goodness.

I have the rather insisted upon this, as it may be a
Caution to us, that we do not rashly condemn any of
this Gentleman’s Observations, tho’ even with his own
Glasses, we should not immediately be able to verify
them our selves. We are under very great Disadvantages
for want of the Experience he had, and he has himself
put us in Mind, more than once, that those who are the
best skill’d in the Use of Maenifying-Glasses, may be
misled, if they give too sudden a Judgment upon what
they see, or ’till they have been assured from repeated
Experiments. But we have seen so many, and those of
his most surprizing Discoveries, so perfectly confirm’d,
by great Numbers of the most curious and judicious
Observers, that there can surely be no Reason to distrust
his Accuracy in those others, which have not yet been so
frequently or carefully examin’d.

Upon the whole, it is to be hoped, some of the Society
will pursue those Enquiries, the late Possessor of these
Microscopes was so deservedly famous for; and that as
we have lost in Mr. Leeuwenhoek a most worthy Member,
and a most valuable Correspondent, this last Piece of his
Respect to the Royal Society will not only enrich our

Repository, but both encourage and enable
some other diligent Observer
to prosecute the same
curious and useful
Discoveries.

®

i
@

PART II

THE “LITTLE ANIMALS”

While ruder heads stand amazed at those
prodigious pieces of nature, as Elephants,
Dromidaries, and Camels ; these I confesse,
are the Colossus and Majestick pieces of
her hand; but in these narrow Engines
there is more curious Mathematicks, &
the civility of these little Citizens, more
nearly sets forth the wisdome of their
Maker.—Sir Thomas Browne (1642).

ae . ey 7 Te F . ; :
- an y ie a
ete A) ie th a ; :

; coe .

109

CHAPTER!

THE FIRST OBSERVATIONS ON “LITTLE ANIMALS”
(PROTOZOA AND BACTERIA) IN WATERS

(Letters 6, 13, 13a, 18, 188)

EEUWENHOEK’S observations on the free-living
le Protozoa probably began with his discovery of certain
“very little animalcules”’ which he saw in fresh water
in the year 1674. He described his findings in a letter
addressed to Mr. Oldenburg,’ and dated from Delft,
7 September 1674. This letter deals with other matters also,
and the passage in which the Protozoa are mentioned is quite
short. (See Plate XVII.) Here it is, in its entirety °:

About two hours distant ® from this Town there lies an
inland lake, called the Berkelse Mere, whose bottom in

‘ Henry Oldenburg, Secretary of the Royal Society. See p. 38.

2 Hrom Letter 6. 7 September 1674. MS.Roy.Soc. [Not in Dutch or
Latin collected works.] Part of this letter was translated and printed in
Phil. Trans., Vol. 1X, No. 108, pp. 178—182 [misprinted 821], 23 Nov.
1674. It is numbered “ [10] Brief Tr. 7’ by Vandevelde (1922, p. 344),
who gives an abstract of it in Flemish (from the Phil. Trans. version—not
from the MS.). The important passage given above has been generally
overlooked by protozoologists—possibly because the letter was omitted,
apparently by an oversight, from the table of contents at the beginning of
the number in which it was printed. The passage here given begins on
p. 181; and I have followed the original translation pretty closely, because
it is so lively and faithful. I havea strong feeling—but no direct evidence—
that it was not the work of Oldenburg himself: but I do not know who the
translator was. The English MS. has not been preserved.—I find since
writing the above that attention was directed to this passage—as fixing the
date of L.’s earliest observations—by Schill (1887), who reprinted the
original English version. His note has seemingly been overlooked by all
later writers.

® John Ray, in his Journey through the Low-countries, notes (anno 1663)
as a peculiarity that ‘ they reckon or measure their way in these Countreys,
by the time they spend in passing it” (Ray, 1673; p. 93).

110

1

LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

many places is very marshy, or boggy. Its water is in
winter very clear, but at the beginning or in the middle of
summer it becomes whitish, and there are then little
green clouds floating through it; which, according to the
saying of the country folk dwelling thereabout, is caused
by the dew, which happens to fall at that time, and which
they call honey-dew. This water is abounding in fish,
which is very good and savoury. Passing just lately’
over this lake, at a time when the wind blew pretty hard,
and seeing the water as above described, I took up a little
of it in a glass phial; and examining this water next day,
I found floating therein divers earthy particles, and some
green streaks, spirally wound serpent-wise, and orderly
arranged, alter the manner of the copper or tin worms,
which distillers use to cool their liquors as they distil
over. The whole circumference of each of these streaks
was about the thickness of a hair of one’s head. Other
particles had but the beginning of the foresaid streak ;
but all consisted of very small green globules joined
together: and there were very many small green globules
as well. Among these there were, besides, very many
little animalcules,’ whereof some were roundish, while
others, a bit bigger, consisted of an oval. On these last I
saw two little legs near the head, and two little fins at
the hindmost end of the body.* Others were somewhat
longer than an oval, and these were very slow a-moving,
and few in number.’ These animalcules had divers
colours, some being whitish and transparent; others

nu laest MS. The date of the observation is not more precisely stated,

but it seems clear that the discoveries must have been made in the late
summer (end of August or beginning of September ?) of 1674.

> The common green alga Spirogyra: the earliest recorded observations
on this organism. ‘The size of the filament negatives the suggestion that L.
could have been referring to Arthrospira or Spirulina.

* It can hardly be doubted that some, at least, of these animalcules were
Protozoa.

* Probably Rotifers—seen under a low magnification.

5

Probably Ciliates.

PLATE XVII

aoe ang Vewr ;LvrewecR Bee apes apr se =
eer 82d, Wot taset oon) Oy Ee j ow wee eronuk LI Galo}
Bate! ta Os care Vevee nee “Die Ventvy 6 Sacer ae ee ee
; L 3 ¥, gR Be i coast Vas eae ay
’ ig yok Went Iw obs oa
pes ea phe Aes pees Fae (ere Ceuta 225s)
Que Bar akdsed. das LET PES ray Tye day Dee oe NA AEG a

leer ae ae,

PIT OS bese ak 67 ote wd 9 a9) ent A L/
Chane Ss rr ee eae StS treme hy eh ae,
eee sae. SD BR. Casw Neen ous & Sue ae
made Le Seth Oem Yosh asd)J ae tll DabLaSY v2,

Sas Res coger ee ¥ g Sue J ceocotga5, af ye Safes Lense (20: a
rot «Coot Cul eee: Md , S2S~ Crovase R 0.94.9 on Srbey Book ao Gore.
ae Creme eee et OF 25, yi greet Cb Se / Otto a
BS Syrent + adie Casres ick ioe pa ae Ee
a DG wee a ee 5 B86 Lica dw, LaB9F Apo BLY Sal
aoe! Qoeent Ca. St) QAeinwKe Slo
: sth peeved tne; oie ee =

Gear i freed 3. (Oe ee yA eee $ ee a ee ics J.
ies a sae rick Sok At ; Cha ae foro SH % eae i wt Loe Gotse Ss
oy ov Goves ~ > Joe om RE, at ~a om a circle,
fet Ql oe ao an oon witae als ee AS) a SO hege IR VCnaKe

ats os A eoynseS VWoetgsns pont eee weet 7 one OS Rods CDI HSS

EXTRACT (REDUCED FACSIMILE) FROM LEEUWENHOEK’s LETTER NO. 6

(7 Sept. 1674: leaf 3 recto = p. 5), showing the original of the passage here
translated. Holograph MS. The concluding words are on the verso of the
page, and read: “.. . int tarwen meel, in schimmel, en etc. heb gesien.”
Apart from this unavoidable omission, the passage is complete.

facing p. 110

i 2H: hse sa pie ' i)
"a cher ae ee yey oy vn a i mk dw
He ‘i ne A ‘e
ND i uate if hy ok ’
ene f

yi ah |
n oa gh ae)

AY -” habs
‘

LETTERS 6 AND 13 EEE

with green and very glittering little scales; others again
were green in the middle, and before and behind white’ ;
others yet were ashen grey. And the motion of most of
these animalcules in the water was so swift, and so
various, upwards, downwards, and round about, that ’twas
wonderful to see: and I judge that some of these little
creatures were above a thousand times smaller” than the
smallest ones I, have ever yet seen,’ upon the rind of
cheese, in wheaten flour, mould, and the like.

No further observations on these ‘little animals” appear
to have been reported until more than a year later. But in a
letter written in December, 1675, Leeuwenhoek again alludes
to them briefly, in the following words :*

In the past summer I have made many observations
upon various waters, and in almost all discovered an
abundance of very little and odd animalcules, whereof
some were incredibly small, less even than the animalcules
which others have discovered in water, and which have
been called’ by the name of Water-flea, or Water-louse.

This passage is important as establishing the date when
some of Leeuwenhoek’s earliest observations were made—the
summer of 1675. At this time, however, he gave no more
detailed account of his discoveries: but he kept a careful
record, and a month later the following passage occurs in a
further note to Oldenburg :°

* Probably Euglena viridis. The peculiar arrangement of the chromato-
phores in this species gives the flagellate this appearance under a low
magnification. The identification seems to me almost certain; and, if
correct, this is the first mention of Huglena, whose discovery is usually
attributed to Harris (1696).

> i.e., in volume—not in linear dimensions.

* i.e., mites.

* From Letter 13. 20 December 1675. MS.Roy.Soc. Unpublished.
Original in Dutch.

* By Swammerdam. See note 1 on p. 118.

° From Letter 13a. 22 January 1676. MS.Roy.Soc. Unpublished.
Original in Dutch.

‘cé

12 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

The living creatures discovered by me in water, were
in ordinary rain-water, that was caught from a pantile
roof’ in stone troughs under the ground, or in tubs; also
in well or spring water, coming up through well-sand ;
likewise in the canal water, that runneth through this
Town and through the country. Upon these I have
made divers notes, concerning their colour, figure, the parts
whereof their body is composed, their motion, and the
sudden bursting of their whole body; of which notes I
keep a copy by me, which I shall send you at the earliest
opportunity.

The promised ‘“ notes”? were sent in due course: they form
the celebrated letter (Letter 18) which protozoologists have
long regarded as the first paper ever written upon the objects
of their special study. Moreover, this letter also contains the
first account ever written of the Bacteria, as well as many
other original observations. In view of its unique interest,
therefore, I must say a few further words of introduction at
this point.

Leeuwenhoek’s 18th Letter.

The famous “ Letter on the Protozoa” is a truly amazing
document. According to my reckoning it is Leeuwenhoek’s
eighteenth scientific epistle to the Royal Society, and I shall
therefore refer to it henceforward simply as Letter 18. The
original Letter itself is preserved among the Royal Society’s
manuscripts, and is still—except for a few slight mutilations—
intact. It is in Dutch, and covers 17} folio pages, closely
written in a neat small hand which is not Leeuwenhoek’s own,
though the manuscript has been carefully corrected by him
throughout (in a different ink), and bears his autograph
signature at the end. It seems likely that he wrote the letter
himself, with his notebook before him, and then caused his

1 The water so collected was probably very clean water: for Dutch
houses then—as now—were wont to be kept clean both inside and out.
John Ray, in the diary of his Travels—writing in 1663—notes that, in the
Netherlands, ‘‘all things both within and without” were “ marvellously
clean, bright, and handsomly kept: nay some are so extraordinarily curious
as to take down the very Tiles of their Pent-houses and cleanse them.”
Vide Ray (1673), p. 52.

j . , na
ay rev 7 "
. : une } i
| i : oe Ne
PEG Samrat Le ale
eg ni i . -_ x shea! dia is Dat seen
mee ee ’ by AT sire a ty Le . .
ri. : a TY Aya oe Dials, © Fyne EBL Sannin wt ie.

fs ch ne a} 4 Fain ak uv
Wahid ey a ae we’ 4 rhs iv ey ah Anes f ee | Aa . as Ma am 7
: ¥ ; q, hi mh . : : a a rr a ae a

o a - Ba. i Ve ma 7 7 “tae - : “ae : i Ly roa ‘ ih, hoy rit } ; oe a 7
: ay tak - eee! ts é oy 5 : io f ft ’ ‘al le 8 : . { r j '

I i 5
7 aa i f ui : ; ee Tee He
Or Ol a a gree Le vp

res : y ee i : — Yad we” He ; , iv) er ; ose a v Pau * 7 . 1

¢ 7 - ye : ait @ : : “a
mh fe eee ae Une dh a ye, Py eis of ald ; ‘an
al’ ep eret OR eo .
J I ' i it ° ; ay :
-_ <3 4” uy : | Lt. Pot) eee * ate |
ad 14 i 7s ar 7 Daa) Whos 7 ’ ry o
aay ¥ 7 t fae a - A i ae 1s ™) ma tint

. es an Big Bas o's m0 | ae
mt > | n - YY iY ; A iP aK phn - W fl 1 { : - .
et eR yl iy lel! . vane itty ene Tit m1 “be
Tia pp WPMD ih FAP. a! i De HI -
Ww A . \ oanty iin i am ah, ee Wades i t Vi - 7 @%' A.
nie: ans ona ye ’} 7 1 fie any PP ho © ’ ee
a epieme ty) Se : . a | vite ae irs mn ea
ie ear "a Tr i ; — Sean re ) ri 7 i : i
S a a Ae vy : _) : ’ ; ws " 7 a _ aera 4 i. Z < a. tr. eri’ a
:
; oa _ ie | i. ay a ; fa poe : 7 fe =). i f ' / a q:
Aa Vide H ee ae! i a i. . ‘ ‘a >
a oars ed on hae ay Spe" ok OY ng,
ry Bein?! Ah or Ser vs oa The th ge
wile boy Pat a ous ia ped eee meal
ot “ > an rn ides a oe Mu x tin

a
. a eee ina
yk NSE INNG i
, ae i | a La is
Se Wilt Hi Be beaut Ka
i. A ont
wy |

‘ Faun, deine

PLATE XVIII
( $2r.)

Obfervations communicated to the Publier by Mr. Antony van
Leewenhoeck, én 4 Dutch Letter of the 9th of O&ob. 1676,
here Englify’d: Concerning little Animals by hire obferved in
Rain- Welle Sea- and Snow-water ; as alfo in water wherein
Pepper hadlain infufed.

N the year 1675.1 difcover’d living creatures in Ra'n water,
which had ftood but few days in anew earthen pot, glafed
blew within, This invited me to view this water with great at-
cention,efpecially thofe little animals appearing to me cen thou-
fand times lefs than thofe reprefented by Monf. Swamerdam,
and by him called Water-fleas or Water-dice, which may be per-

ceived in the water with the naked eye, 3
The fir fore by me difcover’d in the faid water, I divers

times obferved to confit of 5, 6,7, or 8 clear globuis, without

being able to difcern any film that held them together, or con-
tained them. When thefe amimaicula or living Atoms did move,
they put forth two little horns,continually moving themfelves:

The place between thefe two horns was flat, though the reft of

the body was roundifh,fharpning a little towards che end,where

they hada tayl, near four timesithe length of the whole body,of
the thicknefs (by my Microfcope) ofa Spiders-web ; at the end
of which appear’d a globul, of the bignefs of one of thofe which
made up the body; which tayi I could not perceive,even in ve-
ry clear water, to be mov’d by them. Thefe little creatures, if
they chanced to light upon the leait filament or ftring,or other
fuch particle, of which there are many in water,ef{pecially after
it hath ftood fome days, they {tock intangled cherein,extending
their body ina long round, and ftriving to dif-intangle their
tay] ; whereby it came to pafs, that their whole body lept back
towards the globul of the tay], which then rolled together Ser-
pent-like, and after the manner of Copper- or Iron-wire that
having been wound abouta ftick, and unwound again, retains
thofe windings and turnings. This motion of extenfion and
contraétion continued a while; and I have feen feveral hun-
dreds of thefe poor little creatures, within the fpace of a grain
of profs fand, lye faft clufter’d together ina few filaments.
Lalfo difcover’d a fecond fort, the figure of which was ova! ;
and I imagined their head to ftand on the tharp end.Thefe were

a little bigger than the former. The inferior part of their body

is flat, furnifhed with divers incredibly thin feet, which pyar

FIRST PAGE (FACSIMILE) OF OLDENBURG'S TRANSLATION OF LETTER 18

(9 Oct. 1676) published in Phil. Trans. (1677), Vol. XII, No. 183,

pp. 821-831. Compare with Plate XIX.
facing p. 1138

INTRODUCTION TO LETTER 18 113

rough draft to be copied out in a fair hand before sending it to
the Society. The letter is dated from ‘ Delft in Holland, 9th
October, 1676”’ [New Style], and is addressed to Henry
Oldenburg in person. From an endorsement which it bears’
it appears that he received it 10 days later, and sent back an
acknowledgement of its receipt through Leibniz. The letter
was read at the meetings of the Royal Society held on 1, 16,
and 22 February 1677 [O.S. ].’

A part of this letter was published (in English) in the
Philosophical Transactions in March, 1677,’ under the heading
“ Observations, communicated to the Publisher * by Mr. Antony
van Leewenhoeck, in a Dutch Letter of the 9th of Octob. 1676.
here English’d: Concerning little Animals by him observed in
Rain- Well- Sea- and Snow-water; as also in water wherein
Pepper had lain infused”. (See Plate XVIII.) This English
version was the work of Oldenburg himself, as is evident from
the manuscript translation—in his hand—still preserved with
its Dutch original.

Oldenburg’s English rendering is the only version of
Letter 18 which has hitherto been printed. It is, on the
whole, good: but it is not perfect, and most people will be
surprised to learn that it is a condensed translation of less
than half of the original, and that the part which Oldenburg
did not print has never yet been published in any language.
Why the letter has never been published, in its entirety, I do
not know. I can only suppose that no protozoologist or
bacteriologist has ever yet seen the original manuscript; or,
having seen it, has had the courage and diligence to decipher

1 The endorsement—in Oldenburg’s hand—is as follows: “recew le 9.
Octob. st. v. [=style vieux] 1676. resp[ondu]. le 16 Oct. d’avoir receu
cette lettre, par M. Leibnitz, mais non pas encor consideré”’.—It was in the
autumn of 1676 that Leibniz paid his now well-known (but formerly hushed-
up) visit to Spinoza at The Hague (cf. Pollock, 1899; p. 37). Perhaps
Oldenburg, knowing this interview to be imminent, requested Leibniz to send
word to L.—only a few miles distant at Delft—of the safe receipt of his
letter. I can find no evidence to show that Leibniz visited Leeuwenhoek
on this occasion.—The well-known correspondence between L. and Leibniz
took place, of course, at a much later date, and has been already reviewed
by Ehrenberg (1845).

2 Cf. Birch, Vol. III, pp. 332, 333, 334.
* Phil. Trans. (1677), Vol. XII, No. 133, pp. 821-831.
* “Publisher”? = Editor (¢.e. Oldenburg).

8

114 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS”

it. It certainly is not very easy to read; but considering its
supreme interest and importance, I am astonished that nobody
hitherto appears to have made the attempt—nobody, that is,
since Oldenburg: for Oldenburg evidently read the whole
letter, and, though he published but a part, translated most
of it—after a fashion. I have been through his manuscript
translation carefully, but I have made no use of it in the
preparation of my own: for it is much too abbreviated and
confused for my purpose, and it is not free from errors.
Oldenburg seems to have had a fair knowledge of Dutch, but
the objects which Leeuwenhoek was endeavouring to describe
were, of course, at that time entirely outside the experience
of everybody but himself: and to understand his words, and
to appreciate his efforts at description, it is necessary to be
familiar with the things that he was studying as well as with
his way of writing.

Many protozoologists have, no doubt, read Oldenburg’s
curtailed English version of Letter 18 in the Philosophical
Transactions, but probably many more are acquainted with it
through the work of Saville Kent. This author copied a
considerable part of the letter into his well-known book on
the ‘“ Infusoria’”’!; but I must remark that his quotations from
Oldenburg’s translation do not altogether bear out his own
statement that they were transcribed “with a faithful
reproduction of their original quaint style of diction”. Kent's
version is, indeed, by no means faithful to its prototype, and
even contains several bad mistakes. For example, in one
place Leeuwenhoek says that he put some water in a glass
“on mijn comptoir’’—meaning “in my closet,” z.e. the office
or study”? in which he worked and wrote (probably the
counting-house in his shop). This frequently recurring phrase
is usually rendered ‘“‘in musaeo meo”’ by the Latin translators,
and appears—concordantly —as “dans mon cabinet” in the

* Manual of the Infusoria (1880). Vol. I, pp. 3-7.—I may also note
here that what purports to be another reproduction of the same letter,
published recently by Knickerbocker (1927), is nothing more than a reprint
of the garbled and condensed version printed in 1809 by Hutton, Shaw,
and Pearson in their Abridgement of the Phil. Trans. It has no value either
as a historical document or as an illustration of L.’s work.

* Comptoir = reekenkamer, schrijfkamer, etc. (Meijer, Woordenschat p. 56).
spe particulars regarding L.’s “ comptoir ” are given in Letter 16 (p. 125
infra).

LETTER 18: OTHER VERSIONS 1S

short French version of Chr. Huygens.’ Oldenburg rightly
translated it ‘in my Counter’ or Study ’’—evidently being at
a loss for the exact English equivalent of the Franco-Dutch
word. But Kent, by “copying” Oldenburg, ultimately gives
us “on my counter of study’’—an unintelligible expression
which he perhaps imagined to mean “on my laboratory
bench ”’.*

On 7 November 1676, a month after he had sent his long
letter to the Royal Society, Leeuwenhoek wrote a much
shorter account of the same observations to his old friend
Sir Constantijn Huygens—the statesman-poet father of
Christiaan, the famous astronomer and mathematician. This
letter *is preserved at Leyden, and has recently been published
by Vandevelde and van Seters (1925). At Leeuwenhoek’s
request it was translated into French by Christiaan Huygens
—then at Paris—whose MS. translation is also now in the
Leyden University Library along with its Dutch original.
This French version was evidently intended for presentation
to the Paris Academy: but another French abstract or
summary of Leeuwenhoek’s observations was printed in the
Journal des Scavans some two years later,’ and the translation
made by Huygens has only recently been published in
Holland.° These various abstracts give but a poor idea of

™ See note 6 below.

> i.e. Counting-house (reekenkamer).

° I regret to say that at least one modern Dutch translator and one
Flemish commentator have fallen into the same error. They should both
have known better.

* Letter 18b, according to my numeration. Referred to by Haaxman
(1875), p.135. Snelleman (1874) has printed a part of this letter, in the
original Dutch, but his version contains several manifest misreadings which
Vandevelde and van Seters have rectified. I have carefully compared the
(published) letter of 7 Nov. 1676 with Letter 18, and it is obvious that it is
merely a very condensed account (not half the length) of the latter. It
contains nothing that is not more fully given in the original (Letter 18,
9 Oct. 1676) addressed to the Royal Society. The comparison instituted by
Vandevelde and van Seters between the French and Dutch abstracts and
Oldenburg’s short English version seems somewhat unprofitable, since they
never consulted the Dutch original in extenso (Letter 18).

> Journ. d. Scav., Vol. IX. 1678 (pp. 55 and 68 of nouv. éd., 1724).

° Gwores Completes de Chr. Huygens (1899), Vol. VIII, pp. 22-27
(No. 2100).

116 LEEUWENHOEK AND HIS “LITTLE ANIMALS”

the extensive investigations described in the original Dutch
epistle (Letter 18).

The greater part of this very long letter—one of the
longest Leeuwenhoek ever wrote—is in an unusual form. At
the very end of it he remarks that “these my observations”
are “ taken from the diary which I keep from time to time;”
and accordingly we find that he generally gives, in order, the
observations as he made them from day to day—without
making any attempt to summarize or correlate them. In his
letter to Constantijn Huygens (7 Nov. 1676) he explains that
he sent these details from his notebook “ merely so as to make
my observations more credible in England and elsewhere; and
especially because Mr Secretary Oldenburg had formerly
written to me that there are a number of philosophers at Paris
and elsewhere who don’t allow of the truth of what I
describe”*. The subject-matter falls naturally, as will be
seen, into various sections, dealing with the divers creatures
found in the several sorts of water or infusions which he
examined. Some of these sections are provided, by himself,
with appropriate headings, while others are not: and I have
therefore, for the sake of uniformity, interpolated such
headings where they are lacking in the original.’

Leeuwenhoek’s 18th Letter opens (cf. Plate XIX) with a
few personal remarks, of no particular interest in the present
connexion, and then drops abruptly into the description of his
discoveries: and at this point I have begun my translation,
which now follows.*

* Another French translation (or a copy of one of the two mentioned
above ?) was published later in a work called Collection Académique de Dijon,
Vol. II, pp. 454-461, 1755: but this I have not been able to consult. Cf.
Konarski (1895, p. 251 note) and Vandevelde (1922, p.349)—No account of
these observations appears to have been published in the Acta Hruditorum,
which only began publication in 1682: but a reference to L., and the
discovery of animalcules in infusions (attributed ambiguously to Butterfield),
will be found in the note by Elsholz (1679) in Miscellanea Curiosa, Vol. IX.

* See Vandevelde and van Seters (1925), p.20: and Guvres Compl. de
Chr. Huygens (1899), Vol. VIII, p. 22, footnote 3.

* These additions, wherever they occur, are indicated by being inclosed
between square brackets.

* Letter 18. 9 October 1676. To Oldenburg. MS. Roy. Soc. I have
not thought it necessary to mark all the places where my translation differs

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LETTER 18. 9 OCTOBER 1676 TL

[1st Observation on Rain-water. |

In the year 1675, about half-way through September '
(being busy with studying air, when I had much compressed
it by means of water”), I discovered living creatures
in rain, which had stood but a few days® in a new tub,
that was painted blue within.* This observation provoked
me to investigate this water more narrowly; and especially
because these little animals were, to my eye, more than
ten thousand times smaller’ than the animalcule which
Swammerdam ° has portrayed, and called by the name of

from Oldenburg’s, nor yet to point out all his many minor omissions.
These will be manifest to anybody who will take the trouble to compare
this rendering with that in the Phil. Trans. Only important errors,
interesting variants, or vital omissions, are indicated in my notes.—
Vandevelde (1922, p. 348) numbers this letter ‘ [15] Brief Tr. 11,” but it
certainly cannot be called ‘‘ Letter 11” or 15” in any sense.—The letter
is not to be found, of course, in either the Dutch or the Latin edition of the
collective works.

* In den gare 1675 ontrent half September MS. “In the year 1675”
Phil. Trans. By neglecting to translate the latter part of the original
statement, Oldenburg left the precise date of the discovery in doubt; and
a controversy arose later between Ehrenberg and Haaxman in consequence—
the former alleging that the observations were made in April, while the
latter, on evidence furnished by the MS. letter from L. to Const. Huygens,
believed the correct date to be mid-September. Cf. Haaxman (1875). It
is now obvious that Haaxman was right.

> Some account of L.’s experiments “on the compression of the air”
had already appeared in Phil. Trans. (1673), Vol. IX, p. 21. (Letter 2,
15 August 1673. MS. Roy.Soc.)

* “four days”’ Saville Kent (Vol. I, p. 3). This is merely due to careless
copying, and is not in the originals.

. . . . be
* in een nieuwe ton, die van binnen blaww geverft was MS. in a new

earthen pot, glased blew within’ Phil. Trans. Oldenburg here mis-
translated L.’s words, which were quite plain and were rendered concordantly
by Chr. Huygens “dans un tonneau peint en huile par dedans’”’. The vessel
was obviously not of Delft porcelain.

° ¢.e., in bulk—not in diameter. This expression means, with L., that
he judged the animalcules to have roughly one twenty-fifth of the diameter
of the bigger creatures.

® Jan Swammerdam (1637—1680). For his life see especially his
Biblia Naturae (1737) and Sinia (1878).

118 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS”

Water-flea, or Water-louse,’ which you can see alive and
moving in water with the bare eye.

Of the first sort that I discovered in the said water, I
saw, after divers observations, that the bodies consisted
of 5, 6, 7, or 8 very clear globules, but without being able
to discern any membrane or skin that held these globules
together, or in which they were inclosed. When these
animalcules bestirred ’emselves, they sometimes stuck
out two little horns,’ which were continually moved, after
the fashion of a horse’s ears. The part between these
little horns was flat, their body else being roundish, save
only that it ran somewhat to a point at the hind end; at
which pointed end it had a tail, near four times as long
as the whole body, and looking as thick, when viewed
through my microscope, as a spider’s web.* At the end
of this tail there was a pellet, of the bigness of one of the
globules of the body; and this tail I could not perceive
to be used by them for their movements in very clear
water. These little animals were the most wretched
creatures that I have ever seen; for when, with the
pellet, they did but hit on any particles or little filaments °
(of which there are many in water, especially if it hath

* Swammerdam’s “ watervlooy’”’ was Daphnia—as all students of the
Biblia Naturae are well aware (cf. B.N. Vol. I, p. 86, Pl. XX XI). But as this
work was not published until 1737—long after his death—it is clear that
L. here alludes to his earlier Dutch publication (Swammerdam, 1669), in
which the water-flea is shown on Pl. I. Swammerdam himself called it
“the branched water-flea”’, and attributed the name ‘‘ water-louse’’ to
Goedaert.

> Vorticella sp. The following admirable description makes the
identification certain.

* The optical section of the wreath of cilia round the peristome—so
interpreted by most of the early observers.

* i.e., as thick as a spider’s web looks to the naked eye.

a9

> maer quamen aen eenige deeltgens of veseltgens MS. ° if they chanced
to light upon the least filament or string, or other such particle’? Phil.
Trans. These words of Oldenburg are amusingly mistranslated by Nagler
(1918, p. 7) ““ Wenn man diese kleinen Kreaturen Zufallig belichtete.” (He
apparently supposes that “ to light upon’”’ means “‘ to illuminate ” ! )

LETTER 18. RAIN-WATER 119

but stood some days), they stuck intangled in them; and
then pulled their body out into an oval, and did struggle,
by strongly stretching themselves, to get their tail loose ;
whereby their whole body then sprang back towards the
pellet of the tail, and their tails then coiled up serpent-
wise, after the fashion of a copper or iron wire that,
having been wound close about a round stick, and then
taken off, kept all its windings.’ This motion, of stretch-
ing out and pulling together the tail, continued; and I
have seen several hundred animalcules, caught fast by
one another in a few filaments, lying within the compass
of a coarse grain of sand.”

I also discovered a second sort* of animalcules, whose
figure was an oval; and I imagined that their head was
placed at the pointed end. These were a little bit bigger
than the animalcules first mentioned. ‘Their belly is flat,
provided with divers incredibly thin little feet, or little
legs,* which were moved very nimbly, and which I was
able to discover only after sundry great efforts, and where-
with they brought off incredibly quick motions. The
upper part of their body was round, and furnished inside
with 8, 10, or 12 globules: otherwise these animalcules

* Apparently it never occurred to L., at this time, that the contraction
and extension of the stalk (“tail’’) of Vorticella could have any other
significance than that here attributed to them. The idea of a stalked and
normally sessile animal probably never entered his head; and consequently
he jumped to the incorrect conclusion that the animals were endeavouring
to “ get their tails loose ’’—which, of course, was a mistake, though a very
natural one. lL. published pictures of Vorticellids later, in Phil. Trans.,
Vol. XXIII (Letter dated 25 Dec. 1702): and still later he arrived at a
more correct interpretation of the function of the “tail,” and of the
organization of these remarkable animals (Send-brief VII, dated 28 June
1713). See Chapter 4, below.

* inde spatie van een grof sant MS. “ within the space of a grain of gross
sand” Phil. Trans. This is a very common expression with L., and
Oldenburg fully understood its meaning ; but Nagler (1918, p. 9) mistranslates
his words “in der Héhlung eines grossen Sandkorns’’—as though L. had seen
the animalcules lying in a cavity in an actual grain of sand!

* Not identifiable with certainty, but undoubtedly a ciliate.

y Ve ey:
2.e. cilia.

120

LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS”

were very clear. These little animals would change their
body into a perfect round, but mostly when they came to
lie high and dry. Their body was also very yielding: for
if they so much as brushed against a tiny filament, their
body bent in, which bend also presently sprang out again ;
just as if you stuck your finger into a bladder full of
water, and then, on removing the finger, the inpitting
went away. Yet the greatest marvel was when I brought
any of the animalcules on a dry place, for I then saw
them change themselves at last into a round, and then the
upper part of the body rose up pyramid-like, with a point
jutting out in the middle; and after having thus lain
moving with their feet for a little while, they burst
asunder, and the globules and a watery humour flowed
away on all sides, without my being able to discern even
the least sign of any skin wherein these globules and the
liquid had, to all appearance, been inclosed ; and at such
times I could discern more globules than when they were
alive. This bursting asunder I figure to myself to happen
thus: imagine, for example, that you have a sheep’s
bladder filled with shot, peas, and water; then, if you
were to dash it apieces on the ground, the shot, peas, and
water would scatter themselves all over the place.’

Furthermore, I discovered a third sort’ of little
animals, that were about twice as long as broad, and to
my eye quite eight times smaller* than the animalcules
first mentioned: and I imagined, although they were so
small, that I could yet make out their little legs, or little
fins. Their motion was very quick, both roundabout and
in a straight line.

ee ee

* The foregoing graphic account of the bursting of the “ little animals” is
of great interest, as it shows clearly that L. was really observing protozoa.
An animal whose body consisted entirely of soft ‘‘ protoplasm ”—without any
skeletal parts or obvious skin—was, of course, a considerable novelty at this

date.

2

Not identifiable. Probably a small ciliate.

* «.e., having a diameter equal to about half that of the Vorticella.

LETTER 18. RAIN-WATER 121

The fourth sort! of animalcules, which I also saw
a-moving, were so small, that for my part I can’t assign
any figure to em. These little animals were more than
a thousand times less than the eye of a full-grown
louse? (for I judge the diameter of the louse’s eye to be
more than ten times as long as that of the said creature),
and they surpassed in quickness the animalcules already
spoken of. I have divers times seen them standing still,
as ’twere, in one spot, and twirling themselves round
with a swiftness such as you see in a whip-top a-spinning
before your eye*; and then again they had a circular
motion, the circumference whereof was no bigger than
that of a small sand-grain; and anon they would go
straight ahead, or their course would be crooked."

Furthermore, I also discovered sundry other sorts of
little animals; but these were very big, some as large as
the little mites on the rind of cheese, others bigger and
very monstrous.’ But I intend not to specify them ; and

1 Probably—from the ensuing description—a species of Monas. Certainly
not bacteria of any kind.

2 This makes the diameter of the protozoon here described about 6-8 p,
and is agreeable with its interpretation as Monas vulgaris.

? If the description applies to Monas—as I strongly suspect—then the
“spinning” here described was an illusion. I fancy L. saw a Monas attached
by its caudal filament, and mistook the swirl of the water at its anterior
end (occasioned by the movements of the small accessory flagellum) for a
motion caused by the rotation of the body as a whole.

4 on dan weder soo regt wijt, als crom gebogen MS. These words are hard
to understand. The above seems to me to be L.’s meaning : but Oldenburg
translates ‘and then extending themselves streight forward, and by and by
lying in a bending posture ”’ (Phil. Trans.). It is hardly likely that L. could
have observed “a bending posture”’ in an organism so small that he could
discern “ no figure” in it: and as the “circular motion” just mentioned
evidently refers to the orbit described by the organism—not to the
animalcule itself—I imagine that ‘‘regt wijt’” and “‘ crom gebogen” likewise
refer to the path traversed. I should point out, however, that L. elsewhere
(Letter 38) applies precisely the same words to the shape of the spermatozoa
of a frog.

® Some of these were doubtless protozoa, but the “ monsters’ were
perhaps rotifers. Much later, when describing these animals, L. mentions
that he had previously discovered them in rain-water, in which he had
steeped pepper and ginger. See Letter 144, 9 Feb. 1702.

122 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS ”’

will only say, that they were for the most part made up
of such soft parts, that they burst asunder whenever the
water happened to run off them.

The 2nd Observation. [Rain-water.]

The 26th of May,’ it rained very hard. The rain
abating somewhat, I took a clean glass and got
rain-water, that came off a slate roof, fetched me in it,
after the glass had first been swilled out two or three
times with the rain-water. I then examined it, and
therein discovered some few very little animals’; and
seeing them, I bethought me whether they might not
have been bred in the leaden gutters, in any water that
might erstwhile have been standing in them.

The 3rd Observation. Rain-water.

On the same date, the rain continuing nearly the
whole day, I took a big porcelain dish, and put it in
my court-yard, in the open air, upon a wooden tub
about a foot and a half high: considering that thus no
earthy particles would be splashed into the said dish by
the falling of the rain at that spot. With the water
first caught, I swilled out the dish, and the glass in
which I meant to preserve the water, and then flung this
water away: then, collecting water anew in the same
dish, I kept it; but upon examining it, I could discover
therein no living creatures, but merely a lot of irregular
earthy particles.

The 30th of May, after I had, since the 26th, observed
this water every day, twice or thrice daily, I now first
discovered some (though very few) exceeding little
animalcules,* which were very clear.

* Anno 1676.

* Unidentifiable. The animalcules from L.’s gutters were described by
himself later. (Cf. p. 263 infra.) They include flagellates, ciliates, bacteria,
and rotifers.

* From the description which follows, these were probably the same
as the “ very little animalcules”’ already described—.e., a species of Monas.

LETTER 18. RAIN-WATER 123

On the 31st ditto, I discovered more little animals in
the water, as well as a few that were a bit bigger; and I
imagine that ten hundred thousand of these very little
animalcules are not so big as an ordinary sand-grain.’
Comparing these animalcules with the little mites in cheese
(which you can see a-moving with the bare eye), I would
put the proportion thus: As the size of a’small animalcule
in the water is to that of a mite, so is the size of a honey-
bee to that of a horse; for the circumference of one of
these same little animalcules is not so great as the thick-
ness of a hair on a mite.

The 4th Observation. Rain-water.

On June 9th,’ collected rain-water betimes in a dish, as
aforesaid, and put it at about 8 o’clock in the morning in
a clean wine-glass, and exposed it to the air at about the
height of the third storey of my house, wondering whether
the little animals would appear sooner in water thus
standing in the air.

The 10th ditto, observing this water, I fancied that I
discovered living creatures; but because they were so
few, and not so plainly discernible, I could not accept
this for the truth.

On the 11th ditto, seeing this water, with the naked
eye, stirred in the glass by a stiff gale of wind (which had
now blown from the same quarter for 36 hours; the
weather being so cold withal, that it did not irk me to
wear my winter clothes), I had no thought of finding any
living creatures in it; but upon examining it, I saw with
wonder quite 1000 living creatures in one drop of water.

‘This means that he estimated their diameter at something less than
zdo of the diameter of an “ordinary” (or large) sand-grain. Taking this
as 35 of an inch, their diameter would thus be of the order of so00 in., or
roughly 8°5. This is a very close guess at the size of Monas vulgaris. On
sand-grains cf. p. 334 fra.

? Anno 1676.

124 LEEUWENHOEK AND HIS “LITTLE ANIMALS”’

These animalcules were of the smallest sort’ that I had
as yet seen.

The 12th of June, in the morning (the wind being west,
with both sunshine and an overcast sky), observing again,
I saw the foresaid animalcules in such great numbers in
the water which I took from the surface, that now they
did not amount to merely one or two thousand in one
drop.

The 13th ditto, in the morning, examining the water
again, I discovered, besides the foresaid animalcules, a
sort of little animals that were fully eight times as big’
as the first; and whereas the small animalcules swam
gently among one another, and moved after the fashion
of gnats in the air, these large animalcules had a much
swifter motion; and as they turned and tumbled all
around and about, they would make a quick dart.°®
These animalcules were almost round. *

On the 14th of June I did perceive the very little
animalcules in no less number.

On the 16th ditto, the animalcules seen as before; and
the water (which had been, in all, about 4 of a pint)
being now more than half dried up, I flung it away.

5th Observation. Rain-water.

The 9th of June,’ I put some of the last-collected
water, likewise in a clean wine-glass, in my closet; and

*4.e., probably Monas sp. again.
? On L.’s system this means “ twice as long”.

= nmamen deselve een snelle scheut MS. “and then making a sudden
downfall”? Phil. Trans. L.’s meaning seems clearly to be that given above
(i.e., they sometimes made sudden shoots or darts forward). Oldenburg
renders his words as though scheut = Fr. chute.

4 It seems to me almost certain that the animalcule here described was
the common ciliate Cyclidiwm. This is the only likely organism—of this
order of magnitude—which makes sudden springs (hence its name of “ flea-
animalcule”’). The only objection to this interpretation is the statement
that it was ‘‘almost round’’: but it must be remembered that L. made
his observations under a very inadequate magnification.

> Anno 1676.

iat int ‘ag FY eo
ay Oi

by set) Gains

re

PLATE XX

Rijksmuseum

Amsterdam
A HOUSE IN DELFT

From the picture by Jan Vermeer (1632-1675). This three-storey house is
probably very like the one in which Leeuwenhoek lived. The picture shows
the casement windows, with their leaded panes and wooden shutters, and
an alleyway leading to the yard at the back (where the well was situated) :

only the canal in front of the house is not shown below the cobbled
pavement in the foreground.

facing p. 125

LETTER 18. RAIN-WATER 125

on examining it, I descried no animalcules. (Note. My
closet standeth towards the north-east,’ and is parti-
tioned off from my antechamber with pine-wood, very
close joined, having no other opening than a slit an inch
and a half high and 8 inches long, through which the
wooden spring of my lathe passeth. ‘Tis furnished
towards the street with four windows, whereof the two
lowermost can be opened from within, and which by
night are closed outside with two wooden shutters; so
that little or no air comes in from without, unless it
chance that in making my observations I use a candle,
when I draw up one casement a little, lest the candle
inconvenience me; and I also then pull a curtain almost:
right across the panes.)

The 10th of June, observing this foresaid rain-water,
which had now stood about 24 hours in my closet, I
perceived some few very little living creatures,’ to which,
because of their littleness, no figure can be ascribed; and
among others, I discovered a little animal that was a bit
bigger, and that I could perceive to be oval.* (Note.
When I say that I have observed the water, I mean I
have examined no more than 3, 4, or 5 drops thereof,
which I also then throw away; and in narrowly
scrutinizing 3 or 4 drops I may do such a deal of work,
that I put myself into a sweat.)

' From the situation of the house, this indicates that the “ closet”? was
at the front, looking on to the canal in the Hippolytusbuurt.—Plate XX is
inserted here to show the sort of house which L. probably lived in, and to
illustrate what he means by fowr windows with two wooden shutters over
the lowermost. (This picture may conceivably have been painted from L.’s
own house—or Vermeer’s!) Although the original painting (formerly in
the Six Collection, now in the Rijksmuseum) is now known as Het Straatje
(= The Little Street), it appears to have been more correctly described as
“A View of a House in Delft” in the catalogue of the sale of Vermeer’s
pictures at Amsterdam in 1696.

* Probably Monas (or Cercomonas): see below.

* From the observations recorded later, it appears probable that the
organism was a ciliate; but its very small size is against this interpretation.
It may have been a Cyclidiwm.

126

LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

The 11th ditto, observing this water again, I saw the
foresaid small animalcules, though very few in number.

The 12th ditto, I saw the very small animalcules, as
yesterday ; and besides these, a little animal’ that had
nearly the figure of a mussel-shell, lying with its hollow
side downwards. “T'was of a length anigh that of a
louse’s eye.”

The 13th ditto, in the morning, I found the said very
small animalcules in greater number, and I saw also one
bigger animalcule, like that just spoken of.” The same
day, in the evening, I perceived the said very small
animalcules again in no less number; and I could now
see that they had a clear or transparent projection at the
hind end of their body.* Moreover I discovered animal-
cules which were somewhat longer than an oval.’ These
were about 6 times as long as the foresaid very small
animalcules ; and their head, which was somewhat long
drawn out, they oft-times pulled in, and then looked to
be almost round. ‘There were also animalcules’ which
appeared perfectly round, their diameter being twice as
long as that of the smallest animalcules of all. These
two large sorts were very yielding, so that their body did
bend before the least little filament which they chanced
to brush against in the water.

The 14th ditto, I perceived the oval animalcules in
greater number.’

' Traditionally—and doubtless with justice—identifiable as Stylonychia
mytilus (O.F.M.) Ehrbg., a common hypotrichous ciliate.

* That is, about 70m. See p. 336.
*ie., Stylonychia.

* Probably Monas again—or perhaps a Cercomonas.

® From the description which follows it seems probable that these were
Dileptus sp., but it is impossible to identify them with certainty.

© Perhaps Cyclidiwm again — similarly described on June 13 (4th
observation).

7This apparently refers to the oval animalcules seen on the 10th
(2 Cyclidiwm).

LETTER 18. RAIN-WATER 127

The 16th ditto, I perceived the oval animalcules in yet
greater numbers; and they were flat beneath, and round
above: and besides these, there were very small animal-
cules that were three times as long as broad,’ together
with divers other sorts which it would take all too long
to specify. In the evening of the same day, I discovered
little paws on the foresaid oval animalcules,’ which were
many in number, in proportion to the animalcule; and
also a much bigger animalcule* of the same figure, that
was likewise furnished with little legs. And at this point,
I stopped my observations upon this water.

6th Observation anent Rain-water.

On the 17th ditto, it rained very hard in the forenoon,
and I collected water, as before related, in a new Delft
porcelain dish, which had never been used before; but I
found therein no living creatures, only many earthy
particles, and, among others, bits which I imagined came
from the smoke of coals’; and some very thin threads, at
least ten times thinner than the thread of a silk-worm.
They seemed to be made up of globules; and when they
lay rather thick one upon another, they had a green
colour.

The 26th ditto, having been eight days out of town
on holiday, and my closet having stood tight shut up;
being come home, and observing the water afresh, I
discovered divers animalcules, which were very small.°

* Unidentifiable, as no further details are given. Possibly Bodo
caudatus.

” 2? Cyclidium. The “paws” were obviously cilia.
* A ciliate; but not determinable, as this is all that is ever said about it.

* June, 1676.
° wande rook van smits coolen MS. “from the smoak of Smiths-coals”
Phil. Trans. “ Smits coolen”’? means ordinary (or stone) coal, as dis-

tinguished from “ howts coolen’’, or charcoal. The “globules” present in
smoke are described by L. elsewhere.

° Unidentifiable. It is not clear from his words whether L. here refers
to the ‘‘ very small animalcules’”’ (Monas?) previously mentioned or not.

128 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS ”’

Thereupon I put my observations upon rain-water on one
side for the time being.

[ Observations on River-water. |

This town of Delft is very well off for water, and in
summer we get fresh water into the town with all the
floods seaward from the river Maas; wherefore the water
within the town is very good, and river fish are caught
every day by children with fishing-rods in the water-
ways inside the town. This water being divers times
examined by me, I discovered in it some exceeding small
animalcules (so small, indeed, that I could scarce discern
their figure) of sundry sorts and colours, and therewithal
some that were much bigger; though were I to specify
the motion and the make of every one of ’em, ’twould
take all too long a-writing. But all these animalcules are
very scanty in this water, compared with those that I saw
in the rain-water; for if I discovered 25 animalcules in
one drop of it, that was quite a lot.’

[Observations on Well-water.]

I have in my yard,’ standing in the open air, a well,
which is about 15-foot deep before you come to the
water. It standeth at the south, but so encompassed
with high walls, that even when the sun is in the sign of
Cancer, the coping of the well is not shone upon. This
water cometh out of the ground, which is well-sand, with
such force, that whenever I have tried to empty the well
there was always about a foot of water still leftin. On
a summer’s day this water is so cold that ’tis not feasible
to keep your hand in it for long. Having no thought
that there would be living creatures in it (for ’tis very

1 No identification of these “animalcules”’ can be attempted, though
they must have been protozoa or bacteria. As some of them were coloured,
it may be inferred that they included Phytoflagellates.

> op mijn plaets MS. “In the open Court of my house’? Oldenburg
dans ma cour Huygens.

PLATE

XX

I

THE SHORE AT SCHEVENINGEN
as it appeared in Leeuwenhoek’s time.

National Gallery

facing p. 129

by Jacob van Ruisdael (1628 ?- 1682).

ing

t

-pain

il

After the o

LETTER 18. RIVER,- WELL,- SEA-WATER 129

palatable and clear), I examined it in September of last
year, and discovered therein a great number of very
small animalcules, which were very clear, and a bit bigger
than the very smallest animalcules that I’ve ever seen.
And I imagine (having aforetime weighed a grain of
water), that there were commonly more than 500 living
creatures in one grain of this water. ‘These animalcules
were very sedate, moving without any jerks.”

In the winter’ I perceived no little animals, nor did I
see any of them this year before the month of July, and
then not in such great plenty; but in the month of
August, their number was much increased.

[ Observations on Sea-water.|

The 27th of July, 1676, I betook myself to the seaside,
hard by the village of Schevelinge.* Finding myself upon
the shore (the wind coming off the sea, with very warm
sunshine), and observing the sea-water as well as I could,
I discovered in it divers living animalcules. I gave to a
certain person, who went into the sea to bathe himself, a

—_—_—__

‘G.e., anno 1675.

* dese diertgens waren seer sedig, sonder eenige horten in haer beweginge
MS. - + + Were very quiet and without motion” Phil. Trans.—
Oldenburg’s translation is clearly wrong, and entirely changes the meaning
of this passage. The organisms were probably very small flagellates
(? Cercomonas sp.): and I imagine that L. is here contrasting their even
(creeping) movements with the jumping motions of the Cyclidiwm which he
had previously seen in rain-water.—According to Sewel (1708), hort means
“a Hunch, push, jog, tug”: and to do a thing “ met horten en stooten”’
signifies to do it “ by fits and starts”, as we now say.

* Presumably 1675-1676.

* Now called Scheveningen—the well-known sea-side resort near The
Hague: but the name is so spelled by L. here and elsewhere (cf. Send-brief
XLII, 10 Sept. 1717), as it is in some old Dutch maps which I have
examined. Pepys, in his Diary, also calls the place ‘ ‘ Scheveling, ” while
Temple (1693), our Ambassador to Holland in 1668, writes ‘Skeveling ”’ ;
and Professor Beijerinck informs me further that the spelling © Schevelingen ”’
was sometimes used formerly. The appearance of the ‘‘ Shore at Schevelinge ”’
in L.’s day is shown in the well-known picture by Jacob van Ruisdael (1628-
1682) in the National Gallery (No. 1390). See Plate XXI.

9

130 LEEUWENHOEK AND HIS “LITTLE ANIMALS’”’

new glass phial (which I had bought on purpose) and
besought him that, when he was in the sea, he would
rinse it out twice or thrice and then fill it up with water.
This having been carried out according to my orders, I
tied the phial up tight with a clean bit of bladder: and
on reaching home and examining the water, I perceived
therein a little animal’ that was blackish, having a shape
as if twere made of two globules. This little animal had
a peculiar motion, after the manner of a very little flea,
when seen, by the naked eye, jumping on a white paper ;
yet ’twas only displaced, at every jump, within the com-
pass of a coarse sand-grain, or thereabouts. It might
right well be called a water-flea; but ’twas not so big,
by a long way, as the eye of that little animal which
Swammerdam calls the Water-flea.”

I did also discover animalcules which were clear, of the
same bigness as that first mentioned; but they had an
oval figure, and their motion was snake-wise.

Furthermore, I perceived yet a third sort, which were
very slow in their motion. Their body was mouse-colour ;
and they were also a bit on the oval side,’ save that a
sharp little point stuck out (sting-fashion) * in front of the
head, and another at the hind end. This sort was a bit
bigger.

And there was besides a fourth sort, rather longer than
an oval. Yet all these animalcules were few in number,
so that in a drop of water I could make out but 3 or 4,
nay, sometimes but one.

* Iam unable even to hazard a guess at the identity of this organism ;
but, judging from its estimated size, it may well have been a protozoon.

> i.e., Daphnia. Cf. p. 118, note 1.

° mede hellende na de ovale kant MS. “clear towards the oval-point ”’
Phil. Trans.—an evident mistranslation. LL. means that their shape tended
to be oval—not that they were clear at one end. I translate his colloquial
old Dutch into its equivalent in modern conversational English.

* angels gewijs MS. “‘angle-wise” Phil. Trans. Angel means a sting
(e.g., that of a bee), not an angle (=hoek). lL. was probably thinking of the
mouth-parts of a mosquito—which he also called (as the man-in-the-street
still does) its “‘sting”’. ;

ce

LETTER 18. SEA- AND PEPPER-WATER 131

The 31st ditto, having examined this water every day
since the 27th, and perceived no little animals in it;
upon this date I did now see a good hundred of ’em where
at first I had seen but one: but they were now of another
figure, and not only smaller, but also very clear. They
were like an oblong oval, only with this difference, that
they tapered somewhat more sharply to a point at what
I imagined to be the head end. And although these were
at least a thousand times smaller than a very small sand-
grain, I saw, notwithstanding, that whenever they lay
high and dry out of the water they burst asunder, and
flowed apart or scattered into three or four very small
globules and some watery matter, without my being able
to discern any other parts.’ (In the above, I took the
water out of the phial from the surface: and at this time,
too, I was no longer able to see the animalcules of the
sort first spoken of.)

The 2nd of August I could discern nought but an
abundance of the foresaid animalcules.

The 4th ditto, saw ’em as heretofore, without any
difference.

The 6th of August, looking again, perceived nowhere
near as many little animals.

The 8th ditto, I again discovered a very few of the

. foresaid animalcules; and I now saw a few so exceeding
small that, even through my microscope, they well-nigh
escaped the sight. And here I stopped my observations.”

[Observations on Pepper-water. Ist Observation. |

Having made sundry efforts, from time to time, to
discover, if ‘twere possible, the cause of the hotness or
power whereby pepper affects the tongue (more especially
because we find that even though pepper hath lain a

’ This observation indicates that the organisms were protozoa.

* Beyond the obvious fact that they were probably protozoa and bacteria,
I cannot offer any guess at the identity of the various organisms which L.
saw in sea-water.

132 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

whole year in vinegar, it yet retaineth its pungency); I
did now’ place anew about 3 ounce of whole pepper in
water,’ and set it in my closet, with no other design than
to soften the pepper, that I could the better study it.
This pepper having lain about three weeks in the water,
and on two several occasions snow-water having been
added thereto, because the water had evaporated away ;
by chance observing this water on the 24th April, 1676,
I saw therein, with great wonder, incredibly many very
little animalcules, of divers sorts; and among others,
some that were 3 or 4 times as long as broad, though
their whole thickness was not, in my judgement, much
thicker than one of the hairs wherewith the body of a
louse is beset.2 These creatures were provided with
exceeding short thin legs in front of the head (although
I can make out no head, I call this the head for the
reason that it always went in front during motion).
This supposed head looked as if ’twas cut off aslant, in
such fashion as if a line were drawn athwart through
two parallel lines, so as to make two angles, the one of
110 degrees, the other of 70 degrees. Close against the
hinder end of the body lay a bright pellet, and behind
this I judged the hindmost part of all was slightly cleft.
These animalcules are very odd in their motions, oft-times
tumbling all around sideways; and when I let the water
run off them, they turned themselves as round as a top,
and at the beginning of this motion changed their body
into an oval, and then, when the round motion ceased,
back again into their former length.’

cis Bi ate Fie i 5

! The exact date is not recorded ; but it will be seen from the next sentence
that the pepper was laid in water during the first few days of April, 1676.

® Unfortunately L. omits to state what kind of water he used. Had he
done so, it would have afforded some help in attempting to determine the
organisms which he found in it later.

* About 3. See p. 337 infra.

‘From the foregoing description I think it highly probable that the
animal observed was Bodo caudatus (Duj.) Stein,—one of the commonest
protozoa found in organic infusions. The description, as far as it goes, fits
this animal almost exactly.

LETTER 18. PEPPER-WATER 133

The second sort of animalcules consisted of a perfect
oval." They had no less nimble a motion than the
animalcules first described, but they were in much
greater numbers. And there was also a third sort, which
exceeded both the former sorts in number. These were
little animals with tails, like those that I’ve said were in
rain-water.”

The fourth sort of little animals,’ which drifted among
the three sorts aforesaid, were incredibly small; nay,
so small, in my sight, that I judged that even if 100 of
these very wee animals lay stretched out one against
another, they could not reach to the length of a grain of
coarse sand*; and if this be true, then ten hundred
thousand of these living creatures could scarce equal the
bulk of a coarse sand-grain.

I discovered yet a fifth sort,’ which had about the
thickness of the last-said animalcules, but which were
near twice as long.

2nd Observation [on Pepper-water].

The 26th of April,° I took 23 ounces of snow-water
(which was a good three years old, and which had stood
throughout either in my cellar or in my closet in a glass
bottle, well stoppered), wherein I was able to discover no
living creatures. Having poured this same water into a
porcelain tea-cup, with half an ounce of whole pepper, I
set it likewise in my closet. J examined this water every
day until May the 3rd, but could discover therein no
living creatures; and by now the water was so far
evaporated away and absorbed by the pepper, that some

* Perhaps a Cyclidiwm—equally common in infusions of all sorts.
* Vorticella sp. Cf. p. 118 supra.
* Evidently bacteria.

*T.’s “coarse sand-grain’’=approximately 355 inch in diameter. Cf.
p. 334 enfra.

> Probably bacilli. /
* i.e., anno 1676. le
(.

134 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”

of the pepper-corns began to lie dry. And this water was
now so thick with particles, that you might almost
imagine you were looking at the spawn of very wee fish,
what time the fish discharges its roe, when the roe-corns
are very soft, and as ’twere hang together. Thereupon
I added snow-water to the pepper once more, until the
pepper-corns lay under about half an inch.

The 4th and 5th of May, examined it again, but
perceived no living creatures.

The 6th ditto, I discovered very many exceeding small
animalcules.' Their body seemed, to my eye, twice as
long as broad. Their motion was very slow, and oft-times
roundabout.

The 7th ditto, I saw the last-mentioned animalcules
in still greater numbers.

On the 10th ditto, I added more snow-water to the
pepper, because the water was again so diminished that
the pepper-corns began to lie dry.

The 13th and 14th ditto, the animalcules as before.

The 18th of May, the water was again so dried away,
that I added snow-water to it once more.

The 23rd of May, I discovered, besides the foresaid
animalcules, living creatures that were perfectly oval, like
plovers’ eggs.” I fancied that the head was placed at the
pointed end, which at times was stuck out a bit more.
Their body within was furnished with some 10, 12, or 14
globules, which lay separated from one another. When
I put these animalcules on a dry place, they then changed

" Probably bacilli.

® de Kievits eijeren gelijk MS. “like Cuckow-eggs”’ Phil. Trans. Kievit
means the Peewit or Lapwing (Vanellus cristatus), not the Cuckoo (Cuculus
canorus). The eggs of the former are, of course, those which are known
commercially as “ Plovers’ eggs”. The distinction is not without import-
ance here, as the “ Plover’s egg” is conspicuously pointed—that of the
Cuckoo being much more rounded.—The organism was probably Colpidium
or an allied ciliate. L.’s remarks a little later support the view that he was
observing the “small variety’ of C. colpoda—a very common inhabitant of
such infusions.

LETTER 18. PEPPER-WATER 135

their body into a perfect round, and thereupon oft-times
burst asunder; and the globules, together with some
watery humour, flowed out on all sides, without my being
able to discern any other remains. These globules, which,
in the bursting asunder, flowed apart from one another,
were of about the bigness of the first-mentioned very
little animalcules. And albeit I could as yet distinguish
no feet on the said animalcules, none the less I imagined
that they must be furnished with many very little ones ;
for the very smallest animalcules (whereof I have already
said there were a great many in this water, and of which
more than 100 sometimes lay around one of the little oval
creatures) were driven away from the bigger ones by the
motion which these made in the water (even when the
big animalcules themselves seemed to me simply to lie
still, without stirring at all), just as if you were to blow a
feather from your mouth.’ Of these oval animalcules I
could never discover any very little kind,’ how diligently
soever I sought them.

The 24th ditto, examining this water again, I found the
oval animalcules in a much greater number. Dvtto, in
the evening, looking again, I perceived so great a plenty
of the oval animalcules, that ‘twas not a mere thousand
that I saw in one drop; while there were several thousands
of the very small animalcules in the same drop.

The 25th ditto, I saw still more of the oval animalcules,
and some most exceeding thin little tubes,’ which I had
also seen many a time before this.

The 26th ditto, I saw such a great many of the oval
creatures, that I believe there were more than 6 or 8
thousand in one drop, not counting the multitude of very
little animalcules, whereof the number was far greater.

SS, - aE

1 This is obviously a description of a ciliate (e.g. Colpidium), with actively
vibrating cilia, lying among bacteria.

® f.e., any young ones.

* pijgpjes MS. Probably thread-bacteria.

136 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

But I took this water from the surface, and in the water
that I took from underneath there were nowhere near as
many. Seeing these little animals increase to so vast a
number, but therewithal not being able to detect that
they did wax in bigness, nor yet to espy any like creatures
drifting in the water, I bethought me whether these
animalcules might not well be put together in an instant
(so to speak) *: but this speculation I leave to others.”

The 26th dztto, in the evening, I perceived almost none
of the little animalcules; but I now saw divers creatures
with tails (whereof I have said heretofore that I saw ’em
in rain-water).” And furthermore I saw one animalcule
that was three times as long as broad. Through all the
water floated numberless particles, like thin little hairs
off men who haven’t been shaved for a fortnight*; but
with this difference, that many had a kink in them.

The 27th ditto, I perceived none at all of the very little
animalcules, but the large creatures in greater number.

The 28th ditto, almost all the animalcules in the pepper-
water were become somewhat scantier.’

The 80th dztto, I discovered very few animalcules in
the water, and I saw there now but one where some days
before I had seen a good hundred. And as the water was

' of deselvige niet wel in een moment des tijts (om soo te spreeken) en

waren te samen gestelt MS. He means that it crossed his mind that these
animals might possibly come into existence, on a sudden, by a fortuitous
concourse of inanimate particles in the water. As a rule, of course, L.
strongly opposed the doctrine of spontaneous generation.

* dog ik geef dit aen anderen over MS.
* i.e., Vorticella sp.

* By this quaint simile L. means to convey the idea that the particles, if
magnified in diameter to the size of human hairs, would be about as long,
in proportion, as those forming the beard of a normally clean-shaven man
who had not shaved himself for about a fortnight.

> wat dunder MS., lit. = somewhat thinner. I take L. to mean that the
water itself was now not so full of animalcules—not that the animalcules
had themselves grown thinner. But Oldenburg seems to have taken the
latter view, for he translates (Phil. Trans.) ‘all sorts of those living creatures
in this peppery water were grown thinner.” The ensuing paragraph supports
the above reading.

LETTER 18. PEPPER-WATER 137

now so dried away, that the pepper began again to he
above the surface, I filled up the tea-cup with snow-water
once more.

On June the Ist, the animalcules were again in as
great numbers as I had ever before seen, though I can’t
say that I saw any of the very little ones. But now I
could see very plain that the animalcules were furnished
with very thin little legs,* which was a very pretty sight
to see.

The same day, I discovered some few very little round
animalcules,’ that were about 8 times as big as the
smallest animalcules of all. These had so swift a
motion before the eye, as they darted among the others,
that ’tis not to be believed. The big creatures, which
were about 8 times smaller than the eye of a louse,’ were
in no less number.

My further observations on this water I have made no
note of.

8rd Observation [on Pepper-water].

On May the 26th, I took about $ of an ounce of whole
pepper, and pounded it small, and then put it in a
tea-cup in which there was about 22 ounces of rain-water,
stirring this water about in order that the pepper might
mix itself with the water and then sink to the bottom.
And after letting it stand thus an hour or two, I took
some of the forementioned water in which the whole
pepper lay, and which contained a multiplicity of little
animals, and mixed it with this water wherein the
pounded pepper had now lain for one or two hours: and

_

i.e., the cilia on the ciliates (? Colpidiwm).
* Probably larger bacteria.

* This is the first indication which L. gives of the size of his ciliates.
‘About 8 times smaller’? means “having a diameter of about a half”:
and this therefore agrees with the supposition that the “ oval animalcule”’
was the small species (or variety) of Colpidiwm so commonly found in
such infusions.

138 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

I observed that when I added rather much of the water
containing the pounded pepper, it came to pass that the
foresaid animalcules died forthwith; but when I added
somewhat less of the same water, then the little creatures
remained alive.

On June 2nd, in the forenoon, after I had made divers
observations since the 26th ultimo, but without being
able to discover any living creatures, I now saw a few
particles which had, indeed, the figure of some of the
little animals, although I could distinguish no life in
them, how attentively soever I looked. On the 2nd
again, at night, about 11 o’clock, I discovered a few very
little living animalcules.

The 3rd ditto, I discovered therein many more
animalcules, which were all very small, and about 2 or 8
times as long as broad.’ All through this water little
bubbles kept rising, as if ’twere fresh beer that stood
fermenting.

The 4th ditto, in the morning, I found therein a great
many animalcules. The same day, in the afternoon,
examining the water again, I saw such a great many
living creatures in one drop of it, that they amounted
to at least 8 or 10 thousand; and to my eye they were,
when viewed through my microscope, like ordinary
sand-grains to the naked eye.

On the 5th ditto, I discovered, besides the multifarious
very little animalcules aforesaid, some few (but not above
8 or 10 in one drop of water) little oval animals,” whereof
some exceeded the others quite 8 times in bigness,’ whilst
the biggest of them were in shape like the oval
animalcules that I have made mention of before (those
that were in the water wherein the whole pepper lay).*

* s00 lang als breet MS. “as broad as long” Phil. Trans.—an obvious
mistake.—The organisms were evidently bacilli.

* Probably Colpidium again.

* 1.e., were twice as long.

* i.e., they resembled the organisms previously identified as Colpidiwm.

LETTER 18. PEPPER-WATER 139

On the 6th ditto, the animalcules were as before.

On the 8th ditto, the little oval animals* were
multiplied, swimming among the foresaid very numerous
little animalcules*; and now they’ were very nearly all
of one and the same bigness.

The 9th of June, the oval animalcules were in yet
ereater number, but the very little animalcules were now
less. And now, using again a particular method in
observing, I saw the little feet or legs* (wherewith the
animalcules were provided underneath their body, which
was flat) moving very plainly ; and with such a swiftness,
that ’tis incredible. And methinks that ever and anon I
could make out that each of the globules, whereof, as I
have said, their body was for the most part composed,
was not perfectly round, but every one of them stuck out
in a point, in the same fashion as the shields or plates
on the sturgeon or thornback do.’ The said animalcules
were, to my eye, 8 times smaller than the eye of a louse.”

On the 10th ditto I took a little of the last-mentioned
water, and mixed it with a little water wherein 36 cloves
had now lain for about 3 weeks; and I perceived that,
no sooner did the multifarious little animals aforesaid
come into this mixed water, than they were dead.

On the 12th ditto, the said animalcules seen in no less
number; and as the water was now so evaporated away
and sucked up by the pepper, that the pepper itself began

* Colpidium.
* Bacteria.

*¢.e., the colpidia. L. cannot have meant that the ciliates and bacteria
were now equal in size.

‘ i.e., the cilia (on the Colpidium).
° ie., like the “ placoid scales ” of some Ganoid and Elasmobranch fishes,
such as the sturgeon (Acipenser) and the thornback (Raja clavata).

® This estimate accords with that given for the “ oval animalcules ’’ under
date June 1 (2nd observation).—Oldenburg’s translation in the Phil. Trans.
terminates at this point. All that follows has never previously appeared in
print.

140

1

2

8

LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

to lie dry, I threw the latter away, after first of all tasting
it on my tongue, and finding it as strong as if it had just
been pounded.

4th Observation {on Pepper-water |.

The 14th of June, a certain quantity of whole pepper
put in well-water.

The 16th dzttv, in the morning, on examining the same,
I discovered, in a tiny drop of water, incredibly many
very little animalcules, and these of divers sorts and sizes.’
My further observations I have not made note of, save
that on the 17th of July still more animalcules were seen,
and among them many of the little oval creatures” many
times mentioned already.

Examining the water again on July 20th, I now saw,
with very great wonder, that some very long and very
thin particles (which I imagine had come to my notice
in various waters before) were alive. These most
wonderful living creatures seemed, when viewed through
my microscope, thinner than a very fine hair of one’s
head, and about as long as the back of a bread-knife,°
others quite twice as long. Their whole body appeared
of one and the same thickness throughout, without my
being able to make out a head or any bodily parts; and
therewithal their body was very clear, and ’twas thus
very troublesome to succeed in seeing ’em alive in the
water. They moved with bendings, as an eel swims in
the water; only with this difference, that whereas an eel
always swims with its head in front, and never tail first,

Bacteria—various sorts.
Colpidiwm.
Another of L.’s homely similes. He means that the “animalcules”

were very long, and uniformly thin—their proportions being similar to those
of the blunt edge, or back, of a large knife such as is used for cutting bread ;
though their thickness actually appeared not so great, but even less than
that of a human hair as seen by the naked eye. Itis a peculiar comparison,
but on the whole conveys a tolerably accurate notion of the appearance of
the long thread-bacteria which he was evidently observing.

LETTER 18. PEPPER-WATER 141

yet these animalcules swam as well backwards as forwards,
though their motion was very slow. And were I to
contrast these creatures with the eels or worms which are
in vinegar,’ I imagine the proportions would be thus :

As a worm of the bigness of a big pin, is to an eel of
the thickness of one’s wrist : So are these very little living
creatures or eels in the pepper-water, to the size of the
eels in vinegar.

5th Observation [on Pepper-water].

On August the 2nd, in the evening about 7 o’clock, I
again examined my well-water, which was very clear
(especially when it stood in a kettle or pot; but standing
in a clean glass, alongside of clean rain-water, the rain-
water outdid the well-water in clearness). In this well-
water I saw living a great many of the oft-mentioned
very little animalcules*; some thousands, indeed, in one
drop of water. I then poured some of this water into a
porcelain tea-cup, adding thereto a quantity of coarsely
pounded pepper; and [I stirred round the pepper in the
water, deliberating whether the said animalcules would
remain alive in the peppery water, or whether they would
die. This water and pepper having been stirred up, I
examined it, and saw the animalcules living: after the
lapse of half an hour I examined it again, and saw the
animalcules still alive, but their motion was not so quick
as when they were in plain well-water. After the lapse
of two hours more, examining the water again, I saw the

ee ee

1 A yemarkably shrewd observation, which proves conclusively that L.
was here dealing with bacteria. The organisms were evidently the long
flexible thread-bacteria (Pseudospira C.D.) so common in infusions.

2 Of these more anon. The “vinegar-eel” (Anguzllula acett) was
described by L. in an earlier letter, dated 21 April 1676. See Phil. Trans.,
Vol. 0%, p: 6093 (1676). Power, Kircher, Borel, and others had, however,
discovered this organism at a still earlier date, though L. was apparently
unaware of their observations. IL. gives figures of the eel in a later letter
(No. 43, 5 Jan. 1685).

® fe., bacteria, in all probability.

142 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

animalcules even yet alive, though in much less number
than heretofore.

On the 3rd of August, about 7 o’clock in the morning, I
saw some few animalcules still alive; while the water was
fermenting, as if it had been beer that stood and worked.
In the afternoon, about 4 o’clock, examining it again, I
still saw a few animalcules alive. In the evening, at
about 9 o’clock, however, I saw very few animalcules
living.

On the 4th ditto, about 6 o’clock in the morning, I
could discover no living animalcules, how attentively
soever I looked; but I thought I saw some floating dead.
The evening of the same day, about 9 o’clock, I discovered
4 or 5 very little animalcules, and among them one some-
what bigger, and very round. Such an animalcule I have
never seen in well-water.

The 5th ditto, in the morning, I saw again 4 or 5 very
little animalcules, among them one that exceeded the
others a bit in length: and amidst the very many par-
ticles, I judged that I could distinguish little forms which
agreed in their shape with the foresaid living animalcules,
but I could discern no life in them. On the afternoon of
the same day, about 3 o’clock, I saw several most extra-
ordinarily small animalcules (nay, even smaller than
those in the well-water), together with many animalcules
that were somewhat bigger. These last * were well-nigh
round, and their motion was mostly all a-rolling, where-
withal they didn’t much hurry themselves. ‘Together
with these was a sort” that were of the same size, but
they were somewhat elliptical. And lastly, I also saw
some® (though very few) which were a good 20 times
bigger than the biggest sort spoken of above. These were

1 Probably small flagellates (? Monas sp.).
? Unidentifiable. Perhaps more elongated specimens of the same Monas.

* Perhaps Euplotes or an allied hypotrichous ciliate. (The movements
described indicate that it cannot have been a Cyclidiwm.) “ A good 20 times
bigger’? means “ having about thrice the diameter” of the former sort.

LETTER 18. PEPPER-WATER 1438

long, and bent crooked, the upper part of the body round,
but flat beneath, looking much after the fashion of an
s part of the peel of a large citron. Their motion was all
a-wallowing, on their back as well as on their belly. I
could discern no little feet or legs on them; and after this
time, moreover, I never saw them any more. In the
evening, about 10 o’clock, I saw the very little animal-
cules, and the round ones,” in much greater numbers;
together with a little animal that was 3 or 4 times as
long as broad *; and besides these, many little worms, or
little eels *, which were even smaller than the very tiny
eels spoken of before.

On the 6th ditto, about 6 o’clock in the morning, [
discovered a very great many (indeed, incredibly many)
exceeding little animalcules, to which, because of their
littleness, no shape can be given’; and with these a very
great number of round animalcules,’ which to my eye
seemed quite eight times as big as the first animalcules (in
which I have just said I could make out no shape). These
round animalcules I imagine to be more than 50 times
smaller than the eye of a louse. And besides these there
was a third sort,’ that were twice as long as broad, and
which had about the length of the round animalcules.
The fourth sort * was the very tiny eels; but now I could
not see their bending, when they moved, so very plainly
as I had seen it before: and at this time too I saw some
(though very few) animalcules, which had very nearly the
length of the eye of a louse, and which were in shape very

" Bacteria.
° 9? Monas sp.

* Unidentifiable; ? a small flagellate. (Had it been large, L. would
doubtless have supplied some further details.)

* Bacteria, probably Spzrzllwm sp.

> Bacteria.

° Larger bacteria ? (“8 times as big” = of twice the diameter.)
* Unidentifiable.

* Spirilla.

144

LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

much like (only much smaller) that animalcule which I
have previously likened to a piece of citron-peel. More-
over, I could not convince myself that I now saw, among
the sorts of animalcules described, those creatures which I
have said I saw in the well-water, although I examined the
well-water also.

The same day, about 3 o’clock in the afternoon, I saw
still more animalcules, both the round ones and those that
were twice as long as broad; and besides these, a sort
which were still smaller ; and also incredibly many of the
very little animalcules whose shape, this morning, I could
not make out. J now saw very plainly that these were
little eels,, or worms, lying all huddled up together and
wriggling; just as if you saw, with the naked eye, a
whole tubful of very little eels and water, with the
eels a-squirming among one another: and the whole
water seemed to be alive with these multifarious animal-
cules. This was for me, among all the marvels that I
have discovered in nature, the most marvellous of all; and
I must say, for my part, that no more pleasant sight has
ever yet come before my eye than these many thousands
of living creatures, seen all alive in a little drop of water,
moving among one another, each several creature having
its own proper motion: and even if I said that there were
a hundred thousand animalcules in one small drop of
water which I took from the surface, I should not err,
Others, seeing this, would reckon the number at quite
ten times as many, whereof I have instances; but I say
the least. My method for seeing the very smallest
animalcules, and the little eels, I do not impart to others ;
nor yet that for seeing very many animalcules all at once ;
but I keep that for myself alone.

The same day, about 11 at night, the animalcules were
as before. The sort in which I could hitherto discern no
shape, I now fancied to be round, rather than long.

* Spirilla.

LETTER 18. PEPPER-WATER 145

On the 7th ditto, about 8 o’clock in the morning, the
animalcules were as heretofore. The little eels or worms
were a bit bigger, but the very smallest animalcules I
could not now make out. Ditto, in the evening about
8 o’clock, I now saw again the smallest animalcules of
all, but few in number. The round animalcules very
plentiful; and the animalcules which were twice as
long as broad, together with the little eels, I saw in
numbers unspeakably vast, for the amount of water.

The 8th ditto, about 8 in the morning, the animalcules
as before. The same day, afternoon and evening, the
animalcules seen in no less number.

The 9th ditto, in the morning, the animalcules as
before. Ditto, in the afternoon, the animalcules in no
less number, excepting that the round animalcules
now seemed fewer to my eye.

Having been, from the 10th to the 17th of this month,
in Brabant and elsewhere for a holiday, I now observed
that the water was very small in amount, and thick
with all manner of very small particles; and I saw that
the animalcules lay alongside one another in great plenty,
without any motion, save 2 or 3 animalcules which I saw
moving feebly. Thereupon I again added a little well-
water to the pepper and the water that remained over:
and I then viewed the water, but notwithstanding could
perceive no further movement in it, after several
observations.

The 18th ditto, in the morning, examining this water
again, I saw the animalcules alive and moving in as
great numbers as ever heretofore, though their motion
was not so quick; excepting only the little eels, none of
which I could discern. Ditto, in the evening, the motion
in the animalcules was as quick as ever before.

The 19th ditto, the animalcules as before.

The 20th ditto, the animalcules as before.

The 21st ditto, the animalcules aforesaid, that were
almost round, were in incredibly great plenty, and more

10

146

LEEUWENHOEK AND HIS ‘“ LITTLE ANIMALS ’”’

than ever before; the animalcules that were twice as long
as broad were fewer in number than hitherto, and now I
could discern that before and behind they ran somewhat
to a point; and ’twas pretty to behold the motion, all
a-quivering and a-shivering, that such very little creatures
made in going forward. No others than these two sorts
could I discover. Among other particles, there drifted
through the liquid a multitude of short straight little
tubes, several times (yea, 3 or 4 times) shorter than
the foresaid very thin little eels or worms, so that they
were only to be made out by very curious inspection.

The 21st ditto, in the afternoon, the animalcules in
abundance, as before. The long animalcules are clear;
the rounded ones appear encircled with a dark streak, and
having at the hindmost part of their body a little dark
spot or point.

The 22nd ditto, the animalcules as before. The short
and very smali tubules were in greater numbers.

The 3rd of September, the animalcules being as before,
without my being able to espy any notable change in
them, I again poured well-water (in which there were
many living animalcules) upon the pepper, and at the
same time put also two eggspoonfuls of coarsely pounded
pepper into the water; considering whether the animal-
cules might not then die.

* (L have, moreover, well-water containing whole pepper
still standing in my closet; but I have sent no notes of
the observations made thereon. I have seen in it, besides
divers animalcules, a great many little eels or little
worms, together with a sort of little animals that were a
bit smaller than the oval creatures already oft-times
referred to. These were rounded like an oval at the hind
end of the body, but their foremost part had, at its end,
a crooked bend, like a parrot’s beak.”

*The whole of this passage is thus put in parenthesis in the MS., and
was perhaps meant for a footnote.

* Probably Chilodon.

LETTER 18. PEPPER-WATER 147

The animalcules which I have throughout called “ oval
animalcules”’, are not really oval, unless you look upon
them on the back or upper part of their body; and as the
making of observations is well-nigh a study in itself, I
have only just now exhibited them to myself very prettily
in side-view, and have demonstrated not only their little
feet, but also their head, and their very short and pointed
little tail. At such perfection in this tiny creature I did
creatly marvel’: and were it not that the multiplicity
of solid particles (which are present in plain water)
hindered me, I could describe the little animals even more
distinctly.)

The 4th of September, the animalcules were seen in
such great abundance as never before; but whether the
animalcules which were at first present in the well-water
were yet alive, I still can’t say for certain.

The 5th ditto, the animalcules in an incredible number,
much greater than hitherto; but they consisted of only
two sorts, to wit: the roundish animalcules, and the
animalcules that were twice as long as broad, albeit some
few somewhat exceeded the others in length. The long
animalcules were a bit thicker than the hair of a louse,
and the round ones about twice as thick.

The 6th ditto, the animalcules in as great abundance
as heretofore. I now imagined that the long animalcules
consisted of two sorts: and I imagined, furthermore, that
I saw animalcules of such extreme littleness as I had
never up to this date seen in pepper-water.

The 7th ditto, the animalcules in even greater number
than before this date.

The 8th of September, besides the foresaid long animal-

1T, was always carried away with delight at beholding the “ perfections ”’
of ‘little animals’’. So also, it appears, was his draughtsman: for L. tells
us elsewhere that in making drawings of a flea he was repeatedly provoked
to exclaim (his words being given by L. in large capitals) “‘ Lieve God wat
sijnder al wonderen in soo een kleyn schepsel!” (Letter 76, 15 Oct. 1693.)
Cf. also p. 279 znfra.

148

LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS ”’

cules and roundish animalcules, I discovered three which
had the figure of a pear, only with this difference, that on
the underside of their body they were flat.’ Such a sort I
had not seen till now in any water. And I had such a
hunt for these creatures, because they were so few, that I
gave no heed to the very smallest ones.

The 9th ditto, I perceived but one of the animalcules
that had the figure of a pear, in four several observations.
And though there was still quite a lot of water with the
pepper, yet I added more well-water to it, because the
pepper-water was become rather thick. Ditto, in the
afternoon, about 4 o’clock, I could see none at all of
the animalcules that had been in great plenty in the
well-water ere I poured it on the pepper; neither could
I discover any of the animalcules that had the figure
of a pear.

The 10th ditto, in the morning, the roundish and the
long animalcules were now in such inexpressibly great
crowds, that they far exceeded in number all the animal-
cules that I had ever seen up to this date in any waters.
Moreover, I could discern no other sort.

On the 14th ditto, I could remark no change since the
10th, save only that 1 now saw again animalcules which
had the figure of a pear; and I saw there besides an
animalcule with a tail.’

The 15th ditto, | saw more animalcules that had the
figure of a pear, and two or three animalcules with tails.
And I perceived at this time that the pear-shaped
animalcules kept not against the surface of the water,
like the other creatures, but that they swam a bit deeper
under water. Their thickness was about that of a single
small thread of a silk-worm,’ and they were about 13 times

’ Evidently a hypotrichous ciliate.

? t.e., Vorticella.

° Cf. Letter 146. 20 April 1702. To the Landgrave of Hesse. Printed
fully in Dutch and Latin collective editions.

LETTER 18. PEPPER-WATER 149

as long as broad. The smaller nearly round animalcules,
and the long ones, were present in no less number.

The 16th ditto, the animalcules that had the figure of
a pear, as before: the animalcules with tails were
increased to a greater number: the small round animal-
cules, and the animalcules that were twice as long as
broad, were now diminished in number.

* [The 16th ditto, the animalcules that had the figure
of a pear, as before: the animalcules with tails were even
more numerous than formerly: the long and the round
small animalcules were even more reduced in number. |
On this occasion I discovered three animalcules’ that
were equally thick throughout, but which tapered to
rounded ends before and behind, very like the fruit that
we call dates.* The thickness of them was about that of
a very fine sheep’s hair. Their motion was very curious,
with a rolling about and a tumbling and a drawing of
themselves together into a round.

The 17th ditto, the animalcules that had a figure like a
pear, as before: the animalcules with tails in greater
number: the long and the round animalcules were de-
creased still further, and therewithal very slow a-moving.
The animalcules that were equally thick throughout were
somewhat more plentiful; and now I could make out

"The passage here placed in square brackets is in the MS., but it is
obviously a repetition—with slight differences in wording—of the preceding
paragraph. lL. seems to have paraphrased the same entry in his notebook
(for Sept. 16) twice over, by mistake.

* Evidently a large ciliate—probably Oxytricha.

*dalen MS. I have been unable to find this word in any dictionary—
ancient or modern. Oldenburg (MS. ined.) translated the word thus, and
may have had some authority for so doing. Elsewhere, however, L. speaks
of the date by its usual Dutch name, dadel: cf. Letter 47, 12 Oct. 1685.
The description is consistent with the above rendering: and Dr E. P. Snijders
informs me that candied dates are still sometimes called “ confijte dalen”’,
in popular speech, in Holland.

‘ Blsewhere (Letter 80,2 Mar. 1694) L. shows that sheep’s wool consists
of a number of “ fine hairs” stuck together. By “a fine sheep’s hair’’ he
here means, apparently, one of these component filaments.

150

LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS”

that they were a bit flat in front, furnished with divers
little legs, which during motion stuck out a bit beyond
the body; and at the hind end of the body there was a
round spot, running out headwards in a dark streak,
looking very much like the guts or the blood in the
body of a louse,’ as seen with the naked eye.

The 19th of September, the numerous long and roundish
little animalcules were much slower in their motion, and
amany of them lay without any motion at all. The
animalcules with tails were increased to yet greater
numbers: the animalcules equally thick throughout, and
those that had the figure of a pear, were in number as
before.

My further observations I have not recorded: I can
only say this, that in the course of a day or two the
water again got so thick, that all the animalcules that
were still in it moved themselves very slow; and 2 or
3 days after I had poured in well-water once more, I
perceived the small animalcules in as vast a number as
ever heretofore.

[Observations on Vinegar. ]

For the last 2 or 3 years I have not been able to find
any little worms, or eels, in the vinegar that I keep in
a cask in my cellar, for my household. I now®* drew
off } pint of this vinegar into a glass, and set it in my
closet, covering it over with a paper to keep off the dust :
and after the lapse of 11 days, I did perceive therein
little eels, which multiplied from day to day. I have
divers times put a little vinegar into a little pepper-water,
and have always seen that as soon as the pepper-water

‘4 more particular description of this phenomenon was given by L. in
an earlier letter (7 April 1674) published—in part only—in Phil. Trans.,
Vol. IX, p. 23. The more famous description of the “blood and guts in the
louse” by Swammerdam was not published until long after this date.

* See note 2 on p. 141.

* No date is here recorded.

LETTER 18. VINEGAR Si

was mixed with the vinegar, the animalcules that were in
the pepper-water died instantly; albeit that I was unable
to perceive that the little eels, which were in the vinegar,
suffered any hurt from the pepper-water.

At another time I took some 10 parts of the pepper-
water last spoken of (at the time when the living creatures
were most plentiful in it), and added to it about 7 part 108
vinegar, containing living eels, or little worms. This
vinegar I put in at the bottom, and not on the surface, of
the pepper-water: and I took note that, the moment the
vinegar was added to the pepper-water, the multifarious
very little animalcules that were next the bottom, where
the vinegar was, lay without any motion; and those
animalcules lying further from the bottom became slower
in their motion; and after the lapse of a little while, all
the very little animalcules were dead: yet the motion of
the little eels was no less in this water than when they
were in the vinegar alone. This pepper-water and vinegar,
which together equalled in quantity one big drop of
water, I observed almost from day to day: and after the
lapse of about 2 or 3 weeks, I saw that the little eels in
this mixed water were greatly increased; for where at
first I had seen but 10 eels, I now saw fully 200 of ’em.
And among the rest I saw a great number of very little
eels, near of one and the same bigness as one another,
whose length, to my eye, equalled about 1 or t part of the
biggest eels of all; but notwithstanding the further ob-
servations that I made, I was able to discover no smaller
eels, nor yet any particles that looked like the foresaid
very little animalcules*; but they seemed all gone, without
any remains being left over. Seeing this multitude of
little eels (in the mixture of 10 parts pepper-water and
1 part vinegar), I imagined that surely they were not

Dee ———

1 Ags becomes evident later, L. means that he took 1 part of vinegar
to 10 parts of pepper-water—not, as he apparently says, one-tenth of a
part of the former to 10 parts of the latter.

2 = .
1.e., bacteria.

152 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

generated from any particles which might have been in
the pepper-water, nor yet from such as might have been
in the vinegar, as this, mixed with pepper-water, would
have become unfit for the production of living creatures :
but I felt firmly persuaded that the said little eels had
become thus increased by procreation. I then made use
of certain means, in order to throw more light on these
very little animalcules; and first of all, after I had broken
asunder or pulled apart some of the biggest sort (corre-
sponding to those that I had seen originally in my wine),
I saw that they were provided inside with a long structure,
which had about 4 of the thickness of the eel itself. I
imagined that this was the gut of the little animal. In
some, moreover, I saw still much thinner long structures,
which I imagined might well be small eels: otherwise
the body of this creature was very soft, and streamed
away on all sides in many big globules of various sorts,
and others that were very little (in proportion to the
animalcule). These globules did not consist of watery
matter, but were, in fact, oil: for just as clearly as you
can, by the eye, distinguish oil floating on water, from the
water itself, so clearly could I see the oily particles,
among which were some so small that they well-nigh
escaped the sight. These curiosities of mine I divers
times followed up further; and at last I saw very plainly,
among other things, that from an eel which I had broken
across the middle, there came out four distinct small eels,
each twisted on itself, very nice and pretty, and each
bigger than the one following: and the biggest, which
came out first, lay and lived, and wrenched itself loose,
and remained alive a little while." I have more than
once been able to see a small eel, out of an eel which I

* All these exact observations can be very easily confirmed. The vinegar-
eel is viviparous; and L. was evidently here dealing with large pregnant
females, whose larval young drop out and behave just as he says when they
are torn in two.—These were the first observations ever made on the
reproduction of Anguwillula.

LETTER 18. VINEGAR, GINGER-WATER 153

had broken in pieces, lie a-writhing, and remain alive so
long, that it wearied me to keep my eye upon it. I have
also seen two small living eels come forth from an eel
after I had cut it in pieces: and they moved themselves,
and swam, and were in bigness like the smallest sort. To
sum up, the more observations I made on this matter,
the clearer did I demonstrate that the small living eels
come out of eels: and I conceive also that ’tis certain
I have seen the little eels alive in the big eels; but this
came to my notice only when I had taken the big eels
out of the vinegar, and when they lay a-dying.’

[ Observations on Ginger-water. |

The 6th of May, 1676, I put into a porcelain tea-cup,
which holds a little more than 24 ounces of water, three
of the ordinary large pieces” of ginger, after I had first
of all bruised them a bit with a hammer; merely with
the idea of seeing if the snow-water which I poured on
the ginger would bring forth living creatures with it.

The 14th ditto. I observed this water almost every
day, but till now I could perceive no living animalcules ;
and by this time the water was so dried up, or drawn into
the ginger, that I poured fresh water upon it.

The 29th ditto, having again examined this water
almost from day to day since the 14th, I now discovered

* L. at this point enters upon a long digression (about one whole page),
in which he describes and discusses the structure of the peppercorns them-
selves and attempts to explain why they have a hot taste. This leads him
further to discuss the constitution of wheat and other kinds of grain, and
several physiological problems suggested by his observations. After this he
suddenly returns to his experiments with infusions, and at this point I have
resumed my translation. The observations here omitted have no interest
from a protistological standpoint.

* clawwen MS. UL. evidently means the broken pieces of the dried
rhizome of the plant, as commonly sold by apothecaries.—I am informed
that the irregularly branching pieces of rhizome are known in the trade as
“hands” of ginger: and I take it that L.’s “ claws” were the broken-off
“fingers” of such “ hands”’.

154 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

some very little animalcules, a bit longer and bigger than
the small animalcules seen by me in the pepper-water.
Nevertheless, these had a different form and motion;
for while the animalcules in the pepper-water went
forward all winding-wise, these animalcules all advanced
in jumps, hopping like a magpie: yet were they very
few in number.’

The 30th of May, observing the ginger-water anew, I
discovered at least 25 times more animalcules therein
than previously. Among them were some quite three
times as long as broad, and I fancied I saw that their
fore and hind ends were fashioned aslant:; that is, with
an acute angle and an obtuse angle, as I have said before”
of a like sort that were bigger. Ditto, about 10 o’clock
at night, the said animalcules seen in greater number.

The 31st ditto, the foresaid animalcules seen in still
much greater number, amounting to several thousand in
one drop of water: and some of them exceeded the others
in length.

The Ist of June, the animalcules seen in still greater
number.

The 3rd ditto, the animalcules seen in such a vast
number (in the water that I took from above, off the
surface of the water), that were I to declare, according to
my own judgement, how many thousands there were in
one drop of water, ’twould not be believable.

The 4th of June, the water was again so evaporated
away, that the bits of ginger began to lie dry; so I poured
on rain-water at this time.

The 10th ditto, upon the water lay a thick film, which
I took off: and I then saw some oval animalcules,* in size
and shape like those that I have said were in the pepper-
water.

" From the description of its jumping movements, this was probably a
Cyclidium—noted earlier.

” See p. 132, 1st observation on pepper-water. ? Bodo sp.
* Ciliates, but otherwise unidentifiable.

1

LETTER 18. GINGER- AND CLOVE-WATER 155

The llth ditto, the oval animalcules were in greater
number, mostly swimming at the top, against the thin
film that had come again over the water. On this
occasion I marvelled to see the violence that the first-
mentioned little living creatures’ exercised, whenever
they came out of the water on to a dry place, ere they
fell a-dying.

The 12th ditto, the oval animalcules were now in great
plenty, as well as the other animalcules: and because the
film that lay upon the water had grown in thickness, I
poured the water and ginger away.”

[Observations on Clove-water. |

On the 17th of May, 1676, I placed 36 cloves in some
24 ounces of rain-water, after I had first of all examined
the rain-water and found nought therein (so far as
animalcules are concerned), save a very few creatures
that were roundish, and which looked to my eye, through
my microscope, no bigger than a coarse sand-grain doth
to one’s naked eye.

The 25th of May. Up to this date I could perceive no
living creatures, notwithstanding the many observations
I had made since the 17th of this month. I now added
more rain-water (wherein I could discern no animalcules)
to the cloves.

The 12th of July. After I had made divers observa-
tions on this water, and between-times had filled up the
tea-cup with water once more; and having no thought
that I should discover living creatures in this water, so

i.e., those seen on May 29 (? Cyclidiwm).

? T. again digresses at this point in order to describe the structure of
the macerated ginger itself. After a long description and discussion—
occupying more than one whole page of the MS.—he returns to the subject
of animalcules, and at this point my translation is resumed. Nothing of
protozoological or bacteriological importance is contained in the lines which
I have omitted.

156

1

LEEUWENHOEK AND HIS “ LITTLE ANIMALS ’”’

that I did not examine it from day to day, and kept no
note of when I last added water thereunto: on this date
I discovered very many living creatures, which displayed
themselves, through my microscope, as no bigger than an
ordinary sand-grain to the naked eye. These were very
clear, and seemed to be about twice as long as broad.
Along with them were some few animalcules which looked
as big as ordinary ant-eggs’; the upper part of their body
being round and raised, the under part flat, like unto
tortoises in shape. ‘Their whole body seemed to be made
up of no other parts than big and little globules, which
were all very glittering, so long as the animalcules were
alive: but when I brought them into a dry place (where-
upon they oft-times burst asunder), the glittering went
off; and the globules became smaller, and flowed away
on all sides, together with some watery humour in which
these globules lay. These animalcules were provided
underneath the body with divers little legs, whereof 5 or 6
stuck out in front of the head during motion.

The 14th ditto, I discovered many more animalcules
than heretofore, but most of them were very small.

The 19th ditto, I discovered, besides the said creatures,
many animalcules with tails,” along with many long
animalcules that were fashioned aslant in front; and if I
saw aright, their hindmost part was somewhat cloven,
their body flat below and round above, their length well
anigh that of the little oval animals.

The 4th of August, I did not perceive the long
animalcules, but exceeding many very little animalcules,
and some few that were a bit bigger. The water being
now almost evaporated away, I added well-water to it.

i.e., they appeared, through the microscope, about as big as “ ant-eggs”’

appear to the naked eye. (In a later letter L. showed that the structures
commonly called “ ant-eggs’’ are not really the ova of the ant, but its pupae.
Cf. Letter 58, 9 Sept. 1687.) From the deseription which follows, they
were obviously hypotrichous ciliates: but it is impossible to identify them
more precisely.

* i.e., some species of Vorticella. Cf. p. 118.

LETTER 18. CLOVE-WATER Loh

The 8th ditto, I saw very many animalcules whose
figure was like an oval, and these were to my eye, through
my microscope, like coarse sand-grains to the naked eye;
and there were some few animalcules with tails; likewise
some little animalcules, and plenty that were bigger, and
had the length of the eye of a louse. These were bent a
bit crooked, the underneath part flat; and therewithal
looking much like an eighth part of a preserved citron-
peel. Their motion was all turning about, so that I am
persuaded that they had no little legs; and though they
were a bit smaller, they resembled very closely the little
animals previously likened to a piece of citron-peel. So
great was their number, that it did not amount to a mere
thousand or two in one drop.

The 17th of August, the animalcules found as before ;
but their motion was very slow: and as over a half of
this water was evaporated away, I added well-water to it
again.

The 18th ditto, the animalcules as before, and now
their motion was a bit quicker again; and I now saw
again more animalcules with tails.

The 20th ditto, the animalcules with tails were so
multiplied, that by now they were the most plentiful.

The 21st and 22nd ditto, the animalcules with tails
were now less, and their motion, too, was very slow.
Furthermore, these animalcules with tails, whenever they
got themselves stuck by the tail in any bit of dirt,
stretched ’emselves out somewhat longer than the
animalcules with tails which I have seen in pepper-
water. The little animalcules were now also less; and
here and there [ discovered one of the animalcules that
I have likened to an eighth of a citron-peel.

The 3rd September, I took one or two cloves out of the
water, and they were now become so soft that one could
rub them to bits between one’s fingers: and moreover, I
found but little savour in them. The animalcules were
now much decreased, and therefore, as the water was also

158

cc

LEEUWENHOEK AND HIS LITTLE ANIMALS ”

diminished, I poured in well-water, in which were living
animalcules. After the lapse of an hour, I examined this
water; and whereas I had seen before very few of the
animalcules inclining to an oval figure, I now saw many
of them, together with animalcules that were twice as
long as broad, besides the animalcules that were in the
well-water, and a very few animalcules with tails. I
added 8 fresh cloves to this water, wondering whether
the animalcules in it would then die.

The 4th of September, the animalcules as before,
saving that the animalcules with tails were so diminished,
that I descried but 2 or 3 of ’em.

The 5th ditto, the animalcules inclining to an oval
figure were in greater plenty; and I saw a few of those
that were twice as long as broad, but none of the animal-
cules that had been in the well-water, nor of the
animaleules with tails.

The 6th ditto, I perceived no other animalcules than
those tending to an oval.

The 7th of September, saw animalcules which inclined
to an oval, without being able to make out any other sort.
However, they were decreased rather than increased, and
their motion was not quicker, but rather slower.

The 8th of September, the motion of the animalcules
even slower, and they were no more plentiful.

The 9th ditto, in the morning, at 8 o’clock, the animal-
cules as before: and because the motion was so slow,
I added a little well-water. And in this well-water there
were many very little living animalcules. Dvtto, in the
afternoon, at 4 o’clock, I now saw the animalcules that
had been in the well-water still alive in plenty in this
clove-water; and the other animalcules were now moving
more lively. Ditto, in the evening at 8 o’clock, the
animalcules that had been living in the well-water were
now almost all of them dead; so that I was able to see
but 2 or 3 alive after several observations.

The 10th ditto, at 9 o’clock in the morning, no animal-

LETTER 18. CLOVE- AND NUTMEG-WATER 159

cules seen except those inclining to a round oval figure ;
but the motion of these was a bit nimbler, and they were
no less in number.

The 18th of September. The animalcules inclining to
a round oval figure are got less from day to day since the
10th of this month, so that at this time I was able to see
only a very few of them; but now I saw some extra-
ordinary tiny animalcules, which looked, through my
microscope, no bigger than common sand doth to the
naked eye.

The 19th ditto, stirring the water around a little, and
then examining it, I saw more of the animalcules likened
to a round oval than before this date. Along with them
I perceived the very little animalcules.

[Observations on Nutmeg-water. |

The 13th of July, 1676, I beat some big nutmegs in
pieces with a hammer, and put them in 24 ounces of
well-water. ‘This well-water I had divers times examined
during the summer till this date, but could yet discover
no living creatures in it, save now and then so few and
extraordinary small, that I did not see them till I had
made several observations.

The 17th ditto. Divers observations made since the
13th of the month, but no living creatures perceived
therein. And now the nutmegs lay on top, against the
surface of the water. The water itself lay fermenting, as
if it had been fresh beer: and betwixt the bits of nutmeg
lay a lot of round particles of oil, which were very supple.
These were for the most part 1000 times smaller’ than
a small sand-grain.

The 19th ditto, the fermentation was all done with, and
the nutmegs mostly sunken to the bottom.

ee

1 je., in bulk: or, in other words, they had a diameter of about one-
tenth of that of a small sand-grain—on L.’s scale, about one thousandth of
an inch, or 25.

160 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

The 24th of July, the water was for the most part dried
up. I again added well-water thereto; and in this well-
water there were now many very little living creatures,’
which, whenever the well-water came under the water
containing the nutmegs, died in a trice.

The 3rd of August. Made divers observations since
the last foregoing date, but discovered no living creatures
in this water till to-day. The creatures now seen’ were
very few, and so small, that they well-nigh escaped the
sight, notwithstanding that one had a very good micro-
scope. And as the water was, for the most part, dried
up again, and very many living creatures were at this
time present in all the common kinds of water, I poured
on some snow-water, in which there were no animalcules.

The 4th ditto, the animalcules as before; and they
moved among so many various particles, of very near the
same bigness as the animalcules themselves, that you
would say, ’twas no mere water in which the nutmegs
lay ; for twas made up of soft fluid particles stuck beside
one another, much as if you beheld, with your naked eye,
the spawn of frogs, or the seed of fishes when it is spent.’

The 5th ditto, I saw plenty of animalcules, which I
can’t call long, they looked to me to be round rather ;
for they were no bigger, through my microscope, than
very little sand-grains to one’s naked eye; and I must
say, that I deem them to be a good three or four times
smaller than the thickness of the hair of a mite, or one
of the little hairs wherewith the body of a louse is beset."

The 6th ditto, the animalcules as before.

The 7th ditto, I saw a huge number of exceeding
minute animalcules.

* Probably bacteria and monads.

* Bacteria.

? I, doubtless observed, on this occasion, bacterial “ zoogloea’”’ mixed
with particles derived from the macerated nutmegs.

‘ Cf. p. 337 infra. The very minute animalcules here mentioned were
undoubtedly bacteria.

LETTER 18. NUTMEG-WATER 161

The 17th ditto, I perceived no animalcules ; and as the
water was much evaporated away, I added well-water, for
want of snow-water.

The 18th ditto, no animalcules made out.

The 19th of August, many small animalcules seen
again.

The 20th ditto, the animalcules as before.

The 21st ditto, the small animalcules seen in greater
number. I likewise now saw some, though very few, that
were a bit bigger. These last were very nearly round,
only tending somewhat to an elliptical figure.

The 23rd ditto. Besides the said animalcules, I dis-
cerned, both now and yesterday, divers animalcules that
were twice as long as broad, running to a point before
and behind, and of the size of those in the pepper-water ;
but their motion was not so quivering. I fancied the
cause of this was that this water was thicker.

On the 3rd of September, I could perceive no animal-
cules. The water being now for the most part evaporated
away, I added well-water, wherein were very many little
animalcules. I also took a little bit of nutmeg out of the
water, and tasting it upon my tongue, found it was still
so strong that it surpassed many fresh nutmegs in savour.

The 4th ditto, the exceeding very little animalcules
now seen alive once more.

The 7th of September, the very little animalcules seen
alive, as before; yet could I discern no animalcules of
the sort that were in the well-water ere I put it to the
nutmegs. My further observations I have not writ
down.’

The objection hath divers times been urged against me,
that there are, hovering in the air, extraordinary small
living creatures, which are hid from our eyes, and can

" The record of observations ends at this point.
1a!

LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS”

only be discerned by means of surpassing good magni-
fying-glasses, or telescopes; and these creatures, they
say, have been seen in Rome.’ For my part, notwith-
standing the manifold observations I have carried out to
this end, I have as yet seen no lesser animalcules moving
in the air than those which are so big that you can
readily make them out with the naked eye. The very
little particles which I have commonly found in the air,
and which are there in motion, are all earthy particles,
which are given off by (so to speak) “ dustsome ” ’ things.
For you can’t tear a sheet of paper apieces, but what
more than a thousand very tiny fibres break off, and these
so light withal, that they can’t easily fall upon the earth,
owing to the motion that is in the air: you can’t draw a
comb through the hair of your head, but what various
very little particles, which lie or are stuck upon every
hair, are set loose and moved in the air; not to mention
the wearing away and the breaking off which each several
hair suffers in the act of combing. Nor can you so much
as rub your hands together, when they are dry, nor stroke
your face, without thereby imparting a multitude of tiny
scaled-off particles to the air; and ’tis even so with wood,
earth, smoke, etc. Such particles as these would seldom
fall upon the earth, so long as they be in the sun’s rays,
or in a light breeze; but on coming out of the sun’s rays,
and out of the strong motion of the air, they sink towards
the earth: and these little bits of dust thus lying still,
and not sticking to larger particles that are heavier, may
again be set a-moving by the mere motion of the air, or
the sun’s rays. From what observations I have made
hereon, I can’t say I ever saw, among the rest, two bits
of dust that exactly agreed with one another in shape.
But I'll not deny that there can be, in the air, any living
creatures which are so small as to escape our sight; I say

1

2

A rumour, I take it, of the imaginative work of Athanasius Kircher.
stofligte MS. lL. here invents a word meaning “ apt to form dust.”

LETTER 18. CONCLUSION 163

only that I haven’t descried them. And furthermore, I
am persuaded that they would not be able to remain alive
in the air, about our horizon; rather would they be
begotten in the clouds, where, in the continual dampness,
they could remain alive, and so be conveyed still living to
us in mist and rain. I fancy I have even seen something
of the sort in the early summer of this year, on two
several occasions, when there was a heavy mist here; but
I saw the supposed creatures without any motion. And
I believe I have now found out a means of performing
such observations more exactly and nicely in future.
These observations concerning living creatures, in the
liquors spoken of, were indeed deserving of closer atten-
tion and description ; but for that, there had been need
too of a whole man, which my circumstances did not allow
of: for I have employed only my spare time upon them.’

Much light is thrown on the observations recorded in the
foregoing letter by some of the Huygens correspondence. As
the relevant MSS. are now accessible in print, and as it would
take us too far afield to discuss the position of Huygens as
a protozoologist, I shall not now consider this correspondence
in detail. It is so important, however, that it cannot here be
ignored, and I therefore add the following notes by way of
supplement.

Christiaan Huygens never himself published any serious
contributions to protozoology: and the records of his own
observations, which were made in an attempt to repeat
Leeuwenhoek’s experiments, remained in manuscript and
unknown until only a few years ago. Consequently, his
private work” had no influence whatsoever upon the progress

' A few final remarks—having no bearing upon animalcules—are here
omitted.

* Published for the first time in Gwvres Compl. de Chr. Huygens: see
particularly Vol. VIII (1899), No. 2148, p. 122; and Vol. XIII, fase. ii
(1916), p. 698 sq. So far as I am aware, all that was previously known
about Huygens’s protozoological work is contained in the fragmentary notes
in his Opuscula Posthuma (1703) and Opera Reliqua (1728). These show
only that he was an imitator of L., and give no idea of the originality of
his own observations. There is also a reference to the subject in Gregory
(1713), however, while contemporary mention was made of his observations
in the Journ. d. Scav. for 1678.

ce

164 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”

of protozoology. Had it been published in his lifetime, it would
have assured him a place in the very forefront of the founders
of the science. Even at the present moment the excellence
and originality of his observations have been largely obscured
by his modern editors. In my opinion most of the protozoa
described and roughly sketched by Huygens can be easily
recognized by any competent protozoologist, yet his editors
have not only failed to recognize the majority but have often
misidentified common species most ludicrously. As examples,
I may note that Huygens’s unmistakable account of Chilodon
(with figures, including a characteristic pair in conjugation)
is interpreted as “ probably infusoria of the genus Bursaria”’:
his description of Astasia, with its characteristic euglenoid
movements and “ hardly any colour”’, is said to suggest the
bright green and rigid Phacus—“ if having hardly any colour
be not taken to exclude a slight green coloration’: and so on.
But we are here concerned with Leeuwenhoek—not with
Huygens—so I shall say no more on this matter now. I
hope to deal with Huygens’s admirable observations on another
occasion.

Whilst Leeuwenhoek’s astonishing researches were being
considered by the Royal Society, he himself was continuing
them and was corresponding with Constantijn Huygens (pater)
about his discoveries. Sir Constantijn was also in frequent
communication with his son Christiaan, at Paris, to whom he
reported Leeuwenhoek’s findings. Christiaan, at first sceptical,
soon repeated and confirmed the experiments: and at the end
of 1678 he wrote a most interesting letter,’ accompanied by a
few sketches, to his elder brother Constantijn. In this letter
Christiaan gave unmistakable’ descriptions of Chzlodon,
Paramecium, Astasia, and Vorticella—all found in infusions:
and he added “I should much like to know what Leeuwenhoek
would say about all this, and whether he has seen anything
like them.” Evidently the letter was sent to Leeuwenhoek,

who wrote to Constantijn Huygens sen. about it a little later.’

" Chr. Huygens to Const. Huygens jun. 18 Nov. 1678. Printed in
Guvres Compl. Vol. VIII (1899), No. 2148, p. 122.

* To me they are all unmistakable in this description: and when the
notes of 26 July 1678 (published in Guvr. Compl. XIII (ii), 702) are also
taken into account, the identifications are surely beyond all doubt.

* Leeuwenhoek to Const. Huygens sen. 26 Dec. 1678. Letter printed in
Gwor. Compl. VIII, No. 2156, p. 140.

APPENDIX TO LETTER 18 165

Leeuwenhoek here says that he can recognize all the animal-
cules described by Christiaan, and notes where he had himself
observed them previously. But he makes one obvious though
natural mistake: he takes Huygens’s Astasia for the Dileptus
which he himself discovered, and on which he had observed
the cilia. Apart from this, Leeuwenhoek interpreted Huygens’s
protozoa conformably with my interpretations of his own.
Huygens observed not only the protozoa which Leeuwenhoek
discovered in pepper-water, but he also saw and delineated
(his fig. F.) the long thread-bacteria so commonly seen in
infusions. On these organisms Leeuwenhoek comments :

These long eels I have seen too. My wonder at these
animals, was because one was 3 or 4 times as long as
t’other, yet they were always of the very same thickness ;
and besides, they swam as well backwards as forwards,
without my being able to make out any head, or anything
that looked like a head. I have already written about all
this to the Royal Society at London’. :

This is an important passage, as it confirms what Leeuwen-
hoek had previously said about bacteria. A little later he
adds the following remarks, with which we may conclude this
first chapter in Protozoology :

All these animalcules aforesaid I found too in ordinary
water, though not so many by a long way as in pepper-
water. And in the summer, when I feel disposed to look
at all manner of little animals, I just take the water that
has been standing a few days in the leaden gutter up on
my roof, or the water out of stagnant shallow ditches:
and in this I discover marvellous creatures.

And whether I put in the water whole white pepper,
black pepper, coarse pounded pepper, or pepper pounded
as fine as flour, animalcules always turn up in it, even on
the coldest days in winter, provided only that the water
doesn’t get frozen.

This day [26 December 1678] there are in my pepper-
water some animalcules which I judge to be quite 8 times

* See p. 140 above.

166

cc

LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS”

smaller than fig. A.,* on which I can make out the paws
too, which are also pleasant to behold, because of their
swift motions. The paws of these animalcules are very
big, in proportion to their bodies.” Besides these animal-
cules, I discovered in pepper-water, some few weeks since,
yet others which I judge to be a good 1000 times less
than the animalcule in fig. A: for the circumference of
the whole body of one of these extreme small creatures is
no bigger than the thickness of a paw of the animalcule
in fig. A: and I am persuaded that thirty million of these
animalcules together wouldn’t take up as much room, or
be as big, as a coarse grain of sand.

Ajo ee ie Dee TR oy a ein oee DS a eee
' Referring to Huygens’s sketch of a small (and unrecognizable) ciliate.

> Ly. probably here refers to the cirrhi on a small hypotrichous ciliate
such as Huplotes.

167

CHAPTER 2

EPILOGUE TO LETTER 18. FURTHER OBSERVA-
TIONS ON THE FREE-LIVING PROTOZOA AND
BACTERIA

(LETTERS 19, 21, 23, 26, 29a, 30, 31, 32, 33, 71, 92, 96)

S we have already seen, Leeuwenhoek communicated his

A discovery of the Protozoa and Bacteria not only to the

Royal Society but also to Sir Constantijn Huygens.

The latter evidently wrote a reply—which is lost—to which
Leeuwenhoek rejoined, inter alia’:

In order to answer Your Excellency’s letter further, I
must yet wait 2 or 3 weeks, for the reason that I have to
repeat the observations I made some time since (concern-
ing the living creatures in water) with two kinds of
water, which, among others, I intend to study every day.

From these words it may be inferred that at the beginning
of 1677 Leeuwenhoek was still hard at work on his discoveries.
But the Royal Society also did not remain idle or disinterested :
the Fellows wanted to know more. Consequently, in an
editorial comment upon Leeuwenhoek’s observations on the
animalcules in pepper-water “—wherein he says that he saw
‘ several thousands of the very small animalcules”’ in a single
drop of liquid—Oldenburg remarks*: “ This Phaenomenon,
and some of the following ones seeming to be very extraordinary,
the Author hath been desired to acquaint us with his method of
observing, that others may confirm such Observations as these.”

"From Letter dated 15 February 1677. To Const. Huygens sen. The
original Dutch MS. is at Leyden, and has recently been printed in Zwvr.
Compl. de Chr. Huygens (1899), Vol. VIII, No. 2099, p. 21.

* See p. 135 supra, 2nd observation on pepper-water: 24 May 1676.

® Phil. Trans. (1677), Vol. XII, p. 829.

168 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

To Oldenburg’s inquiries Leeuwenhoek sent the following
characteristic reply’:
Your very welcome letters of the 12th and 22nd
ultimo” have reached me safely. I was glad to see that
Mr. Boyle* and Mr. Grew* sent me their remembrances :
please give these gentlemen, on my behalf, my most
respectful greetings. “T'was also a pleasure to me to see
that the other Philosophers’ liked my observations on
water, etc., though they found it hard to conceive of the
huge number of little animals present in even a single

"Letter 19. 23 March 1677. MS.Roy.Soc.—The greater part of this
letter was translated into English and published in Phil. Trans. (1677),
Vol. XII, No. 134, pp. 844-846. The original MS., in Dutch, is accompanied
by a MS. translation into Latin, concerning which L. makes the following
statement in a postscript (in Dutch, which I translate): “ Sir, seeing that
you are most times hard pressed to find time to translate my observations
into the English tongue, and mentioning this to a gentleman who hath
divers times been to visit me; this gentleman offered me his services, to
translate into Latin such of my observations as I may perchance com-
municate to you: which offer I did not decline, and I now send you his
Latin copy herewith, along with my own letter. I await your answer, and
would know if I can serve you by acting in this way in future.” Although
Oldenburg’s translation is said to be “ English’d out of Dutch’, it appears
to me almost certain—from comparison of the three versions—that the
English was really rendered from the Latin, and not from the Dutch copy.
My own translation—above—is from the latter, written in L.’s own hand.
This will explain several slight discrepancies between Oldenburg’s version
and mine. It must be added that L. himself also printed a considerable
extract from this letter, at a later date, in his Letter 96 (9 Nov. 1695)—
published in the Dutch and Latin works.

*7.e., February 1677.

*The Hon. Robert Boyle (1627-1691)—“ Father of Chemistry and
brother of the Earl of Cork.”

“Nehemiah Grew (1641-1712), to whom several of L.’s most interesting
letters were addressed, was a Doctor of Medicine (Leyden, 1671) and
Secretary of the Royal Society from 1677 to 1679. He was educated at
Pembroke Hall, Cambridge, and became a Fellow of the Society in 1671:
but he is best known for his botanical work, and his catalogue of the
Society's museum. As a botanist he was the rival of Malpighi, and a
pioneer in the study of vegetable morphology. His later work is deeply
tinctured with religion. (His father, Obadiah Grew, was an ejected
minister of the English Church.) For his biography see the Dict. Nat.
Biogr. and Arber (1913).

*de Heeren Philosophen MS.—i.e., the Fellows of the Royal Society.

LETTER 19. 23 mMARCH 1677 169

drop of water. Yet I can’t wonder at it, since ’tis
difficult to comprehend such things without getting a
sight of ’em.

But I have never affirmed, that the animals in water
were present in such-and-such a number: I always say,
that I imagine I see so many.

My division of the water, and my counting of the
animalcules, are done after this fashion. I suppose that
a drop of water doth equal a green pea in bigness;* and
I take a very small quantity of water, which I cause to
take on a round figure, of very near the same size as a
millet-seed. ‘This latter quantity of water I figure to
myself to be the one-hundredth part of the foresaid drop :

4s for I reckon that if the diameter of a millet-seed

45° be taken as 1, then the diameter of a green

225 -pea must be quite 43. This being so, then a
_— + quantity of water of the bigness of a millet-seed
20m”, maketh very nearly the sz part of a drop, ac-
cording to the received rules of mathematicks

00 ©. (8.-« Shown. in the margin). This amount of
~ 91] Bas water, as big as a millet-seed, I introduce into

a clean little glass tube (whenever I wish to
millet-seeds
equalone let some curious person or other look at it).
Sie This slender little glass tube, containing the
(vobmme)- “water, I divide again into 25 or 30, or more,
parts; and I then bring it before my microscope, by
means of two silver or copper springs, which I have
attached thereto for this purpose, so as to be able to
place the little glass tube before my microscope in any
desired position, and to be able to push it up or down
according as I think fit.

I showed the foresaid animalcules to a certain
Gentleman, among others, in the manner just described ;
and he judged that he saw, in the zoth part of a quantity

'In Letter 96, L. tells us that his standard “ green pea”’ weighed 8 grains.
See p. 214 infra.

170

LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

of water as big as a millet-seed, more than 1000 living
creatures. This same Gentleman beheld this sight with
ereat wonder, and all the more because I told him that
in this very water there were yet 2 or 3 sorts of even
much smaller creatures that were not revealed to his
eyes, but which I could see by means of other glasses
and a different method (which I keep for myself alone).
Now supposing that this Gentleman really saw 1000
animalcules in a particle of water but soth of the bigness

of a millet-seed, that would be 30000 living
Shoe creatures in a quantity of water as big as a
9730000 +4+%millet-seed, and consequently 2730000 living

creatures in one drop of water. Otherwise, I
imagine the quantity of water to be of the bigness of a
coarse sand-grain; and in this quantity I imagine that
I see upwards of 1000 living creatures. Now I take it
that the bigness of a coarse grain of sand beareth the
following proportion to a drop of water: If the diameter
of a sand-grain be 1, then that of a drop of water is more
than 10, and consequently a drop of water is more than
1000 times bigger than a sand-erain. ‘Thus there are
more than a thousand times a thousand living creatures
in a drop of water. Tis in such a fashion that I make
my uncertain and imaginary reckoning of the animalcules
in water: but I guard myself, so far as ‘tis possible,
against making the number too big, as you can see from
the foregoing lines of my letter, wherein I have made
the number not half so big as others well might do.

My counting is always as uncertain as that of folks
who, when they see a big flock of sheep being driven,
say, by merely casting their eye upon them, how many
sheep there be in the whole flock. In order to do this
with the greatest exactness, you have to imagine that the
sheep are running alongside one another, so that the flock
has a breadth of a certain number: then you multiply
this by the number which you likewise imagine to make
up the length, and so you estimate the size of the whole

LETTER 19. METHOD OF OBSERVING lg

flock of sheep. And just as the supposed number may
differ from the true number by fully 100, 150, or even 200,
in a flock of 600 sheep, so may I be even more out of my
reckoning in the case of these very little animalcules: for
the smallest sort of animalcules,’ which come daily to my
view, I conceive to be more than 25 times smaller than
one of those blood-globules which make the blood red 5
because I judge that if I take the diameter of one of
these small animalcules as 1, then the diameter of a
blood-globule is at least 3.

These, Sir, are the trifling observations which I have
shown to divers curious persons, to their great satisfaction ;
but the other things that I have seen, and my particular
microscope, I cannot yet resolve to make public: which
I beg you, Sir, and your fellow philosophers, not to take
amiss.

Since sending off my letter” concerning the little
animals in water, I’ve not remained idle; but I have con-
tinued to examine divers sorts of water, examining even
that which was distilled or boiled. During the last sharp
spell of cold, when all the little animals had perished, I let
the water thaw by the fire; and when it had stood a whole
day in my bedchamber, with the fire kindled all the time, I
saw, after the lapse of 24 hours (and at another time after
17 hours), that living creatures had come again in the
water. Upon this subject I might, indeed, say something
further; but I note that my former letter is still under
your consideration, so I will spare you more.

To give your Philosophers further assurance, con-
cerning the reality of the multifarious living creatures in
even only a very little quantity of water, ‘tis my intention,
when they appear again in great plenty in the water, to
obtain testimony thereof, which I shall then send you.

The foregoing Letter was read at the meeting of the Royal
Society on 5 April 1677 [O.S.]; and the observations excited

‘7.e., Bacteria.
? Referring to Letter 18 (p. 117 swpra).

ie LEEUWENHOEK AND HIS ‘“ LITTLE ANIMALS ’”’

so much interest that the Secretary (Nehemiah Grew) was
ordered to repeat Leeuwenhoek’s experiments, for the greater
satisfaction of the Fellows.’

In a further communication on the same subject—and
various others—Leeuwenhoek fulfilled his promise to send
the testimony of divers credible eye-witnesses in support of the
truth of his statements. To a modern worker it seems some-
what curious that a scientific observer should think of calling
in such people as notaries public and ministers of religion to
vouch for the accuracy of his observations: but Leeuwenhoek
could think of no better method of establishing his bona fides,
and the result was, no doubt, satisfactory to all parties con-
cerned. It should be remembered that Leeuwenhoek’s
reputation was not yet firmly established at this early stage in
his scientific career, and we know that certain people had
already expressed their doubts as to the accuracy of his
observations. Among them was Christiaan Huygens, who,
writing to Oldenburg in 1675, says: “I should greatly like to
know how much credence our Mr Leeuwenhoek’s observations
obtain among you. He resolves everything into little
globules; but for my own part, after vainly trying to see some
of the things which he sees, I much misdoubt me whether
they be not illusions of his sight ; especially when he professes
to discover the particles whereof water, wine, and other
liquors, are composed.” It was this scepticism regarding
his researches, apparently, which caused Leeuwenhoek to
send those long and detailed extracts from his note-book—
which, as already noted, are peculiar to his 18th Letter—to
the Royal Society. The disbelievers, therefore, did a signal
service to posterity; for they put Leeuwenhoek on his mettle,

"Cf. Birch, Vol. III, p.338: “It was ordered, that Dr. Grew should be
desired to try what he could observe in the like waters; and that for this
purpose an extract should be given him by Mr. Oldenburg of Mr.
Leewenhoeck’s observations formerly read to the Society.”

* Huygens to Oldenburg ; 30 January 1675. MS.Roy.Soc. This letter
has lately been published in (uur. Compl. de Chr. Huygens, Vol. VII,
No. 2003, p.399. The original is in French, and the above is my
translation of the passage in question—-Huygens was mistaken in
supposing that L. laid claim to having detected the particles (molecules)
of which water and other liquids consist—as is abundantly proved by L.’s
own statements: see, for example, his letter to Const. Huygens (20 May
1679) translated on p. 187 infra.

LETTER 21. 5 OCTOBER 1677 iV (e:

and thereby enabled us to read today a detailed record of some
of the most remarkable and original researches ever executed.

The further communication referred to above is
Leeuwenhoek’s 21st Letter—according to my reckoning—
and the passages in question are as follows’:

In my letter of 23 March, 1677, I demonstrated that
one drop of water (which is as big as a green pea) is
equal in volume to 92%” millet-seeds: and to bring it
home to some friends of mine who could not grasp this,
I took 6 millet-seeds and stuck them alongside one
another with a little pitch. Then, with a pair of callipers,
I took the width of the axes of the said millet *-seeds, and
found the distance between the points was equal to the
axis of a big currant; and I remarked that the cube of 6
is 216. Now, said I, let us put an uncertain for a certain
quantity; and let us say, that as the currant sinks in
water, and the millet-seeds sink likewise in water, they
are therefore of like gravity: this being so, then 216
millet-seeds should weigh as heavy as this currant. I
then placed the currant in a small but exceeding nice
pair of scales, and found that 212 millet-seeds were of
equal weight with the currant.

I said also* that when I should again have a great
number of living creatures in water, I would send you
testimonials thereof, for the satisfaction of yourself and
the other Philosophers: these I now send you herewith,
from eight several Gentlemen, some of whom say that

nn

"From Letter 21. 5 October 1677. To Oldenburg. MS.Roy.Soe.
An English abstract was published by R. Hooke in his Lectures and
Collections (1678), Part II; Letter I, pp. 81-83. (Also reprinted in Hooke’s
Lectiones Cutlerianae, 1679.) Apparently this letter, though sent to
Oldenburg, came into Hooke’s hands when he succeeded him—after his
death—as Secretary of the Society.—This letter is called “ [26] Brief 18B”’
by Vandevelde (1922, p.356), who, as he was unaware of the existence of
the original MS., could assign no date to it. My translation is made from
the manuscript itself.

? This is a mistake. It should be 91 (91°125). See p. 169 supra.
® In the MS. the word geerst (= millet) is here miswritten “ geest’’.
* 7.e., in his letter of 23 March 1677. See p. 171 supra.

174 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS ”

they have seen 10,000 living creatures in a parcel of
water the bigness of a millet-seed, while others say
80,000 and also 45,000. I have generally counselled
these Gentlemen, when giving their testimony, to put
down but half the number that they judged they had
seen; for the reason that the number of animalcules in
so small a quantity of water would else be so big, that
’twould not be credited: and when I stated in my letter
of 9 October, 1676, that there were upwards of 1,000,000
living creatures in one drop of pepper-water, I might with
truth have put the number at eight times as many. For
if there be, as the testimonial saith, 45,000 animalcules in
a quantity of water as big as a millet-seed, then
3? there would be 4,140,000 living creatures in a
50000 Crop of water: and over and above this vast
4050000 number, I cau say that I am able to discern at
4140000 times even as many other living creatures, which
are so little that they were hid from the sight
of the Gentlemen who gave their testimony. ‘The first
number, when doubled, amounts therefore to 8,280,000
living creatures in one drop of water. This is incon-
ceivable: but let us put it thus, that supposing a coarse
grain of sand be divided into 8,000,000 parts, then I do
indeed see little living creatures in water which are no
bigger than these particles of sand would be. And this
being conceived, ’twill not appear so marvellous.

The attestations' of the eight eye-witnesses have for-
tunately been preserved with the foregoing letter. There are
actually five of them, but one bears three signatures and
another two—making eight testimonies in all. One® is in

1 Presented at a meeting of the Society on 15 October 1677, and read on
November 1 [0.8.]. Cf. Birch, Vol. III, pp. 346, 347.

? By Alexander Petrie, son of a more famous father of the same name
(ca.1594-1662) who was a Scottish divine and minister of the Scottish
church at Rotterdam. The father’s life will be found in Dict. Nat. Biogr.,
but I have been unable to discover anything further about the son—the
present writer.

THE ATTESTATIONS 175

English, and is written and signed by the minister of the
English church at Delft. It is as follows’:

I underwritten, being willing to give testimony unto
that whereof I was an eye-witnesse, do declare that having
seen and read Mr Leewenhoecks letter of March 23. 1677.
as it is set down in the printed Philosophical Transactions,
Numb. 134. p. 844. I was desirous to see a proof of
what I found there related; and for my satisfaction, Mr
Leewenhoeck did put a litle quantity of water, about the
bignesse of a Millet-grain, into a very slender glasse-pipe,
on which looking through his Microscope, I did see a
very great number of litle animals moving in that water,
so many that I could not possibly number them, and to
my sight they seemed to exceed the number expressed in
his fore-mentioned letter: and moreover, being desirous
to see a proof whether those animalcula were indeed
living animals, Mr Leewenhoeck by adding a very small
quantity of vinegar to the same water, and putting it
again into the same glasse-pipe, I did see those litle
animals in the water, but they did not moove at all (being
killed by the vinegar) which I beheld with admiration,
that in so small a quantity of water I should see such a
vast number of those litle animals. Whereof, being
Testis oculatus, I was willing at the desire of ingenious
Mr Leewenhoeck to confirm the truth of his relation by
this testimony written and subscribed by me, in Delft,
Aug: =a HORT:
Alex: Petrie.
Pastor of the English Congregation in Delft.

The other testimonials are couched in similar terms. There
is a long one in Latin, signed by “ Benedictus Haan’ Pastor

* MS. Roy. Soe.

2 Benedictus Haan (sew de Haan) was Lutheran minister successively at
Breda (1666), Delft (1675), and Amsterdam (1692). He died in 1702, and
is otherwise dimly remembered as the author of sundry verses which,
according to van der Aa, afford very feeble proof of his ability as a poet.”

cc

176 LEEUWENHOEK AND HIS “ LITTLE ANIMALS

Luther: Delph:” and ‘ M. Henricus Cordes’ Past. Luth.
Hag.’ ; and there are two shorter ones in the same language
signed respectively by “ R. Gordon’ Medicinae Studiosus”’ and
the three following persons: “J. Boogert* J.U.L. et Notar.
Publ.” ; ‘“ Rob. Poitevin * Doct. m. monspel.” ; ‘“‘ W. V. Burch °
J.U.L. et coram curia Hollandiae advt.” The remaining
attestation is short and in Dutch, and is signed ‘“ Aldert
Hodenpijl.”’°

* Hendrik Cordes, Lutheran minister at The Hague from 1674 to 1678,
was the son of Paulus Cordes (1613-1674), who held a like office at
Amsterdam. Hendrik, who died in 1678, is known to students of Spinoza:
for his successor was the Colerus (Kéhler) who wrote the life of the Jewish
philosopher. Colerus (1705), speaking of Spinoza, says: “He had a great
esteem for Dr. Cordes, my Predecessor; who was a learned and good
natured Man, and of an exemplary Life, which gave occasion to Spinosa
to praise him very often. Nay, he went sometimes to hear him preach,
and he esteem’d particularly his learned way of explaining the Scripture,
and the solid applications he made of it. He advised at the same time his
Landlord and the People of the House, not to miss any Sermon of so
excellent a Preacher.” See Pollock (1899) p. 395.

*This was Sir Robert Gordon (1647-1704), who “travelled much into
foreign countries for his improvement, was a man of extensive learning and
knowledge, and particularly skilled in mechanics and chemistry.’’ He was
son of Sir Ludoyick Gordon, of Gordonstoun, Elginshire, and became a
Fellow of the Royal Society in 1686. (Cf. Birch, Vol. IV, pp. 454, 455.)
Owing to his scientific pursuits he became known in the neighbourhood
where he lived as “ Sir Robert the Warlock”. For his life see the Dict.
Nat. Biogr.

*J. Boogert. The letters J.U.L. stand for Juris Utriusque Licentiatus—
a degree inferior to that of Doctor. It is evident, therefore, that he was a
lawyer and notary public; and Mr Bouricius tells me further that his
forename was Johannes and he was the son of a physician. It is probable
that he was the Jan Fransz. Boogert (or Bogaert) mentioned in Boitet
(1729, pp. 453, 495) as one of the governors of the reformatory at Delft in
1677, and a governor of the poor-house in 1680. This J. B. died in 1702.

‘Robert Poitevin, Doct[or] m[edicinae] Monspell[liensis], I cannot
trace further: but I find that several other medical men with the same
surname also qualified at Montpellier, where other members of this family
resided. Perhaps he was the Leeuwenhoeks’ family physician. Astruc
(1767) makes no reference to him.

°W. vlan der] Burch. The words following his name show that he
was a barrister; and I think he must have been the Willem Reyersz. v. d.
Burch (1627-1712), sometime town-councillor and “ weesmeester”’ at Delft,
who is referred to in Boitet (1729, p.90 et alibi)—though Mr Bouricius
(in litt.) considers this doubtful.

*Aldert Hodenpijl. Mr Bouricius informs me that he was married to

TESTES OCULATI ney

All these attestations bear out what Leeuwenhoek himself
tells us in his letters. But they also tell us that the capillary
glass tube containing the animalcules was as thick as a horse-
hair * (Haan and Cordes), and that it was divided into a large
number of measured parts, though it contained but a droplet
of water no bigger than a millet-seed. Hodenpijl says the
animalcules looked to him as large as lice, or even larger’:
while Haan and Cordes declare that some of them appeared
as big as bugs."

To the testimony of these worthy men we may now add
that of Christiaan Huygens, who, at the end of his French
version of Leeuwenhoek’s observations,’ added the following
remarks of his own’: “These are the observations of Mr.
Leeuwenhoek. His manner of making them is to introduce
the water into very little glass tubes, one third or one quarter
of a line in diameter; and these he afterwards applies to his
microscopes. He showed me some of these little insects very
distinctly, continually tumbling about in the water”. We
may suppose, accordingly, that Huygens, when he wrote this,
had overcome his original scepticism regarding Leeuwenhoek’s
observations. Indeed, the demonstration of which he here
speaks was probably the stimulus which prompted him, soon

Judith le Roy, and he has found records of the baptism of three of their
children (circiter 1668): but he has been able to find out nothing of present
interest about him in the Archives of Delft. It seems probable, however,
that Aldert H. is identical with Aalbert H. who is recorded in Boitet (1729,
pp. 519-20) as having been schutterkoning (= champion shot) of Delft in
1661, 1665, and 1668. (The discrepancy between ‘‘ Aldert ”’ and “ Aalbert”
may be easily accounted for—Mr Bouricius assures me—by the “ general
slovenliness [slordigheid] in writing names at that time”.) Why L. sent
his testimony I do not know—unless it was because his pre-eminence in
shooting guaranteed the excellence of his eyesight.

‘ad crassitiem pili equini crasso MS.

* Haan and Cordes say 50 parts, Hodenpijl says 70, and Boogert and his
co-signatories say 90. No doubt the discrepancy is to be explained by the
circumstance that they recorded L.’s procedure on three different occasions.

* hebbende de groote van een luijs, en sommige grooter MS.

*apparebant ad magnitudinem cinvicis MS.

> See p. 115, note 6.

° Published in Guvr. Compl. de Chr. Huygens, Vol. VIII, p. 27. These

remarks remained in manuscript until 1899, when this volume was published.
The original is in French, and the above is my translation.

12

178 LEEUWENHOEK AND HIS “LITTLE ANIMALS ”’

afterwards, to make his own remarkable contributions to

protozoology.:
It cannot be doubted that the “ very smallest animalcules,”’

of which Leeuwenhoek himself speaks, were in reality not
protozoa but bacteria. The particulars which he records prove
this conclusively, and it is hardly necessary to make infusions
of pepper—as I have done*—to convince oneself of this:
while the fact becomes superabundantly clear from Leeuwen-
hoek’s next letter on this subject, which was written at the
beginning of 1678 and contains the following remarkable
passage *:

I can't help mentioning that I can now make out, very
plain and clear, the shape of those little animals of the
smallest sort, whereof I said before* that I could ascribe
no figure to them ; and this because of the pleasure that
I do take in their manifold delightful structures, and the
motions that they make from time to time in the water.
Upon the 4th of this present month,’ when it froze hard,
I did fill a small clean glass with pounded pepper to 3 of
its height, adding § of rain-water, and set it for the first
night in my bedchamber. The next day, it’ being well
softened, I put it’ in my closet; and within thrice 24

" See p. 163 supra.

? Cf. also Beijerinck (1913).

* From Letter 23,14 January 1678. This letter was written to Robert
Hooke, who published an incomplete English version of it in his Lectures
and Collections (1678), Part II; Letter 2, pp. 84-89. This translation was
made by Hooke himself: for in a letter to L., dated 10 March 1682 (MS.
unpublished), he says so, and adds: “I have as neere as I could followed
the sense of your Expressions though not verbatim.’’—I translate from the
original MS. I may add that this letter serves to confirm my numeration
of L.’s early epistles: for it is No. 23 according to my reckoning, and L.
himself refers to it in his 113th Letter as “my 23rd”. It was read at a
meeting of the Society on 24 Jan. 1678 (cf. Birch, III, 380), but is not to be
found in the Phil. Trans., nor in the Dutch or Latin editions of the letters.
Hooke reprinted his translation in Lectiones Cutlerianae, Part V (1679).

* Letter 18. (Seep. 143 supra.) The organisms referred to were evidently
bacilli.

° January, 1678.

® ¢.e., the pepper.

” i.e., the glass.

LETTER 23. 14 JANUARY 1678 179

hours I discovered in it’ so great a many of such incon-
ceivably small creatures, that a man’s mind may not
contain them all: and in my judgement, the sort that
were most plentiful were much more than 1000 times
thinner than a hair of one’s head, and 3 or 4 times as
long as thick. These would oft-times shoot so swiftly
forward with the hindmost part of their body, that you
might think you saw a pike darting through the water ;
yet each shoot was, in length, most-times about half a
hair’s breadth. ‘The figures of the other sorts of creatures,
whereof some were even less, I shall pass over, else
’twould take all too long a-writing: I will only say, that
in pepper-water, that hath stood somewhat long, I have
oft-times seen, among the extraordinary little animalcules,
little eels;? and the structure and the motions which
these had, was as perfect as in big eels. But they were,
to my eye, quite a thousand times thinner than a hair off
one’s head ; and if a hundred of these little eels were laid
out end to end, the whole length of them would not reach
to the length of a full-grown one of those eels that are in
vinegar.*
Leeuwenhoek’s next letter in which we find any mention
of protozoa was written in September of the same year (1678).
It also contains some observations of whose precise signifi-
cance I am uncertain: but it is so characteristic, and so
clearly reveals his method of working and ways of thinking,
that I cannot refrain from quoting it. This is what he there
Says’:

’ i.e., the pepper-infusion in the glass.

* Spirilla.

® Anguillula aceti—the “ vinegar-eel’’—which L. regarded as really a
little fish. Large specimens measure about 1:5 mm. in length: ef.
p. 335 infra.

“ From Letter 26. 27 September 1678. To Nehemiah Grew. MS.Roy.Soc.
Unpublished. (A poor contemporary English MS. translation accompanies
the original Dutch MS.) The above is my translation of a part of the
letter.—There is an important reference to this epistle in L.’s letters to
Magliabechi (vide Targioni-Tozzetti, 1745: Epist.I, Vol. II, p. 345); but
the observations on the reddening of grass are there referred to the year
1648—which must assuredly be a misreading or misprint for 1678.

180

“ce

LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

But many of the things we imagine, and the natural
objects that we inquire into, are very insignificant ; and
especially so, when we see those little living animals
whose paws we can distinguish, and estimate that they
are more than ten thousand times thinner than a hair of
our beard; but I see, besides these, other living animal-
cules which are yet more than a hundred times less, and
on which I can make out no paws, though from their
structure and the motion of their body I am persuaded
that they too are furnished with paws withal: and if
their paws be proportioned to their body, like those of the
bigger creatures, upon which I can see the paws, then,
taking their measure at but a hundred times less, it
follows that a million of their paws together make up but
the thickness of a hair of my beard; while these paws,
besides their organs for motion, must also be furnished
with vessels whereby nourishment must pass through
them.

Because many people, both in the towns and in the
open country, are stricken with fever,’ and because their
shoes get very red whenever they walk through the grass
in the meadows; the common man concludes that the air
is therefore infected, and very fiery. This coming to my
ears, I betook myself without the town and examined the
dew: but I could find nought in it worthy of remark.
However, seeing that my shoes also had got reddened by
the grass, I turned my attention to the grass itself, and
saw that some of it was studded with reddish dots.
Bringing these before my microscope, 1 saw that they
consisted of small globules, whereof upwards of a thousand
did not equal the bigness of a small sand-grain. (I find
there are various kinds of grass: and among others, one
sort that was very rough, which was not contaminated °*.)
Inquiring after a reason for these globules being upon the

’ Probably a reference to malaria, and therefore of some interest at the

present time.

> Marginal note in original.

LETTER 26. 27 SEPTEMBER 1678 181

grass, I observed that they came not out of the air (as
was the vulgar opinion), but out of the grass itself: the
cause whereof I conceived to be this. The dry cold, that
we had some three weeks earlier, caused the death of the
extreme tips of some blades of grass; and this was followed
by very warm weather, which drove fresh nourishment
again upwards through the pores’ in the grass. But this
food-matter, wherewith the pores of the grass were filled,
being unable to get out at the top (because the ends or
the uppermost pores of the grass were stiff and dried up),
burst open the pores in many places where they were
most weakened ; and thus many globules were squeezed
out of them. These globules, lying stuck together upon
the outside of the grass, and becoming stiffer on exposure
to the surrounding air, took upon themselves a reddish
colour; whereas these same globules, when they le in-
closed in the pores, are green.” And whenever one
happens to strike one’s foot against such grass, the said
globules are dusted off it, and make one’s shoes reddish.
But since a red colour is most agreeable with the notion
of fire, we must not take it amiss in the common man if
he deems the said substance to be a fiery matter: seeing
that there are among us physicians (who fancy themselves
experienced) who say, when they see blood whose whey-
like matter * is yellow, that the blood is bilious; or say of
black blood, that ’tis burnt: just as if everything yellow
were bile; and everything black, burnt.’

Meantime the Fellows of the Royal Society’ had not been
wholly idle in the matter of the “little animals.” Robert

* Port MS.

> L. evidently confused the red corpuscles on the grass-blades with
chloroplasts within them.

* i.e, serum.

* It is clear from this, and many another passage in L.’s writings, that
he had but a poor opinion of the general medical practitioner of his day.

*> The Fellows (or some of them) would perhaps have taken particular
interest in the observations on infusions: for they would recall—unlike

“ec

182 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”

Hooke, who succeeded Oldenburg in 1677 as Secretary,
himself repeated the experiments with pepper-water and other
infusions. In 1678 he published’ some account of his obser-
vations, which confirmed Leeuwenhoek’s findings: and his
experiments were also briefly communicated to Leeuwenhoek
by letter at the end of 1677. Hooke’s published description
records that he succeeded in seeing the animalcules—-or some
like them—described by Leeuwenhoek: “some of these,” he
says, “so exceeding small, that millions of millions might be
contained in one drop of water.”* A draft of Hooke’s unpub-
lished letter is still in possession of the Royal Society; and as
it contains several points of interest J will now give it. He
wrote °:

The papers you directed to the Lord Brouncker* were
read at a full meeting of the Royall Society and very
kindly accepted by the Members thereof and they have
orderd me to returne you both their thanks for soe freely
communicating your observations, and also an account
of what hath been here done in order to verify your
observation concerning the small animalls you have first
discovered in Pepper-water.

Having steeped then in Raine water pepper wheat

most modern Fellows—that Bacon, whose writings had so profound an
influence upon the Society at its inception, had emphasized the need of
inquiry into the various substances which produce animalcules by putre-
faction. Cf. Nov. Org., Lib. II, cap.50: “Etiam materiae diversae putre-
factionum, unde animalcula generantur, notandae sunt.”

* See Lectures and Collections made by Robert Hooke (1678). Part II,
Microscopium. Also reprinted in Lectiones Cutlerianae (1679).

* Ibid., p.83. Hooke evidently refers to bacteria—not protozoa.

* MS. letter (unpublished)—R. Hooke to Leeuwenhoek, Dec. 1 [?— date
partly obliterated], 1677. Roy.Soc.MSS. The original is in English, and
I give it exactly as written—only omitting a part at the end which has no
bearing upon the subject under consideration. I have merely expanded
words which are contracted in the original—for the reader's convenience,
and for typographical reasons. The letter is in Hooke’s own hand, and is
signed “ your very great admirer and honorer R.H.”

* William, second Viscount Brouncker (1620 ?—1684)—an Irish peer.
He was M.D. (Oxford) and a mathematician, and an original Fellow and
first President of the Royal Society on its re-foundation in 1662-3.

HOOKE’S CONFIRMATIONS 183

barly oats pease and several other graines,' and having
fitted up some microscopes which had layne a long
while neglected, I having been by other urgent occupa-
tions diverted from making further inquirys with that
Instrument, I began to examine all those severall Liquors
and though I could discover divers very small creatures
swimming up and down in every one of those steepings
and even in Raine it self and that they had various
shapes & differing motions, yet I found none soe ex-
ceedingly filled and stuffed as it were with them as was
the water in which some cornes of pepper had been
steeped. Of this the President & all the members
present were satisfyed & it seems very wonderfull that
there should be such an infinite number of animalls in
soe imperceptible a quantity of matter. That these
animalls should be soe perfectly shaped & indeed with
such curious organs of motion as to be able to move
nimbly, to turne, stay, accelerate & retard their progresse
at pleasure. and it was not less surprising to find that
these were gygantick monsters in comparison of a lesser
sort which almost filled the water.

It seems clear that the ‘“gygantick monsters’’ were
protozoa, while those of the “lesser sort” were bacteria. The
foregoing lines contain, I believe, the first mention of the
discovery of any of these organisms in infusions of wheat,
barley, oats, and peas: for none of these are recorded by
Leeuwenhoek as having been used in making the “ steepings 4
employed in his own experiments. It is therefore unfortunate
that Hooke—so far as I can ascertain—never wrote any
further descriptions of the organisms which he discovered.

Rumours of these remarkable discoveries spread, it would
appear, into even the highest circles : for in another letter from
Hooke to Leeuwenhoek, written a little later, the following
passage occurs *:

1 At a slightly later date—at a meeting of the Society on 7 March
1678—Hooke also demonstrated the presence of “ animalcules ” in infusions
of aniseeds and coffee. See Birch, Vol. TEE paso.

2 MS. letter (unpublished), R. Hooke to Leeuwenhoek, dated 18 April

184 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS”’

The prospect of those small animalls have given great
satisfaction to all Persons that have viewed them. His
majesty * having been acquainted with it, was desirous to
see them and very well pleasd with the Observation and
mentiond your Name at the same time. I know not
whether any of the ways I have here made use of for the
Discovery of them may be in any thing like those with
which you make your observations. But I have two or 3
other ways which I shall shortly communicate,’ that doe
farr exceed those I have here mentiond.’

Some important additional particulars regarding Hooke’s
observations can be gathered from Birch’s History. He tells
us* that at the meeting of the Society held on 1 November
1677 O58),

There were produced a great many exceedingly small and
thin pipes of glass of various sizes, some ten times as big
as the hair of aman’s head; others ten times less. These
were made, in order to try a conjecture of Mr. Hooke
propounded to the Society, that the discoveries, affirmed
to be made by Mr. Leewenhoeck, were made by help of

1678 (Roy. Soc. MSS.). The original, of which only a part is here copied,
is in English. It is written in Hooke’s hand and signed “R.H.”’ I again
expand the abbreviations in the original, for the reader's convenience.

1 j.e., King Charles II of England, “ Founder” and Patron (Fundator et
Patronus) of the Royal Society—as he is styled in the Charta secunda of
1663.

2 The communication will be found in Hooke’s Lect. & Collect. (1678),
p. 89 et seqq.

* This letter from Hooke is referred to by L. at the end of his own
Letter 28, 25 April 1679, to N. Grew (Brieven I, p.13: first published in
Dutch in 1686). As the 28th Letter deals largely with spermatozoa, it has
often been erroneously inferred that Hooke demonstrated spermatozoa—not
protozoa—to the King. But the correspondence between Hooke and L.
affords no grounds for such an inference; and I have been unable to
discover any evidence in support of the accepted belief that the Merry
Monarch was once entertained at an exhibition of spermatozoa by the
Royal Society (or any member thereof). This myth probably originated
with Haller (Elementa [1765], VII, 523)—as Cole (1930, p. 14) has already
noted.

* Birch, Vol. III, p. 346.

WITNESS OF ROYALTY AND THE ROYAL SOCIETY 185

viewing with a good microscope such small pipes contain-
ing the liquor or water, in which those multitudes of
exceedingly small insects or animals wriggling among
each other are discovered; for that he alledged, that the
said pipes being filled with liquors became themselves as
it were magnifying glasses. . . . . . It was therefore
ordered, that against the next meeting pepper-water should
be provided, and some better microscope than that made
use of, that the truth of Mr. Leewenhoeck’s assertions
might, if possible, be experimentally examined.

Accordingly, at the next meeting, on 8 November 1677,
“the first thing exhibited was the experiment charged on
Mr. Hooke at the last meeting, of examining pepper-water with
better microscopes and thinner and small pipes.”* But the
experiment was not wholly satisfactory, and various objections
to the observations were raised by the Fellows present. At
the following meeting, however, on November 15, ample
confirmation was forthcoming. In the words of Birch :*

The first experiment there exhibited was the pepper-
water, which had been made with rain-water and a small
quantity of common black pepper put whole into it about
nine or ten days before. In this Mr. Hooke had all the
week discovered great numbers of exceedingly small
animals swimming to and fro. They appeared of the
bigness of a mite through a glass, that magnified about
an hundred thousand. times in bulk; and consequently it
was judged, that they were near an hundred thousand
times less than a mite. Their shape was to appearance
like a very small clear bubble of an oval or egg form;
and the biggest end of this egg-lke bubble moved fore-
most. They were observed to have all manner of motions
to and fro in the water; and by all, who saw them, they
were verily believed to be animals; and that there could
be no fallacy in the appearance. ‘They were seen by Mr.

' Birch, Vol. III, p. 349.
* Bireh, Vol: IL, p: 352.

186 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS”

Henshaw, Sir Christopher Wren,’ Sir John Hoskyns,°
Sir Jonas Moore,‘ Dr. Mapletoft,? Mr. Hill,® Dr. Croune,"
Dr. Grew,* Mr. Aubrey,’ and divers others; so that there
was no longer any doubt of Mr. Leewenhoeck’s discovery.

Leeuwenhoek’s next communication on the “ animalcules’’
in infusions was sent to Robert Hooke, and is very brief; but
it was accompanied by a copy of a very curious and interesting
letter which he had previously written to Constantijn
Huygens. In the letter to Hooke he says:

As I see and hear that you are a man much given to
speculation, I have thought fit to send you a copy of a
very rough calculation which I set down on paper at
the urgent intreaty of Mr. Constantijn Huygens van

1 Thomas Henshaw (1618-1700), barrister and author: Vice-President
and an original Fellow of the Society. Cf. Dict. Nat. Biogr.

* Christopher Wren (1632-1723), artist and famous architect—soon to be
President of the Society (1680)—too famous to need further annotation.

* John Hoskyns (1634-1705), barrister of the Middle Temple: later
Secretary and President of the Society. Cf. Dict. Nat. Biogr.

* Jonas Moore (1617-1679), mathematician and surveyor. Elected F.RB.S.
in 1674. He is several times mentioned by Pepys in his Diary, and his life
is given in the Dict. Nat. Biogr.

* John Mapletoft (1631-1721), M.D. and D.D., of Trinity College,
Cambridge. Elected F.R.S. in 1676. He was an intimate friend of John
Locke, and before he became a divine practised medicine in London with
Sydenham.

* Abraham Hill (1635-1721), Treasurer of the Society, and an original
Fellow. Commissioner of Trade in 1689—a business-man of no known
scientific attainments.

” See p. 48, note 2, supra.

* See p. 168, note 4, supra.

* John Aubrey [sew Awbrey] (1626-1697), the well-known antiquary ; an
original Fellow of the Society.

* From Letter 29a. 16 January 1680. MS.Roy.Soc. An English extract
from this letter—and its enclosure—was published in Derham’s Philos.
Expts. & Obss. of R. Hooke (1726), p. 55. (The letter is there incorrectly
dated Jan. 6.) I translate from the Dutch original—A contemporary
English MS. translation is preserved with the original Dutch MS. in the
Roy. Soc. collection, but it has given me no help. The letter was read at
the meeting of the Society on 22 Jan. 1680 [0.S.], and discussed at the
following meeting on Jan. 29. See Birch, Vol. IV, p. 5.

LETTERS TO HOOKE AND CONST. HUYGENS 187

Zuylichem.* And I feel bound to say, furthermore, that
last Friday evening I took some pepper-water, in which
there were many living animalcules, and mixed it with
about a like amount of rain-water, wherein I had put a
quantity of pounded ginger: and forthwith examining
this mixt water, I found that the animalcules were slow
a-moving. Some hours afterwards, examining this water
anew, I could perceive no animalcules whatsoever in it :
but about twice 24 hours afterwards, I saw very distinctly
some animalcules which I judged to be a hundred million
times smaller than a sand-grain, but without being able
to discern any of those animalcules that had been before
in the pepper-water.”

The enclosed letter to Constantijn Huygens, dated 20 May
1679, I shall now give in full. The original, from which it
was copied, is preserved among the Huygens manuscripts at
Leyden *—the following being a complete translation of the
copy sent to Hooke:

Along with this goeth my calculation, which I confess
is quite imperfect, seeing that my estimates were made
by the eye alone.

I have oft-times let my thoughts run on the extreme
small vessels and sinews* wherewith the very little

* The father of Christiaan Huygens the astronomer and mathematician—
not his elder brother. Cf. p. 42, note 2, supra.

* It is probable that the animalcules in the pepper-water were protozoa
of some sort, which were killed when the ginger-water was poured upon
them: while the very minute forms which developed in the mixture after
48 hours were evidently a new crop of bacteria.

* See Haaxman (1875), p. 136,—where the date is given as 21 May
1679: but L.’s copy, sent to Hooke, is by himself dated May 20, as stated
above. The copy was made with his own hand.—The original has recently
been printed in full in Guvr. Compl. de Chr. Huygens, VIII, 168-172 (also
there dated May 21).

* Or “nerves”: MS. senwwen. Zenww nowadays means a nerve—as it
often did to L.—but at an early date it also meant a sinew (tendon), and
from what follows this seems to be the correct rendering here. (Cf. the
original meaning of Lat. nervus and Gr. vedpov.)

188

ce

LEEUWENHOEK AND HIS LITTLE ANIMALS ”’

animalcules are furnished withal; and more especially
when I have been asked, whether I am able to see the
particles of water itself? T’o which I did often answer,
that there be little animals in water that are many
million times smaller than a sand-grain; and that these
little animals, on which I can discern no feet, must not-
withstanding be furnished with instruments for motion ;
and that these instruments must themselves consist, in
part, of blood-vessels which convey nourishment into
them, and of sinews which move them; and that through
these vessels, moreover, water must also pass. And this
being so, we must suppose the particles of the water itself
to be so small as to be, for us, inconceivable: and I’m
persuaded that no man will ever advance so far in science
as to be able to gaze upon the particles whereof water
itself consisteth.

I shall here first lay down the proportion which the ©
animalcules bear to a sand-grain, in so far as my eye is
able to arrive at it; together with the number of
animalcules proportionate to the bigness of a cubic
inch.

I usually judge that three or four hundred of the
smallest animalcules, laid out one against another,
would reach to the length of the axis of a common grain
of sand; and taking only the least number (to wit 300),
then

27000000 animalcules together are
as big as a sand-grain.

Let’s assume that such a sand-grain is so big, that
80 of them, lying one against the other, would make up
the length of one inch as BC [Text-fig. 1].

LETTER TO CONST. HUYGENS. 20 may 1679 189

80 sand-grains in the length of one
80 inch.

6400 sand-grains in a square inch.
80

p 512000 sand-grains in a cubic inch.
27000000 animalcules which make
3 up the bigness of a
(Text-Fic. 1.] sand-grain.
amounting to 1382400000000 animalcules in a cube
inch, as ABCDEF.

This number of animalcules is so great, that if one had
as many sand-grains, of the bigness aforesaid, then one
could lade with them more than 108 of our ordinary sand-
lighters; that is, reckoning one schagt of sand (which is
144 cubic feet) to every lighter.

I have let my thoughts run likewise on the very
little vessels that are in our bodies, and have judged that
they are above a thousand times thinner than a hair of
one’s head; and I have therefore put the proportion of
the very little vessels thus in relation to the body, in
order to arrive afterwards at the proportion of the
vessels in the little animals.

First of all, I sought to know how many hairbreadths
are equal to the length of one inch; and having by me a
copper rule, whereon the inches are divided into 3 parts,
and each of these again into 10 parts (thus altogether, an
inch divided into 30 parts), I laid hairs from my periwig
upon these divisions; and observing them thus through
a microscope, I judged that 20 hairbreadths are equal to
3a of an inch. Consequently, there are 600 hairbreadths
in the length of one inch.

Further, I measured, roughly, the thickness of my
body above the hips, and judged (taking one thing with
another) that the diameter of my body was 8 inches.’

‘ If this were approximately correct, then L. was considerably more

190 LEEUWENHOEK AND HIs ‘“‘ LITTLE ANIMALS ”’

Archimedes showeth that as 14 is to 11, so is the square
of the diameter to the content of a circle.’

14—11—8
8 704
64 14 507 square inches for my body’s thick-
11 ness.
704

600 _hairbreadths in a length of one inch.
33 diameters of the very little vessels in
our bodies for one hairbreadth (that
is, reckoning the little vessels in our
bodies 1089 times thinner than a

hair)

gives 19800 little vessels in a length of one inch.
19800

gives 392040000 little vessels to a square inch.
50 square inches for the body’s thickness

gives 19602000000 vessels in the thickness of the body.

If we now suppose that the little vessels bear the same
proportion to the bodies of the little animals, as those in
us do to our bodies; then, in order to compare the very
little vessels of the animalcules with the thickness of a
sand-grain, the number given above must still be multi-
plied by 300 (since, as already said, a sand-grain is 300
times thicker than an animalcule).

——$————

slender than the apparently heavily-built man depicted in his portraits.
Moreover, the statement is not easy to reconcile with the later record that
at this date he weighed over 11 stone (ef. p. 222 infra).

* Nowadays we usually find the area of a circle by 77°; but “/y X d’ is
obviously the same thing, and Prof. D’Arcy Thompson informs me that it is
actually in this form that the proposition is found in the Circuli Dimensio of
Archimedes.—It is highly improbable, of course, that L. had ever studied
the writings of this great mathematician.

SOME ‘‘ CURIOUS MATHEMATICKS ”’ 191

Consequently, if the thickness of 19602000000

ar pe 300
a sand-grain is 1, the vessels in cae A eee
the little animalcules are 5880600000000

And because this number is so exceeding great, I have
thought good to express the proportion in terms of a
hair’s breadth in relation to the circumference of the
earth.

5400 miles’ for the length of the circumference
2000 rods for every mile

gives 10800000 rods for the circumference
12 feet for one rod

g1ves 129600000 feet for the circumference
12 inches in one foot

gives 1555200000 inches in the circumference
600 hairbreadths in one inch

gives 933120000000 hairbreadths for the length of the

circumference.

This number of hairbreadths, which is equal to the
length of the circumference of the earth, even when again
multiplied by 6 will not equal that number aforesaid
which represents the proportion of the vessels in the little
animals to the thickness of a sand-grain (as we have
estimated it above). To sum up, then:

As a sixth of a hair-breadth is:

To a length of 5400 miles:

So is one of the smallest vessels in the smallest
animalcules :

To the thickness of a sand-grain (of such size that
80 thereof, lying one against another, equal a
length of one inch).

Sir, you have here the wonderful proportions that I

‘ Leeuwenhoek’s ‘‘ mile’’, consisting of 2000 “rods” of 12 feet, is, as a
simple calculation shows, equal to some 4% English miles. (The English
mile = 320 rods, and the English rod = 162 feet.)

cc

192 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”’
conceive to exist in the secret parts of Nature: and from
this appeareth also, that all we have yet discovered is but
a trifle, in comparison of what still lies hid in the great
treasury of Nature; and how small must be those particles
of water’ which, to all appearance, pass many at a time
through such tiny vessels.

I hope that with this I have satisfied your require-
ments.”

I have given the foregoing letter in full for several reasons.
In the first place, it serves to illustrate Leeuwenhoek’s fond-
ness for simple mathematical deductions ; secondly, it shows
very clearly that, in the case of his “smallest animalcules”’, he
was dealing with bacteria; and thirdly, it shows the success
and failure of the application of his “uniformitarian” principles
to microscopic creatures. In his estimate of the size and
numbers of the bacteria present in a minute drop of water, he
was not mistaken: but when he proceeded to show, by simple
arithmetic, the magnitude of the blood-vessels in such
organisms, he went ludicrously astray. His education and
his century both failed him. His greatness and his littleness
are here revealed simultaneously—to those endowed with the
accumulated knowledge of the next 250 years. Yet even at
the present day Leeuwenhoek’s mistaken conclusion may
serve as a warning to the biologist with statistical tendencies.
It is surely worthy of remembrance, even now, that the most
flawless mathematical calculations may sometimes be wholly
erroneous.

Leeuwenhoek’s next observations on ‘‘animalcules” are
contained in a further letter to Robert Hooke. After
recording some observations of no* present interest, the letter
ends thus: *

a

" j.e., the molecules of which water itself is composed.

> Referring to Const. Huygens’s request that he should put down on
paper his calculations concerning the magnitude of the parts of the “little
animals”’ (vide supra).

° A few words which are perhaps not irrelevant to the present subject
will be referred to later (see p. 207 infra).

* Letter 30. 5 April 1680. To R. Hooke. MS.Roy.Soc. Published in
Brieven, Vol. I (Dutch), and Opera Omnia, Vol.I (Latin): also an English
abstract in Phil. Trans. (1693), Vol. XVII, No. 196, p. 593; but this does
not include the passage here quoted.

LETTER 30. 5 APRIL 1680 193

In the court-yard of my house there stand two vines;
and observing their growth to be such, that a moisture
dripped from their shoots, I examined this sap on several
successive occasions, just to see if I could discover any
living creatures in it: and most times I discerned therein
divers kinds of living animalcules, whereof one sort was
uncommon big in comparison of the others; nay, I even
saw some little animals that I had seen aforetime in
divers sorts of water. Hereupon I repaired to my
garden which lieth within this town, and there too I
examined the sap dripping from the vines, but in it I could
discover no living creatures, save only a little worm that
was of an uncommon bigness,’ compared with the other
animalcules. I betook myself thence to my garden which
lieth without the town, and there again examined the sap
from several vines, but could discover no living animalcules
in it. I cut off pieces from two vine-branches, to make
them drip the more, and went to examine the sap again
next day, but could find therein nothing living. And
I took a new glass phial, and caught the sap in it, and
carried it home and examined it; but notwithstanding,
I could perceive no living animalcules in it. I am
now busy finding out, if ’tis possible, why there be living
animalcules in one sap, but none in the other.

A little later Leeuwenhoek addressed another letter on
the same subject to Dr Gale,” and in it recorded the results
of his further experiments and observations on the sap of vines.
This letter is as follows: °

* Probably a nematode.

* Thomas Gale (1635 ?—1702), a Doctor of Divinity, was at this time
Secretary of the Royal Society—an office to which he was appointed in
November, 1679. He was a Fellow of Trinity College, Cambridge, and
Professor of Greek in the University from 1662 to 1672. Later (1697) he
became Dean of York.—At the beginning of this letter L. says that he is
writing to Gale because Hooke had informed him that Gale was become
Foreign Secretary, and that he should therefore address his letters to him
in future.

° Letter 81. 13 May 1680. To Thomas Gale. MS.Roy.Soc. Printed
1Ue5;

194 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS ”’

This serves as a continuation of my letter of the 5th of
April [1680], wherein I noted how I had observed living
animalcules* in the sap leaking from the shoots of the
vine standing in my court-yard; whereas in the sap
which dripped from the vines in my garden, I could
discover no living creature. I have divers times turned
my thoughts to this matter, and can find no more
satisfactory explanation thereof than the following :

The rain-water, which is drawn aloft by the power of
the sun, and forms the clouds, is commingled with the
seed of these animalcules; and as it had been raining for
several days running, before the date of my first observa-
tions on vine-sap, the tags of leather, wherewith the
branches of the vine were nailed fast against a stone
wall, had become quite water-logged; but afterwards there
followed a warm sunshine, which caused the vine-branches
to drip, and thus the foresaid leathern tags were kept
continually wet, by the dripping of the vine upon them;
and in this manner not only did divers sorts of animals
come forth from this rain-water, but they even (so I
imagine) bred in it, and swam along the vine-branches,
even to the topmost part of the vine, where the moisture
dropped out.

About 24 hours after I had dispatched my observations
to Mr. Hooke, the vine-branches in my court-yard
stopped dripping, and the weather grew uncommon warm,
so that the vine-branches, and the leathers as well, got
quite dry: hereafter, it rained near the whole night, then
the sun shone in the morning, and it rained afresh in the
afternoon: and observing that the leathern tags (with
which, as remarked above, the branches of the vine were
nailed fast to the wall) were once more soaked through, I

in Brieven, Vol. I (Dutch), Opera Omnia, Vol. I (Latin), and briefly abstracted

in English in Phil. Trans. (1693), Vol. XVII, No. 196, pp. 593-4,—along

with the preceding letter. It was presented at a meeting of the Society on

« 13 May 1680 [0.S.] (Birch, Vol. IV, p. 37). I translate the whole letter,
with the exception of a few words at the beginning and the end.

1 The MS. says Dierkens, but the printed letter has Dieren (=animals).

LETTER 31. 138 may 1680 195

examined the water that lay upon them, and in it I
discovered! sundry little animals of the biggest sort
previously seen in the sap aforesaid, and I saw some of
a lesser sort lying dead: and when I examined these
animalcules more narrowly, I found that they belonged to
two kinds commonly present in ordinary waters.’ After
this time, about the middle of April, it rained a whole day,
and the night following ; and next morning, when the
sun came out, I betook myself to my garden, and
[examined]* the sap dripping froma vine-branch, which
I had cut a few days before, in order to make it drip, at
the same time tying or binding a strip of wash-leather
around it, so that when it rained, the rain-water would
stay caught in it, and not readily dry up, and thus get
better mixed with the sap that dripped out: and in this
water I discovered a few animalcules of the sort already
described. I also examined the sap from a second vine,
which I had likewise treated in the same way, and herein
too I perceived the animalcules. I also visited a third
vine, from which I had also previously cut off a branch,
so that it would drip;* but this one I did not tie round
with a leather, and I took the sap that ran down the
branch at the place where it was most plentiful (namely,
in a fork, where the shoot came off the stem); but I

Aw «mA
(Text-Fic. 2.]
could perceive no living animalcules in it, though I saw in
it, with admiration, many little chrysalises, or pupae, as
in Fig. A A [see Text-fig. 2]: and although they were

' gesien MS. ontdekt printed version.

2 It is obviously impossible to identify these “animalcules”, though
they were probably protozoa or bacteria of some sort.

> A verb is here accidentally omitted from the MS. and also from the
Dutch printed version. The sense evidently requires “examined” or
“ observed’: and as the Latin translator supplied “ examinavi # do
likewise. .

4 These words (op dat die druipen soude) are in the printed version but not
in the MS.

196 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

more than a million times smaller than a coarse sand-
grain, yet could I see very plainly that they were furnished
with 5 joints. This appeared very strange to me, as I
had formerly convinced myself that no water-animalcules
proceed from such structures, and I had never conceived
that animalcules of such littleness could live in the air.
I took these chrysalises home, and put some of them in the
air, to see what would come out of them; but within a
few days, they got so dry that their former figure was
scarce discernible ; and those which I meant to keep in
water got lost.

These trifles are all I have to tell you for the time
being.’

The foregoing characteristic observations upon protozoa
(or bacteria) show us an interesting picture of Leeuwenhoek
at work—discovering new ‘‘animalcules” in new situations,
wondering how they make their appearance and multiply in
certain liquids, and endeavouring to account for their appar-
ently erratic distribution. Soon afterwards he again attacked
the problem of their generation, and sent the following account
of his experiments : *

When it became known to me that divers opinions
have been expressed concerning the generation of little
animals; and as I heard, especially, that a certain
Gentleman’ hath writ that no living creature can be
generated if the vessel, or bottle, in which any moisture
or meat has been put, be tightly stoppered ; I had a mind
to carry out some trials of this matter.

* This sentence is in the MS. but not in the printed version.

* From Letter 32. 14 June 1680. To Thomas Gale. MS.Roy.Soc.
Printed in Brieven, Vol. I (Dutch) and Opera Omnia, Vol. II (Latin). No
abstract of this letter was published in the Phil. Trans. though the letter is
a very remarkable one. It contains, in addition to the observations here
related, a description of yeasts obtained from beer—the first microscopic
study of these organisms.

* Doubtless Francesco Redi, whose celebrated treatise on “‘ the Genera-
tion of Insects”’ first appeared in 1668. LL. could know of Redi’s work only
by hearsay, since he was ignorant of Italian.

eva Lan)

ie ne; mint i
aes mies:
hin a Nhat:
il “ul ih ‘ae
uy Ms wt

me LAr Ay

a rat aoe

bes re hah Naa haa

I Se
wn Ce ~ Nhneaia Mea wor aN nel ;
ee Y aw Te), ;
Aah, ‘eo iat ait) Nae ee se a

Wh en hay yi Ha) od a py

hi Se ey yi ia, ay es Wi, wine ia, ne
oe mete, Slots oh

we Ae , :

PLATE XXII

Ss

pr

yp

ANNAN ass A

A FIGURE FROM LETTER 32 (14 JUNE 1680)

illustrating the experiment with the pepper-
tube. On the left, Leeuwenhoek’s original
drawing (reduced to #): on the right, the same
figure as improved by the engraver for re-
production in the printed letter (same size).

facing p. 197

LETTER 82. 14 JuNE 1680 197

Accordingly, I took two glass tubes, as ABCDEFHIKL
[Plate XXIT], which, after they were both closed below at
AL, were filled up to BK with pounded pepper, and then
to CI with clean rain-water, as soon as it had been
collected on May 26* in a clean china dish (in which no
victuals had been put for quite ten years); then, by the
heat of the flame, the glass was fashioned to the figure of
ABCDGHIKL, having at its pointed end G a small
opening ; for I considered that though the glass was now
hot, the air within it would presently become equally cold
with the air that was outside it; and after the lapse of
about a quarter of an hour, I sealed up the aperture at G
tight, by means of the flame. I also prepared myself a
second glass, treating it likewise, save that in this I left
the aperture at G open; in order to ascertain, if ’twere
possible, in which water the living animalcules would first
turn up. But after it had stood thus for three days,
during which time I made divers observations upon it, I
judged that if there were already any very little living
animalcules in this water, ’twould not be possible for me
to discover them, for the reason that the glass was too
thick, and because of the many little particles of pepper
which lay against the glass inside, so that it was not
feasible to carry out such particular observations as the
occasion required. On this account, I took a little water
out of the second glass, through the small opening at G;
and I discovered in it a great many very little animalcules,
of divers sorts and moving about among one another,
each several sort having its own particular motion. But
as the first tube was of a somewhat thinner glass, I left it
shut up till the fifth day, and during that time made
various observations upon it; but I could discover no
living animalcules in it, so I resolved to break the glass
open at G, and in breaking it, the air which had thus
been shut up for 5 days within it (and which was much

" Anno 1680.

198 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

compressed by the air-bubbles which rose everywhere to
the top of the water) escaped with force out of the tube:
for which reason I rather fancied that there would be no
living creatures in this water. But I found the contrary:
for no sooner did I draw some water through the small
opening I had made at G, and bring it before my micro-
scope, than I perceived in it a kind of living animalcules
that were round, and bigger than the biggest sort that I
have said were in the other water, though they were yet
so small that it was not possible for me to discern them
through the thickness of the glass tube.’ After this tube
had stood thus open for 24 hours, I examined the water
again ; and I then saw, besides the foresaid animalcules,
various other sorts, though they were so small that they
were hard to make out.

Still, I bethought me that when that Gentleman afore-
said spake of living creatures”, he meant only worms or
maggots, which you commonly see in rotten meat, and
which ordinarily proceed from the eggs of flies, and which
are so big that we have no need of a good* microscope to
descry * them.

The whole of the foregoing passage (as printed in Dutch)
has recently been copied and learnedly commented upon by
Prof. Beijerinck (1913), who himself repeated the experiments.
He infers that the “animalcules”? which Leeuwenhoek dis-
covered were undoubtedly bacteria—not protozoa—and that
among them were probably (as he found in his own experiments)
Bacillus coli, Azotobacter, and Amylobacter saccharobutyricum.
It was to this last species, he thinks, that the “ bigger sort ”’
which were found in the sealed tube probably belonged.
Beijerinck also points out that these are the earliest known
observations on any anaerobic bacteria: but although

' So in the printed version. The MS. has “ for reasons already men-
tioned ”’ (voor de verhaelde oorsaeken).

> dierkens MS. schepsels printed version.
* goet is in printed version, but not in MS.
* bekennen MS. beschowwen printed version.

ANAEROBIC BACTERIA DISCOVERED 199

Leeuwenhoek discovered that organisms could live and
multiply under the hemi-anaerobic conditions present in his
closed tube, he was unable at that time, of course, to realize
the full importance of his discovery. I have also confirmed
the foregoing observations, though I made no attempt to
determine exactly what species of bacteria were present in
the tubes—being satisfied with Prof. Beijerinck’s authoritative
opinion. Iam also satisfied that no protozoa can usually be
obtained in experiments such as the above if the procedure
described be adhered to.

It seems remarkable that Leeuwenhoek—always a vigorous
opponent of the doctrine of spontaneous generation—appears
to have made no further study of the very interesting pheno-
mena which the foregoing experiments record. He must
have been puzzled, at first, to account for the appearance of
bacteria in his sealed tube: but I think his own words supply
the explanation which occurred to him, and which apparently
satisfied him at that time. In previous letters’ he makes the
suggestion that ‘“‘ animalcules” or their “ seeds ”’ are present,
or can exist, in rain—being drawn up into the clouds with
the water in which they live or are formed, and subsequently
scattered when the rain falls. Consequently, he probably
imagined that the rain-water introduced into the sealed tube
already contained ‘“ animalcules” —or “seeds”? capable of
germinating into “animalcules”»—-which found sufficient
‘air’ in the tube to enable them to live and breathe and
multiply for at least some days. Nearly a hundred years
subsequently elapsed before any further light was shed on this
subject by the ingenious experiments of Spallanzani, though
it was not until much later that the problem was solved—
more or less completely—by Pasteur and Tyndall. Redi’s
famous observations by no means solved the problem of
spontaneous generation—as is often lightly stated: and this
point is clearly brought out by Leeuwenhoek’s experiment, as
he himself apparently realized; though he made no attempt—
or, at least, recorded none—to push his inquiries any further.

A few months after he had written the foregoing letter to
Dr Gale, Leeuwenhoek wrote again to Dr Hooke: and in

" Cf. Letter 18 (p. 163) and Letter 31 (p. 194).

a3

200 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

the course of his letter he gave some further details concerning
the animalcules in pepper-water. His words are as follows: *

Some days ago I once more poured water upon some
pounded pepper; and a few days later, I saw, among
others, two kinds of animalcules’ in it; and moreover,
there seemed to be big and little ones of either sort,’ so
that methought the big ones were full-grown, and the
little ones their young; and at the same time I imagined
that in the biggest sort of these animalcules I could see
the young, or maybe their eggs, inside their bodies. And
I imagined, besides, whenever I saw two little animals
entangled together, either swimming or lying still, that
they were a-copulating.

* Whereas I suffer many contradictions, and oft-times
hear it said that I do but tell fairy-tales about the little
animals, and that there are people in France who do not
scruple to say that those are not living creatures which I
exhibit, and that if such water be boiled, the particles
which one imagines to be animals still continue to move ;
yet notwithstanding, I have demonstrated the contrary

" From Letter 33. 12 November 1680. To R. Hooke. MS.Roy.Soc.
Printed in Brieven, Vol. I (Dutch), and Opera Omnia, Vol. II (Latin). An
incomplete English translation was published in Phil. Collect. of R. Hooke
(1681), No. 3, pp. 51-58. The whole letter was first published in Dutch in
1684 (Ondervindingen en Beschouwingen, etc. pp. 1-32): while the full Latin
version appeared in 1695 (Arc. Nat. Det.)—It should be noted that in the
earlier part of this letter—not here translated—L. casually mentions that
he “ saw some little animalecules swimming” (p. 8, Dutch printed version)
among various © globules’? which he found in rain-water that he had put in
a special piece of apparatus. They were probably protozoa or bacteria; but
as no further mention is made of them, they are not identifiable.

* Evidently ciliates.

° dat yder soorte groter en kleynder haar vertoonde printed version (1684)
dat ijder in sijn soort bestonden uijt groote en kleijne dierkens MS. (1680).

‘ Probably a misinterpretation of the inclusions in food-vacuoles.

° The lines following, as far as the calculations on p. 203, have been
translated by Hoole (1798) in his Introduction, pp.iv-vi. His rendering is
faithful in substance, though not always in diction. In translating L. he
allowed himself more latitude than I have done.

LETTER 33. 12 NOVEMBER 1680 201

to divers distinguished Gentlemen, and I make bold to say,
that people who say such things have not yet advanced so
far as to be able to carry out good observations.

For my own part, I can say with truth, that the smallest
sort of which I shall here speak, I see alive and exhibit as
plainly to my eye as one sees, with the naked eye, little
flies or gnats sporting in the air, though they may be
more than a hundred million times less than a coarse
grain of sand ; for not only do I observe their progression,
both when they hurry, and when they slow down, but
I see them turn about, and stand still, and in the end
even die; and those that are of a bigger sort,’ I can also
see running along as plain as you see mice before
your naked eye; nay, in some I can even see the inward
parts of their mouth, as they stick them in and out, and
make play with them; indeed, in one sort I see the very
hairs on their mouth, though they themselves are several
thousand times less than a sand-grain.

As they’ll say ’tis not credible that so great a many of
these little animalcules can be comprehended in the
compass of a sand-grain, as I have said, and that I can
make no calculation of this matter,” I have figured out
their proportions thus, in order to exhibit them yet more
clearly to the eye: Let me suppose, for example, that
I see a sand-grain but as big as the spherical body ABGC
[Text-fig. 3, p. 202] and that I see, besides, a little animal
as big as D, swimming, or running on the sand-grain; and
measuring it by my eye, I judge the axis of ° the little
animal D to be the twelfth part of the axis of the
supposed sand-grain, AG ; consequently, according to the

" From the descriptive details which follow, L. evidently refers here to

ciliates.

* The beginning of this sentence—up to the point here marked—is worded

differently in the MS. and in the printed version. The meaning is, however,
identical in the two.

* van (of) is here omitted from the printed version—by a misprint—but

is present in the MS.

202 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS”

ordinary rules, the volume of the sphere ABGC is 1728
times greater than the volume of D. Now suppose I see,
among the rest, a second sort of little animals, which

i

(Text-Fie. 3.]

I likewise measure by my eye (through a good glass, giving
a sharp image); and I judge its axis to be the fifth part,
though I shall here allow it to be but the fourth part (as
Fig. E), of the axis of the first animalcule D; and so,

MICROMETRIC METHODS 203

consequently, the volume of Fig. D is 64 times greater
than the volume of Fig. E. This last number, multiplied
by the first number [1728], comes then to 110592, the
number of the little animals like Fig. E which are as big
(supposing their bodies to be round) as the sphere ABGC.
But now I perceive a third sort of little animalcule, like
the point F, whereof I judge the axis to be only a tenth
part of that of the supposed animalcule E; wherefore
1000 animalcules such as F are as big as one animalcule
like E. This number, multiplied’ by the one foregoing
[110592], then makes more than 110 million little animals
[like F] as big as a sand-grain.

12 10 a 1728

12 10 + 64
144 100 16 6912

12 10 4 10368

288 1000 64 110592
144 1000
1728 110592000

Otherwise I reckon in this fashion’: Suppose the axis
of Fig. Fis 1, and that of Fig. EK is 10; then, since the
axis of Fig. D is 4 times as great as that of Fig. EH, the
axis of D is 40. But the axis of the big sphere ABGC is
12 times that of Fig. D; therefore the axis AG is equal
to 480. This number multiplied by itself, and the pro-
duct again multiplied by the same number, in order to
get the volume of ABGC, gives us the result, as before,
that more than 110 million living animalcules are as big
as a grain of sand:

1“ vermenigvuldig,’ in printed version, is a misprint. The MS. has,
correctly, vermenigvuldigt. ;

2 So in printed version. The MS. has merely Of anders (Or otherwise).

204 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

axis of Fig. F = 1
axis of Fig. H = 10
+
axis of Fig. D = 40
12
80
40
axis AG = 480
480

38400
1920

230400
480

18432000
921600

110592000

However, when I took somewhat coarser sand, as I did
when I drew up my estimate, I had to say that 20 axes
of the foresaid | biggest] animalcules did but make up one
axis of a sand-grain; and again, 5 axes of the lesser
animalcule equalled the axis of the first; and further,
10 axes of the smallest creature equalled one axis of the
second. In fine, then, according to this calculation, a
thousand million living animalcules are as big as a coarse
sand-grain (taken from fine scouring sand).

1 = axis F
10 = axis E
5
50 = axis D
20

1000 = axis AG
1000

1000000
1000

1000000000

LETTER 71. 7 MARCH 1692 205

In Leeuwenhoek’s next communications we find no further
mention of either protozoa or bacteria until we come to his
Letter 71, which, while recording various other observations,
contains the following words: '

I have by me the following notes, which I feel
constrained to add.

For several days past I have kept in a clean glass, in
my closet, some rain-water, gotten from a rain-cistern ;
in which water there was a little red worm,’ which I
divers times observed, by reason of its curious structure.

In this water, after a day or two, a multitude of little
living creatures did propagate themselves, they being of
two sorts which you commonly find in fresh or sweet
waters. The bigger sort I judged to be so small, that
thirty thousand of them together would scarce make up a
body as big as a coarse grain of sand.

On several different days I did look upon these little
animals,* and for so long, that not alone my eyes, but my
very hands, got a-weary ; and this was simply because I
did perceive such a plenty of these little animals, which
were coupled together, and so long remained in this pos-
ture: and I observed how the bigger sort dragged the
little ones along, or swam forward with them, with the
help of very plentevous feet, wherewith these animals are
furnished withal ; so that 1 was thus able on this occa-
sion to observe the copulation of these little animals
clearer than ever before. Nay, I saw them as plain as
you can see flying creatures* a-copulating before your
naked eye.

* Letter 71. 7 March 1692. To the Royal Society. MS.Roy.Soc.
Printed in Brieven, Derde Vervolg, p. 396 (the passage here translated
beginning on p. 423): Opera Omnia, Vol. II, p. 239 (1st pagination). A
partial English translation was also published in Phil. Trans. (1694),
Vol. XVIII, No. 218, pp. 194-199; but the passage here given in full is
there so abridged that it occupies only 84 lines (on p. 198).

> Rvidently a “ blood-worm’”’ (larva of Chironomus).

* The animals referred to are evidently ciliates.

* i.e. insects—not birds.

éé

206 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

These observations caused me to view more nicely the
lesser animalcules that were also swimming about in the
water, and whereof the number was a good twenty times
as many as that of the little animals aforesaid. Some of
these animalcules were also coupled; and I saw that
these likewise not only stayed long a-copulating, but also
that one of the pair, whether it swam through the water
or ran upon the glass, dragged the other one forward, or
trailed it after itself.

The foregoing passage is of great interest, since it is
evidently a record of observations made upon the conjugation
or fission of ciliates. In my opinion the evidence is in favour
of the view that Leeuwenhoek, on this occasion, witnessed
both these phenomena; though it is regrettable that he
gave so brief an account of what he saw. I cannot help
thinking that what he interpreted as “one animalcule
dragging another one along’ was a conjugating pair; whereas
‘one animalcule trailing another behind it”’ was really an
organism dividing transversely into two. Later,’ as we shall
soon see, he described the conjugation of ciliates in unmistak-
able terms.”

In a letter written some 3 years afterwards, Leeuwenhoek
mentions the discovery of “animalcules”’ in a new situation.
After describing his observations on the oyster, and its
generation, he remarks * :

I also paid attention to the ordinary water that is in
the shells of oysters; and I discovered therein a great lot
of little animalcules, which, in bigness and figure, were
like the little animalcules that you generally find in
canal-water, rainwater cisterns, and common ditch-water.
These animalcules were, in my judgement, above five
hundred times smaller than a young oyster.

' Cf. also the earlier observations in Letter 33, p. 200 supra.
> Letter 96, p. 213 infra.
* Letter 92. 15 August 1695. To Frederik Adriaan, Baron van Rhede.

Published in Brieven, Vijfde Vervolg, p.114: Opera Omnia, Vol. II, p. 511.
No MS., and not in Phil. Trans.

LETTERS 92 AND 96. 1695 207

No doubt these animalcules were protozoa: and it should
be mentioned that Leeuwenhoek had recorded a similar
observation at an even earlier date. Writing to the Royal
Society about fifteen years before, he mentioned’ that he had
found “ divers kinds of little living animalcules”’ in the juice
of mussels and oysters: but he gave no further account of
them, and it is impossible to ascertain what sort of organisms
these were. It should also be noted here, however, that in a
much later letter* he expressed the opinion that some of the
‘“animalcules”’ which he thought he saw formerly in the juice
of oysters were probably not really organisms at all, but
“particles”? set in motion by the cilia on the tissues of the
molluse.®

Leeuwenhoek’s last recorded observations on the “ animal-
cules” in infusions are contained in a letter written several
years later, and sent not to the Royal Society but to the
Elector Palatine. This very interesting letter runs as follows’:

In my letter of 18 September’ [1695] I ventured most

respectfully to describe how I opened a Freshwater
Mussel° and took out of it the unborn young mussels,’

* Letter 30. 5 April 1680. To Robert Hooke. MS.Roy.Soc. Published
in Brieven, Vol. I, p.33 (1st pagination): Opera Omnia, Vol. I, p. 25 (2nd
pagination): English abstract in Phil. Trans. (1693), Vol. XVII, No. 196,
p. 593.

* Letter dated 10 June 1712. To the Royal Society. MS.Roy.Soc.
English version printed in Phil. Trans. (1712), Vol. XXVII, No. 336, p. 529.
Not published elsewhere, and not numbered by L. himself.

* It seems to me probable that L. was here referring to the observations
contained in Letter 30, and not to those in Letter 92, which appears to record
a genuine observation of protozoa.

* Letter 96. 9 November 1695. To the Elector Palatine. Published
in Brieven, Vijfde Vervolg, p. 156: Opera Omnia, Vol. II (Contin. Arc. Nat.),
p.30 (2nd pagination). Not translated by Hoole. No MS., and not in
Phil. Trans. I translate the whole letter, with the exception of a few
immaterial words at the beginning and end.

° Letter 95, printed immediately before the present letter in L.’s published
works.

* Veen-Mossel (literally ‘‘ fen-mussel’’) — Anodonta: not easily recog-
nizable in the Latin version, where it is called “ concham ex genere earum
quae ex fossis capiuntur.”’ Veen means not only a fen, marsh, or bog, but
also the peat which can be dug out of such places: and consequently Hoole
(Vol. I, p. 85 sq.) translates veen-mossel as ‘ peat-muscle.’”’ But Anodon was
never known by this name in England—so far as I am aware.

" i.e., the “ Glochidia ’”’ larvae—described and figured in Letter 95.

208

cc

LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

which had developed so far that I judged them to be com-
pletely formed, because their shells seemed to be perfect.

I took several thousand of these unborn mussels, and
put them in a glazed white earthenware basin, and forth-
with poured canal-water upon them, in order to see
whether any of these unborn mussels would remain alive
and grow bigger.

Having put these little unborn mussels in the water,
I viewed them on several successive days, yet I could
make out no change in their size. But since, owing to
the rain which had fallen plentifully, our canals were
filled at that time with no other water than what runs
off the land, and which must then flow through our Town,
I saw, beyond my expectations, a great many very little
living animalcules, of divers sorts and sizes, in this water,
a-swimming among the unborn mussels. Amongst others
I saw some little worms,’ having a figure very much like
those worms that children void in their stools,” but whose
thickness I judged to be a quarter of that of a hair off
one’s head.

Furthermore, I saw some animalcules stuck fast to
one another by their long tails*; and these animalcules,
as well as sundry other sorts, I had never seen before, and
their motion was uncommon pleasant to behold.

Further, I saw that these animalcules did increase in
numbers from day to day.

At first, after four or five days, I replenished the water,
wherein these unborn mussels Jay, in such a fashion
that I poured off all but about a spoonful* of it, and then
presently added more canal-water again thereto.

1

Probably free-living nematodes.

* Probably meaning the nematode Oxyuris (=Enterobius) vermicularis.

3

Evidently a colonial Vorticellid (Carchesiwm ?). The “ animaleule with

a tail” is L.’s name for Vorticella, already described in Letter 18 (p. 118).
Further observations on the colonial forms are recorded later in the present
letter. (See also p. 277 sq., infra.)

* op een lepel vol water na Dutch version omnem fere aquam Latin
translation.

LETTER 96. 9 NOVEMBER 1695 209

In these my inquiries, I imagined that the unborn
mussels got eaten up by the little animalcules aforesaid ;
because it oft-times happened that I saw a multitude of
little animalcules that had got between the shells of the
young mussels, so that I judged, indeed, that I could even
see as many as fifty animalcules inside a single young
mussel. And during my observations, I observed that the
fishy matter in the unborn mussels got less from day to
day; nay, to such an extent even, that after the lapse of
twelve days, little or no fishy matter was to be discerned
between their little shells, which had become all trans-
parent. After this time, too, I could not perceive that
the animalcules were increasing in such great plenty.

My notion that the little animals were partly the cause
of the unborn mussels being eaten up (though ten
thousand of the little animals aforesaid would, for the
most part of them, scarce equal in bigness one of the little
mussels), was confirmed when I came to inspect the little
mussels (at the time when I had placed them in water in a
white Delft porcelain basin) after inclosing them in various
little glasses*; whereupon I perceived that each little
mussel inclosed in the little glass, though also lying in
water, still had its fishy substance between its shells,
notwithstanding that many of them had their shells wide
apart, or agape.

I have sometimes been puzzled when beholding the
multitude of little unborn mussels which lay inclosed in a
big mussel ; for I was not able to conceive why our canals,
and fens, are not overflowing with mussels, seeing that the
water does not run so strong that it could carry the little
mussels along with it, while they are still very small ;
and in the second place, seeing that they are not gathered
to serve as food: so that one mussel ought to beget
thousands. But now, after discovering how the little

" As mentioned below, these “little glasses” (glaasjens) were capillary
glass tubes, such as L. commonly employed in his experiments.

14

210 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

animals aforesaid devoured them, methought this a
sufficient reason why freshwater mussels are not found in
ereater plenty.’

After this, I let the water stand for twelve more days,
without replenishing it, in order to see whether, if I did
so, the animalcules would multiply in greater numbers.
But I perceived that the animalcules decreased from day
to day; so that by the 8th of October they were indeed
grown so few, that where I had before discovered a good
hundred of them, I now could scarce see one; and those
of the biggest sort, which still remained over, moved
forward very slow, and were very thin in the body; and
all the little shells of the unborn mussels had so far
increased in transparency, that I could make out some
hundreds of very little parts, whereof they were composed.
And so, from all these observations, I concluded that
all the various animalcules had now died for lack of food.

In order to satisfy myself further concerning the
plentevous multiplication of the little animalcules, and
in so very short a time, I took a parcel of canal-water,
somewhat more than a common wine-glass full, and put
in it an ordinary mussel, that I had taken out of its shell’ ;
and I put this mussel in the water to see, if ’twere
possible, whether the animalcules would multiply beyond
what they commonly do, owing to the food that they
would be able to get from the mussel.

After the mussel had lain for four-and-twenty hours in
the water, I took a little of the uppermost part of the
water, and examined it through the microscope; and I

' From these observations one can hardly doubt that L. had got
something more than an inkling of the part played by putrefactive micro-
organisms in the general oeconomy of nature. To appreciate the novelty
of this notion—nowadays commonplace— one must remember that it belongs,
historically, to the nineteenth century.

? In such an infusion of freshwater mussel many different Protozoa are
commonly found, including ciliates (e.g., Paramecium) and flagellates (e.g.,
Trepomonas). For this reason it is impossible to determine what particular
forms L. was likely to have seen.

LETTER 96. MUSSEL-WATER ik

saw, to my wonder, a vast number of animalcules. And
after the water, with the mussel in it, had stood for twice
twenty-four hours, I observed that the number of animal-
cules was greatly increased. I took a little of this water,
and put it in a glass tube, whose diameter was about
a fifteenth of an inch, and which was filled for about an
inch of its length with the water. In this water I saw a
few little animalcules swimming, whereof several thousand
together would scarce equal a sand-grain in bigness.
These animalcules had a pretty structure, for the round
circumference of their bodies seemed to be made up of ten
or twelve brighter round pellets, while in the middle of
them there seemed to be a little dark spot, somewhat bigger
than the pellets. These animalcules generally rotated
themselves in their progression (which took place
slowly).

When these animalcules had been a little while in the
foresaid glass tube, I saw a slender little structure like
unto a little branching vein, with seven or eight lesser
branches, each several little branch being full a hundred
times thinner than a hair off one’s head; and at the same
time I saw that at the utmost extremity of every little
branch, one of the forementioned little animals was firmly
fixt, though at first I could discover no motion in ’em.
Yet after the lapse of about a minute, I perceived that
some animalcules began to move themselves to and fro,
whereby each of the thin little branches became bent
into divers coils. The longer this motion continued, the
stronger it became, till at last the little creature, by its
efforts, got loose from the little branch, and swam off;
and the same thing came to pass with all the others too,
so that the little branching structure was forsaken by all
the animalcules that were discernible.”

i T

’ Probably ciliates—the bright bodies being food-inclusions, and the dark
central spot the meganucleus.

* This graphic narrative gives an unmistakable description of Carchesvwm.

212

1

ce

LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS ”’

From this spectacle, I imagined that the little animals
of this kind must have laid their little eggs, or young
animalcules, upon the ends of every little branch, and
that they had there waxed in bigness, and grown up.

Furthermore, this little branching vein was for the
most part clothed with a clearer matter, which I judged
was made up of round pellets. Seeing this, it came into
my head that all the round particles which I could see
might perhaps be really eggs, or young animalcules, and
that from these particles, moreover, similar animalcules
might presently come forth. After the lapse of another
twenty-four hours, I looked upon the little branch again ;
and I then saw that some animalcules, which had reached
their full growth, were fixed anew upon it; and that
many of these animalcules were swimming around the
little branch, while the roundish particles, that I’d seen
on the branch the day before, were much diminished in
number.’ ;

At a distance of about half an inch from the little
vein-branch aforesaid, there lay in the water a little fibre,
whereon were also fixed some little animals; and these too
were come forth (so I imagined) from the round corpuscles
which were likewise fixed to the fibre. These animalcules
were increased to such great numbers in the space of
twice twenty-four hours, that I now saw quite fifty of
them where I had before seen but one.

Now, as we have made sure that, in twice twenty-
four hour’s time, animalcules appear, which have reached
their full growth; and as we imagine that they have
come forth from little round particles: therefore, we need
not wonder at the multifarious little animalcules which
we perceive to be bred in water in only a few days’ time
(provided only that food be not lacking for them). And
who knows but what one sort of these very little water-

The observations here recorded were, no doubt, perfectly accurate :

but the interpretation which L. put upon them is, of course, incorrect.

LETTER 96. MUSSEL-WATER 213

creatures may not gobble up another sort, using it as
food,’ just as we see that big fish do? For, an ’twere
otherwise, the water would get stuffed full with little
animalcules.

One day afterwards I looked at the animalcules again,
and saw, to my wonder, that many of ’em were coupled;
nay, some of ’em even coupled before my eye; and at the
beginning of their copulation they had a wobbling motion,
but after coupling swam forward together, and did stay
still too, fixt to the glass.’

At this time I saw also that the bodies of each animal-
cule of the pair were of a roundish figure ; for no matter
how they turned about in swimming forward, they always
kept one and the same shape, looking like a little round
cluster of grapes, the cluster being stuck together very
tight; and as the animalcules swam forward, you saw each
of the supposed grapes in motion.

"Twas eventide when I carried out the observations
last mentioned; and next day, in the morning, I found
that many of the animalcules were dead, and by evening
they were so diminished, that I could find but four of
them that were still alive: wherefore I concluded, that the
little creatures were died off for want of food. After
another night had passed, I saw but one animalcule living ;
and the bodies of all the dead animalcules in the water
were so gone to pieces, that I saw nought but little round
particles (as they seemed to my eye), which made the
water, wherein these little animals had been swimming,
all troubled.

' As the “ bigger sort’ were, in part, ciliates, while the “smallest sort ”’
were bacteria, L.'s conjecture here was perfectly sound.

* This passage proves conclusively that L. observed the conjugation of
ciliates. In his earlier observations he had only seen the organisms joined
together; and consequently he may have seen ciliates really undergoing
fission—not conjugating. But here he says he actually saw them come
together, so that there can be no doubt as to the correctness of his
interpretation.

214 LEEUWENHOEK AND HIS “LITTLE ANIMALS”

Two days after the foregoing discoveries, I again beheld
the small parcel of water aforesaid in the glass tube; and
as I did so, I saw a huge number of extreme small fishes,
or animalcules, which I may call little eels,’ because in
swimming forwards they lashed their bodies like eels
do, and so quick that ’twas marvellous. These little fish
did mostly stay close beside one another, and round the
circumference of the tube, and in vast numbers; and in
my judgement their length was equal to the diameter
of one of those blood-globules which make the blood red.
And they remained alive some seven days, after which
time I could make out only one every now and then.

Among these little animals, or little fishes, I did also
see a-Swimming a few smaller animalcules, whereof I
deemed that eight of ’em together were no bigger than
the said blood-corpuscle*: and now I could no longer
discern that little structure that I heretofore likened to a
little branching vein, how oft soever I looked for it.
These last-mentioned animalcules were so prodigiously
increased in two or three days, that ‘tis incredible ; though
by now half the water was evaporated away.

All the water that I have so far spoken of, which I had
put in the glass tube, and wherein the foresaid multi-
plicity of little animalcules were bred, I deemed (to the
best of my knowledge) to be no more in bulk than the
eighth part of a green pea; but not being content with
this my estimate, I went and weighed a like quantity of
water, and I found its weight two grains. I did also
weigh some peas, and found that a common pea weigheth
eight grains.

Through the microscope with which I had carried out
the first observations, I imagined I still saw,* in water

* Probably Spirilla—certainly bacteria of some sort.

* i.e., their diameter was about half that of a red blood-corpuscle.
Undoubtedly bacteria.

° L., it will be recalled, commonly used a different microscope for each
separate observation—the object being more or less permanently fixed and
focussed before the lens.

LETTER 96. MUSSEL-WATER 215

taken from the surface of that wherein the mussel lay, a
vast company of living animalcules: but to make sure of
this, | made use of a glass of higher magnification, and
a different instrument: and I then saw so great a many
of such extreme small animalcules,’ that there’s no man
living could possibly conceive of them; nay, they were so
little, that several millions of them together would not be
as big as a coarse grain of sand. Nevertheless, all these
animalcules, when I put them in a glass tube, remained
alive but a little while.

Moreover, I found that the animalcules in the water
that the mussel was in, had increased so much in seven
or eight days, that I might well say their number was (to
the best of my judgement) quite ten times a hundred
thousand more than those in the water before I put the
mussel in it.

Regarding this increase of animalcules in water, and in
so very short a time, I have oft-times been amazed: and
especially, because I chanced to see divers sorts of
animalcules, which increased in numbers, without being
able to discern any of them that were smaller; all of
them being of an equal bigness.”

But after observing what I have just related (namely,
that there are animalcules which do not take to swimming
about till they have reached their full growth, and
which soon after are ready to copulate; and therewithal
that a full-grown animalcule is produced in one night), I
was now, to my great satisfaction, delivered from all
those difficulties, that I had for years laboured under,
concerning the generation of these little creatures.

When I first discovered, in the year 1675, a great
plenty of divers very little animalcules in water, and
made these observations known by letter to the Royal

’ Bacteria.

* He means that he could detect no young ones of any species.

216 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ’”’

Society in London, neither in England’ nor in France
could they accept of my discoveries: nor do they even yet
in Germany, as I’m informed.

This remarkable document ends at this point with a couple
of extracts from Leeuwenhoek’s letters of 23 March 1677 (to
Oldenburg) and 5 October 1677 (to Lord Brouncker), which
were sent to the Elector Palatine “to give him greater
satisfaction concerning the vast numbers of little animalcules
that are found in water”: but as these letters have already
been given fully on earlier pages,’ it is unnecessary to repeat
them here.

With these observations we come to the end of Leeuwen-
hoek’s researches on the free-living Protozoa and Bacteria, in
so far as they were made in the XVII Century. Later he
made many notable additional observations, but these will be
chronicled in a later chapter: and we must now retrace our
steps in order to record his equally wonderful discoveries
concerning the parasitic Protista.

* This can hardly be regarded as a fair description of the reception
accorded to L.’s earliest observations by the Fellows of the Royal Society.

* Vide pp. 168 and 173 supra. The second letter was originally addressed
to Oldenburg, but redirected to Brouncker when L. heard of his death.

217

CHAPTER 3

THE FIRST OBSERVATIONS ON ENTOZOIC
PROTOZOA AND BACTERIA

(Lerters 7, 33, 34, 38, 39, 75, 110, etc.)

E have already seen (in Chapter 1) how Leeuwenhoek
NV discovered the free-living Protozoa and Bacteria.
We inust now chronicle his discoveries in the world

of similar “ parasitic’ organisms.’
It will be remembered that Leeuwenhoek first saw protozoa
in water in the summer of 1674.* He probably first saw a
parasitic protozoon—though he had no idea what it was—in
the autumn of the same year. Whilst examining the bile of
various animals, he hit upon some curious structures which he
described, in the course of a rather rambling letter, in the

following terms: *

The bile of a cow was examined* by me on the Ist
instant,’ and therein I beheld some few globules” that
floated in the liquid ; but I didn’t see them unless I set the
bile in a continual motion before my sight, for ’twould else
have been impossible for me to perceive the globules in it,

* To call all such micro-organisms studied by L. by the opprobrious
name of © parasite” is hardly justifiable, for most of the forms which he
described cannot be regarded as harmful. They are “ parasitic” in a
colloquial and unscientific sense only.

” See p. 109.

> From Letter 7. 19 October 1674. To Oldenburg. MS.Roy.Soc.
This letter was wholly unpublished until recently, when I first published
(Dobell, 1922) the passages given here in revised translation.

* i.e., with the microscope.

° 4.e., 1 October 1674.

° clootgens MS.

218

~

LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

because they were so few in the bile that I was examining.
But afterwards, examining the bile of another cow, I
found that the globules were of a heavier matter than the
liquid that they floated in; wherefore I drew off the bile
from the bottom of the gall-bladder, and then found that
there were' many hundred times more globules in this
bile than in that which I had taken from the upper part
of the gall-bladder; and there were, besides, some
corpuscles * which, to my eye, looked as big as ants’ eggs.”
These had the figure of an egg,* only with this difference,
that whereas an egg is more sharply pointed at one end
than at the other, yet these corpuscles were equally
pointed at both ends: and moreover these corpuscles
were composed of globules joined together, and had a
yellow colour, except several which were somewhat
whitish ; but notwithstanding, they were so transparent
that you could see the body of one through that of
another. And this transparency making me wonder
whether they might not, in fact, be little vesicles filled
inside with liquid, I fished some of these corpuscles out of
the bile with a fine hair; and looking at ’em on the hair,
I perceived two which seemed to be pushed in, just as
though you had blown up a bladder and then stuck your
thumb in it, so as to make a dent in it; whereupon I was
the more firmly persuaded that these corpuscles were filled
with some sort of humor. Afterwards, on examining
more biles from oxen, I found them the same as before;
only with this difference, that one bile might be furnisht
with more of the oval corpuscles than another.

was MS.

* deeltgens MS.

8

L. means that the objects looked, under his microscope, about as big

as ‘ants’ eggs” look to the naked eye. At a later date he published a
remarkable account of ants, from which it is clear that he was well aware

that

the ant’s “egg” is not really an egg, but a pupa. See Letter 58,

9 Sept. 1687.

4

: )
2.€., a hens egg.

LETTER 7. 19 ocToBER 1674 219

In the bile of two calves I find, furthermore, some very
little globules floating, and very many irregular particles
of divers forms; among others, some like little floating
clouds, all consisting of very little globules joined together.
On seeing these irregular congealed particles, I judged
them to be joined or stuck together through no other
cause than because the bile had got cold, and was without
motion. In the bile of a third calf there wére a few oval
corpuscles.

Moreover, in the bile of sucking lambs I find there are
very little globules, and some, though very few, bright
particles, which are a bit bigger; besides irregular particles,
of divers figures, and also composed of globules clumped
together.

The bile of a yearling sheep I find to be like that of
sucking lambs, only with this difference, that in this bile
there are also oval corpuscles of the bigness and figure of
those that I remarked in ox-bile.

I have examined the bile of two young rabbits: that of
the first was inclined to a purple colour, and in it I beheld
very many globules, and irregular particles made up of
globules clumped together, which were of various red
colours:* and this diversity of colour I imagined to be
due to no other cause than that some of these compound
particles, being made up of more globules, were denser
than the rest. In the other bile the irregular particles
were fewer, but there were more globules and the colour
was a light reddish.

Further, I examined the bile from three old rabbits.
The first had a very few small globules, but very many
oval corpuscles of a figure like those that, as I have said,
I saw in the bile of a cow. In the bile of the two other
rabbits there was nought but globules, and irregular

* Evidently red blood-corpuscles. LL. had described these—from his
own blood—in another letter written earlier in the same year (Letter 3,
7 April 1674). An English abstract of this appeared in Phil. Trans. (1674),
Nol. EX. No. 102. pn. 23:

‘é

220 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

particles made up of globules joined together; though
the thin matter’ of one was much thicker and stickier
than that of the other, and there were some little clouds
floating through it.

I have furthermore examined the biles of fowls,
turkeys, ete., and in them I also found very little
globules floating, and irregular particles composed of
globules stuck together.

I think there can be no doubt that the “ oval corpuscles ’”—
called eyronde deeltgens in the original—which Leeuwenhoek
discovered in the gall-bladder of one of his “ three old rabbits,”
were the oocysts of the coccidian Himeria stiedae; while the
comparable structures which he found in the bile of sheep and
oxen were, equally certainly, the eges of trematodes.” But as
I have already discussed this subject in some detail elsewhere,’
I shall say no more about it here. If my interpretations be
correct, then the foregoing extract records the first observations
ever made upon the Sporozoa or upon any parasitic protozoon.

It is true that Leeuwenhoek himself did not realize that he
had discovered a stage in the life-history of a brand-new kind
of parasite: but the same can be said also of others who are
now generally credited with the discovery of the Coccidia.'*
The fact remains, none the less, that he saw and described—
though his description was not published for nearly 250 years—
a coccidial parasite long before all other men.

* i.e., the liquid part of the bile.

* Fasciola hepatica—the worm itself—was well known to L.; for the
Dutch anatomist Bidloo (1649-1713) dedicated a little memoir to him, in
1698, in which it was described and figured. At a later date, L. himself
wrote a letter to the Royal Society on the ‘ Worms observ’d in ae
Livers ’’—of which an English abstract was published i in Phil. Trans. (1704),
Vol. XXIV, p. 1522. The original letter is extant, and is dated 3 Nov.
1703. It was not included in the Dutch or Latin collected works.

* See Dobell (1922).

“ The lesions of hepatic coccidiosis in the rabbit appear to have been
first depicted by [Sir] Robert Carswell (1793-1857 ; Professor of Pathological
Anatomy at University College, London) in the year 1838. He regarded

them as “the seat of tuberculous matter.” The oocysts of E. stiedae were
first figured and described in print by Dr Thomas Gordon Hake (1809-

DISCOVERY OF COCCIDIA AND LEPTOMONADS 221

Leeuwenhoek’s next observations on ‘ animalcules”’
inhabiting the bodies of other animals were written down
in 1680 and printed some few years later. ‘They occur in the
course of his description of the spermatozoa of insects—various
species of which he dissected in his attempts to study their
“seminal animalcules”. After recording some findings in
flies, he casually adds the following: '

I have also seen, in the summer,’ in a big horse-fly
(which was a female, out of which I pulled many eggs), a
lot of small animalcules ; though these were not a sixth
of the length of the animalcules aforesaid,* but a good 10
times thicker.* They lay mingled with the thin matter ”
that was in the fly’s guts, and moved forwards very
quick.

From the size and proportions of the “ animalcules”’ here
mentioned, and from their situation, it can hardly be doubted
that Leeuwenhoek actually saw on this occasion a protozoon
(or possibly a bacterium) in the gut of a horse-fly. The
dimensions of the organism are against the bacterial inter-
pretation, but agree very well indeed with the supposition that
he saw a Orithidia (or Leptomonas).° If this was so, then we

1895; a practising London physician, and English minor poet) in 1839.
He interpreted the lesions as “carcinoma”, and the oocysts as “a new
form of the pus globule.” See Dobell (1922).

* From Letter 38. 12 November 1680. To R. Hooke. MS.Roy.Soc.
Published in Brieven, Vol. I (Dutch), and Opera Omnia, Vol. II (Latin).
The full letter first appeared in print (in Dutch) in 1684. An incomplete
English translation was published earlier, however, in Hooke’s Phil. Collect.
(No. 3, pp. 51-58; 1681). The passage here translated is on p. 23 of the
Dutch printed version.

* Presumably 1680.

° L. here refers—as the context shows—to the spermatozoa of “ the
smallest sort of our common house-fly.”’

* On L.’s system this means that they had rather more than thrice the
diameter of the fly’s spermatozoa.

° 4.e., liquid or watery material.

° These flagellates oceur—as is now well known—in many different
species of Tabanidae. Several species of Crithidia have been described, in
recent times, from the intestines of HKuropean species of Tabanus.—I may
add that, forty years ago, Biitschli (1887-89; Vol. III, p. 1101) pointed out
that the organisms here described by L. were probably flagellates; but he
wrongly dated the observations 1695—the date of publication of the first
Latin translation.

222 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

have here the first recorded observations ever made upon any
protozoa belonging to the important flagellate family of the
Trypanosomatidae. But this interpretation, though very
plausible, is not absolutely certain ; for the details recorded
are obviously too scanty to warrant dogmatic deductions.
Nevertheless, it can, I think, be concluded—with complete
assurance—that Leeuwenhoek observed “ parasitic” protists
of some sort in the intestine of a horse-fly as early as the
year 1680.

We now come to a letter of great historic interest and
importance—a letter which has rarely been read aright, but
one which records in no uncertain terms the discovery of the
intestinal protozoa and bacteria of Man. This letter was
written in 1681, and in it Leeuwenhoek discusses a variety of
subjects—such as the structure and falling-out of the hair,
“blackheads ”’ (comedones), clay, and gout: but the only part
which here concerns us deals with the discovery of “living
animalcules in the excrements.” ‘The passages in question
run as follows:'

I weigh about 160 pound, and have been of very nigh the
same weight for some 30 years,” and I have ordinarily of
a morning a well-formed stool; but now and then hitherto
I have had a looseness, at intervals of 2, 3, or 4 weeks,
when I went to stool some 2, 3, or 4 times a day.’ But

* From Letter 34. 4 November 1681. To R. Hooke. MS.Roy.Soc.
Published in fullin Brieven, Vol. I (Dutch), and Opera Omnia, Vol. I (Latin).
The Dutch version first appeared in 1686 (Ontled. en Ontdekk.), the Latin
[from which the date of the letter was omitted ] in 1687 (Anat. s. Int. Rerwm).
An English abstract was published by R. Hooke in Phil. Collect. (1682),
No. 4, p. 93: and another by Derham in the posthumous Phil. Expts. and
Obss. of Hooke (1726), p. 61. The letter itself was presented to the Society
at their meeting held on 2 Noy. 1681, and read in English translation at the
following meeting on Nov. 9 [O.8.]. Cf. Birch, Vol. IV, pp. 99, 101. Part
of this letter was also translated by Hoole in his Select Works of L.—but
not the part with which we are now concerned. I have already translated
and commented upon the paragraphs dealing with intestinal protozoa
elsewhere (Dobell, 1920).

* When he wrote this L. was 49 years old.

* The Latin version of this passage is somewhat ambiguous, and has
apparently led some readers to suppose that L. frequently suffered from
diarrhoea lasting for 2-4 weeks at a stretch. It has even, indeed, given rise
to the belief that he suffered from chronic dysentery for 30 years. His own
words do not countenance any such conclusions. Cf. Dobell (1920).

LETTER 34. 4 NOVEMBER 1681 293

this summer! this befell me very often, and especially
when I partook of hot smoked beef, that was a bit fat,” or
ham, which food I’m very fond of; indeed, it persisted
once for three days running, and whatever food I took, I
kept in my body not much > above 4 hours; and I
imagined (for divers reasons) that I could get myself well
again by drinking uncommon hot tea, as hath happened *
many a time before.

My excrement being so thin,’ I was at divers times
persuaded to examine it ;° and each time "T kept in mind
what food I had eaten, and what drink I had drunk, and
what I found afterwards*: but to tell all my observations
here would make all too long a story. I will only say that
I have generally seen, in my excrement, many irregular
particles of sundry sizes, most of them tending to a round
figure, which are very clear and of a yellow colour :’ these
were the ones that make the whole material look yellow
to our eye. And there were also, besides, suchlike
particles that were very bright and clear, without one
being able to discern any colour in them.”

I have, moreover, at divers times seen globules that
were as big as” the corpuscles in our blood, and that each

a

" i.e., anno 1681.

2

dat een weynig vet was. These words are in the printed version but

not in the original MS.—A similar remark is made by L. much later in
Send-brief XX XIX, 13 July 1717, to J. G. Kerkherdere.

3

veel is here in the printed letter, but not in the MS.

‘ is gelukt [=succeeded] MS. is geschied [ =befell] printed version.

> 7.e., dilute or watery.

6

7

8

9

i.e., with the microscope.

soo nu en dan MS. soo nu als dan printed version.

This word is not in the originals. I add it to preserve the sense.
Probably incompletely digested remains of meat (striated muscle).

0 fe., the faeces en masse.
11 Pyobably fat-droplets.

12 The Latin version mistranslates soo groot als as ° bigger than”
(globulos globulis nostra sanguinis majores vidi).

224 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS”

of them was made up of 6 separate globules :' and further,
there lay, among all this material, globules whereof 6 of
‘em together would make up the bigness” of a blood-
corpuscle. These last were in such great® plenty, that
they seemed to form a good third of the whole’ material:
while there were besides many globules which were so
small, that six-and-thirty of ’em would make up the bigness
of a blood-globule.’

All the particles aforesaid lay in a clear transparent
medium, wherein I have sometimes also seen animalcules °
a-moving very prettily; some of ‘em a bit bigger, others
a bit less, than a blood-globule, but all of one and the
same make. ‘Their bodies were somewhat longer than
broad, and their belly, which was flatlike, furnisht with
sundry little paws, wherewith they made such astir in the
clear medium and among the globules, that you might e’en
fancy you saw a pissabed‘ running up against a wall; and
albeit they made a quick motion with their paws, yet for
all that they made but slow progress. Of these animalcules
I saw at one time only one in a particle of matter as big
as a sand-grain; and anon, at other times, some 4, 5, or
even 6 or 8. I have also once seen animalcules of the
same bigness, but of a different figure. *

* At one time L. held the curious belief that each red blood-corpuscle
was composed of 6 aggregated smaller “globules”. This was an error
probably due, I think, to misinterpretation of diffraction-images.

* i.e., in volume—not in diameter.

* groote stands here in the MS. but not in the printed letter.

* gantsche MS. omitted from printed letter.

° 7.e., their diameter was between + and + of that of a human red
blood-corpuscle.

* The following description—as I have elsewhere tried to show (Dobell,
1920)—is a graphic account of the flagellate Giardia (=Lamblia)
intestinalis.

" The woodlouse or sow-bug (Oniscus asellus). The Latin translation of
this passage has given rise to many curious misunderstandings. Cf. Dobell
(1920), where “ pissabeds”’ are more fully discussed.

* As no other details are given, it is impossible to identify these
organisms. Possibly they were Trichomonas or Chilomastiz.

INTESTINAL PROTOZOA OF MAN DISCOVERED 225

I have also seen a sort of animalcules that had the
figure of our river-eels: these were in very great plenty,
and so small withal, that I deemed 500 or 600° of ’em
laid out end to end would not reach to the length of a full-
grown eel such as there are in vinegar.” These had a
very nimble motion, and bent their bodies serpent-wise,
and shot through the stuff as quick as a pike does through
the water.’

At another time I saw, in 4 several observations, but
one animalcule of the sort first spoken of;* but at my
fourth observation, observing more narrowly than before,
I saw a great number of animalcules,’ each of which I
judged to be more than 200 times less than a globule of
our blood: for I imagined that I could make out that the
length of six diameters of one animalcule couldn’t reach
beyond the diameter of one blood-globule. But here I
speak to those who are versed in geometry, and know full
well that if the diameter of one body be 1 and that of
another (of like figure) be 6; then the difference in their
bulk is as 1 to 216. And I can’t forbear to say that I
have divers times judged that I have seen, with great
delight, in a particle of matter of the bigness of a coarse
sand-grain, more than 1000 living animalcules, and these
of 3 or 4 sorts, all alive together; nay, you might well
have supposed that the whole material consisted of nought
but living animalcules. Some people hearing this might

cme EUS USSU

* The Latin version wrongly says “50 or 60” (quinquaginta aut
secaginta), which would—if correct—-put a very different complexion on
this passage.

> Anguillula aceti, the “ vinegar-eel’’. Cf. p. 150 swpra.

? From the description here given, it can hardly be doubted that these
organisms were spirochaetes. In recent years a vast literature has sprung
up on the intestinal species in man; but it must suffice to note here that
more than one species occurs in human faeces, and that spirochaetes of
some sort are normally present in the intestines of most human beings.
This is the first record of their occurrence.

* Referring to Giardia.

> Probably bacteria, but possibly inanimate particles in Brownian
movement.

15

226 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”

perhaps imagine that these animalcules, because of their
extreme littleness, might well get through into our blood ;
but I conceive that the vessels which conduct the material
(out of which blood, fat, etc. is made) are so small, or must
pass through such narrow channels, that even if such a
little animalcule were divided into more than 1000 parts,
‘twould still be too big to get through them.’

I have, moreover, examined my excrement when it was
of ordinary thickness, and also mixed with clean water,
but could then discover no animalcules in it; but
whenever the stuff was a bit looser than ordinary, I have
still seen animalcules therein, contrary to my expectation.
I have, however, also seen in it some particles of food that
were not digested; among others, for example, after I had
eaten asparagus I saw very prettily its little tubes (off
which the soft parts had been all digested away).

At divers times in the summer I have betaken myself
into our meadows, and collected the dirt of cows and
horses, just as they let it drop; yet I could discover no
living animalcules therein, but most of this stuff (setting
aside grass-particles which were undigested) was made up
of globules, whereof 6 would be as big as a blood-globule,
and many lesser globules of which I judged that 36
together would be only as big as a blood-globule; all these
lying in a clear medium.

In the month of May,’ I rode my horse (which is a
mare) very hard, for about 1% hour’s going;° and on
getting back to the stable, she let go her urine; and as
the last of this urine looked to me very thick, and was

" L. means that the channels—in the intestinal wall—through which
the ultimate food-particles in the gut pass into the blood-stream are too
minute for bacteria to traverse them: and that even if a bacterium were
but a tenth of its length, it still would be too big to do so.

> Presumably anno 1681.

* 14 wre gaens MS. The printed version says “an hour and a quarter ’
(een en een quart van een ure). Apart from this discrepancy in the time, it
should be noted that L. does not mean that he rode his mare hard for an
hour and a half (a pretty strenuous feat), but for a distance equal to that

y

INTESTINAL PROTOZOA AND BACTERIA O27

of an ashen colour, I viewed it’ through a common
microscope, that I had by me; and I found that what
gave it the ashen colour were globule-like particles, of
sundry sizes, each of ’em made up of still lesser globules
stuck together. And these last globules were as big as
the globules of our blood, and each of these again consisted
of six several globules. I can’t describe the first sort of
globules better than by likening them to a round bunch
of grapes, growing very close together, as it looks to your
naked eye ; and although the particles were not perfectly
round, yet I may call ’em globules, for they were wanting
in nothing but that those which were as big as a blood-
globule (which I have already described as compound)
stuck out a bit on the outside, like each grape does from
its bunch.” Of this matter I took up a little, and found
that besides the globules aforementioned there were yet
many others, which had a sixth of the bigness of one of
our blood-globules, and also some whereof I judged that
36 of ’em together would only make up the bulk of a
blood-globule.°

which would be covered in an hour and a half by a man on foot. (Cf. note
3 on p. 109 supra.) The Latin translator—who copies the time from
the printed Dutch version, not the MS.—accordingly renders this phrase
(correctly) as “ circiter horam atque horae quadrantem pedestris itineris. . .”

' In an earlier communication (Letter 38, 12 Noy. 1680), L. mentions
that he examined his own urine, at a time when he was sick, and found in
it—in addition to numerous particles—several red blood-corpuscles (ef. p. 12
of Dutch printed version).

* This is a hard sentence to translate closely and intelligibly. I give it
as near as I can—without improving it too much.

* The foregoing observations—though they record the discovery of no
new animalcules—appear to me to be of great importance; for they show
that L. really recognized living bacteria when he saw them. He did not
here—or elsewhere—mistake minute inanimate particles for “‘animalcules.”’
At first sight it may seem strange that he did not take all minute moving
particles for living organisms—as would have been indeed excusable.
‘“ Brownian movement’ was not “ discovered ” until a century and a half
later: but the phenomenon itself must have been frequently witnessed by
L. He accounted for it as a consequence of the heat imparted to his
microscopic preparations by their proximity to his own body. (He had to
hold his microscopes very close to his face, because of the very short focus
of his lenses.)

228

1

LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

I then bethought me to examine the dirt of hens; and
in order to get it clean, I squeezed the dirt out of a fowl’s
body as soon as it was dead. On viewing it, I saw
therein a huge number of little snakes or eels, which I
considered to be the fowl’s seed; as indeed it was. For
the cock was more than half full-grown ;’ and I took it
for certain that in squeezing out its dirt, I had compressed
its seed-vessels so violently that I squeezed the material
out of them too. Afterwards I squeezed the dirt out of
the hind end of several young hens, but I didn’t discover
anything but one living animalcule, which was about as
big as a sixth of a blood-globule. The dirt consisted,
further, of a clear matter, mixed with very many globules
as big as a sixth of a blood-globule. These also looked as
though they were composed of 2, 3, 4, 5, or 6 globules
stuck together. And there were besides very many wee
globules whereof 36 together (so I imagined) would be
only as big as a blood-globule.

I also” gently pressed the dirt out of two new-killed
pigeons, that were about a month old; and in the first I
couldn’t find any living animalcules at all. But in the
dirt from the second pigeon (which was much clearer
than the first’s) I saw many animalcules;* so that I
judged there were quite 100 of ’em in a bit as big asa
sand-grain. ‘These moved among one another very
prettily *, and were all of one and the same bigness,
having the figure of an egg, and being in my judgement
as big as a sixth part of one of our blood-globules.
Beyond this, the stuff was like what I have described
above from hens.

half volwassen MS. volwassen printed version. I follow the MS.

because it is difficult to comprehend how the bird could have been “ more
than full-grown’”’. The Latin translator evaded the ambiguity by calling
the fowl “ major annis gallus’’.

* ook MS. omitted from printed letter.

* Bacteria of some sort, in all probability.

* seer aerdig MS. but the Dutch printed letter says seer vaardig [| =very
quickly] —which is concordantly rendered expeditissime in the Latin.

LETTER 34. INTERPRETATIONS 229

The foregoing quotations—which contain, I believe, all
that Leeuwenhoek ever wrote on such subjects—record a series
of truly remarkable discoveries; and they prove conclusively
that he discovered intestinal protozoa and bacteria in man
and several other animals. He here saw, and recognizably
described, the flagellate Giardia' and the Spirochaetes and
other Bacteria in his own faeces. He also, I think, must have
seen other human intestinal flagellates (possibly Trichomonas
or Chilomastix), though this is uncertain: but he certainly
saw bacteria in the excrement of a fowl and in that of a
pigeon, though curiously enough he failed to find them in the
dung of cattle and horses.

Some of the interpretations which have been put upon
Leeuwenhoek’s words in this connexion must be read to be
believed. As I have commented upon them elsewhere’ I need
say no more about them here. I will only note that the
passages just quoted supply all the evidence there is for the
statement—frequently met with in the literature—that
Leeuwenhoek described the ciliate Balantidium coli, and that
he himself suffered from dysentery caused by this parasite.
Beyond all doubt this is a literary fiction lacking all
foundation. Though an Austrian nobleman® assures us
that Leeuwenhoek could not have seen what he described,
and therefore what he saw must have been something totally
different ; and though a distinguished American medico‘* tells
us that when Leeuwenhoek says he had weighed 160 lbs. for
30 years and usually had solid stools, he meant that he had
suffered from balantidial dysentery since the age of 30: never-
theless, serious students of protozoology may well rest content
with the plain and obvious meaning of his own simple words.

Before we proceed to the next discoveries, it may not be
amiss to emphasize the novelty of those just recorded. At the
time when the foregoing observations were made, no protozoa
or bacteria of any kind were known—except the free-living

* Of. Dobell (1920).

* Dobell (1920).

* Stein (1867), Vol. II, p.321. Although I exposed Stein’s blunders
some years ago, I note that a recent German writer (Pritze, 1928) still
accepts them. But as he evidently overlooked my paper, and knows nothing
of L.’s work, I cannot take his opinions seriously.

* Strong (1904).

230 LEEUWENHOEK AND HIs “ LITTLE ANIMALS ”’

forms described by Leeuwenhoek himself a few years earlier.
No animal or “‘animalcule” smaller than a worm was known
to live inside the body of man: and the existence of hordes of
micro-organisms within the bodies of healthy animals was as
wholly unsuspected as it was unheard-of.

It is worthy of note, moreover, that neither here nor else-
where in his writings does Leeuwenhoek associate entozoic
protozoa or bacteria with the causation of disease. He found
them in normal hosts, and it probably never occurred to him
that any of them might have pathogenic properties. Having
no medical education, and no preconceived notions regarding
““animalcules,” he recorded his findings simply and objectively,
and it was left to others to elaborate his great discovery into
the vast present-day corpus of medical protozoology and
bacteriology. In a sense, therefore, he missed the great
practical implications of his revelation." But it must not be
forgotten that the micro-organisms which he studied were all,
in all probability, harmless; and consequently he deserves
every credit for not speculating in excess of his facts. If
every worker on the same subjects during the next 250 years
had possessed an equally conservative and scientific spirit, a
great deal of unnecessary confusion in our knowledge of
“microbes ”’ might have been avoided.

No further observations on entozoic protozoa were recorded
until 1683. But in this year Leeuwenhoek wrote another
highly interesting letter, in which he described many novel
observations on frogs and other animals. He here accurately
described, and discussed, the frog’s spermatozoa and _ blood-
corpuscles—for the first time; and in the course of his
description he interpolated an account of various “ animalcules ”
which he had discovered incidentally. Some of these animal-
cules were undoubtedly protozoa, but they are so involved

* Contemporary medical workers, however, were not slow to seize upon
the pathological possibilities of L.’s discoveries. For example we find,
as early as 1683, that “the ingenious Fred. Slare M.D. and ¥.R.8.”,
commenting upon a murren” in Switzerland which carried off many
cattle, says: ‘I wish Mr. Leewenhoeck had been present at the dissections
of these infected Animals, I am perswaded He would have discovered some
strange Insect or other in them.”—Slare [alias Slear] (1647 ?-1727) was
a physician and chemist. He qualified at Oxford in 1680, and became a
Fellow of the Royal Society in the same year—just after L. himself.

LETTER 88. 16 guLy 1683 931

with the other matters mentioned that it is not always easy to
separate them. The passages in question—omitting irrelevant
details (duly indicated)—are as follows:!

The first frog that I dissected sat in the road; and it
seemed so weak from the cold,’ that though I gave it a
bit of a kick on with my foot, it didn’t jump away. When
I picked it up and opened it, I found ’twas a female, in
whose guts there were worms, which had the shape of
those worms that children void in their stools.’ These
worms * were about as thick as a hair off one’s head.’

But what most surprised me was, that I observed in the
blood (which had run out of the many blood-vessels that
Thad cut, into the clean ° dish in which I dissected the frog)
a great number of living animalcules,’ which were about

" From Letter 38, 16 July 1683 [N.S.]. To Christopher Wren.
MS.Roy.Soc. Read at a meeting of the Society held on July 18 [0.S.] —
not on July 11, as appears (owing to omission of a date) in Birch, Vol. IV,
p. 215. Published in Brieven, Vol. I (Dutch) ; Opera Omnia, Vol. I (Latin).
The Dutch version first appeared in 1685 (Ontled. en Ontdekk.), and the
first Latin version in the same year (Anat. et Contempl.). In both of these
the letter is dated correctly : but in the Op. Omn. (and in the earlier Anat.
s. Int. Rer. [1687], which contains a 2nd edition of the Latin letter) it is
misdated July 26. A short English translation was published in Phil.
Trans. (1683), Vol. XIII, No. 152, p. 347; and this was therefore the first
version to appear in print. Hoole also translated a part of this letter, but
not that which here concerns us. My translation is based primarily upon
the original MS.

* In a previous (untranslated) paragraph it is noted that these frogs
were studied on 1 April 1683, when they were coupling. It is thus certain
that the species was Rana temporaria—not R. esculenta, which breeds later.

* Probably meaning Oxyuris (=Enterobius) vermicularis.

“The “worms” found in this frog were obviously not protozoa or
bacteria but nematodes; and— if the foregoing identification of Oxywris be
correct—they were probably Ozysoma brevicaudatum, which is very
common in R. temporaria.

° A description of the blood-corpuscles of the frog is here omitted.
° schone printed version. Not in MS.

" When all the particulars related are taken into account—size, host,
origin, movements, etc.—I think there can be very little doubt that this
‘animalcule”’ was Trichomonas (or Trichomastia ?) batrachorum.

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” al
”

s e
i* Ww

.

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232 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

half as long and half as broad as one of the oval blood-
corpuscles ; all being of one and the same structure.
‘Twas no small pleasure to see this sight: for I had let
so much time slip by, that the oval blood-corpuscles were
sunk down somewhat (owing to their weight) towards the
bottom, and then these animalcules made a pretty motion,
for as they went a-swimming, they knocked into the
blood-corpuscles, and sent them spinning. And I judged
that in every particle of blood as big as asand-grain there
were quite 50 animalcules.

The blood aforesaid was very watery, and not pure
blood by any means: for as soon as I separated a good
bit of the frog’s skin from the flesh, some watery juice‘
began to run out of the skin, as well as the flesh ; and still
more when I opened the belly. And as I had well-nigh
bashed in the frog’s head, trying to make it keep quiet,
methought some watery juice might well have been
squashed out of its mouth or stomach too, and from this
juice the animalcules might have come; for when I
afterwards took blood out of the frog’s veins clean, I
could discover no animalcules therein; neither when
I viewed the watery matter which came from between the
skin and the flesh, nor yet in that from the hollow of the
belly.’

In the foresaid watery matter, I noticed some irregular
particles, most of which looked to me round, and were about
as big as the globules of our blood. In some of these’ I
could make out that they were composed of 6 lesser
globules; and there were besides particles that seemed
only about 4 of the bigness of the others. And when I

* 4.¢., lymph.

* From the foregoing and succeeding passages it is clear that L. satisfied
himself that there were no animalcules in the blood or lymph: and
consequently there is no foundation for the statement—sometimes made—
that he discovered protozoa in the blood of the frog.

* Plasma-cells, from the lymph. The smaller “ globules” inside them
were doubtless the large basophile granules contained in such cells.

" wl y
dete Be

real
PAs

ie

PLATE XXIII

LEEUWENHOEK’S PICTURES OF THE INTESTINAL PROTOZOA OF FROGS
From the engravings in the Dutch edition of Letter 38 (16 July 1683). X 13.

Fig. A, Opalina (Cépédea) dimidiata.
Fig. B, Nyctotherus cordiformis.
Fig. C, a larval nematode ?

facing p. 233

PROTOZOA OF FROGS DISCOVERED 233

examined the said watery blood of divers frogs, that had
run out into the dish (for I took a clean dish for each
several frog), a very few animalcules were‘ to be seen in
it once more.

Because I couldn’t satisfy myself about the animalcules
aforesaid, though I was sure they didn’t belong to the
blood itself, but were gotten into it by accident; in the
month of June* I continued my observations, and at
last I came across some frogs* in whose dirt, which I
took out of the guts, I beheld an unconceivably great
company of living animalcules, and these of divers sorts
and sizes. ‘The biggest sort “ had the shape of Fig. A.2 Of
these I judged there were quite 40 in a quantity of
material as big as a grain of sand. ‘The second sort” had
the figure of B: these were very fewinnumber. The third
sort had very near the shape of our river-eels, as Fig. C:
these were in even greater plenty than the first. And
moreover the whole material was so full of little animal-
cules, that the very dirt seemed to consist of nothing but
little living animals; for the little particles of the dirt
itself were so stirred’ by the motions of the animalcules,
that they looked almost as though they were themselves
animalcules too.© The number of the little animalcules

* is MS.—corrected to zijn in printed version.

> Anno 1683.

* The species is not discoverable from this description, but the protozoa
found indicate that they were Rana esculenta—not R. temporaria. lL. knew
well (and could distinguish) both species. In Letter 65, 7 Sept. 1688, he
tells us that there are two kinds of frog (vorsch) in Holland—the common
“kikvorsch”’ [= R. temporaria], and the larger “ work” [= R. esculenta]
which is “ eaten by the French.”

* Opalina (Cépédea) dimidiata—without a doubt.

> hadden de fig: van. A MS. hadden de gedaante van Fig. 3. A. printed
version. See Plate XXIII.

° Nyctotherus cordiformis : but see below.

"wiert . . . bewogen MS.—corrected to wierden . . . bewogenin
print.

* This graphic description must appeal to every worker who has studied
the intestinal protozoa of frogs, for it vividly describes the usual appearance

234 LEEUWENHOEK AND HIS “LITTLE ANIMALS”’

last spoken of was so great, that I judged there were
several thousand of ’em in every bit of matter as big as a
sand-grain.

On seeing this, I took it for certain that the animalcules
which I said before were in the blood (which I had taken
out of the dish), came to be there only in this way:
namely, because the frog, when it was being cut up,
voided its dirt into the dish, or because I had unwittingly
wounded the guts of the frog, in whose dirt there must

have been many animalcules, which got mixed with the
blood.

It has been generally allowed that the larger animalcules
which Leeuwenhoek here described and figured (his Figs. A
and B) were ciliates—which occur so commonly in the guts
of frogs. But it is possible, I believe, to identify them more
exactly. To anybody familiar with the intestinal fauna of
the two common frogs of Northern Europe (Rana temporaria
and R. esculenta), it must be obvious that the abundant long
organisms (Hig. A) were Opalina (Cépédea) dimidiata, while
the smaller, scantier, and more rounded creature (Fig. B) was
Nyctotherus cordiformis. Both of these occur very commonly
in Lana esculenta, and I therefore infer that the frogs which
Leeuwenhoek was studying on this occasion were of this
species.”

It would have been impossible to determine the exact
species of these ciliates before the intestinal protozoa of frogs
had been adequately studied. Consequently, most of the early
identifications are not worth serious consideration. The first
correct determination we owe, I think, to Biitschli, who says

of frogs’ faeces under the microscope. The “animalcules’”’ responsible for
the phenomenon are flagellates (Trichomonas, Trichomastix, Chilomastiz,
and Hexamuta), and various motile bacteria.

" O. dimidiata is well known as the characteristic species of opalinid
from this host: Nyctotherws, however, is usually described as occurring in
i. temporaria only. That the above statement is correct I know from my
own observations.

* The frog in which L. found the worms previously was—as already
noted—f. temporaria: but there is nothing in his words to prove that the
frogs of the second batch were not of the other species. If they were, then
the above identification amounts almost to a certainty.

OPALINA AND NYCTOTHERUS Zao

that in Leeuwenhoek’s description “ Opalinae and Nyctotherus
can be recognized with sufficient certainty.”* No species are
indicated, though the two which I have mentioned must, I
think, have been intended. Saville Kent, however, had
previously identified Leeuwenhoek’s Fig. A as Opalina
intestinalis :” but this is highly improbable, because there is
no certain record of this species having ever been found in
either R. temporaria or R. esculenta.’

Metcalf, who has studied the Opalinidae in greater detail
than any other specialist, writes of Leeuwenhoek’s observations
as follows : *

‘“ Opalina was first mentioned [?] by Leeuwenhoek in
1685° [?]. In his Opera omnia (1722) he quotes the earlier
record [?] of finding innumerable animalculae [sic] of
various sizes and forms in the foeces [sic] of the frog. One
of these figured [L.’s Fig. B] seems in all probability to have
been O. ranarum. Another may have been O. dimidiata
DRG ya cates. diag

From this it seems to me that Metcalf cannot have studied
Leeuwenhoek’s works or words very carefully, nor does he
- appear to appreciate the difficulties of his own interpretation.
If—as he suggests, and as I am convinced—Fig. A represents
O. dimidiata, then the smaller rounded form (Fig. B) can
hardly have been O. ranarum. For this species is at least as
large as O. dimidiata, and occurs typically in a different host—
RR. temporaria.” Consequently, if Metcalf’s interpretation
were correct, it would leave the small size of Fig. B un-

' Biitschli (1887-89), Vol. III, p. 1101. The date of the observations is
wrongly given, however, as 1687. Cf. also zbzd., pp. 1718 and 1721.

* Kent (1881-82), Vol. II, p. 562.

* Opalina (Protoopalina) intestinalis is a species proper to Bombinator—
not Rana. Cf. Metcalf (1923), p. 51. Kent’s error was first noted by
Metcalf (1909), p. 319.

* Metcalf (1909), p. 319. My comments are interpolated in square
brackets for the sake of brevity. In my opinion this single sentence
contains at least six mistakes, but it seems unnecessary to do more than
indicate them.

° In a later work (Metcalf, 1923, p. 438) the date is given as 1865 [! ]—
presumably by misprint of the first date (1685), which was itself incorrect.
Little errors of this sort abound in nearly all discussions of L.’s work.

° I know of no certain record of O. ranarwm having been found in R.
esculenta, or of O. dimidiata from R. temporaria. Cf. also Metcalf (1923).

cc

236 LEEUWENHOEK AND HIs “ LITTLE ANIMALS”
explained, and would necessitate the assumption that
Leeuwenhoek found his ciliates not merely in two different
frogs, but in frogs of two different species—of which there is
no indication whatever in his own writings. But if, on the
other hand, it be agreed that Fig. A shows O. dimidiata, then
the frog was a specimen of R. esculenta, and the smaller ciliate
was Clearly Nyctotherus—not an opalinid at all. The figure
certainly suggests this strongly, and everything else supports
this obvious, natural, and easy interpretation.

When we come to consider Leeuwenhoek’s Fig. C, however,
we are faced with very grave difficulties. This organisin is
said to have been like a “‘ river-eel ”’, and to have been abundant
in the frog’s faeces: and in size it appears, from the figure, to
have been longer than a Nyctotherus—though the drawings
were not made accurately to scale. Elsewhere in Leeuwen-
hoek’s writings we find nematodes (Anguillula, etc.), spirilla,
and spirochaetes, all likened to “eels”: and in the rectal
contents of . esculenta we may find not only various species
of nematodes, spirilla, and spirochaetes, but also long flexible
and actively motile bacilli (Bacillus flexilis and similar forms).
To determine which—if any—of these Leeuwenhoek may have
seen on this occasion, is I think impossible. I must therefore
leave Fig. C unidentified, though I am inclined to believe that
it depicts a larval nematode.

I conclude, consequently, that Leeuwenhoek discovered
and described Opalina, Nyctotherus, and Trichomonas (or
Trichomastix) in the faeces of frogs, in addition to various other
protozoa and bacteria which are not now identifiable.’

And now we come to a letter which is, perhaps, as famous
as any Leeuwenhoek ever wrote to the Royal Society—the
one containing his account of the ‘‘ animalcules”’ in the human
mouth. This letter is frequently quoted—or rather mis-

" For example, there is a definite indication of the mouth, and the
outline is—to me—quite convincing. The interpretation of Fig. B as
Balantidium coli—recently put forward by Pritze (1928)—is so outrageous
as to deserve no further notice.

* I ought perhaps to point out that Prowazek (1913) has identified some
of these organisms with Balantidiwm coli. Although he has been copied by
others (e.g. Pritze, 1928), his interpretation is manifestly absurd. There is
no evidence that L. ever saw any species of Balantidiwm in the frog, and
B. colt certainly does not live in this host.

LETTER 88. CONCLUSIONS Ao tT|

quoted—by bacteriologists, and is usually said to be the first
memoir in which bacteria of any sort are mentioned. How
far this 1s true, readers of foregoing quotations can judge for
themselves. References to this important epistle, addressed
to Francis Aston, Sec.R.S.," are almost invariably given
incompletely or incorrectly ; and this is doubtless due in
part—though not altogether—to the fact that many versions
of it are extant. Moreover, many different interpretations of
the organisms described have been advanced, and this has led
to some truly astonishing conclusions. Yet Leeuwenhoek’s
words are, as usual, plain and straightforward, while the
interpretation of his observations appears to me obvious. To
anybody familiar with the flora and fauna of the human
mouth they surely present no difficulties. I shall therefore
give his own words (as well as I can) first, and shall comment
upon them afterwards—adding exact references but ignor-
ing many manifestly absurd statements made by other
commentators.
The passages in question run as follows: ?

* Concerning Francis Aston little is now known. (He is not mentioned
in the Dict. Nat. Biogr.) He was elected F.R.S. in 1678, and became
Secretary in 1681—a post which he suddenly threw up in 1685 (ef. Rec.
Roy. Soc., and Weld, I, 302). Afterwards he received a gratuity from the
Society (Weld, I, 305), and on his death bequeathed to them his estate at
Mablethorpe in Lincolnshire, together with his books and instruments
(Weld, I, 428). His portrait now hangs in the apartments of the Society
at Burlington House (at the foot of the staircase). For the following
additional information I am indebted to Mr H. W. Robinson, Assistant
Librarian of the Royal Society: Aston was born about 1644, and died in
June or July 1715. He went to Westminster School in 1656, and was
King’s Scholar in 1660 (aged 16). He entered Trinity College, Cambridge,
in 1661, and became Fellow in 1667. (B.A. Cant. 1664/5: M.A. 1668.)
He travelled abroad for some years, and in his youth was an intimate friend
of Isaac Newton.

* From Letter 39. 17 September 1683. To F. Aston. MS.Roy.Soc.
Published in Brieven, Vol. I (Dutch), and Opera Omnia, Vol. II (Latin).
The Dutch version was first printed in 1684 (Ondervind. en Beschouww.
pp. 1-19), the Latin in 1695 (Arc. Nat. Det. pp. 41-53). Both versions are
wrongly dated the 72th of the month (‘‘ den 12 Septemb. 1683” and “ pridie
Iduum Septembris 1683”) apparently through a misreading of the MS.
Owing, it would seem, to some oversight, two different English abstracts
appeared in the Plil. Trans. The first was published in Vol. XIV (1684),
No. 159, p. 568 [b¢s—a misprint for 598]: the second in Vol. XVII (1693),
No. 197, p. 646. [The first—published 20 May 1684—is the fuller and
better.] Hoole (1798) has given a third—and as far as it goes the best—

938 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

I have ere this sent you my observations concerning
spittle, which I see have been made public in print in the
Lectures and Collections published by Mr. Robert Hooke,
Secretary of the Roy. Soc., in the year 1678.’ Since
that time I have made divers further observations on
my spittle, with the idea that if there be any animalcules
lying about in the body, they would get into the mouth,
sooner or later, through the spit-ducts; but in what
observations I made to this end, I could make out no
animalcules there, nor could I say aught else but what
I have hitherto writ.

"Tis my wont of a morning to rub my teeth with salt,
and then swill my mouth out with water: and often,
after eating, to clean my back teeth with a toothpick, as
well as rubbing them hard with a cloth: wherefore my
teeth, back and front, remain as clean and white as falleth
to the lot of few men* of my years,’ and my gums (no

partial English translation in Select Works, Vol. I, p. 118. Léffler (1887,
p. 5) has translated a fragment into German, but he misdates the letter
September 14. It was read at a meeting of the Society held on 24 October
1683 [O.S.]: ef. Birch, Vol. IV, p. 219. Various reproductions of the
illustrative figures are noted below (p. 244 et seq.). They have already
given rise to much confusion and misstatement.—-Though there are already
at least one Dutch, two Latin, and three English versions of this letter in
print, I rely upon the original MS. (in L.’s own hand), from which my
translation has been made.

"A reference to Letter 23, 14 January 1678. To R. Hooke.
MS.Roy.Soc. English version (incomplete) published in Hooke’s Lect. &
Collect. (1678), part II, Letter 2, p. 84. (Reprinted in Hooke’s Lect. Cutl.
(1679) pt. V.)—This letter contains an account of certain ‘‘ Globules in the
Flegm’’: but L. had examined saliva still earlier, for in Letter 4 (1 June
1674, to Oldenburg) he notes that ‘‘In clean spit, examined by me in the
morning, I find a few very little particles floating in the liquid; whereof
I saw some sink to the bottom; as also divers irregular particles, some of
which seemed to consist of globules stuck together. And in the spittle that
I examined in the afternoon, I found the globules and irregular particles in
greater plenty”. (MS.Roy.Soc. Partial English translation in Phil. Trans.
(1674), Vol. IX, No. 106, p. 121.)

* als er weijnig menschen van mijn Jaren sign MS. als weynig
menschen . . . gebeurt printed version.

* When he wrote this, L. was approaching his 51st birthday. He tells

ey Mi
iy Tf

is Me

j 4 i pean i
a
Woathy o ih a re

1 Kt ae ta

cr a |
Nunet _ a

; i Ay R)
Oh yent TA af ii i at

fe

if a

* ng ae oe

, ay AS No is ay my) ia A

a i ani on
nn oe ee oe er a ice ; ke ts

nag a ele Pea Al)

ua ea mn es ay
aa

a ie ‘ is

PLATE XXIV

LEEUWENHOEK’S FIGURES OF BACTERIA FROM THE HUMAN MOUTH
(Letter 39, 17 Sept. 1683)
Enlarged (X 13) from the engravings published in Arc. Nat. Det., 1695.

Fig. A, a motile Bacillus.

Fig. B, Selenomonas sputigena. C....D, the path of its motion.

Fig. E, Micrococci.

Fig. F, Leptothrix buccalis.

Fig. G, A spirocheete—probably “ Spirochaeta buccalis,” the largest form found
in this situation.

facing p. 239

LETTER 39. 17 SEPTEMBER 1683 939

matter how hard the salt be that I rub them with) never
start bleeding. Yet notwithstanding, my teeth are not
so cleaned thereby, but what there sticketh or groweth
between some of my front ones and my grinders (whenever
I inspected them with a magnifying mirror), a little
white matter, which is as thick as if ’twere batter.” On
examining this, I judged (albeit I could discern nought
a-moving in it) that there yet were living animalcules
therein. I have therefore mixed it, at divers times, with
clean rain-water (in which there were no animalcules),
and also with spittle, that I took out of my mouth, after
ridding it of air-bubbles (lest the bubbles should make
any motion in the spittle): and I then most always saw,
with great wonder, that in the said matter there were
many very little living* animalcules, very prettily
a-moving. The biggest sort had the shape of Fig. A*
[Plate XXIV]: these had a very strong and swift
motion, and shot through the water (or spittle) like a
pike * does through the water. ‘These were most always
few in number.

The second sort had the shape of Fig. B. These oft-
times spun round like a top, and every now and then
took a course like that shown between C and D: and
these were far more in number.

us elsewhere, however, that he sometimes suffered from toothache—to
alleviate which he smoked a pipe of tobacco, which generally made him
feel very sick. He also tells us later how some of his teeth decayed.

‘ Nogtans printed version—omitted in MS.

* beslagen meel MS. and Dutch printed version “wetted flower” Phil.
Trans. (1684) “like a mixture of flour and water” Hoole farinae aqua
subactae similem Latin edition. The 2nd Phil. Trans. version (1693)
incorrectly calls this soft mealy material (materia alba) ‘‘a kind of gritty
Matter.”

* levende is here in the MS. but not in the printed version.

* hadde de Fig: van A. MS. was van de Fig: A. printed version.

® een snoek MS. and Dutch printed version. The Latin translator
rendered this—with some justification—piscis lupus: which caused Loffler
(1887, p. 5) to mistranslate it ‘‘ Rauwbfisch” (instead of Hecht). To “ shoot
through the water like a pike” is a phrase commonly used by L. to describe
any rapidly darting aquatic animalcule.

240

1
2

3

Lat.

LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

To the third sort I could assign no figure: for at times
they seemed to be oblong, while anon they looked
perfectly * round. ‘These were so small that I could see
them no bigger than Fig. HK: yet therewithal they went
ahead so nimbly, and hovered so together, that you might
imagine them to be a big swarm of gnats or flies, flying in
and out among one another. ‘These last seemed to me
e’en as if there were, in my judgement, several thousand
of ’em in an amount of water or spittle (mixed with the
matter aforesaid) no bigger than a sand-grain; albeit
there were” quite nine parts of water, or spittle, to one
part of the matter that I took from betwixt my front
teeth, or my grinders.

Furthermore, the most part of this matter consisted of
a huge number of little streaks, some greatly differing
from others in their length, but of one and the same thick-
ness withal; one being bent crooked, another straight,
like Fig. F, and which lay disorderly ravelled together.
And because I had formerly seen, in water, live animal-
cules that had the same figure, I did make every
endeavour to see if there was any life in them; but
I could make out not the least motion, that looked lke
anything alive, in any of ’em.

I have also taken spittle from the mouths of two
different womenfolk,’ that I’m sure clean their teeth
every day, and examined it as narrowly as I was able to,
but could discern therein no living animalcules. But
afterwards I examined the same spittle mingled with
a little of the matter that I picked out with a needle from
betwixt their teeth : and then I discovered as many living

volkomen is here in the printed text, but not in the manuscript.
was MS.—corrected to waren in print.

twee distincte Vrouwspersonen MS. and Dutch ed. binaruwm foeminarum
5 ce ?
ed. ‘‘two several women” Phil. Trans. (1684) other Persons ”’

Phil. Trans. (1693) “‘ two ladies’ Hoole (1798). It is almost certain that
these were L.’s own womenfolk—his second wife Cornelia, and his daughter
Maria.

PLATE XXV

Cle odo eve Len Soe bch WI & he oars on gel , Lu
Sohoefen gree hi rterater po fission ocses
AD Chex fo DEN TS
feos Sot Oe why an a WEA
Ee je re meh C. em D. tf atm poweden \' Soke learner
Creel am cerder amt geht. Jhon de: (eDe Srost- Poul Mat

~~, Seo clin LOB spew) eno De ander
4 ne A ‘a - ele Date! binerce Soe Ze. oat
eh eleles & age cee LeQe devi eee ha E. mat

ew eer. Cae he far So
ea, cr a Astin’ "Nets nna shp
.

hwel te Gerren men { dat-iL cordece cen
Soi ER te ry ae
(Oem x amet Ve ie 5% of peed

Rae Asem Shevere

ettte rmatene Ky etn over
ae ye abe. (GEL (ee ies. Klidentre Cle phi ouwe +5 aD

4, ogtang Comm Lon ade Deh. =: ibe Scull
Vie tier te mete Bk cpt Py Fs ange,
ro es SMES SP ie we ao
wwe Dea oak ee ington Tae Laven Seb leo
aii 4! Aaildesin se Ae heb 1k, atte (Qeserreny : oon Blond — pO
"£3 S Bic ph de ae VWogex m cai On aor ik heb 9 eeu

)
Peuwregr, aft rie gf there: gelek , ja ay~
ys Anan 4 < an J f ‘2 sy o d nti
A PAGE OF THE ene tie HOLOGRAPH MS. OF LETTER 39
(17 Sept. 1683: leaf 2 recto = page 8),
containing part of Leeuwenhoek’s description of the Bacteria in the mouth.
Facsimile. (The first word is [desel] ve, continued from the previous page.)
This is a good sample of Leeuwenhoek’s handwriting at this period.

facing p. 240

ee CA rey aU Pep me MUN ee emt es et ee
“oy eiy : ih NI. 3 aie va ne ay OL Pa iy bik
ay ve halt Bs Wb eee See “3 kk 4 Py Tue J) Md " rr ~

op ee aad ne
% tee, caNT eo
; a i he ; hid Bh . i tor ae a oy re : we - o i
Farben me ii me! ata: GIN apt!

Ccemauenen ett par pers
ae Ce ae me mag

yey i

ae . re tan 7 ee

a Le te, 5 date}
A} rca! weer; agit) See a 2: =e 5 tf \ Atel rie

sie a eh Pith ene + es

‘ he | wee

77° Sey
"a
o seca) Sie As
tant 7 \ P), oy Hye Em
. 7 ’
aA Wiki te c g }
7 i be | i
t vans ask
it: ey - ‘aye a i
h 4 8 is
eo 14
ee eee

Poe ie presge af
an te i 2 ru a yeu!

: - wi f

ae Ht » i, ~* aie ; , ; : ~ a

al hoe el i ona

7 ee 77 h
ae ee
7 ager be
Disa ie} iikennk 1h

| any ah a _ yids: ah

a % ‘ ans Aas i waka
ke ~~ va ie

oa An oN oN

ton - ie

‘
i ea i

i. yor ile

ay haere i

BACTERIA IN THE HUMAN MOUTH 241

animalcules, together with the long particles, as herein-
before related.

I have also examined the spittle of a child about eight
years old, and likewise could discover no living animalcules
therein ; and afterwards the same spittle, mixed with the
stuff that I got out from atween the child’s teeth: where-
upon I perceived as great a many animalcules and other
particles as heretofore made mention of.

I didn’t clean my teeth (on purpose) for three days
running, and then took the stuff that had lodged in very
small quantity on the gums above my front teeth; and I
mixt it both with spit and with fair rain-water;* and
I found a few living animalcules in it too.

While I was talking to an old man (who leads a sober
life, and never drinks brandy or tobacco,’ and very seldom
any wine), my eye fell upon his teeth, which were
all coated over; so I asked him when he had last cleaned
his mouth? And IJ got for answer that he’d never washed
his mouth in all his life.” So I took some spittle out of
his mouth and examined it; but I could find in it nought
but what I had found in my own and other people’s. I
also took some of the matter that was lodged between and
against his teeth, and mixing it with his own spit, and also
with fair water (in which there were no animalcules), I
found an unbelievably great company of living animalcules,
a-swimming more nimbly than any I had ever seen up to
this time. The biggest sort (whereof there were a great
plenty) bent their body into curves in going forwards, as
in Fig. G. Moreover, the other animalcules were in such
enormous numbers, that all the water (notwithstanding

' water MS. vregen-water Dutch printed version.
2 In olden times it was customary to speak of “ drinking” tobacco—
)

both in Holland and in England—though it meant “ smoking ” (as we now

* Hoole (1798, p. 119)—with his usual squeamishness—purifies these

coarse details into more polite observations upon “ the teeth of an old
gentleman, who was very careless about keeping them clean.

16

242

cc

LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS”

only a very little of the matter taken from between the
teeth was mingled with it) seemed to be alive. The long
particles too, as before described, were also in great
plenty.

I have also taken the spittle, and the white matter that
was lodged upon and betwixt the teeth, from an old man’
who makes a practice of drinking brandy every morning,
and wine and tobacco in the afternoon; wondering
whether the animalcules, with such continual boozing,
could e’en remain alive. I judged that this man, because
his teeth were so uncommon foul,’ never washed his
mouth. So I asked him, and got for answer: ‘‘ Never
in my life with water, but it gets a good swill with wine
or brandy every day.” Yet I couldn’t find anything
beyond the ordinary in his spittle. I also mixed his spit
with the stuff that coated his front teeth, but could make
out nothing in it save very few of the least sort of living
animalcules hereinbefore described time and again. But
in the stuff I had hauled out from between his front teeth
(for the old chap hadn’t a back tooth in his head), I made
out many more little animalcules, comprising two of the
littlest sort.

Furthermore, I put some strong wine-vinegar in my
own mouth, and then set my teeth, and let the vinegar run
betwixt ’em time after time: and after doing so, I rinsed
my mouth out thrice with fair water. Afterwards I once
more fetched out some of the foresaid stuff from between
my front teeth, as well as from between my grinders ;
and I mixed it divers times both with spittle and with
clean rain-water: and most always I discovered in it
an unbelievable number of living animalcules, though most
of ’em were in the matter I got from between my back
teeth, and only a few had the appearance of Fig. A.

1

Hoole (1798) prudishly refrained from translating the observations

made upon this disreputable ‘old gentleman”’, who, in the Phil. Trans.

(1684), is called simply—without other descriptive detail—" a good fellow ”.

”

2 ongemeen vurjl MS. buyten gemeen vuyl printed letter.

1

BACTERIA IN THE HUMAN MOUTH 243

I have also put a little wine-vinegar to this stuff mixed
with spittle, or with water: whereupon the animalcules
fell dead forthwith. And from this I drew the conclusion
that the vinegar, when I filled my mouth with it, didn’t
penetrate through all the matter that is firmly lodged
between the front teeth, or the grinders, and killed only
those animalcules that were in the outermost parts of
the white matter.

In several of the observations aforesaid, I saw on 2 or
3 occasions some very bright transparent particles,
whereof many were perfectly round, others having an
irregular round figure. ‘These were of divers bignesses,
and the biggest of them I judged to be about 25 times
bigger than a globule of one’s blood’: and if they hadn’t
sunk to the bottom, by reason of their weight, I should
have taken them for fat-particles.’

I have had several gentlewomen in my house, who
were keen on seeing the little eels in vinegar: but some
of ’em were so disgusted at the spectacle, that they vowed
they’d ne’er use vinegar again. But what if one should
tell such people in future that there are more animals
living in the scum on the teeth in a man’s mouth, than
there are men in a whole kingdom ? especially in those
who don’t ever clean their teeth, whereby such a stench
comes from the mouth of many of ’em, that you can
scarce bear to talk to them; which is called by many
people “ having a stinking breath”, though in sooth ’tis
most always a stinking mouth. For my part I judge, from
myself (howbeit I clean my mouth like I’ve already said),
that all the people living in our United Netherlands are
not as many as the living animals that I carry in my
own mouth this very day: for I noticed one of my back
teeth, up against the gum, was coated with the said matter

z.e., they had about thrice the diameter of a human red blood-corpuscle.

These were probably squamous cells—the smaller being “salivary
corpuscles ” (dead leucocytes).

2

vet-deeltgens ; 2.e., oil droplets.

244 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

for about the width of a horse-hair, where, to all appear-
ance, it had not been scoured by the salt for a few days ; *
and there were such an enormous number of living
animalcules here, that I imagined I could see a good 1000
of ’em in a quantity of this material that was no bigger
than a hundredth part of a sand-grain.’

It must be noted here that the illustrations accompanying
the foregoing letter differ slightly in each version. The
original drawings are, unfortunately, lost: and the_ best
figures—those now reproduced—are in the original Latin
edition (Arc. Nat. Det., 1695) and Opera Omnia. From the
first Dutch edition® (1684) Fig. G, a highly important
picture, was for some unexplained reason omitted altogether."
In the first Phil. Trans. version (1684) all the figures appear,
but Fig. G has an irregular and unrecognizable shape: while
in the second Phil. Trans. version (1693) Fig. G again
disappears, and the others are reversed.’

A plausible explanation of these discrepancies is the
following. The figures originally sent by Leeuwenhoek to the
Royal Society were badly drawn and poorly engraved, and he
was probably dissatisfied with them—especially with Fig. G,
which was very bad. When he was about to publish the
same pictures himself later in the same year, he resolved to
have this figure redrawn, and therefore told the engraver not
to copy the original. Then, by an oversight, the letter was
printed with the figure missing. later, discovering his
mistake, Leeuwenhoek had a new and improved drawing

’ The Latin version inserts here ‘‘ materiam illam inde exemi’’ [=so I
extracted some of this stuff], but this is not in the Dutch originals.

2 The sentences in the foregoing paragraph are loosely strung together
and ungrammatical in the original: and consequently they are not easy to
translate into intelligible English without “ improving ’’ beyond recognition.
If the reader should find my version inelegant and confused, I would refer
him to its prototype—which is much worse.

® In the only copy of the 2nd Dutch edition of L.’s works which I have
yet seen, the whole letter containing these observations (No. 39) is
missing—the copy being otherwise perfect.

* It is referred to, however, in the text (both MS. and printed Dutch
version).

’ This is obviously due to the engraver’s direct copying of the original
drawings on to his plate.

LETTER 39. INTERPRETATIONS 945

prepared, and this was inserted in the Latin translation which
appeared subsequently. The still later omission of Fig. G
from the second Phil. Trans. version was probably merely a
consequence of the great condensation which this very short
and faulty translation underwent at the hands of its editors.

Some such explanation would readily account for the
variations in the different versions. But in any case, I think,
we need not hesitate to accept the final and complete set of
drawings published with the Latin letter—drawings which
Leeuwenhoek must himself have seen and passed for press.
The omission of Fig. G from the Dutch edition was certainly
unintentional, as it is referred to in the letterpress.

It is not possible to doubt, after reading the foregoing
descriptions and inspecting the pictures, that Leeuwenhoek
discovered ‘the bacteria in the human mouth: for he described
—and described recognizably—all the most characteristic
forms occurring in this situation. To anybody familiar with
these organisms his figures speak so clearly that his words are
almost superfluous. If I were shown these sketches for the
first time, and asked to interpret them, I should be able to
say—after only a moment’s reflexion—what they probably
depict. Fig. A is a Bacillus: Fig. B shows the peculiar
organism known as “ Spirillum sputigenum” :° Fig. EK shows
some of the Micrococct commonly present in the mouth: Fig.

"IT must note that priority for this discovery has been claimed for
Hartsoeker: but this is due to a misunderstanding. The true story can
be pieced together from L.’s writings and Hartsoeker’s own words (1730).
Hartsoeker, knowing of L.’s discovery of the spermatozoa, tried to pass it
off as his own: but he says that he was ashamed to tell people that he had
examined semen with the microscope, and therefore told them at first that
the “ animalcules’’ which he had found in it were in the saliva. But he
further says, quite definitely (1730, p. 6), that he never really saw any
animalcules in saliva, and he attempts to discredit L.’s discovery. He
regarded it as an invention. Consequently, Hartsoeker himself never
claimed to have found any organisms in the human mouth, and even
denied their existence.

2 So named by Miller (1890). This organism is not really a Spirillwm
at all, but belongs to the genus Selenomonas Prowazek, 1913a. I have
studied it (in pure culture) but I have seen no accurate description of it.—
In the genus Selenomonas the flagella arise from the concave surface of the
arched or crescentic body—not from its ends, as in Spirillum. Their
lashing produces the curious whirling motion observed by L. Although the
text-books of bacteriology are usually silent on the subject, I can say from
my own knowledge that Selenomonas sputigena is very common in human
mouths—and very difficult to isolate in cultures.

946 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

F is the Leptothriz’* always found on the human teeth: and
Fig. G is unquestionably a spirochaete—probably the so-called
“ Spirochaeta buccalis”.” The figures obviously represent
bacteria, and include no protozoa; and nowhere but in the
mouth is such an assemblage of forms to be found. When
Leeuwenhoek’s own words are considered in conjunction with
these illustrations, the interpretations just advanced must
surely be self-evident to everybody who studies the microbes
of the human mouth “ with the help of a good microscope.”

Yet ever since the foregoing observations were recorded
they have been misinterpreted—and even questioned and
denied—in the most astonishing manner. It is unnecessary
to chronicle here all the wild assertions that have been made
in this connexion.’ 'T'wo of the most recent comments will
serve as illustration :

(i) Singer (1914) reproduces the figures from the Phil.
Trans. 1684 (misdated by him 1683), and says that figs. A, F,
and G [the spirochaete] are all ‘‘rod-shaped organisms ”’
[meaning bacilli?]; and that B [Selenomonas| is “a flagellated
organism” [meaning a protozoon?]|. He even recognizes
‘ sarcinae’”’ in Leeuwenhoek’s description: but the figure * so
strangely interpreted is said by Leeuwenhoek himself to
represent epidermal scales from the human skin, as seen
under a low magnification.

(ii) Wenyon (1926), discussing the Trichomonas of the
human mouth, says “it is probable that Leeuwenhoek saw
the flagellate in the tartar of his own and other people’s
teeth.”°’ Although no reference is given to the passage in

' Leptothrix buccalis Robin, 1853: Bacillus maximus buccalis Miller,
1890.
| 7 specific designation commonly ascribed to Cohn. But see Dobell
1912).

* I must mention, however, that Robin (1853, pp. 352-354) made a
careful study of the Latin versions of Letter 39, and correctly identified the
Leptothrix. Ue also recognized Fig. B as a “vibrion”’. Beijerinck (1913,
p. 10, note) wrongly supposes that Ldéffler (1887) was the first to direct
attention to L.’s pictures of bacteria in the human mouth.

* Fig. H—which occurs in the same letter, but is not reproduced here.
To my mind this figure bears no resemblance to a Sarcina or any other
bacterium : and of course no Sarcina lives normally in the mouth of man.

° Wenyon (1926), Vol. I, p. 656. So far as I am aware, there is no
passage in any of L.’s writings which can be plausibly interpreted as an
account of the Trichomonas of the human mouth.

NOTES ON LETTER 389. LETTER 75 Q47

which T'richomonas is supposed to have been described, it is
clear that Wenyon must here refer to one or other of the
“animalcules’’ which we have just discussed—but which
one, I cannot even guess. To me it is obvious that they were
all bacteria: but Wenyon takes the view that none of them
could have been, since he considers that bacteria ‘“‘ were quite
beyond the scope of the simple magnifying apparatus used by
Leeuwenhoek.” ?

Thus, while Singer finds, in Leeuwenhoek’s words and
pictures, more bacteria than Leeuwenhoek himself, Wenyon is
able to recognize none at all!

Some further researches on the ‘“animalcules” in the
human mouth were reported by Leeuwenhoek nine years
later. His letter runs as follows: ?

In my letter of the 12th* of September, 1683, I spake,
among other things, of the living creatures that are in
the white matter which lieth, or groweth, betwixt or
upon one’s front teeth or one’s grinders. Since that
time, and especially in the last two or three years, I have
examined this stuff divers times; but to my surprise, I
could discern no living creatures in it.

1 Wenyon (1926), p. 3.

2 From Letter 75. 16 September 1692. To the Royal Society.
MS.Roy.Soc. Printed in full in Brieven, Vol. II, p. 508: Opera Omnia,
Vol. II, p. 307 (1st pagination). The Dutch version first appeared in 1693
(Derde Vervolg d. Brieven), the Latin in 1695 (Arc. Nat. Det., p. 334). No
English translation was ever published in the Phil. Trans., and so far as I
am aware no English version has yet appeared in print. (Hoole did not
translate the relevant passages in this letter.) A German paraphrase—of a
fragment only—is given by Léftler (1887, p. 6), who misdates the epistle
October 1.—The printed Dutch version follows the original MS. so closely
that few annotations are necessary : while the Latin version in Opera Omnia
(ed. noviss., 1722)—by an unknown hand—is one of the best translations I
have ever read. Barring a few trivial misprints, it renders its Dutch
prototype with wonderful faithfulness.—The originals of the illustrations
are lost ; the MS. in the Roy.Soc. collection being accompanied by a proof
of the engraved plate sent by L. himself in place of the original sketches.

* As noted already (p. 237, note 2), the correct date of this letter—
as written by L. himself on the MS.—is not the 12th but the 17th of
September.

248

LEEUWENHOEK AND HIS “ LITTLE ANIMALS”

Being unable to satisfy myself about this, I made up
my mind to put my back into the job, and to look into
the question as carefully as I could. But because I keep
my teeth uncommon clean, rubbing them with salt every
morning, and after meals generally picking them with a
fowl’s quill, or pen; I therefore found very little of the said
stuff stuck on the outside of my front teeth: and in what
I got out from between them, I could find nothing with
life in it. Thereupon I took a little of the stuff that was
on my frontmost grinders; but though I had two or
three shots at these observations, ’twas not till the third
attempt that I saw one or two live animalcules. Yet I
could well make out some particles lying about that I
felt sure must have been animalcules. This put me in a
quandary again, seeing that at and about the time when
I wrote to you concerning these animalcules, I never
failed to see there was life in them: but though now I
used just the very same magnifying-glass and apparatus
(which I judged to be that best suited to the purpose),
yet I couldn’t make out any living creatures at all.

Having allowed my speculations to run on this subject
for some time, methinks I have now got to the bottom
of the dying-off of these animalcules. The reason is, I
mostly or pretty near always of a morning drink coffee,
as hot as I can, so hot that it puts me into a sweat:
beyond this I seldom drink anything save at mealtimes
in the middle of the day and in the evening; and by
doing so, I find myself in the best of health. Now the
animalcules that are in the white matter on the front-
teeth, and on the foremost of the back-teeth, being unable
to bear the hotness of the coffee, are thereby killed: like
I’ve often shown that the animalcules which are in water
are made to die by a slight heating.

Accordingly, I took (with the help of a magnifying
mirror) the stuff from off and from between the teeth
further back in my mouth, where the heat of the coffee
couldn’t get at it. This stuff I mixt with a little spit
out of my mouth (in which there were no air-bubbles),

LETTER 75. 16 SEPTEMBER 1692 249

and I did all this in the way I’ve always done: and then
I saw, with as great a wonderment as ever before, an
unconceivably great number of little animalcules, and
in so unbelievably small a quantity of the foresaid stuff,
that those who didn’t see it with their own eyes could
scarce credit it. These animalcules, or most all of them,
moved so nimbly among one another, that the whole stuff
seemed alive and a-moving.

I again paid the strictest attention I possibly could to
the bigness, or at any rate to the length, of the bodies of
many of ’em'; but mostly to the little animalcules, which
looked to me roundish. Afterwards, I took a grain of
coarse sand (of the sort of sand that we use here in this
country* for scouring the pewter, and other household
chattels), and I stuck this sand-grain in front of the
microscope through which I had seen the animalcules :
and I am bound to say, after making careful measure-
ments, which I did by eye, that the diameter of the sand-
grain was above a thousand times longer than the diameter
of one of the little animalcules which I saw in great
numbers. Consequently, then, such a grain of sand was
far more than a thousand millionfold bigger than one of
the little creatures aforesaid.

Besides, I also saw divers animalcules * whose bodies
were a bit thicker than the little animals hereinbefore
spoken of; but these were quite 5 or 6 times longer than
they were thick, and therewithal their body was of equal
thickness all along, so that I couldn’t make out which
was their head, or which their tail end; all the more
because when they were a-swimming, which they did
very leisurely (and this was their only motion, with a
little bending of the body now and then, as it seemed to
me), they would go ahead first with one end of the body

a

1 de hoe grootheijt of de lengte van veele haar lighamen MS. . . . of
wel de lengte van veele haar ’er lighamen Dutch printed version.

2 alwaar hier te lande MS. waar mede hier te lande printed version.
* Obviously bacilli of some sort, but otherwise unidentifiable.

250

LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

in front, and anon with the other.t’ These animalcules,
as they appeared to me, I have shown in Fig. A. [See
Text-fig. 4.]

And I saw, too, sundry animalcules”’ that had very
near the same length, and also some a bit longer. These
moved their bodies in great bends, in comparison of the
first animalcules, and made with their bendings so swift
a motion, in swimming first forwards and then backwards,
and particularly with rolling round on their long axis,
that I couldn’t but behold them again with great wonder

i as 3 B

ee ig

\ ~—

=a —
Sis Cc fy.
———" Se
a a

[Text-Fia. 4]

and delight: the more so because I hadn't been able to
find them for several years, as I’ve already said. For I
saw not alone the nimble motion of their own body; but
the little animalcules too, which swam in great plenty
round about these animalcules, were shoved off or driven
away from them, just as if you imagined you saw a
butterfly or moth flitting among a swarm of gnats, so
that the gnats were all wafted away by the butterfly’s
wings. ‘These animalcules I have represented in Fig. B.

1 This very acute observation was made on other bacteria, of course, at
a much earlier date—as already noted. It furnishes conclusive proof that
the organisms observed were bacteria.

2 From the following account these were evidently spirochaetes again:
but the figures are very poor, and could hardly be identified without L.’s
description of the organisms themselves.

BUCCAL BACTERIA REDESCRIBED 251

Furthermore, I saw animalcules* that were of very
near the same thickness, but of singular length. These
had so little” motion that I had most times to confess
they might not be living creatures at all; yet when I
could keep my eye on them, without getting tired, I
could make out that they bent their body very slow, just
bending it into a very faint curve, so that they didn’t
move forward, or very little. ‘These animalcules, as they
looked to me, are shown in Fig. C.

Now I also saw yet other animalcules,* that were of
very nigh the same thickness, but which in length even
surpassed those last described. But you seldom saw two
of this sort alongside, or floating off in the wet stuff, that
were of one and the same length. ‘These animalcules * too
were ’ in great numbers, whereof some were straight, while
others had a kink in them, as shown in Fig. D. But
the longer these animals were, the less motion or lfe
could I discern in them: and notwithstanding I could
make out no life in ’em, yet I made sure they were living
creatures, or had been such when they were in the mouth,
and situated on the back teeth, where many are
generated.

But we must be still more amazed when we consider
how these animalcules can move, and shift ’emselves
about, in stuff as thick as this is when it is lodged upon
and betwixt the teeth; and how hard and slow it must
be for them to get about in such stuff. But when, on
the other hand, the said stuff is mixed up with spittle,
and by this mixing the animalcules find themselves in a
fluid material, many of them feel released, as it were, and
never stop moving, so far as the eye can see.

-

? Leptothria.
seer weignig MS. soo weynig printed version.

N

* Leptothrix—almost certainly.

* Dierkens MS. omitted from printed letter.

sijn MS. and printed version: apparently a mistake for waren. The
Latin version has erant, and I make the same correction.

oa

252 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS”

It must be confessed that the foregoing observations add
little to those made previously. But bacilli, spirochaetes, and
Leptothrix are again recognizably described—if not recogniz-
ably figured: and this letter therefore confirms, to some
extent, the earlier one (No. 39). It also gives us a characteristic
glimpse of the author and his methods, and for that reason—
if for no other—deserves notice.

Various writers have already reproduced the illustrations
accompanying this letter, but nobody hitherto appears to have
made any attempt to interpret them—apart from noting that
they represent “ bacteria”. This is to be explained, I think,
in the usual way : most people merely glance at Leeuwenhoek’s
figures and do not take the trouble to read his words relating
to them, so that his excellent observations have been all too
often misunderstood or treated as mere curiosities.’

A few further observations on the bacteria about the teeth
were interpolated in a letter written to the Royal Society
five years later. In the midst of a discussion of the eggs of
snails, the germination of wheat, and the spat of oysters, we
find the following digression :”

I can't forbear to tell you also,’ most noble Sirs, that
one of the back teeth in my mouth got loose again, and
bothered me much in eating: so I decided to press it
hard on the side with my thumb, with the idea of making
the roots start out of the gum, so as to get rid of the

Tn passing, I may also add that a recent writer (Prescott, 1930) cites
the foregoing letter (No. 75) as evidence that “ A. von Leeuwenhoek ”’ held
the view “that microscopic organisms were produced spontaneously from
non-living matter.” It is difficult to conceive how anybody who has ever
read a word of L.’s writings could make such a mistake: but perhaps
Prescott—like many another writer who quotes L.—did not consult the
work to which he refers. This would also explain the singular fact that he
cites the original Latin edition of the letter (1695) but gives the pagination
of the editio novissima (1722).

2 From Letter 110. 10 September 1697. To the Royal Society.
MS.Roy.Soc. Printed in Brieven, Vol. III (Sevende Vervolg, 1702); Opera
Omnia, Vol. III (Epist. Soc. Reg., 1719); and in abbreviated English in
Phil. Trans. (1697), Vol. XIX, No. 235, p. 790. The passage here
translated begins on p.40 of the Dutch edition, p.35 of the Latin, and
p. 797 of the Phil. Trans.

° ook printed version: not in MS.

LETTER 110. 10 SEPTEMBER 1697 253

tooth ; which I succeeded in doing, for the tooth was
left hanging to only a small bit of flesh, and I was able
to snip it off very easily.

The crown of this tooth was nearly all decayed, while
its roots consisted of two branches ; so that the very roots
were uncommon hollow,’ and the holes in them were
stuffed with a soft matter.

I took this stuff out of the hollows in the roots, and
mixed it with clean rain-water, and set it before the
magnifying-glass so as to see if there were as many living
creatures in it as I had aforetime discovered in such
material: and I must confess that the whole stuff seemed
to me to be alive. But notwithstanding the number of
these animalcules was so extraordinarily great (though
they were so little withal, that ’twould take a thousand
million of some of ’em to make up the bulk of a coarse
sand-grain, and though several thousands were a-swim-
ming in a quantity of water that was no bigger than a
coarse sand-grain is), yet their number appeared even
greater than it really was: because the animalcules, with
their strong swimming through the water, put many little
particles which had no life in them into a like motion,
so that many people might well have taken these particles
for living creatures too.

These were Leeuwenhoek’s last recorded observations on
the bacteria of the mouth, but there is another reference to
bacteria which he saw in a decoction of the “fur” off his own
tongue some years later. Although these were obviously
putrefactive organisms, and not species proper to the human

1 The original words are 200 dat selfs de Wortels boven gemeen hol waren.
The Latin translator apparently took this to mean that the wpper parts of
the roots were hollowed out (as is very probable, of course), for he renders
these words “ superior wtriusque radicis pars admodum erat excavata”’: but
boven gemeen is a common expression with L., and always means
“unusually” or “out of the common run of experience.” In the Phil.
Trans. the words “boven gemeen hol” are absurdly mistranslated
“extraordinary whole ”’

2 de groote van een grof zand printed letter . . . geen grof zand MS.

254 LEEUWENHOEK AND HIS “LITTLE ANIMALS ”’

mouth, I shall quote his words here—as they are not wholly
irrelevant in the present context. In an interesting letter
written in June, 1708, he said:?

At the latter end of the month of April, 1708, I was
again seized with a high fever, which stayed with me for
four days, rising higher each night; and as my tongue
was again coated with a thick whitish matter, I oft-times
removed some of it, which seemed stuck very tight
to the parts of the tongue, with a small penknife or with a
silver tongue-scraper: and viewing it many times through
the magnifying-glass, I could see nought else but what I
have described * in my previous dicconenee

On two occasions, I took some of the foresaid stuf from
my tongue, and put it in a small clean China coffee-cup,’
and then poured boiling rain-water upon it, and let
it seethe a good half hour; with the idea of separating the
glue-like matter (wherewith the particles seemed to be
stuck to one another) by so doing, in order that I should
the better be able to view the parts themselves.

Now when the stuff which I had taken off my tongue
had lain in the water, in which it was boiled, for about
a fortnight,’ I saw that the water was well-nigh evaporated
away; so I poured again a little rain-water, which had
stood some days in a clean phial in my closet,’ into the
boiled water aforesaid. And five or six days afterwards,

1 Brom Letter dated 29 June 1708. To the Royal Society. MS.Roy.Soc.
Not published in Dutch or Latin editions. English translation (incomplete)
printed in Phil. Trans. (1708), Vol. XXVI, No. 318, pp. 210-214. I
translate from the MS. in L.’s own hand.

2 A reference to a letter dated 18 Oct. 1707. MS.Roy.Soc. Incomplete
English translation in Phil. Trans. (1707), Vol. XXV, No. 312, p. 2456
[misprinted 1456]. Not published in Dutch or Latin.

® een schoon jndiaanse Coffe Copje MS. ‘‘a clean China Coffee-dish ”’
Phil. Trans.

* ontrent veertien dagen MS. “above a Fortnight”? Phil.Trans.

> op mijn Comptoir MS. “upon my Desk near the said boil’d Water ”
Phil. Trans. Cf. p. 114 supra.

LETTER OF 29 JUNE 1708 255

I brought a thin glass tube suddenly with its one open
end over the bottom of the porcelain cup, where most of the
particles that had come off the tongue lay all of a heap; ’
with the idea that when the water entered the tube, a few
particles from the tongue would also be carried upwards
into the tube, so that I should thus again be enabled to
view the particles off the tongue: in doing which,’ I saw
an inconceivable number of exceeding small animalcules,
and these of divers sorts. But far the greatest number
was of one and the same bigness, yet this was so little
that they could not be discerned but by great attention,
through a very good magnifying-glass ; and most of these
animalcules were abiding* where the said matter from
the tongue lay, and I took into consideration whether the
sald creatures might not indeed be getting their food from
the particles of the tongue. And when these animalcules
had been in the glass tube for about two hours, I perceived
that a great many of ’em were dead.

1 over hoop lagen MS. In the Phil. Trans. the translator transferred

the adverb to the glass tube, making L. say that he “ hastily turned it
upside down [my italics] into the bottom of the China Cup.”

2 in welk doen MS. ‘and it happen’d as I wished” Phil. Trans.

* haar . . . waren onthoudende MS. “ rendezvous’d ” Phil. Trans.—
a good translation, but not a word that L. would have used.

256

CHAPTER 4

THE LATER OBSERVATIONS ON FREE-LIVING
PROTOZOA

(LETTERS 122, 125, 144, 147, 149, 150, VII, X XIX)

Leeuwenhoek in his’ multifarious protistological

wanderings during the last quarter of the X VII Century.
We have yet to consider his equally remarkable excursions
into similar unexplored fields at a later date.

At the turn of the century—when he was already an old
man, nearing his 70th birthday—he was still, despite his age,
at the height of his powers; and during the next few years—
between 1700 and 1716—he recorded some of his most
interesting protozoological discoveries. These observations
were all made on free-living forms found in water.

In a letter written at the very beginning of 1700,
Leeuwenhoek gave the first description and picture of
Volvoz. The letter’ begins with an account of other observa-
tions, and describes inter alia some gnat-larvae which he had
found in ditch-water.? It then proceeds :

Ie the three preceding chapters we have followed

IT had got the foresaid water taken out of the ditches
and runnels on the 30th of August:* and on coming

1 Letter 122. 2 January 1700. To Sir Hans Sloane. MS.Roy.Soe.
Published [Dutch] in Brieven, III, 152 (2nd pagination), Sevende Vervolg
(1702): [Latin] in Opera Omnia (Epist. Soc. Reg.), III, 146 (1719) : English
translation in Phil. Trans. (1700), Vol. XXII, No. 261, p. 509.—Curiously
enough, Vandevelde entirely overlooks the fact that this letter contains the
first description of Volvoz.

2 These observations are also remarkable: for they show that L. had
noticed the difference in posture of Anopheline and Culicine larvae in the
water—a peculiarity now well known, but generally supposed to have been
discovered by recent malariologists.

* Anno 1698, as appears from the earlier part of the letter.

LETTER 122. 2 sanuaRy 1700 257

home, while I was busy looking at the multifarious very
little animalcules a-swimming in this water, I saw floating
in it, and seeming to move of themselves, a great many
green ' round particles, of the bigness of sand-grains.

When I brought these little bodies before the micro-
scope, I saw that they were not simply round, but that
their outermost membrane was everywhere beset with
many little projecting particles,” which seemed to me to
be triangular, with the end tapering to a point: and it
looked to me as if, in the whole circumference of that
little ball, eighty such particles were set, all orderly
arranged and at equal distances from one another; so
that upon so small a body there did stand a full two
thousand of the said projecting particles.

This was for me a pleasant sight, because the little
bodies aforesaid, how oft soever I looked upon them,
never lay still; and because too their progression was
brought about by a rolling motion; and all the more
because I imagined at first that they were animalcules.
And the smaller these little bodies were, the greener in
colour they appeared to me: whereas contrariwise, in
the biggest (that were as big as a coarse grain of sand)
no green colour could be made out in their * outermost
part.

Each of these little bodies had inclosed within it 5, 6, 7,
nay, some even 12, very little round slobules,* in structure
like to the body itself wherein they were contained.

While I was keeping watch, for a good time, on one of
the biggest round bodies, among the others, in a little
water, I noticed that in its outermost part an opening

' groene ronde deeltjens MS. ronde deeltjens Dutch printed version
“reat round particles” Phil. Trans. Groene (green) is very important ;
and “great” is an obvious mistranslation or misprint. The Latin version
also omits “‘ green ’’—calling them simply particulae rotundae.

2 ¢e., the individual flagellates composing the colony.

* het MS. haar printed version.

* i.e., the daughter-colonies.

Li

258 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”?

appeared, out of which one of the inclosed round
globules, having a fine green colour, dropt out, and took
on the same motion in the water as the body out of
which it came. Afterwards, the first round body ' remained
lying without any motion: and soon after a second
globule, and presently a third, dropt out of it; and so
one after another till they were all out, and each took on
its proper motion.”

After the lapse of several days, the first round body
became, as it were, again mingled* with the water; for I
could perceive no sign of it.

What also seemed strange to me, was that I* could
never remark, in all the motions that I had observed in
the first round body,’ that the contained particles ° shifted
their positions; since they never came in contact, but
remained lying separate from one another, and orderly
arranged withal.

Many people, seeing these bodies a-moving in the water,
might well swear that they were little living animals; and
more especially when you saw them going round first one
way, and then t’other.

Now when a great many of the said round bodies were
in a bottle along with many little living animals, I saw
that after the space of three days they were all gone,
inasmuch as I could then make out none of the said
bodies in the bottle.

Moreover, I had put a few drops of water (as shown
at CD [Plate XXVI1]) in a glass tube (Fig. 1, AB) about

1 j.e., the mother-colony.

2 en yder een beweginge aannam. These words are in the printed version

but not in the MS., and were probably added in the proof as an afterthought.

* <.e., the mother-colony broke up. The word is vereenigt [=united] in
the MS., but was changed to vermengt [=mixed ] in the printed version.

* The word ik—which is necessary for the sense of this passage—is here
present in the MS. but omitted in the printed version.

° 4,e., the mother-colony.
* «.e., the individual flagellates composing the colony.

7b) J ad { i ‘ ; a iat
; 4% i t :
1 as ‘
1 She
. ey

ee i

Hee ee i ea, RN ah ty
Reh ve Ree: fe ae

4 hata?
Ps Po0%1s$ o hie Sarr =) an Py a

ee TEE Mh hi.’ j
han A * Fog "1 AP
= ‘ ) ae
i O eat) 7 cat , ‘
‘ ; i rs a f K jae

-

‘ , - ‘| Mi ste “A
: Ne 2
¢ uk ee PY. 4
s F ; } mes |
,
a
oa F
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CN), SN alla eb eae we aie a iy Wh

7

i vey at D } Ane ven |

aren eh |

TONG a
Moly is ae ns

ody, 1 ine oie me oy ny y ba } Bras ie ve
7 ee ae wae i] Bae - '
Gr . ee

XXVI

PLATE

‘UOI4ZIpS Yoon, oy} surAuBdMIODNv SSUIABISUO BYy WOAT

(OOLT “URE Z
‘GGL ON) vodjo4, NO UALLAT SMAOHNAMNAAT OL SNOILVULSOATII

259

9

facing p.

DISCOVERY OF VOLVOX 259

eight inches long, and of the thickness of the quill of a
hen’s feather." One end (A) I left open, the other end (B)
I plugged with a bit of cork (so that betwixt D and B
there was nothing but air), with the idea that” when I
came to handle the tube, the water wouldn’t run out of it.
The air being now shut up in the tube, between D and B,
cannot remain of the same volume, or extent, but changes
at every moment, so to speak; for one can’t approach the
tube with the hand, the breath, or any part of the body
that is a little warmer than the air wherein the tube is
lying, without the air in the tube being affected by some
part of it; and this warmth brings about an expansion
or greater enlargement of the air (in the tube), whereby
the water is made to move, being driven from DC towards
A: notwithstanding we may perceive no motion in it
with our naked eye. And just as the least warmth
causes this outward displacement of the air in the glass
tube, so likewise warmth readily departs from the tube,
whereupon a movement of the water takes place* back
from C towards B.

In this water were included two of the foresaid round
bodies,’ and these of the biggest sort; and contained in
each of them were five little round particles,? which
inclosed particles were pretty well grown in size: and in
a third big body there lay seven round lesser particles.
These last were uncommon small.

After the lapse of four days, the said round bodies
remaining shut up in the glass tube all this while, I
perceived that in two of them the outermost membrane

1 een schagt van een hoender [MS. honder] penne Dutch edition “of a
Goose Quill” Phil. Trans.

2 dat is here accidentally omitted in the MS., but restored in the printed
version.

3

aan neemt MS. is nemende printed version.

* j.e., mother-colonies.

° i.e., daughter-colonies.

260

LEEUWENHOEK AND HIS “ LITTLE ANIMALS”

(which was become exceeding thin and clear) was * burst
asunder; and that the ten particles, that were contained
within the two big bodies, were moving about in the
water, rolling first one way and then the other.

Furthermore I perceived,’ after the space of five days,
that the small particles inclosed in the third large body
were not only grown in bigness, but I could also then
discern that from inside these small particles other lesser
round particles* were to come forth. After the lapse of
five days more, this third round body was also a bit burst
open, and its contained particles were also come out of it:
but notwithstanding it was open on one side, it kept on
going round in the water, and that as quick as it had
done heretofore.

Some days afterwards, I could make out nought but
some little bits whereof the bigger bodies had been
composed ; and soon after, these too went out of sight.

Without a break I continued from day to day to watch
these little particles that had issued from the bigger
ones; and I always saw that they not only waxed in
bigness, but that the particles contained within them got
bigger too.

At the end of September,’ I perceived that the con-
tained particles were not so regularly round as the bigger
bodies wherein they were inclosed, and therewithal that
some of them were broke apieces ; and that the last particles
that were come out of the big ones seemed not to be round,
and lay without motion against the glass.’

1 waren MS.—corrected to was in printed version.

2 dat (redundant) stands here in the MS., but has been removed in the
printed version.

* j.e., daughter-colonies within the daughter- colonies. This acute
observation gave great support to the doctrine of the “ preformationists ”’ at
a later epoch, though it was then usually accredited to Spallanzani—who
merely repeated and confirmed L.’s observations.

* Anno 1698.

> The whole of the foregoing sentence is inexplicably omitted from the
Latin version.

REPRODUCTION OF VOLVOX 261

Now these last bigger bodies, when they had unbur-
dened themselves of their contained particles, or when
they broke asunder, were quite four times less than those
wherefrom they issued: wherefore we may conclude that
they had not reached their full growth, or gotten their
right food.

We have also noted that the said round bodies agree
in their weight with water.’ This being so, they may be
set in motion in the water with the least movement that
it recelveth from the air.

I thought fit to have one such body pictured, with its
contained particles; as shown’ in Fig. 2,at EF. In this
body, the inclosed round particles (which had so waxed in
bigness that they were ready to be cast out) did not lie in
such recular order as they did in those before described ;
and as in this one there was not so continuous a motion,
I imagine that this was simply due to the contained
particles not all lying at an equal distance from the centre,
so that the round body was heaviest on the side where the
particle furthest from the centre was placed, whence its
motion was somewhat hindered.

For what purpose these round bodies are created we
know not. But as I observed that the various round
bodies, when mixt with a great many little animals* in
the big bottle, were all vanished in the space of three
days, I did well ponder whether they were not created to
serve as food for such little animals.

Now as we see that the oft-mentioned round bodies
come into being not of themselves,* but by generation, as
we know all plants and seeds do (inasmuch as every seed,

1 i¢., have the same “specific gravity’? as water. This term was

unknown, of course, to L., though the concept was familiar; and I
therefore render his words literally and not too “ scientifically”.

spontaneous generation ’’.

2 See Plate XXVI.

L. here means mosquito-larvae, crustacea, ete., —not protozoa.

. ee . oe
* niet wijt haar selven—meaning “not spontaneously”, or not by

262 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”

be it never so small, is as it were endowed with its
inclosed plant‘); so can we now be more assured than we
ever before were heretofore * concerning the generation of
all things. For my part, I am fully persuaded that the
little round bodies, which are found in the bigger ones,
serve as seeds; and that without them these big round
bodies couldn’t be produced.°

In the summer I divers times applied myself to the
study of the waters lying around our town, the last
occasion being on the 8th of October 1699: but I could
satisfy myself no further in this matter.

The remainder of this letter contains no other observations
on Protozoa: and the next reference to any of these organisms
occurs some five months later, when Leeuwenhoek very briefly
mentions and depicts the shell of a Foraminiferan, which he
had found in the stomach of ashrimp. He did not, of course,
know that it was the shell of a protozoon: but as this is the
only mention—so far as I am aware—of any Rhizopod in the
whole of his writings, I will quote the passage. After
discussing the anatomy of the shrimp, he describes what he
had found in shrimps’ stomachs, and adds:

In some of their stomachs I also discovered very little
snail-shells, which, because of their roundness, I called

1 Demonstrated by L. elsewhere.
2 te vooren . . . tot nog toe—redundant in the original.

* The foregoing description of Volvox, though perfectly intelligible in the
original, is somewhat obscured by the circumstance that L. uses the same
word (deeltjens=particles) throughout to denote the mother-colonies, the
daughter-colonies, and the individual flagellates. To make his meaning
plain I have therefore substituted “ body”’, " bigger particle ’ ’, ete., for

‘particle”’, where it is necessary to distinguish the “ particles’’ of different
categories. The Latin translator took a like liberty with his original, and
rendered deeltjens by particulae rotundae, particulae majusculae, particulae
minores, etc., aS occasion required.

“ From Letter 125. 2 June 1700. To Frederik Adriaan, Baron van
Rhede: [Dutch] in Brieven, Tde pete p. 196 (1702) ; atoll in Opera
Omnia (Epist. Soc. Reg.), II, p. 186 (1719). No MS., and not in Pail.
Trans. The Latin translation is wrongly dated January 2 (postridie Kal.
Jan. 1700). An English version of the letter will be found in Hoole (1807),
Vol. II, p. 266—the passage cited being on pp. 271-2.

PLATE XXVII

TWO OF LEEUWENHOEK’S FIGURES ILLUSTRATING LETTERS 125 AND 144
Enlarged from the original engravings.

Fig. 7, ABC.—Shell of a Foraminiferan (Polystomella ?).
Fig. 3, PQ.—The Ciliate Coleps. (The original measures only 6 mm. in length.)

facing p. 263

LETTER 125. POLYSTOMELLA 263

little cockles;* and these little shells were no bigger
than a coarse sand-grain.

In order to exhibit the pretty structure of these little
shells before the eye, I thought ’twould not be amiss to
set a drawing made of one of them. Fig. 7, ABC
[Plate XX VII] shows one of these little cockles, which
I took out of the stomach of a shrimp.

It has been generally agreed that the shell here referred
to was that of a Foraminiferan, but different writers have
interpreted its species variously. For my part, I feel fairly
confident that the picture represents a Polystomella.’

Leeuwenhoek’s next contribution to protozoology is
imbedded in a _ well-known letter dealing chiefly with
Rotifers: and the protozoological elements in this epistle
have, it seems to me, been hitherto largely ignored or mis-
understood. Too my mind there can be little doubt that he
here left us an unambiguous record of his discovery of three
different Protozoa—two Phytoflagellates (Haematococcus and
Chlamydomonas) and a Ciliate (Coleps). But I will leave
him to speak for himself: °

On the 25th of August,’ I saw that in a leaden gutter,’
on the front of my house, for a length of about five feet

1 ven slakhoorntje. Hoole translates “snails”, but Sewel (1708) says

the word denotes ‘a Cockle-shell’’; and from L.’s allusion to their
roundness, I take this to be correct. The Latin translator called them
limaces cochleares.

2 Cole (1926, p. 13) takes the same view; but Miall (1912, p. 216)
identifies the organism as Nonionina. Robert Hooke (1665, Obs. XI, p. 80;
Scheme V, Fig. X) had previously described and figured a foraminiferan
shell—probably Rotalia—which he had discovered in sand: but to L. his
observation was apparently unknown.

* Letter 144. 9 Feb. 1702. To Hendrik van Bleyswyk. Brieven (7de
Vervolg), III, 400; Op. Omn. (Epist. Soc. Reg.), III, 380. No MS. and not
in Phil. Trans. Partially translated into English by Hoole (1807), IJ,
207.—Vandevelde says this letter is a “ Beschrijving van waterdiertjes,
wellicht infusorién”’: but neither he nor anybody else appears to have
sorted out the various “Infusoria’’ described, though Biitschli (Vol. II,
p. 621) recognized Haematococcus.

* Presumably anno 1701.
> John Ray (in 1663) notes as a curiosity that in Holland “the Rain

ce

264 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

and a breadth of seven inches, some rain-water had
remained standing, which had a red colour; and as it
occurred to me that this redness might well be caused by
red animalcules (as I had indeed seen come about in
muddy ditches), I took a drop or so of this water and
looked at it through the microscope; and I discovered a
creat many animalcules* that were red, and others that
were green, whereof the biggest looked no bigger through
the microscope than coarse sand doth to your naked eye,
and others smaller and smaller, each after its kind.

These animalcules were for the most part round, and
the green ones were somewhat yellowish in the middle of
their bodies.

Their bodies seemed to be composed of particles that
presented an oval figure; and therewithal they had short
thin instruments which stuck out a little way from the
round contour, and wherewith they performed the motions
of rolling round and going forward ;* and when they took a
rest, and fixed themselves to the glass, they looked like a
pear with a short stalk; but this stalk,’ on curious examina-
tion, was split at the end, or divided into two, and ’twas
with these two parts that the animalcules fixed ’emselves
fast to the glass.”

that falls upon the Houses is by Pipes and Gutters conveyed into a Cistern,
and there reserved for the uses of the House, as at Venice in Italy.” It
would appear, therefore, that gutters were not commonly installed on
English houses at that date. (See Ray, 1673; p. 53.)

1 The description which follows obviously refers to the Phytoflagellate
Haematococcus pluvialis (=Sphaerella lacustris), which is very commonly
found in gutters. This is the first account of this organism. The smaller
green ones were probably, for the most part, Chlamydomonas—equally
common in this situation: vide infra.

2 waar medeze een omwentelende beweginge en voortgang te weeg bragten:
“by means of which they caused a kind of circular motion and current in
the water’—Hoole. This mistranslation entirely spoils the sense of this
important passage describing the action of the flagella.

® Hoole here interpolates “or rather this tail’—which is not in the
original, and shows that he did not understand what L. was talking about.

* This is a remarkably good observation of the locomotory organs of
Haematococcus, which possesses two anterior flagella that often adhere to
one another for a variable length at their proximal ends.

LETTER 144. 9 FEBRUARY 1702 265

The smallest animalcules of this sort I judged to have
been begotten of the bigger ones.

I did also see yet another kind of animalcules, that
were much smaller.’ These were very clear in the body ;
but I judged that there must have been quite a hundred
of the former sort to every one of the latter.

On the 31st of August, the water was so far dried up
(owing to the great heat, which had continued for three
days running), that if I pressed my finger on the dirt”
lying on the lead, little more than a drop of water as big
as a sandgrain stuck to it: and though I could discern a
few living animalcules, which were transparent, in this
water, yet all the green and red ones were dead.

On the Ist of September, the stuff in the leaden gutter
was become so thick, that it was like stiff wet clay; and
notwithstanding all my efforts, I could discover no living
creatures in it of the sort that I had seen before.

At this point Leeuwenhoek leaves Haematococcus and goes
on to describe the Rotifers which he also discovered in his
leaden gutter; but in the course of his description he
accurately notes that:

The stuff in the guts of these little animals ° was most
always red, proceeding (as I imagined) from the red
animalcules* which they use as food: but I also saw
afterwards a few of these little animals which hadn’t
any of the red stuff inside them, particularly the young
ones which had not long left their mother’s body.

Here follow further observations on Rotifers—including
the famous experiment in which Leeuwenhoek found that

1 Possibly bacteria, but obviously unidentifiable from this slight
description.

2 A little later (4 Nov. 1704) L. says—in the words of a contemporary
English translator (MS.Roy.Soc.)—* I don’t suffer such foul stuf to lye long
in my gutter, but twice a year cause the lead to be scowered so clean that
it looks just like new’”’.

* t.e., Rotifers.

4:
2.€., Haematococcus.

266 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”
they can “‘return to life” after desiccation. Whilst relating
his experiences, however, he mentions an organism which is
almost certainly identifiable—from the figure which he
fortunately gives—as the ciliate Coleps. He says:?

Now divers little animalcules came before the draughts-
man’s eye, whose structure was very like what is shown
in [Plate XX VII] Fig. 3,’ between P and Q, whose belly
was flat, and from which little instruments stuck out,
wherewith it effected its progress. And as this animal-
cule had little round globules in its body, so there were
yet many other little animals * a-swimming in the water,
whose whole body seemed no bigger, under the micro-
scope, than one of these globules in the bigger sort just
spoken of.*

I have divers times so placed the said animalcules’ out
of water, that they were encompassed by an amount of
water not so big as a sand-grain; in order to see whether
these little creatures, when all the water round them was
evaporated away, and they were lying in nothing but air,
would burst asunder, as I had made certain of in other
animalcules:° and I saw that whenas the water was

1 Brieven, III, p. 407: Op. Oman. III, p. 387.

* In the figure as copied by Hoole (II, Pl. XVI, fig. 35) the resemblance
to Coleps is largely lost. The original—though very small—shows quite
clearly the characteristic barrel-like form (with one side somewhat flattened)
of this organism. The expanded anterior end (bearing the terminal mouth),
the caudal spines, and even the four girdles of armour-plates, are all clearly
indicated. Biitschli noted the resemblance to Coleps, but considered the
identification as doubtful. To me it appears certain.

* Possibly bacteria—or perhaps flagellates.

“ These two sentences are very clumsily constructed in the original—
though their meaning is clear enough—and I have not attempted to improve
them.

* de verhaalde dierkens. It is not absolutely certain that this expression
means the organisms just mentioned : it possibly refers to the Rotifers. If
it really refers to the Protozoa, then the ensuing words confirm the view
that L. was here describing Coleps; for this ciliate has a cuirass composed
of numerous interlocking platelets, which prevent its bursting when dried.

° Cf. Letter 18, p. 120 supra.

COLEPS. GUTTER-WATER 267

almost exhaled, and the animalcule could no longer turn
and twist itself about in it, it took on an oval figure, and
stayed lying thus, without my being able to see that the
moisture evaporated away out of the creature’s body, for
it kept its oval figure.

At this point Leeuwenhoek returns to his experiments with
the Rotifers: but in the account of their revivification after
drying he notes that he

also saw two several sorts of little animalcules
a-swimming through the water, whereof the least were so
little, that many thousands together would not equal a
coarse grain of sand in bigness.’

After some further remarks on Rotifers he then says:

Once more we see here the unconceivable Providence,
perfection, and order, bestowed by the Lord Creator of
the Universe upon such little creatures which escape our
bare eye, in order that their kind shouldn’t die out.

From these discoveries we can well understand that in
all falling rain, carried from gutters into water-butts,
animalcules are to be found; and that in all kinds of
water, standing in the open air, animalcules can turn up.
For these animalcules can be carried over by the wind,
along with the bits of dust floating in the air: and on the
other hand, animalcules which are a hundred million
times and more smaller than a coarse grain of sand, can
be borne aloft, along with the water particles, albeit not
as high as the clouds, but at least a little way up; and
then when the sun goes down, they fall to earth in what
we call dew; and they may well be taken up too and
carried along by the wind. This is the more probable,
since we know that in a storm the sea is so lashed on the
shore by the wind, that drops of sea-water are found on
trees, running down their trunks, and still salty, more

than half-an-hour’s journey from the coast. This salt

" Lit. cit., Brieven III, p. 409. These were evidently not Rotifers but
Protozoa or Bacteria.

268 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS”

water is judged by the vulgar (though mistakenly) to be
the salt evaporated by heat from the sea.’

On the said* 4th of September, it rained a little while
at eventide; yet so much fell, that in the leaden gutter
aforesaid there was some water on the 5th and 6th of
September: and this water I examined on both days,
and discovered, in every drop that I took from the gutter,
eight or ten of the animalcules described, though I could
not discern a single one of the round green or red creatures
that was alive.

On the 6th of September, I put up seven glass tubes, in
which I placed some of the dry stuff aforesaid out of the
leaden gutter; pouring into some of them boiled, and
into others unboiled rain-water.2... On the 7th of
September I viewed the said glass tubes, and beheld with
wonder in one of them an inconceivably great number of
little green animalcules,* all alive, all of which seemed
round, as before described, and a-moving among one
another ; nay, I saw so many that the very water seemed
to the naked eye to have a faint green colour: but how
curiously soever I examined the other glass tubes, I could
find no living green animalcules in them... .°

On the 9th of September it rained a little; and two or
three days later it rained so much, that on the 14th of
September there was water to the depth of about a finger’s
breadth in the leaden gutter. Of this water I took
about two drops; and examining it, I saw a great many
of the little round animalcules previously made mention

* dat door de warme wytwaseminge van de Zee werd voortgebragt. These
words were omitted by Hoole—also most of what follows.

2 Mentioned earlier, in connexion with Rotifers, in a paragraph not here
translated. Apparently anno 1701.

* I here omit two lines referring to Rotifers.

* There can hardly be any doubt that these organisms were Chlamy-
domonas. In similar experiments I have always obtained this flagellate in
abundance.

° Further observations on Rotifers are here omitted.

CHLAMYDOMONAS AND HAEMATOCOCCUS 269

of, whereof most had the outermost part of their bodies a
pale green, and the middle of the body quite red.’

On the 15th and 29th of September, on the 13th and
27th of October, on the 25th of November, and the 9th of
December, I continued my observations aforementioned ;
steeping the said stuff* both in new-fallen rain, that was
collected in an East-Indian porcelain dish, and in boiled
and ordinary rain-water: whereof I kept notes. But as
the upshot was always one and the same, I discarded
these notes: and I will only say that, on the day last
mentioned, I put some boiled water, when it had got
nearly cold, with a little of the oft aforementioned
dirty stuff, into a glass tube that was sealed off at one
end, and stopt with a cork at the other, and carried it
about in my pocket: and I found some hours afterwards
that not only the big animalcules* . . . were swimming
in the water, but also many others so small, that they
looked through the microscope no bigger than a dot, such
as you might make with a pen. And when I had carried
this glass tube in my pocket for eight days, these last-
mentioned animalcules were so increased that there were
some thousands of them, both fixt on the glass and
a-swimming in the little quantity of water.

On the 8th of February,’ when the oft-mentioned stuff
had lain for a few days more than five months upon
a clean white paper in my closet, I put a little of it intoa
clean glass tube, and poured boiled rain-water, after it
had cooled, upon it: and after the space of about halt
an hour, I already found one animalcule swimming about
in the water, and many others that remained still rounded
up; and three hours later I saw various others of this
kind, and some small ones of a different make.”

_ ee ee ee) ee ee ee
1 Undoubtedly Haematococcus.
? i.e., the dry deposit in the gutter.
® There is a reference here to the figures, which shows that these big
forms were Rotifers.
* Presumably 1702.
® Possibly Protozoa.—These observations were referred to again by L. in

sé

270 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS”

Now since we see that these animalcules can lie bedded
so long in dry matter, as before described, and then on
coming into water can swell out their bodies, and swim
off; we may therefore conclude that in all pools and
marshes, which have water standing in them in winter,
but which dry up in summer, many kinds of animalcules
ought to be found; and even though there were none at
first in such waters, they would be brought thither by
water-fowl, by way of the mud or water sticking to their
feet and feathers.’

Seeing these wondrous dispensations of NATURE,
whereby these little creatures are created so that they
may live and continue their kind, our thoughts must be
all abashed; and we ask ourselves, Can there even now
be people who still hang on to the antient belief that
living creatures are generated out of corruption ?

About a couple of months after the foregoing lines were
written, Leeuwenhoek sent the Royal Society some further
observations on the animalcules occurring in rain-water.
The following is a translation of the greater part of this
letter : °

his Letter XXIX (5 Noy. 1716, to Boerhaave); Send-brieven, p. 288 (published
1718). Vide p. 297 infra.

1 These remarks recall a well-known passage in The Origin of Species,
where Darwin discusses the dispersal of organisms by similar means.

2MS. 28 April 1702. To the Royal Society. Not published in Dutch
or Latin works. English version (abbreviated) printed in Phil. Trans. (1702),
Vol. XXIII, No. 279, pp. 1152-1155 [where the date is wrongly given as
1701]. I translate from the original Dutch MS. According to my numera-
tion this is Letter 147: but Vandevelde (1924, p. 132), who did not detect
the error in the date as printed in the Phil. Trans., calls it “‘ Brief 2 Tr 1
[137a]”. The MS. of the English version is extant, along with the Dutch
original, in the Royal Society collection, and is in the hand of John
Chamberlayne.—Chamberlayne (1666-1723) was a miscellaneous writer
and translator—said to have been conversant with 16 languages—who was
educated at Oxford (1685) and Leyden (1688). He became a Fellow of the
Society in 1702, and translated—as will appear presently—several of L.’s
other letters for publication. His best known work—Magnae Britanniae
Notitia, which went through many editions—was a rescript of a smaller
book by his father, Edward C. It contains an interesting account of the
Royal Society—among many other things.

LETTER 147. 28 aprit 1702 271

On the 19th of September, 1701, it rained a little
while about noon, whereupon I caught some of the
rain-water, as pure as I was able to, in a clean East-
Indian porcelain dish :* putting this water then in a glass
tube, in order to see whether, in such new-fallen rain, on
standing in my closet, any living creatures would turn up.

I examined this water several days running, and dis-
covered therein many little bits of dust, otherwise called
particles, such as generally float in the air, consisting of
very little bits of burnt wood, or charcoal, wherein I
could make out the horizontal and ascending vessels;
also a little bit of straw, and many blackish particles
which I imagined to be congealed particles out of smoke
from the coals that our smiths and brewers burn: and
among these was a pretty structure” composed of round
globules clotted together, just lke the little stars that
we see in the snow in winter. But I could discover no
living creature till the 28th of September, when I dis-
covered some exceeding small animalcules that were
fixed to the glass, or anon swam forwards with a quivering
motion ; which afforded me no unpleasant spectacle.

These animalcules were so small, that I could only
make them out by very nice scrutiny; the tube, in which
the water was, being so big and thick; but especially
because the animalcules seemed to me as clear as glass:
but it looked to me as though their bodies were twice as
long as the width of their thickest part,’ the foremost
and hindmost parts of their bodies running somewhat to
a point.

z ‘in a fine China

in een suijvere gndiaanze porsteleijyne schootel MS.
Bason’”’ Chamberlayne.
2

‘

een aardig maaksel MS. ‘an odd Phenomenon” Chamberlayne.

* hare lighame twee maal soo lang waren, als deselve op haar dikste sijn
MS. “twice as long as they were big’? Chamberlayne.—The organisms
were probably flagellates, but are obviously unidentifiable. Their attachment
to the glass suggests Monas vulgaris, which would also fulfil the other
requirements of the description.

272

‘

LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS ”’

Yet from the 10th of October till the 14th of the same
month, I could perceive no living creature, how carefully
soever I looked. But whereas I had till now always
examined only the uppermost part of the water that was
in the glass tube, on the 15th of October I inspected very
narrowly the bottom of the glass tube (which was four
inches long, and had a diameter of a third of an inch):
and there I saw very many of the animalcules aforesaid,
both fixed upon the glass and swimming forth; and
many others sat so still upon the glass, that you might
think they were not animalcules at all; but when one of
’em moved, among the crowd, several others next to it
did too.

Not being content with these my observations, because
I misdoubted me whether there might not well have been
some water in this tube previously, and that from this
source these animalcules had come, and had remained
fixed to the glass, before I poured this rain into the glass
tube: in order to satisfy myself hereof, I procured a glass
tube that had lain full twenty years shut up in a dry
chest, and whereof I was assured that neither the least
water, nor anything but air, and what is therewithal
contained in it, could have gotten into it.

On the 18th of October it rained in the forenoon, after
we had had several days of strong and stormy wind: and
I once more caught the rain in the porcelain dish, and
after flinging away the first two lots received in it, I
poured the third lot of water into the glass tube.

This last water I viewed many times ; but how curiously
soever I looked, I could make out no living creature in it,
though I saw particles stuck to the glass, that agreed in
bigness and figure with the animalcules aforesaid : till the
24th of October, when I discovered three animalcules that
were running along and swimming forward against the
glass, and not in a straight line, but with bendings and
turnings as they went along: and the day after, I
discovered like animalcules in quite ten different places,

ANIMALCULES IN RAIN 213

both running forward and swimming, and that as
plain as if you saw, with your bare eye, those little
animals that the common man calls Water-fleas, swim-
ming in the water.’

Now there lay against the glass, within the compass of
a coarse grain of sand, more than a hundred particles
that were of the bigness of the foresaid animalcules,
which particles I divers times viewed one day, to discover
if possible whether any living creature would come out of
them,’ or turn up thereabouts; but how carefully soever
I looked, yet could I discern no living creature among
these particles, nor those lying hard by: until the
28th of October, when I saw, among the particles last
mentioned, a good five-and-twenty animalcules swimming
forwards, as well as running upon the glass: and I did
then discern two sorts of animalcules,® whereof the
smallest appeared to me first shining, and then not
shining: and their shininess, so I imagined, was observable
whenas they swam with their back or uppermost part of
the body turned towards my eye. These last animalcules
had a quite different motion, in swimming forward, from
those a bit bigger. As regards the particles that were
fixed to the glass, I couldn’t see any change in ’em.

I examined the said water for several days running,
and I saw the smallest animalcules in such great plenty,
both coursing upon the glass and swimming, at every
spot where I cast my eye, that ‘twas amazing: and as I
was holding the microscope in one hand, and in the other
the glass tube (in which the water, owing to the width of
the tube, was set in motion),* I invariably perceived that

1 op het water MS. “in the ordinary Brooks and Canals ’’ Chamberlayne
—a picturesque but inaccurate rendering of the original.
2

‘

ut de selve . . . soude voortkomen MS. “whether they were

living Creatures’’ Chamberlayne.

* Probably protozoa, but not identifiable.

* i.e., by the warmth of his hand, producing convection-currents.

18

274 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

when the animalcules were aswimming, and got off some-
what from the glass, they were borne forward, as if they
were not strong enough (as you might say) to swim up-
stream: yet they alone made, as they went ahead, certain
windings, while the bits of dust in the water (which were
very big in comparison with the animalcules) were swept
forward in a straight line.’

I have also made sure that, when I put new-fallen rain
in a glass tube in which there was never before any
moisture, shortly afterwards very many little air-bubbles
made their appearance in it, and remained sticking to the
glass: but a little while later these air-bubbles were gone.

T'o satisfy myself further hereof, on the 6th of November
I took once more a new glass tube, and examined it
through the microscope: but notwithstanding I had very
carefully shut it up, and covered it over, I saw that there
were yet many very little bits of dust in it. On the
6th of November it rained again, and I caught the rain,
as before described, and put it in the glass tube; in order
to see whether in this one also the air-bubbles would
make their appearance, and whether they would then
vanish from sight.

I examined this water divers times, even after it had
been four hours in the tube; in which time I could
discover not more than two or three air-bubbles, which
were on a dried-up mite,’ out of which the air seemed to
issue.

But whereas I had stood the former glass tube upright,
and had put another one down somewhat aslant, I now
placed this last glass tube lying almost flat, only so that
the opening lay a bit higher, lest the water ran out of it,

' This passage is paraphrased by Chamberlayne, though its import is
correctly conveyed. It can hardly be doubted that L. was here able to
distinguish the animate from the inanimate particles.

2 ven wijt gedroogte mit MS. ‘‘a dry Particle” Chamberlayne. I do
not know whether the “mite’’ should be interpreted literally or
metaphorically.

OBSERVATIONS ON RAIN-WATER O15

and that the air-bubbles might keep the position that
they had at the top of the glass; and after the lapse of
ten hours I saw a great many air-bubbles, that were
mostly affixed to the said dust-particles. And forasmuch
as we know that no dry matter or any other particles, in
which air is included, when they get under water can
then get the water into them unless the air be first dis-
lodged, so the same held good also for the particles that
were in the glass tube.

But what is one to say of this, that some of the air-
bubbles were quite a hundred (and others several hundred)
times bigger than the particles on which they were
stuck ?

Next day, in the morning, I perceived no more than
four very little air-bubbles, and a few hours afterwards I
couldn’t find a single one.

I examined this water every day till the 14th of
November, but could discover no living creature in it;
and the day after, I had the mischance to let my tube
drop, so that it was smashed to bits.’

It is not possible to identify the organisms mentioned in
the foregoing letter, though some of them must certainly have
been protozoa. At the end of the year, however, Leeuwenhoek
wrote a very important epistle in which he described and
figured several freshwater protozoa which are easily recog-
nizable. This letter is so important, indeed, that I must
translate almost the whole of it. It is addressed to the Royal
Society, and runs as follows: ’”

1 The remainder of this letter deals with other subjects, and is therefore
omitted.

2 Letter dated 25 December 1702. To the Royal Society. MS.Roy.Soc.
Not printed in Dutch or Latin editions. English translation in Phil. Trans.
(1703), Vol. XXIII, No. 283, pp. 1304-1311. (The MS. of this translation
is also extant, and is in the hand of John Chamberlayne. See p. 270,
note 2, supra.) According to my numeration this is Letter 149. Vandevelde
numbers it ‘‘ Brief 2 Tr 3 [147] ”.—I have made my translation from the
original Dutch MS., but have compared it with Chamberlayne’s and note
one or two points in which his version differs.

276

LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS”’

I take the liberty of informing you, Gentlemen, that I
have oft heard the common people say that duckweed’,
which floats on the water, is generated in the ground
underneath.

I could not allow of the truth of this assertion; for
whenever I examined duckweed, I always found that one
of these plants is produced by another, as with trees and
other vegetables.

Whenever I turned my attention to duckweed, I always
noticed that it never grows in deep water, even though
the water be small and stagnant, and without motion,
save such as is imparted to it by the wind’; but it is
seen in great plenty on broad sheets of water, which are
not deep and have little motion, but especially in narrow
and shallow ditches.

I have also observed that in ditches wherein there is
very little water, the duckweed is very small, in com-
parison with that which is found on big sheets of water,
along the banks, where the water is shallow and has but
little motion.

Delfshaven, belonging to our Town, lies about two
hours’ distant from it; and from here, through a sluice
from the River Maas, the water that runs through our
town is let in with the flood in summertime, and this
water is then as clear as though we had the River Maas
itself here.

Now with this running water there is brought in, from
time to time, a little duckweed ; yet so little, that ’twould
take you half an hour to collect thirty little weeds in a |
pot all at once. I got some of the duckweed scooped out
of this water, in an earthen pot, with lots of water, so
that their roots might not be hurt.

I took several of these little weeds out of the pot of water

' het kroost MS. (alibi Eende kroost)=“ Lens palustris” of the old
writers = Lemna of modern botanists.

ge

‘and that the Wind does it no harm’’ Chamberlayne. This is a

mistranslation.

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dis ty Petra an Ai Best end

PLATE XXVIII

Philor: Transa t:M:9 84:

ILLUSTRATIONS TO LEEUWENHOEK’S LETTER ON THE ANIMALCULES
FOUND ON DUCKWEED (25 Dec. 1702)

Reduced from the engravings published in Phil. Trans. (1703). (In the
original drawings, in red crayon, the figures are reversed.) Figures re-
numbered to agree with original account.

facing p. 277

LETTER 149. 25 DECEMBER 1702 O77

with a needle, one after the other, as nicely as I was able
to, and put them in a glass tube of a finger’s breadth,
that was filled to the top with water, and also in a
smaller glass tube, and suffered their little roots to sink
down gently; and then examining these roots with the
microscope, I beheld with wonder many little animals
of divers kinds, which escape our naked eye; whereof
two sorts had long tails,* wherewith they were linked fast
to the little roots of the duckweed. In structure these
little animals were fashioned like a bell, and at the round
opening they made such a stir, that the particles in the
water thereabout were set in motion thereby, so that on
but two occasions was I able to discern the little instru-
ments* with which they brought about this motion. And
though I must have seen quite 20 of these little animals
on their long tails alongside one another very gently
moving, with outstretcht bodies and straitened-out tails ;
yet in an instant, as it were, they pulled their bodies and
their tails together, and no sooner had they contracted
their bodies and tails, than they began to stick their tails
out again very leisurely, and stayed thus some time

continuing their gentle motion: which sight I found
mightily diverting.

I got drawings made of some of these animalcules, as
they appeared when fastened to the root of a bit of duck-
weed. [See Plate XXVIII.*|

Fig. 1, ABC shows a bit of duckweed of ordinary
bigness, as it looked, when lying out of * ne water, to the

ne eye of my ME elAneTE,

1 Vorticellids. Cf. p. 118 supra.

2 ““T could not see those instruments. ... Chamberlayne. This is
not a correct rendering. L. says “soo dat ik maar twee maal hebbe
geste .: .”

* The figures on the Plate in Phil. Trans. were renumbered 6-12 (other
illustrations having been added); but I have here altered their numbers to
agree with L.’s original drawings and descriptions. Fig. 7 [12] depicts a
leaf of duckweed not mentioned in the passages here translated.

* buijten het water MS. “upon the water’? Chamberlayne.

278 LEEUWENHOEK AND HIS “LITTLE ANIMALS”’

Fig. 2, DEFG shows this duckweed with its little roots,
as it floated in a glass tube filled with water, whereby the
roots are displayed.

Fig. 38, HIKLMNOPQR shows a little piece of the
root of a duckweed, as it appeared to the draughtsman
through the microscope; in which rootlets you could
discern the vessels, with their divisions, running long-
ways along the root; and these rootlets (so I imagine),
when’ they are of no further use, and as it were withered,
get overgrown with very many peculiar long particles,
mostly forming little figures that you might call “flowers”,
as shown here for a short distance in Fig. 3, between K
aad: A

The animalcules aforesaid, that I have likened unto
little bells, are shown in Fig. 3, between IST * and NVW,'
whereof I have seen, upon some roots, even more than a
hundred living, attached by their little tails, within a
space such as HIKLM, Fig. 3; though upon other roots
I discovered none.

And I also saw fixed upon several roots one or even
(though very seldom) two little cases,’ of various sizes,
whereof the biggest is shown in Fig. 3, RXY. Out of
this little case a little animal, with a small part of its
body which looked roundish, made its appearance, as in
Fig. 3, XZY: and thereupon there suddenly came out of

SSS EEE

‘“‘\vhen”’ is here omitted by Chamberlayne, who thus gives a slightly
different turn to this passage.

2 Diatoms and monads.

* Carchesium polypinum—with branched (contractile) stem. Previously
mentioned by L. in Letter 96. See p. 211 supra.

‘ A group of 3 solitary individuals of Vortzcella sp.

° Kokertjens MS. From the description and figures it is clear that the
biggest organism here spoken of is not a protozoon but a tubicolous rotifer—
almost certainly Limnias ceratophylli. It is certainly not Melicerta (from
which L. clearly distinguished it), nor can it be Cothurnia (as Ehrenberg
and others have stated). This ciliate is described a little later. The “little
wheels ” were, of course, the cilia on the two lobes of the trochal disc—so
interpreted by all early observers of Limnzas.

7

VORTICELLIDS AND ROTIFERS 279

its roundness two luttle wheels, which displayed a swift
rotation, as shown in Fig. 3,a@bc. (The draughtsman,
seeing the little wheels going round, and always running
round in the same direction, could never have enough of
looking at them, exclaiming’ “O that one could ever
depict so wonderful a motion!”’) These little wheels
were as Closely beset with teeth, or cogs, as the wheel of
a watch might be: and when these animalcules had
thus performed their motions for some time, they pulled
their little wheels into their body again, and their body
right into the little case; and soon after they brought a
part of their body out of the case again, with the motions
aforesaid ; and at another time they would stay a long
while inside the case, as though shut up in it. But
although I had, indeed, formerly discovered such little
wheels on other animalcules” too, yet their bodies were
different from these, and their cases were of a dark nature,
so that you couldn’t easily make out the animalcules in
them; and therewithal they seemed to be composed of
pellets.

And I also saw some cases that were several times
smaller than that just mentioned, and these * were as
clear as glass, so that you could see the little creatures
lying within them quite distinctly. Fig. 3, Pdef, shows
the case, with the animalcule Pdf, occupying a part of it,
as it lay taking a rest. Fig. 3, ogh, shows the little case

1 konde men soo een wonderbare beweginge altijd vertoonen MS. “‘O,
that he could always see such a wonderful kind of motion’”’ Chamberlayne.
I take it that the artist’s wish was to be able to portray (vertoonen) this
motion—not that he might go on looking at it for ever. Regarding the
artist himself, see p. 343 sq., onfra.

2 Melicerta ringens. In later letters (MSS. 4 Nov. 1704, to Roy.Soc.,
and 28 June 1713) L. gives an admirable description of this rotifer, and
describes how it builds its house. See Phil. Trans. (1705), Vol. XXIV,
p. 1784: also Letter VII (Dutch and Latin works) and Phil. Trans. (1713),
Voleex VIET; p:.160:

* Bvidently not rotifers but tubicolous ciliates (Cothurnidae)—probably
the common Cothwrnia cristallina, though the species cannot be determined
from the description and figures.

280 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS”

with the animalcule as it looked when it stuck part of its
body (gh) out of it, at which time alone you could now
and then just make out the two little wheels,’ because of
their exceeding smallness, but only when its body was
straightened out, for otherwise it lay drawn up short.

Further, I discovered a little animal * whose body was
at times long, at times drawn up short, and to the middle
of whose body (where I imagined the undermost part of
its belly was) a still lesser animalcule of the same make
seemed to be fixed fast by its hinder end. Such alittle
animal, because of its wonderful structure and manner of
propagation, I have had drawn, and at least twice as big
as it looks to the naked eye when you see it in the water
and attached to the root of a bit of duckweed. Tig. 4,
ABCDEFG, shows this creature, whereof A is the hind
end that it hangs on by, while at CDE are shown its
eight * horns (though others a bit smaller had six horns),
as it looked when it had straightened itself out, for other-
wise it can scarce reach to a quarter of this length; and
its horns seemed to my eye to be made in so marvellous
a manner, that the draughtsman’s art isn’t competent to
portray them, though the artist did his best to draw a
small bit of a horn, as shown at KLM in Fig. 5.

In Fig. 4, at BH, is shown a little animal that is coming
out of the first one; and formerly, when I saw such a
little animal fixed to a bigger one, I imagined that it
was only a young animalcule attached by chance to a big
one; but by nicer attention to the matter, I saw that it
was a reproduction: for I observed that whereas the
second animalcule, at the time when I first recognized
that it really was one, had only four very short little

1 A misinterpretation of the peristomial cilia. In Cothurnia it is very
common to find 2 individuals (the products of fission) in the same house.

2 Hydra—the first description of this organism.

* The draughtsman—as will be evident—inadvertently depicted nine
tentacles instead of eight: ef. Plate XXVIII, fig. 4.

HYDRA DISCOVERED 281

body and its horns had increased in bigness, and four
hours later still I saw that it had forsaken its mother.

When I discovered the young animalcule aforesaid, I
also perceived that, on the other side of the body of the
first animal, there was situated ' a little round knob, which
J did see getting bigger, from time to time, for the next
few hours (as shown in Fig. 4, between G and I); and at
last it appeared as a little pointed structure, which had
so far grown in bigness in the course of thirteen or four-
teen hours, that you could make out two little horns
upon it. After the lapse of another four-and-twenty
hours, this last-mentioned animalcule had four horns,
whereof one was small, a second a bit bigger, and the
other two much bigger; and these last the little animal
stuck out at full length, or pulled in short. And another
three hours later this little animal was gone off from his
mother. *

I tried to trace this reproduction further, and for this
purpose took the duckweed away from the animalcule, so
that I could follow it better; but next day that animal-
cule not only lay dead, but its horns and a piece of its
hind end were all gone, having rotted off, as you might
call it.

Another little animal, that had brought forth two young
ones, not only had her body laden with many other

1

aan de andere zijde .. . een rond knobbeltje zad MS. I take this
last word to be a verb (zat=sat). Chamberlayne, however, evidently
took it for a substantive (zaad = seed), and consequently translates ‘a round
little knob of seed”. But I cannot reconcile this interpretation with the
construction of the sentence as a whole, and at this period L. always spelt
zaad (=seed, a frequent word with him) with aa—never “ zad”. ‘A knob
of seed”’ is also an unintelligible expression. Dr A. Schierbeek (in. litt.)
agrees with my interpretation.

2 All the foregoing observations on the budding of Hydra are very
remarkable. No animal which reproduces asexually by budding was known
at that date; and the sensation caused by the similar observations of
Trembley, and others, nearly half a century later, is in strange contrast
with the apparent indifference which greeted L.’s discovery.

ce

bo
OO
bo

LEEUWENHOEK AND HIS “LITTLE ANIMALS”
animalcules’* (which are flat beneath, and roundish above,
and which I have discovered in most other kinds of water,
and which are hardly a thousandth of the size of the
animals which they crawl on with their little feet, and
cause annoyance to); but a much bigger sort of animal-
cules ° whose bodies were roundish, so pestered one of
these little animals, not only getting on her body, but also
by clinging on to her horns, that in spite of all the struggles
she made with her horns and body, she couldn’t shake it
off; and I noticed afterwards that the little animal had
lost one of her horns.*

“ What seemed to me remarkable and wonderful,
was that these little animals would oft-times let down
their horns so far, that you would think, on seeing them
through the microscope, that they were several fathoms
long.

At one time or another I let the draughtsman have a
look at the horns as they were being stretched out, or
anon pulled in; and with me he was forced to exclaim
‘What wonders are these!” For as the creature pulled
in its horns, they became perfectly round, and the closer
they got to the head, the thicker they became, and when
they were pulled right in, they formeda still bigger round
blob.

I charged the draughtsman to draw, as well as he was
able to, a small part of a horn when so stuck out, which
is here shown in Fig. 6, NOP. On this part are shown

' Evidently the “common polyp-louse”’, Trichodina pediculus.

2 The “large polyp-louse”, Kerona. The ciliates ectoparasitic on Hydra
were again studied and described at a much later date by Rosel von
Rosenhof, Trembley, Baker, and others. This is the earliest account

of them.

* “in the scuffle’ is added here by Chamberlayne—a_ picturesque

addition, but not authorized by L.’s own words.

* T have translated the remainder of L.’s remarks on Hydra because they
are so entertaining : they contain no further observations on protozoa. But
Hydra, rotifers, and protozoa were all “ animalcules ” for L., and he did not
separate them zoologically ; so his views on one sort are illustrative of his
notions about all.

HYDRA AND ITS “ LICE” 283

the knot-like lumps, which are to be seen also in Fig. 5,
KLM. These lumps look to me as though they were
made up of seven round globules; to wit, one in the
middle, which sticks up a bit above the others, and the rest
lying round it in a rosette.

Now if we consider what a lot of instruments must all
be contained in a little piece like Fig. 6, in order that it
may be not only stretched out, but also drawn in, and
moved around, and with as many bends and knots in it too
as you might make in a piece of string; so must we
wonder all the more at such a contrivance. And who
knows but what every knot-like part may not also itself
be furnished with yet other organs, whereby they are set
in motion. Seeing these things I was put in mind of the
knotted threads over which people have spent so much
time these last few years:* and I said to myself, If the
ladies of our country could see such a wonderful and
perfect structure, would they not have reason to bewail
the time and gifts which they employ in making such a
lot of useless knots, in which not the least bit of art or
beauty is ever to be seen!

I saw in this water, or on the duckweed, many wonderful
animalcules, some of them getting their food from it, and
others (as I imagined) using it as a skulking place, to
avoid being devoured by little fishes: but the weed seemed
only calculated to show off’ the three sorts of animalcules
aforesaid.”

' This apparently refers to some kind of macramé-work in which L.’s
countrywomen then indulged: but I have been unable to find any other
reference to it in contemporary writers.

2 maar voor genomen de drie verhaalde dierkens aan te wijsen MS. I take

the above to be L.’s meaning. In his view, everything in nature was created
for some purpose ; and I suppose he would have said that one of the purposes
of duckweed is to accommodate and display animalecules such as Vorticella.—
The last words of the above sentence were omitted by Chamberlayne—
possibly because he could not understand what they meant.

* L. here describes the duckweed itself, and its generation, at greater

“ec

284 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”

Whilst observing this last weed, I saw with wonder a
creat many animalcules’ swimming in spirals through
the water, and they were in such a great number together
in so small a space, that they looked like a little cloud,
visible to the naked eye, in the water; and animalcules
of this sort I have never before seen in other waters, but
on the second day they were nearly all gone.

Furthermore, in this water there were so many sorts of
animalcules that I had never discovered in any other
waters, that I was mazed to see such a diversity of
structures; and each too had its own proper motion,
wherefore I many times looked upon these delightsome
and wondrous little creatures, which quite escape the
bare eye.

During these observations, I saw one sort that exceeded
many of the others in bigness, which were coupled
together,” in which act they lay very still against the
glass, unless a bigger sort came too near them: and as
they lay still, you could leisurely discern those instru-
ments wherewith they can so swiftly move themselves,°
and even the motions of certain parts in their bodies, from
which some would certainly conclude that they saw the
circulation of the blood ;* but I would sooner take it for
the chyle’ in the guts. These animalcules were so big
that you could descry them” in a glass tube, with clear

length. As this part of the letter—though very interesting—-is irrelevant
to the present subject, I have omitted it, and resume the translation at the
point where the animalcules are again referred to.

’ Probably protozoa, but unidentifiable.

? Probably ciliates conjugating. Cf. pp. 200, 205, 206, 213, supra.

* Cilia, in all probability: but possibly cirrhi.

“ This reference to the internal “circulation” is puzzling, unless L.

actually observed the cyclosis of the food-vacuoles (in non-conjugating
individuals) or the rhythmic pulsation of the contractile vacuoles.

° A modern reader might perhaps consider chyle here to be a mistake
for chyme: but in L.’s day these terms were often. used synonymously. Cf.
Lexicon Medicum (Blankaart, 1748; p. 192)—‘‘cHYMUS, idem est quod

”

chylus’’.
® j.e., with the naked eye.

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ebsites y ih an bie n ne is i ati fe yee

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Ra
i

wey
a? eat a
yt : ‘ oe Vy gel as ut ‘ ene tin H At } iy
SOS ana Sie | aan
a ee oa Var
fi 1, Mh ; v ; “iad ; i uP avai i 7 ie

erry” IM ky. os LEA ab mi vn onal oy eee La
. " i 7 Re lca. ; . ; ' Ati | \! Mi : ge A er : Mi .
\ ful iy ‘i lot rat f i : i _ ) f we) pee: ie ‘¢ , mi i if ii 1 <p
( AG 1 a = 5 roy

An

Wy i ba

hs Ba) hie? 95 NT On cet oe “i Ri
WL oe vey Hai ny A y mLeay “ rh arbi He My ta rh 7

m ie, a ih my) 1M aN : y een APD. Vie Ves
Prats wa a ie | ar Mi ay tek se

my tae aa! ayy:
hy
iy Hn ce ae tibel
oe baa Se
he cecal 143
NG. na hae Mle ts, er
a AW am fj aS, yep ; 4
hae ae es :

Oh , vi Ae
beck

ae

aaa. iis

‘ ae alee
ue ie
Mi i as x + hi
ah eit Vavete tt)

r ve ps Ahi

PLATE XXIX

Shepptels, Die ons Clete.
wer bed. Ko~urrn = Le
¢ ma PAL Vee oe Cho brrer en

~ Votn. ie Se Ps ets he feos Clevta Sith-en ben
| vegas Soro Race mit-temra Lemets_jwelolhe fer f

praia’ Sedeg De OU SMES hs Haar beer

Art ~m groethuys

Oa Lemmon Cat hoa) ny tn Se feet De Cowe
¢ eee ae cae Keot Las tae lw ge

Sagiu, (moar Pp Oiga! eas Kaede C4.
er, Desc Qveckiws booren Soo. Segre
ae en Ee, I sme se
Lens Croer Oreide grows ats f de aa hace te
maakteL leortn_~ ats one Sop |
Hee Kable g 4 eb Heres, epee ee |
vt PY Se Pee, eee en ays ter hows Ale 96 4 oe :
™welh doe. bf tol tie Sebo Arbee se ae (aw rat |
Shkeptele is ons aS SE ny ex fy oo. long
naa JEL oe Sotho Bin Hore

|
|
Atl. Ze "fo-cne { dat- 4reQDe At bn Glcet |

Hoos Shel Heerew.

LAST PAGE OF THE LETTER ABOUT DUCKWEED

Facsimile (reduced) of original holograph MS. (25 Dec. 1702). This is a
good sample of Leeuwenhoek’s handwriting and signature during his later
life.

farina m ORE

CONCLUSION OF LETTER ON DUCKWEED 285

water: and among many kinds of creatures, I saw some as
big as sand-grains, which had as perfect a structure as our
garden spiders.’

Here, Gentlemen, you have the notes that I have kept
about my observations on duckweed and little animalcules:
in making which I said to myself, How many creatures
are still unbeknown to us, and how little do we yet
understand !

The foregoing letter contains recognizable descriptions of
at least five different Cillates—Vorticella, Carchesiwm,
Cothurnia, Trichodina, and Kerona—all of which were first
observed by Leeuwenhoek. He had, of course, described the
Vorticellids at an earlier date, since when others had repeated
his observations: and he had also, as we have already seen,
previously observed the conjugation of freshwater ciliates—
here mentioned again. But the letter is, nevertheless, full of
protozoological novelties.

Little more than a month later Leeuwenhoek sent the
Royal Society another remarkable letter, which contained a
description of the curious colonial flagellate Anthophysa
vegetans—one of the “iron-protozoa.” This letter has been
generally overlooked by protozoologists, and nobody hithert °
appears to have identified the organism described. The
identification is, however, easy and certain. Only one inter-
pretation of Leeuwenhoek’s description and figures is possible.
I will now give a translation of the relevant passages in this
highly interesting letter: °

' Probably water-mites.

2 0. F. Miller, who rediscovered and named this flagellate (Volvor
vegetans O.F.M., 1786; p. 22, Pl. III, figs. 22-25), was apparently ignorant
of L.’s earlier observations.—I am aware that Anthophysa is mentioned
among L.’s discoveries in the ‘ Leeuwenhoek Film” recently exhibited in
Holland: but this mention was taken from my own note (1923), in which
T attributed the discovery to L. without specific reference to the letter here
translated.

* Letter dated 5 February 1703. To the Royal Society. MS.Roy.Soc. Not
published in Dutch or Latin Works. English translation (almost complete)
published in Phil. Trans. (1703), Vol. XXIII, No. 286, pp. 1430-1443.
The MS. of this translation is preserved along with the Dutch original, and
is in the hand of John Chamberlayne. The above is a new translation
(from the MS.) of a part of the letter only.—Vandevelde (1924, p. 133) calls
this letter “ Brief 2 Tr 4 [148] ”’; but according to my numeration it is
Letter 150.

286

LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

At the end of the month of July, 1702, I was standing
in front of my dwelling, beside the water’, which flowed
with a gentle stream through our Town, and was very
clear, and had almost the colour of the Maas water; when,
as the sun shone bright, I saw something moving in it,
which seemed to me a-glitter; and so I had a mind to try
and find out what this shining matter was.

In order to satisfy myself, I took a glass tube, having
very near a foot’s length and a finger’s width, and after
tying a string to it, I let it drop into the water; and when
it was nearly half full, I pulled it out of the water and let
it fall from a certain height straight down into the water,
so that, being right under, the tube got filled with water.’

Examining this water with the magnifying-glass, I saw
that divers sorts of animalcules were swimming about in
it, whereof some were of a structure that I don’t remember
to have ever before discovered in any waters.

I viewed this water divers times one day, but couldn’t
discover what occasioned the glittering that it had afore
twas put in the glass tube.

On the 4th of August, I saw, through a magnifying
lens, that in eight or ten places there were particles
sticking fast to the glass; so that though all the water,
and consequently all the very small particles that were
floating in it also, was moved (with a slight motion which
I imparted to the tube)*, yet these particles remained
stuck to the glass.

This constrained me to examine them through the
microscope, and I saw then that the particles looked like
a complete bough off a tree, with its many twigs, as we
might see it with the naked eye; some of them differing
from others in the number of their twigs.

1 j.e., the canal [in the Hippolytusbuurt |: so rendered by Chamberlayne.

2 This passage is abbreviated by Chamberlayne.

* This terminal bracket is not in the MS.—apparently owing to an over-
sight: and the sentence, which is rather involved and disorderly in the
original, I have had to rearrange somewhat in order to make its meaning

clear.

Chamberlayne’s words are a short paraphrase.

LETTER 150. 5 FEBRUARY 1703 287

Nearly all of these branch-like particles were fixed by
their little stalks to the glass, and seemed to have had
their beginnings in a little bit of matter that was stuck
to the glass.

To satisfy myself further hereof, on the foresaid fourth
of August I put some of the water that was flowing along
in front of my dwelling into another glass tube, which
was rather longer and wider than the first, after flinging
away the first and second lots of water that entered the
tube.

IT examined this water divers times; and after it had
stood some thirty hours in the tube, I discovered the
bough-like structures as perfect as I have before described
them; and among others, one that lay so that the thick
stem from which the other branches sprouted seemed
right against my eye.

I fixed a microscope before this last-mentioned particle,
with the idea of finding out if ’twould grow bigger in the
course of time.

After the lapse of another six hours, I couldn’t discern
that it had increased in bigness; but now I perceived
that the extreme tips of the twigs, which were more than
twenty! in number, were nearly all beset with round
transparent globules,” whose diameters were quite three
times that of the extremities of the topmost twigs.

As I now saw that some transparent animalcules, of
the bigness of the round globules just described, were
moving about among the twigs, it occurred to me that
the round globules also might be animalcules, and that
these animalcules had made themselves fast on the
extremities of the little twigs aforesaid.’

RI ROE Ea SN Oe EE De ee

1 meer dan twintig MS. Chamberlayne wrongly translates “ about
twenty ’’.

? bolletjens MS. Chamberlayne translates “bubbles” —quasi belletjens.
But I think this somewhat distorts the sense. Bol and bel are not equivalent,
and I. does not use their diminutives indiscriminately.

* The flagellates forming the flower-like “heads” of Anthophysa do, in
fact, frequently break off and swim away.

288

LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS”

My opinion hereof was strengthened next day, when I
saw, in the morning, after the water had been twice
four-and-twenty hours in the tube, that nearly all the
round globules that were on the twigs had gotten off
them; and that some of these round globules, which I
was sure were animalcules, were moving about among
the branches, while a very few of them placed themselves
again on the twigs, and stayed sitting there motionless
for as long as I was busy looking at ’em.

After another twelve hours’ time, I could not perceive
that the bough-like structure was* grown any bigger;
but I then saw that a few of the twigs were again beset
with round globules, and that an animalcule, which was
at least fifty times bigger than one of the globules, was
running about on the branches: and forasmuch as the
ends of the twigs, whereon this creature had been running,
were once more laden with round globules, I concluded
(though I could get no ocular proof thereof) that the big
animalcule was dropping her young ones there.”

On the 6th of August, I took a glass tube that was
more than a foot long, and with a diameter of an inch;
and this one was sealed up at one end with the flame,
lest there might be some doubt whether the foresaid
bough-like structure originated from the cork: and after
I had rinsed it out once or twice, I put this glass tube in
my closet, and viewed it many times, but I discovered no
bough-like structures till after the water had stood in
the glass tube for about forty hours,’ when I fastened a
magnifying-elass to the tube, to see if the bough-lke
structures (after I first saw them) would not grow any
bigger. But how nicely soever I viewed them, I could
make out no change in them.

eee eeeeeeeeeeeeeeeeeeeeeF

ut

waren MS.—a false concord. The observation seems to have been

made on one © bough”’, and I therefore translate accordingly.
2 This was, of course, an error. The “ big animalcule” was probably a
ciliate—some of which prey upon Anthophysa.

° ontrent veertig wren MS. Chamberlayne mistranslates this “ above
40 hours”’.

;
at i” a ‘ ul vba

eee

‘im " ; eae .. : : Sas
pay i eas id a ¥) Relea ss : ais

a ge. teas a : a

{ tied! a i" oan

. ie i Roca

’ ; : ;
i ey en A Le > > >

Cea Tah
i he | ees te at
; - 7m ie ‘24 en

mens * a , Ri’
Paes” a ne an oe |

mass \ ; rain i Ae ee en -
cn 7. Ny w Wit bie re ne ire mi ,) Pe i
a ir AP a : : ie My oy a eel aire! a Ay ne

, ie ee eee

ig Nae De iy io pear, ne ; a
a g ce i ely eae i: By en fl pio t Py
. 7 ii ee - Me he ee The i ih, we . Nad
ee! 6%, Ot ce ne
ah a Bissek er tad Pa sty ae it Ate uM " a
; oy pe A eth Me iy ‘ol SL | hy ‘ ray i Z i
i : vn Vy a0 0) a Teed th : ' y
Haat eee |
hae PI a lly ann ¥ ;
F es ey ee ' OF a ak ? ang j , RI oy ats :
; ®t dg :
oe ee Wa aie i a ae |
i De eh hw h aie aS) 0 ae
q os ig sn ene Ms = Ne, |
Beis Maen : We an

4 in

PLATE XXX

philos :Transacttl -228¢

LEEUWENHOER’S FIGURES OF Anthophysa vegetans

From the engravings in Phil. Trans. (1703), illustrating his Letter of 5 Feb.
1703. (The original drawings, in red crayon, are reversed.) Slightly
enlarged.

facing p. 289

ANTHOPHYSA VEGETANS 289

And now I also saw that upon the extreme tips of a
very few of the branches there were three or four, or
sometimes even five, round globules, set beside one
another like a rosette; which afforded no unpleasant
spectacle. For when one such branch was fastened to
the glass by its thick end alone (from which all the other
lesser branches sprang), then all the twigs’ were put in
motion by any little movement which you imparted to
the water ; whereby also some of the aggregated globules,
which were set thereabouts, and which you would judge
not to be stuck fast upon the utmost twigs, were’ like-
wise put in motion: but I assured myself, after divers
observations, that they were really fastened thereto,
though I could make out no structure whereby they were
joined, owing to its exceeding thinness.”

I let the water run very slowly out of the glass tube, in
order that the branches (which were fastened to the glass
by their stem, and whose twigs were kept in continual
motion when one handled the tube) might lie against the
glass, as the water ran off them, so that my draughtsman *
would thus be able the better to make a pipeure of them.
[See Plate XXX. ]

Fig. 1, ABCDEF, shows the structure described, as it
was lying against the glass. A represents the part that
you would put down as the root of a plant, whereby
alone ‘twas fastened to the glass. We see here what a
lot of twigs there are on it, which now look rather
disorderly ravelled together, though lying free in the
water they were not unpleasant to behold: especially
because their colour was like that of oaken wood, and in
many places they were encrusted with little round

1 alle de sprankjens MS. Chamberlayne says “all the five small
Twigs’; but this is not in the original, and does not make sense.

2 IT supply waren, which is missing in the original—apparently owing to
the presence of the same word in the clause immediately preceding.

* This sentence is much condensed in Chamberlayne’s translation.
* Cf. p. 342 infra.
19

290

LEEUWENHOEK AND HIS “ LITTLE ANIMALS”’

cranules, just as if they were made up of congealed round
particles.’

At G, and hard by D, are shown the rosette-like struc-
tures which seem to consist of several globules, and
whereof some are also indicated at H: and though I
couldn’t see that the structures shown at H were joined
to twigs, yet they always moved about in the water in
the same way as the utmost little twigs did.

No sooner was the water poured out of the glass tube,
than I forthwith viewed the structure aforesaid: and
thereupon I saw swimming, between the twigs called BD
and BE, two animalcules as small as each of the globules
whereof the structures shown at H are made up: and
these animalcules then went on swimming, even in the
little water that had not yet evaporated from between
the twigs, till my eye wearied with looking at them.
During this observation I further saw one of the four
globules shown at H break off, and make off as though
swimming away, though the distance of its removal was
not above a hair’s breadth: and this particle which swam
off was certainly an animalcule, for it turned and twisted
itself round about several times. And in another globule
I did also see indeed a little motion ; but it didn’t break
off from the others, with which it formed the figure of a
rosette.

There were, furthermore, many other little bough-lke
structures which did not lie so orderly: and when the
water ran off them, they took on the shapes shown in
Fig. 2, IKL, and Fig. 3, MNO.

What are we to say about the fabric of these little
boughs, or tree-like growths? We can’t suppose that
they proceed from a seminal matter in the water: but,
with submission to better judgements, we are more
satisfied by imagining that they are composed of some
substance which, floating in small particles in the water,

1 The stalk of Anthophysa is encrusted with brown particles of ferric
hydroxide, and this is by no means a bad description of its appearance.

ANTHOPHYSA DISCUSSED 291

is clotted together by some kind of mutual attraction.
This won’t seem strange to us, if we bear in mind that
whenever we file a bit of iron it gets rather hot; and if
we apply the filed part to the filings, they’ll stay hanging
chain-wise from it; though in nothing like the way
such filings do with a lodestone.

At this point Leeuwenhoek digresses into a description of
some chemical experiments. ‘Then, after describing how he
dissolved a little metallic silver in dilute nitric acid, he tells
us how he witnessed the wonderful branching “ tree” which
grew in this solution when he dropped into it “a particle of
copper of the bigness of a sand-grain.” Such “trees” are
now familiar to every schoolboy, but in Leeuwenhoek’s time
they were novelties: nor has their wonder been wholly
evaporated away by the work of modern chemists.’ It is
clear, moreover, that Leeuwenhoek saw in the metallic “tree”
a physical analogy—suggesting an explanation of its growth—
to the ‘“‘tree” of Anthophysa, formed (in part) by the con-
gealed particles of ferric hydroxide: for he adds ‘‘ I observed
with a great deal of pleasure, how the Silver in this clear
Water was coagulated into such bodies as are described by
the above-mentioned Trees”’.*” Nevertheless, while recognizing
the resemblances, he confesses that the process of growth is,
in both cases, to him “ wholly inscrutable ”’.

About 10 years later Leeuwenhoek sent another most
interesting letter to the Royal Society—a letter in which he
described anew his observations on Rotifers and Vorticellids.
After referring to his previous observations on Melicerta, and
its ciliary mechanism, he says :°

1 Cf. Leduc (1911).

® Chamberlayne’s translation.—L. gives a figure of his “ silver tree ”’
which is, I believe, the first ever published. His observations are, apparently,
unknown to Leduc and other recent students of similar phenomena.

° From Letter VII. 28 June 1713. To the Royal Society. MS.Roy.Soc.
Published in Brieven, IV, 64 (1718); Epist. Physiol. (Op. Omn. IV), p. 63
(1719). English translation printed in Phil. Trans. for 1713 [published
1714], Vol. XXVIII, p.160. (The MS. of this translation—in an unknown
hand—is preserved in the Roy. Soc. collection.) I translate directly from
the original MS. in L.’s own hand.

292 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS

Notwithstanding I have so many times seen such
animalcules,’ and let others see ’em too, yet one can’t be
satisfied with just looking at* so wonderful a structure:
chiefly because one can’t get clear on how such an
unbelievable motion is brought about, and in the second
place, as to what purpose this motion was for. For when
we see any part of such a creature (that is endowed with
motion *) moved,* we feel sure that this part wasn’t made
for nothing, but is a necessary part of it; and conse-
quently this wheelwork is of use to the animalcule’s body,
though we can’t call to mind just what use it is.’

He then records some further observations on Rotifers—
made “at the end of July and the beginning of August
[1712] ’—and proceeds :

Furthermore, I paid great attention to their revolving
toothed wheelwork; and I saw that an incredibly great
motion was brought about by the said instrument, in
the water round about it, whereby many little particles,
that could be made out with the magnifying-glass, were
wafted towards the animalcule, while others were carried
away from it; whereof some, being borne into the middle
of the revolving instrument, were used as food by the
animalcule.’ And other particles, when they got up to it,
went off from the animalcule as quick as if it flung them
away; seeing which, I came to the conclusion that the
cast-off particles were no good to the creature for food.

From this observation we may well conclude that, since

1 Called Dierkens throughout in the Dutch printed version, but Dieryens
in the MS.

* te beschouwen: these words are in the printed version but not in
the MS.

° The words in parenthesis are in the MS. but not in the printed version.

4 bewegen MS. dat bewogen werd printed version.

° 4s printed version was MS.

5 van het Dierke als tot spys gebruykt wierden Dutch printed version.
The MS. says het Dierke als tot spijs gebruijkte (the animalcule used as
food).

LETTER Vil. 28 JunE 1713 293

these animalcules can’t displace ’emselves' in the water,
they can’t” chase after their food, like all* other creatures
do that are endowed with motion, so that they can get
from place to place.’

These animalcules,’ then, and all the others too, that
can’t shift ’emselves from place to place, either because
they are fixt by the tail, or otherwise, must be furnisht
with similar instruments, in order to make a stir in
the water; whereby they get any stuff that is in the
water for their food and growth and for the defense°
of their body.’

And when we observe the animalcules that are fixt by
a long tail*® to something or other, like many that we have
discovered on the little roots of duckweed,’ we see that
they don’t merely go round in a circle with the extreme
part of their body “ (whereby they make, in proportion to
the littleness of their body, a big bustle in the water) ; but
the creatures can also pull their tails together, and that
very quick too; so that when they stick their tails out
again, they displace the water round about them, and

1 Underlined in MS. but not italicized in printed version.

2 There are slight verbal differences here between the MS. and the printed

version, but they do not affect the sense.
3

alle is in Dutch printed version, but not in MS.

* The Latin version adds “ whenever they want to” (quoties libet): but
this is not in the Dutch.

° Soin MS. The Dutch printed version has “ animals” (Dieren).

S Referring to the pellets with which—as he had just described—
Melicerta builds its house. :

’ This passage is worded differently in the MS. and in the printed
version, but the sense is identical. In the Phil. Trans. the two foregoing
paragraphs were condensed into a single sentence.

* i.e. Vorticellids.

° Of. p. 277 sq., supra.

” L. means that the body of the Vorticellid travels in a circle round
the point of attachment of the stalk. The Latin translator apparently
misunderstood these words, which he rendered “ extremitates corporis sui in
orbem complicant’’.

294 LEEUWENHOEK AND HIS “LITTLE ANIMALS ”’

being thus come into different water,’ they can get fresh
food out of it.

Now I also saw a very few animalcules’ (whose bodies
were short and thick), that were much bigger than the
animalcules that make a little case for their dwelling-
place,’ and these were fixed to the little roots of the
duckweed by their hindmost or tail-like part; and not-
withstanding they were able to move from place to place,
they also made none the less a circular motion with the
foremost part of their body: whence I also concluded
that such a motion was for no other purpose than to
make anything that would serve as food come towards
them.*

I have ere now asked myself, What is the use of such
a toothed wheelwork, like a cogged wheel out of a clock ?
But if we now let our thoughts run on further, we must
decide that such a thing is necessary, if a great stir is to
be made in the water: for if it were a round and smooth
wheel, it would make little motion in the water; whereas
now every tooth that sticks out from the circumference
causes a great stir in the water, in comparison with a
smooth and even rotation.

This being so, we are faced once more with the
mysteries, and unconceivable order, which such tiny
creatures (which quite escape one’s naked eye) are
endowed with.

1 Underlined in MS., but not italicized in printed versions. The phrase
is rendered in Phil. Trans. “and so bringing fresh Water under them,’—
which is incorrect.

2 Clearly unidentifiable from this meagre description, but probably
rotifers.

* Referring to Melicerta (and the tubicolous ciliates ?). The word here
translated “ dwelling-place”’ is in the original hwysvesting, which may mean
“ edification ” in any of the literal or metaphorical senses which this word
has in English.

“ “From whence I concluded, that those Motions serv’d some other

purposes than only to draw their Food to ’em.” Phil. Trans. The
translator here completely reversed the sense of L.’s words.

CILIARY MECHANISMS 295

Can anybody doubt, after reading the foregoing words,
that Leeuwenhoek had, in 1718, already discovered the chief
function of the peristomial cilia (“ wheelwork”’) of Vorticella ?
Surely not. Old Antony knew as well as I do (and everybody
else now does) how the Vorticellids, and many other ciliated
organisms, capture their food from the surrounding water—
though he misconceived the structure of the mechanism. By
persistent study he had advanced a long way beyond his
original interpretations of 1676,‘ and had at last reached the
truth.

The remainder of this letter contains some further observa-
tions on “‘animalcules”’: and as some of these—though none
is exactly identifiable—were undoubtedly protozoa and
bacteria, I will now quote what else he here relates : °

At the beginning of the month of August,’ I was in a
garden where there was a pond well stocked with fish ;
and pretty well all over the water there floated a thin
scum, which looked greenish, though you couldn’t see any
other green-stuff in the water: which seemed to me odd,
because in other years* I had noticed that the water was
very clear in this pond, as it was also in the ditch from
which the pond was continually replenished; but I was
told that when it rains, the scum goes away.

I went a little aside, all on my own, and took a wooden
lath, with which I touched the surface of the water ; and
putting a little drop of the water in a green wine-glass, I
looked at it through a microscope that I had by me: and
I discovered in this water so unbelievably many little
animalcules, which even through a microscope are scarce
discernible, that no one could be made to credit it, unless
he got a sight of it for himself; and also divers sorts of

1 Cf. p. 118 supra.

2 The passages which follow begin at the top of p. 68 of the Dutch
printed works (Vol. IV, Send-brieven).

* Presumably anno 1712: but from the final paragraph this is not
certain.

* op andere jaren MS. “at other times”? Phil. Trans.

296 LEEUWENHOEK AND HIS “LITTLE ANIMALS”

large animalcules, mixt with very’ many air-bubbles, of
extreme littleness.

A few days’ afterwards, I asked to have a little of this
water brought to my house, in order to examine it more
nicely ; but I could discover nothing else in it than what
I have just related, though I noticed a little later that
no air-bubbles * were to be seen in it.

Now if people rinse beer and wine glasses in such a
pond, who can tell how many animalcules may be left in
these glasses ? whence some of them may even get into
our mouths. And this being so, people have no reason
to ask me how the little animalcules, which, as I have
said many a long year ago,’ are in the stuff between our
teeth, and in hollow grinders,’ are able to get there.

Thus far my notes, which I kept some years ago, and
which I have come across within these last few days.

Leeuwenhoek’s last recorded observations on protozoa are
contained in a letter written in 1716 to Boerhaave.° Unfor-
tunately they are mentioned very briefly—being sandwiched
in between observations and speculations on spermatozoa.
Despite their brevity, however, they are of extreme interest.

After speaking of the spermatozoa of various animals,
Leeuwenhoek abruptly interjects the following remarks: ‘

1 The word “very” (seer) is in the printed version, but not in the MS.

* Eenige dagen MS. Eenige weynige dagen Dutch printed version.

* Lugtbellen [underlined] in MS. The printed version has lugtbolletjes.
* Vide p. 238 sq., supra. The “ animalcules”’ were, of course, bacteria.

° inde stoffe . . . tussen onse tanden, ende inde holle kiesen [last
two words underlined] MS. “in and about our Teeth” Phil. Trans.
There are slight verbal differences here between the Dutch printed version
and the MS., though the sense does not differ.

®° Herman Boerhaave (1668-1738), Professor of Botany, Chemistry,
and Medicine at Leyden— ‘a whole Medical Faculty in himself’’—is too
famous a character to need further annotation. He was elected a Fellow of
the Royal Society in 1730. For his life see especially Banga (1868, p. 807)
and N. Nederl. Biogr. Woordenb. (1924), VI, 127 [a long and excellent article
by van Leersum J.

” From Letter XXIX. 5 November 1716. To Boerhaave. Published
in Brieven, Vol. IV, p. 284; and (in Latin) in Opera Omnia, Vol. IV
(Epist. Physiol.), p. 279. No MS., and not in Phil. Trans.—The passage
here translated begins on p. 288 of the Dutch edition.

LETTER XXIX. 5 NOVEMBER 1716 297

I can’t forbear adding here, that I have allowed water-
animalcules, mixed with a little earthy matter, to lie dry
in my closet for a whole winter: and when I put them
again in water, I saw some of them unfold their limbs,
which seemed to be wrapped up inside them, and swim
about in the water.’ I have also observed that animal-
cules, which really belong to the waters, are to be found
in the soil in our meadows ;” and these animalcules are
carried thither, along with particles of water, by strong
winds, and come not only from the canals but even from
the sea. And notwithstanding that most of these
creatures are unable to stand the winter’s cold, and so die,
yet some of them survive, to propagate their kind: and
this has been their lot from the very beginning of things.

Then a few lines further on we strike the following gem:

Now I must tell you that there is, right at the back
of my house, a small flat lead, on which the rain-water
doesn’t dry up for several days after it hath rained. In
this water I have many a time seen, among others, some
very little roundish animalcules, of divers sizes, and
whereof the bodies were round, and having a diameter,
when full grown, of about thrice the diameter of one of
those globules that make our blood red: and in their
bodies you could distinctly make out four round globules.
These creatures were so vastly multiplied in a few days,
that I was dumbfounded at it.

I was all agog to know how this multiplication might
come to pass: and in the end I found out that these
animalcules lived for no longer than 30 or 36 hours, and
that they then fixed themselves upon the glass, and
stopped there without moving: while soon after, their
body burst asunder, and lay divided into eight portions:

" These were probably Rotifers, though some may possibly have been
encysted Ciliates.

2 This is probably a record of the first observations ever made on soil-
protozoa.

cc

298 LEEUWENHOEK AND HIs ‘‘ LITTLE ANIMALS ”’

and these were actually young animalcules, for in five or
six seconds some of them swam off.

Inasmuch as one animalcule thus begets 8 little ones,
and each of these again brings forth 8: then there would
be produced, in the course of 9 days, two hundred and
sixty-two thousand one hundred and forty-four animal-
cules from a single animalcule:

In 30 hours; or 13 (days, 70... 8 animalcules
8
cK opto eae © C7 Renee Pe 64 animalcules
8
in AF dayseese 512
8
in 6 <dayaeseer 4096
8
in 7% days.......82768
8

in 9 days....262144 animalcules.

From the size and shape of these animalcules, as well as
from their habitat and method of reproduction, it is obvious
that they were some common phytoflagellate ; and it is highly
probable, since no mention is made of their colour, that they
were not the forms previously described (to wit, Haematococcus
and Chlamydomonas). I have very little doubt that the
description applies to Polytoma—of which it is, indeed, so far
as it goes, an astonishingly good description.’ The division
of the parent body into 4, and then into 8; the bursting of
the enclosing membrane, and the swimming away of the
daughter-individuals,—all this was observed and recorded
with remarkable accuracy.

How Leeuwenhoek was able to discover, with the limited
means at his disposal, the facts which are here so simply set

" Tam glad to find that Biitschli (Vol. II, p. 621) long ago arrived at the
same conclusion.

REPRODUCTION OF POLYTOMA 299

forth, must remain for ever a marvel. On reading these
passages the modern protozoologist, knowing the patience
and perseverance needed to make such observations—even
with adequate instruments, and with the accumulated informa-
tion of the next 200 years to help him—can only regard this
extraordinary old man,’ as he regarded his “little animals”,
with dumbfounded admiration.

—Door Arbeit en Naarstigheijt
komt men tot saaken die men
te vooren onna speurligk agten.
Actum desen 30: April 1698
ANTONY VAN LEEUWENHOEK

1 L. was 84 years of age when this letter was written—‘ in the autumn
of his life,” as he says a little later (cf. p. 88).

300

ELUCIDATIONS AND ANNOTATIONS

HE following supplementary notes—dealing with very
various subjects—are collected together here simply
because they are too long to print as footnotes to the

foregoing text. They contain much that is important for the
student of Leeuwenhoek and his writings, but the reader will
please bear in mind that they are notes and explanations
only—not full dissertations on the subjects treated. My
information has been gathered from many sources during
many years, but is still far from complete: and I offer it to fellow-
students merely in the hope that it may help them in their
own studies. On some matters I could, indeed, say much in
addition: but as Father Antony himself would say, “I will
spare you more, for ’twould else take all too long a-writing.”’

(i) LEEUWENHOEK’S NAME

As the curious name “ Leeuwenhoek ”’ has, seemingly, at
all times been a stumbling-block to foreigners (and has even
puzzled Dutch scholars), the following annotations may not
be amiss.

LEEUWENHOEK, as a surname, appeared until quite recently
to be extinct. I have been unable to find anybody bearing it
since the middle of the X VIII Century: but my researches in
this connexion were only superficial, and Mr Bouricius has
delved deeper and has deservedly been more successful. He
has discovered’ that there are still Leeuwenhoeks living in
Holland—“ between Oudewater and Gouda.” ‘They are, so
‘ Bouricius believes,’ descendants from Antony’s uncle * Huych
[=Hugh]|—his father’s only brother. (See the Family Tree,

’ Cf. Schierbeek (1929, 1930).

2 Mr Bouricius’s researches—though unpublished—seem to have been
very thorough: for Schierbeek (1930), who has seen his notes, says that
“the genealogy is completely ascertained’’ of these present-day Leeuwenhoeks.

* “ Oudoom”’ [ = great-uncle] according to Schierbeek (1930).

LEEUWENHOEK’S NAME 301

p. 18 supra.) Nevertheless, it is certain that, at the present
day, there can be no Leeuwenhoeks who are directly descended
from the great Antony himself: for he was the only son of
his father, and none of his male issue outgrewinfancy. His
sisters married—and so changed their names—while his only
surviving daughter remained unmarried.

The literal meaning of the name ‘‘ Leeuwenhoek”’ is
obvious: for leeww means a lion, and a hoek is a corner or
angle. (Accordingly, the name was neatly graecolatinized '—
in Antony's own lifetime—into “ Leogonus”.) That the
name itself is probably a place-name seems equally obvious,
especially as we find it coupled with van. A very plausible
derivation has been found recently by Bouricius (1924, 1925).
According to him, Antony’s forefathers resided in a corner-
house by the Leeuwenpoort (= Liongate) in the HKast-End of
Delft : * and consequently they were, in all probability, known
to their neighbours as the family “from the corner of the
Liongate ” (van [den] Leewwen[poorts] hoek).

At the present day there is nothing in Delft to connect
Leeuwenhoek and his family with the topography of the place.
It is true there is his effigy on the railings round the playground
of a girls school in the Oude Delft; but this was put there
recently in error.’ And there is also, of course, a modern road
called Antony van Leeuwenhoek singel—outside the old town,
and leading to the railway station.

For the orthography of the name ANTONY VAN
LEEUWENHOEK there is good authority. In his early life,
however, he signed himself “ Antonj Ieeuwenhoeck ’’—the
christian name ending with a longz (not English 7) and the
surname with ch, and without van. This is the spelling in all
MS. signatures up to and including Letter 39 (17 Sept. 1683):
but Letters 40, 41, and 42 are signed “ Antonj Leeuwenhoek ”—

1 Cf. the panegyric poem prefixed to the first volume of the Opera
Omnia.

2 In early days the town of Delft was fortified by walls and moats,
communicating with the outside by various “ gates’? (poorten). This
enclosure was originally effected about A.D. 1070-1072 by Duke Godfrey of
Lorraine, the Hunchback (Govert mit den bult, or den Bultenaer). Some of
these gates are still standing—more or less: but the Leewwenpoort was not
one of them. It was an alley near the East Gate (Oostpoort), and has now
vanished. Cf. Boitet (1729, p. 592), Bouricius (1924, 1925).

* See p. 338 seq.

302 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS”

still without van, but with final -/ in place of -ck. Letter 43
(5 Jan. 1685) is the first one signed “‘ Anton} van Leeuwenhoek ”’
—with long i, with van, and with -/: and thereafter he appears
generally to have written his name thus—that is, for the last
38 years of his life. In the year 1685-6, however, he himself
seems to have been in some perplexity regarding his signature :
for Letters 44 (23 Jan. 1685), 46 (13 July 1685), and 48
(22. Jan. 1686) are again signed “‘ Antonj Leeuwenhoek ”, while
Letter 45 (30 Mar. 1685) is signed “A: v: Leeuwenhoek ”
and Letter 47 (12 Oct. 1685) simply “‘A: Leeuwenhoek.” ’
Examples of his signature at different dates are shown in
Plates V, X, and XXIX.

In the Dutch published letters, the long 7 of the forename
was generally printed as a short <—though sometimes as a y.
It is therefore questionable whether “ Antoni” or “ Antony”
is to be preferred. I adopt the latter spelling as it is conform-
able with English usage,” and because an English y is a
justifiable equivalent of the long 7. We have in English no
such letter; and a terminal 7 not only appears strange to us,
but may even lead—as I can testify from experience—to
ludicrous mispronunciation of the name. I may add, for the
information of English readers, that the name ‘“ Antony” is
not accented on the first syllable in Dutch (as it is in English),
but on the second: Antény—not Antony.

On the memorial—in the Old Church at Delft—erected to
Antony. by his daughter Maria, the full name is latinized as
Antonius a Leeuwenhoek (the form in which it usually appears
in the Latin translations * of his works). But curiously enough
the Dutch inscription on the stone slab covering his grave gives

' Haaxman (1875, p. 6 note) has already discussed the proper spelling of
L.’s name, and adopted the same spelling as I do: but he had seen only a
small percentage of the extant MSS.—having consulted none of those in the
Roy. Soe. collection—and therefore had not the support (which I can claim)
of some 150 autograph signatures. Had he seen these, he would probably
have expressed his opinion more emphatically.

* Though L.’s chief Dutch biographer—Haaxman (1871, 1875)—also
invariably styles him ‘“ Antony,” Bouricius (1924, 1925), for reasons which
are not evident, prefers to call him ‘“ Anthony”; while Schierbeek (1930)
now names him “ Anthoni,’ and some other recent Dutch writers
“* Anthonie.”’

* Antonius de Leeuwenhoek also occurs, and possibly accounts for some
recent writers’ miscalling him ‘‘ de Leeuwenhoek”’ (instead of van L.).

LEEUWENHOEK’S NAME 303

his name as “ Anthony van Leewenhoek’’—the w having dropped
out of the surname, and an / and a y having crept into
the first name. In old Dutch—as in modern English—it is
quite usual to find “Anthony” spelled with an h. The
objection to spelling Leeuwenhoek’s name thus is that he
never—as far as | know—so spelled it himself.’

Authority might thus be found for a variety of spellings :
and if importance were attached to the orthographical vagaries
of Leeuwenhoek’s contemporaries, and of his interpreters and
commentators down to the present day, any one of a long list of
variant literal combinations might easily be advocated. I will
merely note here that in the English versions of his epistles,
published in the Philosophical T'ransactions, his surname is
spelled in no less than 19 different ways. It appears as
Leewenhoeck, Leeuwenhoeck, Leeuwenhoeek, Leewenhook,
Lewenhoeck, Leeuwenhoek, Leuwenhook, lLeevvenhoeck,
Leewenhoek, Leeuwenhoek, Leuwenhock, Leuwenhoeck,
Leuvenhook, Lewenhoek, Lewuenhoek, Lewuenhoeck,
Leewuenhoek, Leewnenhoek, and Leeuenhoek. Most of these
spellings, however, are certainly due to misprints or mis-
readings of his signature.

It is further noteworthy that Leeuwenhoek’s name has
suffered the most extraordinary mutations, mutilations, and
perversions at the hands of foreigners. Germans, for example,
commonly call him “Anton von Leuwenhoek ’”’—and_pro-
nounce the name as though spelled thus in their own
language; while to the French he is generally “ Antoine
Leuwenhoeck ’’—if nothing worse. It is almost the rule,
moreover, to find his name spelled in several different ways
by the same writer—be he English, French, or German.
Wrisbere (1765), for example, refers to Leeuwenhoek thrice—
calling him (in Latin) ‘“ Loewenhoeckius,”’ “ Lavenochius,”
and ‘‘ Loewenhoeck”’ on each several occasion. (Hxamples
could easily be multiplied.) But perhaps the most remarkable
transformations occur in Italian writings—even in those of
his contemporaries and immediate followers. As instances I
may cite Vallisneri, who usually called Leeuwenhoek
“‘ Lewenoeckio ” but on at least one occasion *‘ Le Wenocchio ” ;

" The name bestowed upon him at his baptism, however, was neither
Antony nor Anthoni, but ‘‘Thonis.”’ (See Plate III.)

304 LEEUWENHOEK AND HIs “ LITTLE ANIMALS”

while the illustrious and erudite Spallanzani regularly dubbed
him ‘‘ Levenoecchio’”’. ‘To Buonanni he was just “ Lauenoch”’.

Foreigners generally find great difficulty not only in
spelling Leeuwenhoek’s name but also in pronouncing it.
On the assumption, apparently, that it issome kind of tongue-
twister in an unknown and barbarous lingo, they invent and
emit noises unintelligible to any Hollander. Some of the
more confident commentators, however, tell us how to pro-
nounce the name properly. For example, Richardson (1885)
informs us that it should be “pronounced in English fashion
Leuvenhock”. J do not know why it should ever be pro-
nounced English-fashion—rather than Dutch-fashion: nor
can I imagine any reason for so singularly mispronouncing a
plain Dutch word. Certainly no native of Holland would
recognize ‘‘ Leuvenhock’”—pronounced English-fashion—if
he were to hear it. But I can assure my fellow-country-
men that the name ‘“‘ Leeuwenhoek” is pure Dutch, and
not so difficult to pronounce as it looks; and that no
Hollander will misunderstand if it be spoken as though
written in English “‘ Laywenhook”. This does not—as I am
well aware—represent modern Dutch pronunciation exactly ;
but it is phonetically far better than the common English
mispronunciations resembling ‘“‘ Lervenherk ” or “ Loivenherk ”
or “ Luvenhock”. The Dutch diphthong eeu(w) is closely
similar in sound to ay-oo (said quickly) in English: and there
is surely no conceivable reason why the Dutch oe (exactly
equivalent to oo in English, and to our own oe in the words
“shoe” and “canoe”) should be pronounced as though it
were German, French, Italian, or Latin.

The reader will no doubt recall (see p. 43 supra) that
Constantijn Huygens—who knew English well—said that
Leeuwenhoek’s name would be written “according to our
orthography ” as “ Leawenhook”. But the phonetic value of
ea in English is not now constant: it differs widely in
different words. Huygens evidently had in mind the modern
sound of these vowels in words such as “ great” or “ break ”"—
not in “real”, ‘seal’, ‘‘Chelsea”, or “bread”. (For some
judicious comments on this subject see Wheatley’s edition of
Pepys: preliminary “Particulars”, ad finem.) In Huygens’s
time ea in most English words “sounded as it still does in
‘oreat’” (Bense, 1925; p. 205). He therefore meant that
‘““Tieeuwenhoek”’ should be pronounced as ‘‘ Laywenhook ” in
English—as I have already said.

HIS NAME AND LANGUAGE 305

The Swedish traveller Bjérnstahl, who visited Leeuwen-
hoek’s tomb in 1774, says that the name should be pronounced
“ Tewenhuk” (more germanico). Jam not prepared to dispute
this: it is perhaps as near the truth as my own foregoing
attempt to imitate the sound in English. But when the same
writer adds! that the name ‘‘ Leeuwenhoek” means “ einen
Greif” [i.e., a griffin], I must part company with him. This
strange interpretation appears, indeed, to rest upon nothing
but an erroneous inference from the mutilated heraldic device
on the tombstone covering Antony and his daughter Maria—
which still shows a flying eagle bearing a scutcheon, on which
the Leeuwenhoek coat-of-arms was formerly emblazoned.”

It will be evident, therefore, that there is now no real
mystery enshrouding the name “ Leeuwenhoek”. We know
well enough how to spell it, how to speak it, what it means,
and where it came from. Any doubts which may still exist
about it are, apparently, due to mistakes or misunderstandings
manufactured by credulous or incompetent commentators.
No profound research is needed to arrive at such a conclusion :
it must be obvious to everybody—no matter what his nation-
ality—who devotes more than passing attention to the matter.

(ii) LEEUWENHOEK’S LANGUAGE

Leeuwenhoek’s only language was Dutch—not the modern
literary language of the Netherlands, nor Old Dutch (properly
so called), but the ‘‘ Nether-Dutch ” commonly spoken in the
Province of South Holland in the XVIJ Century. It is a
language far removed from that of “Reynard the Fox”
(Vanden Vos Reinaerde, written circa A.D. 1250), and is not
even so archaic as the Dutch Bible (which dates from 1637,
though—like the English—it contains much earlier elements).
Consequently, for any educated Hollander of the present day
it is no harder to understand than colloquial English of the
same period is nowadays to an educated Englishman.

IT have heard it said that Leeuwenhoek’s language is
more like Cape Dutch—the “ Taal” or “ Afrikaans” now

1 Vide Bjornstahl (1780-84) ; Vol. V, p. 364 of German translation (1782).

? The coat-of-arms proper (now gone) consisted of a don rampant azure,
tongued and clawed gules, in a field or. See Haaxman (1875), p. 125, and
Morre (1912), p. 15.—The grave was despoiled during the French occupation
of Delft.

20

306 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

spoken in South Africa—than modern Dutch: and I have
been credibly informed that a certain well-known historian
of zoology actually engaged a Boer from Cape Colony (in
preference to an educated Hollander) to translate some of
Leeuwenhoek’s original letters for him, in the belief that he
would thus obtain the most accurate English rendering. (I
have also been told that the Cape Dutchman declined the task
after inspecting the early MSS. He is said to have expressed
the opinion that they were really not written in Dutch at all !)
So far as I can judge, Leeuwenhoek’s speech was very different
from modern Afrikaans: but I have no accurate knowledge of
this language—what little I know being derived chiefly from
perusal of the interesting work of Bosman (1928). In any case
it is certainly a mistake to suppose—as I know some people
do—that Leeuwenhoek’s Dutch is as different from modern
Dutch as Chaucer’s English is from modern English. Any-
body who can read modern Dutch can, with a little patience
and practice, easily read Leeuwenhoek's printed letters.

That Leeuwenhoek knew no language but his own is
attested by himself and others. For example, he refers in
Letter 2 (ante, p. 42) to his lack of education in this
respect and Molyneux also comments upon it (ante, p. 58).
Numerous passages in the published Letters might easily be
cited to the same purpose,’ but perhaps the best testimony is
furnished by an unpublished letter written to Oldenburg in
1676. Oldenburg, it appears, had written to suggest that
Leeuwenhoek should conduct his future correspondence either
in French (which he supposed Leeuwenhoek must know) or in
English (for which he imagined a translator could readily be
found in Delft, as so many English were then in Holland).
Leeuwenhoek answered as follows :”

" Letter 15 (21 April 1676, to Oldenburg: MS.Roy.Soc.), of which an
incomplete translation was published in the Phil. Trans. (Vol. XI, No. 127,
p. 653. 1676.), is sometimes quoted in evidence. In this letter L. is made
to say: © I, by reason of my unskilfulness in the English Tongue, could have
little more than the contentment of viewing the elegant Cuts’’ [in Grew’s
Anatomy of Trunks]. But unfortunately the words here italicized (by me)
are not in the original MS. They are a gloss by the translator (Oldenburg),
and not L.’s own words. Nevertheless, the passage testifies that Oldenburg
was aware that L. did not know English.

* From Letter 13a. 22 January 1676. To Oldenburg. Unpublished.
MS.Roy.Soec. (The original is in Dutch—the above being my translation.)

LEEUWENHOEK’S LANGUAGE 307

Your favour of the 28th December [1675] has reached
me safely, from which I see that you doubt not but I have
a sufficient knowledge of the French language ; but I must
confess, to my sorrow, that I don’t know any tongue but
the Nether-Dutch, to which I was brought up: but if
you write to me in French or Latin, I can manage it
all right, as I have friends enough here who can translate
itforme. But with English I can’t cope, since the death
of a certain Gentleman who was well versed in that tongue.
I grant you there be plenty of the English nation knock-
ing about everywhere, but not all of them are competent
to translate the T'’ransactions out of English into Dutch:
for when I inquired here for a fit person, I was directed to
the chanter of the English Church (who offers his services
also for teaching English). This fellow, presuming to do
what I wanted, and having translated for me a bit
that roused my curiosity, twas so lame I could make
neither head nor tail of it.

In a slightly earlier letter” he also remarks parenthetically
(since I don’t understand English, to my sorrow,
and there's nobody in this town who has the ability to translate
into Dutch for me)”. It may be taken as certain, therefore,
that Leeuwenhoek could neither speak nor read any language
but his own. Consequently—and this must always be remem-
bered—he was never able to detect or correct mistakes
committed by the translators of his letters into English and
Latin. As these translators were often wholly ignorant of the
things which Leeuwenhoek was attempting to describe, their
versions should always be read with caution. In all cases
of doubt it is necessary to refer—whenever possible—to his
own original words.
One of Leeuwenhoek’s present-day countrymen,’ looking

(75

1 Howell, at an earlier date (1622), says “ There is no part of Europe so
hanted with all sorts of Foreigners as the Netherlands”’ (ed. 1705, p. 87).

2 Letter 13. To Oldenburg. 20 December 1675. MS.Roy.Soc.
Unpublished.

* Becking (1924).

308 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”

down upon him from the heights of his own wisdom, regards him
as a greatly over-rated dilettante '—“ illiterate,” “ uncultured,”
‘‘common to a degree ’’—and even goes so far as to aver that
this “bourgeois satisfait . . . rather took a pride in the
fact that he knew neither French, Latin, English nor German.”
But I know of no evidence in support of such a statement,
and it is clearly contradicted by the words “to my sorrow ”’
(tot mijn leetwesen) in the two foregoing extracts.
Leeuwenhoek was always ready to confess his ignorance, but
he was never proud of it. He would undoubtedly have said
that nobody but a fool could pride himself on knowing less
than other people.

Although—as already remarked—Leeuwenhoek’s language
presents few difficulties to his own countrymen, it must be
confessed that to foreigners his words often appear at first
sight very queer, and occasionally even enigmatic. But this
is merely due to certain peculiarities of spelling and speech to
which one soon becomes accustomed—peculiarities proper to
his age and country, and not eccentricities or comicalities
proper to himself. We see exactly comparable features in
English of the same period, and inexperienced modern readers
apparently tend to regard both as humorous. For example, I
have seen people laugh at a grave sentence in Robert Hooke
because the word “ guess” is spelled “ Ghesse”’: while Saville
Kent refers to the ‘‘quaint style of diction” of Oldenburg’s
excellent contemporary English translation of Leeuwenhoek’s
Letter 18 merely, I believe, because it was not couched in the
current English of 1880. Every serious student of Leeuwen-
hoek and Hooke must realize at once, however, that there is
nothing either “quaint” or “funny” about their phraseology
or spellings—any more than there is about Tyndale’s English
translation of the Gospel, or Spinoza’s Dutch writings on
religion.

The following few notes are not intended for Leeuwenhoek’s
learned fellow-countrymen or for professional philologists,
but for poor foreign scholars like myself—“‘illiterate”” and
“‘c¢ommon’—who have no special knowledge of the peculiarities
of his language, but who want to read and understand what
he himself wrote. I design merely to give a few hints such

1 “ dilettant”’ in Becking’s own Italian-Dutch-American-English.

LEEUWENHOEK’S LANGUAGE 309

as I should myself have found helpful when I first began to
try and read his own writings.

Leeuwenhoek’s speech is (pace Professor Dr Becking) an
interesting example of the Dutch of the transitional period
between the language of the Bible and the modern tongue.
It preserves not a few genuine old words, and sometimes
reflects the troubled history of his time; for we find, inter-
spersed among his homely native vocabulary, numerous foreign
intruders—mostly of French origin—which have not taken
root in the language, and which will therefore be sought in
vain in a modern Dutch-English dictionary. (I may instance
the following, which all occur frequently in Leeuwenhoek’s
early letters: presentatie, swperfitie, circumferentie, [en |devotr,
observeeren, imploieren, imagineeren, continuelyk.) The inter-
pretation of such words is, fortunately, seldom difficult for an
English reader, because we have incorporated their counter-
parts into our own tongue.

There is a vast difference between the early letters and the
last letters—not only in the handwriting but also in the words
and wording.' ‘he first letters are comparatively archaic,
and inscribed in the Dutch character: the last are far more
“modern ’’, and written in the “Italian”? hand which is now
universal. Between these extremes, however, all intermediates
occur. I would also note that the spellings and punctuation
are more “modern” and uniform in the Dutch printed letters
than they are in the original manuscripts. But this is also
true of English writings of the same period—so far as I have
studied them. “Correct” and uniform spelling seems to be
generally due to printers and compositors, rather than to
scholars and authors, in all printed languages.

Only the archaic and the irregular spellings likely to
trouble present-day foreign readers of Leeuwenhoek’s early
letters will be noted here. The genuine archaisms—as distinct
from the variations in spelling characteristic of the erratic
orthography of the period—are chiefly the following :

1 T am not concerned here with L.’s style of writing, which I can judge
only as a foreigner. His own countrymen not seldom speak of it con-
temptuously—Becking, for instance, and earlier Pijzel (1875), who describes
it as “ pretty slovenly” (vrij slordig).

310

LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

(1) VowELs

ae is written for aa (e.g. aen, daer, waer, aengaen, for
aan, daar, waar, aangaan).’

eij may represent ez: as weijnig [ weinig |, Mez | Mei], etc.

7, y, and 7 are often interchangeable, and do not always
correspond with the modern usage of 7, 7, and y.
The diphthong uy often stands for modern we.
Spellings such as the following are thus common:
jk, jmagineer, duijsent, huijs, Antonj [= ik, imagineer,
duizend, huis, Antony].

ou is occasionally written for oe: e.g. genouch | genoeg |.

we often occurs instead of ew or ww: e.g. curiues,”
generues, figuer [= curieus, genereus, figuur].

ue may represent wu: e.g. vuier, muyer, [= vuur,
muur |.

(2) CONSONANTS

c or ck commonly stands for /& (or sometimes £h),
Leeuwenhoek regularly wrote ick [for ik], welcke
[welke], oock [ook], malcander [malkander], clootgens
[klootjes|, comen [komen], druckingh |drukking],
trecking | trekking |, ete.

ch for g. For example nochtans [nogtans], wedjnich
[weinig]. The terminal was subject to elision,
however, before a following aspirate: thus L. wrote
hollicheijt [holligheid = holheid].

cx or cka for ks. Examples: sulca, sulckax [zulks].

d = dt = t. Examples: hadt [had], edethetjdt
[edelheid], Engelant [Engeland], Hollant | Holland],
goet [goed], hucjt [huid], zad [zat].

f = ff = v. Examples: halff [half], self [zelf], off
[of |, beneffens [benevens |.

— 7. Examples: diertgens [diertjes], deeltgen
[deeltje] .

gh=g. .g.langh [lang], hoogh [hoog], verwonderingh

[verwondering ].

‘ It may be noted, however, that L. generally spelled the noun haar

[= Engl. hair] as haiy—not haer. He adopted the latter spelling for the
possessive pronoun haar [ = Engl. her, their ].

2 L. also wrote curieuws and cwrius. .He also wrote coulewr or couluer

[for klewr] indifferently. ©

LEEUWENHOEK’S LANGUAGE 311

qu=kw=k. Hig. quaet [kwaad], quaelijck [kwalijk],
manqueeren | mankeeren |.

s = z. Hxamples of this equivalency are too numerous
for selection. Words such as sin [zijn], dese [deze],
seer [zeer] occur copiously on every page of the
early manuscripts.

sch and ssch sometimes stand for s or ss. Examples:
wasch | Du. was = Engl. wax], volwassche [| volwassen].'
We even find sch = z occasionally-—as in schonne-
schijn | zonneschijn].

th is occasionally written for ¢. E.g. voortseth
[ voortzet ].

x sometimes represents modern fs. Hxample: exter
[ekster ].

The wrregular and capricious spellings—common in English
and Dutch of Leeuwenhoek’s period, and of no philological
importance—are too numerous to mention. Variants may
often be found in the very same sentence. Itis perhaps worth
noting, however, that certain spellings are phonetically
interesting—the omission of letters indicating, for example,
that they were commonly not pronounced at that date. Thus,
the final -n (now silent in Dutch, though still heard in
Flemish) in a word like volwassen was sometimes unwritten
(volwassche) : while Leeuwenhoek also sometimes wrote seder
(for sedert), ondecking (for ontdekking), schilpad (for schildpad),
ert (for erwt) etc. He also occasionally added a consonant
where it is properly lacking—as in pampvter (for papier) and
miscroscope (for microscoop). The former is a vulgarism, the
latter a mistake. What appears at first sight to be a mis-
spelling is occasionally, however, an earlier form—such as the
word mergen (A.-S. Mergen), which Leeuwenhoek regularly
wrote for morgen (= Engl. morning, morrow) in his early
letters. Omme (for om: O.Du. ombe) occurs very frequently ;
while omtrent and ontrent are one as common as the other.

The only other obsolete usages likely to trouble modern
foreign readers are the frequent insertion of the negative
adverb en in phrases such as “ alsoo ick niet en versta ”, “ ick
miet en can”, “dat ick daer gansch geen sin utjt en conde

' _s and -ce may also represent -sch(e): thus, in Letter 13a we find “ de

france tael”’ and “ het frans”’ in the same sentence—followed by a reference
to ‘‘ de engelsche tael”’ and “ de engelse kerck’’.

312 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS”

verstaen’’, etc. etc. (in which en is now unnecessary and
untranslatable): and the habit which Leeuwenhoek (not
alone) had of dividing up his compound words into their
constituents—e.g., he commonly wrote over geset, voort comen,
al hoe wel, on na speurlijk, door gaens, etc., where we should
now write overgezet, voortkomen, alhoewel, onnaspeurlijk, door-
gaans, and so forth.

Leeuwenhoek’s language appears, to me, to be full of
philological interest ; but I am no philologist, and must there-
fore content myself with noting some of the more obvious
etymological and orthographic peculiarities of his writings.
In my study of his manuscripts and printed letters I have
been greatly aided not only by his contemporary translators
but also by the lexicographers of his own period; and for
the information of other students I therefore cite the chief
dictionaries and other linguistic works which I have found
most useful. Oudemans—the standard authority on Old and
Middle Dutch—I have consulted only occasionally, on special
points. Hexham, Hannot, and Halma have been of frequent
assistance, while Kiliaan and Martinez and Minsheu have
sometimes helped me over difficulties. Meijer’s Woordenschat
(1745) contains numerous words which I have found in no
other vocabulary : I should have used this valuable book more
if I had known of its existence earlier. But my chief help,
in translating Leeuwenhoek, has been the great dictionary of
Sewel (1708)—a man’ who possessed a wonderful knowledge
of the Dutch and English languages in Leeuwenhoeks time.
This dictionary has been my constant aid during the last 17
years, and I can confidently recommend it to anyone who
wishes to know the exact Dutch and English equivalents of

1 Willem Sewel (or William Sewell, as he would now be called in English)
was born at Amsterdam in 1654. His grandfather was an Englishman, who
married a Dutchwoman and settled in Holland. Sewel visited England as
a boy, but lived most of his life in Holland, where he was first a weaver,
then a journalist and translator, and finally the greatest of Dutch-English
lexicographers. His parents were Quakers ; and in addition to his dictionary
—which first appeared in 1691, and ran through several editions—he wrote
a ‘‘ History of the Rise, Increase, and Progress’”’ of this sect (published in
Dutch, 1717, and in English, 1722). Sewel died in 1720, aged 66. As he
regarded himself as a Hollander, he would be pained to learn that his life
is now to be found in our Dict. Nat. Biogr. but in no Dutch biographical
works which I have consulted.

HIS LANGUAGE AND MICROSCOPES ole

words and phrases current in Sewel’s day. For modern Dutch
and Dutch-English dictionaries I have relied in the main
upon van Dale and ten Bruggencate, though I have frequently
referred to other similar works. In common with all students
of early English, I have received help at times from the well-
known French Dictionary of Cotgrave, and Florio’s famous
Italian-English vocabulary. The English dictionaries—of
every period—which I have consulted, are all those to which
I have had access: they are therefore far too numerous to
mention. (I possess and regularly use more than a dozen.)
As several old Dutch-English phrase-books and grammars,
and the old Dutch Bible, have given me occasional assistance
in arriving at the exact meaning of old-fashioned spellings
ea I quote the editions of these which I have
used.

REFERENCES.—See, in the general bibliography at the
end, the following entries especially : Anonymus (1658),
de Beer & Laurillard (1899), Brenia (1702), Bosman
(1928), ten Bruggencate (1920), Cappelli (1912), Cotgrave
(1650), van Dale (1884), Florio (1688), Halma (1729),
Hannot (1719), Heugelenburg (1727), Hexham, (1658,
1660), Kiliaan (1599), Kilianus auctus (1642), Maigne
d’Arnis (1890), Martinez (1687), Meijer (1745), Minsheu
(1627), Oudemans (1869-1880), Sewel (1691, 1708, 1754).

(iii) LEEUWENHOEK’S MICROSCOPES AND
MICROSCOPICAL METHODS

Leeuwenhoek left us no description of the apparatus which
he used for making his observations on protozoa and bacteria.
As we have already seen, he kept “for himself alone” his
“best microscopes” and his “ particular manner of observing
very small creatures.” He never divulged his secret method:
though undoubtedly he had a real secret, which enabled him
to outstrip all other microscopists for at least a century. But
he left many microscopes behind him when he died, and a
few of these are still in existence. Consequently, we know
something about his apparatus, though we can still only guess
how he used it in making his “ best observations.”

The earliest particular accounts of Leeuwenhoek’s micro-
scopes are the descriptions of the instruments bequeathed

314 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS”

to the Royal Society.’ Martin Folkes," who examined
Leeuwenhoek’s cabinet of microscopes shortly after it reached
England, has left the following record”:

The Legacy consists of a small Indian Cabinet, in the
Drawers of which are 13 little Boxes or Cases, each
containing two Microscopes, handsomely fitted up in
Silver, all which, not only the Glasses, but also the
Apparatus for managing of them, were made with the
late Mr. Leewwenhoek’s own Hands: Besides which, they
seem to have been put in Order in the Cabinet by him-
self, as he design’d them to be presented to the Royal
Society, each Microscope having had an Object placed
before it, and the Whole being accompany’d with a
Register of the same, in his own Hand-Writing, as being
desirous the Gentlemen of the Society should, without
Trouble, be enabled to examine many of those Objects,
on which he had made the most considerable Discoveries.

Several of these Objects yet remain before the Micro-
scopes, tho’ the greater Number are broken off, which
was probably done by the shaking of the Boxes in the
Carriage. I have, nevertheless, added a Translation of
the Register, as it may serve to give a juster Idea of
what Mr. Leewwenhoek design’d by this Legacy, and also
be of Use, by putting any curious Observer in Mind of a
Number of Minute Subjects, that may in a particular
Manner deserve his Attention.

The 13 Cases abovemention’d are numbered from 15
to 27 inclusively,’ corresponding to which is the Register
of the Objects, Two to every Case, as follows.

1 See p. 95 supra. As is well known, these instruments are now all lost.
There is no foundation for the statement of Haeser (16532 Vol. I, p.a62*
repeated in 3rd ed. 1881) that they are in the British Museum—nor have
they ever been there, so far as I am able to ascertain.

2 See p. 102, note 4, supra.

° Holkes (1724), p.447 sq. L.’s own description of his cabinet has
already been given on p. 96 supra.

‘ Baker (1740, p.507), commenting on these numbers, says “it neces-

LEEUWENHOEK’S MICROSCOPES old

No. 15. Globules of Blood, from which its Redness
proceeds.

A thin Slice of Wood of the Lime-Tree, where
the Vessels conveying the Sap are cut
transversely.

No. 16. [ Blank. |

The eye of a Gnat.

No. 17. A crooked Hair, to which adheres a Ring-
Worm, with a Piece of the Cuticle.

A small Hair from the Hand, by which it
appears those Hairs are not round.

No. 18. Flesh of the Codfish (Cabeljaeuw) shewing
how the fibres lie oblique to the Membranes.

An Embrio of Cochineal, taken from the Egg,
in which the Limbs and Horns are con-
spicuous.

No. 19. Small Pipes, which compose the Hlephant’s
tooth.

Part of the Crystalline Humour, from the Eye
of a Whale.

No. 20. A Thread of Sheeps- Wool, which is broken,
and appears to consist of many lesser
Threads.

The Instrument, whence a Spider spins the
Threads, that compose his Web.

No. 21. A Granade, or Spark made in striking Fire.

The Vessels in a leaf of Tea.

No. 22. The Animalcula in Semine Masculino, of a
Lamb taken from the Testicle, Jul. 24.
1702.

A Piece of the Tongue of a Hog, full of sharp
Points.

sarily implies there were 14 preceding Boxes, since no Man begins with the
Number 15. Mr. Leeuwenhoek, then, had another Cabinet, that held 14
Boxes before ours in numerical Order, and probably each Box contained a
Couple of Microscopes, as our Boxes do.”

316

“ce

LEEUWENHOEK AND HIS LITTLE ANIMALS ”

No. 23. A Fibre of Codfish, consisting of long
slender Particles.
Another of the same.
No. 24. A Filament, conveying Nourishment to
the Nutmeg, cut transversely.
Another Piece of the same, in which the Figure
of the Vessels may be seen.
No, 25. Part of the Bone or Tooth abovementioned,
consisting of hollow Pipes.
An exceeding thin Membrane, being that which
cover’d a very small Muscle.
No. 26. Vessels by which Membranes receive
Nourishment and Increase.
A Bunch of Hair from the Insect call’d a
Hair- Worm.
No. 27. The double Silk, spun by the Worm.
The Organ of Sight of a Flie.

For the Construction of these Instruments, it 1s the
same in them all, and the Apparatus’ is very simple and
convenient: They are all single Microscopes, consisting
each of a very small double Convex-Glass, let into a
Socket, between two Silver Plates rivetted together, and
pierc’d with a small Hole: The Object is placed on a
Silver Point, or Needle, which, by Means of Screws of the
same Metal, provided for that Purpose, may be turn’d
about, rais’d, or depress’d, and brought nearer or put
farther from the Glass, as the Eye of the Observer, the
Nature of the Object, and the convenient Examination of
its several Parts may require.

Mr. Leeuwenhoek fix’d his Objects, if they were solid,
to this Silver Point, with Glew; and when they were
Fluid, or of such a Nature as not to be commodiously

" The reader will be better able to follow Folkes’s description if he here

looks at my figure 1 on Plate XXXI, facing p. 328.

LEEUWENHOEK’S MICROSCOPES ol’

view'd unless spread upon Glass, he first fitted them on a
little Plate of Talk, or excessively thin-blown Glass,
which he afterwards glewed to the Needle, in the same
Manner as his other Objects.

The Glasses are all exceedingly clear, and shew the
Object very bright and distinct, which must be owing to
the great Care this Gentleman took, in the Choice of his
Glass,’ his Exactness in giving it the true Figure; and
afterwards, amongst many, reserving such only for his
Use, as he, upon Tryal, found to be most excellent.
Their Powers of magnifying are different, as different Sorts
of Objects may require; and, as on the one Hand, being
all ground Glasses, none of them are so small, and conse-
quently magnify to so great a Degree, as some of those
Drops, frequently us’d in other Microscopes; yet, on the
other, the Distinctness of these very much exceeds what
I have met with in the Glasses of that Sort.

Folkes gives no figures and no further information of
material importance, though he makes the interesting state-
ment that Leeuwenhoek had previously presented to Queen
Mary, when she visited him at Delft, ““A Couple of his
Microscopes, which, as I have been inform’d by one who
had them a considerable Time in his Hands, were of the
same Sort as these, and did not any ways differ from one of
the 13 Cases contain’d in the Drawers of this Cabinet.” ®

ss — — —— — — — — ——

‘This is a very shrewd remark. Undoubtedly L. knew a great deal
about glass, and he was an expert glass-blower—as his recorded experiments
prove. He learnt the art by watching a professional at the fair in Delft,
and then practising by himself at home.

* Mary II of England, wife of William III of Orange. She died in
1694. Folkes calls her “the late Queen Mary,” and clearly did not mean
her sister and successor, Queen Anne (died 1714). Halbertsma (1843, p.14)
appears to have confused these two Queens when he says that L. was
visited by “ Anna Maria.”

* Folkes (1724), pp.450-1. Nothing else is now known about these
instruments, which have long since vanished—like those presented to the
Royal Society.

318 LEEUWENHOEK AND HIS “LITTLE ANIMALS ”’

The only other descriptions of the Royal Society’s micro-
scopes were given some years later by Henry Baker‘ (1740,°
1753), who determined their magnifying powers and—in his
second publication—also gave two diagrammatic representa-
tions of the instruments. Baker tells us that Leeuwenhoek’s
microscopes were under his examination for three months,’
but he found Folkes had already given “ such an exact and
full Description of their Structure and Uses, as renders any
farther Attempt to that Purpose intirely needless.” * He
notes that most of the objects before the glasses were even
then (1740) “destroyed by Time, or struck off by Accident ;
which indeed is no Wonder, as they were only glewed on a
Pin’s Point, and left quite unguarded. Nine or Ten of them,
however, are still remaining ; which after cleaning the Glasses,
appeared extremely plain and distinct, and proved the great
skill of Mr. Leeuwenhoek...’ He then makes the inter-
esting further remark that Leeuwenhoek’s skill was also
shown ‘in the Contrivance of the Apertures of his Glasses,
which, when the Object was transparent, he made exceeding
small, since much Light in that Case would be prejudicial ;
But, when the Object itself was dark, he inlarged the Aperture,
to give it all possible Advantage of the Light.” ’

But we are chiefly indebted to this verbose amateur for
having carefully determined the focal length and magnifying
power of every lens in the collection—notwithstanding he

1 Henry Baker (1698-1774) was a Londoner, whose varied activities
included dabbling in science. As a boy he was apprenticed to a bookseller,
but later he made a fortune by teaching deaf mutes by a secret method of
his own. In 1729 he married the youngest daughter of Daniel Defoe. He
was elected F.R.S. in 1741, and by his will endowed the ‘ Bakerian Lecture ”’
of the Society. In early life he wrote much poetry and light literature. His
chief contributions to science were two popular books on the microscope—
mainly compilations, containing little original. In these works, which ran
through many editions and were translated into several languages, he drew
largely on L.’s letters. Cf. Dict. Nat. Biogr. and Rec. Roy. Soc.

2 Though dated 1740, this paper must have been published considerably
later: for it contains a reference to the 2nd edition of Baker’s Microscope
Made Easy (1743: 1st ed. 1742), and he styles himself F.R.S.—to which he
was not elected until 12 March 1741.

* Baker (1753), p. 434 footnote.
* Baker (1740), p. 504.
° Baker (1740), p. 504.

LEEUWENHOEK’S MICROSCOPES 319

‘‘was sensible it must cost much Trouble.” ‘‘ This Task,”’
he says, ‘“I have performed, with as much care and Exact-
ness as I was able.” His results were summarized in a table,
which I here reproduce in full: *

A Table of the Focal Distances of Mr. Leeuwenhoek’s 26
Microscopes, calculated by an Inch Scale divided into 100
Parts; with a Computation of their magnifying Powers,
to an Hye that sees small Objects at 8 Inches, which is the
common Standard.

Micro- Distance Power of mag- Power of mag- 1
scopes with of the nifying the Dia- nifying the ie
the same Focus. meter of an Superficies. oN
Focus. Object.
Parts of an Inch Times Times
ale so O goo ee ee AGOW: 5: 5,c on ke eae sO OOO >
1: Fae eRe OR 133; nearly <9 )-ucva oso.
1, TG) ene Meee 114) nearly:« <¢icccuansn ete 12996:
3. FAG ORES tien LOO 3s, sas Yay edo 10000.
3. Bera ht gessoi ag ck nal atlas 89! almost... cco useemes 7921 almost.
8. Sep wee eu eaayts er. SO. sat «cise nee 6400.
2. iro eC ee 72 something more... 5184 something more.
3. eh oes She = 66 nearly’... 5". «eas 4356 nearly.
2. Sea ota satet aie Diy! a Lay gsy chee eee 3249,
al Se (AE aoa ee ae BS mearly, i.) cucseasas ss 2809 nearly.
1. at Pee See a 40: ' 2S 2 ca eee 1600.
26

* This largest Magnifier of allis in the Box marked 25. [Note by Baker. |

Baker himself notes regarding these figures: “ I have given
the Calculations in round Numbers, the Fractions making but
an inconsiderable Difference; and I hope any Mistakes I may
have made in so nice a Matter will be excused”. I must also
note—since it has been generally overlooked—that all the
magnifications are given for an image-distance (8 inches)
which is not the “common standard” now universally adopted
(10 inches). Consequently, all Baker’s “magnifying powers”’
represent only ~ of the actual magnification according to
modern notation: and therefore the “largest Magnifier”, with

nn

1 Baker (1740), p.506. The later description (Baker, 1753; p. 436),
though that usually quoted, gives far less detail.

320 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS”

a focal length of 3G in., magnified not 160 but 200 diameters
according to present-day reckoning—and so on throughout.

After a somewhat lengthy discussion, Baker reaches the
conclusion that Leeuwenhoek’s best microscopes, with which
he made his most considerable discoveries, “ must certainly
have been much greater Magnifiers than any in our Possession”’
—a conclusion which was then well founded.

I need not give Baker’s illustrations of a Leeuwenhoek
microscope—which have often been copied—nor their accom-
panying description,’ for more instructive data are now avail-
able: but I must here quote some other contemporary records
which throw more light on the present subject.

It is well known that Leeuwenhoek left many microscopes
with his daughter when he died. Apart from the 26 bequeathed
to the Royal Society there were some hundreds of others—
though their number is generally misstated. Maria did not
sell any of these instruments, but preserved them all her life.
After her own death (1745), however, they were put up for
auction and dispersed. Copies of the sale-catalogue (1747)
are still extant ; but the late Professor P. Harting, of Utrecht,
possessed a unique example which is of the greatest interest
and on which he has left some valuable notes’. I shall
therefore here translate his words verbatum, as they contain
information now unobtainable elsewhere. In 1850 he wrote: *

I have in my possession two copies of the catalogue
of Leeuwenhoek’s microscopes, drawn up for the auction
which took place on Monday the 29th of May, 1747.
One of these copies was probably used by the notary or
auctioneer at the time of the sale, for it is interleaved
with white paper on which the names of all the buyers,
and the prices fetched by the instruments, are carefully
recorded. The catalogue is got up rather more luxuriously
than is customary at the present day; for it is printed

1 Baker (1753), pp. 434-436; Plate XVII, figs. VII and VIII. (Dutch
edition [1770], pp. 453-456; Pl. XVII, afb. 7 & 8.)

* Haaxman (1875), p.38, has also described this catalogue, but adds
nothing material to Harting’s account.

* Het Mikroskoop, Vol. III, p.41 footnote. I have been unable to
discover what happened to Harting’s copies of the catalogue after his death.

LEEUWENHOEK’S MICROSCOPES 321

on heavy writing-paper, while a pretty allegorical copper-
plate engraving is placed at the beginning, along with
another displaying Leeuwenhoek’s portrait. The text is
in Dutch and Latin both.

From this catalogue it appears that Leeuwenhoek left
no less than 247 completely finished microscopes, each
provided with a lens, and generally also with an object ;
and, in addition to these, 172 lenses merely mounted
between little plates—419 lenses in all, therefore.
Among these lenses there are three made from so-called
‘Amersfoort diamond” (rock-crystal pebble)*; and of
one of the microscopes it is noted that its magnifying-
glass is ground from a sand-grain, while the object placed
before it is likewise a sand-grain. ‘T'wo microscopes are
specified as having two glasses, another three. It thus
appears that Leeuwenhoek also manufactured doublets
and triplets”; for, with his kind of apparatus, there can
obviously be no question of any proper compound micro-
scope. More than half of these microscopes (approxi-
mately 160) were mounted in silver. Among the rest
there are three made of gold—two of which weighed
10 engels* 17 grains, the third 10 engels 14 grains. One
of the former was sold for 23 florins 15 stivers, while both
the others were bought in. (This is probably the only
occasion on which microscopes have been sold by weight.)
The remaining microscopes were sold in pairs. The brass
ones fetched 15 stivers to 3 florins a pair, the silver 2 to 7
florins. The entire sale realized a sum of 737 florins and
3 stivers.t The names of the buyers show that all these

i.e. quartz. I know of no evidence to show that L. ever made
lenses from real diamonds—as is sometimes stated (e.g. by Nordenskidld,
1929 ; p. 165).

2 It now seems more probable that these were really double (or triple)
simple microscopes—i.e. 2 (or 3) single lenses mounted in the same frame
side by side—like the “double microscope” illustrated by Haaxman (1875)
p. 34, fig. 2A.

* An engels equals 32 grains: see p. 338 infra.

* About £61. 10s. in modern English currency.

21

1

322

LEEUWENHOEK AND HIS “LITTLE ANIMALS”

microscopes were purchased by Hollanders,' and it is
therefore surprising that one nowadays so seldom meets
with any surviving specimens of Leeuwenhoek’s instru-
ments in this country.

Elsewhere Harting has published a list of the objects

which Leeuwenhoek left fixed before his magnifying-glasses—
as mentioned in the sale-catalogue. Though they include
—like Folkes’s list—no protozoological or bacteriological
items, they seem sufficiently interesting to quote. According
to Harting, they were as follows: ”

Animal Objects

Muscle-fibres of a whale.

a 59 99 COdLish.

a ,, the heart of a duck.
Transverse section of the muscles of a fish.
Scales from human skin.
Crystalline lens of an ox.
Blood-corpuscles of a man.

Liver of a pig.
Transverse section of the bladder.
Bladder of an ox.
Papillae from the tongue of an ox.
Hair of sheep.

457 |, on DOAVEr.

» 9» elk.

wel Goss Dears

» out of the [human] nose.
Scale of a perch.

»” »” > sole.
Spinning-apparatus of a spider.

Thread [web] 999»
Sting ” 99 ”
Teeth » » ”
Hyes » ”

Spinning-apparatus of a silk-worm.

1 The names of all the purchasers (42 in number) have since been
printed in Harting (1876), p. 33.
2 Translated from Harting (1850): Het Mikroskoop, Vol. III, p. 465.

LEEUWENHOEK’S MICROSCOPES 320

Brains of a fly.
Optic nerves of a fly.
Tips of the feet of a fly.
Sting and sheath of a flea.
Feet » 9 99
HKyes of a dragon-fly.

» 99 beetle.
Sting of a louse.

MGM: 59 1 Sp of
Ovipositor ,, 5, aa
Red coral.

Section of oyster-shell.
Embryo oysters in a little [glass] tube.

Vegetable Objects

Transverse and longitudinal sections of elm-wood.

” ” ” ” » fir-wood.

»” ” ” »” »” ebony.

»” »” ” » »” lime-wood.
»” ” om) »” »” oak-wood.
” » ” ” » Clnnamon.
» » ” » »» cork.

” » ” 5) » rush.
Section of fossil wood.

Germ out of the seed of rye.

Vascular bundles out of a nutmeg.

Mineral Objects

Bits of white marble, rock-crystal, diamond, gold-leaf,
gold-dust, silver-ore, saltpetre, crystals, etc.

Harting was fortunately able to examine one of Leeuwen-
hoek’s few surviving lenses carefully: and as his tests are the
only recent ones made by an expert—so far as I am aware—I
must here note what he found. He reports* that the biconvex
lens which he studied was “really very good indeed”’, and
proved that its maker had attained “a very high degree of
proficiency in grinding extremely small glasses.” Its magni-
fying power was no less than 270 diameters [indicating a focal

1 Het Mikroskoop (1850), Vol. III, pp. 43, 44.

324 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

length of about 0°9 mm.]: and its resolution was so good that,
with suitable illumination, it was capable of resolving the 4th
croup of lines on a Nobert test-plate (7.e., a scale 10 » long
subdivided into 7 equal parts by parallel lines ruled with a
diamond on glass). In Harting’s opinion this was probably
the optical limit of Leeuwenhoek’s lenses: but the lens which
he studied was only one of hundreds, and some of the others
—now lost—may well have been superior.”

Leeuwenhoek himself has—to my knowledge ’—left us no
account of his particular procedure in making and mounting
lenses. Others published their methods,* but he never did.
How to grind and polish lenses for spectacles and telescopes
was common property, however, at the time when he wrote;
and it seems probable that he worked by the ordinary rules
and with the customary apparatus. If you had asked him
how to make a very powerful lens, of very short focus, he
would doubtless have told you that it could only be made by
the usual methods: but as such a glass would be much
smaller, and more convex, you would have to do everything
on a smaller scale, and pay more attention to details. If you
can make a good lens with a focus of 1 foot, then you can—
if you take pains, and know your job—make an equally good
one with a focus of +$5 of an inch. It is more difficult, and
takes longer; but that is all. It is a question only of the
time and trouble that you are prepared to expend. The
general methods of grinding and polishing lenses were no
secrets: and when Leibniz asked old Leeuwenhoek why he
did not educate a school of younger men in the art, he made
the following reply :”

1 Op. cit., Vol. I, p. 404.

2 The lens examined by Harting was in a microscope preserved, at that
date, in the physical collection at Utrecht. The instrument now in the
zoological collection of the same university is greatly inferior—its lens
having a focal length of about + in. (fide Mayall, 1886).

* Crommelin (1929), in his recent admirable essay on lens-grinding [and
lens-grinders] in the 17th century, is of the same opinion. On this subject,
he says, L. “has left us entirely in the dark’’.

* See especially Manzini (1660).

> Send-brief XVIII, pp. 168-9 [Epist. Physiol. XVIII, p. 167]. Letter
dated 28 Sept.1715. Not in Phil. Trans.

LEEUWENHOEK’S MICROSCOPES 325

To train young people to grind lenses, and to found a
sort of school for this purpose, I can’t see there’d be much
use: because many students at Leyden have already
been fired by my discoveries and my lens-grinding, and
three lens-grinders have gone there in consequence; to
whom the students have repaired, to learn how to grind
lenses. But what’s come of it? Nothing, as far as I
know: because most students go there to make money
out of science, or to get a reputation in the learned world.
But in lens-grinding, and discovering things hidden from
our sight, these count for nought. And I’m satisfied too
that not one man in a thousand is capable of such study,
because it needs much time, and spending much money ;
and you must always keep on thinking about these things,
if you are to get any results. And over and above all,
most men are not curious to know: nay, some even make
no bones about saying, What does it matter whether we
know this or not ?

In addition to Folkes’s and Baker’s and Harting’s des-
criptions there are many other brief accounts and figures
of Leeuwenhoek’s instruments. The first picture of his
“microscope” is that introduced into Verkolje’s mezzotint
(1686), in which Leeuwenhoek is depicted holding one in
his own hand (see Frontispiece). A similar piece of apparatus
is probably meant to be shown in the hands of the allegorical
personages represented in two of the engraved titles to his
works.' Baker (1753) gave, with his description, a couple of
poor diagrams which have been copied over and over again—
by Hoole (1807) and many others down to Disney (1928) and
Bulloch (1930) at the present day. Uffenbach (1754) also
pretended to portray ‘“‘ Leeuwenhoek’s microscope”; while a
small but excellent figure (from an unknown example) was
engraved on the title-page of the booklet by van Haastert
(1823). Other pictures—sometimes accompanied by descrip-
tions—are to be found in the works of Harting (1850),

1 See Ontled. & Ontdekk. (1686) = Anat. s. Int. Rer. (1687): Vizfde
Vervolg d. Brieven (1696) = Arc. Nat. Det. (1695). These engravings should
also be found (somewhere or other) bound up in all the Dutch and Latin
collective editions of L.’s letters.

“6

326 LEEUWENHOEK AND HIS “LITTLE ANIMALS”

Haaxman (1871, 1875), Mayall (1886), Locy (1910, 1925),
Sabrazes (1926), and divers other writers. ‘‘ Leeuwenhoek’s
microscope’”’ has even appeared in a recent film, in a modern
advertisement for a proprietary dentifrice, and in popular
periodicals—such as the Dutch illustrated weekly De Prins,
which lately published (38 January 1925) the best photograph
which I have yet seen.

Although Leeuwenhoek made and left many microscopes,
nearly all of them have long since disappeared. Not only have
those bequeathed to the Royal Society vanished without
trace, but even some of the few other examples mentioned
by Haaxman and Harting—still surviving in 1875—cannot
now be found. According to my friend Professor Crommelin
(1929a) only 8 specimens in all are now known to exist, 5 of
which are in Holland. Of these, 1 is in the Zoological
Institute at Utrecht, and 3 others were, until recently, in the
private possession of Mr P. A. Haaxman at The Hague: but
2 of the latter have now passed into the Historical Scientific
Museum at Leyden, and have thus become the property of the
Dutch nation.” (All three were exhibited at a congress in
Leyden in 1907. Cf. van Leersum, de Feyfer, and Molhuysen,
pp. 114, 115.) Iam informed that two other genuine instru-
ments are now in Germany—one in a well-known museum,
the other in the possession of an optical firm: but I have not
yet been able to verify these statements. I have also been
told* that the late Dr Henri Van Heurck, of Antwerp, had an
authentic specimen of Leeuwenhoek’s handiwork in his collec-
tion which was sold in 1914. The Nachet Collection (Paris)
also claims to possess one.* Neither in England nor America,

1 There seems to be a general suspicion—probably fostered by some
injudicious remarks of Saville Kent (Vol. I, p. 9, footnote)—that Baker, the
last man known to have handled these instruments, was in some way
responsible for their disappearance. This is entirely unjustifiable: for a
search through the Society’s records (made on my behalf by Mr A. H.
White, our learned librarian) has shown that we still possessed L.’s micro-
scopes long after Baker’s death. They vanished from the Royal Society’s
collection only about a century ago, and the few remaining records appear
to incriminate a very different person.

2 Cf. Crommelin (1929a).

* By Mr W. E. Watson Baker, who—with his father—valued the
collection before the sale.

* The Nachet Catalogue, I may remark, is grossly inaccurate in nearly

LEEUWENHOEK’S MICROSCOPES 327

however, is there any genuine specimen (so far as I have been
able to ascertain), though modern facsimile reproductions are
now in circulation in both these countries. These copies are
accurate, and some of them may before long be passed off as
authentic originals. More than one such exact facsimile was
made for the late Sir Frank Crisp, who preserved one example
in his private collection and presented another to the Royal
Microscopical Society of London (on 21 January 1914), in
whose rooms it can now be seen.’ Crisp’s own facsimile was
sold at Stevens’s in London on 17 February 1925, when
his collection was auctioned after his death.” Other similar
reproductions are also in existence. One was recently in
California, and a friend of mine (who saw it) states that its
owner assured him that he could obtain similar “‘ Leeuwenhoek
microscopes”’ at any time—for a price—from Holland. Be
this as it may, there are certainly facsimiles (and forgeries ?)
now on the market, and prospective purchasers should be on
their guard.

Most of the recent descriptions and pictures of “ Leeuwen-
hoek’s microscope” are based on the rather poor specimen
now preserved in the Zoological Laboratory at Utrecht. The
best account and figures*® of this instrument are, I think,
those of Mayall (1886): but as I am not wholly satisfied with
his or any other description or pictures (Mayall, apparently,
never saw the microscope which he described), I shall here
attempt to revise his version with the help of a few drawings
of my own. My account is based on personal examination of
three genuine specimens, one copy, and a study of all other
available data. I must point out, however, that my own
figures (Plate XXXI) were not drawn from any actual
instrument. They form a composite design—a generalized

2 ___ aa

all its references to L. (see Nachet, 1929). I have not seen the instrument in
this collection; but from the description and picture it appears suspiciously
like one of the recent copies of the Utrecht example.

1 Of. Disney (1928), p.160. This instrument is evidently a copy of
the original now in the Zoological Institute at Utrecht, and most of the
other copies appear to have been made from the same example. One such
has been figured recently by Becking (1924).

2 See the Catalogue of this sale, Lot 1.

* Woodcuts, made directly from photographs. These excellent figures
have recently been reproduced (as line blocks) by Disney et al. (1928,
Plate 1) without acknowledgement.

328 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS”

representation of ‘“‘a Leeuwenhoek microscope ’"—embodying
all the features common to the extant examples. I have
tried to show the mechanism as simply as possible and with
the fewest and most easily comprehensible drawings, because
I find all previous accounts incomplete, inaccurate, or difficult
to understand. Several describers, indeed, do not themselves
appear to have grasped the mechanism—either literally or
metaphorically. My drawings are based primarily on the
microscopes formerly in the possession of Mr P. A. Haaxman
(The Hague), whose daughter—Mejuffrouw S. A. E. Haaxman—
very kindly permitted me (on 29 June 1923) to take one of
these priceless little instruments to pieces, sketch the various
parts, and reassemble it. For the accuracy of my description
I rely chiefly upon the notes and tracings which I made on
this occasion. Unfortunately I have had no opportunity of
testing any of Leeuwenhoek’s lenses.

All Leeuwenhoek’s microscopes had an appearance like
that shown in Plate XXXI, fig. 1. Properly speaking, they
were not “microscopes” at all, but—as he himself usually
called them—simple “ magnifying-glasses”. Hach consisted
of a single biconvex lens (not a system of lenses); and the
mechanical parts were contrived not to focus this lens upon
an object lying on a fixed stage (as in a modern compound
microscope), but in order to bring a movable object into the
focus of the glass, which was itself fixed. It is important to
realize this fundamental point in the design, which is highly
original. It should also be emphasized that all these instru-
ments were very small—even smaller than my drawings.
They were generally made of the same metal throughout,
though different metals were used (brass, copper, silver, and
even gold occasionally): and the workmanship and finish
were none too good. Leeuwenhoek concentrated his attention
upon the optical part of his “microscopes” : and when he had
succeeded in grinding and polishing and mounting a good lens,
he evidently did not think it worth while to spend a lot of
time in finishing off its mechanical accessories, which were
made just.good enough for his purpose.

Fig. 1 (Plate XX XI) shows the whole instrument from the
back, as fitted up ready for use. Figs. 2 and 3 illustrate details ;
and ‘fig. 4 is a diagrammatic longitudinal section. These
drawings will, I hope, almost explain themselves— if carey
studied ; but I may add the following notes :

PLATE XXXI

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LEEUWENHOEK’S © MICROSCOPE ”’

For explanation see the text.

facing p. 328

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LEEUWENHOEK’S MICROSCOPES 329

The minute biconvex lens (J, fig. 4) was mounted between
two thin oblong plates of brass (or other metal). Towards
one end of each plate, at the same point in the middle line, a
concavity was ground or punched and a hole pierced in its
centre. When these apertures had been made to coincide
exactly, the lens was clamped between the plates, in the
concavities (as shown in fig. 4), and secured by four equidistant
rivets forming the corners of a square (see fig. 1) with the lens
at its centre. In other words, the rivets and the lens—in
surface view—formed a quincunx, the lens occupying the
central spot.

The two oblong metal plates’ with the lens thus mounted
between them constitute the essential optical part of the
instrument. Leeuwenhoek probably kept many of his lenses
so mounted, and fixed interchangeable mechanical parts to
them as required. These mechanical accessories— for focussing
the object before the lens-—are shown in the figures and have
been well described by Mayall in his Cantor Lectures (1886)
as follows: ‘“‘ The object is held in front of the lens, on the
point of a short rod, the other end of which screws into a
small block or stage of brass [whose peculiar shape is shown
from above in fig. 2], which is rivetted somewhat loosely on
the smoothed cylindrical end of a long coarse-threaded screw
[figs. 1, 4] acting through a socket angle-piece | fig. 3] attached
behind the lower end of the plates by a small thumb-screw
[s, fig. 4. Only the projecting end of this screw is visible
in fig. 1. It is furnished with a roughly-fashioned metal
washer above the angle-piece—shown in section in fig. 4].
The long screw serves to adjust the object under the lens in a
vertical direction, whilst the pivoting of the angle-piece [fig. 3]
on its thumb-screw [fig. 4, s] gives lateral motion. ‘The
object-carrier can be turned on its axis, as required, by
screwing the rod into the stage [by means of a metal knob,
shown in figs. 1 and 4. When the rod is rotated by moving
the knob, the object is not only turned on its axis but raised
or lowered by the screw passing through the block—thus
forming a sort of “fine adjustment” for the “coarse adjust-
ment” provided by the long screw]. For focussing, a thumb-

1 The brass lens-holding plates of the best Haaxman specimen measure
approximately 41 mm. by 18 mm.; but their sides are not accurately
parallel, and their corners are roughly rounded.

330 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS”

screw passes through the stage near one end [figs. 1, 2,4], and
presses vertically against the plates, causing the stage to tilt
up at that end; the fitting of the long screw-carrier (angle-
piece [fig. 3]) is such that the stage at the end is sprung
down somewhat forcibly on the brass plates, and it is against
this pressure that the focussing screw acts.”

As we have already heard, the object to be viewed was
either stuck directly on to the pin of the object-carrier, or
else it was first mounted in some way (¢.g.,on a small plate of
glass or mica, or between two thin glass plates like a modern
slide and coverslip, or in a capillary glass tube) and the whole
was then fixed and focussed before the lens. A “ microscope”
of this type, with a lens of very short focus and high magni-
fication, must have been extremely awkward to manipulate.
It would be necessary to place the eye almost in contact with
the lens, and it is not clear how Leeuwenhoek was able to
obtain the requisite illumination. The known magnifying
power of his best glasses was, of course, sufficient to enlarge
objects as small as blood-corpuscles (and even bacteria) to
visually perceptible dimensions—a fact which modern workers
with the compound microscope seem apt to overlook. With
the front lens of my 2 mm. apochromatic objective—having a
magnification of about 120 diameters—I can distinctly see
(using the light of a clear sky only) bacteria as small as
Bacillus coli in a stained film. But to see such organisms
alive in water, and with sufficient clarity to describe their
movements, is another matter. (My own eyesight, I should
note, is exceptionally good—probably but little inferior to
Leeuwenhoek’s.) Yet Leeuwenhoek not only knew how to
make lenses of adequate magnifying power and aperture and
resolution, and sufficiently free from spherical and chromatic
aberration, but he also understood how to obtain the necessary
visibility. He was able,in some way, to get the indispensable
contrast between the object and its background which we
now readily obtain by means of central stops, iris diaphragms,
or staining.

It appears to me certain, indeed, that Leeuwenhoek cannot |
have made his extraordinarily accurate observations on bac-
teria and protozoa by means of the apparatus just described
when used in the ordinary way. He had unbounded patience
and magnificent eyesight—as his works abundantly testify—

LEEUWENHOEK’S MICROSCOPES 331

but he could not perform miracles. Moreover, there is no
reason to suppose that he possessed any apparatus essentially
different from that which is now known. (Blanchard’s sug-
gestion (1868) that he destroyed his best instruments in his
old age “with the idea of continuing to appear to everybody
as an incomparable observer ”’, is. quite unjustifiable.) All the
evidence indicates that it was the method of using this appar-
atus which he ‘“‘ kept for himself alone’”’: his secret lay, as he
tells us repeatedly, in his “ particular method of observing.”
What can it have been? The answer is—to me—almost
certain, though I cannot prove from his own words (since he
tried not to give his secret away) that I am right. I am
convinced that Leeuwenhoek had, in the course of his experi-
ments, hit upon some simple method of dark-ground wllwmin-
ation. He was well aware, as we know, of the ordinary
properties of lenses; and he tells us himself that he used
concave magnifying mirrors and employed artificial sources
of illumination (e.g. a candle). Consequently, he may well
have discovered by accident—or even have purposely devised
—some method which gave him a clear dark-ground image.
Such a discovery—possibly inspired by observing the motes.
in a sunbeam—would at once explain all his otherwise inex-
plicable observations, without supposing him to have possessed
any apparatus other than that which we now know he had.
But no hint was ever knowingly given, in all his many letters
(so far as I have been able to ascertain), of what his “ par-
ticular method of observing” may really have been.
Nevertheless, there is, in a very early letter, a remark
which seems to me to substantiate my interpretation—though
one must, I think, be personally familiar with such things to
appreciate it properly. Writing about red blood-corpuscles in
1675, Leeuwenhoek (in reply to criticism) says :*
. . . but I can demonstrate to myself the globules [= cor-
puscles] in the blood as, sharp -and clean as one can
distinguish with one’s eyes, without any help of glasses,
sandgrains that one might bestrew upon a piece of black
taffety silk.

1 From Letter’ 9. 22 January 1675. To Oldenburg. MS.Roy.Soe.
Unpublished.

* The words I have here interpreted and italicized are, in the original,
“desantgens . . . diemen op een swart sijde taff ‘soude mogen werpen”’.

332 LEEUWENHOEK AND HIs “ LITTLE ANIMALS ”’

Taffeta (formerly taffety or taffata—a word of Persian
origin) is a name now applied to various coloured fabrics of
wavy lustre: but in earlier times it denoted a silken cloth of
uniform texture—when black, much used for mourning. It
should be remembered that Leeuwenhoek speaks here not
only as a microscopist but also as a draper; and he therefore
meant that he could see human red blood-corpuscles under his
microscope just as clearly as he could see sandgrains scattered
on a piece of the smooth black silk he sold in his shop. The
more I consider these words, the more am I convinced that
nobody could ever have thought of such a simile unless he
had seen red corpuscles under dark-ground illumination.
Their appearance by transmitted light is wholly different, and
could never suggest such a comparison. To my mind these
words furnish an almost conclusive proof that Leeuwenhoek’s
“particular method of observing very small objects” was
some simple system of dark-field lighting, used in combination
with his ordinary microscopes. It is idle to speculate on how
he may have achieved this result : it is sufficient to note that
such a supposition will easily explain all his otherwise inex-
plicable observations. (It readily explains, for instance, how
he was able to see flagella and cilia and spirochaetes and
micrococci with a magnification of only some 200-300 dia-
meters.) But as he himself would say, “I hand this notion
over to others.”

Leeuwenhoek’s apparatus for viewing the circulation in
the tail of an eel was fully described and illustrated by
himself.’ It is a peculiar instrument, designed for a special
purpose, and not his “‘ microscope”? proper—though it has
more than once been figured as such by later writers. I need
not consider it here. I may note, however, that one of these
instruments is now in the Leyden Museum (with some lenses
made and mounted for it by himself, and a copy by another
maker). Leeuwenhoek’s own figures” show that he sometimes
used the lenses of his “ microscopes’”—mounted between two
oblong metal plates, as already described—in fitting up this

1 Letter 66. 12 January 1689. To the Royal Society. Printed in Dutch
and Latin works, but not in Phil. Trans. The original is preserved among
the Boyle MSS. of the Royal Society.

* See especially fig. 8, on the plate accompanying this letter.

LEEUWENHOEK’S MICROMETRY 333

apparatus. His magnifying-glasses were evidently so designed
that they could be used interchangeably for ‘ microscopes ”
or ‘‘enchelyscopes”’, as occasion required, by adding the
appropriate mechanical parts.

I may also note here that Leeuwenhoek was one of the
first—if not the very first—to study the structure of solid
opaque bodies by means of sections. Some which he cut
with his own hand “by means of a sharp shaving razor ” are
still in existence. They were enclosed in a little packet
affixed to an early letter,’ and have remained intact to the
present day. According to his own description, they are
(1) “Cork”; (2) ‘‘ White of a writing pen” [parings from a
quill] ; (3) “ Bits of the optic nerve of a cow, cut crosswise ”’ ;
(4) “ Pith of elder.” He added the following suggestions for
looking at these objects :

: I would venture to recommend that, when one
of these sections has been brought upon the pin of a
microscope, you then hold the microscope towards the
open sky, within doors, and out of the sunshine, as though
you had a telescope and were trying to look at the stars in
the sky through it.

LEEUWENHOEK’S MicroMEtRY.—Before the invention of
micrometers it was extremely difficult to measure very small
objects under the microscope: their size could, indeed, be
only estimated, by reference to other objects of known dimen-
sions. On an earlier page” we have read Leeuwenhoek’s
own account of the way in which he assessed the probable
magnitude of various animalcules, but a few further notes are
necessary.

Leeuwenhoek took the inch_(of his land and period) as an
absolute unit for small measurements. A copper rule,’ with

1 Letter 4. 1 June 1674. To Oldenburg. MS.Roy.Soc. Partly published
in English in Phil. Trans. (1674), Vol. IX, No. 106, p.121. L. also sent a
copy of this letter to Const. Huygens, and this copy—now in the Leyden
library—has recently been printed in its original Dutch by Vandevelde and
van Seters (1925).

* See p. 201 seq., supra.

3 Referred to on p. 189 supra.

334 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS”

the inches subdivided into tenths, was his standard. Fortu-
nately, he had this engraved for one of his later letters,’ so
that it can now be measured. From the picture it appears
that his “ inch’”’ was approximately 26°15 mm., and therefore
slightly greater than the modern English inch (25'4 mm.).”
His own drawing of a cubic inch (p. 189 supra) confirms
this determination.

The commonest objects with which Leeuwenhoek com-
pares ‘“‘animalcules” are a sandgrain, a human red_blood-
corpuscle, a vinegar-eel, and a millet seed. He also used
other more or less verifiable measures, however, such as “a
hairsbreadth,” “‘the diameter of a louse’s eye,” “the bigness
of a hair on a louse,” etc. J may say a word on each of these.

Sandgrains are Leeuwenhoek’s common standard of com-
parison. At first sight it seems impossible to translate these
highly variable structures * into exact modern measurements,
but it is actually—from the information which he supplies—
quite feasible. He generally referred to two kinds of sand—
coarse and fine. A fine sandgrain, according to the letter
translated on p. 188, was about #5 inch in diameter : but else-
where‘ he states that 100 of his very small sandgrains, laid
end to end, equalled about an inch. This seems to be the
usual magnitude he had in mind—7.e., about 745 of an inch,
or (using his scale) approximately 2604. A coarse sandgrain,

according to his own statement,’ was about 35 inch in

1 Send-brief XXVIII, to Boerhaave. 28 September 1716. Also published
in Latinin Epist. Physiol. and Op. Omn. The plate faces p. 271 of the Dutch
edition, and p. 266 of the Latin.

2 The scale in the figure is 5 inches long, and is accurately delineated.
A fair average can therefore be readily obtained for 1 inch. But as the
actual engraving was made on copper, and the prints are on paper (which
was wetted, and then shrank somewhat), I have made my estimate from
4 different prints in my possession (which differ only very slightly from one
another). The mean for 1 inch (here given) is therefore derived from the
combined measurements of 20 printed inches.

3 Ty. said himself (Send-brief XLI, 26 Aug. 1717) that “as big as a grain
of sand” is an inaccurate expression, andit would be better to use a millet
seed or a mustard seed for comparison.

4 Letter 35, to R. Hooke. 3 March 1682. Published in Dutch and
Latin works.

> Letter 42, to the Royal Society. 25 July 1684. Published in Dutch
and Latin works.

LEEUWENHOEK’S MICROMETRY 335

diameter, and therefore some 870 ». These magnitudes seem
to agree well with all Leeuwenhoek’s inferences—so far as
I have been able to check them.

A Red Blood-corpuscle (of man) measures about 7°5 u
in diameter, and Leeuwenhoek’s frequent choice of this
structure as a standard of size has been amply confirmed by
all later microscopists. Even today we commonly see an
outline of a human erythrocyte inserted among drawings
of microscopic organisms as an indication of their relative
magnitude.

It may be remarked here that Leeuwenhoek himself had a
very good idea of the actual diameter of a red corpuscle, though
he could not express it exactly in terms of any micrometric
unit : for he notes in one place’ that he had satisfied himself
that 100 diameters of a red corpuscle amounted to something
less than that of a coarse grain of sand (which he had just
assessed at 35 inch). Consequently, he imagined the diameter
of a corpuscle to be rather less than 3500 of an inch—an~
astonishingly good estimate.”

The Vinegar-Hel (the nematode Anguillula aceti) is
assigned various sizes in the text-books. I have cultivated
and studied this worm at various times, and find that ordinary
large individuals (females) may measure anything from about
1200 to 1700 in length. “A full-grown eel such as we
see in vinegar’”’ is approximately 1°51um. long, and this agrees
quite well with all Leeuwenhoek’s references.

A Millet Seed is more difficult to appraise. There are
now many kinds of millet (Panicum miliaceum)—*a name
applied with little definiteness to a considerable number of
often very variable species of cereals, belonging to distinct
genera and even subfamilies of Gramineae”’.* I have measured

1 Letter 42, p. 32 of Dutch edition.

* This was pointed out by Harting in 1850 (Het Mikroskoop, III, 404),
and again by myself (1920)—in ignorance of his earlier annotation.
Haaxman (1875, p.56) makes the absurd mistake of commending L. for

estimating the diameter at so (instead of goo) of an inch.

3 Encyclopaedia Britannica, 11th ed. (1911). It is rather surprising that
“a, millet seed” is still so frequently referred to, as a standard of size, in
biological writings (especially text-books). I have asked many people how
big a millet seed is, but have never yet found anybody who could tell me
even approximately—including one distinguished person who had himself
used the expression as a descriptive term.

336 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

samples of modern “ brown” and “ white ” millet (commonly
sold for bird-seed) and found that the grains averaged 1°8 mm.
and 2:17 mm. respectively: but as they are not spherical,
their “diameter” is difficult to determine. In one place’
Leeuwenhoek estimates a green pea to have a diameter equal
to 4} millet seeds, while elsewhere” he says that a pea weighs
8 grains. On selecting a few fresh green peas of about this
weight (520 mg.) and measuring them, I found their diameters
‘to be rather less than lem. (But here again—as peas are
not round—it is impossible to express their diameter, or
“axis”? as he called it, with precision.) If Leeuwenhoek’s
millet had a diameter of about # of such peas, it must have
measured roughly 2mm. across. This agrees with my
estimates from modern millet, and does not seem to disagree
with any of his own statements. I assume, therefore, that
when he uses “a millet seed” as his standard, he means a
spherical body approximately 2 nm. in diameter.

A Hairsbreadth is estimated by Leeuwenhoek himself? as
equal to g3o of an inch (about 43°6 w on his scale). The hairs
measured were plucked from his wig—not his own head—and
human hairs are usually much coarser.”

The Eye of a Louse’ appears to be rather an indefinite
standard of size. I find, however, that it can be estimated
approximately. The eyes of Pediculus humanus corporis (the
louse which Leeuwenhoek particularly studied) have fairly
uniform dimensions in both sexes. They are not spherical;
but series of measurements made longitudinally and trans-
versely give closely similar mean diameters. The average for
‘an eye of a big louse’’ I have found to be about 70 u—ranging
from 64 » to 80 w. It can thus be said, with a fair approxima-
tion to the truth, that ‘‘a louse’s eye’ has a diameter 10 times
that of a human red blood-corpuscle. This is in good agree-
ment with Leeuwenhoek’s interpretations.

1 See p. 169 supra.

> See p. 214 supra.

3 See p. 189 supra.

+ Most of my own hairs, which are unusually fine, have diameters at

least twice as great. I have never seen a human hair (from the head)
measuring only 43 u in diameter; but I have made no extensive investigation
of this matter—being content with L.’s own statement.

> Of. p. 121 et alibi, supra.

LEEUWENHOEK’S MICROMETRY RB

A Hair on a Louse is a less accurate comparison: for the
setae on P. corporis vary greatly in diameter, in different parts
of the body. Moreover, they all taper to a point, so that their
sides are not parallel. Large hairs, I find, have a maximum
width of about 4 »: but smaller ones measure only 2°5 w or
even less. “The thickness of the hairs wherewith the body
of a louse is beset” I estimate—very roughly—to be something
more than 3 yp.

I can add little else to what Leeuwenhoek himself tells us
about his micrometry.' I may mention in conclusion, how-
ever, that he had some correspondence on the subject with
Dr James Jurin in the last year of his life. Jurin, in 1718,
invented” a new method of measuring small objects ; and in
1722 he wrote to Leeuwenhoek about it, and persuaded him
to try it. Leeuwenhoek did so, and his answering letter was
published.’ Though it is not generally known, Jurin’s own
draft (in English) of his letter to Leeuwenhoek is still extant.
It is an interesting letter, and its present owner* has kindly
allowed me to read and copy it: but asit has no bearing upon
Leeuwenhoek’s own methods, I need not print it here.

Finally, I may note that the we:ghts mentioned by
Leeuwenhoek, in various letters, sometimes furnish clues to
his measurements. We could, indeed, exactly determine some
of his small measures of length if we knew the exact equivalents
of his weights in modern units. We do not know, however,
how closely his “grain” or “ounce” agree with modern
weights of the same name; though fortunately he recorded his

1 Tt should be noted that an earlier attempt to evaluate L.’s measure-
ments was made by Muys (1741; p.332, note 72). His words are worth
consideration ; but his estimates can hardly be regarded as satisfactory at
the present time, so I shall not discuss them here.

2 See Jurin (1718). His method was simple and ingenious. It consisted
in closely winding fine hairs or silver wire on a needle, along a measurable
length, and then determining the diameter of the hair (or wire) by counting
the number of turns in that length. The diameter of the filament being
thus ascertained, it was cut into small bits and strewn among the objects to
be measured, whose size was estimated (under the microscope) by comparison.
In this way Jurin determined the diameter of a human red blood-corpuscle
to be gz'z5 inch (a very close approximation).

3 Phil. Trans. (1723), Vol. XXXII, No. 377, p.341 (MS.Roy.Soc.
19 March 1723).

4 Mr A. K. Totton, a kinsman of Jurin and a former pupil of mine.
22,

338 LEEUWENHOEK AND HIS “LITTLE ANIMALS ”’

own “table of weights ” himself, so that we know their relative
values. Writing to Tschirnhausen * in 1699 he says:°

Over here we divide a pound |pont] into 16 ounces
[oncen], and each ounce into 20 engels,* and each engels
into 32 grains [asen]; and consequently, then, a grain
[aas] is todz0 Of a pound.

Tt is thus clear that Leeuwenhoek’s “grain” (aas), which
was gto of his ounce, can hardly have been identical with our
modern grain (4373 = 1 ounce, or 7,000 = 1 Ib. avoirdupois).
Wherever I translate “asen” as “ grains”, in the foregoing
pages, it is merely for want of any other term ; and the reader
will therefore please bear in mind that Leeuwenhoek’s * grain ”
was only approximately the weight nowadays called by the
same name in English (1 grain=0°065 gramme). But these
are problems for the expert metrologist—not for a poor
protozoologist or bacteriologist—and their further discussion
is beyond my competence.

(iv) LEEUWENHOEK’S DWELLING

The tragicomical history of Leeuwenhoek’s house in Delft
has never yet been fully related, but it deserves notice here
for several reasons. ‘These are the facts, so far as I have been
able to ascertain them. My information is derived chiefly
from Soutendam (1875), Haaxman (1875), Harting (1876),
Bouricius (1924, 1925), and an anonymous article” recently
published in the Wereldkroniek—supplemented by a few
personal observations and inquiries made on the spot in 1923.

In September 1875 an international celebration of “the
200th Anniversary” of Leeuwenhoek’s discovery of the
“Infusoria’”’ was held at Delft. (Harting [1876] records the
events which led up to this congress.) The fixing of the date
of the original discovery on September 1675 was, as we now

1. W. von Tschirnhausen (1651-1708), the well-known German
mathematician.

2 Letter 120, dated“. . . 1699.” Published in Dutch and Latin
collective works. See p.131 of Dutch edition.

* There is no English equivalent of this word.

4 See Anonymus (1909).

LEEUWENHOEK’S DWELLING 339
know, incorrect: nevertheless, the “ anniversary”? was duly
celebrated on the date erroneously determined—to the evident
satisfaction of all participants. By that time everyone had
forgotten where Leeuwenhoek had lived: but the then
archivist of Delft (Mr J. Soutendam) endeavoured to find
out, and he finally pitched on an old house standing at
the corner of Oude Delft and the Boterbrugstraat (not
‘“ Botersteeg”’, as Haaxman called it). An “ astrolabiwm” or
“planetarium” still present by the doorstep (figured by
Soutendam, 1875) was taken to confirm his identification of
the site—this bit of “scientific apparatus” presumably indi-
cating that the house in question had once been occupied by
a man of science. Even at that date (1875), however, the
house itself was, by all accounts, much restored and altered.

As Leeuwenhoek’s habitation had been thus identified, the
“anniversary ’’ celebrations included a visit of the delegates
en masse to this hallowed spot. The tenant of the house at
that time (Mr J. B. A. Muré) received them graciously: he
also allowed a stone memorial slab to be affixed to the front
of his residence, and bound himself legally to be responsible
for its future preservation. (The agreement is printed in
Harting, 1876; p. 89.)

So far so good. Some years later, however, the tenant of
the house died, and it passed into the hands of a builder at
The Hague who inconsiderately ordered it to be demolished.
By that date (1892) everybody had, apparently, forgotten all
about Leeuwenhoek again: but when the house came to be
pulled down, the stone block bearing his name, and the
‘‘ planetarium ” by the steps, were noticed. They were there-
fore preserved, consecrated with the seal of the municipality,
and deposited (on 3 December 1892) in the Municipal Museum
at Delft—where they now repose. (The memorial tablet is
an oblong block of white marble bearing the words Antony
vAN LEEUWENHOEK/MDCLXXV—MDCCCLXXV in gilt
capitals. The “planetarium” is a decorative iron railing
bearing no obvious resemblance to any scientific instrument.)
The site occupied by the house was not built on, but was
converted into a playground for the girls’ school adjoining
(the Meisjeshuis, erected in 1760); and again everything was
forgotten.

Some 17 years later, a local society called “ Delfia”—
concerned with the improvement of the town, and the preser-

340 LEEUWENHOEK AND HIS “LITTLE ANIMALS”

vation of its antiquities—realized that something ought to be
done to commemorate Leeuwenhoek in the place of his birth,
residence, and death. They therefore instituted a competition
in which artists were invited to submit designs for a suitable
memorial. ‘The winning entry was duly accepted and erected
—a bronze shield,’ showing a bas-relief bust of Leeuwenhoek
(modelled on Verkolje’s portrait) with a Dutch inscription,
executed and signed by J.C. Schultsz. It is still stuck on the
railings surrounding the school playground, where it was
affixed in 1909. Apart from his tomb, this is still the only
monument to Leeuwenhoek in Delft.

But more recent research into the town archives—made
by a later and more critical archivist, the late Mr L. G. N.
Bouricius—has proved that Leeuwenhoek never lived on the
spot where his modern bronze effigy with its false inscription
now hangs. His real residence was in a neighbouring street
—the Hippolytusbuurt—and has long since vanished without
trace. Consequently, all the belated local endeavours to
commemorate Leeuwenhoek have been futile. It is certain
that he never lived on the spot where the delegates were
thrilled in 1875, and where his memorial now incongruously
stands: nor did he make the supposed discoveries in the year
therein alleged. His own house—where he lived and laboured
and died—was in a different street, and has long since been
destroyed by his forgetful fellow-townsmen. ‘The railings
adorning another man’s doorstep—now preserved in the
Municipal Museum of Delft—are a worthless object which
would surely have excited his derision.

Before the celebrations of 1875 were held in Delft, invita-
tions were issued by the organizing committee to every body
and everybody likely to be interested. Yet England—almost
alone—made no response. The Royal Society, indeed, not
only sent no delegate, but even failed to acknowledge their
invitation: and England and London and the Royal Society
thus placed themselves—to quote Harting (1876)—“on a
level with Spain and Portugal and Greece.” We ought,
undoubtedly, to have taken some part in commemorating
Leeuwenhoek’s discoveries, with which we were so intimately
concerned: yet our disgrace is now, perhaps, mitigated by

1 Figured in the anonymous article in the Wereldkroniek (1909). A
plaster cast is also preserved in the Museum at Delft.

LEEUWENHOEK’S DWELLING 341

the accidental circumstance that no Englishman or Fellow of
the Royal Society was present at the farce enacted in 1875 at
‘* Leeuwenhoek’s house, where he discovered the Infusoria in
1675”. But the whole affair is deplorable, and the less said
about it the better.

The comedy of errors associated with ‘ Leeuwenhoek’s
house ” is unhappily paralleled in the history of his birthplace.
About ten years ago, Mr Bouricius succeeded in discovering
the place where Leeuwenhoek was born—a house in the
Oosteinde of Delft, at that date still erect but used as a
warehouse by a hide-merchant named Roes. Bouricius (1925)
published a picture of this building, and with his kind assist-
ance I had it rephotographed in 1926. (See Plate II.’) But
in February, 1929, Mr Bouricius unfortunately died: and
later in the same year, when Dr Schierbeek was about to
propose to a Dutch scientific gathering’ that a commemora-
tive tablet should be placed on the house, he found that it
had just been pulled down—to enlarge the playground of
another children’s school !

It will thus be seen that the house in which Leeuwenhoek
was born, the other house in which he lived and worked
and traded and died, and even the house in which he is
now erroneously supposed to have resided, have all been
demolished. Delft, Holland, England, London, the Royal
Society, and everyone else in every land, may therefore all be
censured for having done nothing to preserve Leeuwenhoek’s
bodily connexion with the world.

But it is needless to bewail the hard fact that such
material relics of Leeuwenhoek’s existence have been thus
wantonly destroyed. His own works are a monumentum aere
perennius which no vandal or house-breaker or Fellow of the
Royal Society can ever annihilate. For my own part, I feel
no sorrow when I reflect that the site of his own dwelling
is now occupied by an obscure modern shop: and I almost
rejoice that the place where he was born, and the ground

1 This photograph has already been published, unfortunately, by Dr
Schierbeek (1930), though it was taken at my expense for the present work.
I note this lest I be accused of borrowing his illustration without
acknowledgement.

2 Genootschap voor Geschiedenis der Genees-, Natuur- en Wiskunde.

“cc

342 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

whereon he is wrongly supposed to have lived, are both now
open spaces where little Dutch children can play in the sun.
I even find something appropriate, poetic, and comforting in
these ‘‘ inscrutable dispensations of Providence.”

(v) LEEUWENHOEK’S DRAUGHTSMEN

It is well known that most of the illustrations accompanying
Leeuwenhoek’s letters were not drawn by his own hand. He
tells us himself that he was a poor draughtsman, and therefore
employed more skilful artists to make his figures.’ There are
several references to this subject in his published works ; but
perhaps the most explicit expression is to be found in an early
unpublished letter, wherein he says—in answer to Oldenburg’s
complaint that his drawings were not sufficiently clear—that
he sees with the utmost clarity all that he describes, but then
adds :°

Yet I am to blame, because I can’t draw; and secondly,
because I am resolved not to let anybody know the
method that I use* for this purpose: and so I just make
only rough and simple sketches with lines, mostly in
order to assist my memory, so that when I see them I
get a general idea of the shapes: besides, some of the
forms I see are so fine and small, that I don’t know how
even a good draughtsman could trace them, unless he
made them bigger.

Many of the original drawings sent with the letters to the
Royal Society have been preserved. They are, for the most
part, of no great artistic merit, and differ in minor details
from the published engravings. This is, in the main, because
the originals were usually drawn with red or black chalk, or
pencil (exceptionally with ink or in colour), and were often
reduced in size by the engraver. All variations are readily
explicable by the difference in technique—the soft line made
with red crayon on paper being impossible to render exactly
by the hard line of the burin on metal. On the whole, the

1 Cf. Letter 2, p. 42 supra.
2 Translated from Letter 11. 26 March 1675. To Oldenburg. MS.Roy.Soc.
* je, in handling the microscope—as is evident from the context.

LEEUWENHOEK’S DRAUGHTSMEN 343

engravers dealt faithfully with their prototypes: and I
fancy that the average modern editor, if drawings such as
Leeuwenhoek’s originals were submitted to him in illustration
of a present-day paper, would return them to the author with
a note saying that they were “not suitable for reproduction”.
I have, indeed, been compelled to act on this principle myself :
the original drawings, en sanguine on discoloured and yellowish
paper, illustrating the letters on Anthophysa and the protozoa
on duckweed, are still extant; but I cannot reproduce them
here—for technical reasons—and have had to use the
engravings originally made from these drawings instead.

A few “rough and simple sketches ’’—mostly on the mar-
gins of the MSS.—were evidently the work of Leeuwenhoek
himself’: because careful examination shows that they
were drawn with the same pen and the same ink as the
accompanying autograph handwriting. They bear out his
own statement that he was no artist.

In Leeuwenhoek’s letters I have been unable to find any
mention of the name of the draughtsman—“‘de teijckenaer’’, or
“the limner’”’ as Hoole always calls him—who made his
illustrations for him. (He is frequently mentioned, but never
by name.) It is unlikely, indeed, that all the drawings were
executed by the same artist, for they were made at intervals
during some 50 years; and there is no reason to believe that
Leeuwenhoek’s longevity was characteristic of all citizens of
Delft at that period. It seems to me certain, therefore, that
more than one hand must have participated in the illustration
of his discoveries.

It is generally supposed that Leeuwenhoek’s draughtsmen
are unknown. Nevertheless, there is at least one important
record bearing on this subject which seems to have been
overlooked. In Boitet’s book on Delft (1729; pp. 790-91) we
are told of a certain Thomas van der Wilt (born 1659”), who
was ‘‘a fine painter and a good poet,” and who was a pupil of
Johannes Verkolje. It is said by Boitet that he settled in
Delft, and there found plenty of work as a portrait-painter and
otherwise; and “ By his wife Johanna Biddaff he had a son,

1 The cube illustrating the argument in the letter to Const. Huygens
(p. 189 supra) is one as these: and the pepper-tube (Plate XXII) is
another.

* He died at Delft in 1733 (fide Bryan, 1905).

344 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

called Willem, who made such progress in drawing, through
his father’s instruction, that there were few who could match
him. Nearly all the plates in the celebrated work of Mr.
Leeuwenhoek were marvellously drawn from life by him
through magnifying-glasses. .... But hediedin the flower
of his life on 24 January 1727, at the age of 35.”

There is no reason to doubt the truth of this story—
published only two years after Willem’s death in his home
town: but it is impossible to believe that Willem van der Wilt
drew “nearly all” (meest alle) Leeuwenhoek’s figures. If he
died aged 35 in 1727, he must have been born in 1691 or 1692;
and consequently he could have drawn none of the illustrations
for the letters written in the XVII Century. He probably
made the illustrations of the Send-brieven: but he could not
have been responsible for any others—save some of those
reproduced between 1700 and 1712 in the Phil. Trans. The
pictures of vorticellids and rotifers published at the beginning
of the XVIII Century may perhaps have been drawn by hin,
and it may well have been Willem who made the recorded
remark about their surprising “ wheelwork”’’.* But he must
have been a mere child at the time.

Whilst there is thus good reason to believe that
Leeuwenhoek’s last letters were illustrated by Willem van
der Wilt, there seems to be no direct evidence to show who
drew the figures for the earlier ones. Nevertheless, it seems to
me probable that some of them may have been drawn by his
father Thomas. If we consider all the evidence furnished by
Boitet, it appears to me highly suggestive. Very briefly, it is
as follows: (1) Thomas van der Wilt was an artist living in
Delft at the time when Leeuwenhoek wrote his early letters.
(2) His son was employed by Leeuwenhoek to illustrate his
later letters. (3) Thomas himself must therefore have been
known to Leeuwenhoek.’ (4) He (Thomas) earned a good
living in Delft not only by painting portraits, but also by
exercising his artistic abilities in other ways. (5) Thomas’s
father, though not a native of Delft, was a linen-draper—the
trade which Leeuwenhoek himself engaged in. (6) Thomas

* Cf. p. 279 supra.

2 This is confirmed by the cireumstance—mentioned a little later—that
Thomas was responsible for some panegyric verses elucidating the allegorical
title-page of the Send-brieven.

LEEUWENHOEK’S DRAUGHTSMEN 345

was a pupil of Verkolje—the artist who painted Leeuwenhoek’s
portrait.

What could be more likely, therefore, than that
Leeuwenhoek employed Thomas van der Wilt to draw the
pictures for some of his earlier epistles? When all the
circumstances are taken into account, this seems to me to
be something more than a plausible guess at the identity of
one of the original draughtsmen.

But Leeuwenhoek must have known other artists who
lived in his native town, and the evidence in favour of Thomas
van der Wilt is clearly not conclusive. Among Leeuwenhoek’s
acquaintances we must include, for example, that incomparable
painter Jan Vermeer. He was born in the same year as
Leeuwenhoek, in the same place, and at almost the same
hour (their baptisms are registered on the same page), and
lived and worked all his life in Delft—of which he has left us
one of the most beautiful pictures in existence (see Plate VII).
Moreover, we know that, on Vermeer’s untimely death in
1675, Leeuwenhoek was appointed as his executor.’

I must note, in conclusion, that Thomas van der Wilt once
painted a portrait of the poet Hubert Poot (1689-1733), who
wrote Leeuwenhoek’s epitaph ; and an excellent engraving of
this picture, by Houbraken, was prefixed to Poot’s collected
Gedichten (Delft, 1722)—reproduced here in Plate XVI.
I have seen no other specimens of Thomas’s artistic work,
but according to Boitet and others he also painted the
Rev. Mr Gribius—Leeuwenhoek’s minister, who announced
his death to the Royal Society (see p. 93 supra). The only
sample of Thomas's poetry which I have seen is the poem
explaining the engraved title-page—‘ Op de Titel-prent’’—
of Leeuwenhoek’s Send-brieven (1718: not printed in the
Latin edition [Epist. Physiol.]|, 1719).

For my part, I accept Boitet’s evidence that Leeuwenhoek’s
later letters were illustrated by Willem van der Wilt, and
I incline to the view that some, at least, of the earlier ones
were illustrated by his father Thomas. But the subject
obviously demands further research, which I must leave to
future students possessed of the time and opportunities
requisite for pursuing inquiries of this character.

1 Vide p. 35 sq., supra. It is noteworthy also that L.’s microscopes
were ultimately auctioned in the chamber belonging to the artists’ Guild of
St. Luke—of which Vermeer was sometime “ Master ”’.

6e

346 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

(vi) THE PORTRAITS OF LEEUWENHOEK

Several “portraits of Leeuwenhoek” are still extant.
They were made at various dates by various artists, and the
following fragmentary notes upon them may be of interest—
information on this subject being somewhat difficult to obtain,
and not having been previously collected.’

(1) By JoHANNES VERKOLJE (1650-1693 : lived at Delft
1673 till his death, and is buried there. Cf. v. Riemsdijk,
1921, p. 281). There are two portraits of Leeuwenhoek by
this artist :

(a) An otl-painting. (See Plate XI, opposite p. 49 of
the present work.) Dated 1686 (fide Moes, 1905). Three-
quarter length, showing Leeuwenhoek seated at a table;
wearing a golden-brown robe, a wig, a knotted white necker-
chief, etc. Head turned to left of picture (7.e. to his own
right), knees to right. On the table a globe, an ink-stand
with a quill pen, the sealed diploma of the Royal Society, a
small pair of compasses, and a sheet of paper bearing a
drawing of acircle and some indistinct figures. (The drawing
appears to be that here shown in text-fig. 38, p. 202.) In
his right hand he holds another pair of compasses.” He
is depicted with a fresh complexion and clear blue eyes.
An opening at the right in the dark background shows
a glimpse of a distant landscape with a winding river
(“perhaps the Thames” according to Haaxman—but why
not the Maas?).

This painting was formerly in the possession of Dr C. H. W.
van Kaathoven of Leyden (Haaxman, 1875, p. 177: Harting,
1876, pp. 117-119). On his death it was purchased (19 June
1879) by the Rijksmuseum, Amsterdam, where it now hangs
(Room 273, No. 2521). Cf. Moes (1905, p. 12); v. Riemsdijk
(1921, p. 281). This isthe prototype of most of the published
portraits. It has been reproduced in recent times by
Crommelin (1926), van Seters (1926), and others, while

1 Since this was written a short article on the same subject has been
published by de Lint (1931)—too late for its contents to be discussed here.

2 A little passer similar to this, and once belonging to L., is still (or was
in 1923, when I saw it) in the possession of Mr P. A. Haaxman at The
Hague.

PORTRAITS OF LEEUWENHOEK 347

Haaxman had it lithographed'—by A. J. Wendel, not very
successfully—as a frontispiece for his biography (1875).

(b) A mezzotint engraving. (See the Frontispiece.) This
differs from the painting chiefly in the following particulars:
the head is turned to the right, knees to the left; and
Leeuwenhoek holds a microscope in his left hand (not com-
passes in his right). The whole picture is, in fact, reversed.
On the table, instead of the diploma, there is a spray of oak-
leaves with galls” on them, and a large magnifying-glass
with a handle. A curtain hangs behind the head, and the
distant landscape is missing. Below is engraved a Dutch
inscription with some verses signed “‘ Constanter ” (the pen-
name of Constantijn Huygens pater). The mezzotint is
signed “J. Verkolje pina. fec. et exc. A°. 1686.”* (This is
important, as it confirms the date of the painting.)

Several prints, at least, of this engraving are in existence.
Dr van Kaathoven, of Leyden, formerly possessed one, which
afterwards passed into the possession of Mr P. M. Beelaerts,
who in turn bequeathed it to the town of Delft." (It is now
in the Gemeentemusewm.) But the best impression which I
have seen is in the private collection of Mr George H. Gabb
(London), from whose copy my frontispiece has been repro-
duced. Other reproductions of the mezzotint (from other
originals) have previously been published in Opuscula Selecta
Neerlandicorum, Vol. I (1907); by Locy (1910, p. 79) and
Cole (1926, frontispiece); and in the Deutsche Medizinische
Wochenschrift (1911; No. 22, supplement). This last plate—
included in that journal’s ‘‘ Bildersammlung aus der Geschichte
der Medizin’’—is a fine large half-tone reproduction, but bears

1 This poor lithograph has unfortunately been copied (instead of the
equally accessible original) by several well-meaning popular writers—such
as Baumann (1915) in Holland, and Mrs Williams-Ellis (1929) in England.

2 Letter 50, 14 May 1686 (published in Dutch and Latin works) contains
a description of L.’s observations on oak-galls, and its date affords confirmation
of the date of the engraving.

3 Not 1685, as stated by Haaxman (1875, p. 187).

4 Of. Haaxman (1875) and Veldman (1898, p. 74). I have seen this
impression, which is fairly good.

* I am greatly indebted to Mr Gabb for his permission to copy the
original in his collection, and for the trouble which he has taken to insure
its accurate photographic reproduction.

348 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”’

a ridiculous biographical note (signed ‘“‘ Pagel’’) on its back.
The original picture is therein hesitatingly attributed to
“J. Veikolpe”’, and “Anton” van Leeuwenhoek is called a
‘well-known precursor of Robert Koch, in so far as the
discovery of the infusoria is due to him.”

It seems obvious that Verkolje first made his portrait of
Leeuwenhoek in oils, and shortly afterwards (in the same
year) himself engraved it in mezzotinto. The artist evidently
copied his own painting directly on to the copper plate (which
accounts for the figure being reversed in the printed engraving),
and in doing so made several minor alterations or improve-
ments—appropriately substituting a microscope for the
compasses originally held in the hand, but failing to notice
that he ultimately made Leeuwenhoek appear left-handed !
The mezzotint by Verkolje is probably the best of all portraits
of Leeuwenhoek: and that it was an excellent likeness is
attested by the verses written on it by Const. Huygens.

There are several references to this mezzotint by
Leeuwenhoek himself in unpublished passages in his letters.
Apparently the Royal Society wrote, about the beginning of
1694, to ask him for his portrait. In his reply he says: ’

I haven't any of my pictures; and furthermore, the
plate has been printed off, and the plate-maker, who was
also the printer and painter,” is dead. But if I can get
one at our approaching annual fair, at which time many
art-dealers come to our town, I’ll not neglect to let you
have what you ask for.

Later in the same year he wrote again: °

I couldn’t find any copies of my portrait, in mezzotinto,*

for sale by any of the printsellers at our annual fair: but
at last ’'ve gotten six copies from a bookseller in another

1 Translated from Letter of 26 May 1694. To R. Waller. MS.Roy.Soc.
Unpublished.

2 Referring to Verkolje, who died in the previous year.

3 From Letter 84. 14 September 1694. To R. Waller. MS.Roy.Soe.
Published in Dutch and Latin printed works, but with the passage here
translated entirely omitted. Not in Phil. Trans.

* inde swarte konst MS.

PORTRAITS OF LEEUWENHOEK 349

town, which I dispatched a fortnight ago to London by
Skipper Richart Houlatson, with the address: For the
Secretary of the Royall Society at Gresham Colledge,
without any further inscription.

The Royal Society failed to acknowledge the receipt of
these letters and pictures (and also of other letters from
Leeuwenhoek received at that time), and two years later we
find him writing again *:

When I learnt that several Fellows were wishful to
have two or three copies of my portrait, printed in
mezzotinto, . . . I couldn't remain idle, but made
every effort to satisfy them; and finally I obtained six
prints (as the plate had been printed off). These mezzo-
tintos, as also my Latin book, I sent to London, and
addressed them, as I’ve been wont to do, to Gresham
Colledge: to all which letters I got no answer

What happened to these six prints is not now known.
They have all disappeared from the Royal Society’s collection,
and the Society now possesses only a single mutilated copy of
the mezzotint acquired at a much later date.

All the well-known engraved portraits of Leeuwenhoek are
derived from Verkolje’s oil-painting. The best-known, and
most often reproduced, is the excellent copperplate engraving
by A. de Blois prefixed to the Dutch and Latin collective
works (Brieven and Opera Omnia). It first appeared as a
frontispiece to the Vervolg der Brieven (1687), with a Dutch
inscription: afterwards, with Latin lettering, in Arcana
Naturae Detecta (1695). Various copies of this copy have
also been made—in line, stipple, mezzotint, and by modern
photographic processes. At least one early engraving was

1 The words “For . . . Colledge” are thus in English in the MS.
(The rest, of course, is in Dutch.)

2 From Letter 102. 10 July 1696. To the Royal Society. MS.Roy.Soc.
Published—with omission of the passage here translated—in the Dutch
and Latin printed works: English extract in Phil. Trans. (1696), Vol. XIX,
No. 221, p. 269 (from which the passage isalso absent). This letter actually
contains a protest against the Society's failure to acknowledge 8 of L.’s
communications (Letters 77 to 84)—a discourtesy which caused him to
start sending his observations to other people instead.

350 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS”

reproduced in colours. The best steel-engraving (copied from
de Blois) is that by A. Smith,’ prefixed to Hoole’s Select
Works (Vol. I, 1798): but another good one—probably copied
from Smith’s, but with the head turned to the right (as in the
original mezzotint)—was made by J. Chapman and published
by G. Jones in 1813. All these reproductions show
Leeuwenhoek’s head only, in an oval frame with more or
less added decoration.

Regarding Anker Smith’s engraving (in Hoole) the
following points should be noted. Although it bears an
extract from a Dutch letter printed in 1696, and is marked
“ Painted by I. Verkole”’, it was almost certainly copied from
the engraving by de Blois accompanying the Latin Arc. Nat.
Det. The oval frame bears the words: “ANTONIUS A
LEEUWENHOEK DELPHENSIS, R.8.8. AET. LXIII.
MDCXCV.” Both age and year are entirely wrong, and
consequently this circumscription has already led to mis-
understanding. JI can only suppose that Smith (or Hoole)
wrongly took the date of the Arc. Nat. Det. (1695) as that in
which de Blois’s engraving was made; and that the age of 63
was then inferred from this error. Anyway, there can be no
doubt that Smith’s engraving was ultimately derived from an
original made in 1686 (not 1695), which portrayed
Leeuwenhoek at the age of about 54 (not 63).

Verkolje’s portraits have been copied and recopied over
and over again, and terribly travestied and perverted in the
process. ‘The die of Leeuwenhoek’s own seal * was admirably
incised from the mezzotint: the modern bronze effigy’ of
himself, now suspended in Oude Delft, is also based—less
successfully—on Verkolje’s originals. Moreover, there are
contemporary tiles and pottery of Delft-ware bearing
Leeuwenhoek’s supposed simulacrum “ after Verkolje” (a very
long way after). I have seen two samples of these—a plate
and a plaque—now in the Riyksmuseum; and Haaxman and
Harting mention others. I have also seen a present-day
descendant of Verkolje’s pictures—showing “the man who

1 Anker Smith (1759-1819), a once celebrated engraver of small plates
for book-illustration. He was elected.A.R.A. in 1797.

2 Ct. p:. 360.
3 Cf. p. 340 supra.

PORTRAITS OF LEEUWENHOEK 351

first saw a microbe”—in an English children’s magazine,
and a comic reconstruction recently (1931) used to advertise
an American proprietary tooth-paste in India: but the last
stage in degradation has surely been reached in the caricature
imprinted on the covers of the current American Abstracts of
Bacteriology (Vol. I issued in 1917) and some other publications
of the Society of American Bacteriologists.

(2) By Nicotars Mass (1632-1693: from 1673 to 1693
at Amsterdam, where he died and was buried). According
to C. H. de Groot (1916: Vol. VI, pp. 530-531) there are
two portraits of Leeuwenhoek by Maes. The first (No. 202,
de G.) is an oil-painting now in the National Gallery, London
(1921 Catalogue, No. 2581). This picture was formerly owned
by Mr George Salting, the Australian art-collector, and was
bequeathed to the Nation in 1910. It is undated, and depicts
an old man “in full face. His right hand is raised, grasping
his robe. He has long hair, a moustache, and a pointed beard
on his wrinkled face. |He wears a black robe and a white
shirt.| At the back is a curtain, with a column in shadow to
the right’ (de Groot). This is a very fine painting, but it is
certainly no portrait of Leeuwenhoek. It shows a man totally
unlike the sitter for Verkolje’s portraits, and there is no
evidence whatsoever that it depicts our Antony. In 1923
I called the attention of the then Director of the National
Gallery (Sir Charles Holmes) to this misidentification: and on
looking into the matter for himself he agreed that ‘‘ there is
no just ground for identifying the portrait . . . as a portrait
of Leeuwenhoek.” He informed me further that the picture
was first labelled “ Anthony van Leeuwenhoek, F.R.S.” after
it left the Salting Collection—by whose authority is not now
known.” Its label has consequently now been changed to
“ Portrait of a Gentleman”. De Groot blundered badly when
he accepted this painting as a portrait of Leeuwenhoek.

According to de Groot there is also another portrait (like-
wise undated) by Maes. It is described as follows: ‘‘ 202a.
ANTHONI VAN LEEUWENHOEK.—In a dark red coat trimmed
with fur. His long hair falls on his shoulders. 28 inches by
24 inches. Sale.—Lady Anna Chandos-Pole and others,

1 See Anonymus (1927).
2 Letters dated 8 & 10 May 1923.

352 LEEUWENHOEK AND HIS ‘“ LITTLE ANIMALS ”

London, July 19, 1914. No. 106” (de Groot, 1916: Vol. VI,
p.531). Whether this is a genuine portrait or not I do not
know. I have been unable to trace it further. I can only
add that according to Art Prices Current, 1913-1914 (Vol. VI,
pp. 307, 505), the picture was not the property of Lady Chandos-
Pole, but belonged to Maj.-Gen. Sterling, of 249 Knightsbridge,
London, and was sold at Sotheby’s on 29 April 1914 for £46:
while later in the same year (10 July 1914—not 19 July, as
stated by de Groot) it is said* to have been resold at Christie’s
for £120. 15s.

Notwithstanding the allegations of de Groot and others,
there seems to be still no satisfactory evidence to prove that
any portrait of Leeuwenhoek was ever painted by Maes: but
the matter obviously needs further investigation.

(3) By ADRIAEN VAN OsTADE (1610-1685: born at Haarlem,
where he worked and died). See Moes (1905; Vol. IT, p. 12)
No. 4415 (1): de Groot (1910; Vol. IIT, p. 410) No. 876.—De
Groot calls this a “ Portrait of Anthonie van Leewwenhoek (1632-
1722), physicist and surgeon of Haarlem”’,” and he describes
the picture thus: “ He sits, turned three-quarters left, and
leans his left arm on the table and his right hand on his hip.
He wears a black costume with a white collar and brown
gloves. In front of him are a book and a celestial globe.
Signed in full at the foot of the globe, and dated 1665; panel,
81 inches by 7 inches.” This portrait is stated to have been
sold in Paris on 2 May 1865 (Sale H. de Kat, No. 63). Ihave
been unable to find it. I may note, however, that what
appears to be a copy in black chalk, by A. Delfos, is preserved
in the Municipal Museum at Delft. It is a poor portrait (if it
be one) and bears little resemblance to the authentic pictures
of Leeuwenhoek, though the face recalls many of the peasants
portrayed in Ostade’s other paintings.

Adriaen van Ostade was no portrait-painter (and in my
opinion a very poor artist): and at present I am not convinced
that he ever attempted to paint a portrait of Leeuwenhoek—
or, if he did, that it is now in existence.

1 Tt is also there said to represent ‘“‘ Lieuvenhoch, the father of the
Microscope”!

2 There are 5 obvious errors in these dozen words.

PORTRAITS OF LEEUWENHOEK 353

(4) By CoRNELIS DE MAN (1621-1706: born, worked, and
died at Delft). According to Moes (1905; Vol. II, p.12)
there is—or was—a portrait of Leeuwenhoek by this artist,
dated 1681, in the “ Anatomie-Kamer te Delft.” When I
visited the town in 1923 I was unfortunately unable to find it:
and subsequent inquiries made through the late archivist
(Mr Bouricius), and the late Prof. Beijerinck, have been
equally fruitless.

(5) By JAN VERMEER (1632-1675, of Delft). There is no
authentic record of any portrait of Leeuwenhoek having ever
been painted by this great master. Nevertheless, it has
recently been stated by Lucas (1922, p.8) that Leeuwenhoek,
“the inventor of the microscope,” was “ probably his model for
the three or four scientific pictures”. (By “scientific pic-
tures” Lucas means those paintings by Vermeer showing a
“Geographer” or “ Astronomer” at work.) I have not seen
the originals of any of these (nor had Lucas when he wrote),
but I have studied good photographic reproductions of them
all. ‘There are four, and they appear to me to portray as many
different people. No two are alike, and none bears any
recognizable likeness to Leeuwenhoek—as we know him from
Verkolje’s authentic portraits. I am entirely at a loss to
understand how anyone can seriously suggest that Vermeer’s
‘“Geographers”’ and “ Astronomers” all represent the same
person—and that person Leeuwenhoek. ‘The suggestion
becomes still more perplexing when we find that Lucas (op. cit.,
p.20) also accepts as genuine the spurious “portrait” by
Maes '—which in no way resembles any of the people depicted
by Vermeer or Verkolje.

I must call attention, however, to some curious points
which came to my notice whilst seeking evidence (not given
by him) for Lucas’s statements. The very fine painting by
Vermeer known as “ The Geographer,” now in the Stddelsches
Institut at Frankfort,’ shows a man poring over a map or
chart, and with a pair of compasses in his right hand. Behind
his head there is a globe, and some other maps are also in the

1 See above, p. 351.

* There is an excellent reproduction in colour in “Jan Vermeer of
Delft’ (Portfolios of Great Masters), published by Halton & Truscott
Smith, Ltd. London, 1925.

23

354 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS”

picture—a couple loose on the floor, one framed on the wall.
This is one of the few of Vermeer’s pictures which is signed
and dated. The date, painted on the wall behind, is
MDCLXVIIII (z.e., 1669—not 1668, as stated by more than
one writer on Vermeer). Now this is the very year in which
Leeuwenhoek was appointed surveyor." Moreover, the globe
in the picture is apparently a celestial (not terrestrial) globe,
and is very like that shown in both of Verkolje’s portraits.
Leeuwenhoek must surely have possessed a similar one. In
Verkolje’s oil-painting, furthermore, Leeuwenhoek is shown
holding a pair of compasses in his right hand *—just like
Vermeer’s “Geographer”. The framed map on the wall has
only an artistic import: it has no “ scientific” significance,
being simply a decoration—introduced into many of Vermeer’s
other pictures which have no connexion with geography.
There is no authority for calling this picture “The
Geographer ’”’—a modern label. Suppose we call it “The
Surveyor”? This title seems equally appropriate; and we
might then suppose that Vermeer was inspired to paint it by
seeing Leeuwenhoek at work on ground-plans and surveys in
preparation for his qualifying examination in 1669! But all
this is mere guesswork, though the coincidences Just noted are
curious—if nothing more. “The Geographer” himself is not
much like Leeuwenhoek; and there is no evidence, as I have
already remarked, that Vermeer ever painted his portrait.

(6) By JAN GOEREE (1670-1731: designer, engraver, and
poet. Known also as Gouré).—In the engraved title-page of
Leeuwenhoek’s last published letters (Send-brieven and Epist.
Physiol.) there is inset a little oval portrait circumscribed
“ANTONIVS LEEUWENHOEKIVS DELPHIS NATVS
MDCXXXII”’. It is supported by a fat female angel blowing
a trumpet, and somewhat overclouded by other allegorical
accessories. The first state of this plate (in the Dutch
edition) is lettered at foot “Te DELFT by ADRIAAN
BEMAN, 1718.” and in the left bottom corner “J. Goeree
sculpt: Direa.” The second state (Latin edition) bears the
words “DELPHIS apud ADRIANUM BEMAN, 1719.”
—with the same signature.

1 Cf. p. 34 supra.
* See Plate XI, facing p. 49.

PORTRAITS OF LEEUWENHOEK 355

I formerly attached but little importance to this small
detail—believing it to be on a level with the rest of the
engraved title. Buta few years ago Dr W. H. van Seters, of
Leyden, when collecting material for the ‘‘ Leeuwenhoek
Film ” (which has now been exhibited on various occasions :
cf. Kaiser, 1924), rediscovered’ an old design above which
Leeuwenhoek once wrote a motto and his name. Dr van
Seters kindly sent me a photograph of this drawing (included
in the film), which reveals several points of interest.
Leeuwenhock’s signature (undoubtedly genuine) is there dated
30 April 1698. It is written at the top of the page, and is
followed by a large allegorical drawing illustrating his motto f
(“ Door Arbeyt en Naarstigheijt””). But this drawing was
evidently added later, as it is signed “ J. Goeree del: 1707.”
Moreover, it bears, as a pendant, the miniature portrait of
Leeuwenhoek incorporated later in the engraved titles of his
last letters. This picture was therefore probably made in
1707—not at the date of publication of the Send-brieven
(1718). Careful study of the engraving has also convinced
me that it was made with considerable care, and under
Goeree’s own supervision—as the words “sculpt: Durex.”
sndicate. 1 therefore now regard this portrait (shown in my
Plate XII) as a genuine and conscientious attempt, by fairly
competent artists, to delineate Leeuwenhoek as he appeared
in his 75th year. In any case, this is the only known portrait
of him in his later life which can make any pretence to

authenticity.

In conclusion, I must mention three slyptic representa-
tions of Leeuwenhoek. The first is the profile portrait on
the silver medal awarded to him in 1716 by the University
of Louvain (see p. 80). This has already been depicted by
van Loon and Haaxman. The medal is now in the Gemeente-
museum at Delft; and as it was struck during his lifetime, its

fA ee

1 Tt was exhibited at the Leeuwenhoek Celebration in 1875, and was
described by Harting (1876, p. 120). I think the picture was very probably
intended as a title-page for the projected edition of L.’s letters (following
No. 146 and preceding the Send-brieven) which was never published in
Dutch or Latin.—According to de Lint (1931) the original is now in the
collection of Dr J. van der Hoeven at Eefde [near Zutphen]. It is
reproduced in Opusc. Select. Neerland., Vol. IX, Pl. III (1931).

2 Given in full on p. 299 supra.

“ce

356 LEEUWENHOEK AND HIS “LITTLE ANIMALS”

maker may well have had Leeuwenhoek himself as a model.
The portrait is therefore worth consideration. The second
carved likeness is the white marble medallion on his tomb (see
p. 100, and Plate XV). This was made after his death, and
was probably modelled on the silver medal. It has less interest,
therefore, as a portrait. The third representation is that on
the “ Leeuwenhoek Medal,” awarded every ten years by the
Royal Academy of Sciences of Amsterdam to persons who have
distinguished themselves as microbiologists.' This medal is of
gold, valued at f.300 (about £25), and has been described and
figured by Harting (1876). The portrait which it bears is,
however, a modern fake; and its historico-iconographical
value is consequently mil.

(vii) LEEUWENHOEK’S “FIRST 27 UNPUBLISHED
LETTERS ”

As Leeuwenhoek’s own collective editions of his works—
both Dutch and Latin—begin with a letter called “No. 28”,
dated 25 April 1679, it has generally been assumed that all his
earlier letters (No. 1—No..27) have been lost. But this is not
so: most of them have been preserved among the Royal
Society MSS., and many have been printed in English or Latin
(generally abbreviated) in the early volumes of the Philosophical
T'ransactions.

I have discussed these letters in some detail in an article
about to appear in Opuscula Selecta Neerlandicorum, Vol. IX,
so I need not repeat what I have there said.” But as my
numeration differs entirely from that of Vandevelde—who
previously attempted to arrange and number them without
consulting the original manuscripts—and as I have made
frequent references to these letters in the foregoing pages, I
give here a tabular synopsis for the reader’s convenience and
culdance.

1 The first award was made to C. G. Ehrenberg in 1875. The later
recipients have been Ferdinand Cohn (1885), Louis Pasteur (1895),
M. W. Beijerinck (1905), David Bruce (1915), and F. d’Herelle (1925).

2 Since these lines were written, the article has appeared in print: see
Dobell (1931).

TABULAR SYNOPSIS

357

LEEUWENHOEK’S “FIRST 27 LETTERS”

Letter

Addressed to Date Roy. Soc. MS. Published in Phil. Trans.
H. Oldenburg ? [No MS.] | Vol. VIII, No. 94, pp. 6037-6038.
[Transmitted 1673. [Extracts, in English. ]
by de Graaf | Vol. VIII, No. 97, pp. 6116-6118.
28 Apr. 1673] 1673. (Figures, with description in
English. ]

H. Oldenburg | 15 Aug. 1673 | L.1. 1 | Vol. IX, No. 102, pp. 21-23 and
23-25 [in 2 parts]. 1674. [Extracts,
in English.]

H. Oldenburg! 7 Apr. 1674 | L.1. 2 | Vol. IX, No. 102, pp. 23-25. 1674.
[Combined with part of Letter 2,

| Extracts only, in English. ]

H. Oldenburg | 16 Apr. 1674 | L.1. 83 | Unpublished

Lys Ee Sa ee eee Lia Ala Pa Ne

H. Oldenburg | 1 June 1674 | L.l. 4 | Vol. IX, No. 106, pp. 121-128. 1674.
[Part only—in English. ]

H. Oldenburg | 6 July 1674| L.1. 5 | Vol. IX, No. 106, pp. 128-131. 4674.

| [Extracts only—in English. ]}

H. Oldenburg | 7 Sept.1674 | L.l. 7 Vol. IX, No. 108, pp. 178-182 [mis-
printed 821]. 1674. [Incomplete
English translation. ]

H. Oldenburg | 7 Sept.1674 | L.1l. 6 Unpublished

H. Oldenburg | 19 Oct. 1674 | L.1. 8 | Unpublished

H. Oldenburg | 4 Dec. 1674 L.1. 9 | Vol. X, No. 117, pp. 378-380. 1675.
[Extracts in English. ]

H. Oldenburg | 22 Jan. 1675 | L.1. 10 | Unpublished

H. Oldenburg | 11 Feb. 1675 | L.1. 11 | Unpublished

H. Oldenburg | 26 Mar. 1675 | L.1. 13 Unpublished

H. Oldenburg | 14 Aug. 1675 | L.l. 15 Vol. X, No. 117, pp. 380-385. 1675.
(Extracts, in English.]

H. Oldenburg ; 20 Dec. 1675 | L.1. 16 Unpublished

H. Oldenburg | 22 Jan. 1676 | L1. 16a | Unpublished

H. Oldenburg | 22 Feb. 1676 | L.1. 17 Unpublished

H. Oldenburg | 21 Apr. 1676} L.1. 18 Vol. XI, No. 127, pp. 653-656. 1676.
[Incomplete English translation,
with notes (by Nehemiah Grew).]

H. Oldenburg | 29 May 1676} L.1. 20 Unpublished

R. Boyle 28 July 1676 |[ With Unpublished

Boyle MSS.]
H, Oldenburg | 9 Oct. 1676 | L.1. 22 Vol. XII, No. 133, pp. 821-831. 1677.

[Incomplete English translation. }

358

LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS”

SYNOPSIS OF LEEUWENHOEK’S “ FIRST 27 LETTERS ’’—continued

Letter
No.

21

21a

24

25

26
27

Addressed to

H. Oldenburg

Viscount

Brouncker

Viscount
Brouncker

R. Hooke

N. Grew

N. Grew

N. Grew
N. Grew

H. Oldenburg

H. Oldenburg

H. Oldenburg

Date

30 Oct.
23 Mar.

14 May

5 Oct.

16 Oct.

.. Nov.

14 Jan.

18 Mar.

31 May

27 Sept.
21 Feb.

1676
1677

1677

1677

1677

1677

1678

1678

1678

1678
1679

Roy. Soc. MS.

L.1. 24
L.1. 25

ly 2

ed; 29

L.1. 32

[No MS.]

L.1. 33

Lil. 34

L.1. 36

Ll. 88
[No MS.]

Published in Phil. Trans.

Unpublished

Vol. XII, No. 134, pp. 844-846. 1677.

{Incomplete English translation. ]

Vol. XII, No. 136, pp. 899-905. 1677.

[English translation. A full Latin
translation of this letter was pub-
lished later in Derham’s Philos.
Ezpts. & Obss. of R. Hooke (1726),
pp. 65-74. ]

(Not in Phil. Trans. English ex-

tracts published in R. Hooke’s Lect.
& Collect, (1678), Part II, Letter 1,
pp. 81-83: reprinted in his Lect.
Cutlervanae (1679).]

Unpublished

Vol. XII, No. 142, pp. 1040-1043.

1679. [Full letter, in Latin. ]

[Not in Phil. Trans. English ex-

tracts published in Hooke’s Lect. €
Collect. (1678), Part II, Letter 2,
pp. 84-89: reprinted in his Lect.
Cutlervanae (1679). ]

Vol. XII, No. 142, p. 1044. 1679.

(Abstract, in Latin. }

Vol. XII, No. 140, pp. 1002-1005.

1678. [Two extracts, in English.]
Vol. XII, No. 142, p. 1045. 1679.
[Latin summary of another part of
letter. ]

Unpublished

Unpublished [This letter is men-

tioned by L. in his letters dated
13 June 1679 (No. 28a, unpublished),
13 Oct. 1679 (No. 280, unpublished),
and 25 Apr. 1679 (No. 28— published
in Dutch and Latin printed works).
It was apparently lost in trans-

mission. ]

Addendum.—All the Letters marked ‘‘ Unpublished” in the foregoing
list have now (with the exception of the last, which still remains lost) been
printed in full in Vol. IX of Opuscula Selecta Neerlandicorwm, Amsterdam,
This volume has appeared too late for its contents to be considered
in the present work.

1931.

LEEUWENHOEK’S SEALS 359

In addition to the information given in this table, I must
note the following points:

(1) Leeuwenhoek sent a complete copy of his Letter 4
(1 June 1674, to Oldenburg) to Const. Huygens, and the MS.
is preserved at Leyden. ‘This copy has recently been printed
by Vandevelde and van Seters (1925).

(2) Letter 19 (23 March 1677) and Letter 21 (5 Oct. 1677)
are quoted extensively by Leeuwenhoek himself, in his own
language, in his Letter 96 (9 Nov. 1695, to the Elector Palatine)
printed in the Dutch works—with Latin versions, of course,
in the corresponding Latin editions.

(3) Letter 22 (Nov. 1677) is quoted, almost entire, in its
original Dutch, by Leeuwenhoek in his Letter 113 (17 Dec.
1698, to Harmen van Zoelen—published in the collective
editions) : and a complete English translation of it (made but
not published by myself) has now appeared in the recent
work of Cole (1930).

(4) Finally, I must note that the printed Catalogue of the
Royal Society MSS., compiled many years ago by the youthful
Halliwell-Phillipps (1840), is not free from errors; and
accordingly its entries relating to the Leeuwenhoek MSS. are
not to be accepted as invariably accurate.

(viii) LEEKUWENHOEK’S SHALS

Seals on old manuscripts are often important for purposes
of identification: how important they may sometimes be, I
know from the following incident. Recently, Carbone (1930)
believed that he had discovered a new Leeuwenhoek letter
among the Magliabecht MSS. in the National Library at
Florence. This document was among the genuine letters of
Leeuwenhoek addressed to the Florentine scholar, but was
unsigned. Carbone reproduced it in facsimile—including the
seal (enlarged). From its contents it was at once evident
to me that this letter (written in Latin, and dated 2 May 1692
from Hanover) could not possibly have been written by
Leeuwenhoek. I guessed immediately, however, that it was
written by Leibniz: and on comparing it with Leibniz’s
extant letters to the Royal Society, I found that the cor-
rections throughout were apparently made in his handwriting,
and that the seal was one which he used. A seal is often
as good as a signature (for no man lent his seal-ring to

360 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS”

others), and I therefore felt satisfied that the letter was written
by Leibniz and not by Leeuwenhoek. This I was soon able to
confirm by discovering that the manuscript in question had
actually been published previously as a genuine Leibniz letter
by Targioni-Tozzetti (1746, pp. 119-122).

Leeuwenhoek’s own seals have never yet been described.
At various periods of his life he sealed his letters with at least
three different ones—usually of red wax, but occasionally of
black. Most of the extant impressions are imperfect—the
seals having generally been broken, of course, in opening the
letters. The following notes are put together from the avail-
able fragments. They may assist future students in identifying
his writings, but are as incomplete and imperfect as their
originals. :

(1) Most of the early epistles are sealed with the monogram
shown in Plate XXXII (upper figure). This is taken from an
almost perfect impression on Letter 3a (16 April 1674)—
stamped from an oval die measuring approximately 16 mm. by
14mm. The letters APL presumably stand for A[ntony]
P[hilipszoon| L[eeuwenhoek] ; the rest of the device I cannot
interpret with any confidence. Above, there appears to be an
arabic numeral 4: below, connected by a vertical line, the
roman figure xx or (more probably) xxv can be read.

(2) Another early seal—which I am unable to reproduce—
was a heraldic device, all extant impressions of which are
more or less fractured or indistinct. The die was apparently
oval, about 17 mm. by 16 mm., with a slightly beaded border.
The available examples show a small shield, bearing four
raised vertical lines, surmounted by a helmet. On the field
behind are various irregularly distributed plumules (?), but no
lettering or other recognizable figures. This seal is affixed to
several early signed and authentic letters to the Royal Society
(including No. 13, 20 December 1675, from which an extract
is here translated). The armorial bearings I have been unable
to identify. I can only add that an identical scutcheon with
four vertical lines is several times figured by Boitet (1729) as
the coat-of-arms of the Uttenbroek family—a family with
which Leeuwenhoek is not known to have been connected.

(3) Nearly all the later letters, when sealed, bear a portrait
of Leeuwenhoek himself. The die used for this seal (see
Plate XXXII, lower figure) was evidently cut with very great
care and precision, and the various impressions—in red (rarely

facing p.

360

TWO OF LEEUWENHOEK’S SEALS

Enlarged.

For description see the text.

PLATE

a7
a 2

r us eur ge hr aa yr
re eh » a ako oat 0 ee
'”

LEEUWENHOEK’S SEALS 361

in black) wax—show an astonishing amount of detail when
closely studied. The seal was obviously copied from Verkolje’s
mezzotint portrait of Leeuwenhoek (1686): it shows his
bewigged head, as there depicted, with a curtain behind, and
even reproduces such minutiae as his little moustache. Most
impressions, however, are faulty or badly fractured. The best
(from which my figure here is reproduced) is on Maria’s letter
to the Royal Society." I judge the original die to have
measured—outside its beaded border—approximately 21 mm.
by 18mm. But I cannot be sure, as most impressions are so
imperfect. (The specimen figured by Carbone (1930) is
extremely poor.)

This seal cannot have been used by Leeuwenhoek before
1686, when Verkolje made his mezzotint. It may therefore
possibly help to date some of his undated letters in future.
The artist who cut the die is not known; but he must have
been extremely skilful, for his work reveals—on careful study
of good impressions—a degree of accuracy in reproducing
minute detail which is really remarkable. Unfortunately, the
dies of all the seals are now lost.

SIMPLEX SIGILLUM VERI

1 See p. 98 supra. There are two seals on this letter, but only one is
perfect. The other is distorted by a slip in impressing the wax.

362

ENVOY: LEEUWENHOEK’S PLACE
IN PROTOZOOLOGY AND BACTERIOLOGY

Protozoology and Bacteriology ”’, and I now repeat this

title—which has since been adopted by others—on the
title-page of the present work. I do this designedly, because
in my opinion he alone deserves this designation. In my
opinion (which has not been formed too hastily) he was the
first man who ever saw living protozoa and bacteria under
a lens, and by correctly interpreting and describing his obser-
vations he created the modern disciplines of Protozoology and
Bacteriology. Consequently, his relation to these sciences is
that of “father” or “only begetter’”’.

Nevertheless, there are still some people who dispute
Leeuwenhoek’s claim to the discovery of the Protozoa and the ~
Bacteria, while there are others who bestow upon him titles
which he does not deserve—as he himself would freely have
confessed. He has already been styled “Father” and
‘Founder ’”’ of Micrography by Blanchard (1868) and Vande-
velde (1922)—to mention no other authors: though it is
obvious that Pierre Borel and Henry Power and Robert Hooke
and Marcello Malpighi have all at least as good a right to the
title. Launois (1904) obviously goes rather too far when he
calls Leeuwenhoek one of the “ Fathers of Biology’’: there is
more evident justification for those who regard him as the
“Father ” of Histology or Cytology or Haematology ‘"—or even
as just the First Milk-Analyst.” Almost every writer who
discusses Leeuwenhoek’s work regards him, apparently, as
“father” of his own speciality—some strangely misinformed
but enthusiastic authors even hailing him as “the Inventor

A FEW years ago I called Leeuwenhoek “Father of

1 Sabrazés (1926).
2 Wynter Blyth (1903).

THE ENVOY 363

of the Microscope”.’ Many such claims are manifestly
absurd; yet his own right to be regarded as the Father of
Protozoology and Bacteriology is, I believe, real and
indisputable.

The discovery of the microscope is still in dispute, but I
need not discuss the subject here. Its invention is intimately
bound up with that of the telescope, and the rival claims of
Italy and Holland in this connexion have been ably defended
in recent times by Govi (1888), and Harting (1850) and de
Waard (1906) respectively. The question has also been
critically considered lately by Singer (1921) and Disney (1928).
For present purposes it will suffice to note that one form of
the microscope (¢.e., the compound microscope, to which the
name is properly applied) was probably devised in Holland in
the first decade of the XVII Century (not earlier), while
immediately afterwards another form was independently
discovered in Italy. But Leeuwenhoek probably knew nothing
of all this, and it is unnecessary to argue here about the
priority of Zacharias Janssen, Lipperhey, Drebbel, Galileo, or
any other possible “inventor of the microscope”. Leeuwen-
hoek did not use a microscope, but only a simple lens; so
that the invention of the compound instrument (which
occurred before he was born) has no bearing whatsoever upon
his own work or discoveries.

The discovery of simple lenses is, however, also a subject
of dispute. It is now known, from the profound researches of
the French scholar Martin (1871), that the ancients knew
nothing about magnifying-glasses—notwithstanding the con-
fident assertions of Dutens and many another more recent
writer. Our Roger Bacon® (circa 1214-1294) had at least a
glimmering of the properties and possibilities of lenses, but
the first were probably made, and used as spectacles, about

1 Byen since these lines were written I have read a paper (Chapman,
1931) in which it is said that L.’s observations “ have earned for him the
title of ‘The Father of Microscopy ’.”

2 This excellent and fully documented work appears to have been over-
looked by all recent writers on the history of the microscope—including
Singer and Disney.

3 Of. Bridges (1914). In this connexion the reader may also consult
with profit the recent historical analyses by Singer (1921) and Disney e¢ al.
(1928). The literature dealing with Bacon is too vast to cite here.

364 LEEUWENHOEK AND HIS “LITTLE ANIMALS”’

the year 1300 in Italy—their popularization “for the help of
poor blind old men” being chiefly due to the pious and
private labours of the monk Alessandro de Spina of Pisa.
The actual inventor of spectacles, however, is said to be a
Florentine—Salvino d’Armato degl’Armati.’ Friar Bacon
and his brethren in Italy were probably the originators of
simple lenses; and the unknown people who first wore
spectacles and used ordinary magnifying-glasses—for assis-
tance in reading or for personal amusement—are the real
“precursors ” of Leeuwenhoek as a “ microscopist ”’.”

According to Govi (1888), the word “ microscope”
(microscopio) was invented by Giovanni Fabri*—one of the
earliest members of the Accademia dei Lincei—who first used
it in a letter to Federigo Cesi dated 13 April 1625. The first
pictures made with the aid of this instrument are usually
supposed to be those of the bee and weevil interpolated by
Francesco Stelluti (1630) in his Italian translation of the
poems of Persius. The first “micrography ” is the Century
of Microscopic Observations by Pierre Borel,* published in
Latin at The Hague in 1656: but it was soon followed by the
similar work of Henry Power’ (1663-4) and the more
celebrated Micrographia of Robert Hooke (1665)—both
written in English and printed in London.

The writings of Stelluti and Borel and Power and Hooke
all antedate anything that Leeuwenhoek ever published.
But when he wrote his first letters he had probably never
heard of any of these authors: and as he could read neither
English nor Latin nor Italian, they could have afforded him

1 Cf. Redi (1678), Mensert (1831), Harting (1850), Pansier (1901), etc.

2 I cannot refrain from mentioning here a remarkable fantasy recently
published by our greatest living English poet and novelist—an unhistorical
story revealing more than superficial historical knowledge. I refer to
Rudyard Kipling’s “The Eye of Allah”, printed in his volume entitled
Debits and Credits (8° London, 1926).

3 Fabri or Fabro, in Italian. His real patronymic was Faber, and he
was descended from a family of this name who came from Bamberg in
Bavaria. Cf. Carutti (1883, pp. 25, 39), ete.

4 Pierre Borel, alias Petrus Borellus (1620-1689), a French physician,
antiquary, and philologist. Cf. Nowv. Biogr. Gén., VI, 697.

* Henry Power (1623-1668), M.D. Educated at Christ’s College,
Cambridge, and practised as a doctor at Halifax. He was one of the first
Fellows of the Royal Society—having been elected in 1663.

THEE ENVOY 365

little help—even had he seen their works. Moreover, there
are no descriptions of protozoa or bacteria in any of these
publications—so far as I have been able to ascertain. I have
studied them all with care, but have sought information on
such organisms in them in vain. I believe they contain none,
and nobody (to my knowledge) has yet proved that they do.
Nobody now claims that Fabri or Stelluti or Power or Hooke
discovered the Protozoa or the Bacteria: but a half-hearted
claim has recently been made for Borel by Singer (1915), so
I cannot altogether ignore it here.

Borel (1656) tells us that “worms” are said to be found in
the blood of people suffering from “ fever”’,' though he makes no
claim to have seen such things himself. Yet Singer says” that
to him “It seems . . . highly probable that he caught a
glimpse of infusoria and possibly bacteria, for he assures us that
all decomposing material swarms with similar worms.” Singer
gives no exact reference to the passage on which he relies, but
apparently alludes to Borel’s Observatio de Sanguine ; in which
he does not give any such assurance, but merely says it zs
probable that worms would be found in every decomposing
material if attention were paid to it.’ The whole passage is
clearly hypothetical. As a prophecy it may have some interest
for helminthologists: for the protozoologist or bacteriologist it
is obviously without significance. Something more than a
misreading or mistranslation of Borel’s words is surely needed
to prove that he forestalled Leeuwenhoek.

Another claim to priority in the discovery of the Bacteria
has been put forward for the German Jesuit priest Athanasius
Kircher (1602-1680)—well known as a voluminous and reckless
writer on all manner of subjects.* I do not pretend to have

1 Certo etiam refertur, in sanguine febricitantium vermes reperiri.

2 Singer (1915), p. 338. Singer’s references to Borel are not always
easy to follow. In two places, indeed, he appears to confuse Borel’s work
of 1656 with his earlier publication of 1653. But this—so far as I can
discover—contains only one trivial reference to the use of the “ engyscope”’
[= microscope], having no bearing on the present subject. Borel’s later
observation (1656a, p. 198) on “ whale-like insects in human blood ’’—to
which Singer also alludes—cannot conceivably refer to either protozoa or
bacteria.

3 quare verisimile est idem in omni re, dum putrefit, contingere, si animad-
vertatur (Borel, 1656; Obs. III, p. 8).

4 Cf. Nouv. Biogr. Gén., XXVII, 769, and Allg. Dtsch. Biogr., XVI, 1.

366 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS”’

read all his works (which is probably impossible and would
certainly be unprofitable), but only some parts of those which
deal with biological topics. In none of them can I find any
evidence whatsoever to indicate that he ever saw or described
either a protozoon or a bacterium. But others believe that
they have been more fortunate, so I must briefly consider their
findings.

The first person to credit Kircher with the discovery of
the Bacteria was, I believe, Friedrich Léffler (1887), who
opens his work on the history of bacteriology with a quotation
from the Scrutinium Pestis (1658)* wherein Kircher says:
“That air, water, and earth are swarming with countless
insects, is so certain that it can even be proved by ocular
demonstration. It has hitherto also been known to everybody
that worms swarm out of rotting bodies: but only after the
wondrous invention of the Microscope did it become known
that all decomposing things swarm with an innumerable
brood of worms invisible to the naked eye: which even I
myself would never have believed, had I not proved it by
repeated experiment over many years.” *

Now this passage contains no obvious reference to any
organisms other than worms or insects—well known to
everybody at the time when Kircher wrote: yet for reasons
unexplained Léffler alleges that it “announces . . . the
discovery of a new world of living creatures” —by which he
means, presumably, the Bacteria. But does it? Surely not.
The assumption is so far-fetched, indeed, that Léffler felt
constrained to add that ‘“ Kircher was unable to give any
more accurate data regarding these worms;” and he then
made an irrelevant reference to the Ars Magna Lucis et
Umbrae (1646). Any ordinary person would conclude that
Kircher never described bacteria for the simple reason that
he never saw them—and because Leeuwenhoek had not then

1 Léffler actually quotes (in German translation) from an edition of
1671, but gives no exact reference to the passage. I have not seen this
edition, but it appears to be a reprint of the first Leipzig edition (1659),
which I possess. In this the passage quoted (from Cap. VII, § II) is on
p. 69. I have to thank Dr Singer for kindly lending me his own copy of
the original edition of 1658.

2 T translate from the original dog-latin of Kircher (1658)—not from
Loffler.

THE ENVOY 367

published his discoveries. The organisms which Leeuwenhoek
discovered were, for those times, of a ‘“Stupendious
Smalness’’;* and there is good reason to believe that Kircher
possessed no instruments capable of showing any objects of
the order of magnitude of common bacteria.

Singer (1914), however, has recently reasserted Léffler’s
claims, and has attempted to support them with translated
quotations from Kircher’s “ Experiments” with rotting flesh,
leaves, and wood. ‘These are really too ridiculous to quote.”
It is obvious—from Kircher’s own words—that he saw nothing
but maggots, mites, and nematodes, such as anybody possessed
of asimple low-power magnifying-glass can nowadays perceive.
I have consulted all the passages on which Léoffler and Singer
rely, and have repeated some of Kircher’s so-called experiments:
and I have even read a considerable part of the Scrutiniwm
Pestis and of the Ars Magna, and have made long search in
Buonanni’s Micrographia Curiosa (1691) and Musaeum
Kircherianum (1709). But the results have been incommen-
surate with my labours. T'o me the Scrutiniwm Pestis appears
as a farrago of nonsensical speculation by a man possessed of
neither scientific acumen nor medical instinct.’ Kircher
obviously had no conception of a real experiment—in the
Baconian and modern sense. It is easy enough, of course, to
tear a line here and there from his voluble writings, and to
use it as evidence on his behalf: but if such lines be considered
in their context they have a very different complexion. For
instance, some recent authors have inferred that Kircher’s
remarks about rats dying and decomposing at atime of plague
show that he realized the relation of these rodents to plague-

1 Grew (1701), p. 12.

2 About ten years ago I had some correspondence with Dr Singer on
this matter, and I then attempted to convince him of the error of his views.
From his last letter to me on the subject I gather that he is no longer
prepared to defend Kircher’s claim to the discovery of either the Bacteria or
the Protozoa, and that he now accepts my interpretations.

8 Kircher—who was a priest with no biological or medical training—
had obviously derived most of his “ knowledge” from wide reading, and it
seems to me not unlikely that in his vague references to ‘ worms”’ occurring
in the blood of sick people he was merely harking back to the speculations
of antiquity: for example, to the well-known passage where Pliny says
“nascunturque in sanguine ipso hominis animalia exesura corpus ”’
(Hist. Nat., lib. XX VI, cap. xiii; ed. Genevae 1582, p. 488).

368 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS ”’

epidemics. Iwish such authors would also explain, in modern
terms, what Kircher meant when he recorded further how
plague could arise likewise from a rotting mermaid.

For my part, I cannot regard Kircher as anything more
than the veriest dabbler in Science. His own writings
appear to me unscientific in the highest degree, and I can find
no evidence that he ever saw—even by chance—a protozoon
or a bacterium through his “smicroscope.” His writings
appear, consequently, to furnish no evidence whatsoever to
prove that he forestalled Leeuwenhoek. But asI have already
said, I have not read all his works. I can therefore only beg
his supporters (if any there still be) to adduce some solid
passage—which I have hitherto been unable to discover in his
vast publications—to prove that he ever saw a protozoon.
(Discussion of his “ discovery’ of the Bacteria may well be
postponed until it has been demonstrated that he observed
these larger organisms.) I am aware, of course, that Garrison *
calls Kircher “the earliest of the microscopists”’ and says
that he was “ undoubtedly the first to state in explicit terms
the doctrine of a ‘contagium animatum’ as the cause of
infectious diseases”’: but I submit that these statements also
have not yet been substantiated, and I cannot conceive that
they ever will be. Microscopists and contagiwm animatum
both existed before Kircher began to write.

This brings us to another line of argument against
Leeuwenhoek’s originality—the argument from the doctrine of
contagium vivum. It is as certain as anything historic ever
can be that Kircher was not the first exponent of this idea:
and there can be no doubt that the part played by “ animal-
cules” in the causation of diseases was foreshadowed long
before either Kircher or Leeuwenhoek was born.’ Some of the
oldest known authors appear to have been familiar with the

1 Garrison (1921), p. 250.

2 In this connexion the paper by Singer (1913) should be mentioned,
though I must confess that I have been unable to verify many of his
statements and references.

3 IT do not deny, of course, that Kircher formulated a “ doctrine of
contagium animatum’’—and possibly more explicitly than his predecessors :
but I do deny that it had any more objective basis than similar earlier
guesses. The doctrine had no concrete foundation before L.’s discovery of
real “ animalcules.’’

THE ENVOY 369

concept of a living “ contagion ” or infective agent—invisibly
floating in the air at the time of epidemic pestilences, and com-
parable with some kind of “insect”. Malaria, for example,
was all too well known in classical times, and even rustic writers
such as Varro‘ (116-27 B.c.) and Columella (florwit ca. A.D. 50)
cuessed that the “insects” abounding in marshes have some
causal connexion with “fever’’.* (The ancients even used
mosquito-nets as a prophylactic.) At a much later date
Lancisi (1718) developed a more coherent and modern theory
of malarial infection: yet even in his hands it remained nothing
but an ingenious speculation.’ The true aetiology of malaria
has become known only in the last fifty years. In Leeuwen-
hoek’s day both the malarial parasite and its mode of
transmission by the mosquito were still wholly unknown to
mankind, and the guesses of his predecessors and contem-
poraries have really no bearing upon his own discoveries.
Nobody before Leeuwenhoek ever saw a living protozoon, and

1 Marcus Terentius Varro (who was no mere husbandman) is particularly
noticeable because of his antiquity. He is frequently cited, but seldom
correctly. In all his extant works there appears to be but one passage
bearing on the aetiology of malaria: and as most editions of his writings
are rare, and as the passage in question is very short, I may quote it here.
Discussing sites appropriate for a country house, Varro notes certain places
to be avoided (such as the banks of a river—apt to be too cold in winter
and unhealthy in summer) and then adds: ‘‘ Attention should also be paid
to any marshy places thereabouts ; both for the same reasons, and because
[they dry up,] certain minute animals grow there, which cannot be detected
by the eye, and which get inside the body from the air, through the mouth
and nostrils, and give rise to stubborn distempers.” (Advertendum etiam
siqua erunt loca palustria, et propter easdem causas, et quod [arescunt,]
crescunt animalia quaedam minuta, quae non possunt ocult consequi, et per
aera intus in corpus per os, ac nares perveniunt, atque efficiunt difficilis
morbos.) Of. Varro, lib. I, cap. XII (Script. Rez Rust., ed. 1543, p. 54 recto).
The words in square brackets should probably be omitted—arescunt being a
MS. misreading or dittography of the word following.—Since writing the
foregoing note I find there is now an excellent English edition of Varro by
Storr-Best (1912): nevertheless, I let my own translation of the passage
stand.

2 The references to malaria in the Latin classics are mostly collected in
the recent posthumous work of Celli (1925), while the Greek literature has
been ably reviewed by Jones (1909).

3 Lancisi actually refers to L.’s discoveries in order to prove the existence
of such extremely minute animalcules as he himself postulated. Cf. op. cvt.
p. 46.

24

ce

370 LEEUWENHOEK AND HIS “LITTLE ANIMALS ”’

all early speculations about the relation of “insects” to
malaria belong properly to the -prehistory of entomology—not
to that of protozoology.

The whole history of bacteriology has recently been so
admirably written by Bulloch (1930) that I can add nothing to
his account of its origins.” He has shown quite clearly that
real bacteriology (like real protozoology) began with Leeuwen-
hoek’s discoveries, though it was preceded by a long period of
speculation on the causes of contagious diseases. Some early
writers, it is true, made astonishing guesses at the existence of
bacteria—particularly Fracastoro (1478 or 1483—1553), whose
hypothetic “ seminaria”’ bear a remarkable resemblance to
modern ‘germs’ or “microbes”.? But nobody before
Leeuwenhoek ever saw a bacterium with his own eyes.
Nebulous though ingenious notions about invisible living
organisms floated in the air for some thousands of years : but
it required the untutored genius of a Leeuwenhoek to condense
them—single-handed and with only his own little home-made
‘““microscopes”’—into the concrete realities of present-day
laboratories and text-books of bacteriology.

Another point should not be overlooked in this connexion.
When Leeuwenhoek announced his discovery of the
“animalcules”” in various waters and infusions, it was
universally regarded as something entirely new. Yet the
earlier writings of Kircher and others had already been public
property for some years. Why, then, were contemporary
‘“ philosophers ’”’ astounded at Leeuwenhoek’s “ discoveries ”»—
if they were not real discoveries? And why did some
contemporary and later critics dispute his observations ?
Why did no author of his time—including Kircher, who was
still alive and busy writing—claim priority? It is surely
strange, to say the least, that nobody before Loffler in 1887
ever connected Leeuwenhoek’s concrete discoveries of 1676
with Kircher’s random speculations and “experiments” of 1658.

1 T may note, however, that I have studied most of the early writings
mentioned in this fine and accurate work: but as I agree entirely with its
conclusions, and as it has an authority far beyond anything to which I can
pretend, I shall here dispense with all other references to the subject.

2 I cite the work of Fracastoro because I have devoted particular atten-

tion to his writings, owing to their great historic interest. On Fracastoro
see also C. and D. Singer (1917).

THE ENVOY 371

All Leeuwenhoek’s contemporaries regarded him as
unquestionably the discoverer of his “little animals”. But
his discoveries were soon confirmed by Hooke—as we have
already seen—and by several other “philosophers”. In the
last decade of the XVII Century the work of Buonanni' (1691)
appeared, containing the first pictures of free-living ciliates,
but reaffirming the doctrine of spontaneous generation—a
small advance and a big step backwards at the same time.
Of much greater importance were the papers by King’ (1698)
and Harris * (1696), who both saw and described a variety of
free-living protozoa and bacteria—tfrankly in imitation of
Leeuwenhoek, but adding new facts and some original
speculations. Of far less value, protozoologically, were the
notes by Gray * (1696, 1697), who observed protozoa with his
ingenious “ water-microscope” but gave only a slight account
of what he saw. These five men—Hooke, Buonanni, King,
Harris, and Gray—must all be regarded as belonging to the
first generation of protozoologists.

But by far the greatest scion of this generation still
remains unknown to us by name. In two anonymous
English publications’ which appeared in the Phil. Trans. in
1703 are to be found some amazingly good figures of free-

1 Filippo Buonanni, alias Philippus Bonannus (1638-1725), an Italian
Jesuit priest.

2 Sir Edmund King (1629-1709), M.D.; physician to Charles II, whom
he attended during his last illness. He was elected F.R.S. in 1666.

* The Rey. John Harris (1667 ?-1719), D.D., rector of Winchelsea in
Sussex, F.R.S. (1696). Author of Lexicon Technicum (1704).

* Stephen Gray (?-1736) was a physicist, who published a number of
papers in the Phil. Trans. He was not made a Fellow of the Society
until 1732.

> See Anonymus (1703,1703a). The first paper consists of extracts from
several letters written in 1702 and “communicated by Sir C. H.” [= Sir
Charles Holt, not a Fellow] : the second comprises two other letters (1703)
from “a Gentleman in the Country ”, communicated by “ Mr. C.” [probably
John Chamberlayne]. All these letters were really written by the same
person, whose identity I have vainly endeavoured to discover. The letters
themselves are not in the Society’s archives or the British Museum (so far
as I have been able to ascertain), and all the documents relating to them
appear to have been destroyed. In view of their great interest, I have made
repeated attempts to discover their authorship; but every clue has proved
unavailing, and I fear that “The Gentleman in the Country” covered up
his tracks on purpose—in order to remain anonymous for ever.

372 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS”

living protozoa and bacteria, and diatoms '—confirming and
amplifying many of Leeuwenhoek’s findings and accompanied
by a commentary, light-hearted and conversational, which
shows nevertheless remarkable insight and ability. The
pictures were far ahead of anything previously published, and
are sufficient alone to establish their draughtsman as Hldest
Son of the Father of Protozoology.

Only one other protozoologist of Leeuwenhoek’s period
deserves notice here—Louis Joblot (1645-1723), a French-
man. His observations were first published in 1718,’ and
attracted little notice at the time: but his book is, in fact,
the first special treatise on the Protozoa, and it contains
descriptions and figures of many forms not previously
described. A recent writer* has tried to show that Joblot
was not merely a follower of Leeuwenhoek, but actually his
equal—an independent co-discoverer of the Protozoa. But
such a suggestion is manifestly groundless. There is no
evidence that Joblot studied the Protozoa as early as the
time when their discovery was announced by Leeuwenhoek ;
and the appearance of his book in the next century—only five
years before they both died—definitively assigns his publication
to a later generation. In Joblot’s writings there is no direct
reference to Leeuwenhoek’s discoveries, but much internal
evidence of imitation.’

I have already had occasion to note’ that Leeuwenhoek
himself made no application of his discovery of “‘ microbes’”’
to medical doctrines of contagion. He discovered protozoa
and bacteria not only in waters and infusions but also in the

1 Tabellaria—the first account and figures of this organism. Most of
the other figures are equally easily recognizable.

2 On Joblot see especially Fleck (1876), Cazeneuve (1893), Boyer (1894),
Konarski (1895), Brocard (1905), and Dobell (1923). I may note here that
the work of Sturm (1676), cited by Ehrenberg and others as containing
contemporary observations on “‘infusoria’’, really deals only with insects
and nematodes—not with protozoa. It should not be quoted in this
connexion.

3 This work is now very rare, and is better known from the much later
and comparatively common edition of 1754.

4 Konarski (1895).

° Cf. Dobell (1923).

* See p. 230 supra.

THE ENVOY Sle

bodies of living animals—including man: but he never in his
writings suggested, so far as I am aware, that his discovery of
such “animalcules” threw any light upon the aetiology of
morbid infections or furnished, for the first time, an objective
basis for the old speculations regarding the existence of
“living germs” of diseases—seminaria morborum, contagium
vivum, contagium animatum, and the like. Yet this applica-
tion of his findings was immediately made by others. Within
a few months of the appearance of his Letter 18, announcing
the discovery of the “little animals” in all manner of liquids,
we find “an observing person in the country” writing to the
editor of the Philosophical Transactions as follows': ‘‘ Mr.
Leewenhoecks Microscopical Discoveries are exceeding curious,
and may prompt us to suspect, that our Air is also vermicu-
lated, and perhaps most of all in long Calms, long-lasting
Eastern Winds, or much moisture in Spring-time, and in
seasons of general Infections of Men or Animals.”

As soon as this possible connexion between demonstrable
“animalcules” and hypothetic infectious “germs” was
suggested, it became almost commonplace : its theoretical im-
plications and its obvious practical applications were henceforth
recognized. Yet nobody made any real use of them during
the next century anda half. Mankind possessed the necessary
data, and was inspired—as usual—by the appropriate ideas :
but the course of history has shown that both knowledge
and notions arrived prematurely. We should not blame
Leeuwenhoek, therefore, for making discoveries before they
could be appreciated properly either by himself or by the world
at large. Rather should we censure, I think, those modern
writers who do not take his work into consideration when
discussing present-day problems. ‘To me it is incomprehensible
how one author in my lifetime could have defended a thesis on
Parasitology in the XVI and XVII Centuries,’ and another
could have written a book on The Discovery of the Microbic

1 See Anonymus (1677). Cf. also the words of Slare (1683), quoted
already on p. 230.

2 Rémignard (1902). This dissertation—approved by the great Raphael
Blanchard—contains only two ridiculous references to L. The first (p. 55)
merely alludes to the fact that he did not discover Demodex, while the
second (p. 63) informs us that he believed in the spontaneous generation
of frogs.

374 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

Agents of Disease," and yet could both have ignored all
Leeuwenhoek’s discoveries entirely. His work undoubtedly
has an important bearing on the history of both these
subjects.

Notwithstanding such present-day neglect, Leeuwenhoek’s
discoveries were utilized by contemporary theorists. I may
mention particularly Benjamin Marten,’ who published in
1720 (three years before Leeuwenhoek died) a most curious
treatise to which attention has recently been directed by Singer
(1911). In this book Marten, by assuming that tuberculosis
is caused by invisible “ animalcula”’ like those discovered by
Leeuwenhoek, develops a theory of the pathogenesis of this
disease remarkably similar to current conceptions. In many a
passage, if one substitutes “ Bacillus tuberculosis” for
“animalcula”’ his statements are in close agreement with the
views expressed in modern bacteriological and pathological
works. As a prognostication, or even as a mere tour de force,
Marten’s book is notable: but he himself never saw the
tubercle bacillus, and his writings had no influence on the
history of bacteriology.

In recent times a claim to recognition has also been made
for the French physician J.-B. Goiffon (1658-1730), of Lyons.
Molliére (1886) calls him “wn précurseur des théories
microbiennes”’ on the strength of a dissertation on the
plague which he published in 1722. In this Goiffon
propounds the theory that plague is caused by an invisible
virus (vénin)—probably some kind of “insect” “—which floats
in the air and penetrates into the blood either through the
pores of the skin or else through the mouth or nose. But
Goiffon never attempted to see such “insects” himself, and
makes no mention of the real “animalcules”’ already well
known at that date (through the discoveries of Leeuwenhoek

1 Grober (1912). This German writer’s ignorance of L.’s existence was
possibly feigned, and due to a false patriotism: for though his book bears
evidence of considerable learning, its author had apparently never even
heard of Pasteur also.

2 Marten was a London physician about whom very little seems to be
known. His book is excessively rare, and I am indebted to Dr Charles
Singer for the loan of his own copy—the only one which I have studied.
There is another, however, in the British Museum.

3 Tn one place he actually conceives of it as possessing wings !

THE ENVOY o1D

and his imitators). His own speculations are not particularly
prescient or original, and appear to have but little relation
to modern conceptions. I regard Goiffon’s dissertation as
historically negligible: in any case, it was without influence
upon the course of bacteriology or protozoology.

I cannot omit to mention, in the present connexion, an
extraordinary effort in pseudo-microbiology published just
after Leeuwenhoek’s death by a French quack doctor. This
charlatan, who wrote under the initials ‘““ M.A.C.D.”, pretended
to discover the “insects” responsible for all diseases, and to
cure his patients by eradicating them by secret methods.’
He claimed to be following the system of an English physician
who had learned of it in Persia: and he gave a comical
description—accompanied by the crudest cuts—of no less than
91 absurdly-named “little insects” which cause as many
complaints. This imposture was exposed by Vallisneri,” in a
posthumously published letter which is not generally known.
I need make no further reference to it: I mention it only
because certain learned authors have apparently taken this
obvious bit of charlatanry for a serious contribution to
microbiology or for genuine satire.’ It was certainly neither.

There is no need, for present purposes, to trace in detail
the history of our knowledge of Leeuwenhoek’s “little
animals’? down to modern times. We are here concerned
merely with the beginnings of protozoology and bacteriology :
yet to see them as beginnings we must cast our eye also upon
the later historical landmarks. As everyone knows, scant
progress was made in the century following Leeuwenhoek’s
death; though it is worth noting that the first scientific

1 See M.A.C.D. (1726, 1727). I quote him (as is customary) under
these initials, though his real name, according to Vallisneri (1733), was Boil.
From the “ Privilége du Roy” at the end of his work, where the author
is referred to as ‘le siewr A.C.D.’, it seems that the initial M. stands
for Monsieur. Consequently, he ought properly to be catalogued as
Pa ey ag

“See Vallisneri (1733), Vol. III, p. 218. It is here explained how “Mr
A. C. D.’ was able to impose upon his patients by showing them the
“insects”? in their blood or urine through a trick microscope—which
apparently exhibited the object mounted before it, but really showed
protozoa out of an infusion.

* Cf. Lesser (1738), Ehrenberg (1838), Bulloch (1930), ete.

ce

376 LEEUWENHOEK AND HIS “‘ LITTLE ANIMALS”
names' were assigned to protozoa by John Hill’ in 1752, and
that the first serious systematic treatment of both protozoa
and bacteria was attempted in 1773 by O. F. Miiller*—
revising and amplifying the inadequate account of these
organisms given by Linnaeus* (1758, 1767). These three
writers—an Englishman, a Dane, and a Swede—were all very
remarkable men, in very different ways; yet they had this in
common that they all respected Leeuwenhoek. Even the
cavalier Hill—a bitter critic of the Royal Society and all its
works (which he nevertheless copied’ freely for his own
profit)—was forced to allow his merits. In one place he says,
for example, “Even Lewenhoeck the Father, as he may be
called, of this Branch of Observation, is not without his
Mistakes, tho’ there are many more in Proportion in all
that have followed him”.°

Hill was an amateur microscopist, and he made no original
contributions of value to protozoology: but though Linné
was a professional naturalist, he had equally little know-
ledge of the Protozoa—notwithstanding he made the first
attempt to classify the micro-organisms known in his day.
But Miller was a systematist with a good working knowledge
of the “‘ Infusoria.”‘ He applied Linné’s system to organisms
which he had himself seen and studied: and he was, withal, an

1 They were pre-Linnaean and not binominal: yet some of them—such
as Paramecium—are still current.

2 Much has already been written about ‘Sir’? John Hill (1716-1775),
though nobody has yet duly appraised his contributions to protozoology.
Cf. especially the Dict. Nat. Biogr., T. G. Hill (1913), and Woodruff (1926).

* Otto Friderich Miiller (1730-1784). Cf. Dansk Biogr. Lewx., XI, 594.
The most recent estimate of him (chiefly as a botanist) is that of Christensen
(1922, 1924). Biitschli fully appreciated his protozoological works, but no
other recent student of the protozoa has attempted to assess or even interpret
all his extremely important observations on these organisms.

* Carl von Linné (1707-1778). For his life see especially Daydon
Jackson (1923).

° As an instance I may note that most of Hill’s figures of protozoa
(1752) were boldly copied without acknowledgement from the anonymous
writer of 1703—from the Phil. Trans. which he so affected to despise !

® Hill (1752a), p. 94.

" Miiller’s “ Animalcula Infusoria”’ were a motley crew of microscopic
creatures, comprising not only all the protozoa and bacteria then known,
but also worms, rotifers, algae, and other organisms.

THE ENVOY S17

excellent observer. His wrong interpretations were inevitable
at the time when he wrote: and when we remember that he
made his observations mostly with the aid of simple lenses of
English manufacture (probably much inferior to Leeuwenhoek’s),
we can now only admire his accuracy. In my view, Miller was
one of the great protozoologists of all time. He was also, for
his period, a good bacteriologist—familiar at first hand with
many bacteria—though he nowhere considers the possibility
that any micro-organisms may be causally connected with
disease.

Linnaeus’s views regarding protozoa and bacteria, and their
relation to infectious diseases, are not easily ascertained.
In the Systema Naturae (ed. X, 1758) he grouped all the
known protozoa in his Class VERMHES and its last order
ZoopHyTa. Apart from a few Foraminifera and Vorti-
cellidae—placed under molluscs and polyps respectively—all
the Protozoa which he recognized were comprised in the single
genus Volvox, containing only two species. In his 12th
edition, however, he elaborates this system somewhat, and
assigns all the “ animalcules” then known to three ill-defined
genera—Volvox, Furia, Chaos. All the “ infusoria”’ described
in “the books of micrographers” (including Leeuwenhoek)
are lumped together in a single species ‘“ Chaos infusorium”’ :
but as an appendix he adds 6 doubtful kinds of “living
molecules ”’ which he leaves to his followers to elucidate." The
list 1s so curious, in many ways, that I must quote it here: ?

The contagion of eruptive fevers ?

The cause of paroxysmal fevers ?

The moist virus of syphilis ?

Leeuwwenhoek’s spermatic animalcules ?

The aery mist floating in the month of blossoming ?*
Miinchhausen’s septic agent of fermentation and
putrefaction ?

wine Os" "G8

Dr Bulloch—who quotes the foregoing list in its original

1“ obscurae . . . moleculae vivae . . . posteris relinquendae.”

2 I translate the original Latin into English in order to be consistent :
but all students of the history of protozoology and bacteriology are doubtless
familiar with Linné’s own words.

3 Meaning, of course, the month of May—which the Dutch also prettily
call Bloeimaand.

“ce

378 LEEUWENHOEK AND HIS “LITTLE ANIMALS”’
Latin—justly remarks (1930, p. 22) that it “is surprising to
find Linné, 30 years after Leeuwenhoek’s death, placing in
the same class spermatozoa and the ‘ethereal clouds in the
time of flowering’’’; and he and others have been puzzled by
Linné’s “ aethereus nimbus”’ (e, supra). But it is probably, I
think, merely a reference to the anonymous English author
of 1677."

Linnaeus himself doubted whether all the then known
protozoa” and bacteria (as we now call them) might not really
be stages in the development of fungi, and he questioned their
relation to diseases. Similar vague suggestions were mooted
in the dissertations of some of his pupils (Bostrém, 1757;
Nyander, 1757; Roos, 1767): but what Linnaeus himself
believed I cannot discover. I think he had no definite ideas ;
for though he was certainly not blind to the possibility that
‘“microbes’”’? may cause diseases, he was also sceptical and
unable to make up his mind. In his own thesis for his degree
(1735) he argued that “intermittent fevers” are caused by
drinking water contaminated with clay, though in 1757 he
apparently approved Bostrém’s thesis contending that the
cause was “bad air” or faulty sanitation. Yet at the same
time he envisaged the existence of “exanthemata viva”
(cf. Nyander), and ten years later (cf. Syst. Nat., and Roos,
1767) was seemingly still sitting on the fence. In my view,
Linné and his pupils never understood Leeuwenhoek’s “ little
animals,’ and all their attempts at systematization merely
created confusion. ‘Their works are of great historic interest,
however, in showing how far professional biologists and medicos
had profited by Leeuwenhoek’s “amateur” labours a century
after he announced his first discoveries.

The only other authors of this period who call for passing
notice here are three Germans—of very different merits. First,
Résel von Rosenhof,’ a miniature-painter who published some
admirable descriptions and figures of protozoa in 1755: secondly,

1 Quoted on p. 373 supra.

2 The name “ Protozoa” was first used by Goldfuss (1817): but his
group so named included not only the “ Infusoria” but also “ Lithozoa”’,

’

‘“ Phytozoa’’, and “ Medusae”’.

3 August Johann Résel von Rosenhof (1705-1759). His life by Kleemann,
his son-in-law, is prefixed to the fourth volume of his Insecten-Belustigungen.
Cf. also Miall (1912), p. 293 sq.

THE ENVOY 379

Ledermiiller,’ a lawyer and amateur microscopist: thirdly, the
physician Wrisberg°— better known as an anatomist and
obstetrician—who published a dissertation on ‘“ Animalcula
Infusoria” in 1765. The work of Ledermiiller (1760-1765) is
really almost negligible, so far as the Protozoa are concerned.
It is chiefly remarkable for being constantly misquoted as the
first publication in which the indefinite term “ Infusoria ” was
employed*: but so far as I have been able to discover, the
word occurs nowhere in Ledermiiller’s long-winded writings.
It was really first used, I believe, by Wrisberg in the booklet
just mentioned, which—though always cited as a classic—
contains little of protozoological importance or novelty.

The much-quoted English works of Adams* (1746) and
Baker ° (1742, 1743, 1753, etc.) are of no account. Both were
copyists and compilers, who drew largely upon Leeuwenhoek’s
publications for their own purposes. Baker’s books, however,
enjoyed a great vogue among the amateurs of his day, and
were translated into several foreign languages. In the opinion
of Harting (1876)—which seems well founded—the Dutch
translations of his popular works on the microscope were,
indeed, responsible for a sudden revival of interest in Leeuwen-
hoek in Holland: for it is a singular fact that on his death
Leeuwenhoek was not only almost immediately forgotten by
the learned world but even by his own countrymen, and the
memory of his achievements has therefore undergone periodic
-resuscitations both at home and abroad.

The latter half of the XVIII Century was enlivened by
the classical controversy between Spallanzani® and Needham

—

1 Martin Frobenius Ledermiiller (1719-1769). For his life see the
recent sketches by Willnau (1921, 1926).

* Heinrich August Wrisberg (1739-1808). His life will be found in the
Allg. Dtsch. Biogr. and Hirsch’s Lexikon.

* Biitschli—usually so accurate—appears to be responsible for the origin
of this erroneous statement. Ledermiiller actually spoke only of “infusion
animalcules”’ in the vernacular (“Infussions Thierlein”; op. cit. Vol. I,
p. 88).

* George Adams, the elder (?-1773) : mathematical instrument-maker to
George III. See Dict. Nat. Biogr.

° Henry Baker, F.R.S. See note 1 on p. 318 supra.

° The Abate Lazzaro Spallanzani (1729-1799)—too great and famous an

ornament of Italian science to require annotation here. (But the reader
may consult with profit the recent note by Bulloch, 1922.)

380 LEEUWENHOEK AND HIs “LITTLE ANIMALS”

(supported by Buffon)' on the subject of spontaneous generation.
This dispute is too familiar for reconsideration here: and
I need only note that Spallanzani successfully defended
Leeuwenhoek’s position—though he paid little attention to
his Dutch predecessor—and was able to support their mutual
belief by many admirable new experiments. But despite his
great experimental skill and instinctive appreciation of scientific
principles, Spallanzani possessed no real knowledge of protozoa
or bacteria. Most of the organisms which he studied can now
be recognized only with difficulty, or not at all, from his
descriptions. Spallanzani was a great experimentalist and
physiologist, but no morphologist or systematist. Needham’s
contributions, however, to all branches of protozoology and
bacteriology may not unfairly be now assessed as nil. He
may have been a good Catholic, but he was a hopelessly bad
protozoologist and bacteriologist.

Although the middle of the XVIII Century produced
numerous confirmations of Leeuwenhoek’s protozoological
discoveries, they were not—at that time—usually so regarded:
they were rather considered as novelties. Nevertheless,
Antony’s marvellous researches on the multiplication of
Volvox and other phytoflagellates were extended by the work
of Trembley’ (1744a, 1747), de Saussure * (1769), Ellis * (1769),
and Corti’ (1774)—two Genevese, an Englishman, and an
Italian. Germany, soon afterwards, also contributed her
share to protozoology through the work of Gleichen* (1778),

? John Turberville Needham (1713-1781), a British catholic priest who
spent most of his life in France and Belgium. Elected F.R.S. in 1747.

2 Abraham Trembley (1700-1784), sometime tutor to the sons of
William Bentinck, English resident at The Hague. Later he came to
England, and was elected F.R.S. in 1743.

3 Horace Bénédict de Saussure [sew Desaussure ] (1740-1799), naturalist
and celebrated Alpinist. For his life see especially Senebier (1801). He
was elected F.R.S. in 1788.

* John Ellis (1710 ?-1776), government agent in the West Indies, and
author of the well-known work on Corallines. Elected F.R.S. in 1754.

* Bonaventura Corti (1729-1813), a catholic priest. Professor of
Natural History at Reggio, and a friend of Spallanzani. One of the earliest
students of the Cyanophyceae, and the discoverer of Spirulina.

* Baron Wilhelm Friedrich von Gleichen-Russworm (1717-1783).

THE ENVOY 381

who re-examined the organisms in infusions, and of Eichhorn '
(1775, 1783), who discovered the first heliozoon (Actino-
sphaerium). But Holland’s only representatives during this
period were Job Baster (1759), who recorded some trifling
observations on vorticellids, and Martinus Slabber (1778) who
rediscovered, redescribed, and first depicted Noctiluca.” Yet
it is a remarkable fact that—apart from Miiller, who was in
this connexion mainly a nomenclator and systematist—
nobody arose anywhere for more than a century following
Leeuwenhoek’s death who can now fairly be called a bacterio-
logist. For 150 years from the date of their discovery
the Bacteria were strangely neglected. Mankind remained
inexplicably blind to their importance, and almost to their
very existence.

From the standpoint of protozoology and bacteriology the
first quarter of last century is a blank. At the end of this
barren period, however, a revival of interest in Leeuwenhoek’s
“little animals” set in—a revival which led, with gradually
increasing momentum, to the enthusiastic development of our
modern sciences. It is now difficult to place oneself in the
position of a zoologist or physician a hundred years ago:
progress in our knowledge of all “ microbes’ has since been so
rapid and so revolutionary. In 1832, Bory de St.- Vincent * had
just published his reclassification of the “ Infusoria ”—which
he needlessly renamed ‘‘ Microscopica’’ *—and Ehrenberg’ was
busy cataloguing the booty collected in his travels: his
monumental monographs were just germinating in the form of

1 Johann Conrad Hichhorn (1718-1790), pastor of the Church of
St Catharine at Danzig.

2 Noctiluca, one of the chief organisms causing phosphorescence on the
surface of the sea, was discovered by the Englishman Joseph Sparshall,
of Wells in Norfolk, whose observations were recorded by Baker (1753,
p. 402 sq.).

* Colonel J. B. Bory de St.-Vincent (1778-1846), soldier, politician,
traveller, and naturalist. For his life, works, and correspondence see
Lauzun (1908).

4 “ Microscopiques.” I believe Bory borrowed this term—as he did so
much else—from Miiller (1773, p. 4: “microscopica dicuntur, quod unice
lenticulae amplificantis ope videntur’’).

° Christian Gottfried Ehrenberg (1795-1876), of Berlin. The fullest
biography is that of Laue (1895). See Dobell (1923a) for further references.

382 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

tentative preliminary papers.’ His huge final treatise of 1838,
together with its comparatively small but devastating corrective
by Dujardin’ in 1841, forms the real foundation of modern
Protozoology. But the first experimental work on trans-
missible microbic diseases was probably that published in the
same period by Bassi * (1835), while the first on any protozoal
infection came much later from Pasteur (1870). Both of these
experimenters studied, singularly enough, no well-known
maladies of man, but certain obscure “epidemics” of silk-
worms—“ moscardino”’ and “ pébrine”’ respectively.’

It is not my purpose now to trace the history of Proto-
zoology and Bacteriology during the last hundred years, so I
shall leave the subject at the moment when our modern sciences
commenced. The authors I have mentioned, and the works
which they performed, are chronicled merely to remind the
reader of certain salient events which cannot be overlooked if
we would see Leeuwenhoek in his true perspective and
proportions.

Of Leeuwenhoek’s discoveries in sciences other than
Protistology I am not competent to speak. I observe, however,
that he is usually most praised by those most qualified to judge.
Those authors who decry his observations generally reveal
themselves, at the same time, ignorant of himself and his
works. Asan instance I may cite the opinions expressed by
certain botanical writers. Two careful Dutch authors—
van Hall (1834) and Bolsius (1903)—find much that is original
and admirable in Leeuwenhoek’s studies of plants: but the
more famous German botanist Sachs (1875), whose knowledge
of Leeuwenhoek was obviously not profound, says that “
the whole, all his numerous communications, in comparison

1 T possess and have studied all of these, though I do not cite them here.

2 Félix Dujardin (1801-1860), Professor of Zoology at Rennes. For his
life see Joubin (1901). I have also studied—though I do not cite—the
earlier works of this admirable protozoologist.

® Agostino Bassi (1773-1856), of Lodi. See his Opere (1925), recently
reprinted and edited, with a remarkable introduction by the late Prof.
B. Grassi; who sums up his review with the statement that “it is proved
that parasitology, like many other branches of knowledge, had its cradle
in our own Italy: foreigners have merely recognized and perfected it.”
Nevertheless, no Italian saw protozoa or bacteria before the year 1674.

* Moscardino is now supposed to be caused by a fungus (Botrytis) and
pébrine by a protozoon (Nosema)—both of doubtful systematic status.

THE ENVOY 383

with Malpighi’s pleasing clarity and Grew’s systematic
thoroughness, create a painful impression of superficiality
and amateurishness.””* A similar opinion of Leeuwenhoek’s
work in general has, moreover, been recently expressed by one
of his own compatriots (Becking, 1924), who sees in him
merely “a pair of eyes, a pair of hands, directed by other
minds. For when his own mind tried to direct, he could
produce nothing but chaos.” ‘This is surely a strange estimate
of the almost wilfully independent Leeuwenhoek I know—who
certainly produced something very different from chaos when
he discovered the Protozoa and the Bacteria! But even for
these discoveries Becking allows Leeuwenhoek little credit: he
avers that “although he was the first to see bacteria, yeasts
and protozoa, we can not look upon him as the founder of
microbiology.” Despite his obviously great knowledge’ of
Leeuwenhoek, and his own distinction in other branches of
learning, I am unable to judge of Becking’s competence in
protozoology—since he has not (to my knowledge) contributed
as yet anything to the advancement of that science. His
evaluation of Leeuwenhoek may, however, be contrasted with
that of the only man of our times who possessed a profound
knowledge both of the Protozoa themselves and of proto-
zoological history. He not only respected and admired
Leeuwenhoek’s work, but he even dedicated one of his own
most important memoirs to his memory.”

Other biologists have already honoured Leeuwenhoek in
their own peculiar way by naming various organisms after him.
It is true no protozoon or bacterium or other “little animal ”

1 Sachs (1875), p. 264; translated. I have good reasons for believing
that these words were actually plagiarized from an earlier and less-known
author.

2 Becking writes as one who knows all about L., and he says that “ the
uncritical praise of his commentators and biographers can only be ascribed
to an insufficient knowledge of his works and that of his contemporaries.”
Considering Becking’s greater knowledge, I confess that at first I found it
difficult to understand how he could refer to L. as “a humble lens-grinder ”’,
who was ‘a patrician’s son”? and “had many children’’, ete. But such
obvious misstatements of fact are to be explained, doubtless, by his con-
viction that “What really matters in a biography is not the so-called
biographical datum.”’ I differ from him in believing that accurate data are
the szne qua non of any biography.

3 Biitschli (1876).

384 LEEUWENHOEK AND HIS “ LITTLE ANIMALS”

of his own discovering now bears his name:’ yet it has been
bestowed—more or less permanently—upon a minute moth,’ a
tiny mite,’ and an insignificant Australian flowering plant* .. .
“cum rerum Natura nusquam magis quam wm minimis
tota sit.”

My personal estimate of Leeuwenhoek is based upon a
study of his own works. [admit that [have not yet examined
his numerous writings sufficiently, but I have read enough to
realize that those people who ridicule him are generally
ignorant, and usually reveal their own incompetence in the
very act of denouncing his. Whilst professing to show us his
faults they unintentionally pillory themselves. Leeuwenhoek
and his disciples have now no need even to contradict state-
ments such as “this physician described many things that he
never saw,’ or “his assertions . . . sufficiently prove that
he saw less through his microscope with his eyes than with
his imagination:’’’? and nowadays we only laugh when we
read this pronouncement by the self-appointed judge of the
Royal Society—*‘ Lewenhoeck . . . had the good fortune
to be one of the first People who worked at microscopical
Observations, but we are to acknowledge at the same Time,
that he has had the Honour of having stocked the Philo-
sophical Transactions with more Errors than any one Member
of it, excepting only his Successor in Peeping, Mr. Baker.” °

1 The name “ Pandorina leuwenhoekii’’, proposed by Bory de St-Vincent
(1826, p. 22), is an invalid synonym of Volvox globator Linnaeus: while the
same author’s ‘‘ Esechielina lewwenhoekii”’ (1826, p. 78) has been engulfed
in the synonymy of Rotifer vulgaris.

2 Oecophora leeuwenhoekella [Tineidae] F. v. P. Schrank, 1802. For
the various spellings of the specific name see Sherborn (1927). Cf. also Isis
(1839), p. 192.

3 Genus Leewwenhoekia Oudemans, 1911.

4 Levenhookia pusilla Brown, 1810. In proposing the genus, Robert
Brown says (in Latin) that he dedicates it ‘to the memory of the most
famous micrographer, in whose works there are many most beautiful
observations on the structure of vegetables.” Brown’s spelling of the
generic name is curious, and is evidently an attempt to reconcile Dutch
orthography with Latin and with English pronunciation. Later emendations
(such as ‘‘Leevenhokia’”’ van Hall, 1834) can hardly be regarded as
improvements.

° Jourdan (1822), Biogr. Méd., V, 561.

® John Hill (1751), p. 156. The reference is to Henry Baker (see
p. 318 supra), one of Hill’s pet aversions.

THE ENVOY 385

At all times the name of Leeuwenhoek has been mentioned
with respect by those who have really made his acquaintance.
Even general historical writers’ are sometimes aware that he
was one of the phaenomena of the XVII Century: and even
in his own lifetime his claims to recognition were conceded by
biological and medical authors. Leeuwenhoek was no
‘physician ” or “ surgeon ’’, as he has so often been ridiculously
styled: nevertheless, he was already called “celebrated” in
Roukema’s Dictionary of Famous Physicians as early as 1706,
and he now has a whole section to himself in Banga’s History
of Medicine and its Practitioners in Holland (1868) and in
Hirsch’s Biographical Lexicon of Distinguished Doctors of all
Times and Peoples (1886). The great and learned Leibniz
paid attention to his discoveries, which were not without
influence upon his own philosophy: indeed, the abstract
‘““monads”’ of the Monadology are not altogether unrelated to
Leeuwenhoek’s concrete “animalcules”.” But to trace
Leeuwenhoek himself through all the misunderstandings and
misquotations and muddles of the multitudinous authors who
have utilized his discoveries for their own ends, is a task
beyond my competence; and for my present purpose it is,
fortunately, unnecessary.

Leeuwenhoek will be finally judged by his own writings,
and not by anything that other people say he wrote. He has left
us a great mass of records—both published and unpublished
from which we can now extract what we please. I have
endeavoured to recover from them all his observations on the
Protozoa and the Bacteria, and to set in order his inchoate and
uncorrelated findings in a manner which may fairly convey
their import and importance to present-day students. ‘To me
his words, when judicially weighed in the scales of con-
temporary and recent knowledge, prove conclusively that he
was the first protozoologist and the first bacteriologist. He
has had thousands of followers and imitators, and was pre-
ceded by a few prophetic precursors; but his own true place
in Protozoology and Bacteriology appears to me incontro-

1 For example, Hallam in his Literatwre of Europe (published first in
1837-9).

2 Leibniz also mentions L. in his Théodicée (published in 1710). His
correspondence with L. is discussed by Ehrenberg (1845): but the first author
who appears to have realized Leibniz’s intellectual debt to L. is Radl (1905).

25

386 LEEUWENHOEK AND HIS “LITTLE ANIMALS”’

vertible. He was the originator of everything we now know
about ‘‘ microbes ’’, and of all that will ever be known about
these organisms. To say that he is “not the founder of
microbiology . . . although he was the first to see bacteria,
yeasts, and protozoa”? may sound very knowing, and may
satisfy those who seek paradox and literary effect: but every
workaday bacteriologist and protozoologist knows that it is
sheer nonsense. One might equally well say that Columbus
did not discover the New World because he left no account of
New York.

In the foregoing pages I have done my best to portray
Leeuwenhoek and to chronicle some of his great discoveries
anew in his own words. If I have also attempted to represent
other leading figures in the historic scene wherein he himself
appears, it is because I realize that he can be recognized in
his true character only when the other actors are ranged
beside him on the stage. It is not for me, or any other living
man, to design or paint the scenery or to dress the players or
even to clap or hiss their exits and their entrances. I can
but strive to discharge with fidelity the humbler office of the
man who manipulates the limelight—whose duty is to show,
in just illumination, the performers in a drama which I neither
did nor ever could compose, and of whose intricate plot I have
but the roughest working knowledge.

I have always endeavoured to regard Leeuwenhoek
objectively and dispassionately, but I am conscious that I
have not always succeeded: for whenever I listen to his talk
about “little animals” I am carried away by the unintentional
eloquence of his discourse. He speaks an ungrammatical and
old-fashioned language which is not my mother-tongue, and
which I have learned painfully and as yet imperfectly : but he
also echoes a language which I hear oftener than any other—
that of the “little animals” themselves. I have spent all my
working life trying to understand them, but I still know no
more than old Antony knew—just enough, in fact, to inspire
me with the enthusiasm to continue listening and labouring,
but never enough to feel satisfied with my interpretations.
I have unbounded admiration for Leeuwenhoek because he
heard and interpreted things that I, unaided, could never have
discovered, and hit on problems—during quiet nights in his
own private closet—of which neither he nor I can ever know
the final solution.

THE ENVOY 387

One of Leeuwenhoek’s own countrymen has recently called
me his “ greatest living admirer.”* I am proud to admit the
accusation, and this book gives some of the grounds for my
conceit. But the foregoing pages are not meant as an appeal
to the reader’s emotions—only to his reason. “ How Dogma-
tical soever my Assertions may seem to be, yet do I not affect
the unreasonable T'yranny of obtruding upon the Faith of any.
He that speaketh Reason, may be rather satisfied, in being
understood, than believed.” ” Consequently, if my poor labours
succeed in robbing me of a title which I hold but temporarily
and precariously, they will not have been wholly in vain; and
I shall be the first to rejoice when I am deposed from a
position which I do not deserve, cannot maintain, and have
never sought.

As I aim at nothing but Truth, and, so far as in me
lieth, to point out Mistakes that may have crept into
certain Matters; I hope that in so doing those I chance
to censure will not take it ill: and if they would expose
any Errors in my own Discoveries, I’d esteem it a
Service; all the more, because ’twould thereby give me
Encouragement towards the Attaining of a_ nicer
Accuracy.”

1 Dr W. H. van Seters, as reported in the Nieuwe Rotterdamsche Courant
of 13 July 1926 (Nr. 83, blz. 6).

2 Nehemiah Grew (1672), last lines of Preface.

* Translated from L.’s Letter 135 (25 Dec. 1700): published in Brieven,
Sevende Vervolg, p. 307.

388

A SHORT LIST OF LEEUWENHOEK’S WRITINGS

HERE is still no complete edition of all Leeuwenhoek’s
letters: and of those already published there are so
many versions that specific reference to any particular

passage is often a matter of grievous difficulty. The biblio-
graphies already printed by Gronovius (1760), Pritzel (1872),
and many others, are so incomplete and otherwise imperfect
as to be almost worthless. But a committee of experts has
lately been formed in Holland with the object of printing or
reprinting all Leeuwenhoek’s extant writings; and we may
therefore hope that the material for a full and accurate biblio-
graphy will shortly be collected and collated, and placed at the
disposal of the public.

In the meantime, since I have not the leisure or learning
—still less the funds—of the Dutch committee, but owe it to
my readers to give the sources of my own information, I can
only offer the following record of those writings which I have
myself consulted. For the present work I have had to study
every available manuscript and publication in order to collect
the passages relating to protozoa and bacteria, and I have
therefore had to catalogue every discoverable letter and collate
all its versions. But my own private list of Leeuwenhoek’s
writings, so compiled, is still far too faulty to print here—and
also far too long: and moreover this is obviously not the place
to publish such a compilation. I therefore give now only the
briefest indication of my sources for the assistance of fellow-
students.

MANUSCRIPTS

The Leeuwenhoek Manuscripts in the possession of the Royal
Society: 4 volumes, containing also numerous translations,
drawings, and other relevant material. Lmperfectly catalogued
by Halliwell-Phillipps (1840). Referred to, here throughout,
as ‘ Roy. Soc. MSS.” Together with a few letters among the
Boyle MSS. and elsewhere in the Society’s archives, and

LEEUWENHOEK’S WRITINGS 389

including fragments and copies of letters addressed to others,
they amount approximately to 200. At present I cannot
enumerate them more exactly. (Their number is grossly
overstated by most previous authors, who apparently count
originals and translations and printed proofsheets as “ original
manuscripts.) As these manuscripts form the basis of the
present work, I may add the following notes upon them:

The Roy. Soc. MSS. (mostly Dutch) were very incompletely
and imperfectly printed in the form of extracts or abstracts,
in English or Latin, in contemporary numbers of the Philo-
sophical Transactions and Hooke’s Philosophical Collections
(which replaced the Transactions between Vol. XII, 1678-9,
and Vol. XIII, 1682-3). These periodicals contain approxi-
mately 120 printed “ extracts’ from Leeuwenhoek’s letters,
though the “extracts” do not represent exactly the same
number of original letters. The printed versions will all be
found in Phil. Trans. Vol. VIII (1673) to Vol. XXXII (1723)
inclusive [none in Vols. XVI and XXX], and are indexed—
more or less accurately—by Maty (1787). Similar “ extracts”
from 2 letters were included in Hooke’s Lectures and Collections
(1678)—reprinted in his Lectiones Cutlerianae (1679)—and of
3 others in his posthumous Philosophical Haperiments and
Observations edited by Derham (1726).

Many of these manuscripts were published in full, however,
in Leeuwenhoek’s printed Dutch and Latin collective works,
and 14 of the previously wholly unpublished early Dutch
letters have just appeared in Opuscula Selecta Neerlandicorum,
Vol. IX (1931): while two of the letters sent to the Royal
Society, together with a fragment of Letter 116, have passed
somewhat mysteriously into the Sloane MSS. now preserved
in the British Museum. (I say ‘mysteriously’ because the
honourable Sir Hans Sloane, M.D., had no obvious right to
incorporate any of Leeuwenhoek’s original letters, addressed
to him as Secretary of the Society, in his own private
collection.)

Other surviving manuscripts of Leeuwenhoek are known to
me only through more or less recently printed versions or
descriptions. I have not yet been able to study all the
originals, but note their existence here for the help of others:

The Leeuwenhoek Manuscripts in the Huygens Collection at
Leyden (University Library). Eight in number, and now
printed in Guvres Complétes of Chr. Huygens (see especially

“cc

390 LEEUWENHOEK AND HIS “LITTLE ANIMALS”

Vol. VIII; 1899) or by Vandevelde and van Seters (1925).
Also partially printed or abstracted by Snelleman (1874),
Haaxman (1871, 1875), Vandevelde (1924a). [Some of the
MSS. known to Haaxman (1875) have seemingly since
disappeared. They were apparently removed by a former
librarian, who claimed them as his private property.}| A
complete list of these MSS., with 5 others (one published)
which I have not been able to trace further, is given by
Harting (1876, pp. 121-3).

The Leeuwenhoek Manuscripts in the National Library at
Florence. These letters (about 15) were all addressed to
Magliabechi,, and have been partly printed by Targioni-
Tozzetti (1745) and Carbone (1930). [The latter erroneously
includes among them a letter written by Leibniz,’ and
previously published as such by Targioni-Tozzetti (1746). ]

Four [? three] Leeuwenhoek Manuscripts in the Municipal
Museum at The Hague. They are discussed, and their contents
described, by Servaas van Rooijen (1905).

Manuscript of a Letter (dated 3 [?13] March 1716) to
Leibniz. Preserved among the Leibniz MSS. at Hanover
(fide Khrenberg, 1845), together with drafts of 3 letters from
Leibniz to Leeuwenhoek. [This letter—Send-brief XX—was
published in full in L.’s Dutch and Latin collected works. |

PUBLICATIONS

No serious attempt has yet been made by any bibliographer
to collect and collate all Leeuwenhoek’s numerous printed
letters. His published writings have been, indeed, the despair
of all authors who have had occasion to refer to them; and I’
do not, therefore, pretend to describe or enumerate all their
many versions here.

Leeuwenhoek himself published in his lifetime 165 letters
(not counting letters contained within letters): and to these

1 Antonio Magliabechi (1633-1714), a Florentine scholar of prodigious
learning. This remarkable man—of poor parentage—became librarian to
Duke Cosmo III of Tuscany: and though he published nothing during his
lifetime he is said to have been himself “ a walking library ” (including the
dust and cobwebs, apparently). L. wrote to him because he had heard that
he was then the most learned man in Italy: and he also dedicated to him
his Latin edition entitled Arcana Naturae Detecta (1695).

2 Cf. p. 46, note 1, and p. 359 supra.

LEEUWENHOEK’S WRITINGS 391

he assigned numbers—in chronological order. He published
them, however, in two separate series—the first numbered
with arabic numerals, the second with roman. But the first
series began with No. 28* (not No. 1) and ran to No. 146, and
thus consisted of 119 letters in all: while the later series
(46 letters) was consistently numbered from I to XLVI.
This, in itself, is apt to cause confusion: but the difficulty of
collation is increased because the letters were not originally
published always in strict chronological order, and were
frequently, on their first issue, not numbered at all. Their
seriation can therefore be determined only by their dates, or
by the numbers assigned to them in later issues, editions, or
translations.

All the letters originally printed in Dutch, under Leeuwen-
hoek’s supervision, were translated into Latin and printed in
that language; but the Dutch and Latin versions were not
issued simultaneously.” (As a rule—but not invariably—the
Dutch versions preceded the Latin.) Furthermore, the letters
—whether in Dutch or in Latin—generally made their appear-
ance a few at a time in the form of a brochure with a common
title: while a little later another collection would appear—
often printed for a different publisher and with a different
title—and in this some of the earlier letters were often incor-
porated. The final complete collections of Leeuwenhoek’s
letters were made up of these earlier partial collections—of
various issues—and new editions; and, in the case of the
Latin translations, sometimes of entirely new versions corrected.
and amended almost beyond recognition.

The following is a short list of the chief printed versions
—both Dutch and Latin—which I have myself been able to
study, together with a few notes [in square brackets] which
may be serviceable to others. The arrangement is chrono-
logical (for either language), and the names of publishers
are given in parenthesis after the place and date of publica-
tion. Numbers are prefixed merely for convenience of present
reference, and have no other significance.

1 Cf. p. 356 swpra, and Dobell (1931).

2 By far the best list is that given in Harting (1876, pp. 132-139): but
this publication is itself so rare that few authors can nowadays refer to it.
My own copy was most generously presented to me by the late Prof. M. W.
Beijerinck—after I had for years vainly attempted to obtain one through
booksellers.

392

LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

I. DutcH EDITIONS

Ondervindingen en Beschouwingen der onsigtbare geschapene waarheden,
vervat in verscheydene Brieven, geschreven aan de Wijt-beroemde
Koninklijke Societett in Engeland. 4°. Leyden, 1684 (van
Gaesbeeck). [pp. viii + 8 + 32. Contains Letters 32 & 33,
unnumbered and paged separately. Figs. engraved in text.]

Ondervindingen en Beschouwingen der onsigbare geschapene waarheden,
waar in gehandeld werd vande Evyerstok [enz. enz.]. 4°. Leyden,
1684 (van Gaesbeeck). [pp. ii + 21 + 19. Contains Letters 37
& 39, unnumbered and separately paged. Figs. engraved in text.]

(a) Another edition of Letter 37 entitled: Antony van Leeuwenhoeks
37ste Missive, Geschreven aan de Heer Cristopher Wren. 4°. [Lugd.
Bat. 1696 ?] [No preliminary leaves: paged 1-20 (not 21, as in
orig. ed.), and with different make-up.]

Ondervindingen en Beschouwingen der onsigbare geschapene waarheden,
waar in gehandelt wert vande Schobbens inde Mond [enz.]. 4°.
Leyden, 1684 (van Gaesbeeck). [pp. iv + 24. Contains Letter
40: unnumbered, with figs. engraved in text.]

(a) Another edition, entitled: Antoni van Leeuwenhoeks 4Oste
Missive, Geschreven aan de Heer Francois Aston. 4°. [Lugd.
Bat. 1696 ?] [No preliminary leaves: pp. 1-24, identical with
Ist ed.]

Ondervindingen en Beschouwingen der onsigbare geschapene waarheden,
waar in gehandeld werd over het maaksel van’t Humor Cristallinus
[enz.]. 4°. Leyden, 1684 (van Gaesbeeck). [pp. ii + 26.
Contains Letter 41: unnumbered, with figs. engraved in text.]

Later edition: see No. 17.

Oniledingen en Ontdekkingen van de onsigtbare Verborgentheden ; vervat
in verscheyde Brieven, geschreven aan de Wyd-vermaarde Koninklijke
Wetenschap-soekende Societeyt tot Londen in Engeland. 4°.
Leyden, 1685 (Boutesteyn). [pp. 88, but mispaginated 79-94
from p. 72 to end. Contains Letters 38, 42, 43; unnumbered, and
with continuous pagination. All figs. engraved in text.]

(a) Another edition [? 2nd] dated 1691. [non vidi.]

(0) Another edition [? 3rd] dated 1698. Same title and publisher,
but with letters numbered.

Ontdekkingen en Ontledingen van Sout-figuren van verscheyden Souten :
van Levendige Dierkens in de Mannelyke Saden de Baarmoeder
ingestort ; ende van de Voort-telinge [enz.]. 4°. Leyden, 1685
(Boutesteyn). [pp. 76. Contains Letters 44 & 45; unnumbered,
and with continuous pagination. ]

(a) Second edition, zbid. 1696: with letters numbered (but 45 mis-
numbered 46.)

Ontledingen en Ontdekkingen van het Begin der Planten in de Zaden
van Boomen [enz.|. 4°. Leyden, 1685 (Boutesteyn). [pp. 78.
Contains Letters 46 & 47: unnumbered, and with continuous
pagination. |

(a) Another [? 2nd] edition, ibid. 1697. Letters likewise unnumbered.

LEEUWENHOEK’S WRITINGS 393

8. Oniledingen en Ontdekkingen van levende Dierkens in de Teel-deelen
van verscheyde Dieren, Vogelen en Visschen ; van het Hout met der
selver meningvuldige Vaaten [enz.]. 4°. Leyden, 1686 (Boutesteyn).
[Engraved title (dated 1685) + pp. 40 + 35. Contains Letters
28, 29, 30,31; and 34, 35, 36—each series continuously paginated
separately. Letters all unnumbered. |

(a) Second edition, 1bid. 1696. Letters numbered.

9. Ontledingen en Ontdekkingen van de Cinnaber naturalis, en Bus-poeder ;
van het maaksel van Been en Huyd {enz.|. 4°. Leyden, 1686
(Boutesteyn). [pp. 110. Contains Letters 48, 49, 50, 51, 52:
unnumbered, and with continuous pagination. |]

(a) Another edition; Leyden, 1713 (Langerack)—with letters still
unnumbered.

10. Vervolg der Brieven, geschreven aan de Wvytvermaarde Koninglijke
Societeit in Londen. 4°. Leyden, 1687 (Boutesteyn). [pp. viii
+ 155. With engraved portrait. Contains Letters 53-60: all
except the first (53) numbered, and with continuous pagination. }

(a) Second edition, ibid. 1688.
(6) Another [? 3rd] edition, zbid. 1704.

* In the preliminary pages the publisher gives a list of all L.’s letters from
No. 28 to No. 52, with their dates, publishers, titles, and contents (but not dates
of publication).

11. Den Waaragtigen Omloop des Bloeds, Als mede dat De Arterien en Venae
Gecontinueerde Bloed-vaten zijn, Klaar voor de oogen gestelt. Ver-
handelt in een Brief, geschreven aan de Koninglyke Societett tot
Londen. 4°. Delff, 1688 (Voorstad). [pp. ui (title-p.) + 1-30:
1 folding plate. Contains Letter 65 only—numbered.]

12. Natuurs Verborgentheden Ontdekt: zyjnde een Tweede Vervolg der
Brieven, geschreven aan de Koninglijke Societeit tot Londen. 4°.
Delff, 1689 (Voorstad). [pp. ii (titlepage) + 157-350 (mispaginated
after p. 260). Contains Letters 61-67, all numbered.|

(a) Second edition ; Delft, 1697 (Kroonevelt).

13. Derde Vervolg der Brieven, geschreven aan de Koninglyke Soctetett tot
Londen. 4°. Delft, 1693 (van Kroonevelt). [pp. vii + 351-
531. Contains Letters 68-75: all numbered, and continuously
paginated. |

14. Vuierde Vervolg der Brieven, geschreven aan de Wytvermaarde Konink-
lijke Societeyt in London. 4°. Delft, 1694 (van Kroonevelt).
[pp. li (titlepage) + 533-730. Contains Letters 76-83: all num-
bered, and continuously paginated. |

15. Vuijfde Vervolg der Brieven, geschreven aan verscheide Hoge Standsper-
sonen en Geleerde Luijden. 4°. Delft, 1696 (van Krooneveld).
[Engraved title (dated 1696), pp. vi + 172 + x (Blad-wyser).
Contains Letters 84-96: all numbered, and with continuous pagina-
tion. |

16. Sesde Vervolg der Brieven, geschreven aan verscheide Hooge Stands-
personen en Geleerde Luijden. 4°. Delft, 1697 (van Krooneveld).
[pp. iv + 173-342 + x (Blad-wyser & Druk-feilen). Contains
Letters 97-107: all numbered and continuously paginated.]

394

“7.

18.

LS:

20.

21.

22.

LEEUWENHOEK AND HIS “LITTLE ANIMALS”’

A. van Leeuwenhoeks 4rste Missive, Geschreven aen de Koninklijke
Societeit tot Londen [enz.]. 4°. Delft, 1698 (van Kroonevelt).
[pp. li + 26. Apart from title, and preliminary page in former,
identical with Gaesbeeck’s ed. of 1684 (No. 4).]

Sevende Vervolg der Brieven, waar in gehandelt werd, van veele Opmerkens
en verwonderens-waardige Natuurs-Geheimen. 4°. Delft, 1702
(van Krooneveld). [pp. vi + 452 + xxii (Blad-wyser). Contains
Letters 108-146 : all numbered, and continuously paginated.]

Send-Brieven, zoo aan de Hoog-edele Heeren van de Koninklyke Societeit
te Londen, als aan andere Aansienelyke en Geleerde Lieden [enz.].
4°. Delft, 1718 (Beman). [Engraved title with portrait inset
(dated 1718), pp. xiv + 460 + xxviii (Register & Druk-fouten).
Contains Letters I-XLVI, numbered and continuously paged.]

BRIEVEN [seu WERKEN]. 4°. 4 vols. (or sometimes 5). Various
dates, publishers, and places.—The final Dutch collective edition
of all L.’s published letters. Contains Letters 28-146 and I-XLVI,
and is variously made up of the several separate issues already
listed—bound together. With 2 portraits, engraved titles, and
numerous engraved figs. in text and on inserted plates. Perfect
copies, composed of first editions throughout, and with all the
plates, are now extremely rare. The following is a short description
of the only one (my own) which I have yet seen :

Deel I—Made up of Nos. 1, 2, 3, 4, 5, 6, 7, 8, 9: thus containing
Letters 28-52. With engraved title dated 1685 (1st state, with
Dutch lettering ‘“‘ Ontdeckte Onsigtbaar-heeden’’).

Deel IIT = Nos. 10, 12, 13, 14. Letters 53-83. With engraved
portrait prefixed (de Blois, after Verkolje: Ist state, with
Dutch lettering).

Deel III = Nos. 15, 16, 18. Letters 84-146. Engraved title
dated 1696 (2nd state, with Dutch lettering).

Deel IV = No. 19. Letters I-XLVI (Send-brieven), with engraved
title dated 1718 (1st state, with Dutch lettering at foot), having
Goeree’s portrait inset.

If. Latin EDItions

Anatomia et Contemplatio Nonnullorum Naturae invisibilium Secretorum
Comprehensorum Epistolis Quibusdam Scriptis ad Illustre Inclytae
Societatis Regiae Londinensis Collegium. 4°. Lugd. Batavorum,
1685 (Boutesteyn). [pp. 78. Contains Letters 43, 42, 38—in
this order—with all figs. engraved in text. Letters wnnumbered :
continuous pagination. Excessively rare first Latin edition.
My own copy is the only one which I have seen. No copy in
British Museum, or hitherto discovered in any library in Britain.]

Anatomia Seu interiora Rerum, Cum Animatarum tum Inanimarum {sic},
Ope & nebeficio [sic] exquisitissimorum Microscopiorum Detecta,
variisque experimentis demonstrata [etc.]. 4°. Lugduni Bata-
vorum, 1687 (Boutesteyn). [pp. vi + 64 (mispaginated 58) +
260 (mispaginated 258). Two parts—each continuously paged—

23.

24.

25.

26.

27.

LEEUWENHOEK’S WRITINGS 395

containing respectively Letters 43, 42, 38, and Letters 28, 29, 30,
31, 34, 35, 36, 46, 47, 44, 45, 48, 49, 50, 51, 52 (in this order).
All letters unnumbered. Figs. partly engraved in text, and partly
inserted as separate plates. With engraved title of No. 8, but
Dutch words erased. ]

A Second Issue of the preceding (No. 22) with the misprints
“inanimarum ” and “ nebeficio”’ in title corrected to inanimatarum
and beneficio. Same date, place, and publisher. [In the copy in
my possession—the only one which I have collated—the first part
(Letters 43, 42, 38) is paged 3-78, and is a reprint of these pages in
No. 21 (not 22). The mispagination of Part II is also partially
corrected. |

(a) Editio novissima, prioribus emendatior [retranslation, with letters
still unnumbered]. 4°. Lugd. Bat., 1722 (Langerak).

Continuatio Epistolarum, Datarum Ad longe Celeberrimam Regiam
Societatem Londinensem. 4°. Lugduni Batavorum, 1689 (Bou-
testein). [pp. viii (title & indices) + 124. Contains Letters 53-60,
in order; with continuous pagination but unnumbered.]

(a) Second edition ; Lugd. Bat. 1696 (Boutestein).

(0) Third edition; Lugd. Bat. 1715 (Du Vivie, Haak, & Langerack).
Letters unnumbered.

(c) Another [? 4th] edition, Lugd. Bat. 1730 (Langerak). Letters
unnumbered.

Arcana Naturae Detecta. 4°. Delphis Batavorum, 1695 (Krooneveld).
[Engraved portrait and title (same as No. 15, but with Latin
lettering and dated 1695) + pp. vi + 568 + xiv (index & emen-
danda). Contains Letters 32, 33, 37, 39, 40, 41, 61-92, with con-
tinuous pagination. Letters 32-41 unnumbered: 61-92 numbered.]

(a) Second edition ; Lugd. Bat. 1696 (Boutestein).

(0) Third edition; Lugd. Bat. 1708 (Boutestein).

(c) Editio novissima, auctior et correctior; Lugd. Bat. 1722
(Langerak).

Continuatio Arcanorum Naturae detectorum, qua continetur quicquid
hactenus ab Auctore lingua Vernacula editum, & in linguam Latinam
transfusum non fuit. 4°. Delphis Batavorum, 1697 (Kroonevelt).
[pp. i + 192 + viii (index). Contains Letters 93-107 : all numbered,
and with continuous pagination.]

(a) Reprint, with new titlepage, Lugd. Bat. 1722 (Langerak).

Epistolae ad Societatem Regiam Anglicam, et alios Illustres Viros Seu
Continuatio mirandorum Arcanorum Naturae detectorum [etc.].
4°. Lugduni Batavorum, 1719 (Langerak). [Portrait + pp. xvi
(title & index) + 429 + x (2nd index). Contains Letters 108-146,
all numbered and continuously paged. Lat. transl. of No. 18.]

Epistolae Physiologicae Super compluribus Naturae Arcants [{etc.] :
hactenus numquam editae. 4°. Delphis, 1719 (Beman). ([En-
graved title, with portrait inset (same as No. 19, but with Latin
lettering at foot, and dated 1719); pp. xx (title, dedication, &
summary) + 446 + xxvi (index & errata). Contains Letters
I-XLVI; all numbered, and paged continuously. Latin
translation of No. 19.]

396 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS ”’

29. OPERA OMNIA, seu Arcana Naturae, ope Exactissimorum Microscopiorum
Detecta, experimentis variis comprobata, Epistolis, ad varios illustres
Viros, ut et ad integram, quae Londini floret, sapientem Societatem
... datis. 4°. 4Avols. Lugduni Batavorum, 1722 (Langerak).—
This is the Latin equivalent of No. 20, and contains all the Epistolae
from 28 to 146 and I-XLVI. It is made up of various editions and
issues, and most copies which I have collated are imperfect. The
usual arrangement is as follows (though many other collections
are to be found) :

Vol. I = Nos. 23a (part i), 22 (ii), 240. [Engraved title of No. 25,
general title, and 12 other preliminary pages (carmen panegyricum,
lectort typographus, & index): pp. 1-64 + 1-260: Index triplex
[pp. xxiv]: title, pp. vi (fraemonitio ad lectorem & index) +
1-124. Contains, therefore, Letters 43, 42, 38; 28, 29, 30, 31,
34, 35, 36, 46, 47, 44, 45, 48, 49, 50, 51, 52; 53-60.]

Vol. II = Nos. 25¢ & 26a. [Engraved title of Nos. 8 & 22,
with new Latin lettering; new titlepage + pp. xiv (index)
+ 1-515; Index (pp. xxiii + errata) ; new titlepage + Index
argumentorum (pp. vill) + pp. 1-192 + Index (pp. viii). Contains,
therefore, Letters 32, 33, 37, 39, 40, 41, 61-92 ; and 93-107.]

Vol. III = No. 27. [Portrait + title with engraved device
+ pp. xiv (index 1) + pp. 1-429 + x (index 2). Containing
Letters 108-146. ]

Vol. IV = No. 28. [Containing Letters I-XLVI.]

* All these volumes contain numerous figures engraved in the text
and on large and small inserted plates—identical with those
of No. 20.

In addition to the foregoing publications, I must record the following—
issued in Leeuwenhoek’s lifetime but not by himself. [All the
original MSS. appear to be lost.]

The Letters addressed to Petrus Rabus.—Pieter Rabus (1660-1702 ;
Dutch author, poet, and critic) published in the last decade of
the XVII Century a literary review entitled ‘“‘ De Boekzaal van
Europe”’ (8°. Rotterdam). Two volumes were issued yearly—
separately paged—from 1693 to 1700: and in those published
between 1693 and 1697 Rabus not only reviewed those works
of Leeuwenhoek which appeared contemporaneously, but he
also printed several of his letters addressed to himself. As
these are not to be found elsewhere, and as they are not correctly
cited by van der Aa or others, I add exact references here. Apart
from reviews, and letters printed elsewhere, Rabus published—
more or less completely—six of L.’s letters which are otherwise
unknown. To wit: .

1. A letter dated 27 Oct. 1693. Boekzaal v. Europe 16938 (ii),
pp. 554-5. [Extract only.]

2. Letter dated 21 May 1695. Jbzd., 1695 (i), pp. 532-6.
{Extract.]

3. Letter undated. Jbid., 1695 (ii), pp. 96-9.

LEEUWENHOEK’S WRITINGS 397

4. Letter dated 10 Sept. 1695. Jbdid., 1695 (ii), pp. 258-261.

5. Letter dated 1 June 1696. Jbid., 1696 (i), pp. 522-5. [In-
complete. ]

6. Letter dated 23 July 1696. Jbid., 1696 (ii), pp. 144-151.

* There is nothing of protozoological or bacteriological importance in this otherwise
interesting correspondence.

The Letters to Magliabechi, partly published by Targioni-Tozzetti
(1745), have already been noted under “‘ Manuscripts ”’ (p. 390)—
together with several other letters more recently printed in
whole or in part.

The only extensive (though very incomplete) English Translation
of Leeuwenhoek’s works is the bowdlerized version of the Rev.
Samuel Hoole (1798, 1807), to which a fuller reference will be
found in the ensuing general bibliography (p. 410).

iby sprack oock van de boomen;
Yan den cederboom aen, die op den
Libanon ts, tot op den psop die aen
den wandt uptwast: by sprack
oock van bet vee, ende van bet
Gevogelte, ende van de Rruyppende
dieren, ende van de Visscbhen.

—I. Kon. iiij. 33.

398

OTHER REFERENCES AND SOURCES

HE following list contains all the works referred to in
ale the foregoing text, and also a number of other publica-
tions upon which I have relied for information—or
which I have had to read—but to which no specific allusion is
made elsewhere. Annotations are added where they appear
needful.

Various national and general biographical dictionaries, of
which I have naturally made considerable use, have been cited
throughout by abbreviated titles. They are as follows (other
articles or publications being given, as a rule, under their
individual author’s or editor’s name):

Allg. Dtsch. Biogr. = Allgemeine Deutsche Biographie. 8°. 56 vols. (with
supplements). Leipzig. 1875-1912.

Biogr. Ital. Ill. = Biografia degli Italiani Illustri, ed. E. de Tipaldo. 89.
10 vols. Venezia. 1834-1845.

Biogr. Méd. = Biographie Médicale: Dictionaive des Sciences médicales,
ed. A. J. L. Jourdan. 8°. 7vols. Paris. 1820-1825.
Biogr. Nat. Belg. = Biographie Nationale ... de Belgique. 8°. 22 vols.

Bruxelles. 1866-1920.

Dansk Biogr. Lex. = Dansk Biografisk Lexikon, ed. C. F. Bricka. 8°.
19 vols. Kjébenhavn. 1887-1905.

Dict. Nat. Biogr. = Dictionary of National Biography, ed. Leslie Stephen
and Sidney Lee. 8°. 70 vols. (with supplements). London &
Oxford. 1885-1927.

N. Nederl. Biogr. Woordenb. = Nieuw Nederlandsch Biografisch W oordenboek,
ed. P. C. Molhuysen, P. J. Blok, & Kossmann. 8°. 8vols. Leiden.
1911-1930.

Nouv. Biogr. Gén. = Nouvelle Biographie Générale (seu Universelle), ed.
F. Hoefer. 8°. 46 vols. Paris. 1855-1866.

AA, A. J. VAN DER (1852-1878). Biographisch Woordenboek der Nederlanden.
8°. 21 vols. Haarlem. [L. in vol. XI (1865), pp. 280-283.]

Apams, G. (1746). Muicrographia Illustrata, or the Knowledge of the
Microscope Explain’d [{etc.]. 4°. London. [L.’s observations
much quoted, and many of his figures reproduced. ]

Apams, G. (1798). Essays on the Microscope [etc.]. 2nd ed. by F.
Kanmacher. 4°. London. {Second-hand description of L.’s
“single microscope,”’ p. 7.]

REFERENCES AND SOURCES 399

AGNEW, D. C. A. (1886). Protestant Exiles from France, chiefly in the reign
of Lows XIV ; or, The Huguenot Refugees and their Descendants
in Great Britain and Ireland. (8rd ed.) Fol. 2 vols. London.
[Printed for private circulation. ]

Anpry, N. (1700). De la Générvation des Vers dans le Corps de Homme.
8°. Paris. [Another edition, 12°. Amsterdam, 1701. 3rd ed.,
8°. 2 vols. Paris, 1741. Engl. transl. 8°. London, 1701.]

Anonymus (1658). The Dutch-Tutor [etc.]. 8°. London.

Anonymus (1662). Waulhelmus en Mauritius van Nassouw, Prince van
Oranjen. Haer Leven en Bedryf. 12°. Amsterdam.

Anonymus (1677). ““ Letter to the Publisher ” from ‘‘ an observing person
in the country.” Phil. Trans., vol. XII, No. 136, p. 889.
Anonymus (1679). Receuil d’Experiences et Observations sur le Combat,
qui procede du mélange des corps. Sur les Saveurs, sur les Odeurs,
Sur le Sang, Sur le Lait, Gc. 12°. Paris. [No. 3, pp. 221-262,
is a French transl. of L.’s letters on blood and milk in Phil. Trans.
The translation is attributed to “ Mr. Mesmin”’ by Rotermund

(1810) and Hoefer (1860).]

Anonymus (1695). Register (verstrekkende te gelijk voor een kort Inhoud)
van alle de Werken van de Heer Antoni van Leeuwenhoek. 4°.
Leiden. [Anonymously compiled index to the early letters—by
“een Beminnaar der Natuurlijke-weteschappen.” In 2 parts.]

Anonymus (1703). An Extract of some Letters sent to Sir. C. H. relating
to some Microscopical Observations. Phil. Tvans., vol. XXIII,
No. 284, p. 1357.

Anonymus (1703a). Two Letters from a Gentleman in the Country,
relating to Mr. Leuwenhoeck’s Letter in Transaction, No. 283.
Phil. Trans., vol. XXIII, No. 288, p. 1494.

Anonymus (1710). Les Delices de la Hollande. 12°. 2 vols. La Haye.

Anonymus (1880). Herdenking van Jan Swammerdam’s 200-jarige Sterfdag,
op 17 Februari 1880. 8°. Amsterdam. (Genootschap tot Bevor-
dering van Natuur-, Genees-, en Heelkunde.)

Anonymus (1909). Een gedenkteeken voor Antony van Leeuwenhoek.
Wereldkrontek (Rotterdam), 10 April 1909, p. 26.

Anonymus (1923). Antony van Leeuwenhoek (1632-1723). J. Amer.
Med. Assoc., LXXXI, 1613. [Worthless.]

Anonymus (1927). The living world no man had seen and how its gates
were opened. My Magazine (London), XXIII, 561. [An account
of L. written for children. Worthless.]

ARBER, A. (1913). Nehemiah Grew 1641-1712. Makers of British Botany,
pp. 44-64. [See OLIVER (1913).]

Astruc, J. (1767). Mémoires pour servir a lV Histoire de la Faculté de
Medecine de Montpellier. 4°. Paris.

BAAN, J. VAN DER (1874). Antonie van Leeuwenhoek. De Navorscher
(Amsterdam), Jaarg. XXIV (N.S. VII), p. 100.

Bacon, F. (1889). Novum Organum, ed. T. Fowler. 8°. Oxford. [First
published 1620. ]

Baker, K. E. von (1864). Johann Swammerdam’s Leben und Verdienste
um die Wissenschaft. Reden ... und kleinere Aufsédtze ver-
mischten Inhalts, I, 1. [Whole work in 3 vols., 1864-1873. 8°.
St. Petersburg. Lecture delivered in 1817.]

400 LEEUWENHOEK AND HIS ‘‘ LITTLE ANIMALS ”’

Baker, H. (1740). An account of Mr. Leeuwenhoek’s microscopes. Phil.
Trans., XLI, (No. 458) 503.

BAKER, H. (1742). The Microscope made Easy. 8°. London. [Dutch
transl. Het Microscoop gemakkelyk gemaakt. Amsterdam, 1744.]|

BAKER, H. (1743). An Attempt towards a Natural History of the Polype.
8°. London.

BAKER, H. (1753). Employment for the Microscope. 8°. London.
[Dutch transl. Nuttig Gebruik van het Mikroskoop. 2 ed.
Amsterdam, 1770.]|

BAKKENES, H. C. VAN (1873). Antonie van Leeuwenhoek. De Navorscher
(Amsterdam), Jaarg. XXIII (N.S. VI), p. 594.

Banca, J. (1868). Geschiedenis van de Geneeskunde en van hare Beoefenaren
in Nederland [enz.]. 8°. 2 vols. Leeuwarden. [L. in vol. II,
pp. 609-614.]

Barrow, J. (1896). The Life of Peter the Great. 8°. Edinburgh. [lst
ed. New York, 1845. New ed. with notes, London, 1874.]

BassI, A. (1925). Opere . . . scelte e pubblicate a cura del Comitato Nazio-
nale per la ristampa. 8°. Pavia.

BASTER, J. (1759). Natuurkundige Uitspanningen, behelzende eenige waar-
neemingen, over sommige Zee-planten en Zee-insecten {[etc.]. 4°.
Haarlem. [Also published in Latin: Opuscula subseciva .. .
Same form, date, and place. ]

BAuMANN, E. D. (1915). De Dokter en de Geneeskunde. 8°. 2 vols.
Amsterdam. [Nederl. Kultuurgeschk. Monogr. IV & V. For
iLsee vols Th pi 24.. Trvial.|

BECKING, L. B. (1924). Antoni van Leeuwenhoek, immortal dilettant
(1632-1723). Scientific Monthly (New York), XVIII, 547.

BEER, H. DE & LAURILLARD, E. (1899). Woordenschat. Verklaring van
woorden en uitdrukkingen. 8°. ’s-Gravenhage.

BEIJERINCK, M. W. (1913). De infusies en de ontdekking der bacterien.
Jaarb. Kon. Akad. Wetensch. (Amsterdam), pp. 1-28 [separate].

BENSE, J. F. (1925). Anglo-Dutch Relations from the Earliest Times to
the Death of William the Third. 8°. The Hague.

BiBii1A, dat is De gantsche H. Schrifture . . . door Last der Hoogh-Mog :
Heeren Staten Generael . . . wyt de Oorspronckelicke talen in onse
Nederlandtsche tale over geset (1702). Gr. fol. Te Dordrecht en
t’Amsteldam.

BIpDLoo, G. (1698). Brief... aan Antony van Leeuwenhoek ; wegens de
dieren, welke men zomtyds in de lever der Schaapen en andere beesten
vind. 4°. Delft. [Also in Latin, 4°. Lugd. Bat. 1698. Re-
printed in B.’s Opera Omnia, Lugd. Bat. 1715. English transl.
in Hoole’s Select Works of L., vol. I, part 2 (1798). The Dutch
edition is extremely rare. |

BircuH, T. (1756-7). The History of the Royal Society of London, for Im-
proving of Natural Knowledge, from its First Rise. 4°. 4 vols.

London.
B JORNSTAHL, es (1780-84). Resa til Frankrike, Italien, Sweitz, Tyskland,
Holland, Angland, Turkiet, och Grekeland . . . efter des Dod

utgifuen af C. G. Gjorwell. 8°. 6 vols. Stockholm. [German
transl. (C. H. Groskurd). Leipzig & Rostock, 1780-83.]

REFERENCES AND SOURCES 401

BLANCHARD, E. (1868). Les premiers observateurs au microscope. Les
travaux de Leeuwenhoek. Rev. d. Deux Mondes, XX XVIII année
(2de période), T.76, p. 379 (15 juillet 1868).

BLANCHARD, R. (1889, 1890). Tvaité de Zoologie Médicale. 8°. 2 vols.

Paris.
BLANKAART [=BLANCARDUS], S. (1748). Lexicon Medicum... J. H.
Schulz auct. et emend. . . . denuo recog. M. G. Agnethler. 8°.

Halle. [lst ed. Amsterdam, 1679.]

BLEYSWIJCK, D. vAN (1667). Beschryvinge der Stadt Delft. 4°. 2 vols.
Delft.

BrytH, A. WYNTER (1903). Foods: their Composition and Analysis.
5th ed. (with M. Wynter Blyth). 8°. London. [L. referred to on
pp. 26, 27, 190. The author’s other “‘researches”’ on L. are
recorded by Richardson (1885).]

BoEKE, J. (1920). Leeuwenhoek en Mendel. Vvagen des Tijds (Haarlem),
Jaarg. 46, p. 303. [Trivial. Contains no material information
beyond that given in my note of 1915.]

BoEKE, J. (1923). Anthony van Leeuwenhoek. 24 October 1632—27
Augustus 1723. Vyvragen des Tujds (Haarlem), Jaarg. 49, p. 317.
[Contains nothing noteworthy—except the erroneous date of L.’s
death. ]

Boitet, R. [Publisher & Editor] (1729). Beschryving der Stadt Delft,
behelzende een zeer naaukeurige en uitvoerige verhandeling van
deszelfs eerste oorsprong, benaming, bevolking, aanwas, gelegen-
heid, prachtige en kunstige gedenkstukken en zeltzaamheden .. .
door verscheide Liefhebbers en Kenners der Nederlandsche
Oudheden. Fol. Delft.

Botsius, H. (1903). Antoni van Leeuwenhoek et Félix Fontana. Essai
historique et critique sur le révélateur du noyau cellulaire. Mem.
Pontif. Accad. Rom. Nuovi Lincet, XX, 287.

BONNET, C. (1779-1783). Ciuvres d’Histoire naturelle et de Philosophie.
8°. 18 vols. Neuchatel.

BOREL [= BoRELLvs], P. (1653). Historiarum, et Observationum Medico-
physicarum, Centuria prima [& secunda]. 12°. Castris. [Ex-
tremely rare. Not in the British Museum. Consists of pp. xxiv
-+ 1-240. Century II has a separate title, but pagination is
continuous. |

BoreEL [= BorELtus], P. (1655-6). De vero telescopit inventore, cum brevi
omnium conspiciliorum historia . . . Accessit etiam Centuria obser-
vationum mucrocospicarum. 4°. Hagae-Comitum. [The word
“ microscopicarum ”’ is misprinted as above throughout : while the
place of publication (The Hague) is called Hagae-Comitis on the
separate title of the Centuria.]

BorEL [= Borettus], P. (1656a). Historiarum, et Observationum
Medtcophysicarum, Centuriae IV [{etc.]. 8°. Parisiis. [Not to
be confused with the 2 preceding works. Contains, in addition
to the 200 observations published in 1653 (Centt. I & II), 200
additional ones (Centt. III & IV)— in all 384 pp.]

26

ins

402 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS”’

Bory DE ST.-VINCENT [J. B.] (1826). Essai d’une Classification des Animaux
Microscopiques. 8°. Paris. [xii + 104 pp. From Encyclopédie
Meéthodique (1824), Tom. II, Hist. Nat. des Zoophytes. This
separate issue (containing some new matter) is now extremely
rare—only 100 copies having been printed. Cf. Lauzun (1908),
p. 281. I possess a copy signed by the author. ]}

Bosman, D. B. (1928). Oor die Ontstaan van Afrikaans. 2de ed. 8°.
Amsterdam.

Bostr6ém, A. (1757). Febris Upsaliensis. Amoen. Acad., No. LXXVII.
vol. V, p. 18. Holmiae (1760).

Bourictus, L. G. N. (1924). Anthony van Leeuwenhoek en zijn dochter.
Nieuwe Rotterdamsche Courant, 13 Dec. (Avondblad B.) & 14 Dec.
(Ochtendblad B.) 1924.

Bouricius, L. G. N. (1925). Anthony van Leeuwenhoek de Delftsche
natuuronderzoeker (1632-1723). De Fabrieksbode (Delft), 44
Jaarg., No. 10 (7 Maart 1925). (Offprint, 3 pp. Important,
but no copy yet traced in any English library. ]

Boyer, J. (1894). Joblot et Baker. Rev. Scientif., XX XI ann. (4 sér., T. I),
p- 283.

BRACHELIUS, A. (1666). Historia Nostri Temporis . . . overgezet door
L.v.B. 8°. Amstegdam.

BREDIUS, A. (1885). ets over Johannes Vermeer (“ de Delftsche Vermeer ’’).
Oud-Holland (Amsterdam), III, 217. ([Cf. also «bid. (1910),
XXVIII, 61.]

BREWERTON, E. W. (1930). Entoptic phenomena. Proc. Roy. Soc. Med.,
XXIV, (Sect. Ophthalm.) 45.

BripcEs, J. H. (1914). The Life and Work of Roger Bacon. 8°. London.

BrocarD, H. (1905). Louis de Puget, Francois Lamy, Louis Joblot. Leur
action scientifique d’aprés de nouveaux documents. 4°. Bar-le-
Duc. [Privately printed.]

Brown, R. (1810). Prodromus Florae Novae Hollandiae et Insulae Van-
Diemen. 8°. London. [Genus Levenhookia, p. 572.} .

BROWNE, SIR THomAs (1642). Religio Medici. 8°. London. [Facsimile
ed., London, 1883. ]

BRUGGENCATE, K. TEN (1920). Engelsch Woordenboek. Qed. 8°. 2 vols.
Groningen & Den Haag.

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27

418 LEEUWENHOEK AND HIS “ LITTLE ANIMALS ”

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423

ACKNOWLEDGEMENTS

many unexpected quests, and has brought me into

contact with so many problems and such divers people
(both living and dead), that I now find it difficult to record—
or even, I fear, to remember—all the help which I have
received from others in the course of its compilation. Almost
everybody I know has contributed—wittingly or unwittingly,
directly or indirectly—something towards its fulfilment: and
with negligible exceptions every person whose aid I have sought
has willingly furnished me with information or material. It
is impossible, therefore, to mention here by name all the
friends and colleagues, all the fellow-students and distant co-
workers whom I have never met in the flesh, all the librarians
and antiquarian booksellers and editors and publishers, who
have given me their unstinted assistance at all times. Con-
sequently, I can only beg them, one and all, to accept now
this general acknowledgement of my indebtedness.

But there are some special helpers whose names I cannot
omit to mention specifically. My debt to my two “ Brothers”
I have attempted to repay by dedicating this volume to them.
Without their fraternal encouragement it would never have
been written, and I therefore owe them both more than I can
express—big brother D’Arcy for his unattainable example
and incomparable scholarship in wider fields, little brother
Paul for his equal enthusiasm on common ground. Next
after these I would mention my old friend Mr A. Hastings
White, Librarian (now, alas! in only a consultant capacity) to
the Royal Society, whose knowledge of everything connected
with the Society has been of incalculable assistance. I have
never sought his aid in vain, and he has always placed his
own vast learning at my disposal most liberally.

I am further indebted, in no small degree, to several
good friends in Holland. That great bacteriologist, the late

i ae book has been so long a-writing, has taken me on so

424 LEEUWENHOEK AND HIS ‘“‘ LITTLE ANIMALS”

Professor M. W. Beijerinck of Delft, with characteristic
unselfishness gave me aid both material and spiritual. The
late Mr L. G. N. Bouricius, Archivist of Delft until his
untimely death on 21 February 1929, also supphed me with
much valuable information, and never failed to satisfy my
frequent inquiries to the utmost of his ability. Dr W.H. van
Seters of Leyden, who recently produced the ‘“ Leeuwenhoek
Film,” most kindly communicated—unasked—all his own
incidental findings, together with several original photographs
and a full copy of the captions. Dr E. P. Snijders—formerly
stationed in Sumatra, now Professor at Amsterdam—has given
me not only valuable advice but also a magnificent specimen
of the old Dutch Bible (1702): while Dr A. Schierbeek, at
The Hague, has rendered the kindest assistance in innumerable
ways during the last ten years. To all these unseen Dutch
friends and fellow-students of Leeuwenhoek I owe a debt
which I can never acknowledge sufficiently. They have all
given mé—a foreigner unknown to them _ personally—their
most generous help. Dr C. A. Crommelin, now Professor
of Physics at Leyden, has been equally helpful: but I
mention him separately because he is, happily, not only still
a living student and admirer of Leeuwenhoek but also one
whose hand I have actually shaken. I would also record that
the Netherlands Society of Sciences, at Haarlem, have aided
me by the gift of two important volumes of the Complete
Works of Huygens, which they are editing and publishing on
so sumptuous a scale.

Among my own countrymen who have given me continued
support I must mention particularly Professor William
Bulloch, F.R.S., and Professor F. J. Cole, F.R.S. The first—
as all real students everywhere know— possesses an unrivalled
knowledge of the history of bacteriology (and of medicine in
general): the second is now our only living authority on the
history of zoology. Both have given me the benefit of their
own solid learning on countless occasions. If I have not
profited by it, the fault is mine.

To the Council of the Royal Society I am beholden for
sranting me the facilities necessary to undertake this work ;
and to the Trustees of the National Gallery and the Directors
of the Rijks-Museum and the Mauritshuis for permission to
reproduce the pictures shown in four of my plates.

Finally, I wish to acknowledge my deep personal obligation

ACKNOWLEDGEMENTS 425

to my friend Mrs Mabel Selle, who has accurately typed the
greater part of this book: for without her expert aid I could
never have sent my original troublesome and _ repeatedly
corrected and revised manuscript to press at the appointed
hour. To my English printers and publishers, Messrs. Bale
and Danielsson, I am indebted no less: for they have invari-
ably met my tiresome typographical and other requirements
in the most sympathetic and magnanimous manner.

For mistakes I alone am responsible, and to those who
will point them out I shall ever be grateful. I have done my
best; yet I know all too well “ Het en kan niet wesen, datter
geen ergernissen en komen: doch wee hem door welcken sy
komen—It is impossible but that offences will come, but wo
unto him through whom they come” (St LUKE xvi, 1).

FINIS

426

INDEX

* This Index covers the whole of the foregoing work—text, notes, and bibliography.
It is a key to the book as a whole, and furnishes clues to all the information contained
in it—with its sources—and an indication of all the chief persons and genera of

animals and plants mentioned.

** Here, as elsewhere in all notes throughout, the abbreviation ‘“‘L.” stands for

ANTONY VAN LEEUWENHOEK.

Aa, A. J. van der 175, 396, 398

Académie des Sciences 53 sq

Acipenser 139

Actinosphaerium 381

Adams, G. (sen.) 379, 398

Adams, G. (jun.) 398

Agnew, D. C. A. 61, 399

Amsterdam 23

Amylobacter 198

Anaerobic bacteria 197 sqq

Andry, N. 399

Anguillula aceti, vide Vinegar-eel

Animalcules seu ‘ little animals ’
[=Protozoa & Bacteria}, passim

Anne, Queen 317

Anodonta 207 sqq

Anonymi auctores 399

Anthophysa 285 sqq, 343

Apprenticeship, L.’s 23

Arber, A. 168, 399

Archimedes 190

Arthrospira 110

Articles of Faith 73 sq

Astasia 164, 165

Aston, F. 47, 57, 90, 237

Astruc, J. 176, 399

Attestations, vide Testimonials

Aubrey, J. 186

Augustine, St 8

Autobiography 71

Azotobacter 198

Baan, J. van der 31, 399 |
Bacilli 133, 134, 178, 179, 245, 252 |
et alibi |

| Bacillus cola 198, 330 ; B. flexilis 236 ;

B. tuberculosis 374

Bacon, F. 183, 399

Bacon, R. 363, 364

Baen, G. 34

Baer, K. E. von 399

Baker, H. 282, 314, 318, 319, 320,
325, 326, 379, 381, 384, 400

Baker, W. E. Watson 326

Bakkenes, H. C. van 31, 400

Balantidium 229, 236

Banga, J. 31, 84, 92, 296, 385, 400

Baptism, L.’s 21

Barrow, J. 55, 400

Bassi, A. 382, 400

Baster, J. 381, 400

Baumann, E. D. 347, 400

Becking, L. B. 307, 308, 309, 327,
383, 400

‘ Bedellus immortalis ’ 33

Beelaerts, P. M. 347

Beer, H. de 313, 400

Beijerinck, M. W. 129, 178, 198,
199, 246, 353, 356, 391, 400, 424

| Bense, J. F. 12, 304, 400

Beresteijn, E. A. van 99
Bible, Dutch 4, 74, 305, 313, 400
Biddaff, J. 343

| Bidloo, G. 220, 400

Bile, globules in 217 sqq

Bill, L.’s 30

Biography 17 sqq

Birch, T. 12, 38, 40, 47, 48, 49, 57,
59; 11s, 172, 174, 176, 178; 183;
184, 185, 186, 194, 222, 231, 238,
400

INDEX

Birth, L.'s 19

Bjornstahl, J. J. 305, 400

Blanchard, E. 362, 401

Blanchard, R. 373, 401

Blankaart, S. 84, 90, 284, 401

Bleyswijck, A. van 83, 84, 88

Bleyswijck, D. van 24, 84, 401

Bleyswyk, H. van 263

Blois, A. de 349, 350

Blood-corpuscle, red 335 et alibi

Blyth, A. Wynter 32, 362, 401

Bodo 127, 132, 154

Boeke, J. 401

Boerhaave, H. 84, 270, 296, 334

otter, ac, 11, 19. 20, 23,. 24,28.
29, ol, AS, 92, 100, 102, 176,177,
301, 343, 344, 345, 360, 401

Bolnes (Vermeer), C. 35, 36

Bolsius, H. 382, 401

Bombinator 235

Bonnet, C. 401

Boogert, J. 176, 177

Borel, P. 141, 362, 364, 365, 401

Bory de St-Vincent, J. B. 381, 384,
402

Bosman, D. B. 306, 313, 402

Bostrém, A. 378, 402

Botrytis 382

Bouricwus, L.:G: N, 11, 19, 20; 21,
wea, 20,29, 30, 31, 34, 37, 99;
176, 177, 300; 30! , 302, 338, 340;
341, 353, 402, 424

Bourignon, A. 74

Boyer, J. 372, 402

Boyle, R. 39, 168, 357

Brachelius, A. 25, 402

Bray, W. 28, 406

Bredius, A. 36, 402

Brewerton, E. W. 90, 402

Bridges, J. H. 363, 402

Brocard, H. 372, 402

Brother, L.’s 18, 21

Brouncker, Viscount 182, 216, 358

Brown, R. 384, 402

Browne, T. 107, 402

Bruce, D. 356

Bruggencate, K. ten 313, 402

Bryan, M. 343, 402

Bitsenlin Oo. 221.1234 (9235... 263,
266, 298, 376, 379, 383, 402

Buffon, G. L. L. de 380

427

Bulloch, W. 78; 325, 370; 375, 377,
379, 402, 424

Bunyan, J. 72, 402

Buonanni, F. 304, 367, 371, 403

Burch, W. v. 176

Burial, L.’s 99

Burlet 54

Burnet, G. 12, 403

Bursana 164

Butterfield 116

Cabinet of microscopes, L.’s 95, 96,
97, 98, 99, 314 sqq

Camerling, J. 32

Candolle, A. De 53, 403

Cappelle, J. P. van 403

Cappelli, A. 313, 403

Carbone, D. 46, 359, 361, 390, 403

Carchesium 208, 211, 278, 285

Carswell, R. 220, 403

Carus, J. V. 403

Carutti, D. 364, 403

Castlemain, Earl of 40, 403

Catharina van Leeuwenhoek, vide
Sisters, L.’s

Cazeneuve, P. 372, 403

Celli, A. 369, 403

Cépedea, vide Opalina

Cercomonas 125, 126, 129

Cesi, F. 364

Chalk and clay 51

Chalmot, J. A. 403

Chamberlain, Sheriffs’ 31, 32

Chamberlayne, E. 270

Chamberlayne; Io 1775) 270; 271.
273,274, 275,216, 277, 278, 279;
281, 282, 283, 285, 286, 287, 288,
289, 291, 371, 403

Chantavoine, J. 36, 403

Chaos 377

Chapman, A. Chaston 363, 403

Chapman, J. 350

Charante, N. H. van 404

Charles I 19, 28

Charles II 14, 28, 184, 371

Chilodon 146, 164

| Chilomastix 224, 229, 234

Chironomus 205

Chlamydomonas 263, 264, 268, 298
Christensen, C. 376, 404
Chronological note vi

428

Chyle = Chyme 85, 284

Cicero 93, 94

Ciliary mechanism 292 sqq

Cinck, A. 80, 81, 82
Circulation-microscope 332 sq
Clove-water, animalcules in 155 sqq
Coat-of-arms, L.’s 305

Coccidia 219 sq

Cohn, F. 246, 356

Cole, F. J. 70, 184, 263, 347, 359, |
| Dispersal of animalcules by birds

404, 424

Coleps 263, 266

Colerus, J. 176, 404

Collot d’Escury 404

Colpidium 134, 135, 137, 138, 139,
140

Columella 369, 418

Comptoir, L.’s 114, 125

Conjugation of ciliates 200, 205, 206, |

213, 284

Contagium vivum 368 sqq

Cordes, H. 176, 177

Cordes, P. 176

Cornish, J. 47, 404

Corti, B. 380, 404

Cosmo III 390

Cotgrave, R. 313, 404

Cothurnia 278, 279, 280, 285

Creplin, F. C. H. 404

Crisp, F. 327, 403

Crithidia 221

Crommelin, C. A. 324, 326, 346, 404,
424

Cromwell, O. 14

Croone, W. 48, 186

Crose, J. C. dela 61 sq, 404

Cuculus 134

Cuvier, G. 404

Cyclidium 124, 125, 126, 127, 129,
133, 142, 154,955

Dale, J. H. van 313, 404
Daphma, vide Water-flea
Dark-ground illumination 331 sq
Darwin, C. 270
Daughter, L.’s,
Leeuwenhoek
Davaine, C. 404
Death, L.’s 92 sqq
Defoe, D. 318
Delfos, A. 352

vide Maria van

INDEX

Delft 24 sqq, & passim

Derham)’ Wi.) 152, 186, 222.7 389):
& vide Hooke (1726)

De Toni, G. B. 53, 404

Diatoms 278, 372

Dictionaries 312, 313

Dileptus 126, 165

Diploma of the Royal Society 48,
49, 87

Disney, A. N. 325, 327, 363, 405

270 ; by rain 163 ; by wind 267, 297
Ditch-water, animalcules in 165, 256

aed

Divini, E. 40, 41, 103

Dobell, C. 48, 217, 220, 221, 222, 224,
229, 246, 285, 356, 372, 381, 391,
405

Dods, M. 8

Drapery 23, 29, 30, 332

Draughtsmen, L.’s 147, 279, 342 sqq

Drebbel, C. 21, 363

Dryander, J. 405

Duckweed, animalcules on 276 sqq

Dudley, R., vide Leicester

Dujardin, F. 382, 405

Dutch editions 392 sqq

Dutens, L. 363, 405

Dwelling, L.’s 29, 125, 338 sqq

Edmundson, G. 12, 24, 405

Ehrenberg, C. G. 117, 278, 356, 372,
375, 381, 382, 385, 390, 405

Eichhorn, J. C. 381, 405

Eimeria 220

Elector Palatine 207, 216, 359

Elizabeth, Queen 14, 27

Elizabeth, Q. of Bohemia 28

Ellis, J. 380, 405

Elsholz, J. S. 116, 406

England, L.’s visit to 51

Erasmus 14

Esechielina leuwenhoekir 384

Euglena 111

Euplotes 142, 166

Evelyn, J. 12, 28, 39, 406

Explosion at Delft 28, 29, 55

Fabri, G. 364, 365
Fabritius, K. 28
Faille, B. de la 34

INDEX

Faith, L.’s scientific 73 sq

Family Tree 18

Fasciola 220

Father, L.’s 16, 18, 19, 20

Fellowship of Royal Society 47 sqq

Feyfer, F. M. G. de 326, 412

Film, the L. 285, 355, 424

Firmin, T. 47

Fleck, F. le Sueur 406

Fleck, J. M. 372, 406

Florio, J. 313, 406

Folkes, M. 102, 103 sq, 314, 316, 317,
318, 322, 325, 406

Fontenelle, B. de 53, 70, 71, 406

Foraminifera 51, 262, 263, 377

Foster, M. 406

Fracastoro, G. 370, 406

Frederik Hendrik 19

Frogs, animalcules in 230 sqq ;
vide Rana

Fulton, J. F. 61, 406

Funeral, L.’s 99

Fura 377

Gabb, G. H. 347

Gabler 84, 406

Gale, T. 47, 48, 49, 193, 196, 199

Galileo 363

Garden, G. 74

Garrison, F. H. 52, 368, 406

Geertruyt van Leeuwenhoek,
Sisters, L.’s

Genealogy 18

Generaal-wijkmeester 33

‘Gentleman in the Country’ 371,
399 ; vide Anonymus (1703)

George III 379

Geysbeek, P. G. W. 406

Giardia 224, 225, 229

Giesen, G. van der 102

Ginger-water, animalcules in 153 sqqg

Gleichen-Russworm, W. F. von 380,
406

Godfrey (Govert) of Lorraine 301

Godin 53, 406

Goedaert, J. 118

Goeree, J. 354 sq

Goiffon, J. B. 374 sq, 407

Goldfuss, G. A. 378, 407

Gordon, L. 176

vide

& |

429

Gordon, R. 176

| Gosch, C. C. A. 407

| Gosse, E. 43

| Govi, G. 363, 364, 407

| Graaf, R: de 39,40, 41, 42; 103, 357,

407
Grammont, vide Hamilton
Grassi, B. 382
Gray, S. 371, 407
Green, J. R. 78, 407
Gregory, D. 163, 407

eee N47 eS 16S 17279) See
186, 306, 357, 358, 367, 383, 387,
407

Grew, O. 168

Gribius, P. 93, 94, 95, 96, 97, 98, 345

_ Grober, J. 374, 407

Gronovius, L. T. 388, 407

Groot, C. H. de 62, 351, 352, 407

Gutter-water, animalcules in 165,
263 sqq

Haan, Bs 175,177

Haastert, I. van 11, 23, 31, 325, 407

Haaxman, P. A. 326, 328, 346, 407

Haaxman, Py j.eih 19) 20p 2023,
24. 27, 28, 30, 31,33) 53,004,090,
57, 70, 81, 93; 102, 115; 117; AS%
302, 305, 320, 321, 326, 335, 338,
339, 346, 347, 350, 355, 390, 408

Haaxman, S.A.(E. 328

Hadfield, R. 408

Haematococcus 263, 264, 265, 268,
269, 298

Haeser, H. 314, 408

Hairsbreadth 336 & alibi

Hake, T. G. 220, 221, 408

Halbertsma, H. 11, 20, 23, 49, 53,
54, 317, 408

Hall, H. C. van 382, 384, 408

Hallam, H. 385, 408

Haller, A. von 184, 408

Halliwell-Phillipps, J. O. 359, 388,
408

Halma, F. 312, 313, 408

Ham, J. [co-discoverer, with L.,
of spermatozoa], vide Halbertsma
(1862) & Muys

Hamilton, A. 12, 408

Hannot, S. 312, 313, 408

430

Harris, D. F. 100, 101, 409

Harris, J. 111, 371, 409

Harange, (P11, "53; 54) 320. 321.
322, 323, 324, 325, 326, 335, 338,
339, 340, 346, 350, 355, 356, 363,
364, 379, 390, 391, 409

Hartsoeker, C. 69

Hartsoeker, N. 53, 69 sg, 245, 409

Heijnsbroeck, J. 30

Heijnsbroeck, P. 30

Hein, P. 26

Hens, animalcules in 228

Henshaw, T. 186

d’Herelle, F. 356

Heugelenburg, M. 313, 409

Heusch, J.C) 47

Hexham, H. 312, 313, 409

Hill, A. 186

Hill, J. 376, 384, 409

Hill, T. G. 376, 409

Hirsch, A. 84, 92, 379, 385, 409

Hodenpijl, A. 176, 177

Hoefer, F. 409

Holmes, C. 351

Holmes, R. 33

Holt €. 371

Homer 94

Hoogvliet, A. 92

Hoogvliet, J. 90, 92, 93

Hooke, R. 43, 44, 47, 48, 49, 52,
173, 178, 182, 183, 184, 185, 186,
187, 192, 193, 194, 199, 200, 207,
221, 222, 238, 263, 308, 334, 358,
362, 364, 365, 371, 389, 409, 410

Hoole? 'S. ‘3; 90; 200; 207, 222, 231,
2371, 239, PAN, 241, 242, 247, 262.
263, 264, 266, 268, 325, 343, 350,
397, 410

Horse-fly, animalcules in 221

Hoskyns, J. 186

Houghton, J. 48

Houlatson, R. 349

House, L.’s, vide Dwelling

Howell, J. 12, 45, 307, 410

Hunt, H. 48

Huych van Leeuwenhoek, vide Uncle,
Es

Huygens, Christiaan 14, 43, 44, 50,
33, 54, 60, 70; 115; 116; 127, 128,
163 sqgq, 167, 172,177, 187; 389,
410; & vide Harting (1868)

INDEX

Huygens, Constantijn sen. 42, 43,
44, 50, 60, 115, 116, 117, 164, 167,
172, 186, 187, 192, 304, 333, 343,
347, 348, 359, 410 ; & vide Jorissen
& Worp

Huygens, Constantijn jun. 50, 60,
164

Hydra 280 sqq

Inch, L.’s 334

Incubation of cultures, first instance
of 269

‘ Infusoria ’ 377, 379

Inscriptions on L.’s tomb 100, 101

Intestinal Bacteria 222 sqq

Intestinal Protozoa 222 sq

Israéls, A. H. & Daniéls, C. E. 410

Jackson, B. Daydon 376, 410

Jacob van Leeuwenhoek, vide
Brother; L.’s

Jaeger, F. M. 21, 410

James I 43

James II 33

Jelgersma, T. 102

Jew, EE: netar22

Joblot, L3725410

Jones, W. H. S. 369, 411

Jongh, A. de, vide Junius

Jorissen, T. 411

Joubin, L. 382, 411

Jourdan, A. J. L. 384, 411

Junius, H. 24, 27, 411

Jurin, J. 88, 89, 90, 93, 94, 96, 97,
337, 411

Kaathoven, C. H. W. van 346, 347

Kaiser, L. 355, 411

Kent, W. Saville 114, 115,117, 235,
308, 326, 411

Kerkherdere, J. G. 82, 83, 223

Kerona 282, 285

Kihaan, C. 312, 313, 411

King, E. 371, 411

Kipling, R. 364

Kircher, A. 141, 162, 165 sqg, 370,
41]

Knickerbocker, W. S. 114, 411

Knipsheer, F. S. 93

INDEX

Koch, R. 348
Konarski, W. 116, 372, 411
Kruif, Paul de iii, 411, 423

Lacroze, de, vide Crose, de la

Lamblia 224

Lancisi, G. M. 369, 411

Landgrave of Hesse 60, 148

Lang, Leaf, & Myers 95

Language, L.’s 305 sqq

Last illness, L.’s 90, 91

“Last letter” to Roy. Soc. 87

Latin editions 394 sqq

Laue, M. 381, 411

Launois: P: E70, 362,411

Laurillard, E. 313, 400

Lauzun, P. 381, 411

Ledermiller, M. F. 379, 412

Leduc, S. 291, 412

Leersum, E. C. van 296, 326, 412

Leeuwen, C. van 21, 37, 412

Leeuwenhoekia 384

Leeuwenpoort 301

Leibniz, G. W. 46, 70, 71, 113, 324,
359, 360, 385, 390, 412

Leicester, Earl of 14, 27

Rely, P. 102

Lely, W. van der 102

Lemna 276

Lenses, discovery of 363; L.’s 319

ag7

Leptomonas 221

Leptothrix 246, 251, 252

Lesser, F. C. 375, 412

Letters, L.’s, vide Writings

Leuckart, R. 412

Levenhookia 384

Limnias 278

Linnaeus, C. 376 sqq, 412

Lint, J. G. de 346, 355, 412

Lipperhey, H. 363

Locke, J. 19, 186

Locy, W. A. 22, 32, 326, 347, 412

Loéffler, F. 238, 239, 246, 247, 366,
367, 370, 413

Loon, G. van 55, 80, 81, 82, 355, 413

Louse, eye of 121, 336 & alibi ;_ hair
of 337 & alibi

Louvain, medal from 79 sqq, 355

Lucaswe. V7 a6, 350; 413

Luke, St 425

431

“MA. CADy 375.435

McKerrow, R. B. 413

Maes, N. 19, 351, 353

Magliabechi, A. 46, 53, 179, 359

390, 397

Maigne d’Arnis, W. H. 313, 413

Malaria 180, 369

Malpighi, M. 168, 362, 383, 413

Man, C. de 353

Manuscripts, L.’s 388 sqq

Manzini, C. A. 40, 324, 413

Mapletoft, J. 186

Margaretha Bel van den Berch,
vide Mother, L.’s

Margriete van Leeuwenhoek, vide
Sisters, L.’s

Maria van Leeuwenhoek (L.’s daugh-
ter) 18, 28, 64, 69, 94, 95, 96, 97,
98, 99, 100, 102, 103, 240, 302, 305,
320, 361

Maria van Leeuwenhoek (L.’s sister),
vide Sisters

Marriages, L.’s 18, 28, 30, 31

Marten, B. 374, 413

Martin, B. 70, 413

Martin, T. H. 363, 413

Martinez, M. 312, 313, 413

Mary II 56, 104, 317

Matthew, St 74

Maty, P. H. 389, 413

Mayall, J. 324, 326, 327, 329, 413

Mayor, J. E. B. 413

Measurements, L.’s, vide Micrometry

Medal, the Leeuwenhoek 356; the
Louvain 79 sqq

Meerman, J. 35

Meester, W. 60

Meijer, L. 35, 114, 312, 313, 413

Melicerta 278, 279, 291, 293, 294

Memorabilia 16

Mensert, W. 364, 413

Mesmin, vide Anonymus (1679)

Mesnil, F. 53

Metcalf, M. M. 235, 413

Methods, L.’s 169 sqq, 187 sq, 200 sqq,

331 sq; & passim

Mey, Barbara de 16, 18, 28, 30

Mey, Elias de 28

Miall, L. C. 87, 263, 378, 414

Micrococci 245

Micrometry, L.’s 200 sqq, 333 sqq

432

Microscope, discovery of 363

‘Microscopes,’ L.’s 96, 97, 98, 103,
313 sqq

Microscopica 381

Miller, W. D. 245, 246, 414

Millet-seed 335 sq; & alibi

Minsheu, J. 312, 313, 414

Moes, E. W. 346, 352, 353, 414

‘ Moleculae vivae’ (Linnaeus) 377

Molhuysen, P. C. 326, 412

Molijn, Jacob 21, 22

Molijn, Jan 21

Molliére, H. 374, 414

Molyneux, T. 17, 56 sqq, 60, 62, 414

Molyneux, W. 56, 59 sq, 414

Monas 121, 122, 123, 124, 125, 126,
127, 142, 143, 271

Monpart 414

Moore, J. 186

Moray, R. 14; & vide Robertson

More, T. 14, 73, 414

Morre, G. 29, 30, 37, 101, 102, 305,

414

Morris, W. 7

Mortreux, E. 414

Mosquito-larvae 256

Mother, L.’s 16, 18, 20, 22

Motley, J. L. 12, 27, 414

Mountague, W. 25 sq, 414

Mouth, animalcules in the 236 sqq,

296

Miller, O. F. 285, 376 sq, 381, 414

Multiplication of animalcules 297 sq ;
& alibi

Municipal appointments, L.’s 31 sqq

Muré, J. B. A. 339

Muscae volitantes 90

Mussel-water, animalcules in 207 sqq

Muys, W. G. 337, 414

Naber, H. A. 21, 414

Nachet, A. 326, 327, 414

Nagler, K. 118, 119, 415

Name, L.’s 300 sqq

Narez, U. 82

Needham, T. 379, 380, 415

Neeltge van Leeuwenhoek, vide
Sisters, L.’s

New Church, Delft 21, 22, 25, 26,
28, 29, 35

Newton, I. 70, 237

INDEX

New York 33

Nicholas, E. 28
Nieuwenhuis, G. 54, 415
Noctiluca 381

| Nonionina 263

Noordenbos, T. U. 415
Nordenskiodld, E. 321, 415

Nosema 382

Nutmeg-water, animalcules in 159

Sqq
Nuttall, G. H. F. 48, 415
Nyander, J. C. 378, 415
Nyctotherus 233, 234, 235, 236

Objects before L.’s lenses 322 sqq

Obreen, F. D. O. 35, 36, 415

‘Observing person in the country’
(Anonymus, 1677) 373, 378, 399

Ockers, P. 34

Oecophora leeuwenhoekella 384

Old Church, Delft 22, 24, 26, 28,
29, 30,99 sq; & alibi

Oldenburg, H. 37, 38, 39, 40, 41,
AS (44 AG, AT, Si, 109) 111, Pha,
114) MS 116; 1172018, 119 et,

; 128, .129;.136, 139, 149, 167;

72, 7s, 182, 216,217, 238;

, 307, 331, 333, 342, 357, 358,

Oliver, F. W. 415
Oniscus 224

| Opalina 233, 234, 235, 236

Opuscula Selecta Neerlandicorum 415
Ornstein, M. 37, 53, 415
Osborne, D. 12, 45, 415

| Ostade, A. van 352

Oudemans, A. C. [acarologist] 384,
415

Oudemans, A. C.
312, S13, 413

Oxysoma 231

Oxytricha 149

Oxyuris 208, 231

Oyster-water, animalcules in 206,
207

(lexicographer]

Pagel 348 ; & vide Hirsch
Pandorina leuwenhoeku 384
Panicum, vide Millet-seed
Pansier, P. 364, 416
Paramecium 164, 210, 376

INDEX

Pars, A. 416

Pasteur, L. 199, 356, 374, 382, 416

Pediculus 336; & vide Louse

Pepper-water, animalcules in 131 sqq,
165, 166, 182, 183, 185, 187, 197,
200

Pepys, 5. 12, 25, 38, 129, 186, 416

Peter the Great 55

Petiver, J. 78

Petrie, A. 174, 175

Phacus 164

Philosophical Transactions 389; &
passim
Philips van Leeuwenhoek, vide

Father, L.'s
Phillips, L. B. 416
Pigeon, animalcules in a 228
Pijzel, E. D. 24, 309, 416
* Pissabed ’ 224
Plietzsch, E. 36, 416
Plintmer, Hi. G. 22, 23,33; 416
Pliny 95, 367, 384, 416
Poitevin, R. 176
Pollock, F. 113, 176, 416
Polystomella 263
Polytoma 297 sq
Pond-water, animalcules in 295 sqq
Poot, H. 101, 345, 416
Portraits of L. 346 sqq
Power, H. 141, 362, 364, 365, 416
Prescott, F. 252, 416
Pritze, F. 229, 236, 416
Pritzel, G. A. 388, 416
“ Protozoa ’ 378
Prowazek, S. von 236, 245, 416
Pseudospira 141; & vide Dobell
(1912)
Publications, L.’s 390 sqq
Pusey, E. B. 8

Rabus, P. 396, 416 ; letters to 396 sq

Radl, E. 385, 416

Rain-water, animalcules in 117 sqq,
205, 271

Raja 139

Rana esculenta 231, 233, 234, 235,
236; R. temporaria 231, 233, 234,
235

hays ee ee, Oly) SZ, 109; 112) 263;
264, 416

Record of the Royal Society 417

433

Redi, F. 196, 199, 364, 417

Réga, H. J. 82

Register van alle de Werken, vide
Anonymus (1695)

Regley, l Abbé 417

Rémignard, H. 373, 417

Rhede, Baron van 206, 262

Rhizopoda 262

Richardson, 8, W: 22: 31) 322.33:
53, 304, 417

Riemsdijk, B. W. F. van 346, 417

River-water, animalcules in 128

Rix, FL 38,417

Robertson, A. 417

Robin, C. 246, 417

Robinson, H. W. 237

Rosel von Rosenhof, A. J. 282, 378,
417

Rogers) aj oR. 1417

Rooijen, A. J. Servaas van 80, 82,
103, 390, 417

Roos, J. C. 378, 418

Rosenheim, O. 418

Rotalia 263

Rotermund, H. W. 418

Rotifers 110, 121, 263 sqq, 278 sqq,
291, 292, 293, 294, 297, 384

Roukema, R. 385, 418

Roy, J. le 177

Royal Society 37 ; & passim

Royal Society MSS. 356 sqq, 388 sqq ;
& passim

Ruijsch, F. 84

Ruisdael, J. van 129

Ruyter, M. de 39

Sabrazés, J. 326, 362, 418

Sachs, J. 382, 383, 418

Sale-Catalogue of L.’s microscopes
320 sq

Saliva, animalcules in 238 sqq

Salting, G. 351

Salvino d’Armato 364

Sandgrains 334 sq; & passim

Sarcina 246

Saussure, H. B. de 380, 418

Scheltema, P. 84, 418

Schevelinge = Scheveningen 129

Schierbeek, Ay. 120) 21) 2323)
27, 29, 30, 31, 34, 37, 99, 100, 281,
300, 302, 341, 418, 424

434

Schill, J. F. 109, 418

Schooling, L.’s 23

Schrank, F. von Paula 384

Schultsz, J. C. 340

Scriptores ret rusticae 418

Scriverius, P. 24, 418

Seals, L.’s 359 sqq

Sea-water, animalcules in 129 sqq

Sections, histological 333

Selenomonas 245, 246

Selle, M. 425

Senebier, J. 380, 418

Seters, W. Ho van 115,116, 333,
346, 355, 359, 387, 390, 418, 424

Sewel, W. 129, 263, 312, 313, 418

Sherborn, C. D. 384, 419

Shop, L.’s 29, 338 sqq

Shrimp’s stomach, shell in 262

Singer, C. 246, 247, 363, 365, 366,
367, 368, 370, 374, 419

Singer, D. 370, 419

Sinia, R. 117, 419

Sisters, L.’s 18, 21, 22

Slabber, M. 381, 419

Slare, F. 230, 373, 419

Sloane, H. 78, 79, 256, 389

Smith, A. 350

Snelleman, J. F. 115, 390, 419

Snijders, E. P. 149, 424

Soil, animalcules in 297

Sons, L.’s 18, 28

Soutendam, J. 19, 20, 31, 48, 102,
338, 339, 419

Spallanzani, L. 199, 260, 304, 379,
380, 419

Sparshall, J. 381

Spermatozoa 6, 104, 121, 184, 221,
228, 230, 296, 377, 378

Spermine, vide Rosenheim

Sphaerella, vide Haematococcus

Spina, A. de 364

Spinoza, B. de 19, 113, 176, 308, 419

Spirillum 143, 144, 179, 214, 245

‘ Spirillum’ sputigenum 245

* Spirochaeta buccalis’ 241, 246

Spirochaetes 225, 229, 241, 246,
250, Zan,

Spirogyra 110

Spirulina 110, 380

Spoors, Surveyor 35

Sporozoa 220

INDEX

Sprat, T. 12, 37, 419

Statius, 94, 96

Stein, F. von 229, 419

Stelluti, F. 364, 365, 419

Stepfather, L.’s, vide Molijn, Jacob

Stirling, W. 419

Storr-Best, Ll. 369, 419

Strick, Jeol, .32

Strong, R. P. 229, 420

Stuart, A. 78, 79

Sturm, J.-C. 372, 420

Stylonychia 126

Surveyor, L. qualifies as 34, 354

Swalmius, Cornelia 16, 18, 31, 52, 240

Swammerdam, J. 24, 39, 74, 111,
117, 118, 130, 420

Sydenham, T. 186

Sylvius 39

Tabanus 221

Tabellaria 372

Tanner, J. R. 420

Targioni-Tozzetti, G. 46, 179, 360,
390, 397, 420

Teeth, animalcules on the 238 sqq

Temple, W. 12, 40, 45, 129, 420

Testimonials 172, 173, 174 sqq

Thompson, D’Arcy W. iii, 94, 190,
423

Thomson, T. 12, 420

Thorpe, E. 420

Thread-bacteria 135, 141, 165

Tomb, L.’s 100, 101, 102

Tongue, animalcules from the 254

Totton, A..K 337

Town Hall, Delft 26

‘ Trees,’ metallic 291

Trembley, A. 281, 282, 380, 420

Trepomonas 210

Trevelyan, G. M. 420

Treviranus, G. R. 420

Trichodina 282, 285

Trichomastix |=Eutrichomastix} 231,
234, 236

Trichomonas 224, 229, 231, 234, 236,
246, 247

Tromp, M. 26

Trustee (for Vermeer) 35 sq

Tschirnhausen, E. W. von 338

Tyndale, W. 308

Tyndall, J. 199, 420

INDEX 435

Uffenbach, Z. C. von 56, 63 sqq, 77,
325, 420

Uncle, L.’s 18, 23, 300

“ Unpublished letters ’ (1-27) 356 sqq

Uttenbroek 360

Vallisneri, A. 303, 375, 420, 421 |

Vandevelde, A. J. J. 43, 109, 115, |
116, 117, 173, 256, 263, 270, 275, |
285, 333, 356, 359, 362, 390, 421 |

Vanellus 134

Van Heurck, H. 326

Vanzype, G. 36, 421

Varro 369, 418, 419 |

Veldman, H. S. 347, 421

Verkolje, J. 49, 72, 325, 340, 343,
345, 346 sqq, 350, 351, 353, 354,
361

Vermeer, J. 19, 25, 28, 35, 36, 125,
345, 353 sq

‘Vessels ’ in animalcules 189 sqq

Vinegar, animalcules in 150 sqq

Vinegar-eel 141, 150 sqq, 179, 225, |
243, 325

Vine-sap, animalcules in 193sqq_ |

Virgil 80

Virlin, Maria 28

Volvox 256 sqq, 377, 380, 384

Vorticella & Vorticellidae 118 sq,
133, 136, 148, 156 sg, 164, 208, |
2/7 sag, 283, 285, 291, 292, 293,
294, 295, 377, 381

Vries, J. de 103

Waard, C. de 363, 421
Waller, R. 47, 348, 421
Ward, N. 12, 421

Water-flea 111, 118, 130, 273

Weights, L.’s 337 sq

Weld, C; R. 12, 37,39, 96,99, 237,
421

Well-water, animalcules in 128

Wendel, A. J. 347

Wenyon, C. M. 246, 247, 421

Werff, J. van der 80

Wheatley, H. B. 304, 416

Whewell, W. 422

White, A. H. 326, 423

| Wild Boar, College of the 82
| Wildeman, M. G. 29, 101, 422

Wilkins, J. 38, 422

Will, L.’s 103

William I (the Silent) 25, 26
William III 25, 26, 104, 317
Williams-Ellis, A. 52, 347, 422
Williamson, J. 49

Willnau, C. 379, 422

Wilt, T. van der 93, 343 sqq
Wilt, W. van der 344 sq
Wine-gauger, L. appointed 37

| Wives, L.’s; wide Mey, B. de, ©

Swalmius, C.

| Wolf, A. 422

Woodruff, L. L. 376, 422

| Worp, J. A. 43, 422

Wren, C. 19, 186, 231
Wrisberg, H. A. 303, 379, 422
Writings, L.’s 44sqg, 388 sqq

Zacharias Janssen 363
Zahn, J. 422

Zoelen, H. van 359
Zoogloea 160

Zwalmius, vide Swalmius

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