History of biology

Is.

THESE SPLENDID HANDBOOKS BELONG TO
AN AGE Off WONDERS."— BIRMINGHAM GAZETTE.

The Story of the Sciences

ALL ABOUT

BIOLOGY

BY

L. C. MIALL. D.Sc., F.R.S.,

ierly Professor' of Biology, Leeds University, 1876-1907
Fullerian Professor, Eoyal Institute, 1904-5

160 pp., with Pictorial Illustrations

(This work may also be had bound in cloth, price 2s. net}

LONDON: WATTS & CO.

m

.

BIOLOGY LIBRARY

KARL ERNST VON BAER

(in old age), from the picture by Hagen-Schwarz.

( By Permission of t/te Berlin Photographic Company, 133 New Bond Street,
London, W,~)

HISTORY OF

BIOLOGY

BY

L. C.HVJIALL, D.Sc., F.R.S.,

FORMERLY PROFESSOR OF BIOLOGY IN THE UNIVERSITY OF LEEDS

[ISSUED FOR THE RATIONALIST PRESS ASSOCIATION, LIMITED]

LONDON :
WATTS & CO.,

17 JOHNSON'S COURT, FLEET STREET, E.G.
1911

H//

LIBRARY
6

•,*

CONTENTS

INTRODUCTION i

Biology of the ancients. Extinction of scientific
inquiry. Revival of knowledge.

PERIOD 1(1530-1660) - - - - - 7

Characteristics of the period. The revival of
botany. The revival of zoology. Early notions of
system. The first English naturalists. The rise of
experimental physiology. The natural history of
distant lands (sixteenth century and earlier). Agri-
culture, horticulture, and silk-culture in the sixteenth
century.

PERIOD II (1661-1740) 28

Characteristics of the period. The minute anatomists.
Early notions about the nature of fossils. Compara-
tive anatomy ; the study of biological types. Adapta-
tions of plants and animals ; natural theology.
Spontaneous generation. The natural history of
John Ray. The scale of nature. The sexes of
flowering plants.

PERIOD 111(1741-1789) - - . . - 49

Characteristics of the period. Systems of flowering
plants ; Linnaeus and the Jussieus. Reaumur and
the History of Insects. The budding-out of new
animals (Hydra) ; another form of propagation with-
out mating (aphids). The historical or comparative
method ; Montesquieu and BufFon. Amateur students
of living animals. Intelligence and instinct in the
lower animals. The food of green plants. The
metamorphoses of plants. Early notions about the
lower plants.

Mv 3655

vi CONTENTS

PERIOD IV (1790-1858) - 89

Characteristics of the period. Sprengel and the
fertilisation of flowers. Cuvier and the rise of
palaeontology. Chamisso on the alternation of
generations in Salpa. Baer and the development of
animals. The cell-theory. The scientific investiga-
tion of the hig-her cryptogams. The enrichment of
English gardens. Humboldt as a traveller and a
biologist. Premonitions of a biological theory of
evolution.

PERIOD V (1859 AND LATER) - - 124

Darwin on the Origin of Species. Pasteur's experi-
mental study of microbes.

CHRONOLOGICAL TABLE - - - - - 141

THE SUB-DIVISIONS OF BIOLOGY - - - 146

BIBLIOGRAPHY - - - - - 147

INDEX- - - - - 149

LIST OF ILLUSTRATIONS

PAGE

KARL ERNST VON BAER .... Frontispiece
FIGURE FROM FUCKS' " HISTORIA STIRPIU-M " 8

LEONHARD FUCHS • . • - - 10

COMPARATIVE FIGURES OF SKELETONS OF MAN AND
BIRD, FROM BELON'S BOOK OF BIRDS - - - 14, 15

MARCELLO MALPIGHI - - - - 31

ANTONY VAN LEEUWENHOEK - - - -33

JOHN RAY ... 42

CAROLUS LINNAEUS ------ 53

GEORGES Louis LECLERC, COMTE DE BUFFON - -65

GEORGES CUVIER ------ 99

*,»

INTRODUCTION

FOUR HUNDRED years ago, say in the year 1500, Biology,
the science of life, was represented chiefly by a slight
and inaccurate natural history of plants and animals.
Botany attracted more students than any other branch,
because it was recognised as a necessary aid to medical
practice. The zoology of the time, extracted from
ancient books, was most valued as a source from
which preachers and moralists might draw impressive
emblems. Anatomy and physiology were taught out of
Galen to the more learned of physicians and surgeons.
Some meagre notices of the plants and animals of
foreign countries, mingled with many childish fables,
eked out the scanty treatises of European natural
history. It was not yet generally admitted that fossil
bones, teeth, and shells were the remains of extinct
animals.

It is the purpose of the following chapters to show
how this insignificant body of information expanded
into the biology of the twentieth century ; how it
became enriched by a multitude of new facts, strength-
ened by new methods and animated by new ideas.

The Biology of the Ancients.

Long before the year 1500 there had been a short-
lived science of biology, and it is necessary to explain
how it arose and how it became quenched. Ancient
books and the languages in which they are written
teach us that in very remote times men attended to the

i

INTRODUCTION

of plants a^d the habits of animals, gave names to
familiar species, and recognised that while human life
4i&s mac:i in common with the life of animals, it has
something in common with the life of plants. Abundant
traces of an interest in living things are to be found in
the oldest records of India, Palestine, and Egypt. Still
more interesting, at least to the inhabitants of Western
Europe, is the biology of the ancient Greeks. The
Greeks were an open-air people, dwelling in a singularly
varied country nowhere far removed from the moun-
tains or the sea. Intellectually they were distinguished
by curiosity, imagination, and a strong taste for
reasoning. Hence it is not to be wondered at that
natural knowledge should have been widely diffused
among them, nor that some of them should have
excelled in science. Besides all the rest, the Greeks
were a literary people, who have left behind them a
copious record of their thoughts and experience. Greek
science, and Greek biology in particular, are therefore
of peculiar interest and value.

Greek naturalists in or before the age of Alexander
the Great had collected and methodised the lore of
the farmer, gardener, hunter, fisherman, herb-gatherer,
and physician ; the extant writings of Aristotle and
Theophrastus give us some notion of what had been
•discovered down to that time.

Aristotle shows a wide knowledge of animals. He
dwells upon peculiar instincts, such as the migration of
birds, the nest-building of the fish Phycis, the capture of
prey by the fish Lophius, the protective discharge of
ink by Sepia, and the economy of the hive-bee. He is
fond of combining many particular facts into general
statements like these : No animal which has wings is
without legs ; animals with paired horns have cloven

THE BIOLOGY OF THE ANCIENTS 3

feet and a complex, ruminating stomach, and lack the
upper incisor teeth ; hollow horns, supported by bony
horn-cores, are not shed, but solid horns are shed every
year ; birds which are armed with spurs are never
armed with lacerating- claws ; insects which bear a sting
in the head are always two-winged, but insects which
bear their sting behind are four-winged. He traces
analogies between things which are superficially unlike,
such as plants and animals — the mouth of the animal
and the root of the plant. The systematic naturalist is
prone to attend chiefly to the differences between
species ; Aristotle is equally interested in their resem-
blances. The systematic naturalist arranges his
descriptions under species, Aristotle under organs or
functions; he is the first of the comparative anatomists.
His conception of biology (the word but not the thing
is modern) embraces both animals and plants, ana-
tomy, physiology, and system. That he possessed a
zoological system whose primary divisions were nearly
as good as those of Linnaeus is clear from the names
and distinctions which he employs ; but no formal
system is set forth in his extant writings. His treatise
on plants has unfortunately been lost.

Aristotle, like all the Greeks, was unpractised in
experiment. It had not yet been discovered that an
experiment may quickly and certainly decide questions
which might be argued at great length without result,
nor that an experiment devised to answer one question
may suggest others possibly more important than the
first. Deliberate scientific experiments are so rare
among the Greeks that we can hardly point to more
than two — those on refraction of light, commonly
attributed to Ptolemy, and those by which Pythagoras
is supposed to have ascertained the numerical relations

INTRODUCTION

of the musical scale. Aristotle was the last great man
of science who lived and taught in Greece. His
writings disappeared from view for many centuries,
and when they were recovered they were not so much
examined and corrected as idolised.

Greece lost her liberty at Chaeronea, and with liberty
her fairest hopes of continued intellectual development.
Nevertheless, during a great part of a thousand years
the Greek and Semitic school of Alexandria cultivated
the sciences with diligence and success. We must say
nothing here about the geometry, astronomy, optics, or
geography there taught, but merely note that Hero-
philus and Erasistratus, unimpeded by that repugnance
to mutilation of the human body which had been insur-
mountable at Athens, made notable advances in anatomy
and physiology. From this time a fair knowledge of
the bodily structure of man, decidedly superior to that
which Aristotle had possessed, was at the command of
every educated biologist.

The genius of Rome applied itself to purposes remote
from science. The example of Alexandria had its
influence, however, upon some inhabitants of the
Roman Empire. Galen of Pergamum in Asia Minor
prosecuted the study of human anatomy. His know-
ledge of the parts which can be investigated by simple
dissection was extensive, but he was unpractised in
experimental physiology. Hence his teaching, though
full with respect to the skeleton, the chief viscera, and
the parts of the brain, was faulty with respect to the
flow of the blood through the heart and body. Ages
after his death the immense reputation of Galen, like
that of Aristotle, was used with great effect to discredit
more searching inquiries. Under the Roman Empire
also flourished Dioscorides, who wrote on the plants used

EXTINCTION OF SCIENTIFIC INQUIRY 5

in medicine, and the elder Pliny, who compiled avast,
but wholly uncritical, encyclopaedia of natural history.

We see from these facts how ancient nations, inhabit-
ing" the Mediterranean basin and largely guided by
Greek intelligence, had not only striven to systematise
that knowledge of plants and animals which every
energetic and observant race is sure to possess, but
had with still more determination laboured to create a
science of human anatomy which should be serviceable
to the art of medicine. The effort was renewed time
after time during five or six centuries, but was at last
crushed under the conquests of a long succession of
foreign powers — Macedonians, Romans, Mohammedan
Arabs, and northern barbarians — each more hostile to
knowledge than its predecessors.

Extinction of Scientific Inquiry.

The decline and fall of the Roman Empire brought
with it the temporary extinction of civilisation in a
great part of Western Europe. Science was during
some centuries taught, if taught at all, out of little
manuals compiled from ancient authors. Geometry and
astronomy were supplanted by astrology and magic ;
medicine was rarely practised except by Jews and the
inmates of religious houses. Literature and the fine
arts died out almost everywhere.

No doubt the practical knowledge of the farmer and
gardener, as well as the lore of the country-side, was
handed down from father to son during all the ages of
darkness, but the natural knowledge transmitted by
books suffered almost complete decay. The teaching
ascribed to Physiologus is a sufficient proof of this
statement. Physiologus is the name given in many
languages during a thousand years to the reputed

INTRODUCTION

author of popular treatises of zoology, which are also
called Bestiaries, or books of beasts. Here it was told
how the lion sleeps with open eyes, how the crocodile
weeps when it has eaten a man, how the elephant has
but one joint in its leg and cannot lie down, how the
pelican brings her young- back to life by sprinkling
them with her own blood. The emblems of the
Bestiaries supplied ornaments to mediaeval sermons ;
as late as Shakespeare's day poetry drew from them no
small part of her imagery ; they were carved on the
benches, stalls, porches, and gargoyles of the churches.

In the last years of the tenth century A.D. faint signs
of revival appeared, which became distinct in another
hundred years. From that day to our own the progress
has been continuous.

Revival of Knowledge.

By the thirteenth century the rate of progress had
become rapid. To this age are ascribed the introduc-
tion of the mariner's compass, gunpowder, reading
glasses, the Arabic numerals, and decimal arithmetic.
In the fourteenth century trade with the East revived ;
Central Asia and even the Far East were visited by
Europeans ; universities were multiplied ; the revival
of learning, painting, and sculpture was accomplished
in Italy. Engraving on wood or copper and printing
from moveable types date from the fifteenth century.
The last decade of this century is often regarded as the
close of the Middle Ages ; it really marks, not the
beginning, but only an extraordinary acceleration, of
the new progressive movement, which set in long
before. To the years between 1490 and 1550 belong
the great geographical discoveries of the Spaniards in
the West and of the Portuguese in the East, as well
as the Reformation and the revival of science.

PERIOD I.

1530-1660

Characteristics of the Period.

THIS is the time of the revival of science ; the revival
of learning had set in about two centuries earlier.
Europe was now repeatedly devastated by religious wars-
(the revolt of the Netherlands, the wars of the League
in France, the Thirty Years' war, the civil war in
England). Learning was still mainly classical and
scholastic ; nearly every writer whom we shall have
occasion to name had been educated at a university,
and was able to read and write Latin. Two great
extensions of knowledge helped to widen the thoughts
of men. It became known for the first time that our
planet is an insignificant member of a great solar
system, and that Christendom is both in extent and
population but a small fraction of the habitable globe.

The Revival of Botany.

Botany was among the first of the sciences to revive.
Its comparatively early start was due to close associa-
tion with the lucrative profession of medicine. Medicine
itself was slow to shake off the unscientific tradition of
the Middle Ages, and its backwardness favoured, as it
happened, the progress of botany. In the sixteenth
century the physician was above all things the pre-
scriber of drugs, and since nine-tenths of the drugs
were got from plants, botanical knowledge was reckoned
as one of his chief qualifications. All physicians

7

FIGURE OF SOLOMON'S SEAL.

From Fuchs* Historia Stirpium, 1542. The original occupies a folio page.

PERIOD I.

professed to be botanists, and every botanist was thought
fit to practise medicine.

Three Germans, who were at once botanists and
physicians — Brunfels, Bock, and Fuchs — led the way
by publishing- herbals, in which the plants of Germany
were described and figured from nature. Their first
editions appeared in the years 1530, 1539, and 1542.
Illustrated herbals were then no novelty, but whereas
they had hitherto supplied figures which had been
copied time after time until they had often ceased to be
recognisable, Brunfels set a pattern of better things by
producing what he called " herbarum vivae eicones,"
life-like figures of the plants. Each of the three new
herbals contained hundreds of large woodcuts. Those
engraved for Fuchs are probably of higher artistic
quality than any that have appeared since. Each plant,
drawn in clear outline without shading, fills a folio
page, upon which the text is not allowed to encroach.
The botanist will, however, remark that enlarged
figures are hardly ever given, so that minute flowers
show as mere dots, and that the details of the foliage
are not so scrupulously delineated as in modern figures.
The text of Brunfels and Fuchs is of little interest,
being largely occupied with traditional pharmacy.
Bock, whose figures are inferior to those of Brunfels
and Fuchs, makes up for this deficiency by his graphic
and sometimes amusing descriptions. He delights in
natural contrivances, such as the hooks on the twining
stem of the hop, or the elastic membrane which throws
out the seeds of wood-sorrel. Brunfels has no intelli-
gible sequence of species ; Fuchs abandons the attempt
to discover a natural succession, and adopts the alpha-
betical order ; Bock aims at bringing together plants
which show mutual affinity (" Gewachs einander ver-

LEONHARD FUCHS.

From his Historia Stirpium, 1742.

THE REVIVAL OF BOTANY n

wandt"), though such natural groups as he recognises
are neither named nor defined.

These three German herbals really deserve to be
called scientific. To figure the plants of Germany from
the life, to exclude such as existed only in books, and
to strive after a natural grouping, was a first step
towards a fruitful knowledge of plant-life. It is worth
while to dwell for a moment upon the place where these
herbals were produced. Along the Rhine civilisation
and industry had for many years flourished together.
Here and in the country to the east of the great river
had sprung up that powerful union of seventy cities
known in the thirteenth century as the Confederation
of the Rhine ; four universities, three of them on the
banks of the Rhine, had been founded ; here printing
and wood-engraving had established themselves in
their infancy ; here, too, the Reformation found many
early supporters. There were historical, economic, and
moral reasons why the first printed books- on natural
history, illustrated by wood-cuts drawn from the life,
should have been produced in the Rhineland, and why
all their authors should have been Protestants. Nearly
every sixteenth-century botanist held the same faith.

The success of the first German herbalists brought a
crowd of botanists into the field, among whom were
several whose names are still remembered with honour.
Gesner of Zurich made elaborate studies for a great
history of plants, which he did not live to complete.
It was he who first pointed out that the flower and
fruit give the best indications of the natural relation-
ships of plants, and his many beautiful enlarged
drawings set an example which has done much for
scientific botany. Botanists began to understand what
natural grouping means, and to recognise that truly

B 2

12 PERIOD I.

natural groups are not to be invented, but discovered.
The almost accidental succession adopted by Brunfels,
the alphabetical succession of Fuchs, the division
according- to uses (kitchen-herbs, coronary or garland-
flowers, etc.), and the logical, but too formal, method
of Cesalpini, in which, as in modern classification,
much use was made of the divisions in the ovary —
all these were left behind. L'Obel separated, uncon-
sciously and imperfectly, the Monocotyledons from the
Dicotyledons, recognised several easily distinguished
families of flowering- plants (grasses, umbellifers,
labiates, etc.), and framed the first synoptic tables of

genera.

The Revival of Zoology.

While the physicians of the Rhineland were describing
and figuring their native plants, the study of animals
began to revive. Two very different methods of work
were tried by the zoologists of the sixteenth century.
One set of men, who may be called the Encyclopaedic
Naturalists, were convinced that books, and especially
the books of the ancients, constituted the chief source of
information concerning animals and most other things.
They extracted whatever they could from Aristotle,
^Elian, and Pliny, adding- all that was to be learned
from the narratives of recent travellers, or from the
collectors of skins and shells. The books on which
they chiefly depended, being- for the most part written
by men who had not grappled with practical natural
history and its problems, were unfortunately alto-
gether inadequate. Many of the statements brought
together by the encyclopaedic naturalists were ill-
attested ; some were even ridiculously improbable. If
inferences from the facts were attempted — and this was
rare — they were more often propositions of morality or

EARLY NOTIONS OF SYSTEM 13

natural theology than the pregnant thoughts which
suggest new inquiries. Hence the encyclopaedic plan,
even when pursued by men of knowledge and capacity,
such as Gesner and Aldrovandi, yielded no results pro-
portional to the labour bestowed upon it ; the true path
of biological progress had been missed. Naturalists
of another school described and figured the animals of
their own country, or at least animals which they had
closely studied. Rondelet described from personal
observation the fishes of the Mediterranean ; Belon
described the fishes and birds that he had met with in
France and the Levant. His Book of Birds (1555) is a
folio volume in which some two hundred species are
described and figured. The " naturel " (natural history
of the species) contains many curious observations.
Perhaps the best things in the book are two figures
placed opposite one another and lettered in corre-
spondence ; one shows the skeleton of a bird, the other
that of a man. The example of Rondelet and Belon
was followed by other zoological monographers, who
did more for zoology than all the learning of the ency-
clopaedists.

Early Notions of System.

Simple-minded people, who do not feel the need of
precision in matters of natural history, have in all
ages divided animals into four-footed beasts which walk
on the earth, birds which fly, fishes which swim, and
perhaps reptiles which creep. This is the classification
found in the Babylonian and Hebrew narratives of the
great flood. Plants they naturally divide into trees and
herbs. It was not very long, however, before close
observers became discontented with so simple a
grouping. They discovered that the bat is no bird,
though it flies; that the whale is no fish, though it

AB

BIRD'S SKELETON.

For comparison with human skeleton (opposite), lettered to show the answerable
bones. From Belon's Book of Birds, 1555.

HUMAN SKELETON.

For comparison with bird's skeleton (opposite), lettered to show the answerable
bones. From Belon's Book of Birds, 1555.

16 PERIOD I.

swims ; that the snake comes nearer in all essentials to
the four-footed lizard, and even to the beast of the field,
than to the creeping earthworm. At a much later time
they discovered that pod-bearing or rose-like herbs
may resemble pod-bearing or rose-like trees more
closely than all trees resemble each other. Moreover,
a multitude of animals became known which cannot be
classed as either beasts, birds, fishes, or reptiles, and a
multitude of plants which cannot be classed as either
trees or herbs.

Aristotle found himself obliged to rectify the tra-
ditional classification of animals in order to remove
gross anomalies. When learning decayed the traditional
classification came back. Thus the Ortus Sanitatis
(first published in 1475, and often reprinted) adopts
the division into (i) animals and things which creep
on the earth ; (2) birds and things which fly ; (3)
fishes and things which swim. No consistent
primary division of plants was proposed by Greek or
Roman, nor by anyone else until the seventeenth
century A.D.

This conflict of systems should have raised questions
concerning the nature of classification and the relative
value of characters. Some of the most striking resem-
blances found among animals and plants are only
superficial ; others, though far less obvious, are funda-
mental. Whence this difference? Why should scientific
zoology make so little of the place of abode and the
mode of locomotion ; so much of the mode of
reproduction and the nature of the skeleton ? The
answers were vague, and even the questions were rare
and indistinct. But a metaphorical term came into
use which was henceforth more and more definitely
associated with fundamental, as distinguished from

EARLY NOTIONS OF SYSTEM

adaptive, likeness. Such likeness was called affinity^
though no attempt was made to explain in what sense
the term was to be understood. As late as the year
1835 one of the first botanists in Europe (Elias Fries)
could say no more about affinity between species than
that it was quoddam supernaturale, a supernatural
property.

A tolerable outline of a classification of animals was
attained much earlier than a tolerable classification of
plants. The characters available for the classification of
plants are, to begin with, less obvious than those which
the zoologist can employ. Moreover, the botanists
were restricted to a narrower view of their subject.
Zoologists, though they were expected to bestow
the best part of their time upon vertebrates, were
encouraged to study all animals more or less. Bota-
nists, on the other hand, were practically obliged to
concentrate their attention upon the classification of the
flowering plants. The physician, herb-collector, and
gardener cared nothing about any plants except such
as bear flowers and fruit ; but of these they expected
full descriptions, and were clamorous for a system
which would enable even a tyro to make out every
species with certainty and ease. The task set before
the botanist was comparable in respect of difficulty
with the construction of a detailed and completely
satisfactory classification of birds, which zoology has
never yet been able to produce, while for the sake of
this long-unattainable object almost everything else in
botany was neglected.

The First English Naturalists.
During the greater part of three centuries (1300 to

1 Aristotle, Cesalpini, Gesner, and Ray are among the writers
who use this word or some synonym.

i8 PERIOD I.

1600), while the revival of learning1 and science was
proceeding actively in Italy, France, Switzerland, and
the Rhineland, England lagged behind. Humanist
studies were indeed pursued with eminent success in
the England of Sir Thomas More, but there was little
else for national pride to dwell upon. The re-opening
of ancient literature, the outpouring of printed books,
the Reformation, the new mathematics and astronomy,
the new botany and zoology, were mainly the work
of foreigners. Before the seventeenth century no
Englishman was recognised as the founder of a scientific
school.

Passing over Edward Wotton (1492-1555), who
recast the zoology of Aristotle with very little effect
upon the progress of biology, we may head the list of
English naturalists with the name of William Turner
(d. 1568), who wrote on the plants and birds of Britain.
Turner was a Reformed preacher, who had been the
college friend of Ridley and Latimer. Being banished
for preaching without licence, he studied medicine and
botany in Italy, at Basle and at Cologne. Under Edward
VI. he returned to England and was made Dean of
Wells, fled again to the Continent on Mary's accession,
was re-instated by Elizabeth, was suspended for non-
conformity, and died not long after. Turner's herbal
(1551-63) cannot be said to have done much for English
botany. The arrangement is alphabetical, the pro-
perties and virtues of the plants are described out of
ancient authors, and most of the figures are borrowed.
Still, it was something to have the common plants of
England examined by a man who had studied under
Luke Ghini, had botanised along the Rhine, and was
the pupil, friend, and correspondent of Conrad Gesner,
the most learned naturalist in Europe. Turner's History

THE FIRST ENGLISH NATURALISTS 19

of Birds (Htstoria Avium) was published in Latin at
Cologne in I544,1 and is therefore earlier than Belon's
book of birds. The history contains here and there
among1 passages culled from the ancients a sprightly
description of the feeding or nest-building of some
English bird, and furnishes evidence of the breeding
in our islands of birds which, like the crane, have long
been known to us only as rare visitants. Of the kite
Turner says that in the cities of England it used to
snatch the meat out of the hands of children. In his
day the osprey was better known to Englishmen than
they liked, for it emptied their fishponds ; anglers
used to mix their bait with its fat. Turner shows
not a little of that spirit of close observation which
in a later and more tranquil age shone forth in Gilbert
White.

Dr. John Caius (the name is supposed to be a
Latinised form of Kay), the second founder of a great
Cambridge college, was physician in succession to
Edward VI., Mary, and Elizabeth ; in his youth he had
studied under Vesalius at Padua. Like Turner he was
a friend and correspondent of Gesner, for whom he
wrote an account of the dogs of Britain (De Canibus
Britannicis, printed in Latin in 1570), which attempts
to classify all the breeds, and to give some account of
the uses to which each was put. The list contains no
bull-dog, pointer, or modern retriever. There is a
water-spaniel, however, and dogs had already been
trained to retrieve game. The turnspit, which was not
a distinct breed (Caius calls it a mongrel), has long been
superseded. Curious antiquarian information, such as
mention of the weapons formerly used by sportsmen,

1 It has now been made accessible to all readers by the reprint
and translation of Mr. A. H. Evans.

20 PERIOD I.

and obsolete names of dogs, reward the reader of this
short tract.

Thomas Moufet wrote (for Gesner again) a book on
insects, which incorporated the notes of Penny and
Wotton. None of the three lived to see the printed
book, which was at last put forth by Sir Thomas
Mayerne in 1634. It is uncritical, confused, and illus-
trated by the rudest possible woodcuts.

John Gerarde's Herbal (1597) and Parkinson's two
books of plants are more amusing than valuable. Both
authors were guilty of unscrupulous plagiarism, a vice
which cannot be atoned for by curious figures and bits
of folk-lore, nor even by command of Shakespearean
English. Thomas Johnson's edition of Gerarde (1633)
is a far better book than the original ; Ray called it
"Gerarde emaculatus " — i.e., freed from its stains.

The succession of influential English naturalists may
be said to begin with Ray, Willughby, and Martin
Lister, all of whom belong to the last half of the
seventeenth century.

The Rise of Experimental Physiology.

1543 is a memorable year in the history of science.
Then appeared the treatise of Copernicus on the
Revolutions of the Heavenly Bodies, completed long
before, but kept back for fear of the cry of novelty
and absurdity which, as he explains in his preface,
dull men, ignorant of mathematics, were sure to raise.
The aged astronomer, paralysed and dying, was able
to hold his book in his hands before he passed away.
In the same year Vesalius, a young Belgian anatomist,
published his Structure of the Human Body, a volume
rich in facts ascertained by dissection. Some of these
facts were held to contradict the teaching of Galen.

THE RISE OF EXPERIMENTAL PHYSIOLOGY 21

Next year Vesalius was driven by the hostility of the
medical profession to burn his manuscripts and relin-
quish original work; he was not yet thirty years of age.

Galen had taught that there are two sets of vessels
in the body (arteries and veins), and that in each set
there is an ebb and flow. Knowing nothing of com-
munications between the ultimate branches of the
arteries and veins, and shrinking from the supposition
that the arteries and veins are entirely separate and
distinct, Galen had taught that the blood passes from
one set of vessels to the other in the heart. The
septum between the ventricles must be porous and allow
the blood to soak through. Vesalius did not venture
openly to challenge the physiology of Galen, but he
significantly admired the "handiwork of the Almighty,"
which enables the blood to pass from the right to the
left ventricle through a dense septum in which the eye
can perceive no openings. Fabricius of Acquapendente
in 1574 demonstrated the valves of the veins, though
he never arrived at a true notion of their action. His
celebrated pupil, William Harvey, who had been anti-
cipated on important points by the Spaniard Michael
Servetus and Realdo Columbo of Cremona, published
in 1628 a clear account, supported by adequate experi-
mental evidence, of the double circulation through the
body and the lungs, and of the communications between
the arteries and the veins in the tissues — communica-
tions which it was reserved for the next generation to
demonstrate by the microscope.

Aselli of Cremona rediscovered the lacteals in 1622;
they had been known ages before to Erasistratus, but
forgotten. Opening the abdomen of a dog, he saw a
multitude of fine white threads scattered over the
mesentery, and observed that when one of them was

22 PERIOD I.

pricked a liquid resembling' milk gushed out. Further
examination showed him that these vessels, like the
veins, possess valves which permit flow in one direction
only. Pecquet, a French physician, announced in 1651
that the lacteals open into a thoracic duct, which joins
the venous system. In 1653 Rudbeck of Upsala
described yet another set of vessels, the lymphatics ;
these again are provided with valves, and open
into the thoracic duct, but are filled with a clear
liquid.

The effect of these discoveries upon physiology and
medicine was very great, but it did not end there ; the
whole circle of biological students and a still wider
circle of men who pursued other sciences were thereby
encouraged to followthe experimental path to knowledge.
Wallis, in describing the meetings of scientific men held
in London in 1645 and following years, mentions the
circulation of the blood, the valves in the veins, the
lacteals, and the lymphatic vessels among the subjects
which had stirred their curiosity ; while the naturalist
Ray thanked God for permitting him to see the vain
philosophy which had pervaded the University in his
youth replaced by a new philosophy based upon experi-
ment— a philosophy which had established the weight
and spring of the air, invented the telescope and the
microscope, and demonstrated the circulation of the
blood, the lacteals, and the thoracic duct.

The Natural History of Distant Lands (Sixteenth
Century and Earlier).

Travel and commerce had made the ancient world
familiar with many products of distant countries. Well-
established trade routes kept Europe in communication
with Arabia, the Persian Gulf, and India. Egyptians,

THE NATURAL HISTORY OF DISTANT LANDS 23

Phoenicians, and Greeks explored every known sea,
and brought to Mediterranean ports a variety of
foreign wares. Under the Roman empire strange
animals were imported to amuse the populace ; silk,
pearls, gay plumage, dyes, and drugs to gratify the
luxury of the rich.

Long after the fall of the empire foreign trade was
kept up along the coasts of the Mediterranean. Con-
stantinople was still a great emporium. Silk was not
only imported from the East, but cultivated around
Constantinople in the sixth century. The cotton plant,
the sugarcane, the orange tree, and the lemon tree
gradually spread northward and westward until the)7
became established in Italy, Spain, and the islands of
the Mediterranean.

Western Europe had during many centuries little
share in this commerce. The large and conspicuous
animals of Africa and Asia, such as the elephant,
camel, camelopard, ostrich, pelican, parrot, and croco-
dile, would have passed out of knowledge altogether
but for chance mention in the Bible and the Bestiaries.
Little was done to supplement native food-plants and
drugs by imported products, and the knowledge of
foreign vegetation became as indistinct as that of
foreign animals.

In the thirteenth century communication between
Western Europe and the far East was restored. China
was thrown open by the Tartar conquest, and Marco
Polo was able to reach the court of Khan Kublai.
Pilgrims from the Holy Land brought back information
which, however scanty it might be, was eagerly
received. One of the earliest printed books (1486)
contains the travels of Bernard of Breydenbach, a
canon of Mainz, whose narrative is adorned by curious

24 PERIOD I.

woodcuts, in which we can make out a giraffe and a
long-tailed macaque.

The geographical discoveries of the sixteenth century
gave men for the first time a fairly complete notion of
the planet which they inhabit. Circumnavigators
proved that it is really a globe. Maps of the world,
wonderfully exact considering the novelty of the infor-
mation which they embodied, were engraved as early as
1507. The explorers of America busied themselves not
only with the preparation of charts, the conquest of
Mexico and Peru, the search for gold, and the spread of
the true faith, but also with the strange animals and
plants which they saw ; and the news which they
brought back was eagerly received in Europe. Queen
Isabella charged Columbus, when he set out for his
second voyage, to bring her a collection of bird-skins ;
but this may be rather a proof of her love of mil-
linery than of her interest in natural history. Pope
Leo X. liked to read to his sister and the cardinals the
Decades of Peter Martyr Anglerius,1 in which the
productions of the New World are described. The
opossum, sloth, and ant-eater, the humming-bird,
macaw, and toucan, the boa, monitor, and iguana, were
made known for the first time. Potatoes and maize
began to be cultivated in the south of Europe, the
tomato was a well-known garden plant, the prickly
pear was spreading along the shores of the Medi-
terranean, and tobacco was largely imported. By the
end of the seventeenth century Mirabilis and the garden
Tropaeolum had been brought from Peru, the so-called
African marigold from Mexico, and sunflowers from
North America. More than a hundred years had still

1 Letter of Peter Martyr, Dec. 26, 1515.

AGRICULTURE, HORTICULTURE, ETC. 25

to run before the evening primrose, the passion flower,
and the lobelias of America were to become familiar
to European gardeners, ipecacuanha and cinchona to
European physicians.

Agriculture, Horticulture, and Silk-Culture in the
Sixteenth Century.

During the darkest parts of the Middle Ages agricul-
ture and horticulture were regularly practised. Tyranny,
the greed of settlers, the inroads of barbarians, private
war, and superstition may destroy all that brightens
human life, but they hardly ever exterminate the popu-
lation of large districts,1 and so long as men live they
must till the soil.

The age of Charlemagne was one of cruel hardship
to the inhabitants of Western Europe, but the cartu-
laries of the great king show that the improvement of
horticulture was a matter of much concern with him.
The nobles and the religious houses kept trim gardens,
which are delineated in mediaeval paintings We know
less about the state of the peasantry, but it is clear that
they ploughed, sowed, reaped, and dug their little
gardens, however uncertain the prospect of enjoying
the produce of their labour.

The progressive Middle Ages (about 1000 to 1500
A.D.) greatly increased the comfort of the wealthy and
alleviated the miseries of the poor. We now hear of
countries (England, the Low Countries, the western
half of Germany, the northern half of Italy) where
freemen cultivated their own land, or grew rich by
trade, and these men were not content barely to support

1 The extermination of the red man in North America is the
most conspicuous case recorded in history. Australia and Tas-
mania furnish examples on a smaller scale.

26 PERIOD I.

life. Under the later Plantagenets the wool-growers
of that upland country which stretches from Lincoln-
shire to the Bristol Channel showed their wealth by
building a profusion of manor-houses and beautiful
perpendicular churches, many of which still remain.
There can be little doubt that they were attentive to
the rural industries which are so great a source ot
comfort and pleasure.

In the sixteenth and seventeenth centuries the
Flemings, a laborious and enterprising people, inhabit-
ing a fertile country, excelled the rest of Europe
in agriculture and horticulture. L'Obel, himself a
Fleming, speaks with pride of the live plants imported
into Flanders from Southern Europe, Asia, Africa, and
America. By the close of the sixteenth century, or a
few years later, the lilac, lavender, mangold, sun-
flower, tulip, and crown-imperial, the cucumber and
garden rhubarb, besides many improved varieties of
native vegetables, were sent out from Flanders to
all parts of Western Europe. During many genera-
tions English agriculture and horticulture, and not
these alone, but English ship-building, navigation,
engineering, and commerce as well, looked to the Low
Countries as the chief schools of invention and the
chief markets from which new products were to be
obtained.

Late in the sixteenth century a gentleman of the
Vivarais (the modern Ardeche), named Olivier de Serres,
wrote a book on the management of land,1 which leaves
a strong impression of the zeal for improvement which
then pervaded Europe. De Serres was above all
things intent upon extending silk-culture in France.

1 Le Thddtre d Agriculture, 1600.

AGRICULTURE, HORTICULTURE, ETC. 27

On this topic he wrote with full knowledge, having
reared silkworms for thirty-five years. The King-,
Henri Quatre, shared his hopes, and gave him practical
encouragement. It is well known that a great industry
was thus started ; by 1780 the annual yield of silk-
cocoons in France was valued at near a million sterling,
while in 1848 it had risen to four millions. De Serres
sought to promote the cultivation of the mulberry tree,
not only because its leaves are the food of the silkworm,
but because he believed that the fibres of the bast would
be serviceable in the manufacture of cordage and cloth.
He also tried to revive the ancient practice of hatching
eggs by artificial heat. We learn from him that the
turkey, recently introduced from Mexico, had already
become an important addition to the poultry-yard, while
maize from Mexico and beetroot from the Mediter-
ranean coasts were profitable crops. Among the new
appliances De Serres mentions artificial meadows,
wind and water-mills, cisterns not hewn from stone,
and greenhouses.

c 2

PERIOD II.
1661-1740

Characteristics of the Period.

IN Western Europe this was a time of consolidation
succeeding to one of violent change. Religious wars
gave place to dynastic and political wars. In France
the tumults of the preceding hundred years sank to
rest under the rule of a strong monarchy ; order and
refinement became the paramount aims of the governing
classes ; literature, the fine arts, and the sciences were
patronised by the Court. Other nations imitated as
well as they could the example of France. Learning
was still largely classical, but the anti-scholastic revolt,
which had first made itself felt three hundred years
earlier, steadily gained ground ; Descartes, Newton,
and Locke were now more influential than the Aris-
totelians. This was an age of new scientific societies
(Royal Society, Academy of Sciences of Paris, Academia
Naturae Curiosorum, etc.).

The Minute Anatomists.

Magnifying glasses are of considerable antiquity.
Seneca mentions the use of a glass globe filled with
water in making small letters larger and clearer. Roger
Bacon (1276) describes crystal lenses which might be
used in reading by old men or those whose sight was
impaired. As soon as Galileo had constructed his first
telescopes, he perceived that a similar instrument
might be caused to enlarge minute objects, and made

28

THE MINUTE ANATOMISTS 29

a microscope which revealed the structure of an insect's
eye. Within twenty years of this date the working-
opticians of Holland, Paris, and London sold compound
microscopes, which, though cumbrous as well as opti-
cally defective, revealed many natural wonders to the
curious. Simple lenses, sometimes of high power,
came before long to be preferred by working naturalists,
and it was with them that all the best work of the
seventeenth and eighteenth centuries was done.

The power of the microscope as an instrument of
biological research was in some measure revealed by
Hooke's Micrographia (1665). Robert Hooke was a
man of extraordinary ingenuity and scientific fertility,
who took a leading part in the early work of the Royal
Society. He opens his book with an account of the
simple and the compound microscope of his own day,
and then goes on to explain, with the help of large and
elaborate engraved plates, the structure of a number
of minute objects. The most interesting are : A Fora-
miniferous shell, snow-crystals, a thin section of cork
showing its component cells, moulds, a bit of Flustra,
the under side of a nettle-leaf with its epidermic cells
and stinging-hairs, the structure of a feather, the foot
of a fly, the scales of a moth's xving, the eye of a fly,
a gnat-larva, and a flea. The beauty of the plates and
the acuteness of some of the explanations are remark-
able, but lack of connection between the topics dis-
cussed hinders the Micrographia from rising to a very
high scientific level.

Swammerdam treated the microscope as an instru-
ment of continuous biological research. In his eyes it
was a sacred duty to explore with the utmost faithful-
ness the minute works of the Creator. Insects yielded
him an inexhaustible supply of natural contrivances, in

30 PERIOD II.

which closer scrutiny always brought to view still more
exquisite adaptations to the conditions of life. He was
able to throw a beam of steady light upon the per-
plexed question of insect-transformation, and swept
from his path the sophistries with which the philosophy
of the schools had obscured the change of the cater-
pillar into a moth, or of the tadpole into a frog. He
demonstrated the gradual progress of the apparently
sudden transformation of certain insects by dipping
into boiling water a full-fed caterpillar, and then ex-
posing the parts of the moth or butterfly, which had
almost attained their complete form beneath the larval
skin ; after this it was easy to discover the same parts
in the pupa.

There is no more valuable chapter in Swammerdam's
great work, the Biblia Naturcz, or Book of Nature,
than that devoted to the hive-bee. This insect had
long been a favourite study, but only those who were
armed with a microscope and skilled in minute anatomy
could solve the many difficult questions with which it
was involved. Aristotle and other ancient naturalists
had spoken of the king of the bees, which some bee-
masters of the seventeenth century had been inclined
to call the queen. Was it really true that the queen
was a female, perhaps the only female in the hive ?
This question Swammerdam decided by the clearest
anatomical proof — viz., by dissecting out her ovaries.
He pointed out the resemblances between the queen
and the workers, such as the possession of a sting by
both, but did not discover the reduced reproductive
organs of the workers, and wrongly declared that they
never lay eggs, ^e proved by elaborate dissections
that the drones are the males of the community. How
and when the queen is fertilised he could not make out.

MARCELLO MALPIGHI.

From an engraving of the oil-painting by A. M. Tobar, presented to the Royal
Society by Malpighi.

32 PERIOD II.

The dissection of the sting, the proboscis, and the com-
pound eye of the bee was a task after Swammerdam's
own heart, but so intricate that all his patience and
skill could not save him from occasional slips. He
bequeathed to his successors many noble examples of
the way in which life-histories ought to be investigated.

Malpighi of Bologna may be called the first of the
histologists, for as early as the second half of the
seventeenth century he unravelled the tissues of many
animals and plants. His work on plant-tissues was so
closely accompanied by the similar researches of an
Englishman, Nehemiah Grew, that it is not easy to
assign the priority to either. Malpighi was the first to
demonstrate the capillaries which connect the arteries
with the veins, the first to investigate the glands of the
human body and the sensory papillae of the skin. At
the request of our Royal Society he drew up an account
of the structure and life-history of the silkworm, which
is memorable as the earliest anatomical study of any
insect. Malpighi also applied his microscope to the
chick-embryo, and figured its chief stages. His ex-
position of the formation of the heart and vessels of
the chick is a marvellous example of the quick appre-
ciation of novel structures.

If we suppose the Micrographia of Hooke to be
greatly enlarged, so as to become, instead of the
passing occupation of a man busied with a hundred
other interests, the main pursuit of a long and laborious
life, we shall get a rough notion of the microscopic
revelations of Leeuwenhoek. His researches were
desultory, though not quite so desultory as Hooke's ;
he must have often spent months upon an investigation
which Hooke would have dismissed in as many weeks.
Both travelled over the whole realm of nature, and

THE MINUTE ANATOMISTS 33

lacked that concentration which made the work of
Swammerdam so productive and so lasting.

Leeuwenhoek worked with simple lenses, ground and
mounted by his own hands. It was easy to make
lenses of high magnifying power, but hard to correct

ANTONY VAN LEEUWENHOEK.

From the portrait by Verkolje, prefixed to the Epistolce ad Soc. Reg. Angl.t
Leyden, 1719.

their optical defects, to bring a sufficiently strong light
to bear upon the object, and to focus the lens. When
he wished to send out his preparations for examination
by others, he found it best to fix the objects in the

34 PERIOD II.

focus, and to provide each with a separate lens. With
such microscopes he managed to study and figure very
minute objects, such as blood-corpuscles, spermatozoa,
and bacteria. The spermatozoa were brought under
his notice by a young Dutch physician named Hamm ;
but it was Leeuwenhoek's account of them, and his
daring theory of their physiological role, which gave
them such celebrity. To Leeuwenhoek we owe the first
discovery of the rotifers, the infusoria, Hydra, the
yeast-cell, the bacteria, and the generation of aphids
without male parents.

The tradition of the minute anatomists has never been
lost, though we shall be unable to pursue it in these pages.
Lyonet (see p. 61) even surpassed Swammerdam in the
elaborate finish of some of his insect-dissections.

Early Notions about the Nature of Fossils.

Throughout the sixteenth century naturalists held
animated debates about the shells which are found far
from the sea, and even on the top of high hills. Had
they ever formed part of living animals or not? Such
a question could hardly have been seriously discussed
among simple-minded people ; but the learned men of
the sixteenth century were rarely simple-minded. They
had been trained to argue, and argument could make it
plausible that such shapes as these were generated by
fermentation or by the influence of the stars. So
prevalent were these doctrines that it entitles any
early philosopher to the respect of later generations
that he should have taken shells, bcnes, and teeth to
be evidences of animal life. In this singular roll of
honour we find the names of Cesalpini, Palissy, Scilla,
Stenson, Hooke, and Woodward.

In England the struggle between philosophy and

THE NATURE OF FOSSILS

35

common-sense was long- kept up. Dr. Ralph Cudworth
of Cambridge taught that there is in nature a subor-
dinate creative force of limited power and wisdom, to
whose imperfections may be attributed the " errors
and bungles " which now and then mar the work. To
this subordinate creative force he gave the name of
"vegetative soul," or "plastic nature." None but
Cambridge men, it would appear, felt the weight of
Cudworth's reasoning ; but several of these, and espe-
cially John Ray1 and Martin Lister, defended his
conclusions in published treatises. Lister, in a chapter
devoted to " cochlites," or shell-shaped stones, pointed
out that they differ from true shells in being of larger
size, in occurring far from the sea, in being formed of
mere stony substance, and in being often imperfect.
Some naturalists had conjectured that the living animals
of the cochlites still exist at great depths in the sea, but
Lister evidently thought otherwise.

In the eighteenth century the belief that fossils are the
remains of actual animals and plants more and more pre-
vailed, the death and sealing up of the organisms being
generally attributed to Noah's flood. The occurrence
of fossils on high mountains seemed so strong a con-
firmation of the Biblical narrative that Voltaire was
driven to invent puerile explanations in order to dispel
an inference so unwelcome to him. By the end of
the century most naturalists accepted the doctrine that
the great majority of fossils are the remains of organ-
isms now extinct — a doctrine which was enforced by
the remarkable discoveries of Cuvier (see p. 93).
Nearly at the same time William Smith established the

1 Ray came at last to believe that tossils were the remains of
actual organisms, but he was still much hampered by his theolo-
gical views.

36 PERIOD II.

important truth that almost every fossil marks with
considerable precision a particular stage in the earth's
history.

Comparative Anatomy : the Study of Biological Types.

Between 1660 and 1740 the scope of natural history
became sensibly enlarged. System had been hitherto
predominant, but the systems had been partial,
treating the vertebrate animals and the flowering
plants with as much detail as the state of knowledge
allowed, but almost ignoring the invertebrates and the
cryptogams. System was now studied more eagerly
than ever by such naturalists as Ray and Linnaeus,
but new aspects of natural history were considered,
new methods practised, new groups of organisms in-
cluded. Many remarkable vertebrates were anatomically
examined for the first time. Claude Perrault and his
colleagues of the Academic des Sciences dissected
animals which had died in the royal menagerie, and
compared the parts and organs of one animal with those
of another ; Duverney compared the paw of the lion
with the human hand ; in England Tyson studied the
anatomy of the chimpanzee, porpoise, opossum, and
rattlesnake, searching everywhere for the transitions
which he believed to connect all organisms, and to
form " Nature's Clew in this wonderful labyrinth of the
Creation." The new microscopes helped to bring the
lower and smaller animals into notice. From 1669,
when Malpighi described the anatomy and life-history
of the silkworm, a succession of what we now call
biological types were studied ; among these were many
invertebrates. Edmund King and John Master con-
tributed to Willis's treatise De Anima Brutorum (1672)
the anatomies of the oyster, crayfish, and earthworm,

ADAPTATIONS OF PLANTS AND ANIMALS 37

all illustrated by clear and useful plates. Heide (1683)
wrote an account of the structure of the edible mussel
(Mytilus), in which mention is made of the ciliary
motion in the gill; Poupart (1706) and Me"ry (1710)
wrote accounts of the pond-mussel (Anodon). Swam-
merdam's elaborate studies of insects and their trans-
formations were followed up by a long succession of
memoirs by Frisch in Germany, Reaumur in France,
and (shortly after the close of the period now under
discussion) De Geer in Sweden. The extraordinary
diligence and power of Swammerdam and Reaumur
give a very prominent place in the biology of the seven-
teenth and eighteenth centuries to the structure and
life-histories of insects. The great generalisations of
comparative anatomy do not belong to this period ;
nevertheless, sagacious and luminous remarks are not
wanting.

Adaptations of Plants and Animals : Natural Theology.
Natural adaptations and some of the problems which
they suggest were much studied during this period.
Bock and Cesalpini had discussed still earlier the
mechanisms of climbing plants, aquatic plants, and
plants which throw their seeds to a distance. Swam-
merdam figured, not for the first time, the sporangia
and spores of a fern ; Hooke the peristome of a moss.
The early volumes of the Academic des Sciences con-
tain many studies of natural contrivances. Perrault
described the retractile claw of the lion, the pointed
papillae on its tongue, the ruminant stomach and the
spiral valve of a shark's intestine. He improved upon
Hooke's account of the structure of a feather, and his
magnified figures of a bit of an ordinary quill and of a
bit of an ostrich-plume might be inserted into any

38 PERIOD II.

modern treatise on animal structure.1 Poupart followed
the later stages of the development of a feather. Me>y
gave a minute yet animated description of the wood-
pecker's tongue, explaining how it is rendered effective
for the picking up of insects, how it is protruded and
retracted, how it is stowed away when not in use.
Tournefort figured the oblique fibres of a leguminous
pod, which he called muscles, and showed how they
twist the valves and squeeze out the seeds.

Natural theology was much in the thoughts of the
naturalists who studied and wrote between 1660 and
1740. Ray discoursed upon the Wisdom of God as
manifested in the Creation. Swammerdam regularly
closed the divisions of his Biblia Naturce with expres-
sions of pious admiration. A long list of books
expressly devoted to the same theme might be given.2
One weakness of the natural theologians was their habit
of looking upon the universe as existing for the con-
venience of man. Still more fatal was the partiality
with which they stated the facts. While they dwell
upon the adaptations which secure the welfare of
particular animals or plants, they are silent about the
sufferings caused by natural processes.

Spontaneous Generation.

During many ages every naturalist thought that he
had ample proof of the generation without parents of
animals and plants. He knew that live worms appear
in tightly-closed flasks of vinegar ; that grubs may be
found feeding in the cores of apples which show no
external marks of injury ; and that weeds spring up in

1 The second of the two has actually been so treated, but with-
out mention of Perrault's name.

2 See Krause's Life of Erasmus Darwin.

SPONTANEOUS GENERATION 39

gardens where nothing1 of the sort had been seen before.
Certain kinds of animals and plants are peculiar to parti-
cular countries ; what more likely than that they should
be the offspring of the soil? Fables and impostures
supported what all took to be facts of observation.
The great name of Aristotle was used to confirm the
belief that insects were bred from putrefaction ; eels
and the fishes called Aphyae from the mud of rivers.
A belief in a process of transmutation was often
combined with a theory of spontaneous generation.
Francis Bacon not only held that insects were born of
putrefying matter, but that oak boughs stuck in the earth
produced vines.

Towards the end of the seventeenth century it
occurred to one inquiring mind that a particular case
of spontaneous generation, which had been accepted by
everybody without hesitation, was capable of a less
mysterious explanation. Francesco Redi (1626-1698),
physician to the Duke of Tuscany, published in 1668
an account of his experiments on the generation of
blow-flies. He found that the flesh of the same animal
might yield more than one kind of fly, while the same
fly might be hatched from different kinds of flesh. He
saw the flies laying their eggs in flesh, and dissected
eggs out of their ovaries. When he kept off the flies
by gauze the flesh produced no maggots, but eggs were
laid on the gauze. Redi concluded that flies are gener-
ated from eggs laid by the females. He also studied
insect-galls, and the worms which feed on growing
seeds. Like earlier observers, he was baffled by finding
live grubs in galls or nuts which were apparently intact,
and by the parasitic worms which are now and then
found in the brain-case and other closed cavities of
quadrupeds. Such instances led him to jump at the

40 PERIOD II.

supposition of a "vivifying" principle," which generated
living things of itself — a supposition contrary to the
truer doctrine which he taught elsewhere. Vallisnieri
was able to explain how the egg is introduced into the
rose-gall, which a little later shows no mark of injury ;
while Malpighi examined the young nut and found both
hole and egg. How parasitic worms reach the brain-
case of the sheep could be explained only in a later
age. Meanwhile Swammerdam, Leeuwenhoek, Re"au-
mur, and many other special students confirmed and
extended Redi's experiments on the blow-fly ; and every
fresh instance of normal generation in a minute organ-
ism did something to weaken the belief in spontaneous
generation.

Late in the eighteenth century that belief revived in
a form less easy of refutation. Leeuwenhoek had
discovered that organic matter putrefying in water often
yielded abundance of microscopic organisms of the most
diverse kinds, many of which could resist drying in
air and resume their activity when moistened again.
Buffon, ever ready with a speculative explanation,
maintained that such minute organisms were spon-
taneously generated, and that they were capable of
coalescing into bodies of larger size and more complex
structure. Needham supported Buffon's theories by
experiments. Taking infusions of meat, corking
them, and sealing them with mastic, he subjected
them to a heat which he thought intense enough to
destroy life ; after an interval the microscope revealed
an abundance of living things which he affirmed to have
been generated from dead matter. Spallanzani repeated
Needham's experiments with stricter precautions, sealed
his flasks by fusing their necks in a flame, and then im-
mersing them in boiling water until they were heated

THE NATURAL HISTORY OF JOHN RAY 41

throughout. The infusions in such flasks remained
limpid ; no scum formed on the surface ; no bad smell
was given off when they were opened ; and no signs of
life could be detected by the microscope. To meet the
objection that the vegetative force of the infusions had
been destroyed by long heating he simply allowed air to
enter, when the micro-organisms quickly reappeared.
Spallanzani's methods, though far better than any which
had been employed before, are not quite unimpeach-
able, and could not be relied upon in an atmosphere
rich in germs ; but they sufficed to create a strong
presumption that life is set up in infusions by germs
introduced with the air.

This was by no means the end of the controversy,
which broke out again and again until it was laid to
rest, whether finally or otherwise it would be unwise to
predict, by the experiments of Pasteur.

The Natural History of John Ray.

The sixteenth, seventeenth, and eighteenth centuries
each possessed at least one naturalist of wide learning
and untiring diligence, who made it his care to collect
information concerning all branches of natural history,
to improve system, and to train new workers. Gesner,
Ray, and Linnaeus occupied in succession this honour-
able position.

Ray was originally a fellow of Trinity College,
Cambridge, who had risen into notice by proficiency in
academical studies. He then became inspired by the
hope of enlarging the knowledge of plants and animals,
and of producing what we should now call a descriptive
fauna and flora of Great Britain. His plan contem-
plated close personal observation, travels at home and
abroad, and the co-operation of pupils and friends.

D

JOHN RAY.

From an old engraving of the portrait by Faithorn.

THE NATURAL HISTORY OF JOHN RAY 43

His chief assistant was Francis Willughby, a young
man of wealth and good family ; while Martin Lister, a
Cambridge fellow, who had already laboured at natural
history with good effect, undertook an independent
share in the work. Ray wisely began with what lay
close at hand, and published a catalogue of the plants
growing around Cambridge. This was not a mere list
of species, but a note-book charged with the results of
much observation and reading. Journeys in quest of
fresh material were begun. Then Ray's well-laid
scheme was disconcerted by calamities which would
have overwhelmed a less resolute man. He was driven
from Cambridge by the Act of Uniformity, and forced to
serve for years as a tutor in private families. When
this servitude came to an end his only livelihood was a
small pension, bequeathed to him by Willughby, on
which he lived in rustic solitude. Willughby was cut
off at the age of thirty-six, having accumulated much
information but completed nothing. Lister became a
fashionable physician, to whom natural history was
little more than an elegant diversion. The whole
burden of the enterprise fell upon Ray, who manfully
bore it to the end. He completed his own share of the
work, prepared for the press the imperfect manuscripts
of Willughby, and before he died was able to fulfil the
pledge which he had given forty years before in the
prosperity of early manhood. It is needless to say that
the natural history of Britain, executed in great part by a
poor and isolated student, fell far short of what Ray might
at one time have reasonably expected to accomplish.

Ray, like other early naturalists, saw that a methodi-
cal catalogue of species, arranged on some principle
which could be accepted in all times and in all countries,
was indispensable to the progress of natural history,

D2

44 PERIOD II.

and such a catalogue formed an essential part of his
plan. Perhaps he was a little deficient in that discern-
ment of hidden affinities which has been the gift of
great systematisers, but his industry, learning, and
candour accomplished much. Quadrupeds, birds, rep-
tiles, fishes, insects, and plants of every sort were
reviewed by him. British species naturally received
special attention, but Ray did not fail to make him-
self acquainted with the natural productions of foreign
countries, partly by his own travels, and partly by
comparing the descriptions of explorers. He seized
svery opportunity of investigating the anatomy and
physiology of remarkable animals and plants, and
attended to the practical uses of natural history.
British naturalists owed to him the first serviceable
manuals for use in the field.

Ray was the first botanist who formally divided
flowering plants into Monocotyledons and Dicotyledons.
It was only natural that he should now and then have
misplaced plants whose general appearance is deceptive
(lily of the valley, Paris, Ruscus, etc.). He was
perhaps the first to frame a definition of a species ; but
here his success, as might be expected, was not great.
A species was with him a particular sort of plant or
animal which exactly reproduces its peculiarities gener-
ation after generation. Any plant, for example, which
comes up true from seed, would according to Ray
constitute a species. By this definition many races of
plants which are known to have been produced in
nurseries would rank as true species.

The Scale of Nature.

No one can closely examine a large number of plants-
and animals without perceiving real or imaginary

THE SCALE OF NATURE

45

gradations among- them. The gradation, shrews,
monkeys, apes, man, is not very far from a real genea-
logical succession, confirmed by structural and his-
torical proofs. The gradation, fish, whale, sheep, on
the other hand, though it seemed equally plausible to
early speculators, is not confirmed by structure and
history. In the age of Aristotle and for long after-
wards the ostrich was believed to be a connecting- link
between birds and mammals, because it possessed, in
addition to obvious bird-like features, a superficial
resemblance to a camel (long neck, speed in running-,
desert haunts, and a rather imaginary resemblance
in the toes). Sedentary, branching- zoophytes were
quoted as intermediate between animals and plants ;
corals and barnacles as intermediate between animals
or plants and stones. Aristotle was convinced of the
continuity of nature ; his scale of being- extended from
inanimate objects to man, and indicated, as he thought,
the effort of nature to attain perfection. Malpighi
traced analogies between plants and animals, identify-
ing the seed and egg, as many had done before him,
assuming that viviparous as well as oviparous animals
proceed from eggs, and comparing the growth of metals
and crystals with the growth of trees and fungi.
Leibnitz believed that a chain of creatures, rising1 by
insensible steps from the lowest to the highest, was a
philosophical necessity. Buffon accepted the same
conclusion, and affirmed that every possible link in the
chain actually exists. Pope reasoned in verse about a
"vast chain of being," which reaches from God to man,
and from man to nothing. The eighteenth century was
filled with the sound.

Bonnet in 1745 traced the scale of nature in fuller
detail than had been attempted before. He made

46 PERIOD II.

Hydra a link between plants and animals, the snails and
slugs a link between mollusca and serpents, flying
fishes a link between ordinary fishes and land verte-
brates, the ostrich, bat, and flying fox links between
birds and mammals. Man, endowed with reason,
occupies the highest rank; then we descend to the
half-reasoning elephant, to birds, fishes, and insects
(supposed to be guided only by instinct), and so to the
shell-fish, which shade through the zoophytes into
plants. The plants again descend into figured stones
(fossils) and crystals. Then come the metals and demi-
metals, which are specialised forms of the elemental
earth. Water, air, and fire, with perhaps the sether of
Leibnitz, are placed at the bottom of the scale.

In Bonnet's hands the scale of nature became an
absurdity, by being traced so far and in so much detail.
It was not long before a reaction set in. The great
German naturalist, Pallas, in his Elenchus Zoophytorum
(1766) showed that no linear scale can represent the
mutual relations of organised beings ; the branching
tree, he said, is the appropriate metaphor. Cuvier
taught that the animal kingdom consists of four great
divisions which are not derived one from another, and
his authority overpowered that of Lamarck, who still
maintained that all animals form a single graduated
scale. A complete reversal of opinion ensued, so com-
plete that at length the theologians, who had once seen
in the scale of nature a proof of the wisdom of Provi-
dence, were found fighting with all their might against
the insensible gradations which, according to Darwin's
Origin of Species, must have formerly connected what
are now perfectly distinct forms of life.

The eighteenth-century supporters of continuity in
nature were not merely wrong in picturing the organised

THE SEXES OF FLOWERING PLANTS 47

world as a simple chain or scale. They were also
wrong- in assuming1 that all the links or steps still exist.
We can now see that vast numbers are irrecoverably
gone. It is a safe prophecy that the filiation of species
will never be grasped by the intelligence of man except
in outline, and even an outline which shall truly express
the genetic relations of many chief types is unattainable

at present.

The Sexes of Flowering Plants.

As soon as men began to raise plants in gardens, or
even earlier, they must have remarked that plants
produce seeds, and that seeds develop into new plants.
The Greeks (Empedocles, Aristotle, Theophrastus)
recognised that the seed of the plant answers to the
egg of the animal, which is substantially though not
literally true. None of the three understood that a
process of fertilisation always, or almost always, pre-
cedes the production of seed. Had the date-palm,
whose sexes are separate, and which has been artificially
fertilised from time immemorial, been capable of cultiva-
tion in Greece, Aristotle would not have said that plants
have no sexes, and do not require to be fertilised. His
pupil, Theophrastus, knew only by hearsay of the male
and female date-palms, and affirmed that both bear
fruit. Pliny, three hundred years later, called pollen
the fertilising substance, and gave it as the opinion of
the most competent observers that all plants are of two
sexes. The revivers of botany paid no attention to
pollen or the function of the flower ; it is more sur-
prising that in the following- century Malpighi, who had
diligently studied the development of the plant-embryo,
should give so superficial an account of the stamen and
its pollen. About the same time Grew and Millington
expressed their conviction that " the attire " (anthers)

48 PERIOD II.

" doth serve as the male, for the generation of the
seed."1 A few years later Ray2 speaks of the mascu-
line or prolific seed contained in the stamens. In
1691-4 Camerarius, professor at Tubingen, brought
forward clear experimental proof that female flowers,
furnished only with pistils, produce seeds freely in the
neighbourhood of the male or staminate flowers, but
fail to do so when isolated. He distinctly inferred that
the anthers are male organs and the pistil the female
organ. The claim set up on behalf of Linnaeus that he
demonstrated, or helped to demonstrate, the sexes of
flowering plants has little foundation in fact. To make
out such details of the process of fertilisation as the
formation of pollen-tubes, the penetration of the ovules
and the fusion of nuclei required the improved micro-
scopes of the nineteenth century.

The almost universal presence both in plants and
animals of a process of fertilisation is a fact whose
physiological meaning we but imperfectly grasp.
Modern research has shown that the pollen-tube is
exceptional and confined to the flowering plants ; the
motile filament of cryptogams, analogous to the sper-
matozoon of animals, is no doubt a relatively primitive
structure, which gives one of the strongest indications
of the common origin of all forms of life.

1 Crew's Anatomy of Plants, 1682. a Wisdom of God, 1691.

PERIOD III.
1741-1789

Characteristics of the Period.

THE chief historical events are the decline of the French
monarchy, the French revolution, the rise of Prussia,
the expansion of England, and the American Declaration
of Independence. In the history of thought we remark
the introduction of the historical or comparative method,
which seeks to co-ordinate facts and to trace events to
their causes. Science steadily grows in influence, and
freethought wins many triumphs ; this is the age of
Voltaire, Rousseau, and the Encyclopaedists, of David
Hume, of the French economists and Adam Smith.

Systems of Flowering- Plants : Linnseus and the Jussieus.

Linnaeus is remembered as a man of great industry,
enterprise, and sagacity, who was inspired from boyhood
by a passion for natural history and spent a long life in
advancing it. He was early recognised as a leader in
more than one branch of the study.

L'Obel, Morison, and Ray had laboured to found a
natural system of flowering plants, and it was they who
laid the foundation upon which all their successors have
built. The work did not, however, go steadily forward
on the original plan. When Linnaeus entered upon the
scene the prevalent systems were only moderately
natural, and far from convenient in practice. To place
the undescribed species which poured in from North
America and other distant countries was a difficult task,

49

50 PERIOD III.

with which the universities and botanic gardens of
Europe could but imperfectly cope. Linnaeus, who had
the instincts of a man of business, saw that botany was
falling into confusion, and that the only remedy was a
quick and easy method, which could be mastered in a
few days and applied with certainty. No such method,
he well knew, could take into account all the intricate
affinities of plants, but to devise a perfect method
required the labours of generations of botanists ; mean-
while a temporary expedient, full of faults it might be,
would remove a pressing evil. Flowering plants had
been arranged by the divisions of the ovary, or by the
petals and sepals, with no very satisfactory results ; it
occurred to Linnaeus to try the number of the stamens
and styles. Any such method was bound to present
many anomalies, associating plants which are only
distantly related, and separating plants which are
closely related ; but some of the worst anomalies were
avoided and some well-established families (Crucifers,
Composites, Labiates) retained at the expense of sym-
metry. Not even the pressing need of simple defini-
tions, which was allowed to spoil so natural a group as
the Umbellifers,1 could induce Linnaeus to place Ranun-
culus and Potentilla in the same class.

Linnaeus gained currency for his system by connecting
it with the newly accepted doctrine of sexes in plants.
That doctrine was not conceived nor demonstrated by
him (see p. 48), and it had, as we now see, no further
connection with classification by stamens and styles
than that it explained the almost universal occurrence
of such parts in flowering plants. But Linnaeus had
persuaded himself that he had done more to establish

1 By associating1 with them a number of alien genera.

SYSTEMS OF FLOWERING PLANTS 51

the existence of sexes in plants than anybody else, and
that the physiological importance of stamens and styles
was a proof of their systematic value. Neither of these
beliefs can stand inquiry, but both were extremely influ-
ential on contemporary opinion. The so-called Sexual
System achieved an immense success everywhere but in
France and Germany. Botanists of small experience
were now able to say whether the plants which seemed
to be new were really undescribed or not ; if undescribed,
what was their appropriate place in the system. The
congestion of systematic botany was relieved.

The great naturalist appealed to posterity by publish-
ing the sketch of a natural system of flowering plants,
which he accompanied by judicious expositions of the
philosophy of classification. He had the permanent
reform of systematic botany really at heart ; he did not
believe that his own Sexual System could be final ; and
he was glad to help in setting up a better one. To this
end he united groups of genera into families which he
did not pretend to define, being often guided only by an
obscure sense of natural bonds of union. Bernard de
Jussieu, one of the most patient and observant of sys-
tematists, devoted his life to the same task, and profited
by the example of Linnaeus. He published nothing, but
found expression for his views in the arrangement of a
botanic garden at Versailles. His ideas were after-
wards developed by his nephew, A. L. de Jussieu, in
the Genera Plantarum (1789).

Affinity became at length the avowed basis of every
botanical system. No convenience in practice, no
agreement or difference in habit, was knowingly per-
mitted to override this mysterious property. What
then is affinity ? What are natural groups of animals
and plants, and how do they arise ? Until the year

52 PERIOD III.

1859 no one could tell. The terse maxims of Linnaeus
helped to guide naturalists into the right road, but a
single fact shows how inadequate they were. Linnaeus
emphatically and repeatedly declared his belief in the
constancy of species. But if species were really con-
stant, affinity between species must have been no more
than a delusive metaphor ; the resemblances between
distinct species could not, on that supposition, be the
effect of inheritance.

Linnaeus' imperfect appreciation of the fundamental
difference between a natural classification of living
things and such classifications as man makes for his
own practical ends is further revealed by his admission
of a third kingdom of nature.1 Not only animals and
plants, but rocks and minerals as well, had, he thought,
their genera and species. The genus and species thereby
become mere logical terms, independent of inheritance
and of life itself.

Linnaeus had a passionate love of order and clearness,
enforced by an inexhaustible power of work. Hence he
was able to serve his own generation with great effect,
to methodise the labours of naturalists, to devise useful
expedients for lightening their toil (such as his strict
binomial nomenclature),2 and to apply scientific know-
ledge to the practical purposes of life. But the com-
plexity of nature is not to be suddenly and forcibly
reduced to order, and much of Linnaeus' work had to
be done over again in a different spirit. Cuvier fur-
nishes a somewhat parallel case. Cuvier too was an
indomitable worker. His power of organisation moved
the wonder of Napoleon, and there has been no greater

1 The third kingdom of nature was taken from the alchemists.

2 The binomial nomenclature had been gradually coming in
ever since the time of the Bauhins.

CARL VON LINN£ (CAROLUS LINN^US).

From an engraving (1779) after the portrait by Roslin

54 PERIOD III.

master of clear thought and clear expression. But, like
Linnaeus, Cuvier overlooked much that was already
obscurely felt and clumsily worded by brooding philo-
sophers, germs of thought which were destined to
become all-powerful in the course of a generation or
two. It must not be supposed that the labours of
Linnaeus and Cuvier were bestowed in vain. All that
was really valuable in their writings has been saved,
and biology will never forget how much it owes to their
life-long exertions.

Reaumur and the History of Insects.

Reaumur was born to wealth, and made timely use
of his leisure to study the sciences and win for himself
a place among natural philosophers. His inclinations
directed him first towards mathematics, physics, and, a
little later, towards the practical arts. He took a
leading part in a magnificent description of French
industries, which had been undertaken by the Academic
des Sciences. Not content with describing the pro-
cesses in use, he perpetually laboured to improve them.
The manufacture of steel, tin-plate, and porcelain, the
hanging of carriages and the fitting of axles, the im-
provement of the thermometer, glass hives, and the
hatching of fowls' eggs by artificial heat are among
the many objects to which his attention was directed.
Natural History gradually took a more and more
prominent place in his studies, and a great History of
Insects engaged the last years of his busy life.

Reaumur was neither an anatomist nor a systematist,
at least he gained no distinction in either of these
branches of biology. No biological laboratory had
been dreamt of in his day ; he lacked the manipulative
skill of Swammerdam or Lyonet ; he was no draughts-

RfiAUMUR AND THE HISTORY OF INSECTS 55

man, and had to engage artists to draw for him. One
qualification of the first importance, however, he
possessed in a high degree, the scientific mind. As he
watched the acts of an insect, questions at once
sagacious and practical suggested themselves in
abundance, and these questions he set himself to
answer in the best possible way — viz., by observation
and experiment. In close attention to the activities of
living things his ingenuity and patience found a bound-
less sphere of exercise. Moreover all that he had seen
he could relate in a simple but picturesque manner,
using the language familiar to the best French society
in the generation next after Madame de Se'vigne'.
Diffuse but clear, amusing but never frivolous, he won
and kept the attention of a multitude of readers, the
best of whom were incited to adopt his methods or to
pursue inquiries which he had indicated. His greatest
successes were won in observing and interpreting the
natural contrivances of insects, the means by which
they get their food and provide for their safety ; their
transformations, instincts, and societies. Kirby and
Spence, which is still one of the best popular accounts
of insects in English, is largely based upon Rdaumur ;
so are other well-known treatises, in which the debt is
less frankly acknowledged. Rdaumur greatly enlarged
the knowledge of all kinds of insects except the beetles
and Orthoptera, which he did not live to describe, and
to this day his Histoire des Insectes is a work of funda-
mental importance, with which every investigator of
life-histories is bound to make himself acquainted.

No abstract of Reaumur's Histoire des Insectes is
possible, but we may at least give one example of his
mode of treatment. Let us select his account of the
proboscis of a moth, the first full account that was ever

$6 PERIOD III.

given. He tells us that all moths have not an effective
proboscis, though he does not explain how some of
them can dispense with what seems so necessary an
organ ; this omission has been made good by later
entomologists. The proboscis, he goes on, springs
from the head, just between the compound eyes. When
at rest, it takes up very little room, for it is spirally
rolled, like a watch spring ; in some cases it makes as
few as one and a half or two turns, in others as many
as eight or ten ; the base is often concealed by a pair of
hairy palps, which serve as feelers. Careful study of a
moth as she flits from flower to flower shows that she
alights on the plant, unrolls her proboscis, passes it into
the corolla, withdraws it, perhaps coils it for an instant,
and then plunges it again into the tube. When this
manoeuvre has been repeated several times, the moth
flies off to another flower.

Some moths have a tape-like proboscis ; in others it
is cylindrical. It can be made to protrude by gentle
pressure on the head, or be unrolled by a pin passed
into the centre of the spire ; it is composed of innumer-
able joints, and tapers from the base to the tip. When
forcibly unrolled, it often splits lengthwise into halves.
At the time of escape from the chrysalis the halves are
always free, and they require careful adjustment in
order that a continuous sucking-tube may be obtained.
A newly emerged moth may be seen to roll and unroll
its proboscis repeatedly, until at last the halves cohere
in the proper position. Sometimes they begin to dry
before the operation is completed, the half-tubes get
curled, and then the unfortunate moth becomes
incapable of feeding at all. Each half is a demi-canal,
whose meeting edges interlock by minute hooks. The
mechanism reminds Reaumur of that which connects

THE BUDDING-OUT OF NEW ANIMALS 57

the barbs of a feather ; in both cases the hooks can be
adjusted rapidly and completely by stroking- from base
to tip, and in both a water-tight junction is obtained.
Besides the central canal, along which fluids are sucked
up, there are lateral canals (tracheae) filled with air.

Reaumur was careful to correct his anatomical
studies by close observation of the live insect. He
reared an angle-shades moth, which he kept several
days without food. When he saw it repeatedly extend-
ing its proboscis, he put near it a piece of sugar. The
moth at once began to suck, and became so absorbed
in satisfying its hunger that it allowed Reaumur to
carry it on a sheet of paper to a window and to examine
it closely with a lens. The proboscis was sometimes
extended for several minutes at a time, and then rolled
up for an instant ; its tip was either employed in explor-
ing the surface or closely applied to the sugar. By
means of the lens a slender column of liquid was seen
to pass along the central canal towards the head. Now
and then, however, a limpid fluid was seen to pass
down the proboscis ; this was the saliva which was
used to moisten the sugar, and then sucked up again.

The Budding-out of New Animals (Hydra) : another
Form of Propagation without Mating (Aphids).

In the year 1744 a young Genevese, Abraham
Trembley, tutor in the family of Bentinck, who was
then English resident at the Hague, rose into sudden
fame by a solid and well-timed contribution to natural
history. Trembley and his pupils used to fish for
aquatic insects in the ponds belonging to the residence,
and in the summer of 1740 he happened to collect some
water-weeds, which he put into a glass vessel and set
in a window. When the floating objects had come to

58 PERIOD III.

rest, a small green stalk, barely visible to the naked
eye, was found attached to one of the plants. From
one end of the stalk filaments or tentacles were seen to
project, and these moved slowly about. When the
vessel was shaken the stalk and tentacles contracted,
but soon extended themselves again. Was this object
a plant or an animal? Its shape and colour were those
of a plant, and sensitive plants were known which
drooped when touched or shaken. Further observation
showed that it could move from place to place, which
favoured the animal interpretation. Trembley deter-
mined to cut the stalk in two ; if the halves lived when
separated the fact would favour the plant-theory. The
halves at first gave no signs of life beyond occasional
contraction and expansion, but after eight days small
prominences were seen on the cut end of the basal
half. Next day the prominences had lengthened ; on
the eleventh day they seemed to be growing into
tentacles. Before long eight fully formed tentacles
were visible, and Trembley had two complete specimens
in place of one ; both were able to move about.

After four years of observation a handsome quarto
volume was published, which told the history of " The
freshwater Polyp," a name suggested by Reaumur ;
the Latin name of Hydra was given by Linnaeus.
Hydra had been discovered and slightly described forty
years before by Leeuwenhoek, who had seen two young
polyps branching from one parent and spontaneously
becoming free. Trembley made out all that a simple
lens, guided by a skilful hand and a keen eye, could
discover. Thirteen plates were admirably engraved by
another amateur, Pierre Lyonet, who was in all respects
a fit companion for Trembley. It was proved that
Hydra preyed upon living animals, especially upon the

THE BUDDING-OUT OF NEW ANIMALS 59

Daphnia or water-flea. When it was well nourished it
branched spontaneously again and again, forming1 a
compound mass made up of scores or even hundreds
of polyps, all connected with a single base. The power
of locomotion and the power of devouring prey were
held to settle the animal nature of Hydra, a decision to
which zoologists have ever since adhered. Lyonet
went on to try the effect of division upon some common
freshwater worms, and found that each part grew into
a complete worm. Artificial division is not indispens-
able ; in the worm called Nais division takes place
spontaneously at certain seasons, one segment dividing
repeatedly, so as to form the segments of a complete
new individual. The process may be repeated until a
chain of worms is produced, which at length breaks
up.1

A nail was thus driven in a sure place. The concep-
tion of an animal was enlarged, for it was shown that
an animal may branch and multiply in a way hitherto
supposed to be peculiar to plants. The old connecting
links between animals and plants (zoophytes, sponges,
etc.) had never been really investigated ; no one knew
what sort of organisms formed or inhabited their plant-
like skeletons. But Hydra, thanks to Trembley's
description, furnished a clear example of an animal
which possessed some of the attributes of a plant.
Forms more ambiguous than Hydra, such as Volvox
and Euglaena, were ultimately to make the distinction
between animal and plant very uncertain and shadowy.
It was Hydra that gave the first clue to the structure of

1 This discovery is usually attributed to Bonnet, but the testi-
mony of Reaumur (Hist, des Jnsecfes, Vol. VI., p. Ivi.) and of
Trembley (Hist, des Polypes d'eau douce, p. 323) is decisive in
favour of Lyonet.

E2

bo PERIOD III.

the zoophytes, and dispelled the false notion that corals
are plants, bearing flowers, fruits, and seeds.

Baer1 has remarked that Trembley's discovery
appreciably modified the teaching of physiology by
showing that an animal without head, nerves, sense-
organs, muscles, or blood may perceive, feed, grow, and
nove about.

At the time when Trembley was demonstrating the
asexual propagation of Hydra, Bonnet (supra, p. 45)
was demonstrating the asexual propagation of aphids.
Both naturalists were natives of Geneva, and both, as
well as their associate Lyonet, were in a sense pupils
of Reaumur, who not only set them an admirable
example, but directed their attention to promising
researches and discussed with them the conclusions
which might be drawn. Reaumur's experience had
seemed to confirm Leeuwenhoek's statement (supra,
p. 34) that aphids produce young alive, even though
no males are to be found among them ; but unlucky
accidents defeated his intention to confirm it by experi-
ment, and when Bonnet asked him to suggest a piece
of work Reaumur gave him the aphid problem.2

Bonnet filled a flower-pot with moist earth, intro-
duced a food-plant together with a single new-born
aphid, and covered all up with a bell-jar. In twelve
days the aphid produced its first young one ; in a month
ninety-five had been born from the same unfertilised
parent. As many as five generations were obtained
without the intervention of a male, each successive
parent having been isolated from the moment of its
birth. It was, however, discovered, apparently by

1 Reden, Vol. I., pp. 109, 154.

2 Trait^ d ' Insectologie, premiere partie. Two vols. 12 mo.
Paris, 1745.

HISTORICAL OR COMPARATIVE METHOD 61

Lyonet, that though viviparous reproduction without
males went on regularly so long- as food was plentiful,
males appeared towards the end of summer, and
fertilised the eggs which were destined to outlast the
winter.

The aphids added a new and peculiar example to the
known cases of asexual propagation (plants and Hydra).
Much discussion followed, but the physiology of that
age (and the same is true .of the physiology of our own
age) was unable to reveal the full significance of the
observed facts. Insects have since furnished many
instances of unfertilised eggs which yield offspring.
One such instance was already recorded, though neither
Leeuwenhoek, Reaumur, nor Bonnet knew of it. In
the year 1701 Albrecht of Hildesheim placed a pupa
in a glass vessel and forgot it. A moth hatched out
and laid eggs, from which a number of caterpillars
issued.

Lyonet, whom we have more than once had occasion
to mention, afterwards became celebrated as the author
of one of the most laborious and beautiful of insect-
monographs. The structure of the larva of the goat-
moth was depicted by him in eighteen quarto plates,
crowded with detail.

The Historical or Comparative Method: Montesquieu
and Buffon.

About the middle of the eighteenth century we remark
the introduction of a new, or almost new, method of
investigation, which was destined to achieve great
results. Hitherto many men had been sanguine enough
to believe that they could think out or decide by argu-
ment hard questions respecting the origin of what they
saw about them. It was easier, but not really more

62 PERIOD III.

promising1, to resort to ancient books which contained
the speculations of past generations of thinkers. Now
at last men set themselves to study what is, and by the
help of historical facts to discover how it came to be.
The new method was first applied to the institutions
of human society, but was in the end extended to the
earth, life on the earth, and a multitude of other impor-
tant subjects.

Most writers call this method historical, because
history is the chief means by which it seeks to trace
causes. Others call it genetic, because it g-oes back,
whenever it can, to origins. It might also be called
comparative, because it compares, not only things which
are widely separated in time, but also things which are
separated in space, things which differ in form or ten-
dency because they have a common origin, and things
which differ in origin because they have a common form
or tendency. Whether the institutions, arts, and usages
of mankind, or the species of plants and animals, are in
question, the study of history, together with the com-
parative study of what now exists, results in increased
attention to development, and this again brings to light
the continuity of all natural agents and processes — con-
tinuity in time and continuity among- co-existences.
Since the new method has succeeded in tracing the
causes of many phenomena which once seemed to obey
no law, it has done much to strengthen the belief in
universal causation.

Down to the middle of the eighteenth century the
book of Genesis had been almost unanimously accepted
in Europe as the only source of information concerning
the origin of the world, of man, of languages, of arts
and sciences. The whole duration of the world was
restricted to so brief a space that slow development

HISTORICAL OR COMPARATIVE METHOD 63

was impossible, and it was assumed that early history
of every kind must be miraculous.1

Montesquieu (Esprit des Lots, 1748) was the first to
exhibit on an impressive scale the power of the his-
torical method. Natural development, determined by
unalterable conditions, was with him the key to the
right understanding of the past. It is well known that
here and there a great thinker had before Montesquieu
framed something like the same conception. The
Politics of Aristotle2 and Vico's study of the historical
evolution of the Roman law (1725) are memorable
anticipations. By 1748, the date of the Esprit des Lois,
or 1749, the date of Buffon's first volumes, which come
next before us, Newton's Principia had made students
of physics and astronomy practically familiar with the
notion of universal causation.

Buffon's place in the history of science is that of one
who accomplished great things in spite of weaknesses
peculiarly alien to the scientific spirit. It was mainly
he who, by strenuous exertions and largely at his own
cost, transformed the gardens from which the king's
physicians used to procure their drugs into what we
now know as the Jardin des Plantes. By the untiring
labours of fifty years he produced a Natural History in

1 In circles untouched by general European thought such beliefs
lasted much later. Sir Francis Galton {Memories of My Life,
p. 67) says : "The horizon of the antiquarians was so narrow at
about the date (1840) of my Cambridge days that the whole history
of the early world was literally believed, by many of the best-
informed men, to be contained in the Pentateuch. It was also
practically supposed that nothing more of importance could be
learnt of the origin of civilisation during classical times than was
to be found definitely stated in classical authors."

2 " If anything could disentitle Montesquieu's Esprit des Lois to
the proud motto, Prolem sine matre creatam, it would be its close
relationship to the Politics." (A. W. Benn's Greek Philosophers.
Vol. II., p. 429.)

PERIOD III.

thirty-six volumes crowded with plates. Having- won
for himself a place side by side with Montesquieu and
Gibbon, he employed it to direct attention to the larger
questions of biology and geology. He was a pro-
nounced freethinker, who promulgated bold views with
a dexterity which saved him from condemnation by the
theological tribunals. When his opinions were declared
to be contrary to the teaching of the Church, he printed
a conciliatory explanation, but never cancelled the
passages objected to, which continued to appear in a
succession of editions. His deficiencies, we must admit,
were serious. He was a poor observer (partly because
of short sight), and had no memory for small details.
His enemies were able to taunt him with absurd mistakes,
such as that cows shed their horns. He alienated the
two foremost naturalists of the eighteenth century,
Linnaeus and Reaumur, by ignorant and scornful
criticisms. His strong propensity to speculation, in-
sufficiently checked by care to verify, might have
brought him under the sarcastic remark of Fontenelle,
that ignorance is less apparent when it fails to explain
'what is, than when it undertakes to explain what is not.

Buffon's fame is not seriously impaired by the fact
that his great work is no long-er read except by those
who study the course of scientific thought. Few
productions of the human intellect retain their value
after a hundred years, and scientific treatises become
obsolete sooner than others. It is consoling- to
recollect that, if their energy is quickly dissipated, it is
at least converted into light.

In a history of biology Buffon is naturally a more
important figure than Montesquieu. Buffon had im-
bibed evolutionary views from the Protogcea of Leibnitz,
which in turn made use of certain hypotheses of

HISTORICAL OR COMPARATIVE METHOD 65

Descartes.1 The Histoire Naturelle inclines to some
theory of evolution, especially in the later volumes. At
first Buffon teaches that species are fixed and wholly
independent of one another ; some years later he is ready
to believe that all quadrupeds may be derived from some
forty original forms, while in a third and subsequent

GEORGES Louis LECLERC, COMTE DE BUFFON.

passage he puts the question whether all vertebrates
may not have had a common ancestor. He does not
shrink from saying- that one general plan of structure

1 For an account of other early hypotheses of the same kind
the reader may refer to Edward Clodd's Pioneers of Evolution.

66 PERIOD III.

pervades the whole animal kingdom — a belief that he
could never have adequately supported by facts ; Baer
long1 afterwards (1828) searched in vain for evidence on
this very point, while Darwin in 1859 admitted that his
arguments and facts only proved common descent for
each separate phylum of the animal kingdom ;x he
inferred from analogy that probably all the organic
beings which have ever lived on this earth have
descended from some one primordial form.2 Elsewhere
Buffon makes bold to declare that Nature in her youthful
vigour threw off a number of experimental forms of life,
some of which were approved and adopted, while others
were allowed to survive in order to give mankind a wider
conception of her projects. There is generally some
gleam of truth in Buffon's most fantastic speculations, but
we often wish that he could have attended to the warning
of Bossuet : " Le plus grand dereglement de 1'esprit est
de croire les choses parce qu'on veut qu'elles soient."

Against all his shortcomings we must set the fact
that Buffon strove to interpret the present by the
past, the past by the present, geology by astronomy,
geographical distribution by the physical history of the
continents. One of his maxims expresses the funda-
mental thought of Ly ell's Principles of Geology : "Pour
juger de ce qui est arrive, et meme de ce qui arrivera,
nous n'avons qu'a examiner ce qui arrive."

Hard-and-fast distinctions are the marks of imperfect
theory. Early philosophers distinguished hot and cold,
wet and dry, light and dark, male and female, as things
different in kind. In later times organic and inorganic,
animal and vegetable, the activities of matter and the
activities of mind, have been sharply separated. But as

1 Life and Letters, Vol. II., p. 212.

2 Origin of Species, cd. i., p. 484.

AMATEUR STUDENTS OF LIVING ANIMALS 67

knowledge increases these distinctions melt away ; it is
perceived that the extreme cases are either now connected
by insensible gradations, or else spring historically from
a common root. Hutton, Lyell, and their successors
have made it clear that the history of the earth calls for
no agents and no assumptions beyond those that are
involved in changes now going on ; the present is heir
by unbroken descent to the past. Continuity has been
established between all forms of energy. Even the
chemical elements, once the emblems of independence,
give indications that they too had a common origin.
The nebular hypothesis, which has been steadily rendered
more probable by the scientific discoveries of two cen-
turies, traces all that can be perceived by the senses to
a homogeneous vapour, and lays the burden of proof on
those who believe that continuity has its limits. Every
history, whether of planetary systems, or of the earth's
crust, or of human civilisations, religions, and arts, is
recognised as a continuous development with progressive
differentiation.

Amateur Students of Living Animals.
A history of biology would be incomplete which
took no notice of every-day observations of the com-
monest forms of life. Some of the best are due to the
curiosity of men with whom natural history was no
more than an occasional recreation. William Turner
(a preacher, who became Dean of Wells), Charles
Butler (a schoolmaster), Caius and Lister (physicians),
Claude Perrault (a physician and architect), Mery and
Poupart (surgeons), Frisch (a schoolmaster and philo-
logue), Lyonet(an interpreter and confidential secretary),
Roesel (a miniature painter), Henry Baker (a bookseller,
who gained a competence by instructing deaf mutes),

63 PERIOD III.

Leroy (ranger to the King- of France), Stephen Hales,
Gilbert White and William Kirby (country parsons),
and William Spence (a drysalter) were all amateurs in
natural history. To this list we might add Willughby,
Ray, Leeuwenhoek, Reaumur, De Geer, Buffon, the
Hubers, and George Montagu, who were either so
fortunate in their worldly circumstances or so devoted
to science as to make it their chief, or even their sole
pursuit, though they did not look to it for bread. A
large proportion of the naturalists whose names have
been quoted occupied themselves with the habits and
instincts of animals, and biology has been notably
enriched by their observations. To Englishmen the
most familiar name is that of Gilbert White, in whom
were combined thirst for knowledge, exactness in
description, and a feeling for the poetry of nature.

White used his influence to encourage what may be
called live natural history, which, as he understood it,
"abounds in anecdote1 and circumstance." He bids
his correspondents to " learn as much as possible the
manners of animals ; they are worth a ream of des-
criptions." His example has done more than his
exhortations. He focusses a keen eye upon any new
or little-known animal, such as the noctule, the harvest-
mouse, or the mole-cricket ; detects natural contrivances
little, if at all, noticed before, such as the protective
resemblance of the stone-curlew's young ; dwells upon
the practical applications of natural history, such as the
action of earthworms in promoting the fertility of soils;
and combines facts which a dull man would be careful
to put into separate pigeon-holes, such as the different

1 White uses anecdote in the old sense, meaning- by it a piece of
unpublished information.

INTELLIGENCE, ETC., IN LOWER ANIMALS 69

ways in which a squirrel, a field-mouse, and a nuthatch
extract the kernels of hazel-nuts.

The many amateurs of the eighteenth century natu-
rally demanded books written to suit them, and
illustrated books with coloured plates, coming out in
parts, found a ready sale. Some were devoted to
insects, others to microscopic objects. In accordance
with prevalent belief, the writers made a point of
tracing the hand of Providence in the minutest organ-
isms ; many popular treatises were altogether devoted
to natural theology. Some few of these natural history
miscellanies contained original work, which has not yet
lost its interest. The best is Roesel's Insecten-belusti-
gungen (four vols. 4to., 1746-61), memorable among
other things for containing the original description of
Amoeba. For English readers Henry Baker wrote The
Microscope Made Easy (1743) and Employment for the
Microscope (1753).

Intelligence and Instinct in the Lower Animals.

The period with which we are now concerned (1741-
1789) initiated the profitable discussion of the mental
powers of animals. We are unable for lack of space
to follow the investigation from period to period, and
must condense into one short section whatever its
history suggests.

In the year 1660 Aristotelians were still discoursing
about the vegetative and sensitive souls which bridged
the gulf between inanimate matter and the thinking
man. Descartes had tried to prove that the bodies
of men and animals are machines actuated by springs
like watches. Man, however, according to Descartes,
possesses a soul wholly different in its properties from
his body, and apparently incapable of being acted upon

70 PERIOD III.

by it. Man only can think ; animals are capable only
of physical sensations, and have no consciousness.
Into speculations like these we shall not venture, being
content, like Locke, " to sit down in quiet ignorance
of those things which upon examination are proved to
be beyond the reach of our capacities." We shall
merely note here and there facts ascertained by obser-
vation or experiment, and plain inferences drawn from
such facts.

Swammerdam and Reaumur, besides many naturalists
of less eminence, recorded a host of observations on the
activities of insects. They contributed little to the
discussion except new facts, for habit led them to ascribe
without reflection every contrivance to the hand of
Providence or else to Nature. Some of their facts, how-
ever, made a deep impression, none more than the exact
agreement of the cells of the honeycomb with the form
which calculation showed to be most advantageous.1
The coincidence has lost some of its interest since the
discovery that the theoretically best form of cell is hardly
ever realised.2 R£aumur,3 in describing the process by
which a certain leaf-eating caterpillar makes a case for
itself out of the epidermis of an elm-leaf, showed that
the caterpillar is not devoid of that kind of intelligence
which adapts measures to circumstances. He cut off
the margin where the upper epidermis of the leaf passes
into the lower one, a margin which the insect had
intended to convert into one side of its case ; the cater-
pillar sewed up the gap. He cut off a projection which
was meant to form part of the triangular end of the
case ; the caterpillar altered its plan, and made that the
head-end which was originally intended to lodge the

1 Reaumur, Hist, des Insectes, Vol. V., M£m. viii.
9 Darwin, Origin of Species, chap. vii. 3 Vol. III., M£m. iv.

INTELLIGENCE, ETC., IN LOWER ANIMALS 71

tail. This observation anticipates a better-known
example taken from the economy of the hive-bee by
Pierre Huber, which is mentioned below.

Buffon1 heard with impatience all expressions of
admiration for the works of insects. His poor eyesight
and his repugnance to minutiae disinclined him to pay
much attention to creatures so small, and he had set
himself up as the rival of Reaumur in physics and
natural history. To pour contempt upon insects grati-
fied both feelings at once. Bees, he said, show no
intelligence at all ; their actions are purely automatic,
and their much-vaunted architecture is merely the result
of working in a crowd. The cells of the honeycomb are
hexagonal, not by reason of forethought or contrivance,
but because of mutual pressure ; soaked peas in a con-
fined space form hexagonal surfaces wherever they touch.

The elder Huber seems to have denied to bees every
trace of intelligence, but his son Pierre found it hard
to go so far.2 He remarked that the storage-cells
of a honeycomb are not always exactly alike ; they may
be lengthened, cut down, or curved, when requisite.
Cells which had been rudely trimmed with a knife were
repaired with such dexterity and concert as to suggest
that even the hive-bee has " le droit de penser." Bees
would under compulsion build upwards or sideways,
instead of downwards, as they like to do. Finding that
they sought to extend their combs in the direction of
the nearest support, he covered the support with a sheet
of glass, on which they could get no footing. They
swerved at once from the straight line, and prolonged

1 Hist. Nat., Vol. IV.

2 The first edition of the Nouvelles Observations sur les Abeilles
(1792) was the work of Frar^ois Huber alone ; the second (1814)
was prepared by Pierre with the co-operation of his father, and
is here credited to the son.

72 PERIOD III.

their comb towards the nearest uncovered surface,
though this obliged them to distort their cells. He was
driven to the conclusion that bees possess " a little dose
of judgment or reason." In our own time, when all
conscious adaptation of means to ends is believed to
be worthy of the name of reason, it requires no great
courage to ask why we deny such an attribute to all the
lower animals.

In spite of examples like this, the favourite expression
" blind instinct " helped to strengthen the conviction
that the mental processes of animals are unsearchable.
It is impossible to deny that the epithet blind is appro-
priate in many cases. A bird will sit an addled egg all
summer, or vainly but repeatedly attempt to make its
tunnel in the insufficient breadth of a mud wall (Geo-
sitta). Of course such instances do not show that all
the acts of the lower animals are devoid of intelligence.

Hume in 1739 and again in 1748 appealed to every-
day observation of dogs, birds, and other animals of
high grade. The facts seemed to him to show that
animals as well as men are endowed with reason and
able to draw inferences ; he did not, however, credit
them with the power of framing general statements,
holding that experience operates on them, as on children
and the generality of mankind, by " custom " alone. It
is notorious that the dog and other higher animals learn
by experience ; Hume tells, for instance, how an old
greyhound will leave the more fatiguing part of the
chase to younger dogs, and place himself so as to meet
the hare in her doubles. On the other hand (though
Hume does not say so) man himself possesses non-
educable instincts. In short, Hume sees no ground for
drawing a line between the mental powers of man and
those of the higher animals, though he attributes to

INTELLIGENCE, ETC., IN LOWER ANIMALS 73

man a power of demonstrative reasoning1 to which
animals do not attain. In this he substantially agrees
•with Aristotle,1 who maintained that in animals the
germs of the psychical qualities of the man are evident,
though, as in the child, they are undeveloped. Hume's
teaching- also accords with modern views ; comparative
anatomy, for instance, " is easily able to show that,
physically, man is but the last term of a long1 series of
forms, which lead by slow gradations from the highest
mammal to the almost formless speck of living proto-
plasm, which lies on the shadowy boundary between
•animal and vegetable life."2

The detailed proofs which Hume was not enough of
a naturalist to furnish were at length stated with admir-
able clearness and force by Leroy, whose Letters on
Animals form the most important contribution made
to the discussion during our period. Georges Leroy
(1723-1789) was lieutenant des chasses under the last
French kings, and had charge of the parks at Versailles
and Marly. He wrote therefore with knowledge about
the wolf, fox, deer, rabbit, and dog. His pages are
•enlivened by many touches of nature, interesting to
readers who perhaps care little about psychology.
Leroy attributes to the wolf observation, comparison,
judgment. The wolf must mark the height of the fold
which encloses a flock, and judge whether he can clear
it with a sheep in his mouth. Wolf and she-wolf co-
operate artfully in the running-down of prey. Some-
times the she-wolf will draw off the sheep-dog in pursuit,
thus putting the flock at the mercy of her mate. Or one

T Hist. Animalium^ VIII. , i.

8 Huxley's Hume^ chap. v. Some few naturalists, who are
entitled to respectful attention, such as Father Wasmann, author
of The Psychology of Ants , do not even now receive the conclusions
of Hume.

74 PERIOD III.

of the two will chase the quarry till it is out of breath,
when the other can take up the running on advantageous
terms. An old fox shows knowledge of the properties
of traps, and will rather make a new outlet or suffer
long famine than encounter them. But when he finds
a rabbit already caught, he realises that the trap has
lost its power to hurt. Sheep-dogs can be educated to
mind things which do not interest wild dogs, or dogs of
other breeds ; when, for instance, the flock is driven
past a patch of wheat, the dog in charge will take care
that the sheep do not damage the crop. A trained
sporting-dog learns at length to trust his own judgment,
even in opposition to that of his master, and sportsmen
know that they must direct young dogs, but leave old
ones to act for themselves.

From the middle of the eighteenth century to the
present day naturalists and psychologists have been
labouring to distinguish instinct from intelligence. It
is not hard to define well-marked examples of each, and
to show that a typical instinct is congenital (not the
result of a process of education or self-education),
adaptive (conducive to the welfare of the organism),
co-ordinated by nerve-centres (thus excluding the
superficially similar behaviour of the lowest animals and
all plants), actuating the 'whole organism (thus excluding
most, if not all, reflex acts in the higher animals, as
well as the wonderful adjustments effected by bone-
corpuscles and other parts of organisms), and common
to all the members of a species or other group (thus
excluding individual aptitudes).1 In the same way it
is easy to point out clear differences between a bird and
a tree. But just as a definition which shall separate

1 Lloyd Morgan. Habit and Instinct, Introduction.

INTELLIGENCE, ETC., IN LOWER ANIMALS 75

every animal from every plant has hitherto been sought
in vain, so it has hitherto been impossible to frame a
definition which while including all instincts shall admit
no case of reflex action or intelligence. The most
ambiguous cases of all are perhaps to be found in
insects, where, as will shortly be explained, our infor-
mation is ill-fitted to support precise distinctions.

Many naturalists entertain some form of what may
be called the usi-and-disuse or inherited-memory theory,
supposing that the aptitudes of the offspring are
influenced by the activities of the parent. Some cling
to the belief that habits can be fixed and transmitted,
and we must admit that the fixation and transmission
of habits might explain a great deal. But all the
evidence goes to prove that habits are not inherited at
all, and that we must look elsewhere for the origin of
instincts. Let naturalists who think differently try to
account for the instincts of working bees or ants, which
receive their psychical not less than their physical
endowment from a long succession of ancestors, none
of which worked for their living. Or let them try to
explain the instances of spiders, insects, etc., which
after egg-laying practise instinctive arts for the defence
of their brood, standing over the eggs, carrying them
about, blocking the entrance of the burrow, etc. May
we not say that it is impossible for the acts of a parent
to influence the congenital instincts of offspring which
have already lost connection with the mother ? But
surely a theory of instinct breaks down which fails to
account for the expedients by which the worker-bee,
the worker-ant, and the spider provide for the safety
of the unhatched brood or for the welfare of the
community.

Darwin's Origin of Species threw a new light upon

F 2

76 PERIOD III.

instinct by showing that natural selection can operate
on the subtlest modifications. It can discriminate
shades of hardiness to climate, shades of intellectual
acuteness, or shades of courage. It can intensify
qualities which appear only in adults past bearing or
in individuals congenitally incapable of propagation.
Human selection, though a blunt tool in comparison
with natural selection, can originate a bold and hardy
race of dogs, or showy double flowers incapable of pro-
ducing seed. In the second case fertile single flowers
continue the race, as in the garden Stock. Darwin
pointed out that the barren double flowers of the Stock
answer to the workers of social bees and ants, the
fertile single flowers to the functional males and females.
Every modification that works to the advantage or dis-
advantage of the race, whether we classify it as physical,
intellectual, or moral, gives scope for the operation of
natural selection.

The comparative psychology of small invertebrates,
such as insects, is impeded by our imperfect knowledge
of their nervous physiology. Introspection is here
impossible; experimental physiology and pathology,
which have done so much for the psychology of the
higher vertebrates, almost impossible ; analogy is a
treacherous guide where the structures involved differ
conspicuously. We have little to guide us in the
psychology of insects except their behaviour, and that
is often capable of a variety of interpretations. The
only course is to adopt Pasteur's watchword, "Travail-
Ions ! " — the difficulties will diminish with time and
labour.

The Food of Green Plants.

Common observation taught men in very early times
that green plants draw nourishment from the soil, and

THE FOOD OF GREEN PLANTS 77

that sunlight is necessary to their health. In the age
of Galileo a Belgian physician and chemist, Van
Helmont, endeavoured to pursue the subject by experi-
ment. He planted the stem of a live willow in furnace-
dried earth, which was enclosed in an earthen vessel.
Rain-water or distilled water was supplied when neces-
sary, and dust excluded by a perforated lid. The loss
of weight due to the falling-off of leaves was neglected.
In the course of five years the tree was found to have
increased to more than thirty times its original weight ;
Van Helmont concluded that this increase was due to
water only. Malpighi (1671), being guided mainly by
his microscopic studies of the anatomy of the stem and
leaf, taught that moisture absorbed by the roots ascends
by the wood, becoming (apparently at the same time)
aerated by the large, air-conducting vessels ; that it
enters the leaves, and is there elaborated by evapora-
tion, the action of the sun's rays, and a process of
fermentation ; lastly, that the elaborated sap passes
from the leaves in all directions towards the growing
parts. It will be seen that this explanation, though
incomplete, makes a fair approximation to the beliefs
now held ; for more than a hundred years after
Malpighi's day less instructed opinions were commonly
held. Hales (1727) recognised that green plants are
largely nourished at the expense of the atmosphere ;
he dwelt also on the action of the leaves in drawing
water from the soil, and in discharging superfluous
moisture by evaporation.

Joseph Priestley, who had been proving that air is
necessary both to combustion and respiration, made an
experiment in 1771 to discover whether plants affected
air in the same way that animals do. He put a sprig of
mint into a vessel filled with air in which a candle had

78 PERIOD III.

burned out, and after ten days found that a candle would
now burn perfectly well in the same air. Air kept with-
out a plant, in a glass vessel immersed in water, did not
regain its power of supporting combustion. Balm,
groundsel, and spinach were found to answer just as
well as mint. Air vitiated by the respiration of mice
was restored by green plants as readily as air which
had been vitiated by combustion.

Priestley did not remark that the glass vessels
employed in his experiments had been set in a window,
and inattention to this point caused some of his
attempts to repeat the experiment to fail. He was
further perplexed by using vessels which had become
coated with a film of "green matter," probably
Euglaena. Such vessels restored vitiated air, though
no leaves were present, and when placed in the sun,
gave off considerable quantities of a gas, Priestley's
" dephlogisticated air" (oxygen). Hardly any oxygen
was given off when the green matter was screened by
brown paper. Water impregnated with carbonic acid
was found to favour the production of the green matter.
To us, who have been taught at school something about
the properties of green plant-tissues, it seems obvious
that Priestley ought to have ascertained by microscopic
examination whether his " green matter " was not a
living plant. But he had always avoided the use of
the microscope, his eyes being weak, and after some
imperfect attempts in this way he made up his mind
that the green matter was neither animal nor vegetable,
but a thing sui generis. Neglecting his most instructive
experiments, and not waiting till he could devise new
ones, or even disentangle his thoughts, he sent to the
press a confused explanation, which seemed to teach
that vitiated air may be restored by sunlight alone.

THE FOOD OF GREEN PLANTS 79

A Dutch physician, named John Ingenhousz, who was
then living- in England, read Priestley's narrative and
began to investigate on his own account. Without
detailing his numerous experiments, we may give his
own clear summary (condensed). " I observed," Ingen-
housz says, " that plants have a faculty to correct bad
air in a few hours ; that this wonderful operation is due
to the light of the sun ; that it is more or less brisk
according1 to the brightness of the light ; that only the
green parts of the plant can effect the change ; that
leaves pour out the greatest quantity of oxygen from
their under surfaces ; that the sun by itself has no
power to change the composition of air." It will be
seen that Priestley started the inquiry, devised and
executed the most necessary experiments, and got
excellent results. Then he lost his way, and bewil-
dered by conflicting observations, which he was too
impatient to reconcile, published a barren and mis-
leading conclusion. Nothing was left for him but to
acknowledge that Ingenhousz had cleared up all his
perplexities.

Nicholas Theodore de Saussure, son of the Alpine
explorer, showed in 1804 that when carbon is separated
from the carbonic acid of the air by green plants, the
elements of water are also assimilated, a result which
owes its importance to the fact that starch is a combina-
tion of carbon with the elements of water. Saussure
also proved that salts derived from the soil are essential
ingredients of plant-food, and that green plants are
unable to fix the free nitrogen of the air ; all the nitrogen
\vhich they require is obtained from the ground.

We are unable to follow the history further. Though
the main facts were established as early as the begin-
ning of the nineteenth century, experimental results of

So PERIOD III.

scientific and practical interest have never ceased to
accumulate down to the present time.

The Metamorphoses of Plants.

Speculations concerning the nature of the flower
roused at one time an interest far beyond that felt in.
most botanical questions. The literary eminence ot
Goethe, who took a leading- part in the discussion,,
heightened the excitement, and to this day often
prompts the inquiry : What does modern science think
of the Metamorphoses of Plants?

• Let us first briefly notice some anticipations of
Goethe's famous essay. In the last years of the six-
teenth century Cesalpini, taking a hint from Aristotle,,
tried to establish a relation between certain parts of the
flower and the component layers of the stem. Linnaeus-
worked out the same notion more elaborately, and with
a confidence which sought little aid from evidence. His
wonderful theory of Prolepsis (Anticipation) need not be
described, far less discussed, here. He also borrowed
and adapted an analogy which had been thrown out by
Swammerdam. The bark of a tree, which according to-
the theory of Prolepsis gives rise to the calyx of the
flower, he compared to the skin of a caterpillar, the
expansion of the calyx to the casting of the skin, and
the act of flowering to the metamorphosis by which the
caterpillar is converted into a moth or butterfly. More
rational than the speculations just cited, and more
suggestive to the morphologists of the future, are his
words : " Principium florum et foliorum idem est "
(Flower and leaf have a common origin) — which was
not, however, a very novel remark in the eighteenth
century. Long before Linnaeus early botanists had
remarked the resemblance of sepals, petals, and seed-

THE METAMORPHOSES OF PLANTS Si

leaves to foliage-leaves ; Cesalpini has a common name
for all (folium).

At the very time when Linnaeus was occupied with
his fanciful analogies, a young student of medicine
named Caspar Friedrich Wolff, who was destined to
become a biologist of great note, published a thesis
which he called Theoria Generationis (Halle, 1759).
This thesis marks an epoch in the history of animal!
embryology, but what concerns us here is that Wolff
examined the growing shoot, and there studied the
development of leaf and flower. He found that in early
stages foliage-leaves and floral-leaves may be much
alike, and thought that he could trace both to a soft or
even fluid substance, which is afterwards converted into
a mass of cells. It seemed to him possible to resolve
the flowering shoot into stem and leaves only. Wolff's
thesis, or at least that part of it which dealt with the
plant, was little read and soon forgotten ; his studies
of the development of animals were carried further and
became famous.

Goethe in 1790 revived Wolff's theory of the flower,
without suspicion that he had been anticipated. It is
only our ignorance, he said, when the fact came to his
knowledge, that ever deludes us into believing that we
have put forth an original view. As soon as he realised
the true state of the case, he spared no pains to do-
Wolff full justice.

The aim of Goethe's Metamorphoses of Plants was to
determine the Idea or theoretical conception of the plant,
and also to trace the modifications which the Idea
undergoes in nature. These two inquiries constituted
what he called the Morphology of the plant, a useful,
nay, indispensable term, which is still in daily use. He
thought that he could discover in the endless variety of

S2 PERIOD III.

the organs of the flowering- plant one structure repeated
ag-ain and again, which gradually attained, as by the
steps of a ladder, what he called the crowning purpose
of nature — viz., the sexual propagation of the race.
This fundamental structure was the leaf. The proposi-
tion that all the parts of the flower are modifications of
the leaf he defended by three main arguments — viz.,
(i) the structural similarity of seed-leaves, foliage-
leaves, bracts, and floral organs ; (2) the existence of
transitions between leaves of different kinds ; and
(3) the occasional retrogression, as he called it, of
specially modified parts to a more primitive condition.
These lines of argument were illustrated by many well-
chosen examples, the result of long and patient obser-
vation. Goethe did not, however, fortify his position by
the likeness of developing floral organs to developing
foliage-leaves, which had been Wolff's starting-point.
He arrived independently at Wolff's opinion that the
conversion of foliage-leaves into floral organs is due to
diminished nutrition.

Linnaeus's exposition of the nature of the flower had
been read attentively by Goethe, who must have
remarked that the conversion of organs to new uses was
there described as a metamorphosis. That word had
been, long before the time of Linnaeus, appropriated to
a particular kind of change — viz., an apparently sudden
change occurring- in the life-history of one and the same
animal. It was therefore unlucky that Goethe should
have been led by the example of Linnaeus to employ the
word in the general sense of adaptation to new purposes.
He did not, however, expressly compare flower-pro-
duction with the transformation of an insect, as Linnaeus
had done.

The reception of Goethe's Metamorphosen der Pflanzen

THE METAMORPHOSES OF PLANTS 83

was at first cold, but the doctrine which it enforced
gradually won the attention of botanists, and by 1830
he was able to show that it had been accepted by many
good judges.

Then came the discoveries of Hofmeister, followed by
Darwin's Origin of Species. Naturalists soon ceased
to put the old questions, and the old answers did not
satisfy them. Wolff and Goethe had generalised the
flowering plant until it became a series of leaf-bearing
nodes alternating with internodes, but no such abstract
conception could throw light upon the common ancestor
of all the flowering plants, nor upon the stages by which
the flowering plant has been evolved, and it was these
which were now sought. Hofmeister brought to light
a fundamental identity of structure in the reproductive
organs of the flowering plants and the higher cryptogams.
There has since been no doubt in what group of plants
we must seek the ancestor of the flowering plant. It
must have been a cryptogam, not far removed from the
ferns, and furnished with sporophylls — i.e., leaf-like
scales, on which probably two kinds of sporangia, lodging
male and female spores respectively, were borne. The
careful investigation of the fossil plants of the coal
measures has brought us still nearer to the actual pro-
genitor. Oliver and Scott1 have pointed out that the car-
boniferous Lyginodendron, though showing unmistak-
able affinity with the ferns, bore true seeds, as a pine or
a cycad does. Many other plants of the coal measures
are known to have combined characteristics of ferns
with those of cycads, while some of them, like Lygino-
dendron, crossed the frontier, and became, though not
yet flowering plants, at least seed-bearers.

The discovery of a fossil plant which makes so near
1 Phil. Trans., 1904.

84 PERIOD III.

an approach to the cryptogamic ancestor of all the
flowering plants may remind us how little likely it was
that the ideal plant of Wolff and Goethe, consisting- of
leaves, stem, and other vegetative organs, but without
true reproductive org-ans, should fully represent the type
from which the flowering- plants sprang-. No plant so
complex as a fern could maintain itself indefinitely
without provision for the fertilisation of the ovum ; the
only known asexual plants are of low grade, and, it
may be, insufficiently understood.

What substratum of plain truth underlies the doctrine
of the metamorphoses of plants? Botanists would
agree that all sporophylls, however modified, are homo-
log-ous or answerable parts. Carpels and stamens are
no doubt modified sporophylls. Petals are sometimes,
perhaps always, modified stamens, and therefore modified
sporophylls also. We must not call a sporophyll a leaf,
for it contains a sporangium of independent origin, and
the sporangium is the more essential of the two. The
common origin of foliage-leaf, bract, perianth leaf,
sporophyll (apart from the sporangium), and seed-leaf
is unshaken. We may picture to ourselves a plant
clothed with nearly similar leaves, some of which either
bear sporangia or else lodge sporangia in their axils.
Part of such a primitive flowering plant might retain
its vegetative function and become a leafy shoot, while
another part, bearing crowded sporophylls, might yield
male, female, or mixed cones. From an ancestor thus
organised any flowering plant might be derived. But
the chief wonder of the theory of Metamorphoses — viz.,
the derivation of stamen and pistil from mere foliage-
leaves — disappears. Anther and ovule take their real
origin from the sporangium, whose supporting leaf is
only an accessory.

EARLY NOTIONS ABOUT THE LOWER PLANTS 85

The chief steps by which the morphology of the
flowering- plant has been attained are these : — Cesalpini
(1583), followed by several other early botanists, recog-
nised the fundamental identity of foliage-leaf, perianth-
leaf, and seed-leaf. Linnaeus (1759) added stamen and
carpel to the list, identifications of greater interest, but
only partially defensible. Wolff (1759) justified by
similarity of development the recognition of floral organs
as leaves. Goethe (1790) traced structural similarity,
transitions, and retrogression in leaves of diverse
function. Hofmeister (1849-57) showed a relationship
between the flowering plant and the higher cryptogams.
Oliver and Scott (1904), inheriting the results of
Williamson's work, discovered a carboniferous seed-
bearing plant, one of a large group intermediate between
ferns and cycads. It is now possible to explain the
resemblance of the various leaf-like appendages of the
flowering plant by derivation either from the leaves or
the sporophylls (the latter not being wholly leaves) of
some extinct cryptogam, which was either a fern or a
near ally of the ferns.

Early Notions about the Lower Plants.

The fathers of botany neglected everything else in
order to concentrate their attention upon the flowering
plants, from which very nearly all useful vegetable pro-
ducts were derived. The lack of adequate microscopes
rendered it almost impossible to investigate the structure
and life-history of ferns, mosses, fungi, and algae until
the nineteenth century. As late as the time of Linnaeus
it was possible to maintain that they developed spon-
taneously, though the great naturalist himself called
them Cryptogamia, thereby expressing his conviction
that they reproduce their kind like other plants, but in

86 PERIOD III.

a way so far not understood. Gaertner, a contem-
porary of Linnaeus, pointed out one important respect
in which the spores of cryptogams differ from the seeds
of flowering plants, viz. that they contain no embryo.

Ferns. — Even before the age of Linnaeus it was known
that little ferns spring up around the old ones, and that
a fine dust can be shaken from the brown patches on
the back of ripe fern-leaves. The dust was reputed to
be the seed of the fern, and in an age which believed in
magic the invisibility of fern-seed made it easy to suppose
that the possessor of fern-seed would become invisible
also. When the microscope began to be applied to
minute natural objects, the brown patches of the fern-
leaf were closely examined. William Cole of Bristol
(1669), Malpighi, Grew, Swammerdam, Leeuwenhoek,
and others, found the stalked capsules (sporangia), their
elastic ring and the minute bodies (spores) lodged within
them ; it seemed obvious to call the capsules ovaries and
the spores seeds. Some time in the latter part of the
seventeenth century Robert Morison, professor of botany
at Oxford, who died in 1683, sowed spores of the
harts-tongue fern, and next year got an abundant crop
of prothalli, which he took to be the cotyledons. A little
later, when it had been proved that flowering plants
possess male and female organs, diligent search was
made for the stamens and pistils of ferns and mosses,
which of course could not be found, though identifica-
tions, sometimes based upon a real analogy, were con-
tinually announced. Late in the eighteenth century one
John Lindsay, a surgeon in Jamaica, who was blest with
leisure and a good microscope, repeated the experiment
of Morison, which seems to have been almost forgotten.
Having remarked that after the rains young ferns sprang
up in shady places where the earth had been disturbed*

EARLY NOTIONS ABOUT THE LOWER PLANTS 87

it occurred to him to mix the fine brown dust from the
back of a fern-leaf with mould, sow the mixture in a
flower-pot, and watch daily to see what might come up.
About the twelfth day small green protrusions were
observed, which enlarged, sent down roots, and formed
bilobed scales, out of which young ferns ultimately grew.
In 1789 Sir Joseph Banks, who was reputed to be the
best English botanist of the day, asked Lindsay's help
in sending West- Indian ferns to Europe. Lindsay
replied that it would be easier to send the seed, and
that the seed would grow if properly planted. This was
new to Banks, who demanded further information.
Lindsay then prepared a short illustrated paper, which
Banks communicated to the newly formed Linnean
Society. It will be seen that Lindsay was able to add
nothing of much importance to what Morison had
ascertained a century before. The spores were still
identified with seeds, the prothallus was still a coty-
ledon, and for years to come botanists continued to
seek anthers on fern-leaves. At this point we suspend
for a time the history of the discovery (see below, p. 108).
Mosses. — Linnaeus observed that the large moorland
hair-moss (Polytrichum) is of two forms, only one of
which bears capsules, and further that in dry weather
the capsules emit masses of fine dust. No further
progress was made until 1782, when Hedwig, in a
memoir of real merit, described the antheridium and
archegonium of the moss, and traced the capsule to-
the archegonium. Interpreting the organs of the moss
by those of the flowering plant, he called the antheridia
anthers, the capsule was a seed-vessel, the spores were
seeds, and the green filament emitted by the germinat-
ing spore a cotyledon. Such misinterpretations were
then inevitable.

SS PERIOD III.

Fungi. — Micheli in 1729 found the spores of several
fungi, germinated them, and figured the product. The
figures show the much-branched filament (mycelium)
which burrows in the soil and constitutes the vegetative
part of the fungus, and also here and there a pileus
{mushroom, toadstool, &c.), which is the fructification
springing out of the mycelium. His account comprises
the best part of what is known down to the present
time of the reproduction of that group of fungi to which
the mushroom belongs.

Algae. — Some early observers (Reaumur among the
rest) studied the enlarged and fleshy branches of brown
seaweeds, and discovered the seed-like spores.

This scanty knowledge of the life-history of cryp-
togams sufficed until the nineteenth century, when the
study was resumed with better microscopes and in a
far more connected way, with results of the highest
interest and importance (see below, p. 108).

PERIOD IV.
1790-1858

Characteristics of the Period.

THE first French republic and the first French empire
were associated with a great outburst of scientific
energy. French mathematics, astronomy, and physics
were pre-eminent. England suffered from isolation
during the continental war, but Davy, Young, the
Herschels, Watt (now past his prime), Dalton, and
William Smith supported the scientific reputation of
their country. In Germany this was the age of Goethe
and Schiller ; Alexander von Humboldt was prominent
among the scientific men of Prussia. The forty years'
peace, during which reaction prevailed in many parts
of Europe, was in England and America a time of
steady growth and progress.

Sprengel and the Fertilisation of Flowers.

Conrad Sprengel, an unsuccessful schoolmaster who
lived in a Berlin attic and got his bread by teaching
languages or whatever else his pupils wished to learn,
wrote a book which marks an epoch in the study of
adaptations. This was his Secret of Nature Discovered,
which appeared in 1793. Half a century passed before
its merit was recognised by any influential naturalist ;
even then the recognition was private, and never
reached the author, who had died long before. There
was no striking of medals, no jubilee-celebration,

89

90 PERIOD IV.

nothing1 more than this, that Robert Brown recom-
mended the book to Charles Darwin, who found in it,
as he says, "an immense body of truth."

In 1787 Sprengel had remarked that the bases of the
petals of Geranium silvaticum are beset with long- hairs.
Persuaded that no natural structure can be devoid of
meaning, Sprengel asked what purpose these hairs
might serve. A honey-gland in their midst suggested
that they might protect the honey by keeping off the rain,
which easily enters this shallow flower. Other honey-
secreting flowers were found to possess mechanisms
adapted to the same end. His first question suggested
a second : Why should flowers secrete honey?

Malpighi had described the honey-glands of crown-
imperial (1672), and had seen that the honey must be
secreted by the petals, and not deposited from the
atmosphere, according to the notion then current.
Kolreuter (1761) had showed that insects may effect
the pollination of flowers. Linnaeus (1762) had given
the name of nectary to the honey-gland. He thought
that the honey served to moisten the ovary, though he
knew of staminate flowers furnished with nectaries.
He also threw out the alternative conjecture that the
honey is food for insects, which disperse the pollen by
their wings. Sprengel improved upon all his prede-
cessors, and made it clear that transference of pollen is
the main purpose of the honey in flowers. He was put
on the right track by the study of a forget-me-not
flower. Here he found the honey protected from rain
by the narrowness of the corolla-tube, whose entrance
was almost closed by internal protuberances. The
protuberances were distinguished by their yellow colour
from the sky-blue corolla, and this conspicuous coloura-
tion led Sprengel to infer that insects might be thereby

SPRENGEL AND FERTILISATION OF FLOWERS 91

induced to seek for the store of honey within. He
tested his conjecture by examining other honey-bearing
flowers, and soon collected many instances of spots,
lines, folds, and ridges, which might not only make
insects aware of hidden stores of honey, but guide them
to the exact place. Contrivances of the most diverse
kinds, but all tending to invite the visits of insects and
utilise them for the benefit of the plant, rewarded
Sprengel's continued inquiries. He found that night-
flowering plants, which could derive no advantage
from coloured patterns, often have large white corollas,
easily discerned in a faint light, and that these flowers
give out an odour attractive to nocturnal insects. He
found that the pollen-masses of an orchis are actually
removed by large insects, though here no honey could
be detected in the flower. Sprengel's fertility in
probable conjecture is shown by his explanation of this
puzzling case ; he suggested that the orchis is a sham
honey-bearer (Scheinsaftblume), which attracts insects
by assuming the conspicuous size and coloration found
in most honied flowers. Darwin suspected, and
Herman Miiller proved, that though the spur of the
orchis-flower is empty, it yields when pierced a fluid
attractive to bees and other insects. Sprengel dis-
covered too how insects get imprisoned in the corolla
of an Aristolochia, whose reflexed hairs allow small
flies to creep in, but effectually prevent their escape
until they have fertilised the pistils, when the hairs
relax. These are only specimens of a multitude of
adaptations which fill the book.

Sprengel insists upon the study of flowers under
natural conditions ; he could never have made out by
the examination of plucked flowers how Nigella is
fertilised. Flies with attached pollen-masses, which he

G 2

92 PERIOD IV.

found in spiders' nests, gave him the hint as to the way
in which the fertilisation of orchids is effected. Definite
questions must be put if observation is to be profitable.
What is the use of honey to the plant — of this coloured
spot — of these hairs ? He notes the peculiarities of
wind-fertilised and insect-fertilised flowers, the relative
abundance of the pollen, the form of the stigma, the
presence or absence of honey, the size, colour, and
scent of the corolla. Here is a pretty illustration from
his pages. Pluck a branch of hazel, aspen, or alder,
with unexpanded catkins, and also one from the male
sallow ; place them in water, and keep them in a sunny
window until the anthers are ripe. A vigorous puff
will then discharge a cloud of pollen from the wind-
fertilised catkins, but none from the insect-fertilised
catkin of the sallow. What Linnaeus said about the
flowers of trees appearing before the leaves, in order
that the pollen may more easily reach the stigmas,
holds good, Sprengel remarks, only of wind-fertilised
trees. The lime, which is insect-fertilised, flowers in
the height of summer, when all the branches are
crowded with leaves.

Sprengel left it to later biologists to complete his
discovery. " That wonderfully accurate observer,
Sprengel," says Darwin,1 "who first showed how im-
portant a part insects play in the fertilisation of flowers,
called his book The Secret of Nature Displayed; yet he
only occasionally saw that the object for which so many
curious and beautiful adaptations have been acquired,
was the cross-fertilisation of distinct plants ; and he
knew nothing of the benefits which the offspring thus
receive in growth, vigour, and fertility." Not even

1 Cross and Self-Fertilisation of Plants, chap. xi.

CUVIER AND THE RISE OF PALAEONTOLOGY 93

Darwin could exhaust the inquiry. "The veil of
secrecy," he goes on, "is as yet far from lifted."

Cuvier and the Rise of Palaeontology.

If this historical sketch had been prepared within a
few years of the death of Cuvier, it would no doubt
have held him up as the greatest of zoologists and
comparative anatomists. Nor would it have been hard
to find reasons for such a verdict. His Regne Animal
extended and corrected the zoological system of
Linnaeus ; his comparative anatomy, and especially his
comparative osteology, were far ampler and more
exact than anything that had been attempted before.
It would not have been forgotten, moreover, that he
was the practical founder of the new science of palaeon-
tology.

At a later time, say in the sixties and seventies of
the nineteenth century, when the Origin of Species
controversy was in full blast, any estimate of Cuvier
by an evolutionist would have been much less laudatory.
Cuvier had actively opposed that form of evolution
which had been brought forward in his day, and with
such power as to close the discussion for a time. The
assailants of the Origin of Species found his refutation
of unity of type and progressive development adaptable
to the new situation, and the reasoning which had
pulverised Geoffrey St. Hilaire was brought out again
in order to pulverise Darwin. Then the supporters of
Darwin found it necessary to show that Cuvier was by
no means infallible. This they were able to do without
introducing matter foreign to the main question, for
Cuvier's exposition of fixity of species, of the principles
of classification and of the process of extinction, were
entirely opposed to the beliefs not only of Darwin, but

94 PERIOD IV.

of Lyell and the whole school which stood out for
historical continuity, treated history of every kind as a
process of development, extended almost without limit
the duration of life on the earth, and enforced the
obvious but neglected truth that results of any
magnitude whatever may proceed from small causes
operating through a sufficient length of time.

Darwin's main contentions are now accepted by the
scientific world, and Cuvier's hostility to particular
forms of evolution has become a mere historical episode
of no lasting importance. Angry disputes concerning
the weight of his authority are at an end ; he is not to
be blamed because thirty years after his death he was
set up as judge of a cause which he had not heard.
We are now ready to make fair allowance for the time
in which his lot was cast — an age when geology,
embryology, palaeontology, and distribution were mere
infants, some of them hardly yet born. We can also
admit without reserve the incompetence of certain of
Cuvier's antagonists, and justify the severity with which
he treated unity of type as stated and defended by
Geoffrey St. Hilaire. Now that the dust of controversy
has settled, we are chiefly concerned to inquire : What
of all Cuvier's work has proved to be really permanent?
His zoology and his comparative anatomy have had to
be completely re-cast, partly because of the new light
thrown on them by embryology and the doctrine of
descent with modification. His studies of extinct
vertebrates, however, called into existence a new
science, the science of Palaeontology,1 and it is mainly

1 Cuvier did not himself use the word paleontology, which first
came in about 1830. In the same way Button writes on the
history of animals, not on zoology, and on the theory of the earth,
not on geology.

CUV1ER AND THE RISE OF PALAEONTOLOGY 95

this which gives him a lasting and honoured place in
the history of biology.

At the end of the eighteenth century it had been
rather grudgingly admitted that some few animals were
actually extinct. Buffon was able to quote as indu-
bitable examples the mammoth and the mastodon.
Their occurrence in countries unknown to the ancients,
such as Siberia and North America, disposed of the
explanation long clung to by the learned — viz., that their
bones were the remains of elephants which had been
led about by the Roman armies, while their large size
and the ease with which they can be recognised rendered
it highly improbable that they still survived anywhere
on the surface of the globe.

It was therefore natural that Cuvier's first study in
palaeontology should relate to extinct elephants. He
compared and distinguished several species, showed
that they were distinct from the existing Asiatic and
African species, a fact which had escaped the notice of
Pallas, and argued from the well-known case of a
Siberian mammoth preserved in ice and frozen mud
with hardly any decomposition that it must have been
overwhelmed by a sudden "revolution of the earth."
Whatever we may think of Cuvier's geology, his com-
parisons of all known elephants, recent and fossil, intro-
duced a new standard of exactness into these inquiries.
From this beginning he went on to study all the extinct
vertebrates which he could discover in public or private
collections. By 1821 he had published elaborate and
well-illustrated descriptions of near a hundred extinct
animals, an extraordinary output for one investigator.

The most remarkable of his palaeontological dis-
coveries were made at home, in the lower tertiary rocks
which underlie the city of Paris. He proved that in

96 PERIOD IV.

the valley of the Seine a large population of animals, all
now extinct, had formerly flourished. None of these
discoveries impressed his contemporaries more than the
celebrated case of the fossil opossum. The bones were
imbedded in a slab of gypsum, and were at first imper-
fectly exposed. The lower jaw, however, exhibited
a peculiarity of marsupial or pouched animals, for its
angle had an inwardly projecting shelf, not found in
other quadrupeds. The opossums, like all marsupial
animals, bear on the front of the pelvis two long bones,,
which support the pouch. These were as yet concealed,
and Cuvier delayed clearing them until he had sum-
moned friends, some of whom may have been sceptical
about the possibility of reasoning with certainty from
anatomical data. Warning them what to expect, he
removed with a sharp tool the film of stone, and
revealed the long and slender marsupial bones.1 The
ancient existence of marsupials in France was then a
striking and almost incredible fact ; increase of know-
ledge has not lessened its interest, though it has abated
some of the wonder.

The fossil ungulates (hoofed quadrupeds) of the Paris
basin taxed Cuvier's patience and skill to the utmost.
In the tiresome work of piecing together a multitude
of imperfect skeletons he set an example to all future
palaeontologists. That he drew general conclusions
which we are unable to accept, and failed to draw con-
clusions which seem obvious to us, will surprise nobody
whose reading has taught him how unprepared were
the biologists of that age to handle great questions
concerning the origin and extinction of races. Cuvier
recognised among the fossils of the Paris quarries the

1 This anecdote has also been related in a rather different
form.

CUVIER AND THE RISE OF PALEONTOLOGY 97

bones of two genera of ungulates very different from
any of recent times. One resembled the rhinoceros,
tapir, and horse in being odd-toed ; this he called
Palaeotherium. Another had the hind-foot even-toed,
like a ruminant, though the fore-foot, with which he
was imperfectly acquainted, showed points of resem-
blance to the other group. How cautiously he did his
work may be gathered from the fact that he spent
fifteen years upon the collection of facts before he
attempted to restore these extinct forms, though almost
every bone in their bodies had during that time passed
through his hands.

The great interest of these fossil ungulates to the
modern biologist is that they are relatively primitive
types of the order. Palaeotherium is not far from the
ideal common ancestor of the rhinoceros, tapir, and
horse ; Anoplotherium not altogether unlike the ideal
common ancestor of the hippopotamus, the swine, and
the ruminants. It has been suspected that Cuvier was
less obstinately devoted to the tenet of fixity of species
than he was willing to admit in public. Whatever his
private leanings may have been, he stood out resolutely
for cogent proofs of transmutation. When it was con-
tended that the Palaeothere might have been the remote
ancestor of existing ungulates, he demanded that the
intermediate links should be produced. His demand
could not be met till many years later, though inter-'
mediate forms between the Palaeothere and .the horse'
have since been furnished in abundance. Reserve about
far-reaching deductions was surely wise at a time when
plausible speculation was rife, and we ought not to
judge Cuvier severely for having aspired to a rigour unat-
tainable in a natural science, and certainly not always
observed by himself. He hoped to see biology become

98 PERIOD IV.

as exact as astronomy. The hope may have been
chimerical, but emphasis on this side was not altogether
out of place in the generation of Geoffrey St. Hilaire
and Oken.

If the great master who laid the foundations of palae-
ontology could revisit the scene of his former labours,
he would find that many strange things had happened
since the appearance of his Ossemens Fossiles. He would
perhaps be stupefied at first to discover how little is
now made of the Revolutions of the Earth, the proofs
of which had seemed to htm unimpeachable, while the
conjectures about the development of new races, which
in his own day had been almost negligible, have proved
to be anticipatory of fundamental biological truths.
The first shock over, one can imagine the zest with
which he would strive to combine the familiar facts
into a body of new doctrine. The ungulates, recent
and fossil, would of course interest him particularly.
He would recognise the gradations of structure which
run through the whole order, branching and crossing
in all directions; gradation in the number of the
toes, in the rearing of the body more and more upon
the toe-tips, in the progressive complication of the teeth.
One chain of examples would lead from the shallow,
tuberculate molar of the pig to the molar of the horse
or ruminant, deep and massive, with crescentic enamel-
folds ; another would illustrate the gradual development
of tusks from ordinary incisors or canines ; a third
series would show the steps by which the primitive
ungulate dentition became reduced to the dentition of
the elephant, with only a single pair of incisors, enlarged
into tusks several feet long, with no canines but molars
of great weight, complicated by extreme folding. It
would surprise and delight him to compare the almost

GEORGES CUVIER.

From an engraved copy of the portrait by Pickersgill.

ioo PERIOD IV.

insensible steps by which his own Palaeothere can be
seen to pass into the modern horse. Then we can
imagine how our regenerate Cuvier would draw nearer
and nearer to the common ancestor of the whole group,
a five-toed, plantigrade ungulate, with the full dentition
of forty-four unspecialised teeth, and how readily he
would admit that Phenacodus, both in its structure and
its geological horizon, was just the common ancestor
that theory required. The proofs of intermediate stages
between ancient and modern ungulates which he had
once called for in vain, he would now find ready to his
hand. It might well seem that the history of the
ungulates, with all its modern expansions, would suffice
to occupy even his unparalleled energy. He would see
with delight how the palaeontology which he had been
the first to treat as a science has enlarged the compara-
tive anatomy of which also he was so great"- a master.
He would cheerfully admit that both yield proofs of
that doctrine of descent with modification which a
hundred years ago seemed to him so questionable.

Chamisso on the Alternation of Generations in Salpa.

Trembley (see p. 57) had shown that Hydra, though
an animal, multiplies by budding like a plant. He got
indications, upon which he did not altogether rely, that
it also propagated by eggs, and ten years later (1754)
this supposition was confirmed by Roesel, who figured
the egg, though he was unable to demonstrate that a
young Hydra issues from it ; subsequent inquiry has
placed the fact beyond doubt. In 1819 Chamisso
announced that Salpa, a well-known Tunicate which
abounds at the surface of the sea, exhibits a regular
alternation of the two modes of increase, the egg-pro-
ducing form being succeeded by a budding form, the

ALTERNATION OF GENERATION^ 'IN, S

budding form by the egg-producing form, and so on
indefinitely. Sars a few years later showed that the
common jelly-fish Aurelia also propagates by eggs and
buds alternately. Here the familiar swimming- disks,
which are of two sexes, produce eggs from which
locomotive larva issue. The larva at length settles
down and takes a Hydra-like form. It pushes upwards
an ascending column, which divides transversely and
forms a pile of slices, each destined to become a free,
sexual Aurelia. The alternation of generations may be
regarded as resulting from the introduction of budding
into the early stage of a life-history which culminates
in sexual reproduction, much as if a caterpillar were to
divide repeatedly and form more caterpillars, each of
which ultimately became a moth. The case which has
been given as an illustration actually occurs in nature.
A parasitic caterpillar, that of Encyrtus, divides while
still an embryo, so that one egg produces several
moths.1 Many other cases of alternation have since
been found among animals, and it seems to be the rule
among plants.

Alternation of generations may be complicated by
association with transformation, by the omission of
stages usual in the class, and by budding-out from one
part instead of from the whole body. In particular
cases the complication becomes so great that biological
language breaks down under it. Such terms as
generation, individual, organ, larva, adult, cannot
always be used consistently without either being
strained or artificially limited.

1 The same process of " embryonic fission " occurs in other
animals also, one of which is a mammal (Praopus).

102 PERIOD IV.

Baer and the Development of Animals.

The curiosity of the ancient Greeks led them to look
for the chick within the egg, and Aristotle mentions
the beating of the heart as a thing which might be
observed in a third-day embryo. After the revival of
science Fabricius of Acquapendente figured the chief
stages of development, from the first visible rudiments
to the escape from the egg-shell. Harvey, the dis-
coverer of the circulation, not only studied the develop-
ing chick, but took advantage of the rare opportunity
of dissecting breeding does from the royal parks. His
treatise on Generation is unfortunately impaired by
Aristotelian philosophy, and some of the theories there
set forth gave much trouble to Swammerdam. The
oft-cited maxim " Omne vivum ex ovo " does not occur
exactly in this form in Harvey's writings,1 nor does it
fairly state his own belief. Those who read his De
Generations will see that his knowledge was insufficient
to justify so wide a generalisation ; on this head it is
enough to mention that he was persuaded of the pro-
duction of insects without parents from putrefying
matter.9

Malpighi was the first to apply the microscope to
the embryonic chick. His figures are surprisingly full

1 Linnaeus (Fund. Bot. § 134, and Sponsalia Plantarum) gives
it as above; Harvey has "Ex ovo omnia"; "ovum esse primor-
dium commune omnibus animalibus," etc.

a Harvey need not have gone outside the writings of Aristotle
to get the substance cf his generalisation. He would have found
there that the chief task of both plants and animals is propaga-
tion, either by seeds, or eggs, which Aristotle believed to be
equivalent to seeds (Hist, anim., VIII., i.; De anim. gen., I., iv. ;
I., xxiii.). Aristotle excepted the "imperfect animals," such as
insects, and the seedless plants, concerning both of which his
knowledge was misty and inaccurate ; there is no indication that
Harvey was better informed.

BAER AND THE DEVELOPMENT OF ANIMALS 103

of interesting detail, and so far in advance of their age
that they long failed to produce their due effect. On
one point Malpighi unconsciously led naturalists astray
for a hundred years or more. On examining a fowl's
egg which he supposed to be unincubated, he discovered;
within it an early embryo. From this he concluded
that the embryo pre-exists in the egg, like a plant-
embryo in a seed. He mentions one circumstance
which makes everything intelligible. The egg was
examined in August, during a time of great heat, and
the Italian summer no doubt started development, like
the hot sand of Aden, in which Chinamen hatch their
eggs. Swammerdam too enforced the same belief in.
pre-existing germs. From the fact that the butterfly
can be revealed by opening the skin of a full-fed cater-
pillar he inferred (quite contrary to the opinion which
he expresses elsewhere) that one animal had formed
inside another. This led him to say that there is no
such thing as generation in nature, but merely the
expansion of germs which lie enclosed one within
another. By his theory he explained how Levi could
pay tribute to Melchizedek before he was born, and
how the sin of Adam can be laid to the charge of all
his posterity. The belief in the pre-existence of germs
was first shaken by Caspar Wolff (see p. 81), who
examined unincubated eggs but found no germ which
could be detected by the histological methods then
employed.

Swammerdam's Biblia Natures contains useful figures
of early and late tadpoles ; in particular, he describes a
stage in which the body is entirely composed of rounded
"lumps" or "granules," the cells of modern biology.

Early in the nineteenth century Pander and Baer,
both of whom were pupils of Dollinger, a teacher of

io4 PERIOD IV.

extraordinary influence, gave a new impetus to the
study of development. Pander (1817-8) published an
account of the early stages of the chick, illustrated by
beautiful plates by D'Alton. Baer (1828-37) carried
the work much further, not only greatly extending the
knowledge of the developing chick, but discovering the
mammalian ovum (1827), and announcing generalisa-
tions which down to 1859 were the most luminous that
embryology had ever furnished ; we may call him the
founder of comparative embryology. He shows that
development may supply decisive indications of the
zoological position of animals ; it teaches, for instance,
that insects are of higher grade than arachnids or
crustaceans, and that amphibians ought not to be
united with reptiles. He describes the development of
an animal as a process of differentiation, the general
becoming special, and the homogeneous heterogeneous ;
differentiation is, he remarks, the law under which not
only animals but solar systems develop. He maintains
that the embryo, though gradually attaining complexity,
makes no transition to a different type — e.g., the verte-
brate is never in any stage anything but a vertebrate.
All animals, he believes, are probably at first similar,
and take the form of a hollow sphere (the gastrcea of
modern embryology). There are, he says, no new
formations in nature ; all is conversion. When he
comes to speak of the pharyngeal clefts of mammals
and birds, recently discovered by Rathke, he remarks
that their correspondence with the gill-clefts of fishes
is obvious. We wonder what is coming next, but our
curiosity is not gratified by any memorable deduction.
Neither here nor in his miscellanies (Reden), published
nearly fifty years later, does he admit that mammals
and birds can have descended from gill-breathing

THE CELL THEORY 105

vertebrates. If we are inclined to hint that Baer, having
gone so far, might well have gone a little farther, it
is only fair to recollect that every leader in science is
more or less open to the same reproach.

The Cell Theory.

Any one of the higher animals or plants admits of
analysis into organs, each adapted to one or more
functions. Bichat (1801) showed that the body of one
of the higher animals is not only a collection of organs,
but also a collection of tissues, and the same is true of
the higher plants. Analysis of the organism was carried
a step further when in 1838-9 Schleiden and Schwann
announced that all the higher animals and plants are
made up of cells, which were at first supposed to consist
in every case of a cell-wall, fluid contents, and a nucleus.1
It was soon discovered that the cell-wall is as often
absent as present, and that the cell-contents are not
simply fluid; the nucleus is still believed to be universal.
Schwann proved that nails, feathers, and tooth-enamel,
though not obviously cellular, consist of nothing but
cells, and it was afterwards shown that bone, cartilage,
fatty tissue, and fibrous tissue arise by the activity of
cells which disappear from view in the abundance of
their formed products. The individual cells of a com-
plex organism are usually themselves alive ; sometimes,
as in ciliated epithelium, they give indications of life

1 Hooke figured a thin section of dry cork in his Micrographia
(1665), remarking- that it was divided into "little boxes or cells."
The word cell was suggested by the resemblance of the tissue to
a honeycomb ; since 1838 it has been thoughtlessly extended
from the skeleton to the particle of living matter enclosed within
it. Robert Brown (1831) showed that a nucleus is usual in
plant-cells ; it had been figured .by Fontana and others long
before. Down to 1838 no results of biological interest followed
from the discovery.

io6 PERIOD IV.

long after they have been separated from the body.
The preponderating importance of the transparent jelly
or protoplasm became clear when it was recognised
that this alone is invariably present, and that this alone
responds to stimuli. The nucleus is believed to be only
a specialised part of the cell-protoplasm.

The cell-theory, like nearly every theory, was neither
altogether new nor in its first form altogether complete.
Before 1838 cell-division, as we should now call it, had
been indistinctly seen to be the process by which the
body of one of the higher animals is built up. Leeuwen-
hoek and Swammerdam had found a wholly cellular
stage in frog-embryos (see p. 103), while Prevost and
Dumas in 1824 had in effect discovered that the cells of
which such embryos consist result from repeated division
of an egg ; Mohl in 1835 observed the actual division.
Even Schwann, however, was not acquainted with the
important fact that every cell arises by the division of a
pre-existing cell.

Swarm-spores of algae showed that protoplasm, when
unenclosed in a cell-wall, can move about, direct its
course, and change its shape. Knowledge of this fact
did more than rectify the definition of the cell ; it effaced
one distinction between plants and animals, and gave a
hint of the resemblance of primitive cells to such simple
organisms as Amoeba.

Martin Barry in 1843 announced that certain Protozoa
(that name was not yet in use) are simple cells. He
pointed out that they possess nuclei, like those of tissue-
cells, and compared their increase by fission with the
cleavage of the egg. Single cells were thus shown to
be not only capable of locomotion, which was already
known, but able to provide for their own support. The
Protozoa and Protophyta (i.e., the simplest animals and

THE CELL THEORY 107

plants, which are not always to be clearly separated) are
now known to be autonomous cells, increasing by fission,
and often forming- colonies. Conjugation (fusion of
similar individuals) often precedes fission, and when it
was proved (1861-5) that ova and spermatozoa are true
cells, it was seen that fertilisation, as we know it in the
higher animals, is only a special form of the conjugation
observed among the Protozoa. To the Protozoa it is
now possible to trace, without any startling break of
continuity, all the multicellular organisms, their tissues,
the growth of those tissues by repeated fission, their
eggs, and the process of fertilisation which precedes
cleavage. The old Greek riddle, '* Which came first,
the fowl or the egg ? " may now receive the answer :
" Neither ; their common starting-point is to be found
in the Protozoa, which, even when adult, represent the
primitive unicellular condition, to which all the higher
animals revert once in every generation."

It is not without reason that biologists dwell on the
unifying influence of the cell-theory, which has become
a chief support of that still wider unifying influence, the
Origin of Species by Natural Selection. When it was
discovered that all living things, whether plants or
animals, consist of nucleated cells which increase by
fission, and that in all of them cell-fission is started
anew from time to time by a cell-fusion, it was strongly
suggested that resemblances so striking and so universal
can only proceed from a common descent.

During the last half-century the study of cells has led
to a great increase of knowledge respecting all bodily
functions, whether in health or disease. We now look
to it as perhaps the most hopeful source of new light
upon the important question of hereditary transmission.

H 2

io8 PERIOD IV.

The Scientific Investigation of the Higher Cryptogams.
We now resume the history of a study which down
to the end of the eighteenth century had yielded only
meagre and uncertain results (see above, pp. 85-88).
At the date in question it had been ascertained that the
spores (then called " seeds ") of ferns, and probably
of other cryptogams, are capable of propagating the
species, but no one knew precisely what part the spore
played in the life-history, or could explain the true
difference between a cryptogam and a flowering plant.
The great improvements in the construction of the
compound microscope which were effected between
1812 and 1830 rendered it possible to elucidate much
more thoroughly the structure and development of the
chief groups of cryptogams. The sexual reproduction
of algae was explored ; moving filaments (spermato-
zoids) were seen to enter the chambers in which
embryos afterwards formed ; the conjugation of similar
cells was observed in algae and fungi, and recognised
as a simple mode of sexual reproduction. The resem-
blance of the spermatozoids of mosses and ferns to
animal spermatozoa was noted, and their participation
in the process of fertilisation was more and more closely
followed until at length Hofmeister in 1851 saw them
fuse with the egg-cell of a fern. Suminski, whose full
name, Lesczyc-Suminski, is unpronounceable by English-
men, had discovered (in 1848) that the prothallus of a
fern, which is the product of the germinated spore and
had been hitherto taken for the cotyledon, bears two
kinds ot reproductive organs, one of which liberates
spermatozoids, while an egg-cell is developed within
the other. He did not correctly describe all the details,
but he showed where the essential reproductive organs

THE ENRICHMENT OF ENGLISH GARDENS 109

form, and where fertilisation is effected. The masterly
researches of Hofmeister (1849-57) fused what had been
a number of partial discoveries into a connected and
luminous doctrine. He proved that the prothallus is
one of two generations in the life-history ; that it
begins with a spore and ends with a fertilised egg-cell ;
that in the higher cryptogams there is a regular alterna-
tion of generations ; that the prothallus of the fern
answers to the leafy moss, while the leafy fern is the
equivalent of the moss-capsule ; that the egg-cell is the
same structure in both cryptogams and flowering plants ;
that the pollen-tube and the seed are found to-day only
in flowering plants ; that the gymnosperms make a
transition from the higher cryptogams to the angio-
sperms ; that unity of plan pervades the whole series of
mosses, ferns, fern-like plants, gymnosperms, and
angiosperms. Before Darwin's Origin of Species had
appeared Hofmeister presented to evolutionists a clear
example of a descent in which every principal term is
well authenticated, while the extremes are far apart.

The Enrichment of English Gardens.
If some unreasonably patriotic Englishman should
be seized with the whim of keeping none but truly
British plants in his garden, he might enjoy the shade
of the fir, yew, oak, ash, wych-elm, beech, aspen-
poplar, hazel, rowan-tree, and the small willows, but
he would have to forego the common elm, the larger
poplars and willows, the larches, spruces, and cypresses,
the rhododendrons, and all the shrubs popularly called
laurels. Of fruits he might have the crab-apple, sloe,
wild cherry, gooseberry, currants (black and red), the
raspberry, strawberry, and blackberry, but none of the
improved apples, pears, or plums, and no quinces,

no PERIOD IV.

peaches, or apricots. His vegetable garden might
yield cabbages, turnips, carrots, and celery (all deficient
in size, flavour, and variety), but no cauliflowers,
Brussels sprouts, parsley, lettuces, peas, beans, leeks,
onions, or spinach. The handsomest of his flowers
would be dog-roses, mallows, and primroses.

Before Europe was sufficiently enlightened to care
about exact records valuable foreign plants had already
been introduced. Vines, apples, pears, cherries, and
plums, besides improved vegetables, such as the cauli-
flower, bean, garden-pea, and cucumber, had been
brought from temperate Asia or Egypt. Wheat and
barley, neither of them native to Europe, had to some
extent replaced rye and oats, which may have existed
naturally in those European countries which border on
Asia. Britain, while yet a Roman province, shared in
these benefits, and it is believed that the common elm,
besides certain fruit-trees and pot-herbs, have been
continuously grown in our island through all the
troubled ages which separate us from the Romano-
British times. Leek, garlic, and onion are ancient
acquisitions. To our Old-English forefathers garlic
was the spear-leek, distinguished by its long, narrow
leaf from the broad-leaved common leek, just as a
garfish was distinguished from other fishes by its long
body and pointed head ; onion was the enne- or ynne-
leek (onion-leek) ; the most important of the three was
probably that which retained the root-word without
prefix — the leek proper.

During many centuries, when the rights of small
proprietors were little respected and knowledge was
scanty, the religious houses were distinguished by the
diligence with which they tended their gardens.
Flowers, fruits, and simples were cultivated, and plants

THE ENRICHMENT OF ENGLISH GARDENS in

were now and then imported from foreign monasteries.
The English names of the plants, which are often
adaptations of Latin words, still testify to the care of
gardeners who were in the habit of using Latin.

Much improvement was not to be expected so long
as England suffered from frequent and desolating wars
within her own borders. When these at last subsided,
great English gardens, such as those of Nonsuch,
Hatfield, Theobalds, and Hampton Court, began to
parade their beauty ; strange trees, shrubs, and flowers
were brought from the continent, and as early as Queen
Elizabeth's time our shrubberies and walks were admired
by spectators familiar with the best that Italy and
France could show. The new horticulture was, how-
ever, long an exotic among us, and John Evelyn,
whose Sylva appeared in 1664, was "the first to teach
gardening to speak proper English."

In the latter part of the sixteenth century the follow-
ing new plants among others were brought from central
or southern Europe : The poppy and star anemones,
the hepatica, the common garden larkspur, the winter
aconite, the sweet-William, the laburnum, Rosa centi-
folia (of eastern origin, the parent of countless varieties
and hybrids), the myrtle, the lavender, the cyclamen,
the auricula, Iris germanica, and many other Irids, the
oriental hyacinth, several species of Narcissus, the
white and Martagon lilies, and the absurdly named
dog's-tooth-violet (really a lily). The botanist Clusius
introduced the jonquil and the Tazetta narcissus from
Spain to the Low Countries. The Judas-tree (i.e.,
tree of Judaea) was brought from the Mediterranean,
where the hollows of the hills are filled in April with
its pale-purple blooms. The white jasmine was im-
ported from Asia, and the castor-oil plant from Africa.

ii2 PERIOD IV.

The great accessions of geographical knowledge
made during the fifteenth and sixteenth centuries were
slow to affect horticulture. Ships were then few and
small, and the passage from Hispaniola or Calicut to
Cadiz or Lisbon occupied weeks or even months.
Moreover, the conquests of Spain and Portugal (Goa,
the Moluccas, Brazil, the West Indies, Peru, and
Mexico) lay mostly within the tropics, and could
furnish hardly any plants capable of enduring a
European winter. Special pains were, however, taken
to bring1 over some valuable food-plants which were
thought likely to thrive in Europe. Before any Euro-
pean landed in America the potato had been cultivated
by the Indians of Peru, a country which, though lying
almost under the line, rises into cool mountain-districts.
Potato-tubers were soon introduced to Spain and Italy,
and a little later to other parts of Europe ; Raleigh's
planting of potatoes on his estate near Cork came a
few years later. The edible tomato, which is distin-
guished from the wild form by its enlarged fruits, was
apparently cultivated in Peru before the first landing
of the Spaniards. The unusually high proportion of
edible plants among the first importations from America
and other distant countries is worthy of remark. Early
explorers eagerly sought for valuable food-plants, but
the number of such as could be cultivated alive in
Europe was very limited, and since the sixteenth
century the attention of collectors has been fixed upon
ornamental species simply because of the dearth of
others.

European flower-gardens were enriched during the
sixteenth century by the following American species :
the so-called French and African marigolds (both
from Mexico), sunflowers, the arbor-vitae (Thuja

THE ENRICHMENT OF ENGLISH GARDENS 113

occidentalis), Yucca gloriosa, and the Agave, misnamed
the American Aloe.

About the same time the horse-chestnut, lilac, and
syringa, or mock-orange, were first brought to central
and western Europe, and with them the tulip, richest
and most varied of flowering- bulbs. All these reached
Vienna from Constantinople, but how and when they
were brought to Constantinople, or what were their
native countries, are still doubtful questions. The
horse-chestnut is believed to be a native of Greece,
where it is said to grow wild among the mountains ;
probably it extends into temperate Asia as well. It is
said to have reached Constantinople in 1557. Long-
standing tradition derives the lilac from Persia, but
botanists say that it is also indigenous to parts of south-
eastern Europe. The garden-tulip is believed to be
native to temperate Asia and also to Thrace ; it is, of
course specifically distinct from the wild tulip of
northern Europe.

Chief among the travellers to whom we owe the
acquisition of these favourite plants was Augier Ghislen
de Busbecq, a Fleming, who was twice sent by the
emperor as ambassador to the sultan. Busbecq was a
keen observer and collector, and during his long and
toilsome journeys was ever eager to pick up curiosities
or to note new facts. Quackelbeen, a physician in
Busbecq's suite, is named as another helper. The
botanists Mattioli and Clusius, who presided in succes-
sion over the imperial gardens of Vienna, and Gesner
of Zurich, described the plants ; it is from them that
we draw such imperfect knowledge as we possess of the
way in which they were brought to central Europe.
Clusius relates that Busbecq in 1575 received a parcel
of tulip-seed from Constantinople, and being obliged to

ii4 PERIOD IV.

journey into France, left it with Clusius to be germi-
nated. The tulips which came up were of various
colours, an indication of long cultivation. The Turks,
like the Persians, took great delight in gardens.

As North America became permanently occupied by
the English, facilities for the transport of live plants to
Europe steadily increased. Ships began to sail frequently
to and fro, for the crossing of the Atlantic was but a
small affair in comparison with the voyage round the
Cape of Good Hope. Educated men here and there
practised the learned professions in the American planta-
tions, and among them a sprinkling of naturalists was
found. Hothouses, the amusement of wealthy amateurs
in Germany, France, and Holland, made it possible to
protect the plants of mild climates from the winter cold
of northern Europe. By the end of the seventeenth
century our gardens had acquired many beautiful and
curious American plants, besides a few from the East
Indies, and not long afterwards the gains became so
frequent that the botanists of Europe found it hard to
name the new species as fast as they came in.

Lovers of horticulture will tolerate a little further
information concerning the early use of hothouses. As
soon as glass began to be employed in domestic archi-
tecture, the construction of warmed and glazed chambers,
in which plants could be grown, was attempted. Writers
of the first century A.D. mention them, and Seneca
explains how the temperature might be kept up by hot
water. This and other refinements of the Roman
Empire passed into oblivion during the long decline of
civilisation, but revived with the revival of the arts.
In the sixteenth century William IV., Landgraf of
Hesse, who is remembered, among other things, as a
patron of the botanist Clusius, built himself a green-

THE ENRICHMENT OF ENGLISH GARDENS 115

house, which could be taken down and put together
again. A still more famous orangerie was that of
Heidelberg, which served as an example to the kings
and nobles of Europe.1 Henri IV. built one at the
Tuileries, and long afterwards Louis XIV. had one at
Versailles. Madame de SeVigne" describes theorangerie
of Clagny as a palace of Armida, and the most enchant-
ing novelty in the world. The pine-apple was brought
over from Barbadoes in the seventeenth century, and
Evelyn speaks of having tasted the first pine-apple
grown in England at the table of Charles the Second.
For two hundred years the hothouse yielded no greater
dainty, but rapid transit has now made pine-apples so
cheap that it is no longer worth while to raise them in
England. Fagon, who was during many years first
physician to Louis XIV., was a considerable botanist.
He was born and died at the Jardin des Plantes, and
here, on his retirement from practice, he built hot-
houses ; it would be interesting to know what he grew
in them.

In the first half of the seventeenth century the
younger Tradescant, who, like his father before
him, was gardener to our Charles I., brought over
from America the spider-wort, named Tradescantia
after him,2 the false acacia and the tulip-tree. The
magnolias, or some of them, the Virginian creeper,
and the scarlet Lobelia cardinalis were among
the gifts received from North America about the

1 Parkinson (1629) speaks of a stove or hothouse, " such as are
used in Germany."

2 The graceful practice of naming genera of plants after bene-
factors to botany or horticulture was introduced by Father
Plumier (1646-1704), who gave the names of L'Obel and Fuchs to
the Lobelia and Fuchsia, and whose own name is appropriately
borne by the frangipane (Plumeria).

n6 PERIOD IV.

same time. The dwarf Lobelia (L. Erinus) was not
brought over from the Cape of Good Hope till 1752, and
Lobelia splendens and fulgens (both from Mexico) not
till the nineteenth century. One of the passion-flowers,
which are all American, came over about this time ;
but Passiflora caerulea, the favourite ornament of the
greenhouse, was only imported from Brazil in 1699.
The evening primrose, the " convolvulus major and
minor " (Ipomaea purpurea and Convolvulus tricolor),
were other acquisitions from North America.

From the second half of the seventeenth century
dates the introduction of the garden nasturtium (Tro-
paeolum majus) from Peru ; T. minus from Mexico had
been brought over nearly a hundred years earlier. The
sensitive plants and the pine-apple now became frequent
objects in English greenhouses. John Evelyn and
Bishop Compton were eminent patrons of English horti-
culture during this age.

The first half of the eighteenth century brought us
the Aubretia and the sweet pea from southern Europe,
the first Pelargoniums (scarlet geraniums) from the Cape,
the camellia and Kerria japonica from the far east.
The West Indian heliotrope was introduced in 1713; the
better-known Peruvian species not till 1757. Phloxes
began to be imported from North America. Two or
three foreign orchids were already known, and the
number now began to increase ; but it was not till the
nineteenth century that they came over in crowds.
Our list gives no notion whatever of the number of new
species added now and subsequently.

Of the accessions made during the latter half of
the eighteenth century we must at least mention the
mignonette from North Africa, white arabis from the
Caucasus, the common rhododendron from Asia Minor.

THE ENRICHMENT OF ENGLISH GARDENS 117

Rosa indica and Hydrangea hortensis from China,
South African gladioli, which now begin to be numerous,
and chrysanthemums from China and Japan. The first
calceolarias were brought from great heights on the
Andes, the first begonias from Jamaica, and the first
fuchsia from Chili.

We can make only one remark about the multi-
tudinous accessions of the nineteenth century. It is
surprising to note how recently many established
favourites have been brought to the knowledge of
English gardeners. Anemone japonica (Japan) and
Jasminum nudiflorum (China) date from 1844, while
the Freesias (Cape Colony) are as recent as 1875.
The dahlia, after two unsuccessful attempts, was estab-
lished here as recently as 1815 ; Nemophila insignis
came over from North America in 1822 ; the common
musk and the monkey-plant a few years later ; the
chionodoxas (Crete and Asia Minor) in 1877. The first
of the foliage-begonias (Begonia rex from Assam) dates
only from 1858, and the first of the tuberous species
from 1865.

Importation of foreign species has not been the only
method by which English gardens have been enriched.
New varieties and hybrids have been produced in
bewildering numbers by the gardeners of Europe, and
many of these far surpass in beauty the wild originals.
Botanists and nurserymen could relate in great detail
the steps by which our favourite roses, calceolarias,
begonias, and cinerarias have been developed from a
few natural stocks, sometimes of uninviting appearance.

Horticulture has repaid the debt which it owed to
the explorations of botanists by furnishing countless
observations and experiments bearing upon inheritance.
When these have been properly co-ordinated, they will

u8 PERIOD IV.

yield precious knowledge, not only to botanists but to
all students of biology.

Humboldt as a Traveller and a Biologist.

The career of Alexander von Humboldt (b. 1769,
d. 1859), nearly coinciding with the period on which
we are now engaged, was devoted to a gigantic task —
nothing less than the scientific exploration of the globe.
His great natural powers were first cultivated by wide
and thorough training, not only in astronomy, botany,
geology, mineralogy, and mining, which had an obvious
bearing on his future enterprise, but also in anatomy,
physiology, commerce, finance, diplomacy, and lan-
guages. Thus equipped, he sailed in 1799 with the
botanist Bonpland to South America, and spent the
next five. years in exploring the Orinoco and Amazon,
the Andes, Cuba, and Mexico. The expedition marks
an epoch in scientific geography. It is enough to
mention the collection of data for the more accurate
mapping of little-known countries, the exploration of
the river-systems of equatorial America and the dis-
covery of a water-connection between the Orinoco and
the Amazon, the ascent of lofty mountains, the study of
volcanoes, the description of remarkable animals such
as the howler-monkey and the gymnotus (electric eel),
and of remarkable plants, such as the bull's-horn
acacia, whose enlarged and hollow spines are occu-
pied by ants.1 After his return to Europe Humboldt
published many important treatises on terrestrial
magnetism, geology, meteorology, and plant-distri-
bution. His new graphical method of isothermal
lines did much for the study of climate in all its bear-
ings. His Personal Narrative not only disseminated

1 See the account of Cartagena in the Personal Narrative.

HUMBOLDT AS TRAVELLER AND BIOLOGIST 119

much interesting- information, but inspired a new
generation of explorers. Darwin agreed with Hooker
that Humboldt was the greatest of scientific travellers.

In 1829 Humboldt traversed the Russian Empire
from west to east, but the time allowed (half a year)
was altogether insufficient for the examination of so
vast a territory ; a few notable results were, neverthe-
less, secured.

After some fifteen or twenty years spent in European
society, the inspiration drawn from long and arduous
journeys in South America began to fail. The con-
versation of the salons, the troublesome flattery of the
King of Prussia, and the propensity to write copiously,
stimulated, of course, by the eagerness of the public
to buy whatever so eminent an investigator chose to
put forth, sterilised the last half of a career which had
opened with such magnificent promise.

The best of Humboldt's work became absorbed long
ago into the confused mass of general knowledge. This
is the common fate (not by any means an unhappy one)
of those who refuse to concentrate upon a single study.
Among biologists he is chiefly remembered by his
numerous discussions of plant-distribution, which are
now considered less remarkable for what they contain
than for what they leave out. While his travels were
fresh in his mind, Humboldt was impressed by facts of
distribution which could not be explained by present
physical conditions,1 but the influence of climate as the
more intelligible factor gradually assumed larger and
larger proportions in his mind. The writers of text-
books, founding their teaching upon Humboldt, often
overlooked altogether qualifications which he had

* See particularly his Essai sur la geographic des plantes (1805).

120 PERIOD IV.

shown to be necessary. When Darwin and Wallace
pointed out how immensely important is the bearing
upon present distribution, not only of the physical
history of the great continents, but also of their bio-
logical history, and in particular of the interminable
conflicts of races of which they have been the scene,
naturalists began to perceive how inadequate are hori-
zontal and vertical isothermal zones to explain all the
striking facts of distribution, whether of plants or
animals (see infra, p 129).

Premonitions of Biological Evolution.

The eighteenth century had done much to impress
the minds of men with an orderly development in sun
and planets (Kant and Laplace), in the institutions of
human societies (Montesquieu), and in the moral aspira-
tions of mankind (Lessing). Many bold attempts had
been made to trace a like orderly development in the
physical life of plants and animals (Buffon, Erasmus
Darwin, etc.), but neither was the proof cogent nor the
process intelligible. Cautious people therefore, and
those whose prepossessions inclined them to adopt a
very different origin for terrestrial life, held during all
this time a position of some strength against speculative
philosophers who tried to explain the variety and perfec-
tion of living nature by unconscious and unintelligent
factors.

About the year 1840 the doctrine of the fixity of
species seemed to be victorious. Cuvier's knowledge
and skilful advocacy had a few years before over-
powered Geoffrey St. Hilaire's conception of a common
plan of structure pervading the whole animal kingdom,
and the new Philosophic Anatomique was laid on the
shelf, side by side with the Philosophic Zoologique of

PREMONITIONS OF BIOLOGICAL EVOLUTION 121

Lamarck, the Zoonomia of Erasmus Darwin, the Theorie
de la Terre of Buffon, and the Protogcea of Leibnitz.
Yet even then a spectator who was fully informed and
at the same time gifted with uncommon foresight might
have satisfied himself that the victory of evolution had
become inevitable.

Cuvier's memorable descriptions of the extinct verte-
brates of the Paris basin had founded the new science
of Palaeontology, and though neither he nor anyone else
was aware of the fact, had made it possible to trace,
very imperfectly no doubt, the descent of a few modern
ungulates. Lyeli's Principles of Geology (1830-3) had
shaken the belief in catastrophes repeatedly breaking
the succession of life on the earth. It was rapidly
becoming impossible to maintain that the account of
creation given in the book of Genesis was even approxi-
mately accurate. In the year 1828 Baer had almost
made up his mind that the facts of development pointed
to a common plan of structure, perhaps to a common
origin, for each of the great types of animal life.1
Darwin's Journal had appeared in 1839, and though
the explanations which it offered were not inconsistent
with prevalent opinion, evolutionary suggestions were
introduced into the second edition of 1845. Lyell at
least was already aware that the voyage of the Beagle
had impelled Darwin to examine afresh the accepted
philosophy of creation. Between 1840 and 1850 faint
signs of coming change struck orthodox reasoners
with misgiving and gave increased confidence to free-
thinkers. A few German botanists and zoologists
declared against the immutability of species. The

1 Baer's expressions are so guarded that his real opinions in
1828 can only be surmised. He never accepted a consistent
theory of organic evolution.

I

122 PERIOD IV.

Vestiges of the Natural History of Creation, which
might be called a premature explosion, dates from
1844. Hofmeister (see supra, p. 109) put forth a detailed
comparison of the flowering- plants with the higher
cryptogams, which strongly suggested a theory of
descent with modification, and is unintelligible on any
other basis. He indicated no such interpretation him-
self, being content to establish the new homologies ;
but the Origin of Species, as soon as it appeared,
commanded his entire sympathy.

Among those who rejected fixity of species and
special creation before 1859 none was so clear or so
outspoken as Herbert Spencer, who thought out for
himself an evolutionary philosophy which was not
shaken by Darwin. It is impossible to discuss in this
place the question whether or not it was shaken by
Weismann.

Agassiz's Essay on Classification, which was published
in October, 1857, was the last manifesto issued before
the Origin of Species by the party which stood out for
fixity of species, the last polemic which made De
Maillet, Lamarck, and the Vestiges its targets. It is
an eloquent but inconsiderate defence of an extreme
position. According to Agassiz every branch, class,
order, family, genus, and species represents a distinct
creative thought ; every mark of affinity, every appear-
ance of adaptation to surroundings, has been expressly
designed. Extinction and replacement of species are
due to the direct intervention of the Creator ; ptero-
dactyls are prophetic types of birds, and indicate that
divine wisdom had foreseen the possibility of an
advance in the organisation of animals which was not
immediately practicable ; the mallard and scaup duck
occur on both sides of the Atlantic because they were

PREMONITIONS OF BIOLOGICAL EVOLUTION 123

simultaneously but separately created in Europe and
North America ; the teeth of the whale, which never
cut the gum, are the result of obedience to a certain
uniformity of fundamental structure. Explanations
like these removed no difficulties and sug-g-ested no
inquiries. In the hot debates which ensued the
Essay on Classification was rarely mentioned.

I 2

PERIOD V.

(1859 AND LATER)

Period V.

WE do not attempt to characterise our last period, nor
to describe its biological achievement. It seems better
to devote the whole of our scanty space to the scientific
careers of Darwin and Pasteur, in which so much past
effort culminated, and from which so much progress
was to spring.

Darwin on the Origin of Species.

Setting aside as superfluous and we might say
impossible, under our conditions of space, all attempt
to restate the evidence on which Darwin based his
great argument, we shall here try to show that the
Origin of Species shed a new light upon many biological
facts, combined many partial truths into one consistent
theory, and gave a great stimulus to further inquiry.

i. Classification and Affinity. — The sixteenth-century
herbalists and still earlier writers (see p. 17) recognised
a property of affinity, by which plants were associated
in natural groups. Bock (1546) tried to bring together
all plants which are related (verwandt) to one another,
but similarity of any kind was with him a proof of
affinity ; it did not shock him to place the dead nettles
next to the stinging nettles. L'Obel gave names to
several families of flowering plants which are still
admitted as natural. Ray spoke of the affinity
(cognatio) between plants, and his affinity was a thing

124

DARWIN ON THE ORIGIN OF SPECIES 125

not to be violated for the sake of practical convenience
or logical rules, but he was unable to explain what
he meant by it. Linnaeus tried to illustrate affinity
between plants by contiguous provinces on a map, a
better metaphor than the linear scale, for the scale can
only express affinity on two sides, while the map can
express affinity on many. His practical experience of
classification taught him a truth, shocking at first
sight to the logician1 — viz., that the characters which
serve for the definition of one genus may be useless for
the definition of the next, and he laid it down that the
characters do not make the genus, but the genus the
characters. After Linnaeus we find for a long time no
advance in the philosophy of natural classification.
Cuvier (1816) is even retrograde, for he sets aside the
maxims of Linnaeus, maintains that adaptive characters
(characters closely related to the conditions of life) are
relatively constant, and that large groups should be
defined by characters drawn from organs of great
physiological importance. These decisions of his are
repudiated by later naturalists.

The key to the affinity puzzle which had so long
baffled thinking naturalists was at last supplied by
Darwin, who explained that "the natural system is
founded on descent with modification ; that the char-
acters which naturalists consider as showing true
affinity between any two or more species, are those
which have been inherited from a common parent, all
true classification being genealogical ; that community
of descent is the hidden bond which naturalists have

1 Titius of Wittenberg, who published in 1766 what is commonly
called Bode's law of planetary distances, objected to the Linnean
system on the ground that it multiplied the principle of division.
(De di-visione animalium generali, 1760.)

126 PERIOD V.

been unconsciously seeking, and not some unknown
plan of creation, or the enunciation of general proposi-
tions, and the mere putting together and separating
objects more or less alike."1

Natural groups, large or small, result from the long-
continued operation of divergence, the survival of
some, and the extinction of others ; they are to be
respected as facts ; they are not created by definitions,
which only serve to indicate and remind ; any character,
however trifling, will suffice, if only it is constant and
distinctive.

The conflict between natural classification and logic
is apparent only. Logicians say that in classifying
books, for instance, you may take any property you
please, subject, size, etc., as the basis of your arrange-
ment, but having made your choice, you must adhere
to it for all divisions of the same rank. Naturalists
seem to say something different, for they are agreed
that what they call "single-character classifications,"
in which one property is adhered to throughout, are
unnatural. The fact is that a natural classification
always rests upon one and the same property — viz.
affinity p, i.e. relative nearness of descent from some
common ancestor. Every natural classification, like
every logical classification, proceeds upon a single basis,
and the failure of the single-character classifications
is due to their displacing affinity by some definition.

The effect of the Origin of Species upon zoological
and botanical systems has been revolutionary. Fur-
nished with a new and intelligible meaning of the word
natural, and with new criteria of naturalness, syste-
matists have during the last fifty years worked hard to

1 Origin of Species, chap. xiii.

DARWIN ON THE ORIGIN OF SPECIES 127

create classifications which admit of being- thrown into
the form of genealogical trees. Wide gaps in the
geological history of life render the task difficult beyond
expression, but much has already been accomplished.
Newly discovered forms (especially the fossil Archaeop-
teryx and the Cycadofilices) and more fully investigated
forms, far too numerous to be specified, have estab*
lished links between groups which formerly seemed to
be wholly independent. Unnatural assemblages based
on pre-determined characters (Radiates, Entozoa, Birds
of prey, etc.) have been replaced by groups which are
at least possible on evolutionary principles. Almost
every working naturalist will admit that the progress
of zoological and botanical system during the last two
generations has done much to fortify the Darwinian
position.

2. Embryology. — Baer in 1828 was possessed of all
the embryological facts which Darwin used in support
of his theory of evolution ; in particular, he was well
acquainted with the most striking fact of all — viz., the
presence in embryo mammals and birds of a series of
paired clefts along the sides of the neck, between which
run vessels arranged as in gill-breathing vertebrates*
The vessels had been figured by Malpighi ; the clefts
had been discovered by Rathke, who had no hesitation
in calling them gill-clefts and the vessels gill-arches.
Nor had Baer, who nevertheless to the end of his long
life refused to accept the one explanation which gives
meaning to the facts — viz., that remote progenitors of
mammals and birds breathed by gills. Few embryo-
legists have since felt such a scruple. The adaptation
to gill-breathing is obvious ; is gill-breathing now
practised by any mammal or bird? Certainly not. Is
it destined to be practised by their descendants at

128 PERIOD V.

some future time ? To say nothing- of the danger of
putting forth any such prophecy, it involves all the
consequences of descent with modification. The
opponent of evolution may as well admit at once that
the gill-breathing- was practised in time past. As an
example of the same kind taken from plants, we may
quote the trifoliate leaves of the furze-seedling, which,
though absent from the full-grown furze, are frequent
in the family (Leguminosae) to which it belongs. The
general similarity of vertebrate embryos, of insect-
embryos and of dicotyledonous seedlings, is also worthy
of note. We may suppose that early embryos, being
largely or wholly dependent on food supplied by the
parent, and perhaps protected by the parent as well,
escape the pressure of the struggle for existence, and
are often not urgently impelled to produce adaptations
of their own. In these circumstances it is intelligible
that features inherited from remote ancestors should
persist. If, however, early independence is demanded
by the conditions of life, the embryo may develop
temporary adaptations, wanting in the parent and in
embryos of allied groups. Larval adaptation is as
much a part of the economy of nature as the retention
of ancestral structures which have been lost by the
adult.

3. Morphology. — Let us next consider the light which
the Origin of Species throws upon homologous parts.
No example will serve our purpose better than the very
familiar one of the fore-limbs of different vertebrates,
the arm and hand of man, the wing of the bat, the wing
of the bird, the pectoral fin of the fish, and the paddle of
the whale. These limbs, adapted for actions so diverse
as grasping, running, flying, and swimming, neverthe-
less exhibit a common plan, evident at a glance, except

DARWIN ON THE ORIGIN OF SPECIES 129

in the pectoral fin of the fish. But why a common plan ?
Of what advantage is it to an animal that its wing,
paddle, or hand should reproduce the general plan of a
fore-foot? Why should the digits of the land verte-
brates never exceed five ? Why should the thumb never
have more than two free joints ? It would be hard to find
a satisfactory answer to these questions in any book
earlier than the Origin of Species ; no student of the
Origin of Species finds any difficulty in answering them
all. The common plan has been transmitted from type
to type by inheritance, and its features are derived from
an unknown common ancestor.

The new conception, that structures inherited from
remote ancestors may be incessantly modified by the
conditions of life and by mutual competition, is the key
to the chief problems of morphology. No limited collec-
tion of examples can substantiate so wide a proposition
as this. Those who have made themselves familiar with
old text-books of comparative anatomy will recollect how
dry, or else how inconclusive, was pre-evolutionary mor-
phology, how vague were the references to some ideal
archetype, or to climate, or to the ancient conditions of
the earth's surface ; how often exclamations of admira-
tion for the marvels of nature or Providence were sub-
stituted for clear explanations. Cuvier, it is true, was
both precise and reasonable ; but how little he was in
a position to explain ! His " empirical " comparative
anatomy could throw no direct light upon origins or
transformations ; his " rational " comparative anatomy
was practicable only in a few easy cases.

4. Geographical Distribution. — The facts of distribu-
tion were handled in the Origin of Species with great
originality. It was shown that they support, and
indeed require, some doctrine of organic evolution.

i3o PERIOD V.

The succession in the same area of the same types-
armadillos succeeding- armadillos in South America,
marsupials succeeding marsupials in Australia — was
enough of itself to render independent creation highly
improbable. This was not all. Darwin's mind being
charged with facts and reasonings, the accumulations of
many years of travel and meditation, he sketched in-
rapid outline conclusions which have given a new form
to the distribution question. The subject had hitherto
been treated by collecting masses of facts and inter-
preting them by recent physical geography ; Darwin
showed that the history of the continents and islands
may be far more influential than soil, elevation, or
climate.

The scientific discussion of the facts of distribution is
as old as the sixteenth century, when L'Obel pointed out
that the mountain plants of warm countries descend
to low levels in the north. Linnaeus remarked that
fresh-water plants and alpine plants are often cosmo-
politan. Another early and well-founded generalisation
is the statement of Linnasus that the plants common to
the old and the new world are all of northern range.
Buffon made the same remark about the animals, and
offered the probable explanation — viz., that since the
two great land-masses approach one another only in
high latitudes, it is only there that animals have been
able to cross from one to the other.

In the nineteenth century theories involving prodi-
gious changes of land and sea were much in the minds
of naturalists. Darwin lost his temper (a rare thing
with him) over the land-bridges, hundreds, or even
thousands, of miles long, which were created in order
to explain trifling correspondences in the population of
distant countries. A belief in the comparative stability

DARWIN ON THE ORIGIN OF SPECIES 131

of the great continents and oceans has since prevailed,
and it is now recognised that the means of dispersal of
species are greater than was once supposed.

The discovery, about the year 1846, of the marks of
ancient glaciers in all parts of northern Europe, and the
acceptance of an Ice Age, had a still greater influence
upon the teaching of naturalists. Edward Forbes1 put
forth a glacial theory to account for the present distribu-
tion of plants of northern origin. Glacial cold, he main-
tained, had driven the arctic flora far southward. When
more genial conditions returned, most of the northern
plants retreated towards the Pole, but some climbed the
mountains and gave rise to an isolated alpine flora.
Darwin, whose unpublished manuscripts had anticipated
Forbes's theory, believed that the whole earth became
chilled during the Ice Age, and that the fauna and flora
of the temperate zone reached the tropics. His argu-
ment, which is contained in chap. xi. of the Origin oj
Species, is now generally accepted in principle, though
opinions differ on many points of detail. Some think
that he extended too widely the effects of glacial cold,
exaggerated the resemblance of the arctic and alpine
fauna and flora, and attributed the extinction of the
northern species in the intermediate plains too exclu-
sively to climatic causes.

One paragraph in the extremely condensed discussion
on geographical distribution which we find in the Origin
of Species calls attention to the dominance of forms of
life " generated in the larger areas and more efficient
workshops2 of the north." The power which inhabitants

1 Geol. Survey Memoirs, 1846.

2 By a curious and no doubt accidental coincidence, Darwin
employs the same remarkable metaphor which had occurred to
lordanes in the sixth century A.D. lordanes calls the north the
officina gentium.

132 PERIOD V.

of the great northern land-mass of the old world,
and in a less degree those of North America, possess,
and have long- possessed, of driving- out the inhabitants
of the southern continents is one of the most important
factors in the peopling- of the earth with new races of
land-plants and land-animals. Races of men, modes
of civilisation, religious faiths, all follow the same rule,
which has no doubt prevailed ever since land came to
predominate in the northern hemisphere and water in
the southern hemisphere. In the life of the sea and the
fresh waters no dominance of northern forms has been
detected.

5. Palceontology . — We must not claim for Darwin
more than a modest share in the vast extension of
pala3ontological knowledge which the last fifty years
have created. A profusion of new materials has been
acquired by the diligence of collectors working- on a
scale previously unattempted. But though the accu-
mulation of materials is the work of others, the inter-
pretation has been guided by the principles of Darwin.
The evolution of the horse has now been so fully
worked out that it would bear the whole weight of a
doctrine of descent with modification, though it could
not by itself reveal the process by which the modifica-
tion had been effected.

Darwin on Adaptations. — The adaptation of living
things to their, surroundings has always been a
favourite branch of natural history, underrated only
by those whose studies are little calculated to inflame
the curiosity. Many eminent naturalists have made the
interpretation of natural contrivances their chief aim.
Darwin equalled the best of his predecessors in accu-
racy, range, and ingenuity, while he surpassed them all
in candour. No one has done so much to vindicate the

DARWIN ON THE ORIGIN OF SPECIES 133

study of adaptations from all suspicion of triviality, for
no one before him had seen so clearly how all new
species arise by adaptation of pre-existing ones. It is
by adaptation that new forms of life arise ; it is inheri-
tance which preserves old ones.

Socrates, Swammerdam, and Paley had drawn from
the adaptations of nature proofs of the omnipotence
and beneficence of the Creator. Darwin, while ad-
mitting that every organism is exquisitely adapted to
its own mode of life, believed that the adaptations have
been perfected by slow degrees, and that they cannot
be proved to have been consciously devised. This
interpretation deprives the theologian of valued argu-
ments, but at the same time rids him of difficulties.
Even before Darwin's day some few natural theologians
had the courage to bring forward instances of the
harshness of nature. Kirby and Spence1 thought that
no injustice was done to certain predatory insects by
comparing them to devils. Others blessed the mercy
of heaven, which, after creating noxious animals,
created others to keep them in check. Darwin, when
reflecting upon the odious instincts which urge the
young cuckoo to eject its foster-brothers, some species
of ants to enslave others, and a multitude of ichneumons
to lay their eggs in the bodies of live caterpillars, found
it a relief to be able to shift the responsibility to an
unconscious natural process.2

In his autobiography Darwin remarks that he had
thought it almost useless to endeavour to prove by
indirect evidence that species had been modified until
he was able to show how the adaptations could be ex-
plained. Some of them alarmed him by their difficulty;

1 Introduction to Entomology, Introductory Letter.
a Life and Letters, Vol. L, chap. ii.

134 PERIOD V.

to suppose that the eye, with all its inimitable
adjustments, had been formed by an unconscious natural
process seemed to him absurd until he had traced a
good many intermediate steps between the mere colour-
spot and the eye of the eagle. He writes to Asa Gray
(September 5, 1857) that the facts which had done most
to keep him scientifically orthodox were facts of adapta-
tion, the pollen-masses of Asclepias, the mistletoe with
its pollen carried by insects and its seeds by birds, the
woodpecker exquisitely fitted by feet, tail, beak, and
tongue to climb trees and capture insects.

The student of adaptations has no longer a moral
thesis to maintain ; he tries to understand how a con-
trivance acts, what advantage it confers upon its
possessor, and by what steps it was perfected. The
minute variations of species are as capricious as the
form of the stones which accumulate at the foot of a
precipice ; natural selection turns fortuitous variations
to account for the advantage of the species as a builder
might turn to account the shapes of the stones. Man
himself can employ variations for frivolous or even base
purposes, as when he produces toy-spaniels or bull-
dogs.1 The adjustments of organic structures often
move our wonder by their perfection. One reason why
they so far exceed the adjustments made by wind, frost,
or moving water is that the process has been so pro-
tracted ; in a worm or an insect we see the last stage
of an adaptation which has been continuously at work
for untold geological periods. Another reason is that
the thing adapted is alive, sensitive, and capable of
responding to the subtlest imaginable influences.
; Darwinism and Non-biological Studies. — The theory

1 Darwin, Variation of Plants and Animals under Domestica-
tion, Concluding- Remarks.

DARWIN ON THE ORIGIN OF SPECIES 135

of organic evolution has already produced a visible
effect upon non-biological studies. Bagehot has applied
Darwinian principles to the interpretation of history
and politics. Philologists recognise a process very
like that of natural selection in the modification of
words. The usages of language are inherited from
generation to generation ; one idiom competes with
another, that persisting which best suits the temper
or the convenience of the nation. Philology has
like zoology its chains of descent, its breeds or
dialects, its species or languages, its fossils (dead
languages), its dominant and declining forms, its
vestiges (such as letters, still retained, though no
longer sounded). Psychology is already in part experi-
mental and evolutionary, and seems as if it would
attach itself more and more closely to physiology,
detaching itself in the same measure from metaphysics.
The change may be attributed to two growing convic-
tions : (i) That the experimental method is more trust-
worthy than the speculative ; and (2) that the mind of
man is not a thing apart, but an enhanced form of
powers manifest in the lower animals. Sociology finds
its most practicable and its most urgent sphere of work
in the problems of selection and race, which are
naturally examined in the light of Darwinian principles.
The new study of Comparative Religion aims at the
impartial examination of all forms of religious experience,
and is evolutionary in proportion as it is scientific. One
of its conclusions, by no means universally accepted as
yet, is the recognition of conscience as " the organised
result of the social experiences of many generations "
(Galton). Comparative Religion can already show in
outline how by slow degrees magical rites passed into
polytheistic worship, how polytheism became simplified

136 PERIOD V.

and elevated, and how ethical motives at length became
influential if not predominant.

Pasteur's Experimental Study of Microbes.

The same difficulty arises with Pasteur as with
Darwin ; his life-work has already been described often
and well. Readers unversed in science have only to
turn to the Vie de Pasteur^ written by his son-in-law,
Vallery-Radot, to find a luminous account, giving- just
so much detail as makes the discoveries intelligible and
interesting. If shorter sketches are demanded, they
exist. We must therefore above all things be brief,
and content ourselves with reminding the reader of
facts which, in spite of their recent date, are as well
known as anything in the history of science.

Chemists will claim Pasteur as one of their number,
and we do not dispute the claim. Trained in experi-
mental methods by the chemical laboratory, he devoted
his best powers to the study of living things, and, with-
out ceasing to be a chemist, became one of the greatest
of biologists.

Pasteur's chief work was of course the experimental
investigation of living particles which float in the air —
what we may call live dust. Before his day such
particles had been seen, named, and classified ; some
few had been studied in their action and effects. Most
of them are plants of low grade, simplified to the last
point for the sake of minuteness, on which their ready
dispersal depends.

Yeast. — Van Helmont, early in the seventeenth
century, when the microscope had not yet become an
instrument of research, attempted to investigate the
fermentation of beer, and made acquaintance with the
properties of the gas which is evolved, his gas silrvestre>

PASTEUR'S STUDY OF MICROBES 137

which was afterwards called fixed air, or carbonic acid.
Leeuwenhoek about 1680 examined yeast by his micro-
scopes, and discovered that it is made up of globules
which often cohere, and that these globules give off
bubbles of gas. Then comes a long interval, during
which nothing was done to elucidate the process of
fermentation. It was not till 1837 that Caignard-
Latour and Schwann, independently of each other,
showed that yeast-globules multiply by budding, and
are therefore to be set down as living things, probably
plants of a simple kind. Twenty years more passed
without sensible progress ; during this time chemists
were striving to prove that the alcohol was produced
by contact-action, and that the globules were of no
practical importance. By the year 1860 Pasteur was
engaged upon the problem. It is well known that he
arrived at a firm conviction that living yeast-cells are
essential to the production of alcohol. ,It has since
been discovered that the enzyme (unorganised ferment
of older writers) secreted by living yeast-cells can
change sugar into alcohol after the cells themselves
have been destroyed, and that other plants besides
yeast-cells secrete the same enzyme when deprived of
oxygen.

Bacteria. — Another and even more important chapter
in the history of air-wafted organisms was opened by
the indefatigable Leeuwenhoek. In 1683 he wrote a
letter to the Royal Society which makes mention for
the first time of bacteria, which he found upon his own
teeth, and described as minute rods ; some of them
moved with surprising agility. For nearly two hundred
years little more was done. A few bacteria were named
and classified, and there the matter rested until Schwann
proved experimentally that putrefaction is just as much

K

i38 PERIOD V.

the work of living- microscopic organisms as alcoholic
fermentation. In 1857 and the following years Pasteur
not only confirmed the work of Schwann, which had
been received by the majority of chemists with distrust,
but went on to show that the lactic, butyric, and
ammoniacal fermentations also depend upon the activity
of bacteria. The happy thought struck him that they
might be studied alive — a possibility which he soon
realised in practice, and upon which the new science of
bacteriology largely rests. From about the year 1873
he began to occupy himself seriously with contagion,
which he suspected to be connected with specific aerial
germs. Davaine and others had years before observed
in the blood of sheep and cattle which had died of
" charbon " (anthrax) minute " batonnets " (bacilli).
Pasteur's published results induced Davaine to ask
whether his " batonnets " might not be the cause of
"charbon." Again, it was Pasteur's results which
induced Lister to make experiments in the field of
antiseptic surgery. Pasteur wasted no time upon the
curiosities of bacterial life. His first studies on fermen-
tation suggested that specific diseases may be propa-
gated by microscopic germs, and that such cases of
spontaneous generation as had hitherto escaped refuta-
tion might be explained by the access of live dust.
The identification and biological history of the organisms
interested him only as a step towards sure methods of
controlling, and, if necessary, destroying, them ; of
mitigating their virulence by inoculation ; of rendering*
animals immune against them ; or of stamping out the
disease by isolation. All this is happily too well known
for repetition here. The story, with its many dramatic
incidents, can be read in the pages of Vallery-Radot.
Hardly less important than the bacteria which destroy

PASTEUR'S STUDY OF MICROBES 139

life or endanger the products of human industry are the
beneficent forms, some of which have in all ages co-
operated with man, while others can only be employed
by those who possess knowledge and skill. None are
so important to our welfare as the bacteria which renew
the fertility of the soil. But for the soil-bacteria farm-
yard manure would be useless to the crop, for it is
they which render it fit for assimilation. Now the
bacteria of the soil have their natural enemies, the most
mischievous being certain Protozoa, such as Amoeba
and its kindred. As soon as this fact was grasped,
likely remedies were thought of ; indeed, one remedy
was suggested without any guidance from theory by a
vine-grower of Alsace, who treated his soil with carbon
disulphide to destroy phylloxera, and found that in so
doing he had notably enhanced its fertility. Heating
to the temperature of boiling water destroys the soil-
protozoa and at the same time the bulk of the soil-
bacteria. The bacteria, however, soon multiply more
than ever by reason of the absence of their enemies,
and a soil cleared of protozoa yields for a few years
appreciably richer crops. Of other useful bacteria the
briefest notice must suffice. Wine, beer, cheese, and
tobacco owe to certain of them distinct flavours, for
which the customer is willing to pay high. Leather in
certain stages of manufacture, indigo, and woad require
the access of other forms. If we also bear in mind the
part which yeast plays in the every-day manufacture of
bread, wine, and beer, and the part which the vinegar-
mould plays in the manufacture of acetic acid, we shall
get some notion of the industrial importance of the
various micro-organisms. Not a little of the control
which we exercise over them we owe directly or in-
directly to Pasteur.

K 2

I4o PERIOD V.

The career of Pasteur exhibits a striking- unity. His
first research, which dealt with a subject so remote from
the ordinary studies of the biologist as the crystalline
forms of tartrates, made him acquainted with activities,
hitherto unsuspected, of minute forms of life. The hope
of aiding the industries of Lille, Orleans, and France
kept him long engaged upon ferments. If he turned
aside to examine the superstition of spontaneous genera-
tion, it was to protect his methods from misconstruction.
An apparent break in his programme of work was forced
upon him by the silkworm pestilence. It proved to be
no real break, for pebrine and flacherie were both bac-
terial diseases. At a comparatively early date (1863)
he wrote that his chief ambition was to throw light on
the spread of contagious diseases ; he could not then
foresee that he was destined, not only to elucidate, but
in a measure to control them. Around his tomb are
inscribed words, each of which commemorates a signal
service to his fellow-men : " 1848, Molecular dissymetry.
1857, Fermentations. 1862, Spontaneous generation.
1863, Studies of wine. 1865, Silkworm diseases. 1871,
Studies on beer. 1877, Contagious diseases of animals.
1880, Vaccination against contagious diseases. 1885,
Prevention of hydrophobia." These manifold researches
form a continuous chain, each being linked to what
precedes and follows. The devotion by which all were
inspired, beginning with devotion to science and the
fatherland, ended by embracing all mankind.

Biology, which in the sixteenth century sent out only
a few feeble shoots, has now become a mighty tree with
innumerable fruit-laden branches. The vigour of its
latest outgrowths encourages confident hopes of future
expansion.

CHRONOLOGICAL TABLE
1200-1850

(The date of a discovery is the date of first publication, where
this is known.)

1202. Arabic numeration introduced into Europe by

Leonardo of Pisa (Liber Abaci) ; it spread
slowly, and did not become universal till the
middle of the seventeenth century.

1214-1294. Roger Bacon.

1265-1321. Dante.

1271-1295. Travels of Marco Polo.

1304-1374. Petrarch.

1 324?-! 384. Wycliffe.

I34O?-I400. Chaucer.

1410. Wood-engraving introduced about this time.

1423. Earliest known block-book.

1450? Mazarin Bible, printed by moveable types.

1453. Taking of Constantinople by the Turks.

I4(56?-I536. Erasmus.

1471-1528. Albert Durer.

1472-1543. Copernicus.

1475-1564. Michael Angelo.

1477-1576. Titian.

1483-1520. Raphael.

1483-1546. Martin Luther.

1492. First voyage of Columbus.

1497-1498. Voyage of Vasco da Gama to India by the Cape.

1516. More's Utopia.

1517. Luther's theses.
1519-1521. Mexico conquered by Cortez.

1519-1522. Circumnavigation of the globe by a ship of
Magellan's squadron.
141

I42

CHRONOLOGICAL TABLE

1530-1536. Brunfels' Herbarum vivce eicones. Confession of

Augsburg.

1532. Peru conquered by Pizarro.

J534- Society of Jesus founded by Loyola.

I539- Bock's New Kreutterbuch (without figures) ;

2nd ed. (with figures) 1546.

1542. Fuchs' Historia Stirpium.

1543. Copernicus' De Revolutionibus Orbium Celestium.

Vesalius' Fabrica Humani Corporis.
1545. Botanic garden at Padua founded.

1545-1564. Council of Trent.
1547. Botanic garden at Pisa founded.

Belon's Histoire Naturelle des estranges poissons

marins.

Gesner's Historia Animalium.
Belon's De aquatilibus, etc., and his Observa-
tions de plusieurs singularitez > etc. (Travels
in the Levant.)

Rondelet's De piscibus marinis.
Belon's Histoire de la nature des Oyseaux.
Rondelet's Universes aquatilium Histories pars
altera.

Shakespeare.
Galileo.

Revolt of the Netherlands.
Battle of Lepanto (advance of the Turks

checked).
Kepler.

Massacre of St. Bartholomew.
L'Obel's Plantarum seu Stirpium Historia and

A dversaria.

Drake's circumnavigation.
I583- Cesalpini's De Plantis.

1588. The Invincible Armada.

1596-1650. Descartes.

1600. Olivier de Serres' Theatre d' Agriculture.

1601. Clusius' Rariorum plantarum Historia.
1605. Clusius' Exoticorum libri decem.

1553-

1554-
1555-

1564-1616.
1564-1642.
1566.

1572-
1576.

CHRONOLOGICAL TABLE 143

1610. Galileo's microscope invented about this time.

1614. Napier's Logarithms.
1618-1648. Thirty Years' War.

1620. Voyage of Mayflower. Bacon's Novum Organum.

1621. Aselli re-discovers the lacteals.
1623. C. Bauhin's Pinax Theatri Botanici.
1626. Jardin des Plantes founded.

1628. Harvey's De motu cordis et sanguinis published

the lectures had been delivered in 1614.

1635. French Academy founded.

1638. First authenticated cure of fever by chincona

bark (in Peru).

1642. New Zealand and Van Dieman's Land dis-

covered by Tasman.
1642-1727. Newton.

1643. Barometer invented by Torricelli.

1650 ? Air-pump invented by Otto von Guericke.

Thoracic duct discovered by Pecquet.
1653. Lymphatic vessels discovered by Rudbeck.

1660. Royal Society founded ; incorporated 1662.

Boyle's Spring of Air and its Effects. Ray's
Catalogue Plantarum circa Cantabrigiam
nascentium.

1661. Boyle's Sceptical Chemist. Passage of blood

through capillaries observed by Malpighi.

1665. Hooke's Micrographia.

1666. Academic des Sciences founded. Composition

of white light discovered by Newton.

1668. Redi on the Generation of Insects.

1669. Swammerdam's Historia Insectorum Generalis.

Malpighi 's De Bombyce.
1671-1677. Grew's Anatomy of Plants ; collected in one

volume, 1682.
1672-1679. Malpighi's Anatome Plantarum ; collected in his

Opera Omnia, 1686.
1673. Malpighi's De formatione pulli in ovo. Leeu-

wenhoek's first paper published by the Royal

Society.

144

CHRONOLOGICAL TABLE

1675. Greenwich Observatory founded. Velocity of

light determined by Roemer.

1676. Willughby's Ornithologia.

1677. Spermatozoa discovered by Hamm.
1680. Yeast-cells discovered by Leeuwenhoek.

1682. Ray's Methodus Plantarum.

1683. Bacteria discovered by Leeuwenhoek.
1687. Newton's Principia.

1691-1694. Camerarius on the sexes of flowering plants.
1702. Hydra discovered by Leeuwenhoek.

1711-1776. Hume.
1723-1790. Adam Smith.

Vice's Scienza Nuova.

Reaumur's Histoire des Insectes.
1736-1819. Watt.

1737. Linnaeus's Systema Natures; last edition by

Linnaeus, 1766. Linnaeus's Genera Plantarum.
1737-1738. Swammerdam's Biblia Natures published ;
written long before.

1738. Linnaeus's Classes Plantarum.

1740-1761. Roesel von Rosenhof's Insecten-Belustigungen
begun.

1744. Trembley's Polype d^eau douce (Hydra).

1745. Bonnet's Traite d^ Insectologie (aphids, Nais).
1748. Montesquieu's Esprit des Lois.

1749-1804. Buffon's Histoire Naturelle, the last volumes

posthumous.
1752. Identity of lightning and electricity demonstrated

by Franklin.

I753< British Museum founded.

1755. Black's experiments on carbonic acid and

alkalis.

1759. C. F. Wolff's Theoria Generationis.

1760. Lyonet's Trait6 Anatomique, etc. (larva of goat-

moth).

1770. New South Wales discovered by Captain Cook.

I775* Priestley's experiments on the restoration by

green leaves of air vitiated by combustion or

CHRONOLOGICAL TABLE 145

respiration, and on " dephlogisticated air"

(oxygen). Adam Smith's Wealth of Nations.
1777. Spallanzani's experiments on the spontaneous

generation of minute organisms.
1781. Uranus discovered by Herschel. Leroy's Lettres

surles Animaux (first collected edition).

1784, Cavendish's Experiments on A ir (composition of

water).

1785. Hutton's Theory of the Earth.

1787-1789. Lavoisier's Methode de nomenclature chimique
(1787) and Traite elementaire de chimie (1789).

1789. First French Revolution. A. L. de Jussieu's

Genera Plantarum. White's Natural History
of Selborne.

1790. Goethe's Metamorphosen der Pflanzen.

1791. Galvani's experiments on animal electricity.

1792. Sprengel's Entdeckte Geheimniss der Natur. F.

Huber's Nouvelles Observations sur les A beilles.
1796. Cuvier on recent and fossil elephants.

1798. Jenner's Inquiry (vaccination against small-pox).

Lithography invented by Senefelder.

1799. William Smith's Order of the Strata and their

Embedded Organic Remains.
1799-1825. Laplace's Mtcanique Celeste.

1800. Volta's electric pile.

1807. Dalton's Atomic theory. Davy's decomposition

of potash and soda.

1811. Motor and sensory roots of spinal nerves dis-

covered by Bell.

1812. Cuvier's Ossemens Fossiles.
1816. Cuvier's Regne Animal.

1819. Electro-magnetism discovered by CErsted.

Chamisso's De Salpa.
1823-1831. Pollen-tubes traced to the ovule (Amici, Brong-

niart, Robert Brown).

1827. Discovery of mammalian ovum by Baer.

1828-1837. Baer's Entwickelungs-geschichte.
1830-1832. Lyell's Principles of Geology.

i46

THE SUB-DIVISIONS OF BIOLOGY

1835. Cell-division in plants observed by Mohl.

1837. Caignard-Latour's demonstration that alcoholic

fermentation is due to living organisms.

1839. Schwann and Schleiden's ceH-theory.

1840-1849. Joule's determination of the mechanical equiva-
lent of heat.

1841. Faraday's discovery of electric induction.

1846. Discovery of Neptune by Leverrier and Adams.

Agassiz and Buckland's announcement of
extensive glaciation in Scotland.

1848. Discovery of the antheridia of ferns by Suminsky.

1849-1851. Hofmeister's comparative studies of the higher
cryptogams and the flowering plants.

1809-1882. Charles Darwin.
1822-1895. Louis Pasteur.

THE SUB-DIVISIONS OF BIOLOGY

Morphology :

Anatomy.

Minute Anatomy.

Comparative Anatomy.
Embryology.

Physiology (including adaptations to the conditions of life).
Psychology of Animals.
Classification.
Geographical Distribution.
Palaeontology.

All these divisions, except Psychology, apply both to plants
and animals. Many other modes of division have been
proposed.

BIBLIOGRAPHY

[It will be readily understood that the literature of Biology is
enormous, as a single fact will show. Half a century ago Dr.
Hagen compiled a list of books and papers relating to Ento-
mology alone. Though far from complete, it filled a thousand
pages, and if brought down to the present date would probably
fill a thousand more. The student who tries to follow in some
detail the history of any branch of Biology must read books in
half-a-dozen languages, and work continually in large public
libraries. We shall attempt no more in this place than to mention
a few books which can be procured and read by those whose
leisure and knowledge of the subject are limited.]

HISTORY OF BIOLOGY OR ITS SUB- DIVISIONS.
Carus, V. Geschichte der Zoologie. 1864 foil.

The French translation by Hagenmuller and Schneider
(1880) will be preferred by some.

Cuvier, G. Histoire des Sciences Nattirelles. Publie"e par
M. de Saint-Agy. Two vols., 1841. Taken down from
Cuvier's lectures, but not revised by him.

Though far from trustworthy (the first volume especially),
this history mentions many interesting facts, and suggests
inquiries which may be pursued with advantage.
Foster, Sir M. Lectures on the History of Physiology.
Cambridge Natural Science Manuals, 1901.

Green, J. R. History of Botany, 1860-1900. A continua-
tion of Sachs's History. Clarendon Press, 1909.

Sachs, J. History of Botany, 1530-60. English transla-
tion. Clarendon Press, 1889.

An outline of the History of Paleontology is prefixed to
Zittel's Handbuch der Palceontologie, Bd. I. (1876-80). English
translation, 1900-2.

The ninth edition of the Encyclop&dia Britannica often
contains useful references. See for example the articles
Biology, Embryology, Medicine, Parasitism, and Zoology.

Biographical dictionaries are of course indispensable.
The Dictionary of National Biography, the Biographic

'47

148 BIBLIOGRAPHY

Universelle, the Nou-velle Biographic Universelle, the Allge-
meine Deutsche Biographic, and the Biographie Nationale de
Belgique will be frequently consulted.

Among the old authors who can be read for pleasure as
well as for profit the present writer would include : —

Baker, H. The Microscope Made Easy. Second ed., 1743.
— Employment for the Microscope. 1753.

Belon, P. Observations de plusieurs singularitez et choses
memorables trouvees en Grece, Asie, Judee, Egypte, Arable, et
autres pays estranges. 1553.

Histoire de la nature des Oyseaux. 1555.

Buffon, Comte de. Histoire Naturelle. Forty-four vols.,
of which thirty-six appeared during Buffon's lifetime. 1749-
1804. Selected passages only.

Cuvier, G. Ossemens Fossiles. 1812. Fourth ed. in ten
vols., besides two of plates, 1834-36. Selected passages only.

Hooke, R. Micrographia. 1665.

Huber, F. NouveHes observations sur les Abeilles. 1792.
Second ed., two vols., 1814.

J. P. Recherches sur les mosurs des Fourmis indigenes.

1810.

Le Roy, G. Lettres sur les Animaux. 1781. Reprinted,
1862.

Linnaeus, C., and his Pupils. Amcenitates Academicce.
Seven vols., 1749-69.

Contain interesting- discussions here and there among
much that is now valueless.

Lachesis Lapponica ; or, A Tour in Lapland. Trans-
lated by Sir J. E. Smith from the original diary. Two vols.,
1811.

Ray, J. Catalogus Plantarum circa Cantabrigiam nascen-
tium. 1660.

Reaumur, R. A. F. de. Histoire des Insectes. Six vols.
1734-42.

Redi, F. Experiments on the Generation of Insects. Trans-
lated from the Italian edition of 1688 by Mab Bigelow.
Chicago, 1909.

Roesel von Rosenhof, A. J. Insecten-belustigungen. 1746-
61.

Turner, W. On Birds. 1544. Translated by A. H.
Evans, 1903.

INDEX

AFFINITY, 17, 51

Agassiz, 122

Albrecht, 61

Aldrovandi, 13

America, discovery of, 24, 112

Aristotle, 2, 16, 17 w., 30, 39, 45,

47' 63> 73. 102 n.
Aselli, 21

BACON, FRANCIS, 39

Roger, 28

Bacteria, 137

Baer, Von, 66, 102, 104, 121, 127

Bagehot, 135

Baker, 67, 69

Barry, 106

Belon, 13

Bernard of Breydenbach, 23

Bestiaries, 6, 23

Bichat, 105

Bock, 9, 12, 37, 124

Bonnet, 45, 60

Bonpland, 118

Bossuet, 66

Brown, 105 n.

Brunfels, 9, 12

Buffon, 40, 45, 63, 68, 71, 94 w.,

95, 120, 130
Busbecq, 113
Butler, 67

CAIGNARD-LATOUR, 137

Caius, 19, 67

Camerarius, 48

Gesalpini, 12, 17 «., 34, 37, 80,

85

Chamisso, 100
Charlemagne, 25
Clodd, 65 n.
Clusius, in, 113

Cole, 86
Compton, 116
Copernicus, 20

DARWIN, C., 46, 66, 75, 91, 92,

I2O, 121, 124
E., 120

Davaine, 138
Descartes, 69
Dioscorides, 4
Dumas, 106
Duverney, 36

ENCYCLOPAEDIC Naturalists, 12
Erasistratus, 4
Evelyn, in, 115, 116
Experiments of ancient Greeks,
3

FABRICIUS, 21
Fagon, 115
Flemings, 26
Fontana, 105 n.
Forbes, 131
Fries, 17
Frisch, 37, 67
Fuchs, 9, 12

GAERTNER, 86

Galen, 4, 21

Galileo, 28

Gallon, 63 n., 135

Geer, De, 37, 68

Gerarde, 20

Gesner, n, 13, 17 w., 18, 19, 20,

"3

Goethe, 80, 81, 84, 85
Greenhouses, 114
Grew, 32, 47, 86

149

INDEX

HALES, 68, 77

Hamm, 34

Harvey, 21, 102

Hedwig, 87

Heide, 37

Helmont, Van, 77, 136

Herophilus, 4

Hofmeister, 83,85, 108, 109, 122

Hooke, 29, 34, 37, 105

Hothouses, 114

Huber, 68, 77

Humboldt, 118

Hume, 72

Hutton, 66

INGENHOUSZ, 79

JUSSIEU, B. de, 51
A. L. de, 51

KANT, 120

King, 36

Kirby, 68

and Spence, 55, 133

LAMARCK, 46
Laplace, 120
Leeuvvenhoek, 32, 40, 58, 60, 68,

86, 1 06, 137
Leibnitz, 45, 64
Leroy, 68, 73
Lessing, 120
Lindsay, 86
Linnaeus, 48, 49, 52, 64, 80, 82,

85, 87, 90, 92, 124, 130
Lister, Lord, 138

M., 35, 43, 67

L'Obel, 12, 26, 124, 130
Locke, 70

Lyell, 66, 67, 94, 121
Lyonet, 34, 58, 60, 61, 67

MALPHIGHI, 32, 36, 40, 45, 47,

127

Marco Polo, 23
Master, 36
Mattioli, 113
Medicine and botany, 7
M6ry, 37, 38, 67

Micheli, 87
Microscope, 28, 48
Middle Ages, 5, 6, 25
Millington, 47
Mohl, 106
Montagu, 68
Montesquieu, 63, 120
Morgan, Lloyd, 74
Morison, 86
Moufet, 20

NEEDHAM, 40
Newton, 63

OLIVER and Scott, 83, 85
Ortus Sanitatis, 16

PALEY, 133

Palissy, 34

Pallas, 46

Parkinson, 20

Pasteur, 136

Pecquet, 22

Perrault, 36, 37, 67

Peter Martyr Anglerius, 24.

Physiologus, 6

Pliny, 5

Plumier, 115 n.

Pope, 45

Poupart, 37, 38, 67

PreVost, 106

Priestley, 77

Quackelbecn, 113

RATHKE, 104, 127

Ray, 17 n., 22, 35, 38, 41, 48, 68r

124
Reaumur, 37, 40, 54, 60, 64, 68,

70,87
Redi, 39
Rhineland, n
Roesel von Rosenhof, 67, 69,.

100

Rondelet, 13
Rudbeck, 22

SARS, 101
Saussure, De, 79

INDEX

Schleiden, 105
Scott and Oliver, 83, 85
Schwann, 105, 106, 137
Seneca, 28, 113
Serres, Olivier de, 26
Smith, 35
Socrates, 133
Spallanzani, 40
Spence, 68
Spencer, 122
Spreng-el, 89
Stenson, 34
Suminski, 108

Swammerdam, 29, 37, 38, 40, 70,
86, 103, 1 06, 133

THEOPHRASTUS, 2, 47
Titius, 124 n.
Tournefort, 38

Tradescant, 115
Trembley, 57
Turner, 18, 67
Tyson, 36

VALLISNIERI, 40
Vesalius, 20, 21
Vico, 63
Voltaire, 35

WALLACE, 120

Wallis, 22

White, 68

Wolff, 80, 82, 84, 85, 103

Woodward, 34

Wotton, 18

YEAST, 136

PRINTED BY WATTS AND CO., JOHNSON'S COURT, FLEET STREET, LONDON, E.C,

RETURN TO the circulation desk of any
University of California Library

or to the

NORTHERN REGIONAL LIBRARY FACILITY
Bldg. 400, Richmond Field Station
University of California
Richmond, CA 94804-4698

ALL BOOKS MAY BE RECALLED AFTER 7 DAYS

• 2-month loans may be renewed by calling
(510)642-6753

• 1-year loans may be recharged by bringing
books to NRLF

• Renewals and recharges may be made
4 days prior to due date

DUE AS STAMPED BELOW

rJUL 2 2 2004

DD20 15M 4-02

M 3655

-

r

BIOLOGY

LIBRARY

r,

THE UNIVERSITY OF CALIFORNIA LIBRARY

DARWINISM AND DARWIN1ANA

AUTOBIOGRAPHY OF
CHARLES DARWIN

With Appendices,
comprising

A CHAPTER OF REMINISCENCES

and

A STATEMENT OF
CHARLES DARWIN'S RELIGIOUS VIEWS,

by his Son,

SIR FRANCIS DARWIN
160 pp.; elothette, Is. net

TWO INVALUABLE WORKS

By Sir Arthur Keith, F.R.S.

DARWINISM fc? WHAT IT IMPLIES

Contents: — Implications of Darwinism (the Ludwig Moiu!

Lecture in the University of Manchester) ; Concerning the

Nature of Man's Brain ; Modern Critics of Evolution.

CONCERNING MAN'S ORIGIN

Contents: — The Presidential Address given at the Meeting
of the British Association, 1927 (How our modern concep-
tion of man's origin has come about ; Advances in our
Knowledg-e made since Darwin's Time ; The Machinery of
Man's Evolution) ; Further Evidence and Some Unsolved
Problems ; Darwin's Home ; Why I am a Darwinist ;
Capital as a Factor in Evolution.

Each volume 60 pp.; elothette, Is. net; paper cover, 7d. net

London : WATTS & CO., Johnson's Court, Fleet St., E.C-4