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Full text of "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. 



M v 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 learning 1 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 
among 1 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 Ray 1 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 nothing 1 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, rising 1 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 assuming 1 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 Ray 2 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 associating 1 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, forming 1 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. 

Baer 1 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. 



promising 1 , 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 Aristotle 2 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 
long 1 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 anecdote 1 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 Raumur,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., Mm. viii. 
9 Darwin, Origin of Species, chap. vii. 3 Vol. III., Mm. 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. 

Buffon 1 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 reasoning 1 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 long 1 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 
according 1 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 Scott 1 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. 



nothing 1 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 



io 4 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 bring 1 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 logician 1 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. 



i 3 o 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 Forbes 1 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 
workshops 2 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 Spence 1 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 sil r vestre > 



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 



i 3 8 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 



I 4 o 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 



I 4 2 



CHRONOLOGICAL TABLE 



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

Augsburg. 

1532. Peru conquered by Pizarro. 

J 534- Society of Jesus founded by Loyola. 

I 539- 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. 
I 583- 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. 

I 753 < 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. 

I 775* 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. 



i 4 6 



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' 6 3> 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, 68 r 

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 



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