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UNIVERSITY EXTENSION MANUALS
EDITED BY PROFESSOR KNIGHT

THE STUDY OF ANIMAL LIFE

EDITOR'S PREFACE

This Series is primarily designed to aid the University Extension
Movemetit throughout Great Britain, and to supply the need so
■widely felt by students, of Text-books for study and reference, in
connection with the authorised Courses of Lectures.

The Manuals differ from those already in existence in that they
are not intended for School use, or for Examination purposes ; and
that their aim is to educate, rather than to inform. The statement
of details is meant to illustrate the working of general laws, and the
development of principles ; while the historical evolution of the
subject dealt with is kept in view, along with its philosophical
significance.

The remarkable success which has attended University Extension
in Britain has been partly due to the combination of scientific treat-
ment with popularity, and to the union of simplicity with thorough-
ness. This movement, however, can only reach those resident in the
larger centres of population, while all over the country there are
thoughtful persons who desire the same kind of teaching. It is for
them also that this Series is designed. Its aim is to supply the
general reader with the same kind of teaching as is given in the
Lectures, and to reflect the spirit which has characterised the move-
ment, viz. the combination of principles with facts, and of methods
with results.

The Manuals are also intended to be contributions to the Literature
of the Subjects with which they respectively deal, quite apart from
University Extension ; a?id some of them will be found to meet a
general rather than a special want.

They will be issued simultaneously in England and America.
Volumes dealing with separate sections of Literature, Science,
Philosophy, History, and Art have been assigned to representative
literary men, to University Professors, or to Extension Lecturers
comiected with Oxford, Ca?nbridge, London, and the Universities of
Scotland and Ireland.

A list of the works in this Series will be found at the end of the
volume.

The Study

of

Animal Life

BY

J. ARTHUR THOMSON, M.A., F.R.S.E.

LECTURER ON ZOOLOGY, SCHOOL OF MEDICINE, EDINBURGU
JOINT-AUTHOR OF 1 THE EVOLUTION OF SEX ’

AUTHOR OF ‘OUTLINES OF ZOOLOGY’

SECOND EDITION

WITH ILLUSTRATIONS

LONDON

JOHN MURRAY, ALBEMARLE STREET

1892

" But, for my part, which write the English story, I acknowledge
that no man must looke for that at my hands, which I have not
received from some other : for I would bee unwilling to write anything
untrue, or uncertaine out of mine own invention ; and truth on every
part is so deare unto me, that I will not lie to bring any man in love
and admiration with God and his works, for God needeth not the lies
of men.'

Topsell's Apologia (1607).

PREFACE

This book is intended to help those who would study
animal life. From different points of view I have made
a series of sketches. I hope that when these are united
in the mind of the reader, the picture will have some
truth and beauty.

My chief desire has been to give the student some
impulse to joyousness of observation and freedom of
judgment, rather than to satisfy that thirst for knowledge
which leads many to intellectual insobriety. In pursu-
ance of one of the aims of this series, I have also tried
to show how our knowledge of animal life has grown,
and how much room there is for it still to grow.

A glance at the table of contents will show the plan
of the book ; first, the everyday life of animals, next, their
internal activities, thirdly, their forms and structure, and
finally, the theory of animal life. This is a commonly
accepted mode of treatment, and it is one by which it is
possible in different parts of the book to appeal to students
of different tastes. For, in lecturing to those who attend
University Extension Courses, I find that seniors are
most interested in the general problems of evolution,
heredity, and environment ; that others care more about
the actual forms of life and their structure ; that many
desire to have a clear understanding of the functions of
the animal body ; while most wish to study the ways of
living animals, their struggles and loves, their homes and

VI

Preface

societies. To each of these classes of students a quarter
of this volume is dedicated ; perhaps they will correct
their partiality by reading the whole.

As to the two Appendixes, I may explain that instead
of giving references at the end of each chapter, I have
combined these in a connected bibliography ; the other
Appendix on “ Animal Life and Ours ” may show how my
subject is related to some of the others usually discussed
in University Extension Courses.

My friend Mr. Norman Wyld has written the three
chapters on “ The Powers of Life,” pp. 1 2 5-166, and I am
also indebted to him for helpful suggestions in regard to
other parts of the book. I have to thank Mr. Murray,
Messrs. Chambers, and Mr. Walter Scott, for many of
the illustrations ; while several original drawings have
been made for me by my friend Mr. William Smith.

Professor Knight and Mr. John Murray have given
me many useful hints while the book was passing through
the press, and Mr. Ricardo Stephens was good enough
to read the proof sheets.

J. A. T.

School of Medicine,

Edinburgh, May 1892

CONTENTS

PART I

The Everyday Life of Animals

CHAPTER I

THE WEALTH OF LIFE

Variety of life — 2. Haunts of life — 3. Wealth of form — 4. Wealth
of numbers — 5. Wealth of beauty . . . Pages 1 -17

CHAPTER II

THE WEB OF LIFE

Dependence upon surroundings — 2. Inter-relations of plants and
animals — 3. Relation of animals to the earth — 4. Nutritive rela-
tions— 5. More complex interactions . . . 18-31

CHAPTER III

THE STRUGGLE OF LIFE

Nature and extent of the struggle — 2. Armour and weapons —
3. Different forms of struggle — 4. Cruelty of the struggle . 32-45

Vlll

Contents

PART i

CHAPTER IV

SHIFTS FOR A LIVING

i. Insulation — 2. Concealment — 3. Parasitism — 4. General resem-
blance to surroundings — 5. Variable colouring — 6. Rapid change
of colour — 7. Special protective resemblance — 8. Warning colours
— 9. Mimicry — 10. Masking — ix. Combination of advantageous
qualities — 12. Surrender of parts , . Pages 46-66

CHAPTER V

SOCIAL LIFE OF ANIMALS

i Partnerships — 2. Co-operation and division of labour — 3. Gre-
garious life and combined action — 4. Beavers — 5. Bees — 6. Ants
— 7. Termites — 8. Evolution of social life — 9. Advantages of
social life — 10. A note on "the social organism" — 11. Con-
clusions ....... 67-94

CHAPTER VI

THE DOMESTIC LIFE OF ANIMALS

I. The love of mates — 2. Love and care for offspring . 95-116

CHAPTER VII

THE INDUSTRIES OF ANIMALS

i. Hunting — 2. Shepherding— 3. Storing— 4. Making of homes —
5. Movements . 117-124

PART II

Contents

IX

PART II

The Powers of Life

CHAPTER VIII

VITALITY

i. The task of physiology — 2. The seat of life — 3. The energy of life —
4. Cells, the elements of life — 5. The machinery of life — 6. Proto-
plasm— 7. The chemical elements of life — 8. Growth — 9. Origin
of life . . . . . . Pages 125-142

CHAPTER IX

THE DIVIDED LABOURS OF THE BODY

1. Division of labour — 2. The functions of the body: Movement;
Nutrition ; Digestion; Absorption ; The work of the liver and
the kidneys; Respiration; Circulation; The changes within the
cells ; The activities of the nervous system — 3. Sketch of
Psychology ...... 143-152

CHAPTER X

INSTINCT

1. General usage of the term — 2. Careful usage of the term — 3.
Examples of instinct — 4. The origin of instinct . 153-166

X

Contents

PART III

PART III

The Forms of Animal Life

CHAPTER XI

THE ELEMENTS OF STRUCTURE

i. The resemblances and contrasts between plants and animals — 2.
The relation of the simplest animals to those which are more com-
plex— 3. The parts of the animal body , . Pages 167-183

CHAPTER XII

THE LIFE-HISTORY OF ANIMALS

1. Modes of reproductiofi — 2. Divergent modes — 3. Historical — 4. The
egg-cell or ovum — 5. The male-cell or spermatozoon — 6. Matura-
tion of the ovum — 7. Fertilisation — 8. Segmentation and the first
stages in development — 9. Some generalisations: the ovum
theory , the Gastrcea theory, fact of recapitulation, organic con-
tinuity . . . . . . . 184-203

CHAPTER XIII

THE PAST HISTORY OF ANIMALS

1. The two records — 2. Imperfection of the geological record — 3.
Palceontological series — 4. Extinction of types — 5. Various diffi-
culties— 6. Relative antiquity of animals . . 204-209

CHAPTER XIV

THE SIMPLEST ANIMALS

i. The simplest forms of life — 2. Survey of Protozoa — 3. The common
Amoeba — 4. Structure of the Protozoa — 5. Life of Protozoa — 6.
Psychical life of the Protozoa — 7. History of the Protozoa — 8. Rela-
tion to the earth — 9. Relation to other forms of life — 10. Relation
to man ...... 210-221

PART IV

Contents

xi

CHAPTER XV

BACKBONELESS ANIMALS

i. Sponges — 2. Stinging - animals or Ccelenterala — 3. “Worms" —
4. Echinoderms — 5. Arthropods — 6. Molluscs . Pages 222-247

CHAPTER XVI

BACKBONED ANIMALS

1. Balanoglossus — 2. Tunicates — 3. The Lancelet — 4. Round-mouths
or Cyclostomata — 5. Fishes — 6. Amphibians — 7- Reptiles — 8.
Birds — 9. Mammals ..... 248-272

PART IV

The Evolution of Animal Life

CHAPTER XVII

THE EVIDENCES OF EVOLUTION

1. The idea of evolution — 2. Arguments for evolution : Physiological ,
Morphological, Historical — 3. Origin of life . . 273-281

CHAPTER XVIII

THE EVOLUTION OF EVOLUTION THEORIES

1. Greek philosophers — 2. Aristotle — 3. Lucretius — 4. Evolutionists
before Darwin — 5. Three old masters : Buffon , Erasmus Darwin,
Lamarck — 6. Darwin — 7. Darwin's fellow - workers — 8. The
present state of opinion .... 282-302

CHAPTER XIX

THE INFLUENCE OF HABITS AND SURROUNDINGS

i. The influence of f unction — 2. The influence of surroundings — 3.
Our own environment ..... 303-319

Xll

Contents

PART IV

CHAPTER XX

HEREDITY

i. The facts of heredity — 2. Theories of heredity, historical retrospect —
3. The modem theory of heredity — 4. The inheritance of acquired
characters — 5. Social and ethical aspects — 6. Social inheritance

Pages 320-339

APPENDIX I

ANIMAL LIFE AND OURS

A. Our relation to animals : 1. Affinities and differences between man
and monkeys — 2. Descent of man — 3. Various opinions about the
descent of man — 4. Ancestors of man — 5. Possible factors in the
ascent of man. B. Our relation to Biology : 6. The utility of
science — 7. Practical justification of biology — 8. Intellectual
justification of biology . . . . . 340-350

APPENDIX II

SOME OF THE BEST BOOKS ON ANIMAL LIFE

A. Books on "Zoology"— B. Books on "Natural History" — C .Books
on "Biology" ..... 35I_369

Index

• 371-375

PART I

THE EVERYDAY LIFE OF ANIMALS
CHAPTER I

THE WEALTH OF LIFE

i. Variety of Life — 2. Haunts of Life — 3. Wealth of Form —

4. Wealth of Numbers — 5. Wealth of Beauty

The first steps towards an appreciation of animal life must
be taken by the student himself, for no book-lore can take
the place of actual observation. The student must wash
the quartz and dig for the diamonds, though a book may
help him to find these, and thereafter to fashion them into
a treasure.

Happily, however, the raw material of observation is not
rare like gold or diamonds, but near to us as sunshine and
rain-drops. Within a few hours’ walk of even the largest
of our towns the country is open and the animals are at
home. Though we may not be able to see “ the buzzard
homing herself in the sky, the snake sliding through
creepers and logs, the elk taking to the inner passes of
the woods, or the razor -billed auk sailing far north to
Labrador,” we can watch our own delightful birds building
their “homes without hands,” we can study the frogs from
the time that they trumpet in the early spring till they or
their offspring seek winter quarters in the mud, we can
follow the bees and detect their adroit burglary of the

B

PART I

3 The Study of Animal Life

flowers. And if we are discontented with our opportunities,
let us read Gilbert White’s History of Selborne, or how
Darwin watched earthworms for half a lifetime, or how
Richard Jefferies saw in the fields and hedgerows of Wilt-
shire a vision of nature, which seemed every year to grow
richer in beauty and marvel. It is thus that the study
of Natural History should begin, as it does naturally begin
in childhood, and as it began long before there was
any exact Zoology, — with the observation of animal life in
its familiar forms. The country schoolboy, who watches
the squirrels hide the beech nuts and pokes the hedgehog
into a living ball, who finds the nest of the lapwings,
though they decoy him away with prayerful cries, who
catches the speckled trout in spite of all their caution, and
laughs at the ants as they expend hours of labour on booty
not worth the having, is laying the foundation of a naturalist’s
education, which, though he may never build upon it, is
certainly the surest. For it is in such studies that we get
close to life, that we may come to know nature as a friend,
that we may even hear the solemn beating of her heart.

The same truth has been vividly expressed by one
whose own life-work shows that thoroughness as a zoologist
is consistent with enthusiasm for open-air natural history.
Of the country lad Dr. C. T. Hudson says, in a Presi-
dential Address to the Royal Microscopical Society, that he
“wanders among fields and hedges, by moor and river, sea-
washed cliff and shore, learning zoology as he learnt his
native tongue, not in paradigms and rules, but from Mother
Nature’s own lips. He knows the birds by their flight and
(still rarer accomplishment) by their cries. He has never
heard of (Edicnemus crepitans , the Charadrius pluvialis, or
the Squatarola cinerca, but he can find a plover’s nest, and
has seen the young brown peewits peering at him from
behind their protecting clods. He has watched the cun-
ning flycatcher leaving her obvious and yet invisible young
in a hole in an old wall, while she carries off the pellets
that might betray their presence ; and has stood so still to
see the male redstart that a field-mouse has curjed itself on
his warm foot and gone to sleep.”

CHAP. I

3

The Wealth of Life

But the student must also attempt more careful studies
of living animals, for it: is easy to remain satisfied with
vague “general impressions.” He should make for himself
— to be corrected afterwards by the labours of others — a
“Fauna” and “Flora” of the district, or a “Naturalist’s
Year Book” of the flow and ebb of the living tide. He
should select some nook or pool for special study, seeking
a more and more intimate acquaintance with its tenants,
watching them first and using the eyes of other students
afterwards. Nor is there any difficulty in keeping at least
freshwater aquaria — simply glass globes with pond water
and weeds — in which, within small compass, much wealth
of life may be observed. Those students are specially
fortunate who have within reach such collections as the
Zoological Gardens and the British Museum in London ;
but this is no reason for failing to appreciate the life of the
sea-shore, the moor-pond, and the woods, or for neglecting
to gain the confidence of fishermen and gamekeepers, or
of any whose knowledge of natural history has been gathered
from the experience of their daily life.

1. Variety of Life. — Between one form of life and another
'there often seems nothing in common save that both are
alive. Thus life is characteristically asleep in plants, it is
generally more or less awake in animals. Yet among the
latter, does it not doze in the tortoise, does it not fever in
the hot-blooded bird ? Or contrast the phlegmatic am-
phibian and the lithe fish, the limpet on the rock and the
energetic squid, the barnacle passively pendent on the float-
ing log and the frolicsome shrimp, the cochineal insect like
a gall upon the leaf and the busy bee, the sedentaiy corals
and the free-swimming jellyfish, the sponge on the rock
and the minute Night-Light Infusorians which make the
waves sparkle in the summer darkness. No genie of Oriental
fancy was more protean than the reality behind the myth
— the activity of life.

2. Haunts of Life. — The variety of haunt and home
is not less striking. There is the great and wide sea with
swimming things innumerable, our modem giants the whales,
the seals and walruses and the sluggish sea-cows, the flip-

4 The Study of Animal Life part i

pered penguins and Mother Carey’s chickens, the marine
turtles and swift poisonous sea-serpents, the true fishes in
prolific shoals, the cuttles and other pelagic molluscs ;
besides hosts of armoured crustaceans, swiftly-gliding
worms, fleets of Portuguese Men-of-War and throbbing jelly-
fish, and minute forms of life as numerous in the waves as
motes in the sunlit air of a dusty town.

“ But what an endless worke have I in hand,

To count the seas abundant progeny,

Whose fruitful seede favre passeth those on land,

And also those which wonne in th’ azure sky ;

For much more eath to tell the starres on hy,

Albe they endlesse seem in estimation,

Then to recount the seas posterity ;

So fertile be the flouds in generation,

So huge their numbers, and so numberlesse their nation.”

Realise Walt Whitman’s vivid picture : —

“ The World below the brine.

Forests at the bottom of the sea — the branches and leaves,

Sea-lettuce, vast lichens, strange flowers and seeds — the thick
tangle, the openings, and the pink turf,

Different colours, pale grey and green, purple, white, and gold —
the play of light through the water,

Dumb swimmers there among the rocks — coral, gluten, grass,
rushes — and the aliment of the swimmers,

Sluggish existences grazing there, suspended, or slowly crawling
close to the bottom :

The sperm-whale at the surface, blowing air and spray, or dis-
porting with his flukes,

The leaden-eyed shark, the walrus, the turtle, the hairy sea-
leopard, and the sting ray.

Passions there, wars, pursuits, tribes — sight in those ocean depths
— breathing that thick breathing air, as so many do.”

The sea appears to have been the cradle, if not the
birthplace, of the earliest forms of animal life, and some
have never wandered out of hearing of its lullaby. From
the sea, animals seem to have migrated to the shore and
thence to the land, but also to the great depths. Of the
life of the deep sea we have had certain knowledge only

CHAP. I

The Wealth of Life

5

Fia. i.— Suggestion of dccp-sca life. (In part from a figure by W. Marshall.)

6

PART I

The Study of Animal Life

within the last quarter of a century, since the Challenger
expedition (1872-76), under Sir Wyville Thomson’s leader-
ship, following the suggestions gained during the laying of the
Atlantic cables and the tentative voyages of the Lightning
(1868) and the Porcupine (1870), revealed what was
virtually a new world. During 3J years the Challenger
explorers cruised over 68,900 nautical miles, reached with
the long arm of the dredge to depths equal to reversed
Himalayas, raised sunken treasures of life from over 300
stations, and brought home spoils which for about twenty
years have kept the savants of Europe at work, the results
of which, under Dr. John Murray’s editorship, form a
library of about forty huge volumes. The discovery of this
new world has not only yielded rich treasures of knowledge,
but has raised a wave of wider than national enthusiasm
which has not since died away.

We are at present mainly interested in the general
picture which the results of these deep-sea explorations
present, — -of a thickly-peopled region far removed from
direct observation, sometimes three to five miles beneath
the surface — a world of darkness relieved only by the living-
lamps of phosphorescence, of silent calm in which animals
grow into quaint forms of great uniformity throughout wide
areas, and moreover a cold and plantless world in which
the animals have it all their own way, feeding, though
apparently without much struggle for existence, on their
numerous neighbours, and ultimately upon the small organ-
isms which in dying sink gently from the surface like snow-
flakes through the air.

Far otherwise is it on the shore — sunlight and freshening
waves, continual changes of time and tide, abundant plants,
crowds of animals, and a scrimmage for food. The shore
is one of the great battlefields of life on which, through
campaign after campaign, animals have sharpened one
another’s wits. It has been for untold ages a great school.

Leaving the sea-shore, the student might naturally seek
to trace a migration of animals from sea to estuary, and
from the brackish water to river and lake. But this path,
though followed by some animals, does not seem to have

CHAP. I

The Wealth of Life

7

been that which led to the establishment of the greater part
of our freshwater fauna. Professor Sollas has shown with
much conclusiveness that the conversion of comparatively
shallow continental seas into freshwater lakes has taken
place on a large scale several times in the history of the
earth. This has been in all likelihood accompanied by the
transformation of marine into freshwater species. It is
thus, we believe, that our lakes and rivers were first peopled.
Many freshwater forms differ from their marine relatives in
having suppressed the obviously hazardous free-swimming
juvenile stages, in bearing young which are sedentary or in
some way saved from being washed away by river currents.
Minute and lowly, but marvellously entrancing, are
numerous Rotifers, of which we know much through the
labours of Hudson and Gosse. These minute forms are
among the most abundant tenants of fresh water, and their
eggs are carried from one watershed to another on the
wings of the wind and on the feet of birds, so that the same
kinds may be found in widely separate waters. Let us
see them in the halo of Hudson’s eulogy: “To gaze into
that wonderful world which lies in a drop of water, crossed
by some atoms of green weed ; to see transparent living
mechanism at work, and to gain some idea of its modes of
action ; to watch a tiny speck that can sail through the
prick of a needle’s point ; to see its crystal armour flashing
with ever-varying tints, its head glorious with the halo of its
quivering cilia ; to see it gliding through the emerald
stems, hunting for its food, snatching at its prey, fleeing
from its enemy, chasing its mate (the fiercest of our
passions blazing in an invisible speck) ; to see it whirling
in a mad dance to the sound of its own music — the music of
its happiness, the exquisite happiness of living, — can any
one who has once enjoyed this sight, ever turn from it to
mere books and drawings, without the sense that he has
left all fairyland behind him?” Not less lively than the
Rotifers are crowds of minute crustaceans or water-fleas
which row swiftly through the clear water, and are eaten in
hundreds by the fishes. But there are higher forms still :
crayfish, and the larvae of mayflies and dragonflies, mussels

8

PART I

The Study of Animal Life

and water-snails, fishes and newts, the dipper and the king-
fisher, the otter and the vole.

As we review the series of animals from the simplest
upwards, we find a gradual increase in the number of
those which live on land. The lowest animals are mostly
aquatic — the sponges and stinging-animals wholly so ;
worm-like forms which are truly terrestrial are few com-
pared with those in water ; the members of the starfish
group are wholly marine ; among crustaceans, the wood-
lice, the land-crabs, and a few dwellers on the land, are
in a small minority ; among centipedes, insects, and spiders
the aquatic forms are quite exceptional ; and while the great
majority of molluscs live in water, the terrestrial snails and
slugs are legion. In the series of backboned animals,
again, the lowest forms are wholly aquatic ; an occasional
fish like the climbing- perch is able to live for a time
ashore ; the mud-fish, which can survive being brought from
Africa to Europe within its dry “ nest ” of mud, has learned
to breathe in air as well as in water ; the amphibians really
mark the transition from water to dry land, and usually
rehearse the story in each individual life as they grow from
fish-like tadpoles into frog- or newt-like adults. Among
reptiles, however, begins that possession of the earth, which
in mammals is established and secure. As insects among
the backboneless, so birds among the backboned, possess the
air, achieving in perfection what flying fish, swooping tree-
frogs and lizards, and above all the ancient and extinct
flying reptiles, have reached towards. Interesting, too, are
the exceptions — ostriches and penguins, whales and bats, the
various animals which have become burrowers, the dwellers
in caves, and the thievish parasites.

But it is enough to emphasise the fact of a general ascent
from sea to shore, from shore to dry land, and eventually
into the air, and the fact that the haunts and homes of animals
are not less varied than the pitch of their life.

3. Wealth of Form. — As our observations accumulate,
the desire for order asserts itself, and we should at first
classify for ourselves, like the savage before us, allowing
similar impressions to draw together into groups, such as

CIIAP. I The Wealth of Life 9

birds and beasts, fishes and worms. At first sight the types
of architecture seem confusingly numerous, but gradually
certain great samenesses are discerned. Thus we distin-
guish as higher animals those which have a supporting rod
along the back, and a nerve cord lying above this ; while
the lower animals have no such supporting rod, and have
their nerve-cord (when present) on the under, not on the
upper side of the body. The higher or backboned series
has its double climax in the Birds and the furred Mammals.
Indissolubly linked to the Birds are the Reptiles, — lizards
and snakes, tortoises and crocodiles — the survivors of a
great series of ancient forms, from among which Birds, and
perhaps Mammals also, long ago arose. Simpler in many
ways, as in bones and brains, are Amphibians and Fishes in
close structural alliance, with the strange double-breathing,
gill- and lung-possessing mud-fishes as links between them.
Far more old-fashioned than Fishes, though popularly in-
cluded along with them, are the Round-mouths — the half-
parasitic hag-fish, and the palatable lampreys, with quaint
young sometimes called “nine-eyes.” Near the base of
this series is the lancelet, a small, almost translucent
animal living in the sea-sand at considerable depths.
It may be regarded as a far-off prophecy of a fish.
Just at the threshold of the higher school of life, the
sea-squirts or Tunicates have for the most part stumbled ;
for though the active young forms have been acknowledged
for many years as reputable Vertebrates, almost all the
adults fall from this estate, and become so degenerate that
no zoologist ignorant of their life-history would recognise
their true position. Below this come certain claimants for
Vertebrate distinction, notably one Balanoglossus, a worm-
like animal, idolised by modern zoology as a connecting link
between the backboned and backboneless series, and
reminding us that exact boundary-lines are very rare in
nature. For our present purpose it is immaterial whether
this strange animal be a worm -like vertebrate or a
vertebrate-like worm.

Across the line, among the backboneless animals, it
is more difficult to distinguish successive grades of higher

i O The Study of Animal Life part i

and lower, for the various classes have progressed in very
different directions. We may liken the series to a school
in which graded standards have given place to classes which
have “ specialised ” in diverse studies ; or to a tree whose
branches, though originating at different levels, are all strong
and perfect. Of the shelled animals or Molluscs there
are three great sub -classes, (a) the cuttlefishes and the
pearly nautilus, (b) the snails and slugs, both terrestrial and
aquatic, and ( c ) the bivalves, such as cockle and mussel,
oyster and clam. Simpler than all these are a few forms
which link molluscs to worms.

Clad in armour of a very different type from the shells
of most Molluscs are the jointed-footed animals or Arthro-
pods, including on the one hand the almost exclusively
aquatic crustaceans, crabs and lobsters, barnacles and
“ water-fleas,” and on the other hand the almost exclusively
aerial or terrestrial spiders and scorpions, insects and centi-
pedes, besides quaint allies like the “king-crab,” the last of
a strong race. Again a connecting link demands special
notice, Peripatus by name, a caterpillar- or worm- like
Arthropod, breathing with the air- tubes of an insect or
centipede, getting rid of its waste-products with the kidneys
of a worm. It seems indeed like “a surviving descendant
of the literal father of flies,” and suggests forcibly that
insects rose on wings from an ancestry of worms much as
birds did from the reptile stock.

Very different from all these are the starfishes, brittle-
stars, feather-stars, sea-urchins, and sea-cucumbers, animals
mostly sluggish and calcareous, deserving their title of
thorny-skinned or Echinodermata. Here again, moreover,
the sea-cucumbers or Holothurians exhibit features which
suggest that this class also originated from among
“ worms.”

But “ Worms ” form a vast heterogeneous “ mob,” heart-
breaking to those who love order. No zoologist ever speaks
of them now as a “ class ” ; the title includes many classes,
bristly sea-worms and the familiar earthworms, smooth
suctorial leeches, ribbon-worms or Nemerteans, round hair-
worms or Nematodes, flat tapeworms and flukes, and many

CHAP. I

The Wealth of Life n

others with hardly any characters in common. To us these
many kinds of “ worms ” are full of interest, because in the
past they must have been rich in progress, and zoologists
find among them the bases of the other great branches —
Vertebrates, Molluscs, Arthropods, and Echinoderms.
“Worms” lie in a central (and still muddy) pool, from
which flow many streams.

Lower still, and in marked contrast to the rest, are the
Stinging-animals, such as jellyfish throbbing in the tide,
zoophytes clustering like plants on the rocks, sea-anemones
like bright flowers, corals half-smothered with lime. In the
Sponges the type of architecture is often very hard to find.
They form a branch of the tree of life which has many
beautiful leaves, but has never risen far.

Beyond this our unaided eyes will hardly lead us, yet
the pond-water held between us and the light shows vague
specks like living motes, the firstlings of life, the simplest
animals or Protozoa, almost all of which have remained mere
unit specks of living matter.

It is easy to write this catalogue of the chief forms of
life, and yet easier to read it : to have the tree of life as a
living picture is an achievement. It is worth while to
think and dream over a bird’s-eye view of the animal king-
dom— to secure representative specimens, to arrange them
in a suitably shelved cupboard, so that the outlines of the
picture may become clear in the mind. The arrangement
of animals on a genealogical or pedigree tree, which
Haeckel first suggested, may be readily abused, but it has
its value in presenting a vivid image of the organic unity
of the animal kingdom.

If the catalogue be thus realised, if the foliage come to
represent animals actually known, and if an attempt be
made to learn the exact nature, limits, and meaning of the
several branches, the student has made one of the most
important steps in the study of animal life. Much will
remain indeed — to connect the living twigs with those whose
leaves fell off ages ago, to understand the continual renewal
of the foliage by the birth of new leaves, and finally to
understand how the entire tree of life grew to be what it is.

12

The Study of Animal Life

PART I

Pig. 2 - Genealogical Tree

"Fig. 2 — „ «

16 Tl andl'fndicare .ta’JSSS and

nodon or Hatlfria respectively-

Snakes k

CHAP. I The Wealth of Life 13

There is of course no doubt as to the fact that some forms
of life are more complex than others. It requires no faith
to allow that the firstlings or Protozoa are simpler than
all the rest ; that sponges, which are more or less loose
colonies of unit masses imperfectly compacted together, are
in that sense simpler than jellyfish, and so on. The animals
most like ourselves are more intricate and more perfectly
controlled organisms than those which are obviously more
remote, and associated with this perfecting of structure there
is an increasing fulness and freedom of life.

We may arrange all the classes in series from low to high,
from simple to complex, but this will express only our most
generalised conceptions. For within each class there is
great variety, each has its own masterpieces. Thus the
simplest animals are often cased in shells of flint or lime
whose crystalline architecture has great complexity. The
simplest sponge is little more than a double-walled sack
riddled by pores through which the water is lashed, but
the Venus’ Flower-Basket ( Euplectella ), one of the flinty
sponges, has a complex system of water canals and a
skeleton of flinty threads built up into a framework of
marvellous intricacy and grace. The lowest insect is not
much more intricate, centralised, or controlled than many
a worm of the sea-shore, but the ant or the bee is a very
complex self-controlled organism. More exact, therefore,
than any linear series, is the image of a tree with branches
springing from different levels, each branch again bearing
twigs some of which rise higher than the base of the branch
above. A perfect scheme of this sort might not only express
the facts of structure, it might also express our notions of
the blood-relationships of animals and the way in which we
believe that different forms have arisen.

But the wealth of form is less varied than at first sight
appears. There is great wealth, but the coinage is very
uniform. Our first impression is one of manifold variety ;
but that gives place to one of marvellous plasticity when
we see how structures apparently quite different are redu-
cible to the same general plan. Thus, as the poet Goethe
first clearly showed, the seed-leaves, root-leaves, stem-leaves,

14 The Study of Animal Life part i

and even the parts of the flower — sepals, petals, stamens,
and carpels, are in reality all leaves or appendages more
or less modified for diverse work. The mouth-parts of a
lobster are masticating legs, and a bird’s wing is a modified
arm. The old naturalists were so far right in insisting on
the fact of a few great types. Nature, Lamarck said, is
never brusque ; nor is she inventive so much as adaptive.

4. Wealth of Numbers. — Large numbers are so unthink-
able, and accuracy in census-taking is so difficult, that we
need say little as to the number of different animals. The
census includes far over a million living species — a total so
vast that, so far as our power of realising it is concerned,
it is hardly affected when we admit that more than half
are insects. To these recorded myriads, moreover, many
newly-discovered forms are added every year — now by the
individual workers who with fresh eye or improved micro-
scope find in wayside pond or shore pool some new thing,
or again by great enterprises like the Challenger expedition.
Exploring naturalists like Wallace and Semper return from
tropical countries enriched with new animals from the dense
forests or warm seas. Zoological Stations, notably that of
Naples, are “register-houses” for the fauna of the neigh-
bouring sea, not merely as to number and form, but in
many cases taking account of life and history as well. Nor
can we forget the stupendous roll of the extinct, to which
the zoological historians continue to add as they disentomb
primitive mammals, toothed birds, giant reptiles, huge
amphibians, armoured fishes, gigantic cuttles, and a vast
multitude of strange forms, the like of which no longer
live. The length of the Zoological Record , in which the
literature and discoveries of each year are chronicled, the
portentous size of a volume which professes to discuss with
some completeness even a single sub-class, the number of
special departments into which the science of zoology is
divided, suggest the vast wealth of numbers at first sight so
bewildering. More than two thousand years ago Aristotle
recorded a total of about 500 forms, but more new species may
be described in a single volume of the Challenger Reports.
We speak about the number of the stars, yet more than one

CHAP. I

J5

The Wealth of Life

family of insects is credited with including as many different
species as there are stars to count on a clear night. But far
better than any literary attempt to estimate the numerical
wealth of life is some practical observation, some attempted
enumeration of the inmates of your aquarium, of the tenants
of some pool, or of the visitors to some meadow. The
naturalist as well as the poet spoke when Goethe celebrated
Nature’s wealth : “ In floods of life, in a storm of activity,
she moves and works above and beneath, working and
weaving, an endless motion, birth and death, an infinite
ocean, a changeful web, a glowing life ; she plies at the
roaring loom of time and weaves a living garment for God.”

5. Wealth of Beauty. — To many, however, animal life
is impressive not so much because of its amazing variety
and numerical greatness, nor because of its intellectual
suggestiveness and practical utility, but chiefly on account
of its beauty. This is to be seen and felt rather than
described or talked about.

The beauty of animals, in which we all delight, is usually
in form, or in colour, or in movement. Especially in the
simplest animals, the beauty of form is often comparable to
that of crystals ; witness the marvellous architecture in flint
and lime exhibited by the marine Protozoa, whose empty
shells form the ooze of the great depths. In higher animals
also an almost crystalline exactness of symmetry is often
apparent, but we find more frequent illustration of graceful
curves in form and feature, resulting in part from strenuous
and healthful exercise, which moulds the body into beauty.

Not a little of the colour of animals is due to the
physical nature of the skin, which is often iridescent ;
much, on the other hand, is due to the possession of pig-
ments, which may either be of the nature of reserve-products,
and then equivalent, let us say, to jewels, or of the nature of
waste-products, and thus a literal “beauty for ashes.” It
is often supposed that plants excel animals in colour, but
alike in the number and variety of pigments the reverse is
true. Then as to movement, how much there is to admire ;
the birds soaring, hovering, gliding, and diving; the monkey’s
gymnastics ; the bat’s arbitrary evolutions ; the grace of the

PART I

1 6 The Study of Animal Life

•

fleet stag ; the dolphin gamboling in the waves ; the lithe
lizards which flash across the path and are gone, and the
snake flowing like a silver river ; the buoyant swimming of
fishes and all manner of aquatic animals ; the lobster darting
backwards with a powerful tail-stroke across the pool ; the
butterflies flitting like sunbeams among the flowers. But

Fig. 3. — Humming-birds ( Florisuga mellivora) visiting flowers. (From Belt.)

are not all the delights of form and colour and movement
expressed in the songs of the birds in spring ?

I am quite willing to allow that this beauty is in one
sense a relative quality, varying with the surroundings
and education, and even ancestral history, of those who
appreciate it. A flower which seems beautiful to a bee
may be unattractive to a bird, a bird may choose her mate
for qualities by no means winsome to human eyes, and a

CHAP. I

The Wealth of Life

i7

dog may howl painfully at our sweet music. We call the
apple - blossom and the butterfly’s wings beautiful, partly
because the rays of light, borne from them to our eyes,
cause a pleasantly harmonious activity in our brains, partly
because this awakens reminiscences of past pleasant experi-
ences, partly for subtler reasons. Still, all healthy organisms
are harmonious in form, and seldom if ever are their colours
out of tone with their surroundings or with each other, — a
fact which suggests the truth of the Platonic conception that
a living creature- is harmonious because it is possessed by
a single soul, the realisation of a single idea.

The plants which seem to many eyes to have least
beauty are those which have been deformed or discoloured
by cultivation, or taken altogether out of their natural set-
ting ; the only ugly animals are the products of domestica-
tion and human interference on the one hand, or of disease
on the other ; and the ugliest things are what may be called
the excretions of civilisation, which are certainly not beauty
for ashes, but productions by which the hues and colours of
nature have been destroyed or smothered, where the natural
harmony has been forcibly put out of tune — in short, where
a vicious taste has insisted on becoming inventive.

c

CHAPTER II

THE WEB OF LIFE

I. Dependence upon Surroundings — 2. Inter-relations of Plants and
Animals — 3. Relation of Animals to the Earth — 4. Nutritive
Relations — 5- More Complex Interactiotis

In the filmy web of the spider, threads delicate but firm
bind part to part, so that the whole system is made one.
The quivering fly entangled in a corner betrays itself
throughout the web ; often it is felt rather than seen by the
lurking spinner. So in the substantial fabric of the world
part is bound to part. In wind and weather, or in the
business of our life, we are daily made aware of results
whose first conditions are remote, and chains of influence
not difficult to demonstrate link man to beast, and flower to
insect. The more we know of our suiTOundings, the more
we realise the fact that nature is a vast system of linkages,
that isolation is impossible.

1. Dependence upon Surroundings. — Every living body
is built up of various arrangements of at least twelve
“elements,” viz. Oxygen, Hydrogen, Carbon, Nitrogen,
Chlorine, Phosphorus, Sulphur, Magnesium, Calcium, Pot-
assium, Sodium, and Iron. All these elements are spread
throughout the whole world. By the magic touch of life
they are built up into substances of great complexity and
instability, substances very sensitive to impulses from, or
changes in, their surroundings. It may be that living matter
differs from dead matter in no other way than this. The

CHAP. II

19

Tiie Web of Life

varied forms of life crystallise out of their amorphous
beginnings in a manner that we conceive to be analogous to
the growth of a crystal within its solution. Further, we do
not believe in a “ vital force.” The movements of living
things are, like the movements of all matter, the expression
of the world’s energy, and illustrate the same laws. But
to these matters we shall return in another chapter.

Interesting, because of its sharply defined and far-reaching
significance, and because the essential mass is so nearly
infinitesimal, is the part played by iron in the story of life. F or
food-supply we are dependent upon animals and plants, and
ultimately upon plants. But these cannot produce their
valuable food-stuffs without the green colouring-matter in
their leaves, by help of which they are able to utilise the
energy of sunshine and the carbonic acid gas of the air.
But this important green pigment (though itself perhaps
free from any iron) cannot be formed in the plant unless
there be, as there almost always is, some iron in the soil.
Thus our whole life is based on iron. And all our supplies
of energy, our powers of doing work either with our own
hands and brains, or by the use of animals, or through the
application of steam, are traceable — if we follow them far
enough — to the sun, which is thus the source of the energy
in all creatures.

2. Inter-relations of Plants and Animals. — We often
hear of the “ balance of nature,” a phrase of wide appli-
cation, but very generally used to describe the mutual
dependence of plants and animals. Every one will allow
that most animals are more active than most plants,
that the life of the former is on an average more intense
and rapid than that of the latter. For all typical plants
the materials and conditions of nutrition are found in water
and salts absorbed by the roots, in carbonic acid gas
absorbed by the leaves from the air, and in the energy of
the sunlight which shines on the living matter through a
screen of green pigment. Plants feed on very simple sub-
stances, at a low chemical level, and their most char-
acteristic transformation of energy is that by which the
kinetic energy of the sunlight is changed into the potential

20

PART I

The Study of Animal Life

energy of the complex stuffs which animals eat or which
we use as fuel. But animals feed on plants or on creatures
like themselves, and are thus saved the expense of build-
ing up food -stuffs from crude materials. Their most
characteristic transformation of energy is that by which the
power of complex chemical substances is used in locomotion
and work. In so working, and eventually in dying, they
form waste-products — water and carbonic acid, ammonia
and nitrates, and so on — which may be again utilised by
plants.

How often is the inaccurate statement repeated “ that
animals take in oxygen and give out carbonic acid,
whereas plants take in carbonic acid and give out oxygen ” !
This is most misleading. It contrasts two entirely dis-
tinct processes — a breathing process in the animal with
a feeding process in the plant. The edge is at once
taken off the contrast when the student realises that plants
and animals being both (though not equally) alive, must
alike breathe. As they live the living matter of both is oxi-
dised, like the fat of a burning candle ; in plant, in animal,
in candle, oxygen passes in, as a condition of life or com-
bustion, and carbonic acid gas passes out as a waste-pro-
duct. Herein there is no difference except in degree between
plant and animal. Each lives, and must therefore breathe.
But the living of plants is less intense, therefore the breath-
ing process is less marked. Moreover, in sunlight the
respiration is disguised by an exactly reverse process —
peculiar to plants — the feeding already noticed, by which
carbonic acid gas is absorbed, its carbon retained, and part
of its oxygen liberated.

There is an old-fashioned experiment which illustrates
the “balance of nature.” In a glass globe, half-filled
with water, are placed some minute water-plants and water-
animals. The vessel is then sealed. As both the plants
and the animals are absorbing oxygen and liberating car-
bonic acid gas, it seems as if the little living world enclosed
in the globe would soon end in death. But, as we have seen,
the plants are able in sunlight to absorb carbonic acid and
liberate oxygen, and if present in sufficient numbers will

CHAP. II

21

The Web of Life

compensate both for their own breathing and for that of
animals. Thus the result within the globe need not be
suffocation, but harmonious prosperity. If the minute
animals .ate up all the plants, they would themselves die
for lack of oxygen before they had eaten up one another,
while if the plants smothered all the animals they would
also in turn die away. Some such contingency is apt to
spoil the experiment, the end of which may be a vessel of
putrid water tenanted for a long time by the very simple
colourless plants known as Bacteria, and at last not even
by them. Nevertheless the “vivarium” experiment is both
theoretically and practically possible. Now in nature there
is, indeed, no closed vivarium, for there is no isolation and
there is open air, and it is an exaggeration to talk as if our
life were dependent on there being a proportionate number
of plants and animals in the neighbourhood. Yet the
“ balance of nature ” is a general fact of much importance,
though the economical relations of part to part over a wide
area are neither rigid nor precise.

We have just mentioned the very simple plants called
Bacteria. Like moulds or fungi, they depend upon other
organisms for their food, being without the green colouring
stuff so important in the life of most plants. These very
minute Bacteria are almost omnipresent ; in weakly animals
— and sometimes in strong ones too — they thrive and
multiply and cause death. They are our deadliest foes, but
we should get rid of them more easily if we had greater love
of sunlight, for this is their most potent, as well as most
economical antagonist. But it is not to point out the
obvious fact that a Bacterium may kill a king that we have
here spoken of this class of plants ; it is to acknowledge
their beneficence. They are the great cleansers of the
world. Animals die, and Bacteria convert their corpses
into simple substances, restoring to the soil what the plants,
on which the animals fed, originally absorbed through
their roots. Bacteria thus complete a wide circle ; they
unite dead animal and living plant. For though many a
plant thrives quite independently of animals on the raw
materials of earth and air, others are demonstrably raising

22 The Study of Animal Life parti

the ashes of animals into a new life. A strange partner-
ship between Bacteria on the one hand and leguminous and
cereal plants on the other has recently been discovered.
There seems much likelihood that with some plants of
the orders just named Bacteria live in normal partner-
ship. The legumes and cereals in question do not thrive
well without their guests, nay more, it seems as if the
Bacteria are able to make the free nitrogen of the air
available -for their hosts.

3. Relation of Animals to the Earth. — Bacteria are
extremely minute organisms, however, and stories of
their industry are apt to sound unreal. But this cannot
be said of earthworms. For these can be readily seen
and watched, and their trails across the damp footpath,
or their castings on the grass of lawn and meadow, are
familiar to us all. They are distributed, in some form or
other, over most regions of the globe ; and an idea of their
abundance may be gained by making a nocturnal expedition
with a lantern to any convenient green plot, where they
may be seen in great numbers, some crawling about, others,
with their tails in their holes, making slow circuits in search
of leaves and vegetable debris. Darwin estimated that there
are on an average 53,000 earthworms in an acre of garden
ground, that 10 tons of soil per acre pass annually through
their bodies, and that they bring up mould to the surface at
the rate of 3 inches thickness in fifteen years. Hensen found
in his garden 64 large worm-holes in 14J square feet, and
estimated the weight of the daily castings at about 2
cwts. in two and a half acres. In the open fields, how-
ever, it seems to be only about half as much. But whether
we take Darwin’s estimate that the earthworms of England
pass annually through their bodies about 320,000,000 tons
of earth, or the more moderate calculations of Hensen, or
our own observations in the garden, we must allow that the
soil-making and soil -improving work of these animals is
momentous.

In Yorubaland, on the West African coast, earthworms
{Sip/ionogaster) somewhat different from the common Lum-
bricus are exceedingly numerous. From two separate square

CHAP. II

23

The Web of Life

feet of land chosen at random, Mr. Alvan Millson collected
the worm-casts of a season and found that they weighed
when dry iof lbs. At this rate about 62,233 tons of sub-
soil would be brought in a year to the surface of each
square mile, and it is also calculated that every particle of
earth to the depth of two feet is brought to the surface once
in 27 years. We do not wonder that the district is fertile
and healthy.

Devouring the earth as they make their holes, which are
often 4 or even 6 feet deep ; bruising the particles in their
gizzards, and thus liberating the minute elements of the soil ;
burying leaves and devouring them at leisure ; preparing the
way by their burrowing for plant roots and rain-drops, and
gradually covering the surface with their castings, worms have,
in the history of the habitable earth, been most important
factors in progress. Ploughers before the plough, they
have made fhe earth fruitful. It is fair, however, to
acknowledge that vegetable mould sometimes forms inde-
pendently of earthworms, that some other animals which
burrow or which devour dead plants must also help in the
process, and that the constant rain of atmospheric dust, as
Richthofen has especially noted, must not be overlooked.

In 1777, Gilbert White wrote thus of the earthworms —

“The most insignificant insects and reptiles are of much more
consequence and have much more influence in the economy of
nature than the incurious are aware of. . . . Earthworms, though in
appearance a small and despicable link in the chain of Nature, yet,
if lost, would make a lamentable chasm. . . . Worms seem to be
the great promoters of vegetation, which would proceed but lamely
without them, by boring, perforating, and loosening the soil, and
rendering it pervious to rains and the fibres of plants ; by drawing
straws and stalks of leaves and twigs into it ; and, most of all, by
throwing up such infinite numbers of lumps of earth called worm-
casts, which, being their excrement, is a fine manure for grain and
grass. Worms probably provide new soil for hills and slopes where
the rain washes the earth away ; and they affect slopes probably to
avoid being flooded. . . . The earth without worms would soon
become cold, hard-bound, and void of fermentation, and con-
sequently sterile. . . . These hints we think proper to throw out, in
order to set the inquisitive and discerning to work. A good mono-

24 The Study of Animal Life parti

graph of worms would afford much entertainment and information
at the same time, and would open a large and new field in natural
history.”

After a while the discerning did go to work, and Hensen
published an important memoir in 1877, while Darwin’s
“ good monograph ” on the formation of vegetable mould
appeared after about thirty years’ observation in 1881 ; and
now we all say with him, “ It may be doubted whether there
are many other animals which have played so important a
part in the history of the world as have these lowly-organised
creatures.”

Prof. Drummond, while admitting the supreme import-
ance of the work of earthworms, eloquently pleads the claims
of the Termite or White Ant as an agricultural agent. This
insect, which dwelt upon the earth long before the true ants,
is abundant in many countries, and notably in Tropical
Africa. It ravages dead wood with great rapidity. “If
a man lay down to sleep with a wooden leg, it would be a
heap of sawdust in the morning,” while houses and decaying
forest trees, furniture and fences, fall under the jaws of the
hungry Termites. These fell workers are blind and live
underground ; for fear of their enemies they dare not show
face, and yet without coming out of their ground they cannot
live.

“ How do they solve the difficulty? They take the ground out
along with them. I have seen white ants working on the top of a
high tree, and yet they were underground. They took up some of
the ground with them to the tree-top. They construct tunnels
which run from beneath the soil up the sides of trees and posts ;
grain after grain is carried from beneath and mortared with a sticky
secretion into a reddish sandpaper-like tube ; this is rapidly ex-
tended to a great height — even of 30 feet from the ground — till
some dead branch is reached. Now as many trees in a forest are
thus plastered with tunnels, and as there are besides elaborate
subterranean galleries and huge obelisk-like ant-hills, sometimes
10-15 feet high, it must be granted that the Termites, like the
earthworms, keep the soil circulating. The earth-tubes crumble
to dust, which is scattered by the wind ; the rains lash the forests
and soils with fury and wash off the loosened grains to swell the
alluvium of a distant valley.”

CHAP. II

The Web of Life

25

The influences of plants and animals on the earth are
manifold. The sea- weeds cling around the shores and
lessen the shock of the breakers. The lichens eat slowly
into the stones, sending their fine threads beneath the sur-
face as thickly sometimes “ as grass-roots in a meadow-land,”
so that the skin of the rock is gradually weathered away.
On the moor the mosses form huge sponges, which mitigate
floods and keep the streams flowing in days of drought.
Many little plants smooth away the wrinkles on the earth’s
face, and adorn her with jewels ; others have caught and
stored the sunshine, hidden its power in strange guise in
the earth, and our hearths with their smouldering peat or
glowing coal are warmed by the sunlight of ancient summers.
The grass which began to grow in comparatively modern
(i.e. Tertiary) times has made the earth a fit home for flocks
and herds, and protects it like a garment ; the forests affect
the rainfall and temper the climate, besides sheltering multi-
tudes of living things, to some of whom every blow of the
axe is a death-knell. Indeed, no plant from Bacterium to
oak tree either lives or dies to itself, or is without its
influence on earth and beast and man.

There are many animals besides worms which influence
the earth by no means slightly. Thus, to take the minus
side of the account first, we see the crayfish and their
enemies the water-voles burrowing by the river banks and
doing no little damage to the land, assisting in that process
by which the surface of continents tends gradually to
diminish. So along the shores in the harder substance
of the rocks there are numerous borers, like the Pholad
bivalves, whose work of disintegration is individually slight,
but in sum-total great. More conspicuous, however, is the
work of the beavers, who, by cutting down trees, building
dams, digging canals, have cleared away forests, flooded
low grounds, and changed the aspect of even large tracts
of country. Then, as every one knows, there are injuri-
ous insects innumerable, whose influence on vegetation, on
other animals, and on the prosperity of nations, is often
disastrously great.

But, on the other hand, animals cease not to pay their

26 The Study of Animal Life parti

filial debts to mother earth. We see life rising like a mist
in the sea, lowly creatures living in shells that are like
mosques of lime and flint, dying in due season, and sinking
gently to find a grave in the ooze. We see the submarine
volcano top, which did not reach the surface of the ocean,
slowly raised by the rainfall of countless small shells. Inch
by inch for myriads of years, the snow-drift of dead shells
fonns a patient preparation for the coral island. The
tiniest, hardly bigger than the wind-blown dust, form when
added together the strongest foundation in the world. • The
vast whale skeleton falls, but melts away till only the ear-
bones are left. Of the ruthless gristly shark nothing stays
but teeth. The sea-butterflies (Pteropods), with their frail
shells, are mightier than these, and perhaps the microscopic
atomies are strongest of all. The pile slowly rises, and the
exquisite fragments are cemented into a stable foundation
for the future city of corals.

At length, when the height at which they can live is
reached, coral germs moor themselves to the sides of the
raised mound, and begin a new life on the shoulders of death.
They spread in brightly coloured festoons, and have often
been likened to flowers. The waste salts of their living
perhaps unite with the gypsum of the sea-water, at any rate
in some way the originally soft young corals acquire strong
shells of carbonate of lime. Sluggish creatures they, living
in calcareous castles of indolence ! In silence they spread,
and crowd and smother one another in a struggle for stand-
ing-room. The dead forms, partly dissolved and cemented,
become a broad and solid base for higher and higher growth.
At a certain height the action of the breakers begins, great
severed masses are piled up or roll down the sloping sides.
Clear daylight at last is reached, the mound rises above the
water. The foundations are ever broadened, as vigorously
out-growing masses succumb to the brunt of the waves and
tumble downwards. Within the surface -circle weathering
makes a soil, and birds resting there with weary wings, or
perhaps dying, leave many seeds of plants — the begin-
nings of another life. The waves cast up forms of
dormant life which have floated from afar, and a ter-

CHAP. II

27

The Web of Life

restrial fauna and flora begin. It is a strange and beautiful
story, dead shells of the tenderest beauty on the rugged
shoulders of the volcano ; corals like meadow flowers
on the graveyard of the ooze ; at last plants and trees,
the hum of insects and the song of birds, over the coral
island.

4. Nutritive Relations. — What we may call “ nutritive
chains ” connect many forms of life — higher animals feed-
ing upon lower through long series, the records of which
sound like the stoiy of “The House that Jack built.” On
land and on the shore these series are usually short, for
plants are abundant, and the carnivores feed on the
vegetarians. In the open sea, where there is less vegeta-
tion, and in the great depths, where there is none, carni-
vore preys upon carnivore throughout long series — fish feeds
upon fish, fish upon crustacean, crustacean upon worm,
worm on debris. Disease or disaster in one link affects
the whole chain. A parasitic insect, we are told, has killed
off the wild horses and cattle in Paraguay, thereby influencing
the vegetation, thereby the insects, thereby the birds. Birds
of prey and small mammals — so-called “vermin” — are killed
off in order to preserve the grouse, yet this interference seems
in part to defeat itself by making the survival of weak and
diseased birds unnaturally easy, and epidemics of grouse-
disease on this account the more prevalent. A craze of vanity
or gluttony leads men to slaughter small insect-eating birds,
but the punishment falls — unluckily on the wrong shoulders
— when the insects which the birds would have kept down
increase in unchecked numbers, and destroy the crops of
grain and fruit. In a fuel -famine men have sometimes
been forced to cut down the woods which clothe the sides
of a valley, an action repented of when the rain-storms wash
the hills to skeletons, when the valley is flooded and the
local climate altered, and when the birds robbed of their
shelter leave the district to be ravaged by caterpillar and
fly. American entomologists have proved that the ravages
of destructive insects may be checked by importing and
fostering their natural enemies, and on the other hand, the
sparrows which have established themselves in the States

28

PART I

The Study of Animal Life

have in some districts driven away the titmice and thus
favoured the survival of injurious caterpillars.

5. More Complex Interactions. — The flowering plants
and the higher insects have grown up throughout long
ages together, in alternate influence and mutual per-
fecting. They now exhibit a notable degree of mutual
dependence ; the insects are adapted for sipping the
nectar from the blossoms ; the flowers are fitted for
giving or receiving the fertilising golden dust or pollen
which their visitors, often quite unconsciously, carry from
plant to plant. The mouth organs of the insects have
to be interpreted in relation to the flowers which they
visit ; while the latter show structures which may be
spoken of as the “ footprints ” of the insects. So exact is
the mutual adaptation that Darwin ventured to prophesy
from the existence of a Madagascar orchid with a nectar-
spur 1 1 inches long, that a butterfly would be found in the
same locality with a suctorial proboscis long enough to
drain the cup ; and Foi'bes confirmed the prediction by
discovering the insect.

As information on the relations of flowers and insects is
readily attainable, and as the subject will be discussed in
the volume on Botany, it is sufficient here to notice that, so
far as we can infer from the history half hidden in the
rocks, the floral world must have received a marked impulse
when bees and other flower-visiting insects appeared ; that
for the successful propagation of flowering plants it is
advantageous that pollen should be carried from one indi-
vidual to another, in other words, that cross -fertilisation
should be effected ; and that, for the great majority of
flowering plants, this is done through the agency of insects.
How plants became bright in colour, fragrant in scent, rich
in nectar, we cannot here discuss ; the fact that they are so
is evident, while it is also certain that insects are attracted
by the colour, the scent, and the sweets. Nor can there be
any hesitation in drawing the inference that the flowers
which attracted insects with most success, and insects which
got most out of the flowers, would, ipso facto , succeed better
in life.

CHAP. II

29

The Web of Life

No illustration of the web of life can be better than the
most familiar one, in which Darwin traced the links of
influence between cats and clover. If the possible seeds in
the flowers of the purple clover are to become real seeds,
they must be fertilised by the golden dust or pollen from
some adjacent clover plants. But as this pollen is uncon-
sciously carried from flower to flower by the humble-bees,
the proposition must be granted that the more humble-bees,
the better next year’s clover crop. The humble-bees, how-
ever, have their enemies in the field-mice, which lose no
opportunity of destroying the combs ; so that the fewer
field-mice, the more humble-bees, and the better next year’s
clover crop. In the neighbourhood of villages, however, it
is well known that the cats make as effective war on the
field-mice as the latter do on the bees. So that next year’s
crop of purple clover is influenced by the number of humble-
bees, which varies with the number of field-mice, that is to
say, with the abundance of cats ; or, to go a step farther,
with the number of lonely ladies in the village. It should
be noted, however, that according to Mr. James Sime there
were abundant fertile clover crops in New Zealand before there
were any humble-bees in that island. Indeed, many think
that the necessity of cross-fertilisation has been exaggerated.

Not all insects, however, are welcome visitors to plants ;
there are unbidden guests who do harm. To their visits,
however, there are often obstacles. Stiff hairs, impassably
slippery or viscid stems, moats in which the intruders
drown, and other structural peculiarities, whose origin may
have had no reference to insects, often justify themselves
by saving the plant. Even more interesting, however, is
the preservation of some acacias and other shrubs by a
bodyguard of ants, which, innocent themselves, ward off
the attacks of the deadly leaf-cutters. In some cases the
bodyguard has become almost hereditarily accustomed to
the plants, and the plants to them, for they are found in
constant companionship, and tlie plants exhibit structures
which look almost as if they had been made as shelters
for the ants. On some of our European trees similar
little homes or domatia constantly occur, and shelter small

3°

PART I

The Study of Animal Life

insects which do no harm to the trees, but cleanse them
from injurious fungi.

In many ways plants are saved from the appetite of

animals. The nettle
has poisonous hairs ;
thistles, furze, and holly
are covered with spines ;
the hawthorn has its
thorns and the rose
its prickles ; some have
repulsive odours ; others
contain oils, acids, fer-
ments, and poisons
which many animals
dislike ; the cuckoo-pint
(Arum) is full of little
crystals which make our
lips smart if we nibble
a leaf. In our studies
of plants we endeavour
to find out what these
qualities primarily mean
to their possessors ; here
we think rather of their
secondary significance
as protections against
animals. F or though

snails ravage all the
plants in a district ex-
cept those which are
repulsive, the snails are
at most only the second-
Fig. 4. — Acacia (A. sph cvroccph a la) , with hoi- ary factors in the evolu-
tion of the repulsive
qualities.

The strange inter-relations between plants and animals
are again illustrated by the carnivorous, generally insecti-
vorous, plants. It is not our business to discuss the
original or primary import of the pitchers of pitcher-plants

low thorns in which ants find shelter.
(After Schimper.)

CHAP. II

The Web of Life 31

or of the mobile and sensitive leaves of Venus’ Fly-Trap;
nowadays, at any rate, insects are attracted to them,
captured by them, and used. Let us take only one case,
that of the common Bladderwort ( Utricularia ). Many of
the leaflets of this plant, which floats in summer in the
marsh pond, are modified into little bladders, so fashioned
that minute “ water-fleas ” — which swarm in every corner of
the pool — can readily enter them, but can in no wise get out
again. The small entrance is guarded by a valve or door,
which opens inwards, but allows no egress. The little crusta-
ceans are attracted by some mucilage made by the leaves, or
sometimes perhaps by sheer curiosity ; they enter and cannot
return ; they die, and their ddbris is absorbed by the leaf.

Again, in regard to distribution, there are numerous
relations between organisms. Spiny fruits like those of
Jack-run-the-hedge adhere to animals, and are borne from
place to place ; and minute water-plants and animals are
carried from one watercourse to another on the muddy
feet of birds. Darwin removed a ball of mud from the
leg of a bird, and from it fourscore seeds germinated. N ot
a bird can fall to the ground and die without sending a
throb through a wide circle.

A conception of these chains or circles of influence
is important, not only for the sake of knowledge, but also as
a guide in action. Thus, to take only one instance among ,
a hundred, it may seem a far cry from a lady’s toilet-table
to the African slave-trade, but when we remember the ivory
backs of the brushes, and how the slaves are mainly used for
transporting the tusks of elephants — a doomed race — from
the interior to the coast, the riddle is read, and the respon-
sibility is obvious. Over a ploughed field in the summer
morning we see the spider-webs in thousands glistening
with mist-drops, and this is an emblem of the intricacy of
the threads in the web of life — to be seen more and more
as our eyes grow clear. Or, is not the face of nature like
the surface of a gentle stream, where hundreds of dimpling
circles touch and influence one another in an infinite com-
plexity of action and reaction beyond the ken of the wisest ?

CHAPTER III

THE STRUGGLE OF LIFE

i. Nature and Extent of the Struggle — 2. Armour and Weapons —
3. Different Forms of Struggle— 4. Cruelty of the Struggle

1. Nature and Extent of the Struggle.— If we realise
what is meant by the “ web of life,” the recognition of
the “ struggle for existence ” cannot be difficult. Animals
do not live in isolation, neither do they always pursue
paths of peace. Nature is not like a menagerie where
beast is separated from beast by iron bars, neither is it
- a melee such as would result if the bars of all the cages
were at once removed. It is not a continuous Waterloo,
nor yet an amiable compromise between weaklings. The
truth lies between these extremes. In most places where
animals abound there is struggle. This may be silent and
yet decisive, real without being very cruel, or it may be
full of both noise and bloodshed.

This struggle is very old ; it is older than the conflicts
of men, older than the ravin of tooth and claw, it is as old
as life. The struggle is often very keen — often for life or
death. But though few animals escape experience of the
battlefield— and for some there seems no discharge from
this war — we must not misinterpret nature as “a continual
free-fight.” One naturalist says that all nature breathes a
hymn of love, but he is an optimist under sunny southern
skies ; another compares nature to a huge gladiatorial
show with a plethora of fighters, but he speaks as a pes-

CHAT. Ill

33

The Struggle of Life

simist from amid the din of individualistic competition.
Nature is full of struggle and fear, but the struggle is
sometimes outdone by sacrifice, and the fear is sometimes
cast out by love. We must be careful to remember
Darwin’s proviso that he used the phrase “ struggle for
existence ” “ in a large and metaphorical sense, including the
dependence of one being on another, and including (which
is more important) not only the life of the individual, but
success in leaving progeny.” He also acknowledged the
importance of mutual aid, sociability, and sympathy among
animals, though he did not carefully estimate the relative
importance of competition on the one hand and sociability
on the other. Discussing sympathy, Darwin wrote, “ In
however complex a manner this feeling may have originated,
as it is one of high importance to all those animals which
aid and defend one another, it will have been increased
through natural selection ; for those communities which
included the greatest number of the most sympathetic
members would flourish best, and rear the greatest number
of offspring.” I should be sorry to misrepresent the
opinions of any man, but after considerable study of
modern Darwinian literature, I feel bound to join in the
protest which others have raised against a tendency to
narrow Darwin’s conception of “the struggle for existence,”
by exaggerating the occurrence of internecine competitive
struggle. Thus Huxley says, “ Life was a continuous free-
fight, and beyond the limited and temporary relations of
the family, the Hobbesian war of each against all was the
normal state of existence.” Against which Kropotkine
maintains that this “view of nature has as little claim to
be taken as a scientific deduction as the opposite view of
Rousseau, who saw in nature but love, peace, and harmony
destroyed by the accession of man.” . . . “ Rousseau has
committed the error of excluding the beak-and-claw fight
from his thoughts, and Huxley is committing the opposite
error; but neither Rousseau’s optimism nor Huxley’s pessi-
mism can be accepted as an impartial interpretation of
nature.”

2. Armour and Weapons. — If you doubt the reality

D

34

PART I

The Study of Animal Life

of the struggle, take a survey of the different classes ot
animals. Everywhere they brandish weapons or are forti-
fied with armour. “The world,” Diderot said, “is the
abode of the strong.” Even some of the simplest
animals have offensive threads, prophetic of the poison-
ous lassoes with which jellyfish and sea- anemones are
equipped. Many worms have horny jaws ; crustaceans
have strong pincers; many insects have stings, not to
speak of mouth organs like surgical instruments ; spiders
give poisonous bites ; snails have burglars’ files ; the cuttle-
fish have strangling suckers and parrots’ beaks. Among
backboned animals we recall the teeth of the shark and the
sword of the swordfish, the venomous fangs of serpents, the
jaws of crocodiles, the beaks and talons of birds, the horns
and hoofs and canines of mammals. Now we do not say
that these and a hundred other weapons were from their
first appearance weapons, indeed we know that most of
them were not. But they are weapons now, and just as we
would conclude that there was considerable struggle in a
community where every man bore a revolver, we must
draw a similar inference from the offensive equipment of
animals.

As to armoured beasts, we remember that shells of lime
or flint occur in many of the simplest animals, that most
sponges are so rich in spicules that they are too gritty to
be pleasant eating, that corals are polypes within shells
of lime, that many worms live in tubes, that the members
of the starfish class are in varying degrees lime-clad, that
crustaceans and insects are emphatically armoured animals,
and that the majority of molluscs live in shells. So among
backboned animals, how thoroughly bucklered were the
fishes of the old red sandstone against hardly less effect-
ive teeth, how the scales of modern fishes glitter, how
securely the sturgeon swims with its coat of bony mail 1
Amphibians are mostly weaponless and armourless, but
reptiles are scaly animals par excellence , and the tortoise,
for instance, lives in an almost impregnable citadel. Birds
soar above pursuit, and mammals are swift and strong,
but among the latter the armadillos have bony shields of

CHAP. Ill

35

The Struggle of Life

marvellous strength, and hedgehog and porcupine have
their hair hardened into spines and quills. Now we do not
say that all these structures were from the first of the
nature of armour, indeed they admit of other explanations,
but that they serve as armour now there can be no doubt.
And just as we conclude that a man would not wear
a chain shirt without due reason, so we argue from the
prevalence of animal armour to the reality of struggle.

For a moment let me delay to explain die two saving-
clauses which I have inserted. The pincers of a crab are
modified legs, the sting of a bee has probably the same
origin, and it is likely that most weapons originally served
some other than offensive purpose. We hear of spears
becoming pruning-hooks : the reverse has sometimes been
true alike of animals and of men. By sheer use a structure
not originally a weapon became strong to slay ; for there
is a profound biological truth in the French proverb : “A
force de forger on devient forgeron"

And again as to armour, it is, or was, well known that a
boy’s hand often smitten by the “tawse” became callous as
to its epidermis. Now that callousness was not a device-
providential or otherwise — to save the youth from the pains
of chastisement, and yet it had that effect. By bearing
blows one naturally and necessarily becomes thick-skinned.
Moreover, the epidermic callousness referred to might be
acquired by work or play altogether apart from school
discipline, though it might also be the effect of the blows.
In the same way many structures which are most useful as
armour may be the “mechanical” or natural results of
what they afterwards help to obviate, or they may arise
quite apart from their future significance.

3. Different Forms of Struggle. — If you ask why
animals do not live at peace, I answer, more Scottico,
Why do not we ? The desires of animals conflict with
those of their neighbours, .hence the struggle for bread
and the competition for mates. Hunger and love solve
the world’s problems. Mouths have to be filled, but
population tends locally and temporarily to outrun the
means of subsistence, and the question “which mouths”

Fig. s- — Bird-catching spider {My gale avicularui) attacking finches. (From Bates.)

CHAP. Ill

37

The Struggle of Life

has to be decided — sometimes by peaceful endeavour, as
in migration, sometimes with teeth clenched or ravenous.
Many animals are carnivorous, and must prey upon weaker
forms, which do their best to resist. Mates also have to
be won, and lover may fight with lover till death is stronger
than both. But these struggles for food and for mates are
often strivings rather than strife, nor is a recognition of the
frequent keenness and fierceness of the competition incon-
sistent with the recognition of mutual aid, sociability, and
love. There is a third form of the struggle, — that between
an animal and its changeful surroundings. This also is a
struggle without strife. Fellow competitors strive for their
share of the limited means of subsistence ; between foes
there is incessant thrust and parry ; in the courtship of
mates there are many disappointed and worsted suitors ;
over all are the shears of fate — a changeful physical
environment which has no mercy.

An analysis of the various forms of struggle may be
attempted as follows :

For

Food

For j
Love |

For )
F oot- v
hold j

(a) Between animals of the same kind which

compete for similar food and other
necessaries of life — Struggle between
fellows.

(b) Between animals of different kinds, the

one set striving to devour, the other set
endeavouring to escape their foes, e.g.
between carnivores and herbivores —
Struggle between foes.

(c) Between the rival suitors for desired

mates — Struggle between rivals in
love.

(d) Between animals and changeful surround-

ings— Struggle with fate.

In most cases, besides the egoism or individualism, one
must recognise the existence of altruism, parental love and
sacrifice, mutual aid, care for others, and sociality.

3 8 The Study of Animal Life part i

Before we consider these different forms of struggle, let
us notice the rapid multiplication of individuals which
furnishes the material for what in “ a wide and meta-
phorical sense ” may be called a “ battlefield.”

A single Infusorian may be the ancestor of millions by
the end of a week. A female aphis, often producing one
offspring per hour for days together, might in a season be
the ancestor of a progeny of atomies which would weigh
down five hundred millions of stout men. “ The roe of a
cod contains sometimes nearly ten million eggs, and sup-
posing each of these produced a young fish which arrived
at maturity, the whole sea would immediately become a
solid mass of closely packed codfish.” The unchecked
multiplication of a few mice or rabbits would soon leave no
standing-room on earth.

But fortunately, with the exception of the Infusorians, these
multiplications do not occur. We have to thank the
struggle in nature, and especially the physical environment,
that they do not. The fable of Mirza’s bridge is continually
true,— few get across.

(a) It is often said that the struggle between fellows of the
same kind and with the same needs is keenest of all, but
this is rather an assumption than an induction from facts.
The widespread opinion is partly due to an a priori con-
sideration of the problem, partly to that anthropomorphism
which so easily besets us. We transfer to the animal
world our own experience of keen competition with fellows
of the same caste, and in so doing are probably unjust.
Thus Mr. Grant Allen says —

“ The baker does not fear the competition of the butcher in the
struggle for life ; it is the competition of the other bakers that
sometimes inexorably crushes him out of existence. . . . In this
way the great enemies of the individual herbivores are not the
carnivores, but the other herbivores. ... It is not so much the
battle between the tiger and the antelope, between the wolf and
the bison, between the snake and the bird, that ultimately results
in natural selection or survival of the fittest, as the struggle between
tiger and tiger, between bison and bison, between snake and snake,
between antelope and antelope. . . . Homo homini lupus, says
the old proverb, and so, we may add, in a wider sense, lupus lupo

CHAP. Ill

39

The Struggle of Life

lupus, also. . . . The struggle is fierce between allied kinds, and
fiercest of all between individual members of the same species.”

I have quoted these sentences because they are clearly and
cleverly expressed, after the manner of Grant Allen, but I
do not believe that they are true statements of facts. The
evidence is very unsatisfactory. In his paragraph sum-
marised as “struggle for life most severe between indi-
viduals and varieties of the same species ; often severe
between species of the same genus,” Darwin gave five
illustrations : one species of swallow is said to have ousted
another in North America, the missel-thrush has increased
in Scotland at the expense of the song-thrush, the brown
rat displaces the black rat, the small Asiatic cockroach
drives its great congener before it, the hive-bee imported
to Australia is rapidly exterminating the small, stingless
native bee. But the cogency of these instances may be
disputed : thus what is said about the thrushes is denied by
Professor Newton. And on the other hand, we know that
reindeer, beavers, lemming, buffaloes and many other
animals migrate when the means of subsistence are unequal
to the demands of the population, and there are other
peaceful devices by which animals have discovered a way
out of a situation in which a life-and-death struggle might
seem inevitable. Very instructive is the fact that beavers,
when too numerous in one locality, divide into two parties
and migrate up and down stream. The old proverb which
Grant Allen quotes, Homo homini lupus , appears to me a
libellous inaccuracy ; the extension of the libel to the
animal world has certainly not been justified by careful
induction. For a discussion of the alleged competition
between fellows, I refgr, and that with pleasure and grati-
tude, to Kropotkine’s articles on “ Mutual Aid among
Animals,” Nineteenth Century , September and November
1890.

(/') Of the struggle between foes differing widely in kind
little need be said. It is very apparent, especially in wild
countries. Carnivores prey upon herbivores, which some-
times unite in successful resistance. Birds of prey devour

4° The Study of Animal Life part i

small mammals, and sometimes have to fight hard for their
booty. Reptiles also have their battles — witness the combats
between snake and mongoose. In many cases, however,
carnivorous animals depend upon small fry ; thus many
birds feed on fishes, insects, and worms, and many fishes
live on minute crustaceans. In such cases the tenn

Fig. 6. — Weasel attacking a grouse. (From St. John’s Wild Sports.)

#

struggle must again be used “ in a wide and metaphorical
sense.”

( c ) In a great number of cases there is between rival males
a contest for the possession of the females, — a competition
in which beauty and winsomeness are sometimes as im-
portant as strength. Contrast the musical competition
between rival songsters with the fierce combats of the stags.

CHAP. Ill The Struggle of Life 41

Many animals are not monogamous, and this causes strife ;
a male seal, for instance, guards his harem with ferocity.

(d) Finally, physical nature is quite careless of life. Changes
of medium, temperature, and moisture, continually occur,
and the animals flee for their lives, adapt themselves to
new conditions, or perish. Cataclysms are rare, but
changes are common, and especially in such schools of
experience as the sea-shore we may study how vicissitude
has its victims or its victors.

The struggle with Fate, that is to say, with changeful
surroundings, is more pleasant to contemplate than the
other kinds of struggle, for at the rigid mercilessness of
physical nature we shudder less than at the cruel competi-
tion between living things, and we are pleased with the
devices by which animals keep their foothold against wind
and weather, storm and tide, drought and cold. One illus-
tration must suffice : drought is common, pools are dried up,
the inhabitants are left to perish. But often the organism
draws itself together, sweats off a protective sheath, which
is not a shroud, and waits until the rain refreshes the pools.
Not the simplest animals only, but some of comparatively
high degree, are thus able to survive desiccation. The
simplest animals encyst, and may be blown about by the
wind, but they rest where moisture moors them, and are
soon as lively as ever. Leaping a long way upwards, we
find that the mud- fish {Protopterus) can be transported
from Africa to Northern Europe, dormant, yet alive,
within its ball of clay. We do not believe in toads appear-
ing out of marble mantelpieces, and a palaeontologist will
but smile if you tell him of a frog which emerged from an
intact piece of old red sandstone, but amphibians may
remain for a long time dormant either in the mud of their
native pools or in some out-of-the-way chink whither they
had wandered in their fearsome youth.

A shop which had once been used in the preparation
of bone-dust was after prolonged emptiness reinstated in a
new capacity. But it was soon fearfully infested with mites
( Glyciphagus ), which had been harboured in crevices in a
strange state of dry dormancy. Every mite had in a sense

42

PART 1

The Study of Animal Life

died, but remnant cells in the body of each had clubbed
together in a life-preserving union so effective that a return
of prosperity was followed by a reconstitution of mites and
by a plague of them. Of course great caution must be
exercised with regard to all such stories, as well as in
regard to the toads within stones. Of common little
animals known as Rotifers, it is often said, and sometimes
rightly, that they can survive prolonged desiccation. In a
small pool on the top of a granite block, there flourished a
family of these Rotifers. Now this little pool was period-
ically swept dry by the wind, and in the hollow there
remained only a scum of dust. But when the rain returned
and filled the pool, there were the Rotifers as lively as
ever. What inference was more natural than that the
Rotifers survived the desiccation, and lay dormant till
moisture returned ? But Professor Zacharias thought he
would like to observe the actual revivification, and taking
some of the dusty scum home, placed it under his micro-
scope on a moist slide, and waited results. There were the
corpses of the Rotifers plain enough, but they did not revive
even in abundant moisture. What was the explanation ?
The eggs of these Rotifers survived, they developed rapidly,
they reinstated the family. And of course it is much easier
to understand how single cells, as eggs are, could survive
being dried up, while their much more complex parents
perished. I do not suggest that no Rotifers can survive
desiccation, it is certain that some do ; but the story I
have told shows the need of caution. There is no doubt,
moreover, that certain simple “worms,” known as “paste-
eels,” “ vinegar-eels,” etc., from their frequent occurrence
in such substances, can survive desiccation for many years.
Repeated experiments have shown that they can lie dormant
for as long as, but not longer than, fourteen years ! and it
is interesting to notice that the more prolonged the period
of desiccation has been, the longer do these threadworms
take to revive after moisture has been supplied. It seems
as if the life retreated further and further, till at length it
may retreat beyond recall. In regard to plants there are
many similar facts, for though accounts of the germination

CHAP. Ill

43

The Struggle of Life

of seeds from 'the mummies of the pyramids, or from the
graves of the Incas, are far from satisfactory, there is no
doubt that seeds of cereals and leguminous plants may
retain their life in a dormant state for years, or even for
tens of years.

But desiccation is only one illustration out of a score
of the manner in which animals keep their foothold against
fate. I need hardly say that they are often unsuccessful ;
the individual has often fearful odds against it. How many
winged seeds out of a thousand reach a fit resting-place
where they may germinate ? Professor Mobius says that
out of a million oyster embryos only one individual grows
up, a mortality due to untoward currents and surroundings,
as well as to hungry mouths. Yet the average number of
thistles and oysters tends to continue, “ So careful of the
type she seems, so careless of the single life.” Yet though
the average usually remains constant, there is no use trying
to ignore, what Richard Jefferies sometimes exaggerated,
that the physical fates are cruel to life. But how much
wisdom have they drilled into us ?

“ For life is not as idle ore,

But iron dug from central gloom,

And heated hot with burning fears,

And dipt in baths of hissing tears,

And battered by the shocks of doom
To shape and use.”

4. Cruelty of the Struggle. — Opinions differ much as
to the cruelty of the “ struggle for existence,” and the
question is one of interest and importance. Alfred Russel
Wallace and others try to persuade us that our conception
of the “cruelty of nature” is an anthropomorphism; that,
like Balbus, animals do not fear death ; that the rabbit
rather enjoys a run before the fox ; that thrilling pain soon
brings its own anaesthetic ; that violent death has its
pleasures, and starvation its excitement. Mr. Wallace,
who speaks with the authority of long and wide ex-
perience, enters a vigorous protest against Professor
Huxley’s description of the myriads of generations of

44 The Study of Animal Life part i

herbivorous animals “ which have been tormented and
devoured by carnivores ” ; of both alike “ subject to all the
miseries incidental to old age, disease, and over-multiplica-
tion ” ; of the “ more or less enduring suffering ” which is
the meed of both vanquished and victor ; of the whole
creation groaning in pain. “ There is good reason to
believe,” says Mr. Wallace, “ that the supposed torments
and miseries of animals have little real existence, but are
the reflection of the imagined sensations of cultivated men
and women in similar circumstances ; and that the amount
of actual suffering caused by the struggle for existence
among animals is altogether insignificant.” “ Animals are
spared from the pain of anticipating death ; violent deaths,
if not too prolonged, are painless and easy ; neither do
those which die of cold or hunger suffer much ; the popular
idea of the struggle for existence entailing misery and pain
on the animal world is the very reverse of the truth.” He
concludes by quoting the conclusion of Darwin’s chapter on
the struggle for existence : “ When we reflect on this
struggle, we may console ourselves with the full belief that
the war of nature is not incessant, that no fear is felt, that
death is generally prompt, and that the vigorous, the
healthy, and the happy survive and multiply.” Yet it was
Darwin who confessed that he found in the world “too
much misery.”

We have so little security in appreciating the real life —
the mental and physical pain or happiness — of animals, that
there is apt to be exaggeration on both sides, according as
a pessimistic or an optimistic mood predominates. I there-
fore leave it to be settled by your own observation whether
hunted and captured, dying and starving, maimed and half-
frozen animals have to endure “ an altogether insignificant
amount of actual suffering in the struggle for existence.”

But I think we must admit that there is much truth in
what Mr. Wallace urges. Moreover, the term cruelty can
hardly be used with accuracy when the involved infliction
of pain is necessary. In many cases the carnivores are
less “ cruel ” to their victims than we are to our domesti-
cated animals. We must also remember that the “ struggle

chap, in The Struggle of Life 45

for existence ” is often applicable only in its “ wide and
metaphorical sense.” And it is fair to balance the happiness
and mutual helpfulness of animals against the pain and
deathful competition which undoubtedly exist.

What we must protest against is that one-sided inter-
pretation according to which individualistic competition is
nature’s sole method of progress. We are told that animals
have got on by their struggle for individual ends ; that they
have made progress on the corpses of their fellows, by a
“ blood and iron ” competition in which each looks out for
himself, and extinction besets the hindmost. To those who
accept this interpretation the means employed seem justified
by the results attained. But it is only in after-dinner talk
that we can slur over whatever there is of pain and cruelty,
overcrowding and starvation, hate and individualism, by
saying complacently that they are justified in us their
children; that we can rest satisfied that what has been
called “a scheme of salvation for the elect by the damnation
of the vast majority ” is a true statement of the facts ; that
we can seriously accept a one-sided account of nature’s
regime as a justification of our own ethical and economic
practice.

The conclusions, which I shall afterwards seek to
substantiate, are, that the struggle for existence, with its
associated natural selection, often involves cruelty, but
certainly does not always do so ; that joy and happiness,
helpfulness and co-operation, love and sacrifice, are also
facts of nature, that they also are justified by natural
selection ; that the precise nature of the means employed
and ends attained must be carefully considered when
we seek from the records of animal evolution support
or justification for human conduct ; and that the tragic
chapters in the history of animals (and of men) must be
philosophically considered in such light as we can gather
from what we know of the whole book.

CHAPTER IV

SHIFTS FOR A LIVING

I. Insulation — 2. Concealment — 3. Parasitism — 4. General Re-
semblance to Surroundings — 5. Variable Colouring — 6. Rapid
Change of Colour — 7. Special Protective Resemblance — S.
Warning Colours — 9. Mimicry — 10. Masking- — 11. Com-
bination of Advantageous Qualities — 12. Surrender of Parts

Granting the struggle with fellows, foes, and fate, we are
led by force of sympathy as well as of logic to think of the
shifts for a living which tend to be evolved in such con-
ditions, and also of some other ways by which animals
escape from the intensity of the struggle.

1. Insulation. — Some animals have got out of the
struggle through no merit of their own, but as the result
of geological changes which have insulated them from
their enemies. Thus, in Cretaceous times probably, the
marsupials which inhabited the Australasian region were
insulated. In that region they were then the only re-
presentatives of Mammalia, and so, excepting the “ native
dog,” some rodents and bats, and more modern imports,
they still continue to be. By their insulation they were
saved from that contest with stronger mammals in which
all the marsupials left on the other continents were
exterminated, with the exception of the opossums, which
hide in American forests. A similar geological insulation
accounts for the large number of lemurs in the island of
Madagascar.

CHAP. IV

Shifts for a Living

47

2. Concealment. — A change of habitat and mode of life
is often as significant for animals as it is for men. It is
easy to understand how mammals which passed from
terrestrial to more or less aquatic life, for instance beaver
and polar bear, seals, and perhaps whales, would enjoy
a period of relative immunity after the awkward time
of transition was over. So, too, many must have passed
from the battlefield of the sea- shore to relative peace
on land or in the deep-sea. In a change from open air
to underground life, illustrated for instance in the mole,
many animals have sought and found safety, and the
change seems even now in progress, as in the New
Zealand parrot Stringofis, which, having lost the power
of flight, has taken to burrowing. Similarly the power
of flight must have helped insects, some ancient saurians,
and birds out of many a scrape, though it cannot be
doubted that this transition, and also that from diurnal to
nocturnal habits, often brought only a temporary relief.

3. Parasitism. — From the simple Protozoa up to the
beginning of the backboned series, we find illustrations of
animals which have taken to a thievish existence as unbidden
guests in or on other organisms. Flukes, tapeworms, and
some other “ worms,” many crustaceans, insects, and mites,
are the most notable. Few animals are free from some kind
of parasite. There are various grades of parasitism ; there
are temporary and permanent, external and internal, very
degenerate, and very slightly affected parasites. Some-
times the adults are parasitic while the young are free -liv-
ing, sometimes the reverse is, true; sometimes the parasite
completes its life in one host, often it reaches maturity only
after the host in which its youth has been passed is de-
voured by another. In many cases the habit was probably
begun by the females, which seek shelter during the period
of egg-laying; in not a few crustaceans and insects the
females alone are parasitic. Most often, in all probability,
hunger and the search for shelter led to the establishment
of the thievish habit. Now, the advantages gained by a
thoroughgoing parasite are great — safety, warmth, abund-
ant food, in short, “ complete material well-being.” But

4S

PART I

The Study of Animal Life

there is another aspect of the case. Parasitism lends to be
followed by degeneration — of appendages, food -canal,
sense-organs, nervous system, and other structures, the
possession and use of which make life worth living. More-
over, though the reproductive system never degenerates,
the odds are often many against an embryo reaching a fit
host or attaining maturity. Thus Leuckart calculates that
a tapeworm embryo has only about X chance in 83,000,000
of becoming a tapeworm, and one cannot be sorry that
its chance is not greater. In illustration of the degenera-
tion which is often associated with parasitism, and varies
as the habit is more or less predominant, take the case of
Saccultna — a crustacean usually ranked along with bar-
nacles and acorn-shells. It begins its life as a minute free
“nauplius,” with three pairs of appendages, a short food-
canal, an eye, a small brain, and some other structures
characteristic of many young crustaceans. In spite of this
promiseful beginning, the young Sacculina becomes a para-
site, first within the body, and finally under the tail, of a
crab. Attached by absorptive suckers to its host, and
often doing - no slight damage, it degenerates into an oval
sac, almost without trace of its former structure, with
reproductive system alone well developed. Yet the
degeneration is seldom so great as this, and it is fair to
state that many parasites, especially those which remain as
external hangers-on, seem to be but slightly affected by their
lazy thievish habit ; nor can it be denied that most are well
adapted to the conditions of their life. But on the whole
the parasitic life tends to degeneration, and is unprogress-
ive. Meredith writes of Nature’s sifting —

“ Behold the life of ease, it drifts.

The sharpened life commands its course :

She winnows, winnows roughly, sifts,

To dip her chosen in her source.

Contention is the vital force

Whence pluck they brain, her prize of gifts.”

4. General Resemblance to Surroundings. — Many
transparent and translucent blue animals are hardly

CHAP. IV

49

Shifts for a Living

visible in the sea ; white animals, such as the polar bear,
the arctic fox, and the ptarmigan in its winter plumage,
are inconspicuous upon the snow ; green animals, such
as insects, tree-frogs, lizards, and snakes, hide among the
leaves and herbage ; tawny animals harmonise with sandy
soil ; and the hare escapes detection among the clods. So
do spotted animals such as snakes and leopards live unseen
in the interrupted light of the forest, and the striped tiger
is lost in the jungle. Even the eggs of birds are often well
suited to the surroundings in which they are laid. There
can be no doubt that this resemblance between the colour
of an animal and that of its surroundings is sometimes of
protective and also aggressive value in the struggle for
existence, and where this is the case, natural selection
would foster it, favouring with success those variations
which were best adapted, and eliminating those which were
conspicuous.

But there are many instances of resemblance to sur-
roundings which are hard to explain. Thus Dr. A. Seitz
describes a restricted area of woodland in South Brazil, where
the great majority of the insects were blue, although but
a few miles off a red colour was dominant. He maintains
that the facts cannot in this case be explained as due either
to general protective resemblance or to mimicry.

I have reduced what I had written in illustration of
advantageous colouring of various kinds, because this
exceedingly interesting subject has been treated in a readily
available volume by one who has devoted much time and
skill to its elucidation. Mr. E. B. Poulton’s Colours of
Animals (International Science Series, London, 1890) is a
fascinating volume, for which all interested in these aspects
of natural history must be grateful. With this a forth-
coming work {Animal Coloration , London, 1892) by Mr.
F. E. Beddard should be compared.

5. Variable Colouring. — Some animals, such as the
ptarmigan and the mountain-hare, become white in winter,
and are thereby safer and warmer. In some cases it
is certain that the pigmented feathers and hairs become
white, in other cases the old feathers and hairs drop

E

5° The Study of Animal Life part i

off and are replaced by white ones ; sometimes the
whiteness is the result of both these processes. It is
directly due to the formation of gas bubbles inside
the hairs or feathers in sufficient quantity to antagonise
the effect of any pigment that may be present, but in
the case of new growths it is not likely that any pig-
ment is formed. In some cases, e.g. Ross’s lemming and
the American hare (. Lepus americamis ), it has been clearly
shown that the change is due to the cold. It is likely that
this acts somewhat indirectly upon the skin through the
nervous system. We may therefore regard the change as
a variation due to the environment, and it is at least
possible that the permanent whiteness of some northern
animals, eg. the polar bear, is an acquired character of
similar origin. There are many objections to the theory
that the winter whiteness of arctic animals arose by the
accumulation of small variations in individuals which, being
slightly whiter than their neighbours, became dominant by
natural selection, though there can be no doubt that the
whiteness, however it arose, would be conserved like other
advantageous variations.

To several naturalists, but above all to Mr. Poulton, we
are indebted for much precise information in regard to the
variable colouring of many caterpillars and chrysalides.
These adjust their colours to those of the surroundings, and
even the cocoons are sometimes harmoniously coloured.
There is no doubt that the variable colouring often has
protective value. Mr. Poulton experimented with the

caterpillars of the peacock butterfly ( Vanessa io), small
tortoise-shell ( Vanessa urticce ), garden whites {Pier is
bras sic a and Pieris rapes), and many others. Caterpillars
of the small tortoise-shell in black surroundings tend to be-
come darker as pupae ; in a white environment the pupae
are lighter ; in gilded boxes they tend to become golden.
The surrounding colour seems to influence the caterpillar
“ during the twenty hours immediately preceding the last
twelve hours of the larval state,” “ and this is probably the
true meaning of the hours during which the caterpillar
rests motionless on the surface upon which it will pupate.”

chap. iv Shifts for a Living 51

“ It appears to be certain that it is the skin of the larva
which is influenced by surrounding colours during the
sensitive period, and it is probable that the effects are
wrought through the medium of the nervous system.”

Accepting the facts that caterpillars are subtly affected
by surrounding colours, so that the quiescent pupte har-
monise with their environment, and that the adjustment has
often protective value, we are led to inquire into the origin
of this sensitiveness. That the change of colour is
not a direct result of external influence is certain, but
of the physiological nature of the changes we know little
more than that it must be complex. It may be main-
tained, that “ the existing colours and markings are at any
rate in part due to the accumulation through heredity
of the indirect influence of the environment, working
by means of the nervous system ; ” “ to which it may
be replied,” Poulton continues, “ that the whole use and
meaning of the power of adjustment depends upon its
freedom during the life of the individual ; any hereditary
bias towards the colours of ancestors would at once destroy
the utility of the power, which is essentially an adaptation
to the fact that different individuals will probably meet with
different environments. As long ago as 1873 Professor
Meldola argued that this power of adjustment is adaptive,
and to be explained by the operation of natural selection.”
Poulton’s opinion seems to be, that the power of producing
variable colouring arose as a constitutional variation apart
from the influence of the environment, that the power was
fostered in the course of natural selection, and that its
limits were in the same way more or less defined in adapta-
tion to the most frequent habitat of the larvte before
and during pupation. The other theory is that the power
arose as the result of environmental influence, was accumu-
lated by inheritance throughout generations, and was fostered
like other profitable variations by natural selection. The
question is whether the power arose in direct relation
to environmental influence or not, whether external influence
was or was not a primary factor in evolving the power of
adapting colour, and in defining it within certain limits.

52

PART 1

The Study of Animal Life

6. Rapid Change of Colour. — For ages the chamaeleon
has been famous for its rapid and sometimes striking
changes of colour. The members of the Old World
genus Chamceleo quickly change from green to brown
or other tints, but rather in response to physical irrita-
tion and varying moods than in relation to change of
situation and surrounding colours. So the American
“ chameleons ” ( Anolis ) change, for instance, from emerald
to bronze under the influence of excitement and various
kinds of light. Their sensitiveness is exquisite ; “ a pass-
ing cloud may cause the bright emerald to fade.” Some-
times they may be thus protected, for “ when on the broad
green leaves of the palmetto, they are with difficulty per-
ceived, so exactly is the colour of the leaf counterfeited.
But their dark shadow is very distinct from beneath.” Most
of the lizards have more or less of this colour-changing
power, which depends on the contraction and expansion
of the pigmented living matter of cells which lie in layers
in the under-skin, and are controlled by nerves.

In a widely different set of animals — the cuttle-fishes —
the power of rapid colour-change is well illustrated. When
a cuttle-fish in a tank is provoked, or when one almost
stranded on the beach struggles to free itself, or, most
beautifully, when a number swim together in strange unison,
flushes of colour spread over the body. The sight suggests
the blushing of higher animals, in which nervous excitement
passing from the centre along the peripheral nerves influ-
ences the blood-supply in the skin ; but in colour-change the
nervous thrills affect the pigment-containing cells or chroma-
tophores, the living matter of which contracts or expands
in response to stimulus. It must be allowed that the colour-
change of cuttle-fish is oftenest an expression of nervous
excitement, but in some cases it helps to conceal the
animals.

More interesting to us at present are those cases of
colour- change in which animals respond to the hues of
their surroundings. This has been observed in some
Amphibians, such as tree-frogs ; in many fishes, such as
plaice, stickleback, minnow, trout, Gobius ruthmsparri ,

CUAl\ IV

53

Shifts for a Living

Serranus ; and in not a few crustaceans. The researches
of Briicke, Lister, and Pouchet have thrown much light on
the subject. Thus we know that the colour of surround-
ings affects the animals through the eyes, for blind plaice,
trout, and frogs do not change their tint. The nervous
thrill passes from eye to brain, and thence extends, not down
the main path of impulse — the spinal cord — but down the
sympathetic chain. If this be cut, the colour-change does
not take place. The sympathetic system is connected with
nerves passing from the spinal cord to the skin, and it is
along these that the impulse is further transmitted. The
result is the contraction or expansion of the pigment in the
skin-cells. Though the path by which the nervous influence
passes from the eye to the skin is somewhat circuitous, the
change is often very rapid. As the resulting resemblance
to surroundings is often precise, there can be no doubt that
the peculiarity sometimes profits its possessors.

7. Special Protective Kesemblance. — The likeness
between animals and their surroundings is often very precise,
and includes form as well as colour. Thus some bright butter-
flies, e.g. Kallima , are conspicuous in flight, but become
precisely like brown withered leaves when they settle upon
a branch and expose the under sides of their raised wings ;
the leaf-insects (Phy Ilium) have leaf-like wings and legs ;
the “ walking-sticks ” (. Phasmidce ), with legs thrown out at
all angles, resemble irregular twigs ; many caterpillars (of
Geometra moths especially) sit motionless on a branch,
supported in a strained attitude by a thin thread of silk, and
exactly resemble twigs ; others are like bark, moss, or
lichen. Among caterpillars protective resemblance is very
common, and Mr. Poulton associates its frequent occurrence
with the peculiarly defenceless condition of these young
animals. “ The body is a tube which contains fluid under
pressure ; a slight wound entails great loss of blood, while
a moderate injury must prove fatal.” “ Hence larvae are so
coloured as to avoid detection or to warn of some unplea-
sant attribute, the object in both cases being the same — to
leave the larva untouched, a touch being practically fatal.”
Among backboned animals we do not expect to find many

54

PART I

The Study of Animal Life

examples of precise resemblance to surrounding objects ;
but one of the sea-horses (Phyllopteryx eques) is said to be
exceedingly like the seaweed among which it lives. It is
very difficult at present to venture suggestions as to the
constitutional tendencies which may have resulted in
“ walking-leaves ” and “ walking-sticks,” but forms related
to these tend to resemble leaves. or sticks sufficiently to deter

Fig. 7. — Leaf-insect seated on a branch. (From Belt.)

one from postulating a mere sport as the origin of the
peculiarity which distinguishes Phyllium or Phasma. On
the other hand, some of the strangely precise minute
resemblances may be the fostered results of slight indefinite
sports. It is also possible that some of the cleverer
animals, such as spiders, learn to hide among the lichens
and on the bark which they most resemble. But in every
case, and especially where there are many risks, as among

chap. IV Shifts for a Living 55

caterpillars, the protective resemblance would be fostered
in the course of natural selection.

8. Warning Colours. — While many animals are con-
cealed by their colouring, others are made the more
conspicuous. But, as the latter are often unpalatable nr
dangerous, Wallace suggested that the colours were
warnings, which, as Poulton says, “ assist the education
of enemies, enabling them to easily learn and remember
the animals which are to be avoided.” Expressing
the same idea, Belt says, “ the skunk goes leisurely along,
holding up his white tail as a danger-flag for none to come
within range of his nauseous artillery.” So, the brightness
of the venomous coral-snake {Elaps) is a warning ; the
rattlesnake, excitedly shaking its rattle, “ warns an intruder
of its presence”; the cobra “ endeavours to terrify its enemy
by the startling appearance of its expanded hood and con-
spicuous eye-like marks.” The language in which conspicu-
ous colours are described by many naturalists tends to
exaggerate the subtlety of animals, for the intentional
warning of possible molesters involves rather complex ideas.
Belt’s description of the skunk, for instance, recalls a more
familiar sight — a cat showing fight to a dog — in regard to
which Mantegazza gravely tells us that the cat “ bristles up
her fur, and Inflates herself to appear larger, and to frighten
the dog who threatens her ” ! In our desire to be fair to the
subtlety of animals, it is indeed difficult to avoid being
credulous.

56

PART I

The Study of Animal Life

Perhaps the best illustration which Belt gives is that of
a certain gaily-coloured frog : —

“In the woods around Santo Domingo there are many frogs.
Some are green or brown, and imitate green or dead leaves, and
live amongst foliage. Others are dull earth-coloured, and hide in
holes and under logs. All these come out only at night to feed, and
they are all preyed upon by snakes and birds. In contrast to these
obscurely-coloured species, another little frog hops about in the
daytime dressed in a bright livery of red and blue. He cannot be
mistaken for any other, and his flaming vest and blue stockings
show that he does not court concealment. He is very abundant
in the damp wood, and I was convinced that he was uneatable
so soon as I had made his acquaintance, and saw the happy sense
of security with which he hopped about. I took a few specimens
home with me, and tried my fowls and ducks with them, but none
of them would touch them. At last, by throwing down pieces of
meat, for which there was a great competition amongst them, I
managed to entice a young duck into snatching up one of the
little frogs. Instead of swallowing it, however, it instantly threw
it out of its mouth, and went about jerking its head, as if trying to
throw off some unpleasant taste.”

Admirable, also, are the illustrations given by Mr. Poulton
in regard to many caterpillars, such as the larva of the
currant or magpie moth ( Abraxas grossulariata ), which is
conspicuous with orange and black markings on a cream
ground, and is refused altogether, or rejected with disgust,
by the hungry enemies of other caterpillars. Professor
Herdman and Mr. Garstang have also shown that the
Eolid Nudibranchs (naked sea-slugs), with brightly-coloured
and stinging dorsal papilla;, are rarely eaten by fishes ; and
the same is true of some other conspicuous and unpalat-
able marine animals.

The general conclusion seems fairly certain that the
conspicuousness of many unpalatable or noxious animals is
imprinted on the memory of their enemies, who, after pay-
ing some premiums to experience, learn to leave animals
with “warning colours” alone. It will be interesting
to discover how far the bright colour, the nauseous taste,
the poisonous properties, the distasteful odour, sometimes
found associated, are physiologically related to one another,
but to answer these questions we are still unprepared.

CHAP- IV

Shifts for a Living

57

9. Mimicry. — Mr. Poulton has carefully traced the transi-
tion from warning to mimetic appearance, and it is evident
that if hungry animals have been so much impressed with
the frequent association of unpalatableness and conspicuous
colours that they do not molest certain bright and nauseous
forms, then there is a chance that palatable forms may
also escape if they are sufficiently like those which are
passed by. The term mimicry is restricted to those cases

Fic. 9. — Hornet ( Priocnemis ) above, and mimetic bug (Sfiiniger) beneath.

(From Belt.)

“ in which a group of animals in the same habitat, character-
ised by a certain type of colour and pattern, are in part
specially protected to an eminent degree (the mimicked), and
in part entirely without special protection (the mimickers) ; so
that the latter live entirely upon the reputation of the former. V
The fact was “ discovered by Bates in Tropical America
(1862), then by Wallace in Tropical Asia and Malaya
( 1 866), and by Trimen in South Africa (1870)”; while Kirby,
in 1815, referred to the advantage of a certain fly being
like a bee, and of a certain spider resembling an ant.

5 & The Study of Animal Life part i

The constant conditions of mimicry are clearly and tersely
summed up by Wallace. They arc : —

1. That the imitative species occur in the same area,
and occupy the very same station, as the imitated.

2. That the imitators are always the more defenceless.

3- That the imitators are always less numerous in

individuals.

4. That the imitators differ from the bulk of their
allies.

Fig. 10. — Humming-bird moth ( Macrogiossa titan), and humming-bird
( Lophornis Gouldii). (From Eates.)

5. That the imitation, however minute, is external and
visible only, never extending to internal characters or to
such as do not affect the external appearance.

Many inedible butterflies are mimicked by others quite
different. Many longicorn beetles exactly mimic wasps,
bees, or ants. The tiger-beetles are mimicked by more
harmless insects ; the common drone-fly ( Erislalis ) is like
a bee ; spiders are sometimes ant -like. Mr. Bates relates
that he repeatedly shot humming-bird moths in mistake for
humming-birds. Among Vertebrates genuine mimicry is
rare, but it is well known that some harmless snakes mimic

CHAP. IV Shifts for a Living 59

poisonous species. Thus, the very poisonous coral-snakes
(Flaps), which have very characteristic markings, are
mimicked in different localities by several harmless forms.
Similarly in regard to birds, Mr. Wallace notices that the
powerful “friar-birds” (Tropidorhynchtis) of Malaya are
mimicked by the weak and timid orioles. “In each of the
great islands of the Austro-Malayan region there is a dis-
tinct species of Tropidorhynchus , and there is always along
with it an oriole that exactly mimics it.”

That there may be mimetic resemblance between distinct
forms there can be no doubt, and the value of the resem-
blance has been verified ; but there is sometimes a tendency
to weaken the case by citing instances or using terms which
have been insufficiently criticised. Thus the facts hardly
justify us in saying that the larvae of the Elephant Hawk
Moth (ChcErocampa) “ terrify their enemies by the sugges-
tion of a cobra-like serpent ; ” or that the cobra, which “ in-
spires alarm by the large eye-like ‘ spectacles ’ upon the
dilated hood, offers an appropriate model for the swollen
anterior end of the caterpillar, with its terrifying markings.”

There is only one theory of mimicry, namely, that among
the mimicking animals varieties occurred which prospered
by being somewhat like the mimicked, and that in the
course of natural selection this resemblance was gradually
increased until it became dominant and, in many cases,
remarkably exact.

As to the primary factors giving rise to the variation, we
can only speculate. To begin with, indeed, there must
have been a general resemblance between the ancestors of
the mimicking animal and those of the mimicked, for cases
like the Humming-Bird and its Doppel-Ganger moth are very
rare. But this does not take us very far. The beginning
of the mimetic change is usually referred to one of those
“ indefinite,” “ fortuitous,” “ spontaneous ” variations which
are believed to be common among animals. It is logically
possible that this may have been the case, and that there
was at the very beginning no relation between the variation
of the mimicker and the existence of the mimicked. But
as illustrations of mimicry accumulate — and they are already

mmntfnimrvMi

60

The Study of Animal Life

I'Ali'i' I

Illustrations of Masking. A hermit crab with sea-anemones (after Andres), a crab covered by a sponge (Sufi,-.
another crab with seaweed and zoophyte growing on it. (In part after Cams Sterne.)

CHAP. IV

S /lifts for a IJving 61

very numerous — one is tempted to ask whether there may
not be in many cases some explanation apart from the action
of natural selection upon casual changes. May not the
similar surroundings and habits of mimickers and mimicked
have sometimes something to do with their resemblance ;
may it not be that the presence of the mimicked has had a
direct, but of course very subtle, influence on the mimickers ;
is it altogether absurd to suppose that there may be an
element of consciousness in the resemblance between oriole
and friar-bird ?

io. “Masking” is one of the most interesting ways
in which animals strengthen their hold on life. It is best
illustrated on the sea-shore, where there is no little struggle
for existence and much opportunity for device. There many
animals, such as crabs, are covered by adventitious dis-
guises, so that their real nature is masked. Elsewhere,
however, the same may be seen ; the cases of the cacklis-
worms — made of sand particles, small stones, minute shells,
or pieces of bark — serve at once for protection and conceal-
ment ; the cocoons of various caterpillars are often masked
by extrinsic fragments. The nests of birds are often well
disguised with moss and lichen.

But among marine animals masking is more frequent.
“Certain sea-urchins,” Mr Poulton says, “ cover themselves
so completely with pebbles, bits of rock and shell, that one
can see nothing but a little heap of stones ; and many marine
molluscs have the same habits, accumulating sand upon the
surface of the shell, or allowing a dense growth of Algae to
cover them.”

This masking is in many cases quite involuntary. Thus
the freshwater snails ( Lymnaus ) may be so thickly covered
with Algae that they can hardly move, and some marine
forms are unable to favour or prevent the growth of other
organisms upon their shells. But how far this is from be-
ing the whole story is well known to all who are acquainted
with our shore crabs. For though they also may be invol-
untarily masked, there is ample evidence that they some-
times disguise themselves.

The hermit-crabs are to some extent masked within

62

I’ART I

The Study of Animal Life

then- stolen shells, especially if these be covered by the
Hydroid Hydractinia or other organisms. Various other
crabs ( Stenorhynchus , Inachus , Mata, Dromia, Pisa ) are
masked by the seaweeds, sponges, and zoophytes which
cover their carapace. Moreover, the interest of this mask-
ing is increased by the fact observed by Mr. Bateson at
Plymouth that the crabs sometimes fix the seaweeds for

Fig. 12. — Sack-bearing caterpillar ( Saccopiora ). (From Bates.)

themselves. Mr. Bateson describes how the crab seizes a
piece of weed, tears off a piece, chews the end in his mouth,
and then rubs it firmly on his head and legs until it is
caught by the curved hairs and fixed. “ The whole pro-
ceeding is most human and purposeful. Many substances,
as hydroids, sponges, Polyzoa, and weeds of many kinds
and colours, are thus used ; but these various substances
are nearly always symmetrically placed on corresponding

CHAP. IV

63

Shifts for a Living

parts of the body, and particularly long plume-like pieces
are fixed on the head.” Thus, as Carus Sterne says, is the
story of “ Bimam’s walking wood ” re-enacted on the sea-
shore. Furthermore, a Stenorhynchus which has been
cleaned will immediately begin to clothe itself again, with
the same care and precision as before. Mr. Robertson of
Millport often saw Stenorhynchus longirostris — a common
crab — picking about its limbs and conveying the produce
to its mouth. “ If other observations confirm the view that
this animal is a true vegetarian, we shall have one example
at least of an independent agriculturist, who is not only
superior of his lands, but carries them with him when
he removes.” I also have seen the crab doing what “ the
naturalist of Cumbrae ” observed. In further illustration
of masking we may cite Dromia vulgaris , often covered
with sponge ; Dromia excavata , with compound ascidians ;
the Amphipod Atylus , with seaweed ; while a species of
Dorippe is said to bear a bivalve shell, or even a leaf, as a
shield, and another crab cuts off the tunic of a sea-squirt
and hitches it on his own shoulders.

Sometimes this masking serves as a warning or deterrent ;
witness that hermit-crab ( Pagurus cuanejisis') whose stolen
shell is surrounded by a bright orange sponge ( Suberites
domuncula). As this sponge is full of flinty needles, has a
strong odour and a disagreeable taste, we do not wonder
that Mr. Garstang finds that fish dislike it intensely, nor
can we doubt that the hermit-crab trades on the reputation of
its associate. In other cases the masking will aid in con-
cealment and favour attack. To the associations of crabs
and sea-anemones we shall afterwards refer.

11. Combination of Advantageous Qualities. — Mr.
Poulton describes, in illustration of the combination of
many methods of defence, the case of the larva of the
puss moth ( Centra vinula). It resembles the leaves of the
poplar and willow on which it lives. When disturbed it
assumes a terrifying attitude, mimetic of a Vertebrate
appearance ! The effect is heightened by the protrusion of
two pink whips from the terminal prongs of the body, and
finally the creature defends itself by squirting formic acid.

64

PART I

The Study of Animal Life

Yet in spite of all this power of defence, the larva often falls
a victim to ichneumon-flies. These manage to lay their eggs

within the caterpillar, which
by and by succumbs to the
voracity of the hatched
ichneumon maggots. Mr.
Poulton believes that the
puss moth larva “ has been
saved from extermination
by the repeated acquisition
of new defensive measures.
But any improvement in

Fig. 13. — “Terrifying attitude” of the the means of defence has
caterpillar of Centra vinula. (From i-.ppn n,pf 1, tvp ,rrpntp

Chambers’s Encyclop. ; after Poulton.) mCC Dy tne greater

ingenuity or boldness of
foes ; and so it has come about that many of the best-
protected larvae are often those which die in the largest
numbers from the attacks of enemies. The exceptional
standard of defence has been only reached through the
pressure of an exceptional need.”

1 2. Surrender of Parts. — Among the strange life - pre-
serving powers which animals exhibit, we must also
include that of surrendering parts of the body in the
panic of capture or in the struggle to escape. A rat

will gnaw off a leg to free itself from a trap, and I have

heard of a stoat which did not refrain from amputating
more than one limb. But the cases to which we now refer
are not deliberate amputations, but reflex and unconscious
surrenders. Many lizards (such as our British “ slowworm ”)
will readily leave their tails in their captor’s grasp ; crus-
taceans, insects, and spiders part with their limbs and
scramble off maimed but safe ; starfishes, brittle-stars, and
feather-stars resign their arms, and the sea-cucumbers their
viscera. A large number of cases have been studied by
Fredericq and Giard.

Among Crustacea the habit is most perfectly developed
in the crabs, e.g. the common shore-crab (Carcinus mamas'),
and in the spiny lobster ( Palinurus ), but it is also exhibited
by the crayfish ( Astacus ), the common lobster (Homan/s),

CHAP. IV

65

Shifts for a Living '

the shrimp ( Crangon ), and the prawn ( Palcemon ). In crabs
and in the spiny lobster the surrender of a limb is effected
by the forcible contraction of the basal muscles, and the
line of rupture is through the second-lowest joint. Frede-
ricq’s researches seem to prove conclusively that the sur-
render is a reflex and unconscious act, but its protective
value is not less great. The chances are in favour of the
crab escaping, the residue of muscle prevents haemorrhage
from the stump, and in the course of time the lost limb is
replaced by a new growth. The crab does not know what
it is doing, but it unconsciously illustrates that it is better
that one member should perish than that the whole life
should be lost.

Not a few insects readily surrender their legs, but these
are not replaced. Spiders are captured if the legs are fixed
without irritating the nerves, for that is an essential con-
dition of the reflex amputation. In regard to lizards, also,
it has been shown that a reflex nervous excitement, and not
mere brittleness, is the condition of surrender. Here, how-
ever, the lost tail may be replaced. Among Mollusca a
surrender of parts has been recorded of Ilarpa ventricosa,
Doris cruenta , S left opus, some species of Helix , the razor-
shell Solen ; while it is well known that male cuttle-fishes
sometimes part with one of their arms for special sexual
purposes. A great many “ worms ” break very easily, and
the severed parts are sometimes able to regrow the whole
organism.

Among the Echinoderms the tendency to disrupt is exhi-
bited to an extraordinary degree. Thus Professor Preyer has
shown that the seven-rayed starfish ( Asterias tenuispina)
surrenders its arms with great readiness, often giving off
three or four at a time. But each ray may reproduce an
entire starfish. Professor Edward Forbes tells how a speci-
men of Ltiidia , which he had dredged, was disappearing
over the side of the boat when he caught it by one of its
arms; it surrendered the ann and escaped, giving “a wink
of derision ” with one of its eyes. Brittlfe-stars (Ophiuroids)
of many kinds are true to their popular name, and the
Crinoids are not less disruptive. Not only are the arms

F

66

PART I

The Study of Animal Life

readily given off, but these break into many fragments.
There can be no doubt that this habit, combined with the
marvellous power of regrowth which these animals possess,
is of great protective value, while it is also probable in regard
to both Echinoderms and some worms, that the disruption
of parts may really increase the number of individuals.

There is no need to enumerate all the protective habits
and devices which animals exhibit. Some “ feign ” death,
by falling in panic into a state allied to hypnotic trance,
perhaps in some of the higher animals by conscious decep-
tion ; others roll themselves up into balls, as in forms so
different as myriapods and armadillos ; but, finally, I shall
cite from Dr. Hickson’s Naturalist in North Celebes one
other device. “ I often saw advancing slowly over the
sea-gardens, in parties of from four to six, a group of
cuttle-fish, swimming with an even backward movement,
the fringes of their mantles and their arms trembling,
and their colour gradually changing to what seemed to
me an almost infinite variety of hues as they passed-
over the various beds of the sea -bottom. Then suddenly
there would be a commotion in what was previously a
calm and placid scene, the striped and speckled reef fishes
would be seen darting away in all directions, and of the
cuttle-fishes all that remained were four or five clouds of ink
in the clear water. They had thrown dust in the eyes of
some small shark or voracious fish.”

But I should not like to suggest the idea that animals
are always careful and anxious, or forced to continual
struggle and shift.

“ They do not sweat and whine about their condition,

They do not lie awake in the dark and weep for their sins,
They do not make me sick discussing their duty to God,

Not one is dissatisfied, not one is demented
With the mania of owning things;

Not one kneels to another, nor to his kind that lived thousands
of years ago ;

Not one is respectable or unhappy over the w'hole earth.”

Walt Whitman.

CHAPTER V

SOCIAL LIFE OF ANIMALS

i . Partnerships — 2. Co-operation and Division of Labour — 3. Gre-
garious Life and Combined Action — 4. Beavers — 5- Bees — 6.
Ants — 7. Termites — 8. Evolution of Social Life — 9. Advantages
of Social Life — 10. A Note on the Social Organism — 11.
Conclusions

The over- fed plant, bears many leaves but its flowers
are few ; the animal which eats too much becomes fat ;
and we know that within the living body one part may
grow out of proportion to the others. It seems as if
organ competed with organ within the living engine, as
if one tissue outgrew its neighbours in the living web, as
if there were some struggle for existence between the
individual units which form the city of cells in any of the
higher animals. This idea of internal competition has
been elaborated by a German biologist, Roux, in a work
entitled The Struggle of Parts within the Organism , and
it is full of suggestiveness. It can be verified from our
own experience ; but yet it seems strange. F or we rightly
think of an organism as a unity in which the parts are
bound together in mutual helpfulness, being members one
of another.

Now, just as a biologist would exaggerate greatly if he
maintained that the struggle of parts was the most im-
portant fact about an organism, so would a naturalist if he
maintained that there was in nature struggle only and no
helpfulness.

68

PART I

The Study of Animal Life

Coherence and harmony and mutual helpfulness of
parts — whether these be organs, tissues, or cells — are
certainly facts in the life of individuals ; we have now
to see how far the same is true of the larger life in
which the many are considered as one.

i. Partnerships. — Animals often live together in strange
partnerships. The “beef-eater” birds ( Buphagus ) perch
on cattle and extract grubs from the skin ; a kind of plover
( Pluvianus agyptius) removes leeches and other parasites
from the back of the crocodile, and perhaps “picks his teeth,”
as Herodotus alleged ; the shark is attended by the pilot-fish
'(. Naucrates ductor ), who is shielded by the shark’s reputa-
tion, and seems to remove parasites from his skin.

Especially among marine animals, we find many almost
constant associations, the meaning of which is often obscure.
Two gasteropods Rhizochilus and Magilus grow along
with certain corals, some barnacles are common on whales,
some sponges and polypes are always found together, with-
out there being in any of these cases either parasitism or
partnership. But when we find a little fish living con-
tentedly inside a large sea-anemone, or the little pea-crab
(. Pinnotheres ) within the horse-mussel, the probable explana-
tion is that the fish and the crab are sheltered by their
hosts and share their food. They are not known to do
harm, while they derive much benefit. They illustrate one
kind of “ commensalism,” or of eating at the same table.

But the association between crabs and sea- anemones
affords a better illustration. One of the hermit-crabs of
our coast ( Pagurus prideauxii ) has its borrowed shell
always enveloped by a sea-anemone ( Adamsia palliata),
and Pagurus bernhardus may be similarly ensheathed by
Adamsia rotideletii. Mobius describes two crabs from
Mauritius which bear a sea-anemone on each claw, and in
some other crabs a similar association occurs. It seems
that in some cases the crab deliberately chooses its ally and
plants it on its shell, and that it does not leave it behind at
the period of shell- changing. Deprived of its polype com-
panion, one was seen to be restlessly ill at ease until
it obtained another of the same kind. The use of the sea-

CHAP. V

69

Social Life of A nimals

anemone as a mask to the crab — and also perhaps as
aid in attack or defence — is obvious ; on the other hand,
the sea-anemone is carried about by the crab and may
derive food from the crumbs of its bearer’s repast.

Commensalism must be distinguished from parasitism,
in which the one organism feeds upon its host, though it is
quite possible that a commensal might degenerate into a
parasite. Quite distinct also is that intimate partnership
known as symbiosis, illustrated by the union of algoid and
fungoid elements to form a lichen, or by the occurrence of
minute Algae as constant internal associates and helpful
partners of Radiolarians and some Ccelenterates.

2. Co-operation and Division of Labour. — The idea
of division of labour has been for a long time familiar to
men, but its biological importance was first satisfactorily
recognised by Milne-Edwards in 1827.

Among the Stinging -animals there are many animal
colonies, aggregates of individuals, with a common life.
These begin from a single individual and are formed by
prolific budding, as a hive is formed by the prolific egg-
laying of a queen-bee. The mode of reproduction is
asexual in the one case, sexual in the other ; the resulting
individuals are physically united in the one case, psychically
united in the other ; but these differences are not so great
as they may at first sight appear. Many masses of coral
are animal colonies, but among the members or “ persons,”
as they are technically called, division of labour is very rare ;
moreover, in the growth of coral the younger individuals
often smother the older. In colonial zoophytes the
arborescent mode of growth usually obviates crushing ; and
there is sometimes very marked division of labour. Thus
in the colony of Hy dr actinia polypes, which is often found
growing on the shells tenanted by hermit-crabs, there may
be a hundred or more individuals all in organic connection.
The polypes are minute tubular animals, connected at
their bases, and stretching out from the surface of the shell
into the still water of the pool in which the hermit-crab is
resting. But among the hundred individuals there are
three or four castes, the differences between which probably

7o

PART 1

The Study of Animal Life

result from the fact that in such a large colony perfect
uniformity of nutritive and other conditions is impossible.
Individuals which are fundamentally and originally like one
another grow to be different, and perform different func-
tions according to the caste to which they belong.

Many are nutritive in form like the little freshwater
Hydra — tubular animals with an extensile body and with a
terminal mouth wreathed round by mobile tentacles. On

Fig. 14. — Colony of Hydractinia
echinata. a, nutritive individuals ;
b, reproductive individuals ; c,
abortive spines ; and there are
also long mouthless individuals
specialised in sensitiveness. (From
Chambers’s Encyclop. ; after All-
man).

their life as individuals is p
trate the dark side of divisioi

these the whole nutrition of the
colony depends. Beside these
there are reproductive “ per-
sons,” which cannot feed,
being mouthless, but secure
the continuance of the species
and give rise to embryos which
start new colonies. Then there
are long, lank, sensitive mem-
bers, also mouthless, which
serve as the sense-organs of the
colony, and are of use in de-
tecting food or danger. When
danger threatens, the polypes
cower down, and there are left
projecting small hard spines,
which some regard as a fourth
class of individuals — starved,
abortive members like the
thorns on the hawthorn hedge.
In recognising their utility to
the colony as a whole we can
hardly overlook the fact that
radically nil. They well illus-
l of labour.

Herbert Spencer and Ernst Haeckel have explained very clearly
one law of progress among those animals which form colonies.
The crude form of a colony is an aggregate of similar individuals,
the perfected colony is an integrate in which by division of labour
greater harmony of life has resulted, and in which the whole colony
is more thoroughly compacted into a unity. Among the Stinging-

chap, v Social Life of Animals 71

animals, we find some precise illustrations of such integrated colonies,
especially in the Siphonophora of which the Portuguese Man-of-War
( Physalia ) is a good example. There is no doubt that these
beautiful organisms are colonies of individuals, which in structure
are all referable to a “ medusoid ” or jellyfish-like type. But the
division of labour is so harmonious, and the compacting or ^
organisation of the colony is so thorough, that the whole moves and
lives as a single organism.

E. Perrier in his work entitled Les Colonies Animates (Paris,
1882), shows how organic association may lead from one grade of
organisation and individuality to another, and explains very clearly
how sedentary and passive life tends to develop mere aggregates,
while free and active life tends to integrate the colony. With this
may be compared A. Lang’s interesting study on the influence of
sedentary life and its connection with asexual reproduction — Das
Einfluss des Festsilzen (Jena, 1889). Haeckel, in his Generelle
Morpkologie (2 vols., Berlin, 1866), was one of the first to shed a
strong clear light on the difficult subject of organic individuality,
its grades and its progressive complexity. To Spencer, Principles
of Biology (2 vols., London, 1863-67), we owe in this connection
the elucidation of the transition from aggregates to integrates, and
of the lines of differentiation, i.e. the progressive complication of
structure which is associated with division of labour.

3. Gregarious Life and Combined Action. — Most
mammals are in some degree gregarious. The solitary
kinds are in a distinct minority. The isolated are ex-
posed to attack, the associated are saved by the wisdom
of their wisest members and by that strength which union
gives. Many hoofed animals, such as deer, antelopes,
goats, and elephants, live in herds, which are not mere
crowds, but organised bands, with definite conventions and
with a power of combined resistance which often enables
them to withstand the attacks of carnivores. Marmots and
prairie-dogs, whose “ cities ” may cover vast areas, live peace-
ful and prosperous lives. Monkeys furnish many illustra-
tions of successful gregarious life. As individuals most of
them are comparatively defenceless, and usually avoid com-
ing to close quarters with their adversaries ; yet in a body
they are formidable, and often help one another out of
scrapes. Brehm tells how he encountered a troop of baboons
which defied his dogs and retreated in good order up the

72

FART I

The Study of Animal Life

heights. A young' one about six months old being left
behind called loudly for aid. “ One of the largest males,
a true hero, came down again from the mountain, slowly
went to the young one, coaxed him, and triumphantly led
him away — the dogs being too much astonished to make an
attack.”

Fig. is.— Chimpanzee ( Anthropopithecus or Troglodytes calvus).
(From Du Chaillu.)

Many birds, such as rooks and swallows, nest together,
and the sociality is often advantageous. Kropotkine cites
from Dr. Coues an observation in regard to some little cliff-
swallows which nested in a colony cjuite neai the home of a
prairie-falcon. “ The little peaceful birds had no fear of
their rapacious neighbour ; they did not let it even approach
to their colony. They immediately surrounded it and

CHAr. V

73

Social Life of Animals

chased it, so that it had to make off at once.” Of the
cranes, Kropotkine notes that they are extremely “ sociable
and live in friendly relations, not only with their congeners,
but also with most aquatic birds.” They post sentries, send
scouts, have many friends and few enemies, and are very
intelligent. So is it also with parrots. “ The members of
each band remain faithfully attached to each other, and they
share in common good or bad luck.” They feed together,
fly together, rest together ; they send scouts and post sen-
tinels ; they find protection and pleasure in combination.
Like the cranes, they are very intelligent, and safe from
most enemies except man.

On the other hand, some of the most successful carni-
vores, e.g. wolves, hunt in packs, and not a few birds of
prey (some eagles, kites, vultures) unite to destroy their
quarry. Combination for defence has its counterpart in
combination for attack. In both cases the collective action
is often associated with the custom of posting sentinels, who
warn the rest, or of sending scouts to reconnoitre. Pecu-
liarly interesting are those cases in which the relatively
weak unite to attack the strong ; thus a few kites will rob an
eagle, and wagtails will persecute a sparrow-hawk. Kropot-
kine has noticed how the aquatic birds which crowd on the
shores of lakes and seas often combine to drive off intrud-
ing birds of prey. “In the face of an exuberant life, the
ideally armed robber has to be satisfied with the off-fall of
that life.”

Among many animals there is co-operation in labour, as
well as combination for attack or defence. Brehm relates that
baboons and other monkeys act in thorough concert in
plundering expeditions, sending scouts, posting sentinels, and
even forming a long chain for the transport of the spoil. It
is said that several Hamadryad baboons will unite to turn
over a large stone, sharing the booty found underneath.
When the Brazilian kite has seized a prey too large for it
to carry, it summons its friends; and Kropotkine cites a re-
markable case in which an eagle called others to the car-
case. Pelicans fish together in great companies, forming a
wide half-circle facing the shore and catching the fish thus

74

PART I

The Study of Animal Life

enclosed. Burial beetles unite to bury the dead mouse or
bird in which the eggs are laid, and the dung-beetles help
one another in rolling balls of food. But of all cases of
combined activity the migration of birds is at once the most
familiar and the most beautiful— the gathering together, the
excitement before starting, the trial flights, the reliance
placed in the leaders. Migration is usually social, and
is sustained by tradition.

4. Beavers. — That the highly -socialised beavers have
been' e'xterminated in many countries where they once
abounded is no argument against their sociality, for man
has ingenuity enough to baffle any organisation. A family
of about six members inhabits one house, and in suitable
localities — secluded and rich in trees — many families con-
gregate in a village community. The young leave the par-
ental roof in the summer of their third year, find mates for
themselves, and establish new homesteads. The community
becomes overcrowded, however, and migrations take place
up and down stream, the old lodges being sometimes left to
the young couples. It is said, moreover, that lazy or other-
wise objectionable members may be expelled from the society,
and condemned to live alone. Under constraint of fear or
human interference, and away from social impulse, beavers
may relapse into lazy and careless habits, and in many
cases each family lives its life apart ; but in propitious
conditions their achievements are marvellous. The burrow
may rise into a constructed home, and the members of
many families may combine in wood-cutting and log-rolling,
and yet more markedly in constructing dams and digging
canals. Make allowances for the exaggeration of enthusiastic
observers, but read Mr. Lewis Morgan’s stories of the evolu-
tion of a broken burrow into a comfortable lodge, varying
according to the local conditions ; of the adaptation of the
dams against the rush of floods ; of canals hundreds of feet
in length — labours without reward until they are finished ;
of the short-cut waterways across loops of the river ; and of
“ locks ” where continuous canals are, from the nature of the
ground, impossible. The Indians have invested beavers
with immortality, but it is enough for us to recognise that

chap, v Social Life of Animals 75

they exhibit more sagacity than can be explained by heredi-
tary habit, for they often adapt their actions to novel condi-
tions in a manner which must be described as intelligent.
Especially when we remember that the beaver belongs to a
somewhat stupid rodent race, are we inclined to believe that
it is the cleverest of its kind because the most socialised.

5. Bees.' — Many centuries have passed since men first
listened to the humming of the honey-bees, and found in the
hive a symbol of the strength of unity. From Aristotle’s
time till now naturalists have
been studying the life of bees,
without exhausting either its
facts or its suggestions. The
society is very large and
complex, yet very stable and
successful. Its customs seem
now like those of children at
play, and now like the real-
ised dreams of social refor-
mers. The whole life gives
one the impression of an old-
established business in which
all contingencies have been
so often experienced that
they have ceased to cause
hesitation or friction. There
is indeed much mortality, g. 16. — Honey-bee (A pis mellifica).
some apparent cruelty, and
the constantly recurring ad-
venture of migration ; but though hive may war against
hive, inter-civic competition has virtually ceased, and the
life proceeds smoothly with the harmony and effectiveness
of a perfected organisation.

The mother-bee, whom we call a “ queen ” — though she
is without the wits and energy of a ruler — is to this extent
head of the community, that, by her prolific egg-laying, she
increases or restores the population. Very sluggish in
their ordinary life are the numerous males or “ drones,”
one of whom, fleet and vigorous beyond his fellows, will pair

76 The Study of Animal Life part i

with a queen in her nuptial flight, himself to die soon after,
saved at least from the expulsion and massacre which await
all the sex when the supplies of honey run short in autumn.
The queen and drones are important only so far as multiplica-
tion is concerned. The sustained life of the hive is wholly in
the hands of the workers, who in brains, in activity, and
general equipment are greatly superior to their “ queen.”
“ The queen has lost her domestic arts, which the worker pos-
sesses in a perfection never attained by the ancestral types ;
while the worker has lost her maternal functions, although
she still possesses the needed organs in a rudimentary state.”
What a busy life is theirs, gathering nectar and pollen
unwearyingly, while the sunshine lasts, neatly slipping into
the secrets of the flowers or stealing their treasures by
force, carrying their booty home in swift sweeping flight,
often over long distances unerringly, unloading the pollen
from their hind-legs and packing it into some cells of the
comb, emptying out the nectar from their crop or honey-
sac into store-cells, and then off again for more — such is
their socialised mania for getting. But, besides these
“foragers” — for the most part seniors — there are younger
stay-at-home “ nurses,” whose labours, if less energetic, are
not less essential. For it is their part to look after the
grubs in their cradles, to feed them at first with a “ pap ” of
digested nectar, and then to wean them to a diet of honey,
pollen, and water ; to attend the queen, guiding her move-
ments and feeding her while she lays many eggs, sometimes
2000 to 3000 eggs in a day. Mr. Cheshire, in his incom-
parably careful book on Bees and Beekeeping , laughs at the
“many writers who have given the echo to a mediaeval
fancy by stating that the queen is ever surrounded by a
circle of dutiful subjects, reverently watching her move-
ments, and liable to instant banishment upon any neglect
of duty. These it was once the fashion to compare to the
twelve Apostles, and, to make the ridiculous suggestion
complete, their number was said to be invariably twelve ! "
But Mr. Cheshire’s own account of the nurses’ work, and of
the whole life of the hive, is more marvellous than any
mediaeval fancy.

CHAP. V

77

Social Life of Animals

We have not outlined nearly all the labours of the
workers. There is the exhausting though passive labour of
forming the wax which oozes out on the under-surface of the
body, and then there is the marvellous comb-building, at
which the bees are very neat and clever workers, though they
do not deserve the reputation for mathematical insight once
granted them. “Their combs,” Mr. Cheshire says, “are
rows of rooms unsurpassably suitable for feeding and nurtur-
ing the larvae, for giving safety and seclusion during the
mystic sleep of pupa-hood, for ensconcing the weaiy worker
seeking rest, and for safely warehousing the provisions ever
needed by the numerous family and by all during the
winter’s siege. Corridors run between, giving sufficient
space for the more extensive quarters of the prospective
mother, and affording every facility to the busy throng
walking on the ladders the edges of their apartments supply ;
while the exactions of modern hygiene are fully met by air,
in its native purity, sweeping past the doorway of every
inhabitant of the insect city.”

We shall not seek to penetrate into the more hidden
mysteries of the life of bees ; for instance, “ how the drones
have a mother but no father,” or how high feeding makes
the difference between a queen and a worker. An outline
of the yearly life is more appropriate. From the winter’s
rest the surviving bees reawaken when the early-flowering
trees begin to blossom ; the workers engage in a “ spring
cleaning,” and the queen restores the reduced population
by egg-laying. New supplies of food are brought in, new
bees are born, and in early summer we see the busy life in
all its energy. The pressure of increased population makes
itself felt, and migration or “ swarming ” becomes impera-
tive. In due time and in fair weather “ the old mother
departs with the superabundance of the population.”
Meanwhile in the parent-hive drones have been born, ttnd
several possible queens await liberation. The first to be
set free has to hold her own against newcomers, or it may be
to die before one of them. The successful new queen soon
becomes restless, issues forth in swift nuptial flight, is
fertilised by a drone, and returns to her home to begin

78 The Study of Animal Life part i

prolific egg-laying, and perhaps after a time to lead off
another swarm. During the busy summer, when food is
abundant, the lazy males are tolerated ; but when their
function is fulfilled, and when the supplies become scarce,
they are ruthlessly put to death. “No sooner does income
fall below expenditure, than their nursing sisters turn
their executioners, usually by dragging them from the hive,
biting at the insertion of the wing. The drones, strong for
their especial work, are, after all, as tender as they are
defenceless, and but little exposure and abstinence is
required to terminate their being. So thorough is the war
of extermination, that no age is spared ; even drone eggs
are devoured, the larvae have their 'juices sucked and their
‘remains’ carried out — a fate in which the chrysalids are
made to take part, the maxim for the moment being, He
that will not work, neither shall he eat.” This Lycurgan
tragedy over, the equilibrium of the hive is more secure,
and the winter comes.

The social life of hive -bees is of peculiar interest,
because it represents the climax of a series of stages.
Hermann Muller has traced the plausible history of the
honey-bee from an insect like the sand-wasp, and has
shown in other kinds of bees the various steps by which
the pollen-gathering and nectar-collecting organs have been
developed. The habits of life gradually lead up to the
consummately social life of the hive. Thus Prosopis , which
lays its eggs in the pith of bramble-stems ; the wood-boring
Xylophaga ; and the leaf-cutting Megachilc , which lines its
burrows with circles cut from rose leaves, are solitary bees.
The various species of humble- or bumble-bee ( Bombus ), so
familiarly industrious from the spring, when the willows
bear their catkins, till the autumn chill benumbs, are half-
way to the hive-bees ; for they live in societies of mother,
drones, and workers during summer, while the ^ole surviv-
ing queens hibernate in solitude. From the humble-bee,
moreover, we gain this hint, that the home is centred in
the cradle, for it is in a nest with honey and pollen stored
around the eggs that the hive seems to have begun.

6. Ants. — Even more suggestive of our own social organ-

CHAP. V

79

Social Life of Animals

isation is the Liliputian world of the ants, who, like micro-
scopic men, build bams and lay up stores, divide their labour
and indulge in play, wage wars and make slaves. Like the
bee-hive, the ant-nest includes three kinds of individuals —
a queen mother or more than one, a number of short-lived
males, and a crowd of workers. The queen is again pre-
eminently maternal, and, if we can trust the enthusiastic
observers, she is attended with loyal devotion, not without
some judicious control. Farren White describes how the
workers attend the queen in her perambulations : “ They
formed round her when she rested ; some showed their regard
for her by gently walking over her, others by patiently watch-
ing by her and cherishing her with their antennas, and
in every way endeavouring to testify to their affectionate
attachment and generous submission.” Gould ventures
further, alleging that “ in whatever apartment a queen
condescends to be present, she commands obedience and
respect, and a universal gladness spreads itself through the
whole cell, which is expressed by particular acts of joy and
exultation. They have a peculiar way of skipping, leaping,
and standing up on their hind legs, and prancing with the
others. These frolics they make use of both to congratu-
late each other when they meet, and to show their regard
for the queen.” These are wonderful lists of assumed
emotions ! Should an indispensable queen be desirous to
quit the nest, the workers do not hesitate, it is said, to
keep her by force, and to tear off her wings to secure her
stay. It is certain at least that as the queens settle down
to the labour of maternity, their wings are lost — perhaps in
obedience to some physiological necessity. From the much
greater number of the wingless workers, we are apt to forget
that the males and mothers of the social ants are winged
insects ; but this fact becomes impressive if in fine summer
weather we are fortunate enough to see the males and
young queens leaving the nest in the nuptial flight, during
which fertilisation takes place. Rising in the air they
glitter like sparks, pale into curling smoke, and vanish.
“ Sometimes the swarms of a whole district have been
noticed to unite their countless myriads, and, seen at a dis-

8o

PART I

The Study of Animal Life

tance, produce an effect resembling the flashing of the
Aurora Borealis ; sometimes the effect is that of rainbow
hues in the spray of laughing waterfalls ; sometimes that of
fij-e ; sometimes that of a smoke- wreath.” “ Each column
looks like a kind of slender network, and has a tremulous
undulating motion. The noise emitted by myriads and
myriads of these creatures does not exceed the hum of
a single wasp. The slightest zephyr disperses them.”
After this midsummer day’s delight of love, death awaits
many, and sometimes most. The males are at best short-
lived, but the surviving queens, settling down, may begin

Fig. 17. — Saiiba ants at work ; to the left below, an ordinary worker ; to the
right a large-headed worker ; above, a subterranean worker. (From Bates.)

to form nests, gathering a troop of workers, or sometimes
proceeding alone to found a colony.

A caste of workers (i.e. normally non -reproductive
females) distinct from the males and queens, involves, of
course, some division of labour; but there is more than
this. Workers of different ages perform different tasks —
fox-aging or housekeeping, fighting or nursing, as the case
may be ; and just as the various human occupations leave
marks both for good and ill in those who follow them, so
the division of labour among ants is associated with differ-
ences of structure. Thus, in the Saiiba or Umbrella Ant of
Brazil (CEcodoma cephalotcs ), so well described by Bates in

CIIAP. V

8 I

Social Life of Animals

his Naturalist on the Amazons , there are three classes of
workers. All the destructive labour of cutting sixpence-like
disks from the leaves of trees is done by individuals with
small heads, while others with enormously large heads
simply walk about looking on. These “worker-majors”
are not soldiers, nor is there any need for supervising
officers. “ I think,” Bates says, “ they serve, in some
sort, as passive instruments of protection to the real
workers. Their enormously large, hard, and indestructible
heads may be of use in protecting them against the
attacks of insectivorous animals. They would be, on this
view, a kind of pieces de resistance , serving as a foil against
onslaughts made on the main body of workers.” The
third order of workers includes very strange fellows, with
the same kind of head as the worker-majors have, but “ the
front is clothed with hairs instead of being polished, and
they have in the middle of the forehead a twin simple
eye,” which none of the others possess. Among the
honey ants ( Myrmecocystus mexicanus ) described by Dr.
M‘Cook from the “ Garden of the Gods ” in Colorado, the
division of labour is almost like a joke. The workers
gather “honey” from certain galls, and discharge their
spoils into the mouths of some of their stay-at-home fellows.
These passive “ honey-pots ” store it up, till the abdomen
becomes tense and round like a grape, but eventually they
have even more tantalisingly to disgorge it for other mem-
bers of the community. But this habit of feeding others is
exhibited, as Forel has shown, by many species of ants.
The hungry apply to the full for food, and get it. A
refusal is said to be sometimes punished by death !

Marvellous in peace, the ants may also practise the
anti-social “art of war,” sometimes against other com-
munities of the same species, sometimes with other kinds.
“ Their battles,” Kirby says, “ have long been celebrated ;
and the date of them, as if it were an event of the first
importance, has been formally recorded.” ./Eneas Sylvius,
after giving a very circumstantial account of one contested
with great obstinacy between a great and small species on
the trunk of a pear tree, gravely states, “ This action was

G

82

I' ART I

The Study of Animal Life

fought in the pontificate of Eugenius IV., in the presence of
Nicholas Pistoriensis, an eminent lawyer, who related the
whole history of the battle with the greatest fidelity.” In
the fray the combatants are thoroughly absorbed, yet at a
little distance other workers are uninterruptedly treading
their daily paths ; the melee is intense, yet every ant seems
to know those of its own party ; the result of it all is often
nothing. We laugh at the ants — the laugh comes back on
ourselves.

In some cases an expedition has the definite end of slave-
making, as is known to be true of Formica sangninea — a
British species, and of Polyergus rufescens , found on the Con-
tinent. The former captures the larvae of Formica fusca,
carries them home, and owns them henceforth as well-
treated slaves ; while the Amazon Ant ( Polyergus ) draws
its supply from both F. fusca and F. cunicularia, and
seems to have become almost dependent on its captives.
Indeed, Huber says that he never knew the Amazons take
nourishment but from the mouth of the negro captives ;
while Lubbock notes that every transition exists between
bold and active baron-like marauders and enervated masters,
who are virtually helpless parasites upon their slaves — a
suggestive illustration of laziness outwitting itself.

Slaves somewhat painfully suggest domesticated animals,
and these are also to be found among ants. For what
Linnaeus said long ago, that the ants went up trees to “ milk
their cows, the Aphides,” is true. The ants tickle these little
plant-lice with their antennae, and lick the juice which oozes
from them ; nay more, according to some, they inclose and
tend these milch kine, and even breed them at home.
Seed-harvesting and the like may be fairly called agricul-
tural, and do not the leaf-cutters grow mushrooms, or at
least feed on the fungi which grow on the leaves, stored
some say with that end in view ? The driver ants,
“whose dread is upon every living thing,” when they
are on the stampede, remind us of the ancient troops
of nomad hunters, though some of them are blind. Thus
there are hunting, agricultural, and pastoral ants — three
types, as Lubbock remarks, offering a strange analogy

chap, v Social Life of Animals 83

to the three great phases in the history of human develop-
ment.

Very quaint is another habit of this “little people, so
exceeding wise,” — that of keeping or tolerating guests in the
home ! These are mostly little beetles, and have been
carefully studied by Dr. Weismann, who distinguishes true
guests (. Atemeles , Lomechusa , Claviger) which are cared for
and fed by the ants, from others ( Dinarda , Hester ins,
Formicoxenus) which are tolerated, though not treated with
special friendliness, and which feed on dead ants or vege-
table debris ; while a third set are tolerated — like mice in
our houses — only because they cannot be readily turned out.
Of the genuine guests, the best known is Atemeles , a lively
animal, constantly moving its feelers, and experimenting
with everything. If one be attacked by a hostile ant, it
first seeks to pacify its antagonist by antennary caresses,
but if this is hopeless it emits a strong odour, which seems
to narcotise the ant. These little familiars are really
dependent upon their hosts, who feed them and get
caresses in return. It is easy to understand the presence
of pests in the ants’ home, but Atemeles and Lomechusa
are pets, taken away by the owners when there is a flitting,
and exhibiting, as Lubbock also observes, “international
relations,” since they can be shifted from one nest to
another, or even from species to species. It seems likely
enough, as Emery suggests, that these semi-domesticated
pets are moralised intruders, and, like our cats, they seem
to retain some of their original traits.

I cannot linger longer over the interesting character-
istics of ants, though I should like to speak of their archi-
tecture, of their roads, tunnels, bridges, and covered
ways ; of their care for the young, and sometimes even for
the disabled ; of their proverbial industry, and yet of their
indulgence in “ sportive exercise.” It would be profitable
to think about the contrast between solitary ants (Mutilidce)
who have no “ workers,” and the complex life of a com-
munity in which there are half a million residents ; or about
their aesthetic sensitiveness, for they see light and hear
sound for which our eyes and ears are not adapted ; or

8 4 The Study of Animal Life i>akt i

about their power of recognising their fellow-citizens (even
when intoxicated), and of communicating definite impres-
sions to one another by a subtle language of touch and
gesture ; or about their instincts and intelligence, and the
limitations of these. But it will be better to read some of
the detailed observations, endeavouring, though necessarily
with slight success, to think into the nature of ants, — their
pertinacity, their indomitable “pluck,” their tireless in-
dustry, their organic sociality. Surely all will agree with
Sir John Lubbock, to whose patient observations we owe
so much, that, “ when we see an ant-hill, tenanted by
thousands of industrious inhabitants, excavating chambers,
forming tunnels, making roads, guarding their home,
gathering food, feeding the young, tending their domestic
animals, each one fulfilling its duties industriously and
without confusion, it is difficult altogether to deny them the
gift of reason,” or, perhaps more accurately, intelligence,
for we cannot escape the conviction “ that their mental
powers differ from those of men not so much in kind as
in degree.”

Kropotkine says that the work of ants is performed
“ according to the principles of voluntary mutual aid.”
“ Mutual aid within the community, self-devotion grown into
a habit, and very often self-sacrifice for the common wel-
fare, are the rule.” The marvels of their history are “ the
natural outcome of the mutual aid which they practise at
every stage of their busy and laborious lives.” To this
mode of life is also due “ the immense development of indi-
vidual initiative.” Ants are not well protected, but “ their
force is in mutual support and mutual confidence.” “ And
if the ant stands at the very top of the whole class of In-
sects for its intellectual capacities ; if its courage is only
equalled by the most courageous Vertebrates, and if its
brain — to use Darwin’s words — ‘ is one of the most mar-
vellous atoms of matter in the world, perhaps more so than
the brain of man,’ is it not due to the fact that mutual aid
has entirely taken the place of mutual struggle in the com-
munities of ants ? ”

7. Termites. — The true ants are so supremely interest-

CHAr. V

85

Sorin' Life of Animals

ing, that the Termites or “ white ants ” (which are not ants at
all) are apt to receive scant justice. Perhaps inferior in intel-
ligence, they have the precedence of greater antiquity and
all the interest which attaches to an old-established society.
Nor is their importance less either to practical men or to
speculative biologists. In 1781 Smeathman gave some
account of their economy, noting that there were in every
species three castes, “ first, the working insects, which, for
brevity, I shall generally call labourers ; next, the fighting
ones or soldiers , which do no kind of labour ; and, last of
all, the winged ones, or perfect insects , which are male and
female, and capable of propagation.”

The “ workers,” blind and wingless, and smallest in the
ant-hill, do all the work of foraging and mining, attending
the royal pair and nursing the young. The soldiers, also
blind and wingless, are much larger than the workers, but
there are relatively only a few in each hill. “ They stand,”
Prof. Drummond says, “ or promenade about as sentries, at
the mouths of the tunnels. When danger threatens, in the
shape of true ants, the soldier termite advances to the fight.”
“With a few sweeps of its scythe-like jaws it clears the
ground, and while the attacking party is carrying off its
dead, the builders, unconscious of the fray, quietly continue
their work.” At home, in the ant-hill, shut up in a chamber
whose door admits workers but is much too small for the
tenants to pass out if they would, a fortunate investigator
sometimes finds the royal pair. The. male is sometimes
even larger than the soldier, and is in many ways different,
though by no means extraordinary. The queen -mother,
however, is a very strange organism. She measures two
to six inches, while the worker is only about a fifth of an
inch in length. Like her mate, she sees, and she once had
wings like his, but they have dropped off. The hind
part of the body is enormously distended with eggs, and
“ the head bears about the same proportion to the rest of
the body as does the tuft on his Glengarry bonnet to a six-
foot Highlander.” In her passivity and “ phenomenal cor-
pulence,” she is a sort of reductio ad absurdum of femaleness
— “a large, cylindrical package, in shape like a sausage,

86 The Study of Animal Life part i

and as white as a bolster.” But have some admiration for
her : she sometimes lays 60 eggs per minute, or 80,000
in a day, and continues reproducing for months. As she
lays, she is assiduously fed by the nursing-workers, while the
eggs are carried off to be hatched in the nurseries. At the
breeding season, numerous winged males and females leave

Fig. 18. — Diagrammatic section of a termite's nest (after Houssay). In the walls
there are winding passages (f) ; uppermost is a well-aired empty attic (D)
the next story (C) is a nursery where the young termites are hatched on
shelves (a) and (h) ; the next is a hall (B) supported by pillars ; beneath this
is a royal chamber (?') in which the king and queen are imprisoned ; around
this the chambers of worker-termites (s) and some store-chambers (/«) ;
excavated in the ground are holes (c) out of which the material used in
making the termitary was dug. The whole structure is sometimes 10-15
feet in height.

the hill and its workers in swarms, most of them simply to
die, others to mate with individuals from another hill and
to begin to form new colonies.

The plot of the story becomes more intricate, however,
when we notice Fritz Muller’s observations, that “ besides

chap, v Social Life of Animals 87

the winged males and females which are produced in vast
numbers, and which, leaving the termitary in large swarms,
may intercross with those produced in other communities,
there are (in some if not all of the species) wingless
males and females which never leave the termitary where
they are born, and which replace the winged males or
females whenever a community does not find, in due time, a
true king or queen.” There is no doubt as to the existence
of both winged and wingless royal pairs. According to
Grassi, the former fly away in spring, the others ascend the
throne in summer. The complementary kings or viceroys
die before winter ; their mates live on, widowed but still
maternal, till at least the next summer.

This replacement of royalty reminds us that hive-bees,
bereft of their queen, will rear one from the indifferent grub,
but the termites with which we are best acquainted seem
almost always to have a reserve of reproductive members.
This other difference between termites and ants or bees
should be noticed, that in the latter the “workers” are
highly-developed, though sterile females, while in the former
the workers seem to be arrested forms of both sexes. They
are children which do not grow up.

8. Evolution of Social Life. — To Professor Alfred
Espinas both naturalists and sociologists are greatly in
debted for his careful discussion of the social life of animals.
It may be useful, therefore, to give an outline of the mode
of treatment followed in his work — Des SociitSs Animales :
Etude de Psychologie Comparee (Paris, 1877) : —

Co-operation, which is an essential characteristic of all society,
implies some degree of organic affinity. There are, indeed,
occasional associations between unrelated forms — “ mutualism,” in
which both associates are benefited; “ commensalism,” in which
the benefit is mainly one-sided ; parasitism, which is distinctly
anti-social, deteriorating the host and also the rank of the tempor-
arily benefited parasite. Of normal societies whose members are
mutually dependent, two kinds may be distinguished — [a) the
organically connected colonies of animals, in which there is a
common nutritive life ; ( b ) those associations which owe their origin
and meaning to reproduction. Of the latter, some do not become
more than domestic, and these are distinguished as conjugal (in

88

PART 1

The Study of Animal Life

which the parents alone are concerned), maternal (in which the
mother is the head of the family), and paternal (in which the male
becomes prominent). But higher than the pair and the family is
what Espinas calls the “peuplade,” what we usually call the
society, whose bonds are, for the most part, psychical.

But let us consider this problem of the evolution of
sociality. The body of every animal — whether sponge or
mammal — is a city of living units or cells. But there are
far simpler animals than sponges. The very simplest
animals, which we call firstlings or Protozoa, differ from all
the rest, in being themselves units. The simplest animals
are single cells ; each is comparable to one of the myriad
units which make up a sponge, a coral, a worm, a bird, a
man.

Here, therefore, there is an apparent gulf. The simplest
animals are units — single cells ; all other animals are com-
binations of units — cities of cells. How is this gulf to be
bridged ? It is strange that evolutionists have not thought
more about this, for on the transition from a unit to a com-
bination of units the possibility of higher life depends.

Every higher animal begins its individual life as a single
cell, comparable to one of the firstlings. This single cell,
or egg-cell, divides ; so do most of the Protozoa. But when
a Protozoon divides, the results separate and live in-
dependent lives ; when an egg- cell divides, the results
of division cohere. Therefore, the whole life of higher
animals depends upon a coherence of units.

But how did this begin ? What of the gulf between
single-celled Protozoa and all the other animals which are
many-celled ? F ortunately we are not left to mere specula-
tion. The gulf has been bridged, else we should not exist ;
but, more than that, the bridge, or part of it, is still left.
There are a few of the simplest animals which form loose
colonies of units, which, when they divide, remain together.
Whether it was through weakness, as I am' inclined to
believe, that the transition forms between Protozoa and
higher animals became strong, or for some hidden reason,
we do not know. Some speak of this coherence of
firstlings as a primal illustration of organic association,

CHAP. V

89

Social Life of Animals

co-operation, surrender of individuality, of sociality at a low
level, but it is unwise to apply these words to creatures
so simple. All that we certainly know is that some of the
simplest animals form loose colonies of units, that the gulf
between them and the higher animals is thus bridged, and
that the bridging depends on coherence. Our first con-

Fig. 19.— Siphonophore colony, showing the float (a), the swimming-bells (l);
the nutritive, reproductive, and other members of the colony beneath. (From
the Evolution of Sex ; after Haeckel.)

elusion, therefore, is, that the possibility of there being any
higher animals depends, primarily at least, not on competition
but on the coherence of units.

Our next step is this : When we study sponges, or
zoophytes, or most corals, or some types usually classed as

9° The Study of Animal Life part i

“ worms,” we see that the habit of forming colonies is
common. Every sponge is a simple sac to begin with,
but it buds off others like itself, and the result is a coherent
colony. A zoophyte is not one individual, but a connected
colony of individuals. Throughout the colony there is one
life ; all the individuals have a common origin, and all are
members one of another. In varying degrees of perfection
the life of the whole is unified. Moreover, the unity is
often increased, not diminished, by the fact that the indivi-
duals are not all alike. There is division of labour among
them ; some may feed while others reproduce, some feel
much while others may be quite callous. Thus, as we
already mentioned, the Portuguese Man-of-War, a colony
of small jellyfish -like individuals, has much division of
labour, and yet there is much, though by no means perfect,
unity of life.

Our second conclusion is that among many animals —
beginning with sponges and ending with the sea-squirts,
which are acknowledged to be animals of high degree —
the habit of forming colonies is common, and that these
colonies, though organically continuous, illustrate the essence
of society ; for in them many individuals of common descent
and nature are united in mutual dependence and help-
fulness.

The next step towards an understanding of the social
relations of animals is very different from that in which we
have recognised the habit of forming colonies. The factor
which we have now to acknowledge is the love of mates.
This also has its history, this also has its prophecies among
the firstlings, but we shall simply assume as a fact that
among crustaceans and insects first, in fishes and amphi-
bians afterwards, in reptiles too, but most conspicuously
among birds and mammals, the males are attracted to the
females, and in varying degrees of perfection enter into
relations of mutual helpfulness. The relations and the
attractions may be crude enough to begin with, but perhaps
even we hardly know to what heights of devotion their
highest expressions may attain. To mere physical fondness
are added subtler attractions of sight and hearing, and

chap, v Social Life of Animals 91

these are sublimed in birds and mammals to what we call
love. This love of mates broadens out ; it laps the family in
its folds ; it diffuses itself as a saturating influence through
the societies of animals and of men. “ Sociability,” Espinas
says, “ is based on the friendliness of mates.”

The fourth step is the evolution of the family. From
monkeys and beavers and many kinds of birds, to ants and
bees and diverse insects, many animals illustrate family
life. There is no longer the physical continuity charac-
teristic of the colony, but there is a growing psychical
unity. It is natural, that the first ties of family life should
be those between mother and young, and should be strong-
est when the number of offspring is not very large. But
even in some beetles, and more notably in certain fishes
and amphibians, the males exhibit parental care and affec-
tion ; while in higher animals, especially among birds, the
parents often divide the labours of the family. “ Children,”
Lucretius said, “ children with their caresses broke down
the haughty temper of parents.”

The fifth step is the combination of families into a
society, such as we find illustrated by monkeys and
beavers, cranes and parrots, and in great perfection by
ants. The members are less nearly related than in the
family, but there may be even more unity of spirit.

I do not say that it is easy to understand how coherence
of units led to the formation of a “ body,” how colonies
became integrated and the labours of life more and more
distributed, how love was evolved from apparently crude
attractions between the sexes, how the love of mates was
broadened into parental and filial affection, or how families
well knit together formed the sure foundations of society ;
but I believe that it is useful to recognise these steps in the
history.

W e hardly know how to express ourselves in regard to
the origin of affection. But I cannot get beyond Aristotle’s
fundamental principle of evolution, that there is nothing in
the end which was not also in the beginning.

Yet we may fairly say that the sociality and helpfulness
of animals are flowers whose roots are in kinship. Off-

92 The Study of Animal Life part i

spring are continuous in nature with their parents ; the
family has a unity though its members be discontinuous
and scattered ; “ the race is one and the individual many.”

9. Advantages of Social Life. — But animals are social,
not only because they love one another, but also because
sociality is justified of her children. “ The world is the
abode of the strong,” but it is also the home of the loving ;
“ contention is the vital force,” but the struggle is modified
and ennobled by sociality.

(a) Darwin's Position. — Darwin observed that “ the
individuals which took the greatest pleasure in society
would best escape various dangers ; while those that
cared least for their comrades, and lived solitary, would
perish in greater numbers.” He distinctly emphasised
that the phrase “ the struggle for existence ” was to be
used in a wide and metaphorical sense — to include all the
endeavours which animals make both selfishly and un-
selfishly to strengthen their foothold and that of their
offspring. But he was not always successful in retaining
this broad view, nor was he led to compute with sufficient
care to what extent mutual aid is a factor in evolution
counteractive of individualistic struggle.

Without losing sight of the reality of the struggle for
existence ; without disputing the importance of natural
selection as a condition of evolution — securing that the
relatively fittest changes succeed ; without ignoring what
seems almost a truism, that love and social sympathies have
also been fostered in the course of natural selection ; we
maintain — (1) that many of the greatest steps of progress
— such as those involved in the existence of many- celled
animals, loving mates, family life, mammalian motherhood,
and societies — were not made by the natural selection of
indefinite variations ; (2) that affection, co-operation, mutual
helpfulness, sociality, have modified the struggle for material
subsistence by lessening its intensity and by ennobling its
character.

(b) Kropotkine' s Position. — Against Prof. Huxley’s con-
clusion that “ Life was a continual free- fight, and beyond
the limited and temporary relations of the family the

ch-ap. v Social Life of Animals 93

Hobbesian war of each against all was the normal state of
existence,” let me place that of Kropotkine, to whose admir-
able discussion of mutual aid among animals I again
acknowledge my indebtedness.

“ Life in societies is no exception in the animal world.
It is the rule, the law of nature, and it reaches its fullest
development with the higher Vertebrates. Those species
which live solitary, or in small families only, are relatively
few, and their numbers are limited. . . . Life in societies
enables the feeblest mammals to resist, or to protect them-
selves from, the most terrible birds and beasts of prey ;
it permits longevity ; it enables the species to rear its pro-
geny with the least waste of energy, and to maintain its
numbers, albeit with a very slow birth-rate ; it enables the
gregarious animals to migrate in search of new abodes.
Therefore, while fully admitting that force, swiftness, pro-
tective colours, cunning, and endurance of hunger and cold,
which are mentioned by Darwin and Wallace as so many
qualities making the individual or the species the fittest
under certain circumstances, we maintain that under any
circumstances sociability is the greatest advantage in the
struggle for life. . . . The fittest are thus the most soci-
able animals, and sociability appears as the chief factor ot
evolution, both directly, by securing the well-being of the
species while diminishing the waste of energy, and indirectly
by favouring the growth of intelligence. . . . Therefore
combine — practise mutual aid ! That is the surest means
for giving to each and to all the greatest safety, the best
guarantee of existence and progress — bodily, intellectual,
and moral. That is what nature teaches us.”

10. A Note on “The Social Organism.” — It is com-
mon nowadays to speak of society as “ the social organism,”
and the metaphor is not only suggestive but convenient
— suggestive because it is profitable to biologist and soci-
ologist alike to follow out the analogies between an organism
and society, convenient because there is among organisms
— in aggregates like sponges, in perfected integrates like
birds — a variety sufficient to meet all grades and views of
society, and because biologists differ almost as much in

94 The Study of Animal Life par* i

their conceptions of an “ organism ” as sociologists do in
regard to “ society.”

It may 'be questioned, however, whether we need any
other designation for society than the word society sup-
plies, and whether the biological metaphor, with physical
associations still clinging to it, is not more illusory than help-
ful. For the true analogy is not between society and an
individual organism, but between human society and those
incipient societies which were before man was. Human
society is, or ought to be, an integrate — a spiritual integrate
— of organisms, of which the bee-hive and the ants’ nest,
the community of beavers and the company of monkeys,
are like far-off prophecies.. And in these, as in our own
societies, the modern conception of heredity leads us to
recognise that there is a very real unity even between
members physically discontinuous.

The peculiarity of human society, as distinguished from
animal societies, depends mainly on the fact that man is a
social person, and knows himself as such. Man is the realis-
ation of antecedent societies, and it is man’s realisation of
himself as a social person which makes human society what
it is, and gives us a promise of what it will be. As bio-
logists, and perhaps as philosophers, we are led to conclude
that man is determined by that whole of which he is a
part, and yet that his life is social freedom ; that society is
the means of his development, and at the same time its
end ; that man has to some extent realised himself in society,
and that society has been to some extent realised in man.

But I am slow to suppose that we, who in our ignorance
and lack of coherence are like the humbler cells of a great
body, have any adequate conception of the social organism
of which we form part.

1 1 . Conclusions. — I would in the main agree with
Kropotkine that “ sociability is as much a law of nature as
mutual struggle ” ; with Espinas that “ Le milieu social est
la condition necessaire de la conservation et du renouvelle-
ment de la vie ” ; and with Rousseau that “ man did not
make society, but society made man.”

CHAPTER VI

THE DOMESTIC. LIFE OF ANIMALS

I. The Love of Mates — 2. Love and Care for Offspring

Winter in our northern climate sets a spell upon life.
The migrant birds escape from it, but most living things
have to remain spell-bound, some hiding with the supreme
patience of animals, others slumbering peacefully, others in
a state of “ latent life ” stranger than death. But within
the hard rind of the trees, or lapped round by bud scales,
or imprisoned within the husks of buried seeds, the life of
plants is ready to spring forth when the south wind blows ;
beneath the snow lie the caterpillars of summer butterflies,
the frogs are waiting in the mud of the pond, the hedgehog
curled up sleeps soundly, and everywhere, under the seeming
death, life rests until the spring. “ For the coming of
Qrmuzd, the Light and Life Bringer, the leaf slept folded,
the butterfly was hidden, the germ concealed, while the sun
swept upwards towards Aries.”

But when spring does come, heralded by returning
migrants — swallows and cuckoos among the rest — how
marvellous is the reawakening ! The buds swell and burst,
the com sends up its light green shoots, the primrose and
celandine are in blossom, the mother humble-bee comes
out from her hiding-place and booms towards the willow
catkins, the frogs croak and pair, none the worse of their
fast, the rooks caw noisily, and the cooing of the dove is
heard from the wood. Then, as the pale flowers are sue-

9 6 The Study of Animal Life part i

ceeded by those of brighter tints, as the snowy hawthorn
gives place to the laburnum’s “dropping wells of fire ” and
the bloom of the lilac, the butterflies flit in the sunshine, the
chorus of birds grows stronger, and the lambs bleat in the
valley. Temperature rises, colours brighten, life becomes
strong and lusty, and the earth is filled with love.

i. The Love of Mates. — In human life one of the
most complex musical chords is the love of mates, in the
higher forms of which we distinguish three notes —
physical, emotional, and intellectual attraction. The love
of animals, however, we can only roughly gauge by
analogy ; our knowledge is not sure enough to appreci-
ate it justly, though we know beyond any doubt that in
many the physical fondness of one sex for another is sub-
limed by the addition of subtler emotional sympathies.
Among mammals, which frequently pair in spring, the
males are often transformed by passion, the “ timid ” hare
becomes an excited combatant with his rivals, while in the
beasts of prey love often proves itself stronger than hunger.
There is much ferocity in mammalian courtship — savage
jealousy of rivals, mortal struggles between them, and suc-
cess in wooing to the strongest. In many cases the love-
making is like a storm — violent but passing. The animals
pair and separate— the females to motherhood, the males to
their ordinary life. A few, like some small antelopes, seem
to remain as mates from year to year ; many monkeys are
said to be monogamous ; but this is not the way of the
majority.

Birds are more emotional than mammals, and their love-
making is more refined. The males are almost always
more decorative than their mates, and excel in the power of
song. They may sing, it is true, from sheer gladness of
heart, from a genuine joy of life, qnd their lay rises
“ like the sap in the bough ” ; but the main motive of
their music is certainly love. It may not always be music
to us, but it is sweet to the ears for which it is meant — to
which in many tones the song says ever “ Hither, my love !
Here I am! Here!” Nor do the male birds woo by
singing alone, but by love dances and by fluttering displays

CHAP. VI

The Domestic Life of Animals 97

it

98 The Study of Animal Life part i

of their bright plumage ; with flowers, bright pods, and
shining shells, the bower-birds decorate tents of love for
their honeymoon. The mammals woo chiefly by force ; the
birds are often moved to love by beauty, and mates often
live in prolonged partnership with mutual delight and help-
fulness. Sixty years before Darwin elaborated his theory of
sexual selection, according to which males have grown more
attractive because the most captivating suitors were most
successful in love, the ornithologist Bechstein noted how the
female canary or finch would choose the best singer among
a crowd of suitors ; and there seems some reason to belie%'e
that the female’s choice of the most musical or the most
handsome has been a factor in progress. Wallace, on the
contrary, maintains that the females are plainly dressed
because of the fate which has befallen the conspicuous during
incubation, and surely they must thus be handicapped. To
others it seems more natural to admit that there is truth in
both Darwin’s and Wallace’s conclusions, but to regard the
males as stronger, handsomer, or more musical simply
because they are males, of more active constitutional habit
than their mates. To this view Mr. Wallace himself inclines.

Compared with the lion’s thunder, the elephant’s trum-
peting, or the stag’s resonant bass, and the ihight which
lies behind these, or with the warble of the nightingale,
the carol of the thrush, the lark’s blithe lay, or the mocking-
bird’s nocturne, and the emotional wealth which these ex-
press, the challenges and calls of love among other classes
of animals are apt to seem lacking in force or beauty. But
our human judgment affords no sure criterion. The frogs
and newts, which lead on an average a somewhat sluggish
life, wake up at pairing time, and croak according to their
strength. The males are often furnished with two reson-
ating sacs at the back of the mouth, and how they can croak
dwellers by marsh -land know ; the North American bull-
frog bellows by himself, and the South American tree-frogs
hold a concert in the branches.

Of the mating of fishes we know little, but there are some
well-known cases alike of display and of tournament. The
stickleback fights with his rivals, leads his mate to

99

chap, vi The Domestic Life of Animals'

the nest by captivating wiles, dances round her in a frenzy,

Malc..“"d £™al? b;rd °f Paradise (Paradise a minor). (From Evolu
tion of Sex , after Catalogue of Dresden Museum.)

arid afterwards guards the eggs with jealous care. The

IOO

PART I

The Study of Animal Life

male salmon, with their hooked lower jaws, fight with their
rivals, sometimes to the death.

Among insects the love-play is again very lively. Like
birds, many of these active animals are very beautiful in
colour and form, especially in the male sex, and a display of
charms has often been noticed. Like birds, though in a
different fashion, some of them are musical, using their
hard legs and wing-edges as instruments. The crickets
chirp merrily, the cicadas “ sing,” and the death-watch taps
at the door of his mate.

In the summer night, when colours are put out by the
darkness, the glow-worm shines brightly on the mossy bank.
In the British species ( Lampyris noctiluca) the winged
male and the wingless female are both luminous ; the latter
indeed excels in brightness, while her mate has larger eyes.
Whatever the phosphorescence may mean to the constitution
of the insect, it is certainly a love-signal between the sexes.
But we know most about the Italian glow-worm (Luciola
italica ), of whose behaviour we have a lively picture — thanks
to Professor Emery’s nocturnal observations in the meadows
around Bologna. The females sit among the grass ; the
males fly about in search of them. When a female catches
sight of the flashes of an approaching male, she allows her
splendour to shine. He sees the female’s signal, and is
swiftly beside her, circling round like a dancing elf. But
one suitor is not enough. The female attracts a levde.
In polite rivalry her devotees form a circle and await the
coquette’s choice. In the two sexes, Emery says, the
colour of the light is identical, and the intensity seems
much the same, though the love-light of the female is more
restricted. The most noteworthy difference is that the
luminous rhythm of the male is more rapid, with briefer
flashes ; while that of the female is more prolonged, with
longer intervals, and more tremulous — illumined symbols of
the contrast between the sexes.

While recognising the genuinely beautiful love-making of
most birds, we did not ignore that the courtship of most
mammals is somewhat rough. So, after admiring the love
dances of many butterflies, the merry songs of the grass-

chap, vi The Domestic Life of Animals ioi

hoppers, and the flashing signals of the glow-insects, it is
just that we should turn to the strange courtship of spiders,
which is less ideal. Of what we may be prepared to find
we get a hint from a common experience. Not long ago I
found in a gorge some spiders which I had never seen
before. Wishing to examine them at leisure, I captured a
male and a female, and, having only one box, put them,
with misgivings, together. When I came to examine
them, however, the male was represented by shreds.
Such unnatural conduct, though by no means universal
among spiders, is common. The tender mercies of spiders
are cruel. We have lately obtained an account of the
courtship of spiders from George W. and Elizabeth G.
Peckham, from whose careful observations I select the
following illustrations :

According to these observers, “there is no evidence that the
male spiders possess greater vital activity ; on the contrary, it is
the female that is the more active and pugnacious of the two.
There is no relation in either sex between development of colour
and activity. The Lycosidce, which are the most active of all
spiders, have the least colour-development, while the sedentary orb-
weavers show the most brilliant hues. In the numerous cases
where the male differs from the female by brighter colours and
ornamental appendages, these adornments are not only so placed
as to be in full view of the female during courtship, but the atti-
tudes and antics of the male spider at that time are actually such as
to display them to the fullest extent possible. The fact that in the
Attida the males vie with each other in making an elaborate dis-
play, not only of their grace and agility, but also of their beauty,
before the females, and that the females, after attentively watching
the dances and tournaments which have been executed for their
gratification, select for their mates the males that they find most
pleasing, points strongly to the conclusion that the great differences
in colour and in ornament between these spiders are the result of
sexual selection.”

These conclusions support Darwin’s position that the female’s
choice is a great factor in evolving attractiveness, and are against
Wallace’s contention that bright colours express greater vitality,
and that the females are less brilliant because enemies eliminate
the conspicuous. It is quite likely that Darwin’s view is true in
some cases ( e.g . these spiders), and Wallace’s conclusion true in
others {e.g. birds and butterflies), or that both may be true in

io2 The Study of Animal Life part i

many cases ; while the fact that the males of these spiders are
always more brilliant than their mates suggests again that the
brilliancy is wrapped up along with the mystery of maleness, which
it is not sufficient to define merely as superabundant vitality, or as
greater activity, but rather as a tendency towards a relative increase
of destructive or disruptive vital changes over those which are
constructive or conservative. But the problem is very complex,
and dogmatic conclusions are premature. We need to know
the chemical nature and history of the pigments to which the
colour is due ; we need to have an approximate balance-sheet
of the income and expenditure of the two sexes. Enough of this,
however ; let us return to the pictures. We talk about romance —
listen to these patient observers :

“ On reaching the country we found that the males of Sciitis
pulex were mature and were waiting for the females, as is the way
with both spiders and insects. In this species there is but little
difference between the sexes. On May 24th we found a mature
female and placed her in one of the larger boxes, and the next day
we put a male in with her. He saw her as she stood perfectly
still, twelve inches away. The glance seemed to excite him, and
he at once moved toward her. When some four inches from her
he stood still, and then began the most remarkable performances
that an amorous male could offer to an admiring female. She eyed
him eagerly, changing her position from time to time, so that he
might always be in view. He, raising his whole body on one side
by straightening out the legs, and lowering it on the other by fold-

CHAP. VI

The Domestic Life of Animals

i°3

ing the first two pairs of legs up and under, leaned so far over as to
be in danger of losing his balance, which he only maintained by
sidling rapidly toward the lowered side. The palpus, too, on this
side was turned back to correspond to the direction of the legs
nearest it. He moved in a semicircle of about two inches, and
then instantly reversed the position of the legs and circled in the
opposite direction, gradually approaching nearer and nearer to the
female. Now she dashes toward him, while he, raising his first pair
of legs, extends them upward and forward as if to hold her off, but
withal slowly retreats. Again and again he circles from side to
side, she gazing toward him in a softer mood, evidently admiring
the grace of his antics. This is repeated until we have counted one
hundred and eleven circles made by the ardent little male. Now
he approaches nearer and nearer, and when almost within reach
whirls madly around and around her, she joining and whirling with
him in a giddy maze. Again he falls back, and resumes his semi-
circular motions with his body tilted over ; she, all excitement,
lowers her head and raises her body, so that it is almost vertical.
Both draw nearer, she moves slowly under him, he crawling over
her head, and the mating is accomplished.” The males are quarrel-
some and fight with
one another ; but after
watching ‘ 1 hundreds
of seemingly terrible
battles ” between the
males of twelve differ-
ent species, the obser-
vers were forced to the
conclusion that “they
are all sham affairs
gotten up for the pur-
pose of displaying be-
fore the females, who
commonly stand by in-
terested spectators.”

“It seemed cruel sport
at first to put eight or
ten males (of Dendry-
phantes capitatus) into
a box to see them fight,
but it was soon apparent that they were very prudent little fellows,
and were fully conscious that ‘ he who fights and runs away will
live to fight another day.’ In fact, after two weeks of hard fighting
we were unable to discover one wounded warrior. . . . The
single female (of Phidippus morsitans) that we caught during the

Fig. 23.— -Two male spiders (Zygoballus bettini )
fighting. (After G. W. and E. G. Peckhnm.)

PART I

104 The Study of Animal Life

Fig. 24. — Male argus pheasant displaying its plumage. (From Darwin.)

summer was a savage monster. The two males that we provided
for her had offered her only the merest civilities when she leaped

chap, vi The Domestic Life of Animals 105

upon them and killed them.” “The female of Dendryphantes
elegans is much larger than the male, and her loveliness is accom-
panied by an extreme irritability of temper, which the male seems
to regard as a constant menace to his safety ; but his eagerness
being great, and his manners devoted and tender, he gradually
overcomes her opposition. Her change of mood is only brought
about after much patient courting on his part.” In other species
(Phi teens tnililaris) the males take possession of young females and
keep guard over them until they become mature. We sometimes
hear of courtship by telephone. In the Epeiridse spiders “ it seems
to be carried on, to some extent at least, by a vibration of web
lines,” as M‘Cook and Termeyer have also observed.

Surely it is a long gamut this, from a mammal’s clamant
call and forcible wooing, or from the sweet persuasiveness
of our singing birds, and the fluttering displays of others, to
the trembling of a thread in the web of a spider. But,
however varied be the pitch of the song and the form of
the dance, all are expressions of love.

Mates are also attracted to one another by odours.
These are best known in mammals ( e.g . beaver and civet)
and in reptiles ; they predominate in the males, and at the
breeding season. They usually proceed from skin glands ;
but we understand little about them. They serve as
incense or as stimulant, but perhaps this usefulness is
secondary. The zoologist Jaeger regards the odoriferous
substances in plants and animals as characteristic of and
essentially associated with each life ; but without going so
far we may recognise that in the general life of flowers
and animals alike odours are very important. We know,
too, that certain odours make much impression upon us ;
such as those of hawthorn and of the hay-field, of newly-
mown grass and of withered leaves, of violet and of
lavender ; and furthermore, that in some mysterious way
some fragrances excite or soothe the system, and have
become associated with sexual and other emotions.

2. Love and Care for Offspring. — Gradual as the
incoming of spring has been the blossoming of parental
love among animals. We cannot tell in what forms it
first appeared in distinctness. We cannot say Lo here 1 or
Lo there ! for it is latent in them all.

io6 The Study of A nimal Life part i

In many of the lower animals the units which begin
new lives arc readily separated from the parent ; but in
others, e.g. some of the simplest, or some by no means
simple “ worms,” and even some insects, the parent life
disappears in giving birth to the young. Reproduction or
the continuance of the species often involves a sacrifice of
the individual life.

It is strangely true, even in the highest forms, that
reproduction, though a blossoming of the whole life, is also
the beginning of death. It is costly, and brings death as
well as life in its train. This is tragically illustrated by
many insects, such as butterflies, who die soon after repro-
ducing, though often not before they have, in obedience to
instinctive impulse, cared most effectively for their eggs —
the results of which they do not live to see. Think also of
the mayflies, or Ephemeridae, who, after a prolonged aquatic
life as larvae, become winged, dance in the sunlight for an
hour, mate and reproduce, and die.

Picture the long larval life in the water, and the short
aerial happiness lasting for an evening or two. Long life,
compared with the span of many other insects, but short
love ; there may be years of patience, and but a day
of pleasure ; great preparations, and the anti-climax
of death. The eggs lie half conscious in the water,
faintly stirred by the growing life within, lapped round
about by peace, — though the trout thin them sorely.
In the survivors the embryos become conscious, awaken
from their rocking, and turn themselves in their cradles.
See the larvae creep forth, wash themselves gaily in
the water, and hungrily fall upon their prey, some
smaller insects. The little “water-wings” grow, and

the air soaks into the blood ; the larvae cast their skins
many times, and hide from the fishes. At length comes
the final moult, and the making of the air-wings, of which
in the summer evening you may see the first short flight as
the insects rise like a living mist from the pool. But even
yet a thin veil, too truly suggestive of a shroud, encumbers
them ; and they rest wearily on the grass or on the
branches of the willow. Watch them writhe and jerk, as if

CHAP. VI

The Domestic Life of Animals T07

impatient, till at length their last encumbrance — their
“ghost,” as naturalists call it — is thrown off. Now the
other life, the life of love, begins. Merrily they dance up
and down, dimpling the smooth water into smiling with a
touch — chasing, embracing, separating. See the filmy fairy
wings, the large lustrous eyes of the males, the tail fila-
ments gracefully sweeping in the dance 1 They never
pause to eat — they could not if they tried ; hunger is past,
love is present, and in the near future is death. The
evening shadows grow longer, — shadows of death to the
Ephemerides. The trout jump at them, a few rain-drops
thin the throng, the stream bears others away. The

mothers lay their eggs in the water, and wearily die forth-
with— -cradle and tomb are side by side ; the males seem

to pass in a sigh from the climax of loving to the other

crisis of dying. But the eggs are in the water, and
the dance of love is more than a dance of death.
Turning homewards, we cannot but think sadly of other
Ephemerides, of patient larval life, of the gradual

revealing of the higher self, of shrouds thrown aside and
wedding robes put on, of hunger eaten up by love, of the
sacrifice of maternity, of cradle and tomb together. Yet
we remember the eggs in the water, the promise of the
future beneath the surface of the stream. Under the horse-
chestnut tree, too, the wind has blown the shed petals like
white foam, but the tree itself is strong like Ygdrasil, and
among the branches a bird sings in the twilight.

Returning in more matter-of-fact mood to parental care,
we need not dwell upon those cases where the young
are simply sheltered for a while about the body of the
mother, hanging to a jellyfish, on some sea-urchins hidden
in tents of spines, in one or two sea-cucumbers half buried
in the skin, adhering to the naked ventral surface of the
common little leech ( Clepsine ), imprisoned in modified
tentacles in some marine worms, carried about in a dorsal
brood-chamber in many water-fleas, or under the curved
tail of higher crustaceans, retained within the gills of
bivalves, and so on. Such adaptations are interesting,
they involve prolonged physical contact between mother

1 08 The Study of Animal Life part i

and offspring, but we are in search of cases where the
parent acts as if she cared for her young.

But this care, as we said, begins very gradually. Thus,
in some lowly crustaceans the young may return to the
brood - chamber of the mother, even after hatching and
moulting ; and young crayfish are said to return to the
shelter of the maternal tail after they have been set adrift.
Strange, too, are the males of some sea-spiders (Pycno-
gonida), who carry about the ova on their legs. It is con-
fidently stated that the headless freshwater mussel keeps
the embryos imprisoned even after the normal period,
until some freshwater fish be present, to which they may
attach themselves ; while some cuttle-fishes are said to exert
themselves in keeping their egg-clusters clean and safe.

But it is among insects, with their full, free life, that we
see the best examples of parental care in backboneless
animals. Some scoff at the “beetle-pricker” or the scara-
beist, — and such genial laughter as that of the Professor at
the Breakfast Table has a healthy resonance, — but those
who scoff have not read Kirby’s Letters, else they would
feel that the student of insects watches at a well-head of
romance and marvel inexhaustibly fresh. What, for
instance, shall we say of the worker-bees, who, though no
parents, tend and nurse the grubs with constant care ; or of
the likewise sexless worker-ants, whose first endeavour
when the nest is disturbed is to save, not themselves, but
the young ; or of the care that flies, moths, and other
insects will take to lay their eggs in substances and situa-
tions best fitted for the future young ? We must think back
into the past history of climatic and other conditions if
we would understand the frequently elaborate provision
which mother insects make for offspring which they never
see ; the ancestors had probably a longer life, and had the
gratification of seeing the result of their labours, and now
the inherited habit works on, perhaps with no vision of
the future. We must also allow that the offspring mis-
takenly deposited by an imperfect maternal instinct would
most likely die, and thus leave the race more select. But
after thinking out these explanations, the facts remain mar-

CHAP. VI

The Domestic Life of Animals 109

vellous. Thus W. Marshall saw an Ichneumon fly
( Polynema natans) remain twelve hours under water,
without special adaptations for such a life, swimming about
with her wings, and depositing her eggs within the larvae of
caddis-flies !

We are accustomed, the same naturalist says, to look
upon a hen which gathers her brood under her wings as a
picture of loving care, but we must recognise that the same
is true of earwigs, spiders, and scorpions. Many of us
have lifted a large stone on the dry bank, and seen the
hurry-scurry of small animals ; there are earwigs among
the rest, and the pale-yellowish young crowd quickly under
the shelter of their mothers, who stand guard with open
pincers. Female spiders, too, so fierce and impatient as
mates, are most “ respectable mothers.” Some make nests,
guard, feed, and even fight for the young ; others carry the
eggs about with them. “ I have often,” Marshall says,
“ made fun of the little creatures, taking away their
precious egg-sac and removing it to a slight distance. It
was interesting to see how eagerly they sought, and how
joyously, one may even say, they sprang upon their ‘ one
and all ’ when they found it again. Sometimes I cheated
them with a little ball of wool of the size, form, and colour
of the egg-sac, which they quickly seized, and as rapidly
rejected.”

Many fishes lay their eggs by hundreds in the water,
and thenceforth have nothing more to do with them, but
even among these cold-blooded animals there are illustra-
tions of parental care. From a bridge over the river you
may be able to watch the female salmon ploughing a
furrow in the gravelly bed, and there laying her eggs, care-
ful not to disturb the places where others have already
spawned. In quiet by-pools you may find the gay male
stickleback guarding the nest which he has made of twined
fibres partly glued together with mucus. There the female
has laid eggs, but he has driven her forth : he will do all
the nursing himself. No approaching enemy is too large
for him to attack ; his courage equals his seeming pride.
When the young are hatched, but not yet able to fend for

I IO

I' ART I

The Study of Animal Life

themselves, his cares are increased tenfold. It is hard to
keep the youngsters in the cradle. “ No sooner has he
brought one bold truant back, than two others are out, and
so it goes on the whole day long.”

We are not clever enough to understand why the males
among many fishes are so much more careful than the
females. For the stickleback is not alone in his excellent
behaviour. The male Chinese macropod {Poly acanthus)
makes a frothy nest of air and mucus, in which he places
his mate’s eggs. He, too, watches jealously over the brood,
and “ has his hands — or rather his mouth — full to recover
the hasty throng when they stray, and to pack them again
into their cradle.” Of all strange habits, perhaps that
is strangest which some male fish (e.g. Arias) have of
hatching the eggs in their mouths ; what.external dangers
must have threatened them before this quaint brooding-
chamber was chosen ! Or is it not almost like a joke to see

the male sea-horse swelling up as
the eggs which he has stowed
away in an external pocket hatch
and mature, “till one day we
see emerging from the aperture a
number of small, almost transpar-
ent creatures, something like
marks of interrogation.” But
some female fishes also carry
their eggs about, attached to the
ventral surface (in the Siluroid
fish, Asftredo), or stowed away in
a ventral pouch (in Solenostoma ,
allied to pipe-fishes), arrange-
ments which recur among amphi-
bians, but on the dorsal surface
of the body.

Amphibians, like fishes, to
which they are linked by many ties, are either quaint or
careless parents. Again, the males assume the responsi-
bilities of nurture. The obstetric frog {Alytes obstetricans),
common in some parts of the Continent, takes the eggs from

Fig. 25. — Sea-horse ( Ilif>po -
campus guttulatus). (From
Evolution t if Sex ; after Atlas
of Naples Station.)

CHAP. VI

I I I

The Domestic Life of Animals

his mate, winds them round his hind-legs, and retires into a
hole, whence, after a fortnight or so, he betakes himself to the
water, there to be relieved by the speedy hatching of his
precious burden. Even quainter is the habit of the male of
a Chilian frog {Rhinoderma darwinii ), who keeps the eggs and
the young in a pouch near the larynx, turning a resonating
sac in a most matter-of-fact way into a cradle. He . is some-
what leaner after it is all over. It is interesting to notice
how similar forms and habits recur among animals of dif-
ferent kinds, like the theme in some musical compositions.
The spiral form of shell common in the simple chalk-forming
Foraminifers recurs in the pearly nautilus ; the eye of a
fish is practically like that of many a cuttle, though the
two are made in quite different ways ; and an extraordinary
development of paternal care may signalise animals so
distinct as sea-spider, stickleback, and frog.

But we must not be unfair to the female amphibians.
Without doubt most of them are willing to be quickly rid
of their eggs or young, and as these are usually very
numerous, the mortality in the pools is of little moment.
In some cases, however, water- pools are less available
than in Britain, and then we find adaptations securing the
welfare of the young. The black salamander of the Alps,
living at elevations where pools are rare, retains her twin
offspring until more than half of the tadpole life is past.
They breathe and feed in a marvellous way within the
body of the mother, and are born as lung-breathers. In
the case of the Surinam Toad (Pifia), the male places half
a hundred eggs on the back of the female, where they
become surrounded by small pockets of skin, from which
the young toads writhe out fully formed. In two other
cases ( Nototrema and Notodelpkys), the above somewhat
expensive adaptation, which involves a great destruction
of skin, is replaced by a dorsal pouch in which the eggs
hatch, an arrangement dimly suggestive of the pouch of
kangaroos and other marsupial mammals.

Fishes and amphibians are linked closely by their likeness
in structure, and, as we have seen, they are somewhat alike
in parental habits ; but how great is the contrast between

I 12

PART I

The Study of Animal Life

the habits of birds and reptiles, in spite of their genuine
blood-relationship. Yet the python coiled round her eggs
is a prophecy of the brooding birds, as in past ages the
flopping Saurians prophesied their swift-winged flight. The
sharpness of the contrast is also lessened by the fact that a
few birds, like the mound-builders, do not brood at all ; while
others, it must be confessed, are somewhat careless. But,
exceptions and criminals apart, birds are so lavish in their
love, so constant in their carefulness, that it is difficult to
speak of them without exaggeration. I am quite willing to
allow that they often act without thought (that is half
the beauty of it) ; nor do I doubt that many species
would have gone to the wall long since in the struggle of
life if the parents had not taken so much care of the young ;
but I would rather emphasise at present the reality that
they do sacrifice themselves for the sake of their young
to a most remarkable degree, and spend themselves not for
individual ends, but for their offspring.

Before the time of egg-laying the birds build their nests,
eagerly but without hurry, instinctively yet with some plas-
ticity, and often with much beauty. On the laid eggs,
which require warmth to develop, the mothers brood,
and though to rest after reproduction is natural, the brood-
ing is not without its literal patience. Among polygamous
birds the males are, as one would expect, more or less
careless of their mates, but most of the monogamous males
are careful either in sharing the duty of brooding or in
supplying the females with food. After the eggs hatch,
the degree of care required varies according to the
state of the young; for many are precociously energetic
and able to look after themselves, while others still require
prolonged nurture. They need large quantities of food,
to supply which all the energies of both parents seem
sometimes no more than adequate ; they may still require
to be brooded over, and certainly to be protected^ from
rain and enemies. After they are reared, they have to be
taught to fly, to catch food, to avoid danger, and a dozen
other arts. With what apparent love— willing and joyous
— is all this done for them !

chap. VI The Domestic Life of Animals 113

Consider the cunning often displayed in leaving or
approaching the nest, in removing debris which would
betray the whereabouts of the young, or in distracting
attention to a safe distance ; remember, too, that some birds

Fig. 26. — Nest of tailor-bird ( Orthotomus bcncttii). (After Brehm.)

will shift either eggs or young to a new resting-place when
extreme danger threatens ; estimate the energy spent in
feeding the brood, sometimes on a diet quite different
from that of adult life ; and acknowledge that the parental
instinct is very deeply rooted, since fostering young not
their own may be practised by orphaned birds of both
sexes. Listen to the bird which has been bereaved, and tell
me is not the “ lone singer wonderful, causing tears ” ?

The female of the Indian and African hornbill nests in
a hole in a tree, the entrance to which she plasters up so
that no room is left either for exit or entrance. The

1

PART I

1 14 The Study of Animal Life

Malays imagined that this was the work of the jealous
male, but it is the female’s own doing. “ She sits,”
Marshall says, “ securely hidden, safe from any carnivore
or mischievous ape or snake stealthily climbing, while the
male exerts himself lovingly to bring his mate those
delightful things in which the tropical forest is rich — fruits
above all, but occasionally a delicate mouse or juicy
frog. He flies with his booty to the tree and gives a
peculiar knock, which his mate knows as his signal, and
thrusts her beak through the narrow window, welcoming her
meal.” At the end of the period of incubation, C. M. Wood-
ford says, “ the devoted husband is worn to a skeleton.”

But animals, like men, have their vices, and birds, gener-
ally so ideal in their behaviour, are sometimes criminals.
Ornithologists assure us that the degree of parental care
varies not only in nearly related species, but also among
members of the same species. We need not lay much
stress on the fact that a bird occasionally slips its egg
into a neighbour’s nest, for when a partridge thus uses a
pheasant’s rough bed, or a gull that of an eider-duck, it
is likely enough that the intruder had been disturbed
from her own resting-place when about to lay. We
approach something different in the case of the American
Ostrich ( Rhea ), the female of which is quite ready to
utilise a neighbour’s burrow ; nor does the owner seem
to object, for all the brooding is discharged by the male,
“ and it is no great art to be patient and magnanimous at
another’s expense.” Again, in the case of the American
Ani ( Crotophaga atii), of whose habits we unfortunately
know little, a number of females sometimes lay their eggs
in a common nest.

We are so glad to hear the cuckoo’s call in spring that
we almost forget the wickedness of the voluble bird. The
poets have helped us, for they have generously idealised, in
fact idolised, the cuckoo, the “ darling of the spring,” “ a
wandering voice babbling of sunshine and of flowers,” a
“sweet,” nay more, a “blessed bird.” But the cuckoos
have hoaxed the poets, for they are even worse than their
legendary reputation of being sparrow-hawks in disguise ;

chap. VI The Domestic Life of Animals 115

they are “greedy feeders,” says Brehm, “discontented, ill-
conditioned, passionate fellows ; in short, decidedly unamiable
birds.” The truth must be told, the cuckoo is an immoral
vagabond, an Ishmaelite, an individualist, a keeper of game
“ preserves.” There are so many males that they have
perverted and thoroughly demoralised the females ; there is
no true pairing ; they are polyandrous. The birds are too
hungry for genuine love, though there is no lack of passion ;
while by voraciously devouring hairy caterpillars they have
acquired a gizzard-fretting feltwork in their stomachs, and
for all I know are cursed by dyspepsia as well as by a con-
stitutionally evil character. It is not quite correct to say
that the cuckoo-mother is immoral because she shirks the
duties of maternity ; it is rather that she puts her young out
to nurse because she is immoral.1 The so-called “ parasitic ”
trick is an outcrop of an egoistic constitution which shows
itself in many different ways. The young bird, “ a dog in
the manger by birth,” evicts the helpless rightful tenants
whether they are still passive in the eggs or more assertive
as nestlings, and as he grows up a spoilt child his foster
parents lead no easy life. But though the poets have been
hoaxed, I do not believe that the nurses of the fledgling
are ; it seems rather as if the naughtiness of their
changeling had some charm.

Of course there is another way of looking at the cuckoo’s
crime. It is advantageous, and there is much art in the
well-executed trick by which the mother foists her several
eggs, at intervals of several days, into the nests of various
birds, which are usually insectivorous and suited for the
upbringing of the intruder. I think there is at least some
deliberation in this so-called instinct. Nor should one forget
that the mother occasionally returns to the natural habit of
hatching her own eggs, — a pleasant fact which several trust-
worthy observers have thoroughly established. Still, in
spite of the poets, the note of this “ blessed bird ” must be
regarded as suggestive of sin !

1 The student will notice that I have occasionally used words
which are not strictly accurate. I may therefore say definitely that I
do not believe that we are warranted in crediting animals with moral,
aesthetic, or, indeed, any conceptions.

PART I

116 The Study of Animal Life

There is much to be said about the domestic life of
animals— their courtship, their.helpful partnership, and their
parentage — but perhaps I have said enough to induce you
to think about these things more carefully. Many of the
deepest problems of biology — the origin and evolution of
sex, the relation of reproduction to the individual and to the
species — should be considered by those who feel themselves
naturally inclined to such inquiries ; moreover, in connection
with our own lives, it is profitable to investigate among
animals the different grades of the love of mates, and the
relation between the rate of reproduction and the degree of
development. First, however^ it were better that we should
watch the ways of animals and seek after some sympathy
with them, that we may respect their love, and salute them
not with stone or bullet, but with the praise of gladdened
eyes.

Ruskin’s translation of what Socrates said in regard to
the halcyon is suggestive of the mood in which we should
consider these things.

Chcerophon. “And is that indeed the halcyon’s cry? I never
heard it yet ; and in truth it is very pitiful. How large is the
bird, Socrates?”

Socrates. “Not great ; but it has received great honour from the
gods, because of its lovingness ; for while it is making its nest, all
the world has the happy days which we call halcyonidse, excelling
all others in their calmness, though in the midst of storm.”

“ We being altogether mortal and mean, and neither able to see
clearly great things nor small, and for the most part being unable to
help ourselves even in our own calamities, what can we have to say
about the powers of the immortals, either over halcyons or night-
ingales ? But the fame of fable, such as our fathers gave it to us,
this to my children, O thou bird singing of sorrow, I will deliver
concerning thy hymns ; and I myself will sing often of this religious
and human love of thine, and of the honour thou hast for it from
the gods.”

Chcerophon. “ft is lightly due indeed, O Socrates, for there is
a twofold comfort in this, both for men and women, in their rela-
tions with each other.”

Socrates. “ Shall we not then salute the halcyon, and so go back
to the city by the sands, for it is time ? ”

CHAPTER VII

THE INDUSTRIES OF ANIMALS

I. Hunting — 2. Shepherding — 3. Storing — 4. Making of Homes
5. Movements

It is likely that primitive man fed almost wholly upon fruits.
His early struggles with animals were defensive rather than
aggressive, though with growing strength he would become
able for more than parrying. We can fancy how a band of
men who had pursued and slain some ravaging wild beast
would satisfy at once hunger and rage by eating the warm
flesh. Somehow, we know, hunting became an habitual art.
We can also fancy how hunters who had slain a mother animal
kept her young alive and reared them. In this or in some
other way the custom of domesticating animals began, and
men became shepherds. And as the hunter’s pursuits were
partially replaced by pastoral life, so the latter became in
some regions accessory to the labours of agriculture, with
the development of which we may reasonably associate the
foundation of stable homesteads. Around these primary
occupations arose the various human industries, with division
of labour between man and woman, and between man and
man.

These human industries suggest a convenient arrange-
ment for those practised by animals. For here again there
are hunters and fishers — beasts of prey of all kinds — pursuing
the chase with diverse degrees of art ; shepherds, too, for some
ants use the aphides as cows ; and farmers without doubt,

PART I

IJ8 The Study of Animal Life

if we use the word in a sense wide enough to include those
who collect, modify, and store the various fruits of the
earth.

In illustrating these industries, I shall follow a charming
volume by Frederic Houssay, Les Industries des Animaux,
Paris, 1890.

1. Hunting. — Of this primary activity there are many
kinds. The crocodile lies in wait by the water’s edge,
the python hangs like a lian from the tree, the octopus
lurks in a nook among the rocks, and the ant-lion
( Myrmeleon ) digs in the sand a pitfall for unwary
insects. The angler-fish ( Lophius piscatorius) is some-
what protectively coloured as he lies on the sand among
the seaweeds ; on his back three filaments dangle, and
possibly suggest worms to curious little fishes, which,
venturing near, are engulfed by the angler’s horrid maw,
and firmly gripped by jaws with backward-bending teeth.
Many animals prowl about in search of easy prey — eggs
of birds, sleeping beasts, and small creatures like white
ants ; others would be burglars, like the Death’s Head
Moth ( Sphinx atropos ) who seeks to slink into the homes
of the bees ; others are full of wiles, witness the cunning fox
and the wide-awake crow. Many, however, are hunters by
open profession, notably the carnivorous birds and mammals.
If these hunters could speak we should hear of many strange
exploits ; such, for instance, as that of a large spider which
landed a small fish. The ins and outs of their ways are
most interesting, especially to the student of comparative
intelligence. Think of the Indian Toxotes, a fish which
squirts drops of water on insects and brings them down
most effectively; several birds which let shells drop from
a height, e.g. the Greek eagle ( Gypaetos barbatus), which
killed ^Tlschylus by letting a tortoise drop on his head;
the grey-shrike ( Lanius excubit or), which spikes its victims
on thorns ; and, strangest perhaps, the slave-making expedi-
tions of the Amazon ants. All strength and wiles not-
withstanding, the chase is often by no means easy ; the
hare grows swift as well as the fox, many grow cautious
like trout in a much -fished stream, scouts and sentinels

chap, vii The Industries of Animals 119

are often utilised, the weak combine against the strong,
and the victims of even the strong carnivores often show
fight valiantly.

2. Shepherding. — Although the ants are the only animals
which show a pastoral habit in any perfection, and that
only in four or five species (e.g. Lasius niger and Lasius
brunneus), I think that the fact is one about which we
may profitably exercise our minds. I shall follow Espinas’s
admirable discussion of the subject.

We may begin with the simple association of ants and
aphides as commensals eating at the same bountiful table.
But as ants discovered that the aphides were overflowing
with sweetness, they formed the habit of licking them, the
aphides submitting with passive enjoyment. Moreover, as
the ants nesting near the foot of a tree covered with
aphides would resent that others should invade their pre-
serves, it is not surprising to find that they should continue
their earthen tunnels up the stem and branches, and should
eventually build an aerial stable for some of their cattle.
Thither also they transport some of their own larvae to be
sunned, and as they carried these back again when the
rain fell, they would surely not require the assistance of an
abstract idea to prompt them to take some aphides also
downstairs. Or perhaps it is enough to suppose that the
aphides, by no means objecting to the ants’ attentions,
did not require any coaxing to descend the tunnels, and
eventually to live in the cellars of the nests, where they
feed comfortably on roots, and are sheltered from the bad
weather of autumn. In autumn the aphides lay eggs in
the cellars to which they have been brought by force or
coaxing or otherwise, and these eggs the ants take care of,
putting them in safe cradles, licking them as tenderly as
they do those of their own kind. Thus the domestication
of aphides by ants is completed.

Now what is the theory of this shepherding ? (1) W£

have no warrant for saying that the ants have deliberately
domesticated these aphides, as men have occasionally
added to the number of their domesticated animals. It
does not seem to me probable that even primitive man

iso The Study of Animal Life tart i

was very deliberate in the steps which led to the first
domestications. (2) Nor is it likely that the process
began in a casual way, and that it became predominant
in four or five species in the course of natural selection.
For the habit is more a luxury than a necessity, and
it is not likely to have been evolved before the estab-
lishment of the sterile caste of workers, who have no means
of transmitting their experience. Moreover, initial steps are
always difficult to explain on this theory. (3) The theory
which seems to me warrantable is that the habit arose by
a gradual extension of habits previously established, that it
was neither deliberate nor casual in its origin, but a natural
growth, beginning- neither in a clever experiment nor in a
fortunate mistake of an individual worker ant, but the
outcome of the community’s progressive development in
“ intellectual somnambulism,” helped in some measure by
the sluggish habits of the aphides. And, if you wish, the
formula may be added, “ which was justified in the course
of natural selection.”

3. Storing. — Not a few animals hide their prey or their
gatherings, and with marvellous memory for localities
return to them after a short time. But genuine storing
for a more distant future is illustrated by the squirrels, which
hide their treasures like misers. Many mice and other rodents
do likewise, and in some cases the habit seems to become
a sort of craze, so large are the supplies laid in against the
winter’s scarcity. Very quaint are the sacred scarabees
( Ateucus sacer), which roll balls of dung to their holes, and
sometimes collect supplies at which they gnaw for a couple
of weeks. Some ants (e.g. Atta barbard) accumulate stores
of grain, occasionally large enough to be worth robbing ;
and there is no doubt that they are able to keep the seeds
from germinating for a considerable time, while they stop
the germination after it has begun by gnawing off plumule
and radicle and drying the seeds afresh. Dr. M ‘Cook’s
account of the agricultural ant of Texas (Pogotnyrmex
barbatus) gives even more marvellous illustrations of
farming habits, for these ants to a certain extent at least
cultivate in front of their nests a kind of grass with a rice-

chap, vii The Industries of Animals 121

like seed. They cut off all other plants from their fields,
and thus their crops flourish.

But animals store for their offspring as well as for
themselves. The habit is very characteristic of insects,
and is the more interesting because the parents in many
cases do not survive to see the rewards of their industry.
Sometimes, indeed, there is no industry, for the stores of
other insects may be utilised. Thus a little beetle ( Sitaris
muralts) enters the nest of a bee ( Anthophora pilifera) and
lays its eggs in the cells full of honey. More laudable are
the burying- beetles ( Necrophorus ), which unite in har-
monious labour to bury the body of a mouse or a bird,
which serves as a resting-place for their eggs and as a
larder for the larvae. The Sphex wasp makes burrows,
in which there are many chambers. Each chamber con-
tains an egg, and is also a larder, in which three or four
crickets or other insects, paralysed by a sting in the nervous
system, remain alive as fresh meat for the Sphex larva
when that is hatched. After the Sphex has caught and
stung its cricket and brought it to the burrow, it enters
at first alone, apparently to see if all is right within.
That this is thoroughly habitual is evident from Fabre’s
experiment. While the Sphex was in the burrow, he stole
away the paralysed cricket, and restored it after a little ;
yet the wasp always reconnoitred afresh, though the trick
was played forty times in succession. Yet when he substi-
tuted an unparalysed cricket for the paralysed one,
the Sphex did not at once perceive what was amiss, but
soon awoke to the gravity of the situation, and made a
fierce onslaught on the recalcitrant victim. So it is not
wholly the slave of habit.

4. Making of Homes. — Houssay arranges the dwellings
of animals in three sets — (a) those which are hollowed
out in the earth or in wood ; ( b ) those which are
constructed of light materials often woven together ; and
( c ) those which are built of clay or similar material. We
may compare these to the caves, wigwams, and buildings
in which men find homes.

Burrows are simplest, but they may be complex in

122 The Study of Animal Life part i

details. Those of the land-crabs ( Gecarcinus ), the wood-
cutting bees ( Xylocopa ), the sand-martens, the marmots, the
rabbit, the prairie dogs, illustrate this kind of dwelling in
various degrees of perfection.

The male stickleback ( Gasterosteus)^ weaves and glues

the leaves and stems of water-plants ; the minutest mouse
(Mus minutus) twines the leaves of rushes together ; the
squirrel makes a rougher nest ; the orang-utan and the
chimpanzee construct shelters among the branches ; but the
nests of many birds are by far the most perfect works of
animal art. -

Of buildings, the swallows’ nests by the window, and the

Fig. 27.

— Swallows ( Chelidonaria urbica ) and their nest. (After Brehm.)

chap, vii The Industries of Animals 123

paper houses which wasps construct, are well known ; but we
should not forget the architecture of the mason-bees, the
great towers of the termites, and the lodges of the beavers.

Perhaps I may be allowed to notice once again, what I
have suggested in another chapter, that \yhile many of the
shelters which animals make are for the young rather than
for the adults, the line of definition is not strict, and some
which were nests to begin with have expanded into homes
— an instance of a kind of evolution which is recognisable
in many other cases.

5. Movements, — But animals are active in other ways.
All their ways of moving should be considered — the marvel-

Fig. 28. — Flight of crested heron, ten images per second. (From Chambers’s
Encyclop . ; after Marey.)

lous flight of birds and insects, the power of swimming
and diving, the strange motion of serpents, the leap, the
heavy tread, the swift gallop of Mammals. All their
gambolings and playful frolics, their travels in search of
food, and their migrations over land and sea, should be
reckoned up.

Most marvellous is the winged flight of birds. As a
boat is borne along when the wind fills the sails, or when
the oars strike the water, and as a swimmer beats the
water with his hands, so the bird beating the air backwards
with its wings is borne onward in swift flight. But the
air is not so resistent as the water, and no bird can float in
the air as a boat floats in the water. Thus the stroke has

124 The Study of Animal Life parti

a downward as well as a backward direction. When there
is more of the downward direction the bird rises, when there
is more of the backward direction it speeds forward ; but
usually the stroke is both downwards and backwards, for
the lightest bird has to keep itself from falling as it flies.
The hollowness and sponginess of many of the bones com-
bine strength of material with lightness, and the balloon-
like air- sacs connected with the lungs perhaps help the
birds in rising from the ground; but, buoyant as many birds
are, all have to keep themselves up by an effort. But the
possibility of flight also depends upon the fact that the
raising of the wing in preparation for each stroke can be
accomplished with very little effort ; the whole wing and
its individual feathers are adjusted to present a maximum
surface during the down-stroke, a minimum surface during
the elevation of the wing. There are many different kinds of
flight, which require special explanation- — the fluttering of
humming-birds, the soaring of the lark, the masterful
hovering of the kestrel, the sailing of the albatross. The
effortless sailing motion of many birds is comparable to
that of a kite, “ the weight of the bird corresponding to the
tail of the kite ; ” it is possible only when there is wind or
when great velocity has been previously attained.

Fig. 29. — From St. John’s Wild Sports,

PART II

THE POWERS OF LIFE

CHAPTER VIII

VITALITY

l. The Task of Physiology — 2. The Seat of Life — 3. The Energy of
Life — 4. Cells, the Elements of Life — 5. The Machinery of
Life — 6. Protoplasm — 7. The Chemical Elements of Life — 8.
Growth — 9. Origin of Life

i . The Task of Physiology. — So far we have been
considering the ways of living creatures, as they live and
move, feed and grow, love and fight ; as they build their
homes and tend their young. We shall now turn to
the inner mysteries, and seek, so far as we may, to fathom
the wisdom of the hidden parts. We shall describe the
machinery — the means by which the forces of life cause
those movements by which we recognise their presence.

This study is called physiology ; and the plan of our
sketch of present knowledge will be as follows : We shall
first try to realise what we mean by life ; we shall then
limit ourselves to the consideration of certain kinds of life,
and attempt to make plain in what parts of all living
creatures are the forces of life most active. Having done
this, we shall describe the life processes of the simplest
creatures, and then those of the higher animals.

It is not easy to say clearly what we mean by life ; but
we recognise as one of its characteristics the power of
movement.

1 26

PART 11

The Study of Animal Life

Still, this gives no distinction between the blowing of
wind and the life of man ; but the other characteristics of
life will be realised as we proceed in our analysis ; it is
certain that without movement there is no life. Further
thought may lead us to define life as that “complex of
forces which produces form.” Thus the star-like crystals
of a snowflake, the diamond drops of dew, the over-
shadowing mountains, would all be imaged in our
minds as living, though of more lowly life than the
lichens of the bare hill-tops, the grass of the plains, or man
himself. We have no space here to trace the connections
between such an idea and the beliefs of all simple peoples,
and the inspirations of all poets, but the similarity is
evident, and the usefulness in philosophy of such general-
ised conceptions is great.

But the physiology which we shall sketch here will be a
narrower one ; it will be confined to the life of plants and
animals, and we shall attempt to show precisely how that
life is separated from the life of the dust and of the air.

2. The Seat of Life.— Now in what parts within the
living body are the life forces most actively at work ?

When we look at any living creature we are all too
willing, even if the wonder of life stirs within us, to remain
satisfied with a vague apprehension of a mystery. It is
strange that so many generations of men passed away
before any steps were taken towards a conception of the
intimate material processes of life and growth and death.
The moving train has been watched, but the engine and
the stoker have been almost unnoticed.

Let us consider the growth of a tree. The outward manner
of its growth we can observe, a few superficial details of its
inner life we already know, and of this knowledge we may
look for great expansion, but the ultimate processes of its
life are still a complete mystery to us.

The tree is alive, but is it all alive ? Cut a stake from
its heart and plant it in the ground ; it will not grow, and
shows no signs of life, but we are not puzzled ; the tree, we
think, can only live as a whole, and we know how easily
most living things are killed by local injuries. But if we

chap, viii Vitality 127

cut a stake from the outer part of the tree, leaving the
bark on, and set it in the ground, it may happen that buds
will appear, pushing through the bark, and stretching out
into shoots.

There is a mystery for us to begin with : some parts of
a tree may have a life of their own. Indeed, we all know
that gardeners do not rear geraniums and other plants from
seeds, but from cuttings. Potatoes, as we know, will give
origin to new plants, and even small parts of potatoes will
do so. Roses are grafted into the stems of the wild brier,
and in this way two life- currents are mingled. We may
remember, too, that all seeds are only parts that have
become separated from the parent plant. We ourselves,
formed in the darkness of the womb, were separated at
birth from the mothers who bore us.

Let us think of the seeds of plants for a little. Formed
in the warmth and brightness of the summer sun, ripened in
the glow of autumn, they fall to the ground, are carried
hither and thither by trickling runlets of water, by the
winds, by animals, and scattered over new pastures.
Through the long chill of winter they remain asleep ; but
not dead, — slow preparation is being made for the new
day. With the warm winds of spring — when the birds
come back to us and sing their first songs of love and
courtship — the countless buds of the woods, the gardens,
and the hedgerows, all the seeds we sowed in the autumn,
all the corn we scattered in the first hours of the new
morning, awake ; the buds burst, the tiny leaves unroll ; in
the seeds there is a great activity, — the slender shoots
stretch forth — spring passes into summer — and we await the
harvest.

3. The Energy of Life. — What is the cause of this
strength of life ? How is it that in an acre of forest tons of
solid matter are lifted high into the air, while the branches
waving under the blue sky seem to enjoy the brightness of
the sun after the gloom of winter ? This assertion of the
poets of the gladness of nature at the springtime is no mere
wandering fancy, it is simple truth ; the intensity of life at
that time is due entirely to the greater warmth of the air

PART II

128 The Study of Animal Life

and increased brightness of the sun ; and since there is no
reason why we should not believe in a simple order of
consciousness in all simple creatures, that consciousness
would certainly become gladness with increased vigour of
life, just as it is with ourselves.

The energy of life, we say, is due to the energy reaching
us from the sun ; but how is the radiant energy of the ether
used to place the growing shoots on the forest tops, and how
is it transformed into the potential energy of wood and
other substances ? Our trains move by virtue of the
energy stored in the coal ; we burn that in a certain
place and get expansive energy of steam, which by
mechanical arrangements we convert into the moving
energy of the engine ; but where is the boiler, and
where the machinery in the plant, by which the energy
of the sun’s rays is transmuted into life ? The partial
answer to this riddle has been found. If we break a
newly-grown branch we find the tissues filled with a watery
slimy sap. If we open a bud we find the slimy stuff again ;
under the bark of trees we find it once more ; it is within
the tissues of a bulb, and in growing seed ; indeed, in all
those parts of a plant which are capable of independent
life we always find what we may call for the moment
this slimy sap ; while in the hard inner parts of the tree,
which we know can live no more, we find nothing of the
kind, — such tissues are quite empty. Life, therefore, we
find to have something to do with a certain substance, and
this is the first step towards understanding the machinery
we have spoken of ; we have, as it were, found that the
movement of the train is due to the engine, but we do not
understand that engine.

4. Cells, the Elements of Life— Let us leave the trees
now for a little, and turn to the simplest of all living
creatures, which live in water and in damp places. They
are so small that only a few of the larger ones can be seen
as tiny specks moving about in the water in which they
live. But they can be seen quite easily with a microscope.
We find them to be little transparent drops of living
matter. They are not really drops ; many of them have

chap, viii Vitality 129

distinct shapes, others constantly change their form. They
move, indeed, by a kind of flowing ; one part of their body is
pushed out and a part on the farther side drawn in. Some
of these lowly creatures have skeletons or shells of lime or
of flint. Great numbers of these shells, when the little
inmates are dead, form beds of chalk and ooze. Now
all living creatures begin life in this way ; at first they
are tiny masses of a jelly-like translucent stuff. Each
mass gets a skin or surrounding wall ; if fed, it grows
larger, and a wall is built up inside it, making its house a
two-roomed one. This process goes on and on ; the whole
mass grows larger and larger, and becomes divided up into
a corresponding number of compartments. The chambers
are not quite separated ; there are always holes left in the
walls, through which strands of the jelly-like stuff pass, and
so all of them are connected. The divisions in each
separate kind of animal or plant take place in a special
way, until at last the whole body is built up, with all its
peculiarities of form and internal arrangement. The cells
of an animal’s body do not, however, form walls as definitely
as do those of plants.

In an ordinary plant there are millions of those com-
partments ; they are called cells, from their likeness in
general appearance to the cells of a honeycomb ; and the
enclosed stuff that we have spoken of as jelly is called
protoplasm, because it is believed that the first living things
that were formed were little drops of jelly-like stuff, not
unlike that within the cells, or composing the animalculae in
water. Protoplasm, wherever it occurs, from the highest
to the lowest forms of life, is supposed to have, within
certain limits, a similarity of nature.

In some plants the cells are large enough to be visible
to the naked eye, but the cells of most plants and animals
are so small that they can only be seen with a microscope.

We can now give a complete answer to the question,
What parts of a tree are alive ? It is only the protoplasm
of the cells. The walls of the cells are more or less dead.
As the cells grow older and larger, and the walls become
thicker, the amount of protpplasm within gets relatively

K

130 •

PAIU' II

The Study of Animal Life

less ; at last it slowly dies and withers away ; the cells are
left empty ; and that is why the stake cut from the old hard
part in the middle of the tree could not grow, — it was quite
dead.

5. The Machinery of Life. — We have found that, in
some way, the protoplasm within the cells is the machinery
of life. For simplicity, we shall speak of protoplasm as
living matter. This living matter in plants is such that
it can transform the energy of sunlight into potential energy
of complicated substances such as wood. This trans-
formation of energy is one of the chief labours of plants in
the world. A great deal of the energy that reaches their
living matter is used for their own upward growth ; so that,
as we said before, thousands of tons of matter are every
year, over every acre of forest, raised high into the air.

In animals the living machinery is in certain ways of a
different nature. An animal eats the substances made by
the plant ; the potential energy stored in these is used by it
in moving about, and so transformed into energy of motion.
The life of plants is chiefly shown in the storage of energy,
the life of animals in the use of that store. Chiefly we say,
for plants also move to a slight extent ; as a whole, when
they twine around a tree or bend towards the sun ; and in
their parts when the sap rises and falls. Animals also, to a
slight extent, build up substances of high potential energy.

So far all is certain, but when we inquire by what arrange-
ment of parts the living matter is able to be a machine for
the transformation of energy, we are unable to form any con-
ception. Soon after the discovery of the cells and their living
contents, certain philosophers, who must have very faintly
realised the necessary physical conditions, arguing from the
analogy of machines as men construct them, supposed that
the activities of the living machinery could be deduced
from the structural arrangements of the cells ; they sup-
posed that the living matter, a part within it called the
nucleus, and the cell- wall, were in themselves the parts of
a machine, and that the various activities of the cells were
due to varying shapes of wall, and disposition of its visible
parts. It was soon shown, however, that the wall was not

chap, viii Vitality 131

a necessary part of the living matter, and that the nucleus
did not always occur. The cell is a machine, not in virtue
of the disposition of its visible parts, but as a consequence
of the arrangement of its molecules. We know this much
about the living machinery, that it is far more perfect
than the machinery of our steam-engines, the perfection of a
machine being measured by the relation between the energy
which enters it and that which leaves it as work done.

“Joule pointed out that not only does an animal much
more nearly resemble in its functions an electro-magnetic
engine than it resembles a steam-engine, but also that it is
a much more efficient engine ; that is to say, an animal,
for the same amount of potential energy of food or fuel
supplied to it — call it fuel to compare it with other engines
— gives you a larger amount converted into work than any
engine which we can construct physically.” And Joly has
expressed the contrast between an inanimate material
system and an organism as follows : “ While the transfer
of energy into any inanimate material system is attended
by effects retardative to the transfer and conducive to dis-
sipation, the transfer of energy into any animate material
system is attended by effects conducive to the transfer
and retardative of dissipation.”

It is from protoplasm that we must start in our study
of living machinery ; let us see how far we can attain to
exact conceptions of its nature. We will first describe
shortly what is known as to the structure of protoplasm or
living matter, chiefly to show how hopeless is any attempt
at a solution of the problem in terms of visible structure.
The powers of the microscope are limited by the physical
nature of light, and that limit has already nearly been
reached ; and yet we know the structure of matter is so ex-
cessively minute that within the compass of the finest fibre
visible with the microscope there is room for the most intri-
cate structural arrangements.

6. Protoplasm. — Protoplasm used commonly to be de-
scribed as a structureless mass ; we now know that it often
has a structure somewhat like a heap of network. It is a
complex of finely-arranged strands, with knots or swellings

132 The Study of Animal Life i-art ii

at the junctions of the strands, and with, in each cell, one
or more central and larger swellings, probably of a highly
specialised nature, called nuclei. The size of the meshes
varies, and they are filled “ now with a fluid, now with a
more solid substance, or with a finer and more delicate
network, minute particles or granules of variable size being
sometimes lodged in the open meshes, sometimes deposited

Fig! 30 — Adjacent animal cells showing the nucleus, the protoplasmic network,
and the bridges vitally uniting cell and cell across the intervening inter-
cellular substance. (From the Evolution of Sex ; after Pfitzner.)

in the strands of the network. Sometimes, however, the
network is so close, or the meshes filled up with material so
identical in refractive power with the bars or films of the
network, that the whole substance appears homogeneous.”
The only means we have of getting any further knowledge
of this arrangement is by staining it with various dyes, and
observing the effects of the dyes upon the vai'ious parts.
“ Analysis with various staining and other reagents leads to

chap, vni Vitality 133

the conclusion that the substance of the network is of a
different character from the substance filling up the meshes.
Similar analysis shows that at times the bars or films of the
network are not homogeneous, but composed of different
kinds of stuff ; yet even in these cases it is difficult, if not im-
possible, to recognise any definite relation of the components
to each other such as might deserve the name of structure.”
Plainly there is not much light to be got by further investi-
gations in this direction. Ordinary chemical analysis, too,
is of little avail ; for how can we say what parts of the
mass are alive, even if we could separate part from part ? Is
it only the meshwork that is really living matter, or are the
granules part of it, or are the fluid contents the chiefly vital
substance ?

Let us turn now to the activities of the living stuff, and
see what we can learn from them. We have already spoken
of one of the activities of living matter, especially of plant
protoplasm, that of surrounding itself with a wall. Now we
might at first be inclined to suppose that the wall was simply
due to a hardening and drying of the soft substance at those
places where it touched the air. It is possible that that may
have been the stimulus which caused, as a reaction, the
wall-making at the dawn of life, and which may still have
some connection with it ; but what we have to take note of
is the fact that the walls, as they are made by the higher
plants, have always a definite structure and chemical nature.

If we examine the cells of the leaves of a plant growing
in the sunlight, we find the green colouring matter to be
generally collected in little rounded masses. Looking more
closely, we find it to be the fluid which fills the meshwork
of the masses. At certain points in the meshwork we find
minute masses of starch constantly being formed. They seem
to pass along the strands and collect in the centre of the net-
work, until quite a large mass of starch is accumulated there.
If we examine the plant at night, some time after darkness
has set in, we find no traces of starch in the cells of the
leaves. There is evidence that the starch has been trans-
formed into sugar, and can then, by osmotic and perhaps
by other processes, be removed from the leaves, and

1 34

PART II

The Study of Animal Life

carried by the vessels to all parts of the plant. So we get
a first notion of how a plant is fed. Starch is a com-
pound containing carbon and the elements of water. The
carbon, we know, comes from the carbonic acid of the air ;
the water is absorbed by the roots from the soil. In some
way the living matter of the cells, by means partly of the
green colouring matter, is able to transform the energy of the
sun’s rays into potential energy of a combustible substance
— starch ; so we get clear evidence of a machinery for the
transformation of energy. We have taken a plant as our
example throughout, partly because the cells are more
evident than in animals, and partly because the chemical
processes give evidence of a transformation of kinetic into
potential energy more clearly than do those of animals ; for
the animals eat the plants, and so by using the potential
energy of plant substance are able to live and move.

We have now some idea of the sources of the energy of
life. Plants get their food from the air by their leaves, and
from the soil by their roots, which absorb water and salts
dissolved in water. By aid of the energy of sunlight they
build these up into complex substances, which they use for
the growth of their living matter, for the formation of sup-
porting structures, and for other purposes. Animals eat
these substances. They build up their own bodies of living
matter and supporting structures, and they move about.

In order to get a clearer notion of the nature of living
matter we must attempt to trace the manner in which these
various substances are built up. We have first to discover
what are the substances that are made. In all living
creatures there are, in addition to water and salts, such as
common salt and soda, three groups of stuffs : —

Carbohydrates , such as starch and sugar, made of carbon
with hydrogen and oxygen in the same proportions as they
occur in water ;

Fats — substances containing the same three elements,
but with a smaller proportion of oxygen ;

Proteids — substances containing always carbon, hydrogen,
oxygen, and nitrogen, with a small percentage of sulphur.

The constitution of proteids is difficult to determine.

CHAP. VIII

T35

l ’ itality

The above elements are always present, and in proportions
which vary within narrow limits ; but in addition to
these substances there seem to be always present others
which, when the proteids are burnt, remain as ash in the
form of salts chiefly chlorides of sodium and potassium, but
also small quantities of calcium, magnesium, and iron, as
chlorides, phosphates, sulphates, and carbonates. The mole-
cule of a proteid must be very complex ; thus that of albumen
is, at its smallest, C^, H481, Ng0, Og3,S2; most probably it
is some multiple of this.

The food-stuff's of plants, then, are salts, water, and car-
bonic acid, and a certain amount of oxygen. Of these, by
means of the sun’s energy, they build up complex substances
— carbohydrates, fats, proteids, which, with salts, water, and
oxygen, serve as the food of animals. The living matter,
the machinery by which all this is done, is, if it can be
classed at all, a proteid. But this only means that all
living matter contains the five essential elements and some
others which in the ash exist as salts.

The various services which the different food-materials
are set to within the body will be described later, when we
are considering the details of the animal economy. Here
we shall take note of the elements that enter into the
construction of the food-stuff's.

7. The Chemical Elements of Life. — There are sixty-
eight elements to be found in varying abundance upon the
earth, but by analysis of the food-stuff's and of living matter
itself, we find that only twelve of these occur with any con-
stancy in organisms. They are carbon, hydrogen, oxygen,
nitrogen, sulphur, phosphorus, chlorine, potassium, sodium,
calcium, magnesium, and iron.

Now nine of these elements form sixty-four per cent by
weight of the earth’s crust; while aluminium and silicon,
substances that are only very occasionally found in living
creatures, form thirty-five per cent, being the chief consti-
tuents of quartz and felspar, sand and clay, in short the
greater part of all rocks. All the other elements, three of
which — hydrogen, nitrogen, and phosphorus — enter into
life, form the remaining one per cent.

T 3 ^ The Study of Animal Life part ii

Since the ultimate analysis of the objective side of life
seems to show that life is to be pictured as matter in an
unstable and constantly altering condition, it will be of
interest to find the conditions that determine which of the
elements are to take part in it.

It seems that matter in order to enter into life must be —

(i) Common, (2) rqobile, that is capable of easily
entering into solution or becoming gaseous, and (3) capable
of forming many combinations with other elements.

Nine of the elements fulfil the first condition ; a tenth,
nitrogen, is the chief constituent of the atmosphere ;
while hydrogen is present everywhere in water. Why do
not aluminium and silicon take their share in life ? Because
they do not fulfil conditions (2) and (3). Their oxides are
quartz and aluminia, two of the hardest substances known.
Emery and ruby are two forms of aluminia ; while the oxide
of carbon, the source of all the carbon used in life, is a gas.

Carbon, which takes so great a part in life processes that
the chemistry of organic substances is commonly spoken of
as the chemistry of the compounds of carbon, fulfils all three
requirements in an eminent degree. For although in its
pure form a solid, and sometimes a very hard substance, yet
it readily forms an oxide which is present in the atmosphere,
and, as we know, serves as one of the chief foods of plants.
Its power of entering into combination with other elements
is practically infinite. Nitrogen, although by itself an inert
form of matter, is able to combine with carbon compounds
and add fresh complexity.

It is easy to see why water is so important in life. It
dissolves the other substances, and so allows them to come
into closer contact, and to change in position more easily,
than if they were solid. So the first stuff that was complex
and unstable enough to be properly described as living was
almost certainly formed in water, long ago, when the condi-
tions of greater heat, and consequently greater mobility of
all substances, made chemical changes more active.

The importance of the solvent power of water in a com-
plex organism is obvious when we think of the blood, the
great food stream and drain. It is shown in an interesting

chap, vni Vitality 137

way by the suspended animation of a dried seed, which will
remain for years dormant, but ready when moistened to
spring into active life.

How, then, are these substances built up into living
creatures ? Let us, that we may see this matter clearly,
think for a moment of the conditions of life of the simplest
creatures, the formless masses of living matter. All that
the simplest plants need is water holding oxygen, carbonic
acid, and salts in solution. Out of these simple materials,
by the magic touch of their living bodies, they can build up

the complex matter of which those bodies are made ; so that
they can grow and divide until there may be hundreds in
place of a single one. The image we must form of this
increase of living matter is that step by step substances of
an ever-growing complexity are made, one from the other,
until at last a substance so unstable is made that it begins
to break down into simpler forms of matter at the least
deviation from the precise conditions in which it was made,
and perhaps also with a ferment-like action causes changes

VART II

138 The Study of Animal Life

in all that it touches; and this we call the living matter.
As this living matter breaks down into simpler substances,
or as it causes surrounding substances to break down,
energy is set free for use in movement. We may make
a diagram of this process. The steps go up and down; the
top one we call protoplasm (Fig. A). This shows only one
line of ascent and one of descent. There may be many, all
going on at the same time, as is shown in Fig. B. But
these are much too simple ; they show continuous ascending
and descending stairs, but each step does not really result
directly from the one below, but must result from two or
more stairs meeting ; and at each meeting there must be
substances formed which are useless, and begin to break
down, or are cast out of the system at once.

8. Growth.— The power of growth, of adding to itself
substance of the same nature as itself, is the real mystery
of living matter. A crystal grows out of its solution, the
star or pyramid is built up with perfect regularity, but the
process is much simpler than the growth of living matter.
The substance of which it will be formed is already there,
but the' protoplasm has to make its own substance as it
grows. This is the true difference between the two pro-
cesses, and not, as is usually stated, that a crystal grows by
depositing matter on its surface, while a cell grows by putting
matter within itself. For when two cells fuse, which often
occurs, growth is really as much by aggregation as in the
case of a crystal, and such manner of growth is made
possible simply because the two cells are masses of matter
of equal complexity. But when less complex matter is given
to a cell it cannot add that matter to itself until it has been
transformed into substance as complex as itself. This
change can only be effected within the little laboratory of
the cell itself. The fact that the growth of a crystal may
be endless, while that of a cell is limited, which is usually
cited as the distinctive difference, is a consequence of the
necessity of the protoplasm for forming its own substance
within its own substance. For when a cell grows in size
the ratio of its surface to its volume constantly decreases ;
and therefore, since new material can only be absorbed

chap, viii Vitality 139

through the surface, there must be a certain size of cell at
which the rate of absorption is just sufficient for the nourish-
ment of the protoplasm. Beyond this point a cell cannot
grow ; but if it divides, then the mass to be fed remains the
same, while the absorbing surface is increased. This, then,
is the necessitating cause of cell-division. But it would be
unwise to suppose that there are not other causes that help
to produce this result, which has as a consequence the
possibility of immense variety of disposition of the daughter
cells, and therefore of organic forms ; for, to begin with, a
more obvious means of obtaining increased surface would
be for the cell merely to become flattened or to spread out
irregularly, which, indeed, we see in many of the Protozoa.

Since their growth implies cell-division as one of its con-
sequences, and since cell-division is the basis of reproduc-
tion, synonymous, indeed, in the Protozoa with reproduc-
tion, we get the idea of successive generations of animals as
merely the continued growth of former generations. This
makes intelligible to us all the facts of heredity which are
so surprising if we conceive of each generation as a number
of untried souls that have left some former dwelling-place to
come and live among us. Our children are, in truth, abso-
lutely portions of ourselves. If this be so, we must imagine
in the ovum — the tiny mass of protoplasm from which we
are formed by continued division — a most extraordinary
subtlety of constitution.

Try to picture the complexity of the arrangement of parts.
There are two tiny masses of protoplasm ; so far as we can
see they are the same, yet from one will grow a man, from
the other a tree. If the germ that will grow into a human
being could only properly be fed outside the body of the
mother, so far as we know it might leave that body as
an almost invisible cell, and would grow and divide, add
cell to cell, until the creature was fully formed — sculp-
tured out of dust and air. Our early life within the womb,
our nourishment by the blood of our mother, is only nature’s
way of preserving us from injury. What we shall be is
already marked out before the egg begins to grow.

It is only the highest animals who are thus shielded.

T4° The Study of Animal Life part ii

The birds cover their eggs with their wings. The butterfly
lays hers where the grubs will find their food. The star-
fish cast theirs adrift in the sea. The same story is true
of the flowers. They are the nursing mothers. In their
heart the young plant grows until the first leaves appear ;
not till then does it drop away, and not without food
prepared and placed ready for use — enclosed in what we
call the seed. But the seaweed, like the star-fish that
crawls upon it, allows its young seeds quite unformed to be
floated away by the tide.

All seeds, then, are parts of the living matter of the
parent ; some leave naked and without food ; others are
protected by shells or by husks which are filled with food ;
others live within the mother until they have ceased really
to be seeds, and are fully formed new creatures.

Now the living matter of any simple organism is so much
the same throughout the whole body that almost any part
of it will do to build the new generation from. Thus,
although the sea-anemone does sometimes set apart certain
cells as seeds, yet any part of the body will, if cut off, grow
into a complete creature. The same thing is true of a moss
plant. But the more highly organised animals have their
living matter set to such different service in their various
organs that most of it does not keep all the qualities of the
whole creature, but only of that part to which it belongs.
Thus if a starfish lose its arm, another will grow from the
stump. A snail can in this way repeatedly regrow its horns.
Even so highly developed an animal as a lizard can grow a
new tail. With ourselves this power is confined to growing
new skin if we lose part of it, or mending a bone if it be
broken, and other similar processes.

When we clearly understand in what way the offspring
of all creatures arise from their parents, how they are, as
Erasmus Darwin said long ago, like separated buds, then
we see the truth of the often-made comparison between any
or all species of animals and an organism. The individuals
of a species are not -indeed bound together by protoplasmic
strands, but their interdependence is not less complete. A
single species utterly destroyed might modify the life of the

chap, viii Vitality 141

whole earth. Life itself is dependent upon the invariable
presence of minute quantities of iron in the soil. A wan-
dering tribe of savages is an organism not quite so high in
the scale of social organisms as is the hydra in the scale
of individuals ; for the cells of the hydra, although divided
broadly into an outer and an inner layer, are yet more
divided in their functions than are the members of a
savage tribe. For there are only two kinds of person in
such a tribe — hunters and cooks ; while a highly civilised
community, with its immense variety of workmen, is prob-
ably not so well organised as any mammal ; for there are
in such a state thousands of persons, untrained to any special
labour, merely a burden to themselves and to the nation.

9. Origin of Life. — We have said that life probably
began when the conditions of heat and solubility of sub-
stance were more favourable to the formation of peculiar
and complex matter than at present. But such a state-
ment is often thought to be unphilosophical in view of the
fact that we have at present no experience of the formation
of such substances, and that it has been conclusively proved
that living creatures always proceed from pre-existing life.
But those who urge such objections forget that all that has
been proved is, that the simplest creatures known to be alive
at present can be formed only by cell -division one from
another, and not from simple chemical materials. But we
must remember that those simplest animals are highly
developed in comparison with the complex matter from
which we conceive life to have sprung ; and no one
would now expect that such comparatively highly developed
animals could arise from simple matter. There is certainly
no evidence of the formation at present of the very simplest
and original living matter. But, in the first place, could
we see it, even with a microscope, if it were to be formed ?
Might it not be formed molecule by molecule ? And,
secondly, what chance of survival would such elementary
creatures have among the voracious animals that swarm in
all places where such simplest creatures might possibly be
formed ? Instantly they would be devoured, before they
could grow large enough to be seen.

H2 The Study of Animal Life part ii

Lastly, let it be carefully observed, such a belief as this
as to the origin of life, and of the basis of all life in chemical
processes, carries with it no necessary adherence to the
doctrines of Materialism. The materialist analyses the
whole objective world of phenomena into matter and motion.
So far, his conclusion is perfectly legitimate ; but when he
maintains that matter and motion are the only realities of
the world, he is making an unwarrantable assumption.
Matter in motion is accompanied by consciousness in our-
selves. We infer a similar consciousness in creatures like
ourselves. As the movements and the matter differ from
those that occur within our body, so will the accompanying
consciousness. The simplest state of affairs or “ body ”
we can imagine is that of a gas such as hydrogen. But
such a simple state of matter may have its accompanying
consciousness, as different from ours as is the structure of
our bodies from that of a hydrogen molecule. This is, of
course, also an assumption, but it is one that harmonises
with the facts of experience.

The opposite extreme to Materialism is Idealism, and in
this school of philosophy an assumption precisely similar,
and exactly opposite to that of Materialism, is made. The
idealist says the objective world of phenomena has no exist-
ence at all, it is the creation of mind. An objection to
such a theory lies in the question, If matter and energy are
the creation of mind, how is it that we find them to be
indestructible ?

Popular philosophy has made an assumption which lies
midway between these extremes. It postulates two reali-
ties, matter and spirit, having little effect upon one another,
but acting harmoniously together.

But the view that is here set forth postulates neither
matter nor spirit, but an entity which is known objectively
as matter and energy, and subjectively as consciousness.
This philosophy goes by the name of Monism. The term
consciousness is used for lack of any other to express the
constant subjective reality. Carefully speaking, it is, of
course, only the more complex subjective processes that
form consciousness.

CHAPTER IX

THE DIVIDED LABOURS OF THE BODY

i. Division of Labour — 2. The Functions of the Body : Movement;
Nutrition ; Digestion; Absorption; The Work of the Liver
and the Kidneys; Respiration; Circulation; The Changes
within the Cells ; The Activities of the Nervous System —
3. Sketch of Psychology

1. Division of Labour, — The simplest animals are one-
celled ; the higher animals are built up of numberless cells.
All the processes of life go on within a single cell. In a
many-celled animal the labours of life are divided among
the various groups of cells which form tissues and organs.
The history of physiological development is the history of
this division of labour.

When a dividing cell, instead of separating into two
distinct masses, remained, after the division of its nucleus,
with the two daughter masses lying side by side, joined
together by strands of protoplasm, then the evolution of
organic form took a distinct step upwards, and at the same
time arose the possibility of greater activity, by means of
the division of labour. For when the process had resulted
in the formation of an organism of a few dozen cells,
arranged very likely in the form of a cup, the outer cells
might devote the greater part of their energies to movement
and the inner cells to the digestion of food. In the com-
mon Hydra the body consists of two layers of cells arranged
to form a tube, the mouth of which is encircled by tentacles.

144 The Study of Animal Life part h

The cells of the outer layer are protective, nervous, and
muscular ; the cells of the inner layer are digestive and
muscular. The cells of Hydra are therefore not so many-
sided in function as are Amoebae. In animals higher than
the simplest worms, a middle layer of cells is always formed
which discharges muscular, supporting, and other functions.

With advancing complexity of structure the specialisa-
tion of certain cells for the performance of certain functions
has become more pronounced. In the human body the
division of labour has reached a state of great perfection ;
we shall give a slight sketch of its arrangements.

2. The Functions of the Body. — Our objective life
consists of movement, and of feeding to supply the energy
for that - movement. Growth, reproduction, and decay are

elsewhere treated of.

Movement. — We move by the contraction of cells massed
into tissues called muscles. Contractility is a property of
all living matter ; in muscle-cells this function is predomi-
nant. This is all that need be said here of movement ; the
processes of nutrition we must follow more closely.

Nutrition. — All the cells of our bodies are nourished by
the stream of fluid food-stuff, the blood, which flows in a
number of vessels called arteries, veins, or capillaries,
according to their place in the system. From this stream
each cell picks out its food ; and into another stream —
the lymph stream — moving in separate channels — the
lymphatics, which, however, join the blood channels, each
cell casts its waste material ; just as a single-celled animal
takes food from the water in which it lives and casts its
waste into it.

Nutrition must therefore consist of two series of activi-
ties. One series will have for its object the preparation
of food-matter so that it may enter the blood, and the
excretion of waste products out of the blood. The other
series will consist of the activities of the individual cells, —
the manner in which they feed themselves.

The first step in the preparation of the blood is digestion.
Most food-stuff is solid and indiffusible ; before it can enter
the blood it must be made soluble and diffusible. The

chap, ix The Divided Labours of the Body 145

supply of oxygen to the tissues is also a part of these first
processes of nutrition. Being a gas, it is treated in a
special way which will be described immediately.

Digestion. — The various food-stuffs have various chemi-
cal qualities. After being swallowed they enter a long
tube, the digestive tract or alimentary canal. Within
this canal they are subjected to the action of various
digestive juices prepared by masses of cells called glands.
Saliva is one of these juices, gastric juice is another,
pancreatic juice is another. The effect of these juices
upon the food is that most of it is dissolved in the juice
and made diffusible. Thus we see an example of the
division of labour. An amoeba flows round a solid particle
of food and digests it. In the higher animals the cells of
the digestive glands are specialised for this particular func-
tion and do little else.

Absorption. — After the food is digested it leaves the
alimentary canal, and is absorbed into the blood-vessels
and lymphatics in the walls of the canal. Absorption is not
a mere process of diffusion. It is diffusion modified by the
cells lining the alimentary tract. Certain chemical changes
are effected at the same time. Most of the absorbed food
passes to the liver ; but the fat does not go directly into
the blood, being first absorbed into that other system of
vessels, the lymphatics. Eventually it also gets into the
blood ; for the two streams are connected.

The Work of the Liver and the Kidneys. — The cells
of the liver secrete a juice called bile, which is poured into
the alimentary canal. The exact function of this juice is
still doubtful. It has a certain use in the digestion of fats,
but it is largely an excretion. The stream of food -stuff
going to the liver contains sugar, the result of the digestion
of carbohydrates ; albumen, the result of the digestion and
absorption of proteids ; and certain waste nitrogenous
matters formed during the digestion of proteids.

The cells of the liver retain the sugar, store it within
themselves, in the same sort of way that a potato stores up
starch, and give it up gradually to the blood again. So
far as is known they do not affect the albumen in any way,

146 The Study of Animal Life part ii

but the waste nitrogenous matter is altered and then sent
on in the blood stream to the kidneys.

The cells of the kidneys take this stuff, which was pre-
pared in the liver, and other waste nitrogenous products
out of the blood, pass them and a certain amount of water
along to the urinary bladder, which empties itself from time
to time.

Respiration. — Breathing consists of two distinct acts,
inspiration and expiration. During an inspiration air is
drawn into lungs. Thence the oxygen passes by diffusion,
modified by the fact that the essential membrane is a living
one, into the blood. There it enters into a loose combina-
tion with haemoglobin, the red colouring matter of the
blood cells, and is thus carried to the cells of the tissues to
be absorbed into their living matter. During an expiration
we breathe out air which has less oxygen and more carbonic
acid gas than normal air. The carbonic acid is a waste-
product formed by the cells of the body ; it first enters the
blood, is then carried to the lungs, and leaves the blood-
vessels by a process of diffusion similar to that by which
the oxygen entered. The close association of these two
processes is simply due to the fact that an organ fitted for
the diffusion of one gas in one direction will do for the
diffusion of all gases in any direction.

Circulation. — The blood is maintained in a healthy state
by the processes we have described. By the active con-
traction of the heart it is pumped round and round the
body, continually carrying with it fresh food to the tissues,
and carrying away with it the waste matter cast out of the
tissues. All the blood-vessels, except the very smallest,
have muscular walls. The heart is a large hollow mass of
muscles, is a part of a pair of large blood-vessels that have
been bent upon themselves, and arranged so as to form
four separate chambers, two upper and two lower, an upper
and a lower opening directly into one another on each side.
By the contraction of the lower chamber of the left pair the
blood is forced through all the vessels of the body ; these
collect and empty the blood into the upper chamber of the
right pair ; from this it passes into the lower chamber on

CHAP. IX

The Divided Labours of the Body 147

the same side, and from this it is forced through the vessels
of the lungs, returning to the upper chamber of the left
side, and so to the lower chamber of the left side.

The way in which the blood is able to nourish the
tissues is as follows : — The outgoing vessels — arteries — enter
each mass of tissue ; within it they break up into number-
less very small, very thin-walled vessels — capillaries ; the
blood oozes through these into the small spaces — lymph
spaces — that occur throughout the tissues ; adjacent to these
spaces are the cells, which take from the lymph — the fluid
that fills the small spaces and the vessels connected with
them — what they need, and cast into it their waste. The
lymph spaces open into lymph vessels, which, as has been
noted, join the blood-vessels. Oxygen and carbonic acid,
being gases, pass directly from the blood through the walls
of the vessels to the tissues, and from the tissues to the
blood.

The Changes within the Cells. — In speaking of proto-
plasm an outline of the kind of knowledge that we possess
of the chemical changes that take place within the cells
has been given. We know little more than the sub-
stances that enter the cells and the substances that leave
them.

Perhaps even this is too much to say ; more exactly, we
know the substances that enter the body by the mouth and
nose, and through the alimentary canal and lungs ; we
know the substances that leave the body through the
kidneys, and, in expiration, through the nose. A large
amount of water and traces of other matters leave the body
as perspiration ; but the chief use of sweating is probably
the regulation of the temperature of the body, and the skin
should not be thought of as an excreting organ in the same
way that the kidneys are. The undigested matter that
passes from the food-canal has never been within the
blood, and does not therefore concern us in this inquiry.

But we know very little more than this ; the analysis of
the precise changes that any particular mass of tissue exerts
upon the blood — i.e. the differences that must exist between
the substances entering it and the substances leaving it — is

148

PART II

The Study of Animal Life

very difficult of determination, because of the immense
quantity of blood that passes through any tissue in a short
time. This concludes our sketch of the interchange of
matter within the body.

The Activities of the Nervous System. — We have now
to consider the arrangement of the nervous system — first
merely as the means by which all the varied activities of
the tissues of the separate parts of the body are co-ordi-
nated and wrought into an harmonious series of actions,
and then as the associate of consciousness and of mental
processes.

Just as protoplasm may be called the physical basis of
life, so is nervous tissue far excellence the physical basis of
consciousness and of mind. Throughout the whole animal
kingdom it has a superficial similarity of structure, and
consists of the same three parts.

(1) First there are cells adapted to receive notice of

change in the outer world. Changes in the sur-
rounding medium and affecting such cells are
called stimuli. These cells sensitive to stimuli
form the chief part of the sense organs — the
eyes, ears, nose, tongue. Also in the skin
there are cells sensitive to alterations of touch
and temperature. The effect of stimuli upon
such cells is probably to set them into a state of
molecular agitation, which may or may not result
in chemical changes.

(2) There are connecting fibres or nerves, which,

being connected with the sensory cells, take up
the vibrations or possibly the chemical changes
of the sensory cells and transmit them to the
“ centre.”

(3) There are “ central ” cells, in which the nerves
end, and which are set in molecular agitation by
the vibrations of the nerves. This molecular
agitation is often, when the central cells are in
the brain, accompanied by consciousness. Ap-
parently also agitations may arise “ spontane-
ously” within these central cells and stimulate

chap, ix The Divided Labours of the Body 149

the outgoing nerves, and cause muscular move-
ments, or the activity of glands, or other cellular
activities.

In many ways analogous to the nervous system is
the telegraph system of a country ; the receiving stations
are the nerve cells, among which are the cells of the sense
organs ; the connecting wires are the nerve fibres ; the
central stations are the groups of cells called ganglia, the
chief of which are in the brain and spinal cord. The less
important ganglia are like the branch offices, they receive
messages and transmit them unaltered ; the higher ganglia
are like the offices of a government, in which messages are
received, plans elaborated on the strength of the news, and
orders sent out to various parts of the country. All such
actions when they take place in the nervous system are
called reflex actions, whether a received message be sent
on unaltered, or whether the receiving cell regulates the
transmission according to the needs of the parts of the
body. The analogy of telegraph stations, even with the
living clerk to work them and with responsible persons to
direct the clerk, does not give a much too complex idea of
the activities of nerve cells.

3. Sketch of Psychology. — The following is largely
derived from Professor Lloyd Morgan’s Animal Life and
Intelligence , to which we refer the reader, and to which we
acknowledge our indebtedness.

It very often happens that changes in nervous matter,
caused by changes in the outer world, result in what we
call a change of consciousness.

Consciousness is the subjective side of molecular dis-
turbance in brain or other nerve matter.

Changes in the outer world which cause disturbance of
nerve matter are called stimuli.

Changes of consciousness produced by stimuli are called
impressions.

If impressions left no permanent trace in conscious-
ness behind them, there would be no such thing as mind,
f or mind is based upon memory, and memory is the re-
vival of past impressions, which, we must suppose, have in

i5°

I'ART II

The Study of Animal Life

some way been stored within the cells of the brain in the
form, from the objective point of view, of a certain
arrangement of its particles.

When, after the revival of past impressions, we are able
to discriminate between them, we call them sensations.

Now sensations are referred, in consciousness, not to

Fig. 31. — Attitude of a hen protecting her brood against a dog
(From Darwin’s Expression of Emotions.')

the brain cells which discriminate between them, but to the
cells of the sense organs which received them.

Further, we refer, by experience, the causes of sen-
sations to the outer world. We do this by a mental pro-
cess which is called perception.

Now out of perceptions, and through associations, there
arise expectations. The mental process involved in the
formation of an expectation is called inference.

chap, ix The Divided Labours of the Body 151

Inference is of two kinds :

(1) Perceptual, drawn from direct experience, as in

the inference as to a rain storm from a black
cloud.

(2) Conceptual, which, though based upon experience,

yet can predict events that have never been
experienced. For instance, one who had studied
in books only the causes of volcanic activity,
might predict with a certain amount of confidence
a flow of lava from a volcano, when he saw it in
that state of activity which he knew usually pre-
ceded an eruption of lava.

What we call the emotions, love, hate, fear, and others,
are, so far as we can tell, agitations of nervous matter
which affect consciousness. Their exciting stimuli — infer-
ences for example — proceed, immediately, from within the
brain, ultimately, from changes in the outer world.

We have, therefore, the following orders of conscious-
ness, which are easily distinguishable in theory :

(1) Impressions, or the effects of environmental
changes upon nervous matter ; the retaining and
revival of these constitutes the basis of memory.

(2) Sensations, which occur when the differences that
exist between impressions are discriminated.

(3) Perceptions, which are the outward projections
into the world, by mental acts, of the molecular
disturbances caused in the brain by environ-
mental changes. For example, light falls upon
the retina, stimulates the optic nerve, and causes
a molecular disturbance in the brain, but the
consciousness excited in us is not of the brain
disturbance, but of the light.

It is most essential that the distinction between per-
ceptual and conceptual inference be clearly realised, as it is
probable that it is the faculty for the latter which more
than anything else separates man from the lower animals.
We may be nearly certain that many animals exercise per-
ceptual inference, and we may affirm with little doubt that
none has ever performed a conceptual one. It has been

152 The Study of Animal Life i*art ii

stated that a monkey that had learned to screw and
unscrew a handle from a broom had learned “ the principle
of the screw.” This is entirely erroneous. The monkey
merely observed that a certain movement given to the
handle caused it to separate from the broom, and inferred
perceptually that the same result would always follow from
the same action.

It is evident that a sound comparative psychology of
the animal kingdom, or even of a few of the highest
species, is beyond the present possibilities of science.

CHAPTER X

INSTINCT

i. General Usage of the Term — 2. Careful Usage of the Term —

3. Examples of Instinct — 4. The Origin of Instinct

In considering the mental life of animals, we must settle
how far it is comparable to that of man. We judge of the
mental processes of human beings, other than ourselves,
from their actions ; and we can only do the same when
dealing with animals. If we often err in inferring the
mental states of our fellow-men, how much more are we liable
to error when we are considering creatures different from
ourselves. Still, believing as we do in the continuity of
life, both objective and subjective, by careful proceeding it
is probable that in time we may arrive at a certain state
of precision and exactness in comparative psychology.

Since the idea that is formed of the world is gained
entirely from sensations, the world of every creature must
be largely constructed from its dominant sense ; in a dog,
for instance, from scent.

In common speech the actions of animals are all ascribed
to instinct. The notion which underlies the term is, that
while the actions of men are determined by reason, those of
animals are prompted by a blind power of doing that which
is fitted to the successful conduct of their lives. This, as
we shall see, is a notion that requires modification.

1 . General Usage of the term Instinct. — Every one has
a general notion of what is meant by instinct, but few are

i54 The Study of Animal Life part u

agreed as to the precise usage of the word ; thus when the
birds build their nests, or when the bees collect honey and
form their combs, their acts are with one accord said to be
instinctive ; but some would demur at using such a term to
describe the love of parents for their children, the courage
of brave men, or the artist’s perception of beauty. But,
even supposing we agree to mean by instinct all those actions
which are neither simply reflex nor purely rational, there
will still remain great difference of opinion as to its origin.
Thus the love of parents will not be imagined as due to
practice, either in the individual or its ancestors, but rather
to take origin in some hidden necessity of nature ; while
the rapid closure of the eyes as protection from an expected
blow would seem in all likelihood to have begun in a rapid
exercise of intelligence, which, by being often repeated,
had ceased to be accompanied by conscious effort.

It seems to us that there is still need of a vast amount
of observation and experiment before a theory of the origin
of instinct that will be at all satisfactory can be framed. As
already remarked, it is not easy to decide even in what
sense the term ought to be used. This being so, we shall
content ourselves with mapping the field of thought and
indicating the lines of inquiry that must be followed before
a just view of the subject will be possible.

If we arrange examples of all the movements of animals
in the order in which they are perfonned in the lifetime of
the individuals, not limiting ourselves to those acts which
involve the whole organism, but considering also those which
a single organ or mass of tissue may execute, we shall see
at a glance all the possible varieties of activity with which
we can be concerned. It is, of course, only the move-
ments of comparatively large masses of tissue with which
we can deal at present. The molecular movements which
lie at the base of all the visible ones are as yet almost
unknown.

Even before birth, visible movements of the parts of the
higher animals occur ; as, for instance, the beating of the
heart. Such movements may be either “ automatic ” or
reflex. At birth, in addition to such movements of its parts,

chap, x Instinct i55

the organism acts as a whole ; it reacts to its environment,
and in time performs “ voluntary ” actions.

The acts of the parts of an organism may be —

(1) “Automatic,” as, for example, the beating of the

heart.

(2) Reflex, as, for example, the intestinal movements
which force the food through the alimentary
canal, or the movements involved in sneezing.

(3) Mixed actions which are partly automatic and
partly reflex, such as the respiratory movements.

The movements of the entire organism may be of a very
complex nature. They may be —

( 1 ) Reflex ; as when we start at a sudden noise.

(2) “ Innate,” commonly called instinctive ; these are
best observed in newly-born animals, for in them
intelligence, which must be based upon experience,
is necessarily at a minimum.

(3) “ Habitual,” such as are rapidly learned and are
then performed without mental effort, which imply
an innate capacity, and are therefore allied to (2).

(4) Intelligent, such as imply mental activity, which
consists in the combining and rearranging all the
other possible acts of the order — (1), (2), or (3) ;
and which may be recognised in all adaptations
to novel circumstances.

This classification possesses most obvious faults, but it
has certain advantages. It reveals some of the difficulties
that delay the would-be definer of instinct. For the essen-
tial criterion of an instinctive action is that all the machinery
for its performance, as a reflex to a certain stimulus, lies
ready formed within the organism ; but the apparently in-
soluble questions present themselves, How soon may not
actions be modified by intelligence ? and How in a mature
animal with considerable experience is one to separate
the purely instinctive acts from the intelligently modified
instinctive acts ?

Also it is evident that “habitual” actions may be “instinct-
ive ” actions deferred until the creature be further devel-
oped, as the flight of many birds is deferred ; or they may

PART I

1 56 The Study of Animal Life

be actions in the formation of which intelligence has had a
considerable share.

Now all these activities of an entire organism maybe
studied from four points of view : —

(1) Of natural history, or general description, such as

occurs here and there throughout this work :

(2) Of physiology, or the analysis of the muscular,
nervous, and other mechanisms involved ; as
treated generally in the last chapter :

(3) Of psychology, or the investigation into the states
of consciousness and mental processes concerned ;
as sketched in the last chapter :

(4) Of aetiology, or study of the factors in their origin

and development.

We shall first define more carefully than we have yet
done what we shall speak of as instinct, then give a few
examples, and finally discuss the aetiology of it.

2. The Careful Usage of the term Instinct. — We have
enumerated all the possible varieties of action, and the pos-
sible states of consciousness with which they may be asso-
ciated have been described in the last chapter. If we retain
the use of the term instinct we must explain to what order
of activity we shall apply it. In our use of the term we
shall not strive after any great precision ; for, as already
noted, the difficulty of precision seems to us to be at present
insurmountable. In a general way we shall call any action
which does not require for its execution any immediate
exertion of perceptual inference an instinctive action. Thus
a burned child dreads the fire ; such dread and its conse-
quent avoidance of fires may, with propriety, be termed
instinctive. After the first burn the avoidance will, for a
short time, be the result of perceptual inference ; but in
perhaps a few days only the avoidance becomes “ instinct-
ive” ; or it might be called “ habitual,” as hinted previously.
It is, of course, to be understood that an “ instinctive ”
action is not necessarily the result of this “ lapsed intelli-
gence,” as it has been called. Thus, when a worm
wriggles away from a fire it probably has not at any time
reasoned out to itself the advantages of such procedure,

CHAP. X

Instinct

r57

yet it may well be said to avoid the fire instinctively. It is
obvious that, if we agree to use the term as defined, we
must call all the actions of the lower animals, whose con-
sciousness has never risen to the level of perceptual infer-
ence, instinctive. This definition is based upon the assump-
tion that we can determine the conscious states of animals ;
but, as we have repeatedly said, it is only within very wide
limits that we can with any certainty do this. The inten-
tion, however, is to preclude all those actions which are
certainly or probably rational, and at the same time include
adaptive reflex actions.

Mr. Herbert Spencer has defined instinct as compound
reflex action, while Mr. Romanes separates it from reflex
action and from reason as follows : —

“ Reflex action is non-mental neuro-muscular adjustment
due to the inherited mechanism of the nervous system,
which is found to respond to particular and often-recurring
stimuli, by giving rise to particular movements of an
adaptive though not of an intentional kind.”

“ Instinct is reflex action into which there is imported
the element of consciousness. The term is therefore a
generic one, comprising all those faculties of mind which
are concerned in consciousness and adaptive action,
antecedent to individual experience, without necessary
knowledge of the relation between means employed and
ends attained, but similarly performed under similar and
frequently-recurring circumstances by all the individuals of
the same species.”

“ Reason or intelligence is the faculty which is con-
cerned in the intentional adaptation of means to ends. It
therefore implies the conscious knowledge of the relation
between means employed and ends attained, and may be
exercised in adaptation to circumstances novel alike to the
experience of the individual and that of the species.”

Mr. Romanes therefore separates reflex action from
instinctive action by limiting the term instinct to those
actions which are, as a matter of fact, conscious reflexes.
His definition is open to objection on the same ground that
ours is, only in a greater degree ; for it is easier to deter-

PART J1

ts8 The Study of Animal Life

mine the presence of perceptual inference than the absence
of consciousness ; this criterion may be of theoretical
interest, ^it is of no practical use. The other attributes he
enumerates should be carefully studied.

Prof. Lloyd Morgan also separates, but by no hard-and-
fast line, the automatic and reflex actions, . which are
reactions to definite stimuli, from instinctive actions, which,
according to him, are “ sequences of co-ordinated activities,
performed by the individual in common with all the mem-
bers of the same more or less restricted group, in adaptation
to certain circumstances, oft recurring or essential to the
continuance of the species.”

He separates these from intelligent actions, which are
“performed in special adaptation to special circumstances.”

Instinctive activities he conceives to be performed
“ without learning or practice.” If the actions need a little
practice he calls them “ incomplete instincts” ; if a great deal
of practice be necessary they are called “ habitual activities” ;
if they are not perfectly developed at birth but after further
development can be performed without practice they may be
called “deferred instincts.” A further useful classification
of instincts is into “ perfect ” and “ imperfect,” according to
the precision of their adaptation to the desired end.

Mr. Lloyd Morgan’s definition, like the others, implies that
one can separate rational from non-rational actions ; but he
safeguards himself by defining instincts as “ oft-recurring or
essential to the continuance of the species,” in contra-
distinction to intelligent actions which are performed in
special adaptation to special circumstances. It is important
to notice that the terms of the definition are that instincts
are either oft-recurring or essential, and not oft-recurring
and essential, for many instincts are only either one or the
other and not both. But it is not always possible to say of
a certain action that it is a special adaptation to a special
circumstance, and is therefore rational, and not in reality
an instinctive adaptation to circumstances that are of frequent
occurrence although we have not observed them to be so.

This definition, however, emphasises the fact that instincts
are common to species ; it is, however, not easy to estimate

CHAP. X

Instinct

iS9

the exact significance of this fact, for the apparent similarity
in the actions of individuals of the same species must, to a
certain extent, be due to incompleteness of observation.

It is after considering all these definitions that we have
come to the conclusion that it is convenient to describe all
those actions of animals which are not immediately rational
err intelligent as instincts. If we classify an instinct as
reflex in cases where the exact chain of internal events is
known and use the other qualifications already enumerated,
we reach a simplicity and precision of speech that is
convenient.

At the same time all such criteria as adaptiveness and
similarity of performance in all the individuals of a species
can obviously be applied as they are discovered.

The essential distinction, we believe, between non-
intelligent, that is, instinctive, and intelligent actions, is
that non-intelligent actions are performed in virtue of the
innate and co-ordinated mechanisms of the organism,
whereas for an intelligent action the organism has to do a
greater or less amount of the co-ordination for itself.

3. Examples of Instinct. — If we classify all the actions
of animals according to the period of life at which they are
performed, we shall find that there are three distinct classes
of action which may with convenience be considered
separately.

They are —

(1) Those which are performed at birth, or shortly

afterwards, as perfectly, or nearly so, as at any
future time ;

(2) Those more varied actions which are characteristic

of the mature life of any animal :

(3) Those which are associated with reproduction.

The first of these classes must evidently consist of very

pure instincts, since the creature cannot be supposed to
reason before it has any store of experience.

The second class is well typified by the marvellous
actions of insects, such as ants, bees, and wasps. These
may be instinctive, but it is very probable that many of
them are, at least, improved by intelligence.

PART II

160 The Study of Animal Life

{a) They may be perfected by perceptual inferences on
the part of the individuals, and the mental efforts may or
may not, after a certain number of repetitions, be replaced
by reflexes.

(i b ) They may be perfected by less complex mental
efforts, such as those involved in imitation or in receiving
instruction from other members of the species.

Actions of the third class may be as purely instinctive
as any of those in the first class, or may be improved by
intelligence like those of the second class ; but among
them are many of the most wonderful performances of
animals, for they often seem to show a prevision of an
unknown future.

Some interesting experiments have been made upon
instincts of the first class. The observations show that the
precision of the neuro- muscular co-ordinations of some
newly-born creatures is very surprising. Mr. Spalding
blindfolded some chickens immediately after they were
hatched, and removed the hood after two or three days
when they were stronger. He says that “ almost invariably
they seemed a little stunned by the light, remained motion-
less for several minutes, and continued for some time less
active than before they were unhooded. Their behaviour,
however, was in every case conclusive against the theory
that the perceptions of distance and direction by the eye
are the result of experience, or of associations formed in the
history of each individual life.”

“ Often at the end of two minutes they followed with
their eyes the movements of crawling insects, turning their
heads with all the precision of an old fowl. In from two to
fifteen minutes they pecked at some speck or insect, show-
ing not merely an instinctive perception of distance, but an
original ability to judge, to measure distance, with some-
thing like infallible accuracy. They did not attempt to
seize things beyond their reach, as babies are said to grasp
at the moon , and they may be said to have invariably hit
the objects at which they struck, they never missed by a
hair’s-breadth, and that too when the specks at which they
aimed were no bigger and less visible than the smallest dot

CHAP. X

Instinct

1 6 1

of an i. To seize between the points of the mandibles at
the very instant of striking, seemed a more difficult opera-
tion. I have seen a chicken seize and swallow an insect at
the first attempt ; most frequently, however, they struck
five or six times, lifting once or twice before they succeeded
in swallowing their first food.” Again, “ The art of scrap-
ing in search of food, which, if anything, might be acquired
by imitation, for a hen with chickens spends the half of her
time in scratching for them, is nevertheless another indis-
putable case of instinct. Without any opportunities of
imitation, when kept quite isolated from their kind, chickens
began to scrape when from two to six days old. Generally
the condition of the ground was suggestive ; but I have
several times seen the first attempt, which consists of a sort
of nervous dance, made on a smooth table.” Another
experimenter “ hatched out some chickens on a carpet,
where he kept them for several days. They showed no
inclination to scrape, because the stimulus supplied by the
carpet to the soles of their feet was of too novel a character
to call into action the hereditary instinct ; but when a little
gravel was sprinkled on the carpet, and so the appropriate
or customary stimulus supplied, the chickens immediately
began their scraping movements.”

Another instance of the first class of instincts is the fear
said to be shown by many animals for their natural foes ;
but on this point we find a certain conflict of evidence.
Thus kittens are said to show disgust at a dog, and, while
still blind, at a hand that has touched and smells of a dog, or
to tremble with excitement at the smell of a mouse. A chicken
or young turkey will show evident signs of fear at hearing
the cry of a hawk. Ants of various species that are mutually
hostile recognise an enemy, and fight ; but, on the other
hand, there are observations to the effect that, if taken young
enough, ants of several such species may be brought up
together as a happy family.

The instinctive tameness or wildness of many animals
towards man is probably the effect of intelligence and infor-
mation given to one another ; as is the avoidance of the
same kind of trap, after a short experience of its properties, by

M

162 The Study of Animal Life part n

all the mice of a house or birds of a district. The wild rabbit
is extremely timid, but the domesticated variety is as tame
as possible. In explanation of such cases we might easily
invoke the aid of “ the principle of cessation of natural selec-
tion ” when the safety of the species ceased to depend upon
wildness, but we prefer to suppose that the direct action
of intelligence is to a great extent operative.

As already noted, what are perhaps the most striking
examples of instinct of the second class occur among in-
sects. The comb-building of bees, the wars, the slave-using,
the agricultural pursuits of ants, have been so often de-
scribed that they need not detain us here. The brain of an
ant was to Darwin the most wonderful piece of matter in
the world. Wonderful, indeed, it would be if we supposed
that all the acts of an ant were truly instinctive, that is,
that the nervous machinery of co-ordination was ready,
waiting only the appropriate stimulus to evoke any one of
that series of nicely-adjusted actions. But if we suppose
that individual intelligence has a considerable share in that
co-ordination, then the brain of an ant, though still very
wonderful, is not to us quite so astounding an arrangement
of particles as it was to Darwin.

The third class of instincts, those connected with
reproduction, comprise such actions as the building of
homes and nests, the storage of food for the use of
young that may never be seen, and the care of young after
birth.

The nest-building of birds would form a very good sub-
ject upon which to experiment, in order to determine how
far such a complex act may be truly instinctive, and how
far it is perfected by training, by imitation, and by intelli-
gent practice and observation. The method would be to
isolate young birds from their parents and from all other
creatures of their kind, so as to preclude training and
imitation, and then see how far the nests . that they
built resembled the typical nest of their species. Then one
might remove other birds from their parents but allow them
the society of the members of an allied species, but one
whose nests differed to some observable extent from those

chap, x Instinct 163

of the species under experiment. So far as we know, no
adequate experiments have been carried out.

It is stated that the nests of British birds let loose in
Australia differ very greatly from the nests that they would
build at home. Now this may be due to the absence of
training and the possibilities of imitating the specific nest,
or it may be due to the absence of the materials with which
to build the characteristic nest.

When we consider the careful provision that the Sphex
wasp makes for its young, young which she will never see ;
or the selection by a butterfly of the leaf upon which she
lays her eggs, the only sort of leaf, it may be, that will serve
the grubs, when hatched, for food, food of a kind which the
butterfly herself does not eat, we have before us examples
of instincts most wonderful in their perfection and most
obscure in their origin. The ideas involved are too com-
plex for us to believe that the actions can be the result of
intelligence. So far as we can see at present, such
instincts can only be accounted for by the Natural Selection
of fortunate varieties of habit. The care of young and the
habit of incubation are instincts upon which a certain
amount of thought has been bestowed. For ourselves, we
incline to the idea which may seem mystical to some, that
such habits are born of an inevitable affection for what is so
nearly related to the very body of the parents. To escape
an explanation of such habits in terms of affection, certain
naturalists have suggested the demonstrably absurd notion
that birds sit upon their eggs in order to cool a fevered
breast. If such were her object, the very worst place that
a bird could select as her seat would be a woolly hairy
nest containing eggs which, in virtue of internal chemical
changes, generate heat of themselves.

4- The Origin of Instinct. — The theory of the evolu-
tion of instinct has been worked at by Darwin, and since his
day by various other authors, notably Mr. Romanes, Mr.
A. R. Wallace, and Professor Eimer ; while Professor
Weismann’s doctrines have necessitated the revision of
certain plausible hypotheses.

Darwin, of course, supposed that Natural Selection

PART n

i64 The Study of Animal Life

was the means of the evolution of habit as much as of
form.

Mr.. Romanes, starting from this as a basis, has con-
structed a well-reasoned and lucid theory. He supposes that
while many instincts have been evolved by Natural Selection,
such instincts being called Primary, other habits become
instinctive through the “ lapse of intelligence.” Actions
performed at first with mental effort, becoming after suffi-
cient repetition so ingrained upon the nervous system that
a mechanism of neuro- muscular co-ordination has been
established, are referred to as Secondary Instincts. He
imagines also a third class of Mixed Instincts in which
there are primary instincts that have been altered and
improved by intelligent variations of habit, or secondary
instincts that have been modified by natural selection.

Obviously, therefore, he supposes that intelligence may
be a factor in the formation of any habit that may be under
consideration.

But this theory of instinct becomes impossible if we accept
Professor Weismann’s doctrine that acquired characters can
not be inherited (this doctrine will be discussed in a later
chapter). If this be true, the only possibilities are primary
instincts, and secondary instincts formed afresh during each
individual lifetime, and mixed instincts of the same nature.

The exact antithesis to Professor Weismann’s theory is
upheld by Professor Eimer, who believes that instincts have
been evolved chiefly by the perpetuation of what Mr.
Romanes calls secondary instincts. There is little evidence
that this is the case. The value of Eimer’s work really lies
in his insistence upon the intelligent action of animals as
apart from purely instinctive action.

Mr. Wallace has begun the analysis of the particular
forms which the intelligence of animals takes. He supposes
that imitation of parents and other members of the species
has a great influence upon the actions of individuals. He
has dwelt especially upon such cases as the song and nest-
building of birds.

It may be pointed out as a matter for consideration that,
granted that parents teach their offspring, as, for instance,

CHAP. X

Instinct

165

birds teach their fledglings to fly, and ants their young their
place in the community of the nest, and that animals imi-
tate each other, it is quite possible, and indeed probable,
that an instinct may be steadily improved throughout suc-

FiG. 32.— Young ducks catching moths. (From St. John's Wild Sports.)

cessive generations by the intelligence of the individuals of
a species, without any acquired character being inherited.

The possible factors in the evolution of instinct are
therefore —

(1) Natural Selection, which might develop innate
capacity ; this is certainly insufficient for the
development of form, and therefore, probably, also
of mind.

1 66

PART II

The Study of Animal Life

(2) Individual intelligence, which directly modifies the
actions of individuals, and is also used when, by
imitation and education, the habits of a species
are steadily improved.

(3) The “lapsing of intelligence,” forming “second-

ary,” and helping to form “ mixed ” instincts.

But the probable factors are the first two.

PART II r

THE FORMS OF ANIMAL LIFE

CHAPTER XI

THE ELEMENTS OF STRUCTURE

i. The Resemblances and Contrasts between Plants and Animals —
2. The Relation of the simplest Animals to those which are
more complex — 3. The Parts of the Animal Body: Organs,
Tissues, Cells

The study of form and structure (Morphology), and the
study of habit and function (Physiology), are both as essen-
tial to science as the realities are in life. It is with the
forms of animal life and their structure that we have now
to do, but it seems useful at the outset to compare plants
and animals.

1 . The Resemblances and Contrasts between Plants
and Animals. — Every one could point out some differences
between a tree and a horse, but many might be puzzled to
distinguish clearly between a sponge and a mushroom,
while all have to confess their inability to draw a firm line
between the simplest plants and the simplest animals. For
the tree of life is double like the letter V, with divergent
branches, the ends of which, represented, let us say, by
a daisy and a bird, are far apart, while the bases gradually
approach and unite in a common root.

• Plants and animals are alike, though not equally, alive.

1 68

PART III

The Study of Animal Life

Diverse as are the styles of animal and vegetable archi-
tecture, the materials are virtually the same, and the
individuals in both cases grow from equally simple
beginnings.

Even movement, the chief characteristic of animals,
occurs commonly, though in a less degree, among plants.
Young shoots move round in leisurely circles, twining
stems and tendrils bend and bow as they climb, leaves
rise and sink, flowers open and close with the growing
and waning light of day. Tendrils twine round the
lightest threads, the leaves of the sensitive plant respond
to a gentle touch, the tentacles of the sundew and
the hairs of the fly-trap compare well with the sensitive
structures of many animals. The stamens of not a few
flowers move when jostled by the legs of insects, and the
stigma of the musk closes on the pollen.

Plants and animals alike consist of cells or unit masses
of living matter. The structure of the cell and the apparent
structure of the living stuff is much the same in both. We
may liken plants and animals to two analogous manufac-
tories, both very complex ; we study the raw materials
which pass in, many of the stages and by-products of
manufacture, and the waste which is laid aside or thrown
out, but in neither case can we enter the secret room where
the mystery of the process is hidden.

In the pond we find the eggs of water-snails and water-
insects attached to the floating leaves of plants ; in the
ditches in spring we see in many places the abundant
spawn of frogs and toads ; we are familiar with the heavily
yolk-laden eggs of birds. Now, with a little care it is quite
easy to convince ourselves that an egg or ovum is to begin
with a simple mass of matter, in part, at least, alive, and that
by division after division the egg gives rise to a young animal.
We are also well aware that in most cases the egg-cell, for
cell it is, only begins to divide after it has been penetrated,
and in some subtle way stimulated, by a male unit or sperm.
The great facts of individual history or development then
are, the apparent simplicity in the beginning, the pre-
liminary condition that the egg-cell be united with a male

chap, xi The Elements of Structure 169

unit, and the mode of growth by repeated division of the
ovum and its daughter-cells. In those plants with which
we are most familiar, the facts seem different, for we watch
bean and oak growing from seeds which, instead of being
simple units, are very complex structures. But the seed is
not the beginning of a plant, it has already a long history
behind it, and when that history is traced back to the seed-
box and possible seeds of the parent plant, there it will be
seen that the beginning of the future herb or tree is a single
cell. This is the equivalent of the animal ovum, and, like
it, begins its course of repeated divisions after it has been
joined by a kernel or nucleus from the pollen grain.

Thus, to sum up, along three different paths we reach
the same conclusion, that there is a fundamental unity
between plants and animals. In the essential activities
of their life, in the stones and mortar of their structure,
and lastly, in the way in which each individual begins and
grows, there is a real unity.

Yet, after all, plants and animals are very different.
The two kinds of organisms may be ranked as two great
branches of one tree of life, yet the branches diverge
widely and bear different foliage. The facts of divergence
and diversity are as undeniable as the inseparable unity of
the basal trunk and the genuine sameness of life throughout
the whole tree. I have stated the chief contrasts between
plants and animals in a tabulated summary —

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CHAP. XI

The Elements of Structure 1 7 1

The net result of this contrast is that animals are more
active than plants. Life slumbers in the plant ; it wakes
and works in the animal. The changes associated with the
living matter of an animal are seemingly more intense and
rapid ; the ratio of disruptive, power-expending changes to
constructive power-accumulating changes is greater ; most
animals live more nearly up to their income than most
plants do. They live on richer food ; they take the pounds
which plants have accumulated in pence, and spend them.
Of course plants also expend energy, but for the most part
within their own bodies ; they neither toil nor spin. They
stoop to conquer the elements of the inorganic world, but
have comparatively little power of moving or feeling. They
are more conservative and miserly than the liberally spend-
thrift animals, and it is possible that some of the most
characteristic possessions of plants, e.g. cellulose, may be
chemical expressions of a marked preponderance of con-
structive and up-buikling vital processes. It is enough,
however, if we have to some extent realised the common-
places that plants and animals live the same sort of life,
but that the animals are on an average more active and
wide-awake than the plants.

2. The Relation of the Simplest Animals to those
which are more Complex. — From the pond-water catch in
a glass tube one of the small animals, suppose it be a tiny
water-flea or a minute “ worm ” ; how does it differ from one
of the simplest animals, such as an Infusorian ? It consists of
many units of living matter instead of only one. The con-
trast is like that between an egg and the bird which is
hatched from within it. The simplest animals are single
cells, all the others from sponge to man are many-celled.
The Protozoa are units ; all others — the Metazoa — are
composite aggregates of units, or cities of cells.

Compare the life of one of the Protozoa with that of
a worm, a frog, or a bird. Both are alive, both may be
seen moving, shrinking away from what is hurtful, drawing
near to what is useful, engulfing food, and getting rid of
refuse. Both are breathing, for carbonic acid will poison
them, and dearth of oxygen will kill them ; both grow and

I 72

I’ART HI

The Study of Animal Life

multiply. But in the single- celled Protozoon all the pro-
cesses of life occur within a unit mass of living matter. In
the many-celled Metazoon the various processes occur at
different parts of the body, are discharged by special sets of
cells, among which the labour of life has been divided. The
life of the Protozoon is like that of a one-roomed house
which is at once kitchen and work-room, nursery and coal-
cellar. The life of the Metazoon is like that of a mansion
where there are special rooms for diverse purposes.

In having no “ body ” the Protozoa are to some extent
relieved from the necessity of death. Within the compass
of a single cell they perform a crowd of functions, but tear
and wear are often made good again, the units have great
power of self-recuperation. They may, indeed, be crushed
to powder, and they lead no charmed life safe from the
appetite of higher forms. But these are violent deaths.
What Weismann and others have insisted on is that
the unicellular Protozoa, in natural conditions, need never
die a natural death, being in that sense immortal. It
is true that a Protozoon may multiply by dividing into two
or more parts, but only a sort of metaphysical individuality
is thus lost, and there is nothing left to bury. We would
not, however, give much prominence to a strange idea of
this kind. For the “immortality of the Protozoa” is little
more than a verbal quibble ; it amounts to saying that our
common idea of death, as a change which makes a living
body a corpse, is hardly applicable to the unit organisms.
I believe, moreover, that the idea has been exaggerated ;
for instance, the Protozoa in the open sea, in their natural
conditions, seem to die in large numbers.

The combination of all the vital activities within the
compass of a single-cell involves a very complex life within
the unit, — not more complex than the entire life of a many-
celled animal, but fuller than that of one of its component
cells. While a Protozoon is relatively simple in structure,
its life of crowded functions, such as moving, digesting,
breathing, is exceedingly complex. The simpler an organism
is in structure the more difficult will it be to study its separate
functions. Physiological or functional simplicity is in inverse

chap, xi The Elements of Structure 173

ratio to structural or morphological simplicity. Thus the
physiologist makes most progress when he seeks to under-
stand animals with many parts, for there he can find a large
number of units, all as it were working at one task. The
life of a Protozoon is more manifold and complex than that
of any unit from a higher animal, just as the daily life of
the savage — at once hunter, shepherd, warrior — is more
varied than ours.

Already it has been recognised that every many-celled
animal begins its life as a single cell, — as an egg-cell with
which a male element has united. Every Metazoon begins
its life as a Protozoon, no matter how large the animal,
for the whales arise from ova “no larger than fern-seed,”
no matter how lofty the result, for man himself has to begin
his life at the literal beginning. The fertilised egg- cell
divides and re-divides, its daughter- cells also divide, the
resultant units are arranged in layers, clubbed together to
form tissues, compacted to form young organs, and the
result is such a multicellular body as we possess ; but while
this body-making proceeds, certain units are kept apart, in
some way insulated from the process of growth, to form the
future reproductive elements, which, freed from the adult
body, will begin a new generation. Back to the beginning
again every Metazoon has to go, and if we believe that the
Protozoa are not only the simplest, but also represent, the first
animals, we have here the first and perhaps most important
illustration of the fact that in its development the individual
more or less recapitulates the history of the race. The
simplest animals are directly comparable with the repro-
ductive cells of higher animals, but the divided cells of the
ovum remain clubbed together to form a young animal, while
the daughter-cells of a Protozoon separate from one another,
each as a new life.

The gulf between the single -celled and many-celled
animals is a deep one, but it has been bridged. Otherwise
we should not exist. Traces of the bridge now remain in
what are called “ colonial Protozoa,” which, however trouble-
some to those who like crisp distinctions, are most instruc-
tive to those who would appreciate the continuity of the

174 The Study of Animal Life part hi

tree of life. These exceptional Protozoa are loose colonies
of cells, descendants or daughter- cells of a parent unit,
which have remained persistently associated instead of
going free with the usual individualism of Protozoa. They
illustrate to some minds a primitive co-operation of cells ;
they show us how the Metazoa or multicellular animals may
have arisen.

3. The Parts of the Animal Body. — The physiologist
investigates life or activity at different levels, passing from
his study of the animal as a unity with habits and a tem-
perament, to consider it as an engine of organs, a web of
tissues, a city of cells, or finally as a whirlpool of living
matter. So the morphologist investigates the form of the
intact animal, then in succession its organs, their component
tissues, the minuter elements or cells, and finally the struc-
ture of the living stuff itself. Moreover, as there is no real
difference between studying a corpse and a fossil, the palae-
ontologist is also among the students of morphology ; and
most of embryology consists of studies of structure at dif-
ferent stages in the animal’s life-history.

The outer form of normal animals seems to be always
artistically harmonious. It has a certain hardly definable
crystalline perfection which pleases our eyes, but those who
have not already perceived this will not see much meaning
in the assertion, nor in Samuel Butler’s opinion that “ form
is mind made manifest in flesh through action.”

“ I believe a leaf of grass is no less than the journey-work of the
stars,

And the pismire is equally perfect, and the grain of sand, and
the egg of the wren,

And the tree-toad is a chef-d’oeuvre for the highest,

And the running blackberry would adorn the parlours of heaven,
And the narrowest hinge in my hand puts to scorn all machinery,
And the cow crunching with depressed head surpasses any statue,
And a mouse is miracle enough to stagger sextillions of infidels ! ”

Walt Whitman.

It is also important to think of the different kinds of
symmetry, how for instance the radiating sea-anemones and
jellyfishes, which are the same all round, differ markedly

CHAP. XI

175

The Elements of Structure

from bilaterally symmetrical worms, lobsters, fishes, ancl
most other animals. Then there is the difference between
unsegmented animals which are all one piece (like the
lower worms and the molluscs), and those whose bodies
consist, as in earthworm and crayfish, of a series of more or
less similar rings or segments, due to conditions of growth
of which we know almost nothing.

Organs are well-defined parts, such as limb or liver, heart
or brain, in which there is a predominance of one or a few
kinds of vital activity. Gradually, alike in the individual
and in the race, do they take form and function. There is
contractility before there are definite contractile organs or
muscles ; there is diffuse sensitiveness before there are
defined nerves or sense-organs. The progress of structure,
alike in the individual and in the race, is from simplicity
to complexity, as the progress of function is from homo-
geneous diffuseness to heterogeneous specialisation. The
two great kinds of progress may be illustrated by contrasting
a sea- anemone and a bird. The higher animal has more
numerous parts or organs, the division of labour within its
body has brought about more differentiation of structure,
but it is also a more perfect unity, its parts are more
thoroughly knit together and harmonised. There is pro-
gress in integration as well as in differentiation.

“ The shoulder-girdle of the skate,” W. K. Parker says, “ may be
compared to a clay mo'del in its first stages, or to the heavy oaken
furniture of our forefathers that stood ponderous and fixed by its own
massy weight. As we ascend the vertebrate scale, the mass becomes
more elegant, more subdivided, and more metamorphosed, until,
in the bird class and among mammals, these parts form the frame-
work of limbs than which nothing can be imagined more agile or
more apt. So also as regards the sternum ; at first a mere outcrop
of the feebly developed costal arches in the amphibia, it becomes
the keystone of perfect arches in the true reptiles, then the fulcrum
of exquisitely constructed organs of flight in the bird ; and lastly,
forms the mobile front wall of the heaving chest of the highest
vertebrate.”

Of the order in which organs appear or have appeared
we can say little. The simplest sponges and polypes are

i76

PART III

The Study of Animal Life

little more than two-layered cups of cells, the cavity of the
cup being the primitive food-canal. A parallel stage
occurs in the early life-history of most animals, when the
embryo has the form of a two-layered sac of cells, or is in
technical language a gastrula. Both in the racial and
individual life-history the formation of this primitive food-
canal occurs very early. But it is not certain that it — the
primitive stomach — was not at a still earlier stage an in-
ternal brood-cavity !

But instead of speculating about this, let us seek to
understand what is meant by the correlation of organs.
Certain parts of the body stand or fall together, they are
physiologically knit, they have been evolved in company.
Thus heart and lungs, muscles and nerves, are closely
correlated. Sometimes it is obvious why two or three
structures should be thus connected, for it is of the very
essence of an organism that its parts are members one of
another. In other cases the reason of the connection is
obscure.

When organs either in the same or in different animals
have a similar origin, and are built up on the same funda-
mental plan, they are called homologous. Those whose
resemblance is merely that they have similar functions are
termed analogous. Even Aristotle recognised that some
structures apparently different were fundamentally the
same, and no small part of the progress of morphology has
consisted in the recognition of homologies. Thus it was a
great step when Goethe and others showed that the sepals,
petals, stamens, and carpels of a flower were really modified
leaves, or when Savigny discerned that the three pairs of
jaws beside an insect’s mouth were really modified legs.
To Owen the precision of our conceptions in regard to
homologies is in great part due, though subsequent studies
in development have added welcome corroboration to many
of the comparisons which formerly were based solely on the
results of anatomy. Thus an organ derived from the outer
embryonic layer cannot be homologous with one derived
from the innermost stratum of embryonic cells. Homo-
logous organs in one animal are well illustrated by the

CHAP. XI

The Elements of Structure

177

nineteen pairs of appendages borne by a crayfish or lobster.
These differ greatly in form and in function ; many of them
are not analogous with their neighbours, one feels and
another bites, one seizes and another swims, but they are
all homologous. So are the different forms of fore-limb,
the pectoral fin of a fish, the fore-leg of a frog or lizard, the
wing of a bird, the flipper of a whale, the fore-leg of a tiger,
the arm of man. But the wing of an insect is merely
analogous not homologous with that of a bird, while the
wings of bats and birds are both analogous and homo-
logous.

KlG. 33. — Bones of the wing in pigeon (A), bat (B), extinct pterodactyl (C).

(From Chambers’s Encyclof.)

Change of Fimctioti. — Organs are not mechanisms rigidly
adapted for only one purpose. In most cases they have a
main function and several subsidiary functions, and changes
may take place in organs by the occasional predominance
of a subsidiary function over the original primary one.
Thus the swim- or air-bladder which grows out dorsally
from the food-canal of most fishes, seems usually to be a
hydrostatic organ ; in a few cases it helps slightly in
respiration, but in the double -breathing mud -fishes or
Dipnoi it has become a genuine lung. An unimportant
(allantoic) bladder at the hind end of the gut in frogs, is
represented in the embryos of reptiles and birds by a very
important respiratory (and sometimes yolk-absorbing) birth-

I

178 The Study of Animal Life i-art m

robe, and in almost all mammals by part of the placenta
which unites mother and unborn offspring.

Substitution of Organs. — To the embryologist Kleinen-
berg we owe a suggestive conception of organic change,
which he speaks of as the development of organs by sub-
stitution : An organ may supply the stimulus and the
necessary condition for another which gradually supersedes
and replaces it. In the simplest backboned animals, such
as the lancelet, there is a supporting gristly rod along the
back ■ among fishes the same rod or notochord is largely
replaced by a backbone ; in yet higher Vertebrates the
adults have almost no notochord, its replacement by the
backbone is almost complete. So in the individual life-
history, all vertebrate embryos have a notochord to begin
with ; in the lancelet and some others this is retained
throughout life, in higher forms it is temporary and serves
as a scaffolding around which, from a thoroughly distinct
embryological origin, the backbone develops. What is the
relation between these two structures — notochord and
backbone ? According to Kleinenberg, the notochord
supplies the necessary stimulus or condition for the
development of the backbone which replaces it.

Rudimentary 0?-gans. — ( a ) Through some ingrained
defect it sometimes happens that an organ does not
develop perfectly. The heart, the brain, the eye may be
spoilt in the making. Such cases are illustrations of
arrested development. ( b ) A parasitic crustacean, such as
the Sacculina which shelters beneath the tail of a crab,
begins life with many equipments such as legs, food-canal,
eye, and brain, which are afterwards entirely or nearly
lost ; the sedentary adult sea-squirt or ascidian has lost the
tail, the notochord, the spinal cord which its free-swimming
tadpole-like larva possessed. Such cases are illustrations
of degeneration. In these instances the retrogression is
demonstrable in each lifetime, in other cases we have to
compare the animal with its ancestral ideal. Thus there
are many cave- animals whose eyes are always blind and
abortive. The little kiwi of New Zealand has only apologies
for wings. We need have no hesitation in calling these

chap, xi The Elements of Structure 179

animals degenerate in eyes and fore-limbs respectively.
(c) But somewhat different are such structures as the
following : The embryonic gill-clefts of reptiles, birds, and
mammals, which have no respiratory significaftce, or the
embryonic teeth of whalebone whales, of some parrots and
turtles, which in no case come to anything. They are
vestigial structures, which are partly explained on the
assumption, justified also in other ways, that the ancestors
of reptiles, birds, and mammals used the gill-clefts as fishes
and tadpoles do, that the ancestors of whalebone whales,
birds, and turtles had functional teeth. No one can say
with certainty of vestigial structures that they are entirely
useless, nor can one precisely say why they persist after
their original usefulness has ceased. They remain because
of necessities of growth of which we are ignorant, and
they may be useful in relation to other structures though
in themselves functionless.

Classification of Organs. — We may arrange organs
according to their work, some, such as limbs and weapons,
being busied with the external relations of the organism ;
others, such as heart and liver, being concerned with
internal affairs. Or we may classify them according to
their development from the outer, middle, or inner layer of
the embryo. Thus brain and sense-organs are always mainly
due to the outer stratum (ectoderm or epiblast), muscles
and skeleton arise from the middle mesoderm or mesoblast,
the gut and its outgrowths such as lungs and liver primarily
originate from the inner endoderm or hypoblast. Or we
may arrange the various structures more or less arbitrarily
for convenience of description as follows : the skin and its
outgrowths, appendages, skeleton, muscular system, nervous
system, sense-organs, the food-canal and its outgrowths,
the body-cavity, the heart and blood-vessels, the respiratory
organs, the excretory system, the reproductive organs.

Tissues. — To the school of Cuvier we owe the analysis
of the animal organism into its component organs ; but as
early as 1801 BicMt published his Anatojnie Ginirale, in
which the analysis was carried a step farther. He reduced
the organs to their component tissues, and maintained that

PART Hi

1 So The Study of Animal Life

the function of an organ might be expressed in terms of the
properties of its tissues.

If we pass to the next step of analysis, and think of the
body as a' complex city of cells, we are better able to
understand what tissues are. Each cell corresponds to a
house, a tissue corresponds to a street of similar houses.
In a city like Leipzig many streets are homogeneous, formed
by houses or shops in which the predominant activity is the
same throughout. A street is devoted to the making of
clothes, or of bread, or of books. So in the animal body
aggregates of contractile cells form muscular tissue, of
supporting cells skeletal tissue, of secreting cells glandular
tissue, and so on.

It is enough to state the general idea that a tissue is an
aggregate of more or less similar cells, and to note that the
different kinds may be grouped as follows : —

I. Nervous tissue, consisting of cells which receive,
transmit, or originate nerve-stimuli.

II. Muscular tissue, consisting of contractile cells.

III. Epithelial tissue, consisting of lining and covering

cells, which often become glandular, exuding the
products of their activity as secretions.

IV. Connective tissue, including cells which bind,

support, and store.

Cells. — To the discovery and perfecting of the micro-
scope we owe the analysis of the body into its unit masses
of living matter or cells. From 1838-39, when Schwann
and Schleiden stated in their “cell doctrine” that all
organisms — plants and animals alike — were built up of
cells, cellular biology may be said to date. It was soon
shown as a corollary that every organism which reproduced
in the ordinary fashion arose from a single egg- cell or
ovum which had been fertilised by union with a male-cell
or spermatozoon. Moreover, the position of the simplest
animals and plants was more clearly appreciated ; they are
single cells, the higher organisms are multicellular.

Now the cells of the animal body are necessarily varied,
for the existence of a body involves division of labour

CHAP. XI

The Elements of Structure 1S1

among the units. Some, such as the lashed cells lining
the windpipe, are very active, like the Infusorian Protozoa;
others, for instance the fat-cells and gristle-cells of connective
tissue, are very passive, something like the Gregarines ;
others, such as the white blood corpuscles or leucocytes,
are between these extremes, and resemble the amoeboid
Protozoa.

But it is true of most of them that they consist ( i ) of a

I n;. 34. — Animal cell, showing the coiled chromatin threads of the nucleus (a),
and the protoplasmic network (l>) round about. (From Evolution of Sex ;
after Camoy.)

complex, and in part living cell -substance, in which keen
eyes looking through good microscopes detect an intricate
network, or sometimes the appearance of a fine foam ; (2)
of a central kernel or nucleus, which plays an important
but hardly definable part in the life of the cell, especially
during the process of cell-division ; (3) of a slight outer
membrane, varying much in definiteness and sometimes
quite absent, through which communications with neigh-

182 The Study of Animal Life i>Art hi

bouring cells are often established ; and (4) of cell contents,
which can be chemically analysed, and which are products
of the vital activity rather than parts of the living substance,
such as pigment, fat, and glycogen or animal starch.

The growth of all multicellular animals depends upon a
multiplication of the component cells. Like organisms,
cells have definite limits of growth which they rarely exceed ;
giants among the units are rare. When the limit of
growth is reached the cell divides.

The necessity for this division has been partly explained
by Spencer and Leuckart. If you take a round lump of
dough, weighing an ounce, another of two ounces, a third
of four ounces, you obviously have three masses success-
ively doubled, but in doubling the mass you have not
doubled the surface. The mass increases as the cube, the
surface only as the square of the radius. Suppose these
lumps alive, the second has twice as much living matter as
the first, but not twice the surface. Yet it is through the
surface that the living matter is fed, aerated, and purified.
The unit will therefore get into physiological difficulties as
it grows bigger, because its increase of surface does not
keep pace with its increase of mass. Its waste tends to
exceed its repair, its expenditure gains on its income.
What are the alternatives ? It may go on growing and die
(but this is not likely), it may cease growing at the fit
limit, it may greatly increase its surface by outflowing
processes (which thus may be regarded as life-saving), or
it may divide. The last is the usual course. When the
unit has grown as large as it can conveniently grow, it
divides ; in other words, it reproduces at the limit of
growth, when processes of waste are gaining on those
of construction. By dividing, the mass is lessened, the
surface increased, the life continued.

But although we thus get a general rationale of cell-
division, we are not much nearer a conception of the
internal forces which operate when a cell divides ; for in
most cases the process is orderly and complex, and is
somehow governed by the behaviour of the nucleus. Few
results of the modern study of minute structure are more

chap, xr

The Elements of Structure 183

marvellous than those which relate to dividing cells. From
Protozoa to man, and also in plants, the process is strik-
ingly uniform. The nucleus of the cell becomes more
active, the coil or network of threads which it contains is
undone and takes the new and more regular form of a
spindle or barrel. The division is most thorough, each of
the two daughter- cells getting an accurate half of the
original nucleus. Recent investigators, moreover, assert
that from certain centres in the cell-substance an influence
is exerted on the nuclear threads, and they talk of an archo-
plasm within the protoplasm, and of marked individuality of
behaviour in the nuclear threads. *

From the cell as a unit element we penetrate to the
protoplasm which makes it what it is. Within this we
discern an intricate network, within this, special centres of
force — “attractive spheres” and “central corpuscles,” or
an “ archoplasm ” within the protoplasm ! We study the
nucleus, first as a simple unit which divides, years after-
wards as composed of a network or coil of nuclear threads
which seem ever to become more and more marvellous,
“behaving like little organisms.” We split these up
into “ microsomata,” and so on, and so on. But we do
not catch the life of the cell, we cannot locate it, we cannot
give an account of the mechanics of cell-division. It is a
mystery of life. After all our analysis we have to confess
that the cell, or the protoplasm, or the archoplasm, or the
chromatin threads of the nucleus, or the “ microsomata ”
which compose them, baffle our analysis ; they behave as
they do because they are alive. Were we omniscient
chemists, such as Laplace imagined in one of his specula-
tions, and knew the secret of protoplasm, how its touch
upon the simpler states of matter is powerful to give them
life, we should but have completed a small part of those
labours that even now lie waiting us ; what further investi-
gations will present themselves we cannot tell.

CHAPTER XII

THE LIFE-HISTORY OF ANIMALS

♦

i. Modes of Reproduction — 2. Divergent Modes of Reproduction—
3. Historical — 4. The Egg- Cell or Ovum — 5. The Male-
Cell or Spermatozoon — 6. Maturation of the Ovum — 7.
Fertilisation — 8. Segmentation and the first stages in
Development — 9. Some Generalisations — The Ovum Theory ,
the Gastrcea Theory , Fact of Recapitulation , Organic Con-
tinuity

In his exercitation “ on the efficient cause of the

chicken,” Harvey (1651) confesses that “although it be a
known thing subscribed by all, that the foetus assumes its
original and birth from the male and female, and conse-
quently that the egge is produced by the cock and henne,
and the chicken out of the egge, yet neither the schools of
physicians nor Aristotle’s discerning brain have disclosed
the manner how the cock and his seed doth mint and
coine the chicken out of the egge.” The marvellous
facts of growth are familiar to us — the sprouting corn
and the opening flowers, the growth of the chick within
the egg and of the child within the womb ; yet so

difficult is the task of inquiring wisely into this marvel-
lous renewal of life that we must reiterate the old

confession: “ ingratissimum opus scribere ab iis quae,

multis a natura circumjectis tenebris velata, sensuum
lucis inaccessa, liominum agitantur opinionibus.”

1. Modes of Reproduction. — The simplest animals
divide into two or into many parts, each of which becomes a
full-grown Protozoon. There is no difficulty in understanding

CHAP. XII

The Life-History of Animals 185

why each part should be able to regrow the whole, for each
is a fair sample of the oi'iginal whole. Indeed, when a
large Protozoon is cut into two or three pieces with a knife,
each fragment is often able to retain the movements and
life of the intact organism. Among the Protozoa we find
some in which the multiplication looks like the rupture of a
cell which has become too large ; in others numerous buds
are set free from the surface ; in others one definitely-formed
bud (like an overflow of the living matter) is set free ; in
others the cell divides into two equal parts, after the
manner of most cells ; and numerous divisions may also
occur in rapid succession and within a cyst, that is, in
limited time and space, with the result that many “spores”
are formed. These modes of multiplication form a natural
series.

In the many-celled animals multiplication may still pro-
ceed by the separation of parts ; indeed the essence of
reproduction always is the separation of part of an organ-
ism to form — or to help to form — a new life. Sponges bud
profusely, and pieces are sometimes set adrift ; the Hydra
forms daughter polypes by budding, and these are set free ;
sea-anemones and several worms, and perhaps even some
star-fishes, multiply by the separation of comparatively large
pieces. But this mode of multiplication— which is called
asexual — has evident limitations. It is an expensive way
of multiplying. It is possible only among comparatively
simple animals in which there is no very high degree of
differentiation and integration. For though cut-off pieces
of a sponge, Hydra , sea-anemone, or simple worm may
grow into adult animals, this is obviously not the case
with a lobster, a snail, or a fish. Thus with the excep-
tion of the degenerate Tunicates there is no budding
among Vertebrates, nor among Molluscs, nor among
Arthropods.

The asexual process of liberating more or less large
parts, being expensive, and possible only in simpler animals,
is always either replaced or accompanied by another
method — that of sexual reproduction. The phrase “ sexual
reproduction ” covers several distinct facts : ( a ) the separa-

PART III

• 86 The Study of Animal Life

tion of special reproductive cells ; ( b ) the production of two
different kinds of reproductive cells (spermatozoa and ova),
which are dependent on one another, for in most cases an
ovum comes to nothing unless it be united with a male-cell
or spermatozoon, and in all cases the spermatozoon comes
to nothing unless it be united with an ovum ; ( 'c ) the pro-
duction of spermatozoa and ova by different (male and
female) organs or individuals.

(a) It is easy to think of simple many-celled animals
being multiplied by liberated reproductive cells, which
differed but little from those of the body. But as more
and more division of labour was established in the bodies
of animals, the distinctness of the reproductive cells from
the other units of the body became greater. Finally, the
prevalent state was reached, in which the only cells able
to begin a new life when liberated are the reproductive
cells. They owe this power to the fact that they have not
shared in making the body, but have preserved intact the
characters of the fertilised ovum from which the parent
itself arose.

(1) But, in the second place, it is easy to conceive of a
simple multicellular animal whose liberated reproductive
cells were each and all alike able to grow into new
organisms. In such a case, we might speak of sexual
reproduction in one sense, for the process would be different
from the asexual method of liberating more or less large
parts. But yet there would be no fertilisation and no sex,
for fertilisation means the union of mutually dependent
reproductive cells, and sex means the existence of two
physiologically different kinds of individuals, or at least
of organs producing different kinds of reproductive cells.
We can infer from the Protozoa how fertilisation or the union
of the two kinds of reproductive cells may have had a
gradual origin. .F or in some of the simplest Protozoa, e.g.
Protomyxa, a large number of similar cells sometimes flow
together ; in a few cases three or more combine ; in most a
couple of apparently similar units unite ; while in a few
instances, e.g. Vorticella , a small cell fuses with a large one,
just as a spermatozoon unites with an ovum.

chap, xii The Life-History of Animals 187

(c) But the higher forms of sexual reproduction imply
more than the liberation of special reproductive cells, more
than the union of two different and mutually dependent
kinds of reproductive cells, — they imply the separation
of the sexes. The problem of sexual reproduction becomes
less difficult when the various facts are discussed separ-
ately, and if you grant that there is no great difficulty
in understanding the liberation of special cells, and
no great difficulty in understanding why two different
kinds should in most cases have to unite if either is to
develop, then I do not think that the remaining fact —
the evolution of male and female individuals — need remain
obscure.

If we study those interesting Infusorian colonies, of
which Volvox is a good type, the riddle may be at least
partially read. Though Protozoa, they are balls of cells, in
which the component units are united by protoplasmic
bridges and show almost no division of labour. From
such a ball of cells, units are sometimes set free which
divide and form new colonies. In other conditions a less
direct multiplication occurs. Some of the cells — apparently
better fed than their neighbours — become large; others,
less successful, divide into many minute units. The large
kind of cell is fertilised by the small kind of cell, and there
is no reason why we should not call them ova and sperma-
tozoa respectively. In such a Volvox , two different kinds
of reproductive cell are made within one organism. But
we also find Volvox balls in which only ova are being
made, and others in which only spermatozoa are being
made. The sexes are separate. Indeed we have in Vol-
vox, as Dr. Klein — an enthusiastic investigator of this form
—rightly says, an epitome of all the great steps in the
evolution of sex.

So far I have stated facts ; now I shall briefly state the
theory by which Professor Geddes has sought to rationalise
these facts.

All through the animal series, from the active Infusorians
and passive Gregarines, to the feverish birds and sluggish
reptiles, and down into the detailed contrasts between order

iS8

PART II!

The Study of Animal Life

and order, species and species, an antithesis may be read
between predominant activity and preponderant passivity,
between lavish expenditure of energy and a habit of storing,
between a relatively more disruptive {/catabolic) and a re-
latively more constructive {anabolic) series of changes in
the protoplasmic life of the creature. The contrast between
the sexes is an expression of this fundamental alternative of
variation.

The theory is confirmed by contrasting the characteristic
product of female life — passive ova, with the characteristic
product of male life — active spermatozoa ; or by summing
up the complex conditions (abundant food, favourable
temperature, and the like) which favour the production of
female offspring, with the opposite conditions which favour
maleness ; or by contrasting the secondary sexual char-
acters of the more active males {e.g. bright colours, smaller
size) with the opposite characteristics of their more passive
mates.

Apart from the general problem of the evolution of sex,
those who find the subject interesting should think about
the evolution of the so-called “ sexual instincts,” as illus-
trated in the attraction of mate to mate. As to the actual
facts of pairing and giving birth, it seems to me that I have
suggested the most profitable way of considering these in a
former part of this book where courtship and parental care
are discussed, though I believe firmly with Thoreau, that
“ for him to whom sex is impure, there are no flowers in
nature.”

2. Divergent Modes of Reproduction. — {a) Herma-
phroditism.— Especially among lower animals, both ova
and spermatozoa may be produced by one individual,
which is then said to be hermaphrodite. So most common
plants produce both seeds and pollen. Some sponges and
stinging animals, many “ worms,” e.g. earthworm and leech,
barnacles and acorn-shells among crustaceans, one of the
edible oysters, the snail, and many other molluscs, the sea-
squirts, and the hagfish, are all hermaphrodite. But it
should be noted that the organs in which ova and sperma-
tozoa are produced are in most cases separate, that the two

chap, xn The Life- History of Animals 189

kinds' of cells are usually formed at different times, and
that the fertilisation of ova by spermatozoa from the same
animal very rarely occurs. It is very likely that the
bisexual or hermaphrodite state of periodic maleness and
femaleness is more primitive than that of separate sexes,
which, except in tunicates, a few fishes and amphibians,
and casual abnormalities, is constant among the backboned
animals.

(b') Parthenogenesis seems to be a degenerate form of
sexual reproduction in which the ova produced by female
organisms develop without being fertilised by male cells.
Thus “the drones have a mother but no father,” for they
develop from ova which are not fertilised. In some rotifers
the males have never been found, and yet the fertility of the
females is very great; in many small crustaceans (“water-
fleas ”) the males seem to die off and are unrepresented for
long periods ; in the aphides males may be absent for a
summer (or in a greenhouse for years) without affecting the
rapid succession of female generations.

(f) Alternation of Generations. — A fixed asexual zoophyte
or hydroid sometimes buds off and liberates sexual swim-
ming bells or medusoids, whose fertilised ova develop into
embryos which settle down and grow into hydroids. This is
perhaps the simplest and clearest illustration of alternation
of generations.

In autumn the freshwater sponge ( Spongilla ) begins
to suffer from the cold and the scarcity of food. It dies
away ; but some of the units club together to form
“ gemmules ” from which in spring male and female
sponges are developed. The males are short-lived, but
their spermatozoa fertilise the ova of the females. The
fertilised ovum develops into a ciliated embryo, and this
into the asexual sponge, which produces the gemmules.

The large free-swimming and sexual jellyfishes of the
genus Aurelia produce ova and spermatozoa ; from the
fertilised ovum an embryo develops not into a jellyfish, but
into a sessile HydraA\\s& animal. This grows and divides
and gives origin asexually to jellyfish.

Similar but sometimes more complicated alternations

190

I' ART II!

The Study of Animal Life

occur in some worm-types (some flukes, threadworms, ’etc.),
and as .high up in the series as Tunicates ; while among
plants analogous alternations are very common, e.g. in the
life-cycles of fern and moss.

Fig. 35. — Diagram of a hydroid colony, some of the individuals of which have
been modified as swimming -bells or medusoids; one of these has been
liberated.

3. Historical. — In the seventeenth and eighteenth cen-
turies, naturalists had a short and easy method of dealing with
embryology. They maintained that within the seed of a
plant, within the egg of a bird, the future organism was
already present in miniature. Every germ contained a
miniature model of the adult, which in development was

CHAP. XII

The Life-History of Animals 191

simply unfolded. It was to this unfolding that the word
evolution (as a biological term) was first applied. But not
only did they compare the germ to a complex bud hiding
the already formed organs within its hull, they maintained
that it included also the next generation and the next and
the next. Some said that the ovum was most important,
that it required only the sperm’s awakening touch and it
began to unfold ; others said that the animalcules or
spermatozoa produced by male animals were most im-
portant, that they only required to be nourished by the
ova. The two schools nicknamed one another “ ovists ”
and “ animalculists.” The preformation-theories were false,
as Harvey in the middle of the seventeenth century discerned,
and as Wolff a century later proved, because germs are
demonstrably simple, and because embryos grow gradually
part by part. But in a later chapter we shall see that the
theories were also strangely true.

4. The Egg-cell or Ovum produced by a female animal,
or at least by a female organ (ovary), exhibits the usual
characteristics of a cell. It often begins like an Amoeba,
and may absorb adjacent cells ; in most cases it becomes
surrounded by an envelope or by several sheaths ; in
many cases it is richly laden with yolk derived from various
sources. In the egg of a fowl, the most important part
(out of which the embryo is made) is a small area of trans-
parent living matter which lies on the top of the yellow
yolk and has a nucleus for its centre ; round about
there is a coating of white-of-egg ; this is surrounded by
a double membrane which forms an air-chamber at the
broad end of the egg ; outermost is the porous shell of
lime.

While there must be a general relation between the size
of the bird and that of the egg, there are many inconsisten-
cies, as you will soon discover if you compare the eggs
of several birds of the same size. It is said that the eggs
of birds which are rapidly hatched and soon leave the nest
tend to be large, and that there is some relation between the
size of eggs and the number which the bird has to cover.
It seems probable, however, from what one notices in the

192

PART III

The Study of Animal Life

poultry yard and in comparing the constitution of different
birds, that a highly-nourished and not very energetic bird
will have larger eggs than one of more active habits and
sparser diet.

The egg-shell consists almost wholly of carbonate of
lime, and the experiments of Irvine have shown that a hen can
form a carbonate of lime shell from other lime salts. It is
formed around the egg in the lower part of the oviduct, and
is often beautifully coloured with pigments allied to those of
blood and bile. These colours often harmonise well with
the surroundings, but how this advantageous result has
been wrought out is uncertain.

Eggs differ greatly in regard to the amount of yolk which
they contain ; thus those of birds and reptiles have much, while
those of all mammals except the old-fashioned Monotremes
have hardly any. This is related partly to the number of
eggs which are produced, and partly to the amount of food-
capital which the embryo requires before other sources
of supply become available. The young of birds and
reptiles feed on the yolk until they are hatched, the unborn
young of all the higher (placental) mammals absorb food
from the mothers. The different sizes of egg usually
depend upon the amount of yolk, for the really vital portion
out of which the embryo is made is always very small.

There are many differences also in regard to the outer
envelopes, witness the jelly around the spawn of frogs, the
firm but delicate - skin around the ova of cuttlefish, the
“horny” mermaid’s-purse enclosing the skate’s egg, the
chitinous sheath surrounding the ova of many insects, the
calcareous shell in birds and most reptiles.

5. The Male-Cell or Spermatozoon produced from a male
animal, or at least from a male organ (testis), is very differ-
ent from the ovum. It is very minute and very active. If
we compare an ovum to an Amoeba or to an encysted
Gregarine among Protozoa, we may liken the spermatozoon
to ar minute monad Infusorian. It is a very small cell,
bearing at one end a “head,” which consists mostly of
nucleus, prolonged at the other end into a mobile “ tail,”
which lashes the head along.

chap, xii The Life- History of Animals 193

The spermatozoon, though physiologically the comple-
ment of the ovum, is not its morphological equivalent.
The precise equivalent of the ovum is a primitive male-cell
or mother-sperm-cell, which divides repeatedly and forms a
ball or clump of spermatozoa. This division is to be com-
pared with the division or segmentation of the ovum, which
we shall afterwards discuss.

In some cases spermatozoa which have been transferred
to a female may lie long dormant there. Thus those
received by the queen-bee during her nuptial flight may last
for a whole season, or even for three seasons, during which
they are used in fertilising those ova which develop into
workers or queen-bees. Quite unique is the case of one of
Sir John Lubbock’s queen-ants, which, thirteen years after
the last sexual union with a male, laid eggs which
developed.

6. Maturation of the Ovum. — Most ova before they are
fertilised are subject to a remarkable change, the precise
meaning of which is not certainly known. The nucleus of
the ovum moves to the surface and is halved twice in rapid
succession. Two minute cells or polar globules are thus
extruded, and come to nothing, while the bulk of the
nucleus is obviously reduced by three-fourths. It may be
that the ovum is only behaving as other cells do at the
limit of growth, or that it is exhibiting in an ineffective sort
of way the power of independent division which all the re-
productive cells of very simple many-celled animals perhaps
possessed ; it may be that it is parting with some surplus
material which is inconsistent with or no longer necessary
to its welfare, and there are other theories. One fact,
however, seems well established, that parthenogenetic ova,
which are able to develop into embryos- without being
fertilised, extrude only one polar globule, a fact which
suggests that the amount of nucleus thus retained some-
how makes up for the absence of a spermatozoon.

7. Fertilisation. — When a pollen grain is carried by an
insect or by the wind to the stigma of a flower, it grows
down through the tissue of the pistil until it reaches the
ovule and the egg-cell which that contains. Then a nuclear

O

194 The Study of Animal Life fart m

element belonging' to the pollen cell unites with the nucleus
of the egg-cell. The union is intimate and complete.

When spermatozoa come in contact with the egg-shell
of a cockroach ovum, they move round and round it in
varying orbits until one finds entrance through a minute
aperture in the shell. It works its way inwards until its
nuclear part unites with that of the ovum. The union is
again intimate and complete.

Fig. 36. — Diagram of the development of spermatozoa (upper line), of the
maturation and fertilisation of the ovum (lower line).
cl 1 primitive amoeboid sex-cell; A, ovum with nucleus («); B, ovum extruding
the first polar body (ft1) and leaving the nucleus (n1) reduced by' half ; C,
extrusion of the second polar body (/>-), the nucleus (n-) now reduced to a
fourth of its original size ; 1, a mother-sperm-cell, dividing (2 and 3) into
spermatozoa (sfi) ; D, the entrance of a spermatozoon into the ovum ; E, the
male nucleus ( sfi.tt ) and the female nucleus («2) approach one another, and
are about to be united, thus consummating the fertilisation. (From the
Evolution of Sex.)

Both in plants and in animals the male cell is attracted
to the female cell, the two nuclei unite thoroughly, and,
when fertilisation is thus effected, the egg-cell is usually
impervious to other sperms.

A single nucleus of double origin is thus established,
and the egg-cell begins to divide. Some idea both of the
orderly complexity of the nuclear union and of the careful-
ness of modern investigation may be gained from the fact
that the nuclei of the two daughter-cells which result from

chap, xii The Life-History of Animals 195

the first division of the egg-cell have been shown to consist
in equal proportions of material derived from the male-
nucleus and from the ovum-nucleus.

Yet in the last century naturalists still spoke of an “ aura
seminalis,” and believed that a mere breath, as it were, of
the male cell was sufficient to fertilise an egg, and it was
only in 1843 that Martin Barry discerned the presence of
the spermatozoon within the ovum.

8. Segmentation and Development. — The fertilised
egg-cell divides, and by repeated division and growth of
cells every embryo, of herb and tree, of bird and beast, is
formed. On the quantity and arrangement of the yolk the
character of the segmentation depends. When there is
little or no yolk the whole ovum divides into equal parts, as
in sponge, earthworm, starfish, lancelet, and higher mammal.
When there is more than a little yolk, and when this sinks
to the lower part of the egg-cell, the division is complete
but unequal, and this may be readily seen by examining
freshly-laid frog spawn. When the yolk is accumulated in
the core of the egg-cell, the more vital superficial part
divides, as in insects and crustaceans. Lastly, when the
yolk is present in large quantity as in the ova of gristly
fishes, reptiles, and birds, the division is very partial, being
confined to a small but rapidly extending area of formative
living matter, which lies like a drop on the surface of the
yolk.

As the result of continued division, a ball of cells is
formed. This may be hollow (a blastosphere ), or solid
(a morula , i.e. like a mulberry), or it may be much modi-
fied in form by the presence of a large quantity of yolk.
Thus in the hen’s egg what is first formed is a disc of cells
technically called the blastoderm , which gradually spreads
around the yolk.

The hollow ball of cells almost always becomes dimpled
in or invaginated, as an india-rubber ball with a hole in it
might be pressed into a cup-like form. The dimpling is the
result of inequalities of growth. The two-layered sac of cells
which results is called a gaslrula , and the cavity of this sac
becomes in the adult organism the digestive part of the

196

I' ART III

The Study of Animal Life

food-canal. Where there is no hollow ball of cells, but
some other result of segmentation, the formation of a gastrula

is not so obvious. Yet
in most cases some
analogous infolding is
demonstrable.

In the hollow sac
( a) of cells there are
already two layers.
The outer, which is
called the ectoderm
or epiblast, forms in
the adult the outer
skin, the nervous
system, and the most
important parts of the
sense - organs. The
inner, which is called
( l ) the endoderm or hypo-
blast, forms the lining
of the most import-
ant part of the food-
canal, and of such
appendages as lungs,
liver, and pancreas

Fig. 37. — The formation of the two-layered gas- . . . ,

trula front the invagination of a hollow sphere Which are OUtgrOWthS
of cells. (From the Evolution 0/ Sex; after from jj- pU(- Jn ag
Haeckel.) .

animals above the
Sponges and Ccelenterates, a middle layer appeal's between
the other two. From this — the mesoderm or mesoblast —
the muscles, the internal skeleton, the connective-tissue, etc.,
are formed.

9. Some Generalisations. — (a) The “ Ovum - Theory A
To realise that almost every organism from the sponge to
the highest begins its life as a fertilised egg-cell, and is
built up by the division and arrangement, layering and fold-
ing of cells, should not lessen, but should greatly enhance,
the wonder with which we look upon life. If the end
of this constantly repeated process of development be

cuAr. xii The Life-History of Animals 197

something to marvel at, the same is equally true of its
beginning.

( b ) The Gastraa Theory. From the frequent, though
not universal occurrence of the two-layered gastrula stage in
the development of animals, Haeckel concluded that the
first stable form of many -celled animal must have been
something very like a gastrula. He called this hypothetical
ancestor of all many-celled animals a Gastrcea , and his infer-
ence has found favour with many naturalists. Some of the
simplest sponges, polypes, and “ worms ” are hardly above
the gastrula level.

(c) Recapitulation. When we take a general survey
of the animal series, we recognise that the simplest animals
are single cells, that the next simplest are balls of cells like
Volvox, and that the next simplest are two-layered sacs of
cells like the simple sponges, polypes, and worms above
referred to. These represent the three lowest steps in the
evolution of the race. They are not hypothetical steps in a
hypothetical ladder of ascent, they are realities.

When we take a general survey of the individual
development of many-celled animals, we recognise that all
begin as single egg-cells, and that the ova divide into balls
of cells, which become in most cases two -layered sacs of
cells. It is therefore evident that the first three chapters in
individual history are precisely the first three steps in racial
history.

Von Baer, one of the pioneer embryologists in the first
half of this century, discerned that the individual life-history
was in its general course a recapitulation of the history of
the race. He recognised that even one of the higher
animals, let us say a rabbit, began at the beginning as a
Protozoon, that it slowly acquired the features of a primitive
Vertebrate, that it subsequently showed the character of a
young fish, afterwards of a young reptile, then of a young
mammal, then of a young rodent, finally of a young rabbit.
He confessed his inability to distinguish whether three very
young embryos, freed from their surroundings, were those
of reptiles, birds, or mammals. In stating Von Baer’s
vivid idea of development as progress from the simple

PART III

T98 The Study of Animal Life

to the complex, from the general to the special, we must
be careful to notice that he did not say that the young
mammal was once like a little fish, afterwards .like a reptile,
and so on ; he compared the embryo mammal at one stage
with the embryo fish, at another stage with the embryo
reptile, which is a very different matter.

Fig, 3S. — Embryos of fowl, a ; dog, b ; man, c. (From Chambers’s Encyclop. ;

after Haeckel.)

Fritz Muller, in his Facts for Darwin , illustrated the
same idea in relation to Crustacea. When a young cray-
fish is hatched, it is practically a miniature adult. When
a young lobster is hatched, it differs not a little from the
adult, and is described as being at a Mysis stage, — Mysis
being a prawn-like crustacean. It grows and moults and
becomes a little lobster. When a crab is hatched, it is
quite unlike the adult, it is liker one of the humblest
Crustacea such as the common water-flea Cyclops , and is
described as a Zoea. This Zoea grows and moults and
becomes, not yet a crab but a prawn-like animal with ex-
tended tail, a stage known as the Megalopa. This grows and
moults, tucks in its tail, and becomes a young crab. And
again, when the shrimp-like crustacean, known as Pcnceus,
is hatched, it is simpler than any known crustacean, it is
an unringed somewhat shield-shaped little creature with
three pairs of appendages and a median eye. It is known
as a N auplius and resembles the larvae of most of the simpler
crustaceans. It grows and moults and becomes a Zoea,
grows and moults and becomes a Mysis , grows and moults
and becomes a Penceus.

chap, xir The Life-History of Animals 199

Now these life-histories are hardly intelligible at all
unless we believe that Penceus does in some measure recapi-
tulate the steps of racial progress, that the crab does so
to a slighter extent, that the lobster has abbreviated its
obvious recapitulation much more, while the crayfish has
found out a short cut in development. Let us exercise our
imagination and think of the ancestral Crustacea perhaps
not much less simple than the Nauplius larvae which many

Fig. 39.— Life-history of Penceus ; the Nauplius.

of them exhibit. In the course of time some pushed for-
ward in evolution and attained to the level of structure
represented by the Zoea larvae. At this station some
remained and we have already mentioned the “ water-flea ”
Cyclops as a crustacean which persists near this level. But
others pushed on and reached a stage represented by
Mysis , and finally the highest crustaceans were evolved.

Now to a certain extent these highest crustaceans have
to travel in their individual development along the rails
laid down in the progress of the race. Thus Penceus ,

200

TART III

The Study of Animal Life

starting of course as an ovum at the level of the Protozoa,
has to stop as it were at the first distinctively crustacean
station — the Nauplius stage. After some change and
delay, it continues to progress, but again there is a halt and
a change at the Zoea station. Finally there is another

delay at the My sis stage before the Pawns reaches its
destination. The crab, on the other hand, stops first at
the Zoea station, the lobster at the My sis station, while the
crayfish though progressing very gradually like all the

others has if you do not find the simile too grotesque — a

through-carriage all the way.

Fig. 39 b. — Life-history of Petttru t; a later stage.

202

TART III

The Study of Animal Life

N

'C

til

B

o

u

fa

One must be careful not to press the idea of recapitulation
too far, (i) because the individual life-history tends to skip

stages which occurred in the an-
cestral progress ; (2) because the
young animal may acquire new
characters which are peculiar to
its own near lineage and have
little or no importance in connec-
tion with the general evolution of
its race ; (3) because, in short,
the resemblance between the indi-
vidual and racial history (so far
as we know them) is general, not
precise. Thus we regard Nauplius
and Zoea rather as adaptive larval
forms than as representatives of
ancestral crustaceans. More-
over, if one insists too much on
the approximate parallelism be-
tween the life-history of the indi-
| vidual and the progress of the
£ race, one is apt to overlook the
° deeper problem — how it is that
2 the recapitulation occurs to the
a extent that it undoubtedly does.
£ The organism has no feeling for
I history that it should tread a
g sometimes circuitous path, be-
cause its far-off ancestors did so.
To some extent we may think of
inherited constitution as if it were
the hand of the past upon the
organism, compelling it to become
thus or thus, but we must realise
that this is a living not a dead
hand ; in other words these meta-
morphoses have their efficient causes in the actual con-
ditions of growth and development. The suggestion of
Kleinenberg referred to in a preceding chapter helps us, for

O

chap, xii The Life-History of Animals 203 .

if we ask why an animal develops a notochord only to have
it rapidly replaced by a backbone, part of the answer surely
is that the notochord which in the historical evolution supplied
the stimulus necessary for the development of a backbone, is
still necessary in the individual history for the same purpose.

But there is no doubt that the idea of recapitulation is a
very helpful one, in regard to our own history as well as in
regard to animals, and we would do well to think of it
much, and to read how Herbert Spencer ( Principles of
Biology, Lond. 1864-66) has discussed it in harmony with his
general formula of evolution as a progress from the homo-
geneous to the heterogeneous ; how Haeckel ( Generelle Mor-
phologic, Berlin, 1866) has illustrated it, and pithily summed
it up in his “ fundamental law of biogenesis ” ( Biogenetisches
Grnndgesetz ), saying that ontogeny (individual develop-
ment) recapitulates phylogeny (racial history) ; how Milnes
Marshall (see Nature, Sept. 1890) has recently tested and
criticised it, defining the limits within which the notion
can be regarded as true, and searching for a deeper rationale
of the facts than the theory supplies.

(d) Organic Continuity. In a subsequent chapter on
heredity, which simply means the relation of organic
continuity between successive generations, I shall explain
the fundamental idea that the reproductive cells owe their
power of developing, and of developing into organisms like
the parents, to the fact that they are in a sense continuous
with those which gave origin to the parents. A fertilised
egg-cell with certain qualities divides and forms a “ body ”
in which these qualities are expressed, distributed, and
altered in many ways by division of labour. But it also
forms reproductive cells, which do not share in the up-
building of the body, which are reproductive cells in fact
because they do not do so, because they retain the intrinsic
qualities of the original fertilised ovum, because they
preserve its protoplasmic tradition. If this be so, and
there is much reason to believe it, then it is natural and
necessary that these cells, liberated in due time, should
behave as those behaved whose qualities they retain. It is
necessary that like should beget like.

CHAPTER XIII

THE PAST HISTORY OF ANIMALS

i. The two Records — 2. Imperfection of the Geological Record —
3. Paleontological Series — 4. Extinction of Types — 5. Various
Difficulties — 6. Relative Antiquity of Animals

1. The Two Records. — Reviewing the development of the
chick, W. K. Parker said, “ Whilst at work I seemed
to myself to have been endeavouring to decipher a palimp-
sest, and that not erased and written upon just once, but
five or six times over. Having erased, as it were, the
characters of the culminating type — those of the gaudy
Indian bird — I seemed to be amongst the sombre grouse,
and then, towards incubation, the characters of the Sand-
Grouse and Hemipod stood out before me. Rubbing these
away, in my downward walk, the form of the Tinamou
looked me in the face ; then the aberrant Ostrich seemed
to be described in large archaic characters ; a little while
and these faded into what could just be read off as per-
taining to the Sea Turtle ; whilst, underlying the whole,
the Fish in its simplest Myxinoid form could be traced
in morphological hieroglyphics.”

There is another palimpsest — the geological record
written in the rocks. For beneath the forms which dis-
appeared, as it were, yesterday, — the Dodo and the Solitaire,
the Moa and the Mammoth, the Cave Lion and the Irish
Elk, — there are mammals and birds of old-fashioned type the
like of which no longer live. Beneath these lie the giant

chap, xiii The Past History of Animals 205

reptiles, beneath these great amphibians, preceded by hosts
of armoured fishes, beyond the first traces of which only
backboneless animals are found. Yet throughout the
chapters of this record, written during different aeons on the
earth’s surface, persistent forms recur from age to age,
many of them, such as some of the lamp-shells or Brachio-
pods, living on from near the apparent beginning even until
now. But other races, like the Trilobites, have died out,
leaving none which we can regard as in any sense their
direct descendants. Other sets of animals, like the Ganoid
fishes, grow in strength, attain a golden age of prosperous
success, and wane away. As the earth grew older nobler
forms appeared, and this history from the tombs, like
that from the cradles of animals, shows throughout a
gradual progress from simple to complex.

2. Imperfection of the Geological Record, — If complete
records of past ages were safely buried in great treasure-
houses such as Frederic Harrison proposes to make for the
enlightenment of posterity, then palaeontology would be easy.
Then a genealogical tree connecting the Protist and Man
would be possible, for we should have under our eyes what
is now but a dream — a complete record of the past.

The record of the rocks is often compared to a library
in which shelves have been destroyed and confused, in
which most of the sets of volumes are incomplete, and
most of the individual books much damaged. When we
consider the softness of many animals, the chances against
their being entombed, and the history of the earth’s crust,
our wonder is that the record is so complete as it is, that
from “ the strange graveyards of the buried past ” we can
learn so much about the life that once was.

We must not suppose the record to be as imperfect as
our knowledge of it. Thus many regions of the earth’s
surface have been very partially studied, many have not
been explored at all, many are inaccessible beneath the sea.

As to the record, the rocks in which fossils are found
are sedimentary rocks formed under water, often they have
been unmade and remade, burnt and denuded. The
chances against preservation are many.

206

PART III

The Study of Animal Life

Soft animals rarely admit of preservation, those living
on land and in the air are much less likely to be preserved
than those living in water, the corpses of animals are
often devoured or dissolved. Again the chances against
preservation are many.

3. Palaeontological Series. — Imperfect as the geological
record is, several marvellously complete series of related
animals have been disentombed. Thus, a series of fossilised
freshwater snails ( Planorbis ) has been carefully worked
out ; its extremes are very different, but the distinctions
between any two of the intermediate forms are hardly
perceptible. The same is true in regard to another set of
freshwater snails ( Paludina ), and on a much larger scale
among the extinct cuttlefishes (Ammonites, etc.) whose shells
have been thoroughly preserved. The modern crocodiles
are linked by many intermediate forms to their extinct
ancestors, and the modern horse to its pigmy progenitors.
In cases like these, the evidences of continuously progress-
ive evolution are conclusive.

4. Extinction of Types. — A few animals, such as some
of the lamp-shells or Brachiopods, have persisted from almost
the oldest rock-recorded ages till now. In most cases,
however, the character of the family or order or class has
gradually changed, and though the ancient forms are no
longer represented, their descendants are with us. There
is an extinction of individuals and a slow change of
species.

On the other hand there are not a few fossil animals
which have become wholly extinct, whose type is not
represented in the modern fauna. Thus there are no
animals alive that can be regarded as the lineal descendants
of Trilobites and Eurypterids, or of many of the ancient
reptiles. There is no doubt that a race may die out.
Many different kinds of heavily armoured Ganoid fishes
abounded in the ages when the Old Red Sandstone was
formed, but only seven different kinds are now alive.
The lamp-shells and the sea-lilies, once very numerous, are
now greatly restricted. Once there were giants among
Amphibians, now almost all are pigmies.

CHAP. XIII

207

The Past History of Animals

It is difficult to explain why some of the old types
disappeared. The extinction was never sudden. Formid-
able competitors may have helped to weed out some ; for
cuttlefish would tend to exterminate trilobites, and voracious
fishes would decimate cuttlefish, just as man himself is
rapidly and inexcusably annihilating many kinds of beasts
and birds. But, apart from the struggle with competitors,
it is likely that some types were insufficiently plastic to save
themselves from changes of environment, and it seems likely
that others were victims to their own constitutions, becoming
too large, or too sluggish, or too calcareous ; or, on the
other hand, too feverishly active. The “ scouts ” of evolution
would be apt to become martyrs to progress ; the “ laggards ”
in the race would tend to become pillars of salt ; the
path of success was oftenest a via media of compromise.
Samuel Butler has some evidence for saying that “ the race
is not in the long run to the phenomenally swift, nor the
battle to the phenomenally strong ; but to the good average
all-round organism that is alike shy of radical crotchets and
old world obstructiveness. ”

5. Various Difficulties. — Nowadays it seems natural
to us to regard the fossils in the rocks as vestiges of a
gradual progress or evolution. As some still find difficulty
in accepting this interpretation, I shall refer to three
difficulties occasionally raised.

(a) It is said that the number of fossils in successive
strata does not increase steadily as we ascend to modern
times — that the numerical strength of the fauna is strangely
irregular. Thus (in 1872) it was computed that 10,000
species were known from the early Silurian rocks, while the
much later Pennian yielded only 300. But those who use
such arguments should mention that a large number of the
Silurian species were discovered by the marvellous industry
of one man in a favourable locality, and that the rocks of
the Permian system are ill adapted for the preservation of
fossils. Moreover, we cannot compute the relative dura-
tion of the different periods, we cannot infer evolutionary
progress from the number of species, and we must make
many allowances for the imperfections of the record.

20S The Study of Animal Life part m

( l> ) It is said that the occurrence of Fishes in the
Silurian, and of many highly organised Invertebrates in the
still earlier Cambrian, is inconsistent with a theory which
would lead us to expect very simple fossil forms to begin
with. But to say so is to forget that we have no concep-
tion of the vast duration of periods like the Silurian and
Cambrian, while the antecedent Archaean rocks in which we
might look for traces of simple ancestral organisms have
been shattered and altered too thoroughly to reveal any
important secrets as to the earliest animals.

(c) It is maintained that organic evolution proceeds very
slowly, and that the geologists and biologists demand more
millions than the experts in astronomical physics can grant
them. But there is considerable difference of opinion as to
the unthinkable length of time during which the earth may
have been the home of life ; we are apt to measure the rate
of evolutionary change by the years of a man’s lifetime which
lasts but for a geological moment ; and there is reason to
believe that the simpler animals would change and take
great steps of progress much more rapidly than those of
high degree.

6. Relative Antiquity of Animals, — I have not much
satisfaction in submitting the following table showing
the relative antiquity of the higher animals. Such a table
is only an approximation ; it does not suggest the great
differences in the duration of the various periods, nor how
the classes of animals waxed and waned, nor how some types
in these classes dropped off while others persisted. But the
general fact which the table shows is true, — in the course
of time higher and higher forms of life have come into
being. It is true that the remains of mammals are of more
ancient date than those of birds, but it is likely that the
remains of the earliest birds have still escaped discovery ;
moreover, the earliest known mammalian remains seem to
be of those of very simple types.

Cambrian » Many Invertebrates

CHAT. XIII

The Past History of Animals

209

Primary or Pahvozoic

n

p

X

a

0

3

n>

H

cT

2.

0

2.

S'

a

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P*

to

p’

p*

0

p’

to

3

3

3

to

3

0*

Secondary or
Mesozoic

O

Tertiary or
Cainozoic

M

o

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fD

3

g

o

o

fD

3

fD

O

3

fD

3**

fD

>

3

TJ

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p

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fD

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P

Quaternary or
Post-Tertiary

CHAPTER XIV

THE SIMPLEST ANIMALS

r. The Simplest Forms of Life — 2. Survey of Protozoa — 3. The com-
mon Amceba — 4. Structure of the Protozoa — 5. Life of Protozoa
— 6. Psychical Life of the Protozoa — 7. History of the Protozoa
8. Relation to the Earth — 9. Relation to other Forms of Life —
10. Relation to Man

I. The Simplest Forms of Life. — It is likely that the first breath
of life was in the water, for there most of the simplest animals and
plants have their haunts. Simple they are, as an egg is simple
when contrasted with a bird. They are (almost all) unit specks of
living matter, each comparable to, but often more complex than, one
of the numerous unit elements or cells which compose any higher
plant or animal, moss or oak-tree, sponge or man. It is not merely
because they are small that we cannot split them into separate parts
different from one another,— size has little to do with complexity, —
but rather because they are unit specks or single cells. But they are
not “structureless” ; in fact, old Ehrenberg, who described some of
them in 1838 as “perfect organisms” and fancied he saw stomachs,
vessels, hearts, and other organs within them, was nearer the truth
than those who reduce the Protozoa to the level of white of egg.

Nor are they omnipresent, swarming in any drop of water. The
clear water of daily use will generally disappoint, or rather please
us by showing little trace of living things. But take a test-tube of
water from a stagnant pool, hold it between your eyes and the light,
and it is likely that you will see many forms of life. Simple plants
and simple animals are there, the former represented by threads,
ovals, and spheres in green, the latter by more mobile almost
colourless specks or whitish moles which dance in the water. But
besides these there are jerky swimmers whose appearance almost
suggests theirpopularname of “water-fleas,” and wriggling “worms,”

chap, xiv The Simplest Animals 21 1

thinner than thread and lither than eels : both of these may be very
small, but closer examination shows that they have parts and organs,
that they are many-celled nor single-celled animals.

Vary the observations by taking water in which hay stems or other
parts of dusty dead plants have been steeped for a few days, and even
with the unaided eye you will see a thick crowd of the mobile whitish
motes which, from their frequent occurrence in such infusions, are
usually called Infusorians. Or if a piece of flesh be allowed to rot in
an open vessel of water, the fluid becomes cloudy and a thin flaky scum
gathers on the surface. If a drop of this turbid liquid be examined
with a high power of the microscope, you will see small colourless
rods and spheres, quivering together or rapidly moving in almost
incalculable numbers. These, though without green colour, are the
minutest forms of plant life ; they are Bacteria or Bacilli, the
practically omnipresent microbes, some of which as disease germs
thin our human population, while others as cleansers help .to make
the earth a habitable dwelling-place.

2. Survey of Protozoa. — Three great types of unicellular
animals or Protozoa have been recognised in almost every classi-
fication.

(a) The Infusorians, so abundant in stagnant water, have a
common character of activity expressed in the possession of actively
mobile lashes of living matter known as cilia or flagella. Thus
the slipper-animalcule ( Paramacium ) is covered with rows of lash-
ing cilia, while smaller, equally common forms, generally known
as Monads, are borne along by the undulatory movement of one or
two long whips or flagella. The bell-animalcules ( Vorticella ) which
live in crowds, — a white fringe on the water weeds, — are generally
fixed by stalks, but are crowned with active cilia at the upper end of
the somewhat urn-shaped cell.

(b) In marked contrast to these are the parasitic Protozoa, the
Gregarines, which infest most backboneless animals, notably the
male reproductive organs of the earthworm or the gut of lobster and
cockroach. Sluggishness and the absence of all locomotor pro-
cesses are their characteristics.

(c) Between these two extremes of activity and passivity there
is a third type well represented by the much-talked-of Amoeba which
glides about on the mud of the pond, by the sun - animalcules
(Ac l iitospharitt m ) which float in the clear water of brooks, by the
limy-shelled, chalk-forming Foraminifera which move slowly on
seaweeds or at the bottom of shallow water, or in some cases float
at the surface of the sea, and by the flinty-shelled Radiolarians
which live in the open ocean. In all these the living matter
spreads out in thick or thin, stiff or plastic, free or interlacing pro-
cesses, which often admit of a slow gliding motion, and are still

212

The Study of Animal Life

PART III

more useful in surrounding minute food particles. To these root-
like processes, which are capable of very considerable, often almost

constant, change, these
Protozoa owe their gen-
eral name of Rhizopods.
In contrast to the two
preceding types which
have definite boundaries
or “skins,” the Rhizo-
pods are naked, and their
living matter may over-
flow at any point.

As the Infusorians
are for the most part
provided with cilia from
which flagella differ only
in detail, we may speak
of the type as ciliated ;
the self-contained Gre-
garines, often wrapped
up within a sheath, we
may call predominantly
encysted ; while those
forms which are inter-
mediate between these
two extremes, and ex-
hibit outflowing pro-
cesses of living matter,
are called amoeboid in
reference to their most familiar type, the common Amoeba.

But though the members of each class are characterised by the
predominance of one of the three phases of cell-life, they sometimes
pass from one phase to another. Thus the ciliated or the amoeboid
units may become encysted. A

Fig. 40. — A foraminifer {Polystomclla strigillata)
with interlacing processes of the living matter
flowing out on all sides. Magnified 30 times.
(From Chambers’s Encyclof. ; after Max
Schultze.)

Fig. 41.— Protomyxa. i, encysted ; 2, dividing into many units ; 3, these escap-
ing as flagellate cells ; 4, sinking into an amoeboid phase ; 5, fusing into a
plasmodium. (From Chambers s ILncyclop* } after liaeckel.)

As the three phases represent the three physiological possibilities

CHAP. XIV

213

The Simplest Animals

of cell-life, it is natural to find that the very simplest Protozoa, such
as Protomyxa , exhibit a cycle of amoeboid, encysted, and flagellate
phases, not having taken a decisive step along any one of the three
great paths. Moreover, the cells of higher animals may be classified
in the same way. The ciliated cells of the windpipe or the mobile
spermatozoa correspond to Infusorians ; mature ova, fat-cells, de-
generate muscle-cells, correspond to Gregarines, while white blood-
corpuscles and young ova are amoeboid.

3. The common Amoeba. — To find Amoebic, which is not
always easy, some water and mud from a pond should be allowed
to settle in a glass vessel. Samples from the surface of the sediment
should then be removed in a glass tube or pipette, dropped on a
slide, and patiently examined under the microscope. Among the
debris, traversed in most cases by swift Infusorians, the sought -for
Amoeba may be seen, as an irregular mass of living matter, often
obscured with various kinds of particles and minute Alga; which it
has engulfed, but hardly mistakable as it ploughs its way leisurely
among the sediment, sending out blunt and changeful finger-like
processes in the direction towards which it moves, and drawing
in similar processes at the opposite side. From some objects it
recoils, while others of an edible sort it surrounds with its blunt
processes and gets outside of. Intense light makes it contract, and
a minute drop of some obnoxious reagent causes it to round itself off
and lie quiescent. Such is the simple animal which, in 1755, an
early microscopist Rosel von Rosenhof was delighted to describe,
calling it the “ Proteus animalcule.”

4- Structure of the Protozoa. — Most of these Protozoa are
units or single cells, but this contrast between them and the higher
animals is lessened by the fact that many Infusorians, some
Radiolarians, and some of the very lowest forms live inclose combina-
tion, a number of apparent individuals being substantially united in
co-operation. In two quite different ways this compound life of some
Protozoa arises. The “Flower of Tan” [Fuligo or JEthalium
septicum) which in the summer months spreads as a yellowish slime
on the bark of the tanyard, and supplies the student with the
“ largest available masses of undifferentiated protoplasm,” arises from
the flowing together and fusion of a number of smaller amoeboid
units. But in some Infusorians and Radiolarians the colony
arises quite otherwise. Protozoa multiply by division ; each unit
splits into two which thenceforth live separate lives, and by and
by themselves divide. Suppose, however, that the unit divide
incompletely ; suppose that the daughter -units, distinct though
unsevered, redivide, and that the process is continued ; a “ colonial ”
Protozoon is the result. In this case the units do not flow together,
they were never separated. But the “wisdom” of some of these

214

PART III

The Study of Animal Life

early associations has been justified’ in their far-off children, for in
this way the many-celled animals began.

The cell-substance of a Protozoon is living matter, along with
nutritive materials which are approaching that climax, and waste
materials into which some of the cell substance has disintegrated.
The cell has a kernel or nucleus, or more than one, essential to its
complete life. There are bubbles of water taken in along with
food particles, and in nearly all freshwater forms there are one or
two special regions of internal activity, pulsating cavities or con-
tractile vacuoles, which become large and small sometimes rhythmic-
ally, and may burst open on the surface of the cell. They are be-
lieved to help in getting rid of waste, and also in internal circulation.
There is a rind in the Infusorians and Gregarines, and shells of flint
and lime are characteristic of most Foraminifers and Radiolarians.

5. Life of Protozoa. — The life -histories of the Protozoa are
very varied, but some chapters are common to most. They expend
energy in movement ; they regain this by feeding ; their income
exceeds their expenditure, and they grow ; at the limit of growth
they reproduce by dividing into two or many daughter - units ; in
certain states two individuals combine, either interchanging nuclear
elements (in the ciliated Infusorians) or fusing together (as in some
Rhizopods) ; in drought or in untoward conditions, or before
manifold division, they often draw themselves together and encyst
within a sweated-off sheath.

The Protozoa often multiply very rapidly. One divides into
two, the two become four, and in rapid progression the numbers
increase. On Maupas’s calculation a single Infusorian may in four
days have a progeny of a million. The same observer has shed a
new light on another process — that of conjugation, the temporary
or permanent union of two Protozoa, which in the ciliated Infusorians
involves an interchange of nuclear particles. In November 1SS5,
Maupas isolated an Infusorian ( Stylonichia ) and observed its genera-
tions till March 1 886. By that time there had been two hundred and
fifteen generations produced by ordinary division, but since these
lowly organisms do not conjugate with near relatives, conjugation
had not occurred. The result, corroborated in other cases, was
striking. The whole family became exhausted, small, and
“ senile ” ; they ceased to divide or even to feed ; their nuclei
underwent a strange degeneration ; they began to die. But
individuals removed before the process had gone too far were
observed to conjugate with unrelated forms and to live on. The
inference was obvious. Conjugation in these Infusorians is of little
moment to any two individuals ; during long periods it need never
occur, but it is essential to the continued life of the species. “ It
is a necessary condition of their eternal youth.”

chap, xiv The Simplest Animals 215

We must return, however, to the everyday life of the Protozoa.
Rhizopods move by means of outflowing processes of their living
matter which stream out at one comer and are drawn in at another ;
the Infusorians move more rapidly by undulating flagella or by
numerous cilia which work like flexible oars ; the parasitic
Gregarines without any definite locomotor structures sometimes
writhe sluggishly. A few Infusorians have a spasmodic leaping or
springing motion, while the activity of others (like Vorticelld) which
in adult life are fixed, is restricted to the contraction and expansion
of a stalk and to the action of cilia around the opening which serves
as a mouth. Arcella is aided in its movements by the formation of
gas bubbles in different parts of its cell-substance.

The food consists of other Protozoa, of minute Alga;, and of
organic debris, simply engulfed by the Amoebae, wafted by cilia
into the “mouth” of most Infusorians. The parasitic Gregarines
absorb the debris of the cells or tissues of the animals in which they
live, while not a few suck the cell-contents of freshwater Algae like
Spirogyra. A few Protozoa are green, and some are able to use
carbonic acid after the manner of plants. Almost all Radiolarians
and a few Foraminifers live in constant and mutually helpful
partnership or symbiosis with small Algae which flourish within
their cell-substance.

As to the other functions, the cells absorb oxygen and liberate
carbonic acid, digest the food-particles and excrete waste, produce
cysts or elaborate shells.

6. Psychical Life of the Protozoa. — We linger over the
Protozoa because they illumine the beginnings of many activities,
and we cannot leave them without asking what light they cast upon
the conscious life of higher animals. Is the future quite hidden in
these simple organisms or are there hints of it ?

According to some, the Protozoa, with frequently rapid and
useful movements, with capacities for finding food and avoiding
danger, with beautiful and intricate shells, are endowed with the
will and intelligence of higher forms of life. According to others,
their motions are arbitrary and without choice, they are only much
more complex than those of the potassium ball which darts about
on the surface of water, the organisms are drawn by their food
instead of finding it, their powers of selection are sublimed chemical
affinities, their protective cysts are quite necessary results of partial
death, and their houses are but crystallisations. In both interpreta-
tions there is some truth, but the first credits the Protozoa with too
much, the second with too little.

Cienkowski marvelled over the way in which Vampyrella sought
and found a Spirogyra filament and proceeded to suck its contents ;
Engelmann emphasised the wonderful power of adjustment in Arcella

PART III

216 The Study of Animal Life

which evolves gas bubbles and thus rises or rights itself when cap-
sized, and also detected perception and decision in the motions of
young Vorticella or in the pursuit of one unit by another ; Oscar
Schmidt granted them only “a very dim general feeling” and the
power of responding in different ways to definite stimuli ; Schneider
believed that they acted on impulses based upon definite impressions
of contact ; Moebius would credit them with the power of reminis-
cence and Eirner with will.

Romanes finds evidence of the power of discriminative selection
among the protoplasmic organisms, and he quotes in illustration Dr.
Carpenter’s account of the making of shells. “ Certain minute
particles of living jelly, having no visible differentiation of organs
. . . build up ‘ tests ’ or casings of the most regular geometrical
symmetry of form and of the most artificial construction. . . .
From the same sandy bottom one species picks up the coarser quartz
grains, cements them together with phosphate of iron (?) which must
be secreted from their own substance, and thus constructs a flask-
shaped ‘test’ having a short neck and a single large orifice. Another
picks up the finer grains and puts them together with the same
cement into perfectly spherical ‘ tests ’ of the most extraordinary
finish, perforated by numerous small tubes, disposed at pretty regular
intervals. Another selects the minutest sand-grains and the terminal
points of sponge spicules, and works these up together apparently
with no cement at all, but by the * laying ’ of the spicules into
perfect spheres, like homoeopathic globules, each having a single
fissured orifice.” This selecting power is marvellous ; we cannot
explain it ; the animals are alive and they behave thus. But it
must be remembered that even ‘ dead ’ substances have attractive
affinities for some things in preference to others, that the cells of
roots and those lining the food-canal of an animal or floating in its
blood show a power of selection. Moreover, if we begin with a
unit which provides itself with a coating of sponge spicules,
at first perhaps because they were handiest, it is not difficult to
understand why the future generations of that species should con-
tinue to gather these minute needles. Being simply separated parts
of their parents, whose living matter had become accustomed to
the stimulus of sponge spicules, the descendants naturally sustain
the tradition. This organic memory all Protozoa must have,
for the young are separated parts of the parents.

Haeckel was one of the first (1876) to urge the necessity of
recognising the “soul” of the cell. He maintained that the con-
tinuity of organic life led one to assume a similar continuity of
psychical life, that an egg-cell had in it not only the potency of
forming tissues and organs but the rudiments of a higher life as well,
that the Protozoa likewise must be regarded not only as physical

CHAP. XIV

217

The Simplest Animals

but as psychical, in fact that the two are inseparable aspects of one
reality. “ The cell-soul in the monistic sense is the sum-total of
the energies embodied in the protoplasm, and is as inseparable
from the cell-substance as the human soul from the nervous
system.” FOr several years Verworn has been investigating the
psychical life of the Protozoa, lie has conducted his researches
with great care and thoroughness, observing the animals both in
their natural life and in artificial conditions. I shall cite his con-
clusions, translating them freely : “An investigator of the psychical
processes in Protists (simple forms of life) has to face two distinct
problems. The first is comparative, and inquires into the grade of
psychical development which the Protists may exhibit — the known
standard being found of course in man ; the second is physiological,
and inquires into the nature of these psychical processes. Since
we know these only through the movements in which they are
expressed, the investigation is primarily a study of the movements
of Protists.

“ On a superficial observation of these movements the impression
arises in the observer’s mind that they are the result of higher
psychical processes, like the consciously willed activities of men.
Especially the spontaneous movements of advance and recoil, of
testing and searching, give us the impression of being intentional
and voluntary, since no external stimulus can account for them ;
while even some of the movements provoked by stimuli appear on
account of their marked aptness to arise from conscious sensation
and determination.

“ But a critical study of the results yielded by an investigation
of spontaneous and stimulated movements warrants a more secure
judgment than that of the superficial observer, and leads to a con-
clusion opposed to his. To this conclusion we are led, that none
of the higher psychical processes, such as conscious sensations,
representations, thoughts, determinations, or conscious acts of will,
are exhibited by Protists. A number of criteria show that the
movements are in part impulsive and automatic, and in part reflex,
and in both cases expressions of unconscious psychical processes.

“ This opinion is corroborated by an examination of the structure
of these Protists, for this does not seem such as would make it
possible for the individual to have an idea of its own unified self,
and the absence of self-consciousness excludes the higher psychical
processes. Small fragments cut from a Protist cell continue to
make the same movements as they made while parts of the intact
organism. Each fragment is an independent centre for itself.
There is no evidence that the nucleus of the organism is a psychical
centre. There is no unified Psyche.

“Since the characteristic movements persist in such small frag-

218 The Study of Animal Life part hi

merits, they cannot be the expression of any individual consciousness,
for the individuality has been cut in pieces.”

The dilemma is obvious ; either there are no psychical processes
in the Protists, or they are inseparable from the molecular changes
which occur in the parts of the material substance.

If no psychical processes occur in the Protists, where do they
begin ? There is no distinct point in the animal series at which a
nervous system may be said to make its first appearance. If there
are none, even rudimentarily, in the Protists, then these simple
organisms do not potentially include the life of higher organisms.
If there are none in the Protists, are there any in the germs from
which men develop ?

Verworn seizes the other horn of the dilemma, maintaining that
the superficial observers are wrong in crediting the Protozoa with
their own intelligence or with some of it, but right in concluding
that psychical processes of some sort are there. But since he
cannot in any way locate these processes, since he finds that even
small fragments retain their life for a time and behave much as the
entire cells did, he maintains that all life is psychical.

7. History of the Protozoa. — We know that the Protozoa
have lived on the earth for untold ages, for the shells of Fora-
minifera and others may be disentombed from almost the oldest
rocks. The word Protozoa, a translation of the German Urthiere or
primitive animals, suggests that the Protozoa are not only the
simplest, but the first animals, or the unprogressive descendants of
these. Nowadays we can hardly feign to consider this proposition
startling, for we know that all the higher animals, including our-
selves, begin life at the beginning again as single cells. From the
division and redivision of an apparently simple fertilised egg-cell an
embryo is built up which grows from stage to stage till it is
hatched, let us say, as a chick. It is only necessary to extend this
to the wider history of the race. What the egg is to the chick the
original Protozoa were to the animal series ; the present Protozoa
are like eggs which have lived on as such without making much
progress.

We do not know how the Protozoa began to be upon the earth,
whether they originated from not living matter or in some yet more
mysterious way. The German naturalist Oken, a prominent type
of the school of “Natural Philosophers” who flourished about the
beginning of this century, dreamed of a primitive living slime
( Urschleim ) which arose in the sea from inorganic material. His
dream was prophetic of the modern discovery of very simple forms
of life, in connection with one of which there is an interesting and
instructive stoiy. That one, perhaps I should say that supposed
one, was called Bathybius , and since those who are eager to make

chap, xiv The Simplest Animals 219

points against science (that is to say against knowledge) always tell
the story wrongly, I shall make a digression to tell it rightly.

In 1S57 Captain Dayman, in charge of a vessel engaged in con-
nection with cable - laying, discovered on the submarine Atlantic
plateau the abundant presence of slimy material which looked as if
it were alive. Preserved portions of this formless slime were after-
wards described by Huxley, and he named the supposed organism,
partly from its habitat, partly after his friend Haeckel, Bathybius
Haeckelii. On the Porcupine expedition Professors Wyville Thomson
and Carpenter observed it in its fresh state, and Haeckel afterwards
described some preserved specimens. Its interest lay in its
simplicity and apparent abundance ; Oken’s dream seemed to be
coming true ; it seemed as if life were a-making in the still depths.

But when the Challenger expedition went forth, and the bed of
the ocean was explored for the first time carefully, the organism
Bathybius was nowhere to be found. But this was not all ; the
cruellest blow was yet to come. Dr. John Murray saw reason to
suspect that Bathybius was not an organism at all, that it could be
made in a test-tube, and was nothing but a gelatinous form of
sulphate of lime precipitated from the sea water by the action of the
alcohol in the preserving vessels. He renounced Bathybius,
Wyville Thomson acquiesced, Huxley surrendered his organism to
the chemists, and the obscurantists rejoiced exceedingly over the
mare’s nest. Bathybius became famous, it was trotted out to
illustrate the fallibility of science, a useful if it were not a somewhat
superfluous service.

But the non-existence of Bathybius was not proved by the fact
that the Challenger explorers failed to find it, nor was it certain
that Murray’s destructive criticism covered all the facts. Haeckel
clung with characteristic pertinacity to Bathybius, and his con-
stancy has been to some extent justified by the fact that in 1875
Bessels, on a North Polar expedition, dredged from 92 fathoms of
water in Smith’s Sound abundant quantities of a closely -similar
slime. He observed its vital movements, and called it Proto-
Balkybius. It may be that it consists of the broken-off portions
of Foraminifera ; we require to know yet more about it, but I have
said enough to show that it is unfair to stop telling the story with
the words “mare’s nest.” But whethe? there be a Bathybius, a
Proto-Bathybius, or no Bathybius at all, we are as students of science
compelled to confess our complete ignorance as to the origin
of life.

8. Relation to the Earth, — The floor of the sea for a
variable number of miles (not exceeding 300) from the shore is
covered with a heterogeneous deposit, washed in great part from
the nearest continent. In this deposit shells of Foraminifera usually

220 The Study of Animal Life part m

occur, but they become more numerous farther from the land,
where the floor of the sea is often covered with a whitish “ooze,”
most of which consists of Foraminifera which in dying have sunk
from the surface to the bottom. They are forming the chalk of a
possible future, just as many chalk-cliffs and pure limestones repre-
sent the ooze of a distant past. In other regions the hard parts
of Radiolarians or Diatoms (small plants) or Pleropods (minute mol-
luscs) are very abundant. As the Foraminifers have made much
of the chalk, so Radiolarians have formed less important siliceous
deposits, such as the Barbados Earth, from which Ehrenberg
described no fewer than 278 species. At marine depths greater
than 2500 fathoms the Globigerina or other Foraminifer shells are
no longer present, not because there are none at the surface, but
apparently owing to the solution of the shells before they reach
such a vast depth. Here the floor is covered with a very fine
reddish or brownish deposit, often called “red -clay,” a very
heterogeneous deposit of meteoric and volcanic dust and of residues
of surface-animals. Along with this, in some of the very deepest
parts, e.g. of the Central Pacific, there are accumulations of Radio-
larian shells, which do not readily dissolve.1

9. Relation to other Forms of Life.— On the one hand
the Protozoa are devourers of organic debris and the enemies of
many small plants ; on the other hand they form the fundamental
food of higher animals, helping, for instance, to make that thin sea-
soup on which many depend. Moreover, among them there are
many parasites both on vegetable and animal hosts.

10. Relation to Man. — In many indirect ways these firstlings
affe?t human life, nor are there wanting direct points of contact ;
witness a few Protozoa parasites in man, an Amceba, some Gre-
garines, and some Infusorians, which are veiy trivial, however, in
comparison with the numerous plant-parasites — the Bacteria.

Among the earliest human records of Protozoa is the notice
which Herodotus and Strabo lake of the large coin-like Nurnmu-
lites, the “ Pharaoh’s beans ” of popular fancy. But the minute-
ness of most Protozoa kept them out of sight for ages. They were
virtually discovered by Leeuwenhoek (b. 1632) about the middle of
the seventeenth century, and soon afterwards demonstrated by
Hooke to the Royal Sotiety of London, the members of which
signed an affidavit that they had really seen them ! In 1755 Rosel
von Rosenhof discovered the Amceba, or “Proteus animalcule;”
but his discovery was ineffective till Dujardin in 1835 demonstrated
the simplicity of the Foraminifers, and till Von Siebold in 1845

1 For details, see conveniently H. R. Mill’s Realm of Nature (Lond.
1892).

chap, xiv The Simplest Animals 221

showed that Infusoria were single cells comparable to those which
make up a higher animal. For the resemblance between some of
the spirally twisted shells of Foraminifera and those of the
immensely larger Molluscan Ammonites and Nautili led many to
maintain that the Foraminifera were minute predecessors or else
dwindling dwarfs of the Ammonites. So Ehrenberg (1838) figured
the presence of many organs within the Infusorian cell. But as
the microscope was perfected naturalists were soon convinced that
the Protozoa were unit masses of living matter. This is their great
interest to us ; they are, as it were, higher organisms analysed into
their component elements. We see them passing through cycles
of phases, from ciliated to amoeboid, from amoeboid to encysted,
cycles which shed light upon changes both of health and of disease
in higher animals. Again, they seem like ova and spermatozoa
which have never got on any farther.

CHAPTER XV

BACKBONELESS ANIMALS

i. Sponges — 2. Slinging- Animals or Ccelenterata — 3. “ IVonns” —
4. Echinoderms — 5. A rthropods — 6. Molluscs

1. Sponges. — Sponges are many-celled animals without organs,
with little division of labour among their cells. A true “body” is
only beginning among sponges.

Adult sponges are sedentary, and plant -like in their growth.
With the exception of the freshwater sponge ( Spongilla ) they live
in the sea fixed to the rocks, to seaweeds and to animals, or to the
muddy bottom at slight or at great depths. They feed on micro-
scopic organisms and particles, borne in with currents of water
which continually flow through the sponge. The sponge is a
Venice-like city of cells, penetrated by canals, in which incoming
and outflowing currents are kept up by the lashing activity of
internal ciliated cells. These ciliated cells, on which the whole life
of the sponge depends, line the canals, but are especially developed
in little clusters or ciliated chambers. The currents are drawn in
through very small pores all over the surface ; they usually flow out
through much larger crater-like openings.

Sponges feed easily and well, and many of them grow out in
buds and branches. A form which was at first a simple cup may
grow into a broad disc or into a tree-like system. And as trees are
blown out of shape by the wind, so sponges are influenced by the
currents which play around them, as well as by the nature of the
objects on which they are fixed. Like many other passive
organisms, sponges almost always have a well-developed skeleton,
made of flinty needles and threads, of spicules of lime, or of fibres
of horn -like stuff. While sponges do not rise high in organic
rank, they have many internal complications and much beauty.

Sponges may be classified according to their skeleton, as

CHAP. XV

Backboneless A nimals

223

calcareous, flinty, and horny. (a) The calcareous forms with
needles of lime have a world-wide distribution in the sea, from
between tide-marks to depths of 300 to 400 fathoms. They often
retain a cup -like form, but vary greatly in the complexity of their
canals. The sac-like Sycandra (or Grantia) compressa is common
on British shores, (b) The siliceous sponges are more numerous,
diverse, and complicated, and the flinty needles or threads are often
combined with a fibrous “ horny ” skeleton. Venus’-Flower-Basket
(Eupleciella) has a glassy skeleton of great beauty, Mermaids’
Gloves ( Chalina oculatd) with needles of flint and horny fibres is
often thrown up on the beach, the Crumb -of- Bread Sponge
{Halichondria panicea) spreads over the low -tide rocks. Some
have strange habits, witness Clione which bores holes in oyster
shells, or Suberites domuncula which clothes the outside of a whelk
or buckie shell tenanted by a hermit-Crab. Unique in habitat is
the freshwater sponge ( Spongilla ) common in some canals and lakes,
notable for plant-like greenness, and for the vicissitudes of its life-
history. (c) The “horny” sponges which have a fibrous skeleton
but no proper spicules are well represented by the bath-sponges
(Ettspotigia) which thrive well off Mediterranean coasts, where they
are fanned and even bedded out.

Sponges are ancient but unprogressive animals. Their sedentary
habits, from which only the embryos for a short time escape, have
been fatal to further progress. They show tissues as it were in the
making. They are living thickets in which many small animals
play hide-and-seek. Burrowing worms often do them much harm,
but from many enemies they are protected by their skeletons and by
their bad taste.

2. Stinging -Animals or Coelenterata. — It is difficult to
find a convenient name for the jellyfish and zoophytes, sea-anemones
and corals, and many other beautiful animals which are called
Ccelenterates ; but the fact that almost all have poisonous stinging
lassoes in some of their skin-cells suggests that which we now use.

Representatives of the chief divisions may be sometimes found
in a pool by the shore. Ruddy sea-anemones, which some call
sea-roses, nestle in the nooks of the rocks ; floating in the pool and
throbbing gently is a jellyfish left by the tide ; fringing the rocks
are various zoophytes, or, if we construe the name backwards plant-
like animals ; besides these, and hardly visible in the clear water,
are minute translucent bells some of which have a strange relation-
ship with zoophytes ; and there are yet other exquisitely delicate,
slightly iridescent globes — the Ctenophores which move by comb-
like fringes of cilia. But we must search an inland pool to find
one of the very simplest members of this class — the freshwater
Hydra which hangs from the floating duckweed and other plants.

224

PART III

The Study of Animal Life

This Hydra is a tubular animal often about quarter of an inch in
length. One end of the tube is fixed, the other bears the mouth
surrounded by a crown of mobile tentacles. It is so simple that
cut-off fragments if not too minute may grow into complete animals ;
when well fed, the Hydra buds out little polypes like itself, and
these are eventually set free.

If we suppose the budding of Hydra continued a hundred-
fold, till a branched colony of connected individuals is formed,
we have an idea of a hydroid or zoophyte colony. For a zoophyte
is a colony of many hydra-like polypes, which are supported by a
continuous outer framework and share a common life. Numerous
as may be the “persons” on a branched hydroid, all have arisen
from one more or less Hydra-like individual.

Sometimes, however, there is a marked division of labour in such
a colony, as in Hydractinia which has nutritive, reproductive,
sensitive, and perhaps also protective “persons,” — three or four
castes into which the colony is divided. The difference between
nutritive and reproductive members is often well marked, and
this has a special interest in the case of many zoophytes. For
many of these, especially among those known as Tubularians and
Campanularians, have reproductive individuals which are set adrift
as small swimming-bells or medusoids, somewhat like miniature
jellyfish. A fixed plant -like, asexual hydroid colony buds off
free-swimming, sexual medusoids, from the fertilised eggs of which
embryos develop which grow into hydroids. This is known as
alternation of generations, and is a remarkable illustration of
activity and passivity combined in one life-cycle.

But all the miniature jellyfish in the sea are not the liberated
reproductive buds of hydroid colonies. Some which are in
structure exceedingly like the liberated medusoids never have any
connection with a hydroid. Their embryos grow into medusoids
like the parents. Quite distinct from these medusoids, though
sometimes superficially like them, are the true jellyfishes which are
sometimes stranded in great numbers on the beach. These medusa:
belong to a different series, and some of their features link them
rather to the sea-anemones than to the hydroids.

The sea -anemones and the corals are tubular animals whose
mouths are encircled by tentacles, but they are more complicated
internally than the polypes of the Hydra or hydroid type. For the
latter are simple tubes, while the sea-anemones and their relatives
have turned -in lips which make a kind of gullet, and the inside
tube thus formed is connected with the outer wall of the body by
many radiating partitions some idea of which can be gained by
looking at the skeletons or shells of many corals. Related to the
sea-anemones but different in some details, are many colonies, of

CHAP. XV

Backboncless A nitnals

225

which Dead -men’s -fingers ( Alcyonium digitaium) is a common
type. Animals resembling sea -anemones have often much lime
about them, and the same is true of others which resemble
Alcyonium ; in both cases we call these calcareous forms corals.

In this bird’s-eye view of Stinging-animals, we have recognised
the great types, but we have left others of minor importance out of
account, especially certain corals belonging to the hydroid series
and known as Millepores, also the Portuguese Man-of-War and
its relatives (Siphonophora), which are colonies of more or less
medusoid individuals with much division of labour, and lastly the
Ctenophores, such as Beroe and Pletirobrachia, which represent the
climax of activity among Coelenterates.

A brief recapitulation will be useful :

First Series — Hydroid and Medusoid types (Hydrozoa) : —

( 1 ) The freshwater Flydra and a few forms like it.

(2) The hydroids or zoophytes, each of which may be regarded

as a compound much-branched Hydra ; including (a) many
whose reproductive persons are not liberated, especially
Sertularians and Plumularians ; — (6) many whose repro-
ductive persons are liberated as swimming bells or
medusoids, especially Tubularians and Campanularians.

(3) Free medusoids, anatomically like the liberated bells of 2 (6),

but without any connection with zoophytes.

(4) A few colonial medusoids such as the Portuguese Man-of-

War (Physalia).

(5) A few hydroid corals or Millepores.

Second Series — Jellyfish and Sea- Anemone types (Scyphozoa) : —

(1) The true jellyfishes or Medusae, including (a) a form like

Pelagia which isTree-swimming all its life through, (/>) the
common Aurelia whose embryos settle down and become
polypes from which the future free -swimming jellyfishes
are budded off, ( c ) the more or less sedentary jellyfish
known as Lucernarians.

(2) The sea-anemones and their relatives, including (a) sea-

anemones proper (e.g. Actinia) and their related reef-
building coral-colonies {e.g. star-corals Astrcea, brain-coral
Mceandrina) ; and (b) Dead-men’s-fingers {Alcyonium) and
others like it, also with related corals, e.g. the organ-pipe
coral {Tubipora musica) and the “ noble coral ” of com-
merce {Corallium rubrum).

Third Series —

The Ctenophores, which are markedly contrasted with corals,
being free and light and active. Many (e.g. Beroe and
Pleurobrachia) swarm in our seas in summer, iridescent in
daylight, phosphorescent at night. They differ in many
Q

^ ~ ^ The Study of Amuictl Tife part hi

ways from other Coelenterates, thus the characteristic
stinging cells are modified into adhesive cells.

The first and second series, separated by differences of structure
and development, are yet parallel. In both there are polype-types ;
in both medusoid types ; in both there are single individuals and
colonies of individuals; in both there are “corals.” We may
compare a Hydra with a sea -anemone, a medusoid with a jelly-
fish, a hydroid colony with Dead -men’s- fingers, Millepores with

Fig. 42. — The alternation of generations in the common jellyfish Aurelia. i>
the free-swimming embryo ; 2, the embryo settled down ; 3, 4, 5, 6, the de-
veloping asexual stages, or hydra. - tuba: ; 7, 8, the formation of a pile of
individuals by transverse budding ; 9, the liberation of these individuals ;
10, ii, their progress towards the free-swimming sexual medusa form. (From
the Evolution 0/ Sex ; after Haeckel.)

the commoner reef-corals. Moreover, we may compare a medusoid
liberated from a hydroid with Aurelia liberated from its fixed polype-
stage, and permanently-free medusoids with jellyfishes like Pelagia.
These are physiological parallels.

The sedentary polypes are somewhat sluggish, with a tendency
to bud and to form shells or skeletons of some kind. The free-
swimming medusoid types are active, they rarely bud, they do not
form skeletons, but their activity is sometimes expressed in

CHAP. XV

Backboneless A nimals

227

phosphorescence, and their fuller life is associated with the develop-
ment of sense-organs and a more compacted nervous system. In
both sets the food usually consists of small organisms, in securing
which the tentacles and the stinging cells are of use.

All the Stinging-animals are marine except the species of Hydra ,
a minute relative called Microhydra , the hydroid Cordylophora which
occurs in brackish water and in canals, a strange form Polypodium
which is parasitic in its youth on the eggs of the Russian sturgeon
or sterlet, and a freshwater jellyfish (Limnocodium) which was
found in the tanks at Kew. The rest live in the sea. Hydroids
grow on rocks and shells and on the backs of crabs and other
animals which they mask ; sea -anemones live on the shore -rocks
— but not a few are found at considerable depths ; the medusoid
types frequent the opener sea where Siphonophores and Ctenophores
bear them company.

Various kinds of corals should be contrasted. Dead-men’s-
fingers with numerous jagged spicules of lime in its flesh is just
beginning to be coralline. Similar spicules have been fused together
in an external tube in the organ -pipe coral. In the red coral
the calcareous material forms an axis around which the individuals
are clustered. Very different are the reef-building corals, where
the cup in which each individual lived is more or less well marked
according as it has remained distinct or fused with its neighbours,
and where an image of the fleshy partitions of the sea -anemone-
like animal is seen in the radiating septa of lime.

Corals are passive, and like many animals of similar habit have
calcareous shells, but how do they get the carbonate of lime of
which these are composed ? Is that salt — by no means abundant in
sea-water — plentiful near coral-reefs, or is there a double-decomposi-
tion between the abundant calcium sulphate and the coral’s waste-
products, as has been suggested by Irvine and Murray? On what
do the corals feed, for they seem always to be empty ? Do their
bright pigments enable them, as Hickson suggests, to feed like
plants on carbonic acid ?

The struggle for standing-room should also be thought of, and
the throngs of gaily-coloured animals which browse and hide on
the coral banks.

Many of the Stinging-animals have forms and colours which
delight our eyes, and the quaint partnerships between sea-anemones
and crabs are interesting.

But it is through corals that Ccelenterates come into closest touch
with human life. For the stinging of bathers by jellyfish is a
minor matter, and the thousands which are cast upon the beach
are of no use as manure, being little more than animated sea-
water.

228

PART III

The Study of Animal Life

As sponges showed tissues in the making, so among Stinging-
animals organs begin — eyes and ears, nerve-rings, and special
reproductive structures. The zoologist has much to learn in regard
to the alternation of hydroid and medusoid in one life-cycle, the
division of labour in Hydractinia and other colonies, and the
meaning and making of a skeleton. Nor can we forget the long
past in which there were ancient coral reefs, and types of coral
hardly represented now, and strange Graptolites whose nature we
do not yet clearly understand.

We begin the series of many-celled animals with Sponges and
Coelenterates, partly because they are on the whole simplest, but
more precisely because their types of structure are least removed
from that two-layered sac-like embryo or gastrula which recurs in
the life-history of most animals, and which we have much warrant
for regarding as a hint of what the first successful many-celled
animals were like. The Sponges and Coelenterates differ from the
higher animals : (i) In retaining the symmetry of this gastrula, in
being like it radially symmetrical, and in so growing that the axis
extending from the mouth to the opposite pole corresponds to the
long axis of the embryo; (2) in being two -layered animals, for
between the outer skin and the lining of the internal food-cavity
there is only a more or less indefinite jelly instead of a definite
stratum of cells ; (3) in having only one internal cavity, instead of
having, like most other animals, a body-cavity within which a dis-
tinct food-cavity lies.

3. “Worms.” — This title is one of convenience, without
strict justification. For there is no class of “worms,” but an
assemblage of classes which have little in common. “Worm”
is little more than a name for a shape, most of the animals so
called differing from anemones and jellyfish in having head, tail, and
sides. The simplest worms were apparently the first many-
celled animals to move persistently head foremost, thus acquiring
distinct bilateral symmetry, and a definite nervous centre or brain
in that region which had most experience — the head. In our
survey we are helped a little by the fact that many consist of a
series of rings or segments, while others are all one piece or unseg-
mented. It is generally true that the latter are in structure simpler
and more primitive than the former.

1 st Set of Worms. Plathelminth.es or flat worms. 1st
Class. — Turbellaria or Planarians. — These are small worms,
living in the sea or in fresh water, or occasionally in damp earth,
covered externally with cilia, very simple in structure, usually
feeding on minute animals. The genus Planaria, common in fresh
water ; green species of Vortex and Convoluta, which are said by
some to owe their colour to minute partner algae ; Microstoma, which

CHAP. XV

Backboneless Animals

229

by budding forms temporary chains of eight or sixteen individuals
as if suggesting how a ringed worm might arise ; Guttda , with a hint
of internal segmentation ; and two parasitic genera — Graffilla and
Anoplodium — may be mentioned as representatives of this class.
You will find specimens by collecting the waterweeds from a pond
or seaweeds from a shore-pool, and the simplicity of some may be
demonstrated by observing that when they are cut in two each half
lives and grows.

2nd Class. — Trematoda or Flukes. These are parasitic “worms,”
living outside or inside other animals, often flat or leaf- like in
form, provided with adhesive and absorbing suckers. Those which
live as ectoparasites, e.g. on the skin of fishes, have usually a
simple history ; while those which are internal boarders have an
intricate life-cycle, requiring to pass from one host to another of a
different kind if their development is to be fulfilled. Thus the
liver-fluke ( Distomum hepaticum), which causes the disease of liver-
rot in sheep, and sometimes destroys a million in one year in Britain
alone, has an eventful history. From the bile-ducts of the sheep
the embryos pass by the food-canal to the exterior. If they reach a
pool of water they develop, quit their egg-shells, and become for
a few hours free-swimming. They knock against many things, but
when they come in contact with a small water- snail ( Lymtueus
tnincatulus) they fasten to it, bore their way in, and, losing their
locomotor cilia, encyst themselves. They grow and multiply in a
somewhat asexual way. Cells within the body of the encysted
embryo give rise to a second generation quite different in form.
The second generation similarly produces a third, and so on.
Finally, a generation of little tailed flukes arises ; these leave the
water-snail, leave the water too, settle on blades of grass, and lose
their tails. If they be eaten by a sheep they develop into adult
sexual flukes. Others have not less eventful life-cycles, but that of
the liver-fluke is most thoroughly known. If you dissect a frog
you are likely to find Polystomum integerrimum in the lungs or
bladder ; it begins as a parasite of the tadpole, and takes two or
three years to become mature in the frog. Quaint are the little
forms known as Diporpa which fasten on the gills of minnows, and
unite in pairs for life, forming double animals (Diplozoon) ; and
hardly less strange is Gyrodactylus, another parasite on freshwater
fishes, for three generations are often found together, one within
the other. The most formidable fluke-parasite of man is Bilharzia,
or Distomum hamatobium , common in Africa.

3rd Class. Cestoda or Tapeworms. These are all internal
parasites, and, with the exception of one ( Archigetes ), which fulfils
its life in the little river-worm Tubifex , the adults always occur in
the food-canal of backboned animals. Like the flukes, they have

2 3° The Study of Animal Life part hi

adhesive suckers, and sometimes hooks as well ; unlike flukes and
planarians, which have a food-canal, they absorb the juices of their
hosts through their skins, and have no mouth or gut. Like
the endo-parasitic flukes, the tapeworms have (except Archigetes)
intricate life -histories. Both Turbellarians and Trematodes are
small, rarely more than an inch at most in length, but the tape-
worms may measure several feet. In the adult Tania solium,
which is sometimes found in the intestines of man, we see a small
head like that of a pin ; it is fixed by hooks and suckers to the
wall of the food-canal ; it buds off a long chain of “joints,” each
of which is complete in itself. As these joints are pushed by con-
tinued budding farther and farther from the head, they become
larger, and distended with eggs, and even with embryos, for the
bisexual tapeworm seems able to fertilise itself, which is a very rare
thing among animals. The terminal joints of the chain are set free,
one or a few at a time, and they pass down the food-canal to the
exterior. The tiny embryos which they contain when fully ripe
are encased in firm shells. It may be that some of them are eaten
by a pig, the shells are dissolved away in the food-canal, small six-
hooked embryos emerge. These bore their way into the muscles of
the pig and lie dormant, increasing in size however, becoming
little bladders, and forming a tiny head. They are called bladder-
worms, and it was not till about the middle of this century that they
were recognised as the young stages of the tapeworm. For if the
diseased pig be killed and its flesh eaten (especially if half-cooked)
by man, then each bladder-worm may become an adult sexual tape-
worm. The bladder part is of no importance, but the head fixes
itself and buds off a chain. For many others the story is similar ;
the bladder-worm of the ox becomes another tapeworm ( Tania
saginata) in man ; the bladder-worm of the pike or turbot becomes
another ( Bothriocephalus latus) ; the bladder-worm of the rabbit
becomes one of the tapeworms of the dog, that of the mouse passes
to the cat, and so on. A bladder-worm which forms many heads
destroys the brain of sheep, etc., and has its tapeworm stage (Tania
canurus ) in dog or wolf. Another huge bladder-worm, which has also
many heads, and sometimes kills men, has also its tapeworm stage
(Tania echinococcus') in the dog. But enough of these vicious
cycles.

2nd Set of Worms. Ribbon Worms or Nemerteans—

4th Class, Nemertea. — In pleasing contrast to the flukes and tape-
worms, the Nemerteans are free -living “worms.” They are
mostly marine, often brightly coloured, almost always elongated,
always covered with cilia. There is a distinct food-canal with
a posterior opening, a blood-vascular system for the first time,
a well-developed nervous system, a remarkable protrusible “pro-

chap, xv Backboneless Animals 231

boscis ” lying in a sheath along the back, a pair of enigmatical
ciliated pits on the head. The sexes are almost always separate.
Almost allNemerteans are carnivorous, but two or three haunt other
animals in a manner which leads one to suspect some parasitism ;
thus Malacobdella lives within the shells of bivalve molluscs. We
find many of them under loose stones by the sea-shore ; one
beautiful form, Linens marinus, sometimes measures over twelve
feet in length. Some, such as Cerebratulus, break very readily into
parts, even on slight provocation, and these parts are said to be
able to regrow the whole. To speculative zoologists, the Nemer-
teans are of great interest on account of the vertebrate affinities
which some of their structures suggest. Thus the sheath of the
“proboscis” has been compared with the vertebrate notochord
(the structure which precedes and is replaced by a backbone), and
the two ciliated head-pits with gill-slits.

3rd Set of Worms. Nemathelminthes or Round-
Worms — 5th Class, Nematoda or Thread - Worms. — The
“worms” of this class are usually long and cylindrical, and the
small ones are like threads. The skin is firm, the body is
muscular ; in most a simple food-canal extends from end to end of
the body-cavity now for the first time distinct ; the sexes are
separate. Many of the Nematodes live in damp earth and in
rottenness ; many are, during part of their life, parasitic in animals
or plants. We have already noticed how long some of them —
“ paste -eels,” “ vinegar -eels,” etc. — may lie in a dried-up state
without dying. The life-histories are often full of vicissitudes ; thus
the mildew- worm ( Tylenchus tritici) passes from the earth into the
ears of wheat, and many others make a similar change ; the female
of Sphczrularia bombi migrates from damp earth into humble-bees,
and there produces young which find their way out ; others, e.g.
some of the thread-worms found in man ( Oxyuris , Trichocephalus),
pass from water into their hosts ; others are transferred from one
host to another ; as in the case of the Trichina with which pigs
are infected by eating rats, and men infected by eating diseased
pigs, or the small Filaria sanguinis hominis, sometimes found in
the blood of man, which seems to pass its youth in a mosquito.
Somewhat different from the other Nematodes are those of which
the horse-hair worm Gordius is a type. They are sometimes found
inside animals (water-insects, molluscs, fish, frog, etc.), at other
times they appear in great numbers in the pools, being, according
to popular superstition, vivified horse-hairs.

6th Class, Acanthocephala. — Including one peculiar genus of
parasites ( Echinorhynchus ).

4th Series of Worms. The Annelids or Ringed Worms
— 7th Class, Chaetopoda or Bristle -footed “worms.” — In the

232 The Study of Animal Life part hi

earthworms ( Lumbricus , etc.), in the freshwater worms (Atais,
Tubifex, etc.), in the lobworms ( Arenicola piscatoruni), and in the
sea-worms ( Nereis , Aphrodite , etc.), all of which are ranked as
Chmtopods, the body is divided into a series of similar rings or
segments, and there are always some, and often very .many, bristles
on the outer surface. The segments are not mere external rings,
but divisions of the body often partially partitioned off internally,
and there is usually some repetition of internal organs. Thus in
each segment there are' often two little kidney-tubes or nephridia,

•while reproductive organs may occur in segment after segment.
Moreover, there are often two feet on each ring. The nervous
system consists of a dorsal brain and of a double nerve-cord lying
along the ventral surface. The nerve-cord has in each segment a
pair of nerve-centres or ganglia, and divides in the head region to
form a ring round the gullet united with the brain above. The »

existence of nerve-centres for each segment makes each ring to some
extent independent, but the brain rules all. This type of nervous
system represents a great step of progress ; it is very different from
that of Stinging-animals, which lies diffusely in the skin or forms
a ring around the circumference ; different from that of the lower
“worms,” where the nerve-cords from the brain usually run along
the sides of the body ; different from that of molluscs, where the
nerve-centres are fewer and tend to be concentrated in the head ;
different finally from the central nervous system of backboned animals,
for that is wholly dorsal. But the type characteristic of ringed
“ worms”— a dorsal brain and a ventral chain of ganglia — is also
characteristic of crustaceans, insects, and related forms.

Of bristle-footed “worms,” there are two great sets, the earth-
worms and the sea-worms. The former, including the common
soil-makers and a few giants, such as the Tasmanian Megascolides,
sometimes about six feet long, have bristles but no feet ; sense-
organs, feelers, and breathing organs are undeveloped as one would
expect in subterranean animals. The sea-worms, on the other
hand, have usually stump-like bristly feet, and eyes and tentacles
and gills, but there is much difference between those which swim
freely in the sea (e.g. Alciope and Tomopteris and some Nereids)
and the lobworms which burrow and make countless castings upon
the flat sandy shores, or those which inhabit tubes of lime or
sandy particles (e.g. Serpula , Spirorbis, and Lanice or Terebella
conchilegci). The earthworms with comparatively few bristles
(Oligochseta) are bisexual, while almost all the marine worms with
many bristles (Polychseta) have separate sexes. Moreover, those of
the first series usually lay their eggs in cocoons, within which the
embryos develop without any metamorphosis, while the sea-worms,
though they sometimes form cocoons, have free-swimming larva:

CHAP. XV

Backboneless A nimals

233

usually very different from the adults— little barrel-shaped or pear-
shaped ciliated creatures known as Trochospheres.

Some of the Chxtopods multiply not only sexually, but asexually
by dividing into two or by giving off buds from various parts of
their body. Strange branching growths, which eventually separate
into individuals, are well illustrated by the freshwater Nats, and

Fig. 43. — A budding marine worm ( Syllis ramosa). From Evolution of Sex ;
after M'Intosh’s Challenger Report.)

still better by a marine worm, Syllis ramosa , which almost forms
a network.

Many sea-worms have much beauty, which some of their names,
such as Nereis, Aphrodite, Alciope, suggest, and which is said to
have induced a specialist to call his seven daughters after them.

Along with the Chsetopods, we include some other forms too
unfamiliar to find more than mention here, the Myzostomata which
form gall-like growths on the feather-stars which they infest, the
strange Bonellia in which the microscopic male lives as a parasite
within the female, and some very simple forms which are sometimes
called Archi-Annelids.

234

I’ ART III

The Study of Animal Life

8th Class, Hirudinea or Discophora or Leeches. — These are
blood-sucking animals, which often cling for a long time to their
victims. They live in salt and in fresh water, and sometimes on
land. The body is elastic and ringed, but the external markings
do not correspond to the internal segments. There are no legs,
but the mouth is suctorial, and there is another adhesive sucker
posteriorly. The body-cavity is almost obliterated by a growth
of spongy tissue, whereas that of Chaetopods is roomy. Leeches
are hermaphrodite, and lay their eggs in cocoons, within which
the young develop without metamorphosis.

The medicinal leeches (Hirudo medicinalis) live in slow streams
and marshes, creeping about with their suckers or sometimes
swimming lithely, preying upon fishes and amphibians, and both
larger and smaller animals. They fix themselves firmly, bite with
their three semicircular saw-like tooth-plates, and gorge themselves
with blood. When they get an opportunity they make the most
of it, filling the many pockets of their food-canal. The blood is
kept from coagulating by means of a secretion, and on its store the
leech may live for many months.

The horse-leech (Hcemopis sanguisuga) is common in Britain
and elsewhere. The voracious Aulastoma is rather carnivorous
than parasitic. The land -leeches (e.g. dice mad ipsa ceylonica ),
though small and thin, are very troublesome, sucking the blood of
man and beast. Among the others are the eight-eyed Nephelis of
our ponds, the little Clepsine which sometimes is found with its young
attached to it, the warty marine Pontobdella which fastens on rays,
Piscicola on perch and carp, Branchetlion with numerous lateral
leaflets of skin, and the largest leech — the South American Macro-
bdella valdiviana which is said to attain a length of over two
feet.

Possibly related to the Annelid series are two other
classes —

9th Class — Chsetognatha, including two genera of small arrow-
like marine “ worms,” Sagitta and Spadella.

10th Class — Rotifera, “ wheel animalcules,” abundant and
exquisitely beautiful animals inhabiting fresh and salt
water and damp moss. The head-region bears a ciliated
structure, whose activity produces the impression of a
swiftly rotating wheel. Many of them seem to be
entirely parthenogenetic. Some can survive being made
as dry as dust.

Fifth set of Worms — a doubtful combination including —

1 ith Class — Sipunculoidea, “ spoon-worms ” living in the sea,
freely or in tubes, e.g. Sipunculus.

1 2th Class — Phoronidea, including one genus, Pkoronis.

CHAP. XV

Backboneless Animals

235

13th Class — Polyzoa or Bryozoa, with one exception forming
colonies by buckling, in fresh water or in the sea, e.g. the
common sea-mats or horn-wracks ( Flustra ).

14th Class — Brachiopoda or Lamp-shells, a class of marine
shelled animals once much richer in members, now
decadent. They have a superficial, but only a superficial,
resemblance to Molluscs.

I have not catalogued all these classes of “ worms ” without a
purpose. To ignore their diversity would have lent a false simplicity
to our survey. If you gain only this idea that there is a great
variety — a mob — of worm-like animals, which zoologists have not yet
reduced to order, you have gained a true idea. The “ worms” lie
as it were in a central pool among backboneless animals, from which
have flowed many streams of progressive life. They have affinities
with Echinoderms, with Insects, with Molluscs, with Vertebrates.

To practical people the study of “ worms ” has no little interest.
The work of earthworms is pre-eminently important ; the sea-
worms are often used as bait ; the leech was once the physician’s
constant companion ; numerous parasitic worms injure man, his
domesticated stock, and the crops of his fields.

4. Echinodermata. — In contrast to the “Worms,” the series
including starfishes, brittle -stars, feather -stars, sea-urchins, and
sea-cucumbers, is well defined.

The Echinodermata are often ranked next the stinging animals,
mainly because many of the adults have a radiate symmetry, as
jellyfishes and sea -anemones have. But radiate symmetry is a
superficial character, perhaps originally due to a sedentary habit of
life in which all sides of the animal were equally affected. More-
over, the larvae of Echinoderms are bilaterally symmetrical, that is to
say, they are divisible into halves along a median plane. We
place Echinoderms after and not before “worms,” because the
simplest worm-like animals are much simpler, much nearer the
hypothetical gastrula-like ancestor than are any Echinoderms, and
also because it is likely that Echinoderms originated from some
worm type or other.

Haeckel used to hold a theory of the starfish which was in some
ways suggestive. You know the five-rayed appearance of the
animal like a conventional star j you have perhaps watched it
moving slowly in a deep rock pool by the shore ; you have
perhaps discovered that it will surrender one of its arms when you
try to capture it. Now Haeckel compared the starfish to a colony
of five worms united in the centre. Each “arm” or “ray” is
complete in itself. Each has a nerve -cord along the ventral
surface, a little eye at the tip, prolongations of the food-canal, blood-
vessels, and reproductive organs. Each is anatomically comparable

236 The Study of Animal L,ife part iii

to a worm. Furthermore, when an arm is separated, it may bud
out other four arms and thus recreate an entire starfish. Each arm
has therefore some physiological independence.

But there is no likelihood that a starfish arose as a colony of
worms ; the facts of development do not corroborate the sug-
gestion.

Of Echinoderms there are seven classes, two of winch are
wholly extinct. These — the Cystoids and Blastoids — are of great
interest because of their relationship with the feather -stars or
Crinoids, which stand somewhat apart from the other four extant
classes. The Cystoids are more primitive than the Crinoids, and
connect them with the starfishes or Asteroids. The Asteroids are
nearly related to the brittle-stars or Ophiuroids, and they are also
linked to the sea-urchins or Echinoids. These in turn are the
nearest allies of the Holothuroids or sea-cucumbers.

The Echinoderms are all marine. The sea-urchins and Holo-
thurians are mud-cleansing scavengers ; the Holothurians and
Crinoids feed for the most part on small organisms, though the
former are sometimes mud-eaters ; the starfishes are more emphatic-
ally carnivorous, and often engulf small molluscs.

Among starfishes, sea-urchins, and sea- cucumbers, we find
occasional cases of prolonged external connection between the
mothers and the young.

The Echinoderms are sluggish animals, though many brittle-
stars are lithe gymnasts, and though the commonest Crinoids
(Comatulids, such as the rosy feather-star, Antedoti rosacea), differ
from their stalked relatives and adolescent stages in being to some
extent swimmers. Perhaps the sluggishness is expressed in the
abundance of lime in the skin and other parts ; for, as the name
suggests, the Echinoderms are thorny-skinned, being usually pro-
tected by calcareous plates and spines. The sea-cucumbers are the
most muscular and the least limy, indeed in some almost the only
calcareous parts are a few anchors and plates scattered in the skin.

Another frequent characteristic is the radial symmetry, but we
remember that the larvae are bilateral.

Very important is the development of a peculiar system of
canals and suctorial “tube-feet” — the water-vascular system. By
means of the tube-feet the starfishes and sea-urchins move, in the
others their chief use seems to be in connection with respiration,
and it is likely that in some at least they also help in excretion.

Another characteristic of the Echinoderms is the strangeness of
the larval forms. For not only are they very different from the
parents, and very remarkable in form, but in no case do they
grow directly into the adult. The development is “indirect,”
the larva does not become the adult ; the foundations of the

Fig. 44. — A Holothurian ( Cucumaria crocea) with Its young attached to its skin.
(F’rom Evolution 0/ Sex ; after Challenger Narrative.)

238 The Study of Animal Life part iii

adult are laid anew within the body of the larva, which is absorbed
or partly rejected.

Not only the starfishes but also the brittle -stars and the
feather-stars often surrender their arms when captured, or even
when slightly irritated, and a part or a remnant can in favourable
conditions regrow the whole. The Holothurian Synapta breaks
readily into pieces, and others contract themselves so forcibly that
the internal organs are extruded.

The relations of Echinoderms to other animals are many. A
little fish, Fierasfer , goes in and out of Holothurians ; the de-
generate Myzostomata form galls on the arms of Crinoids ; star-
fishes are deadly enemies of oysters. On the other hand, some
sea-snails and fishes prey upon Echinoderms in spite of their
grittiness. Except that the unlaid eggs of some sea-urchins are
edible, and that some sea-cucumbers are considered delicacies, the
Echinoderms hardly come into direct contact with human life.

5. Arthropods. — Lobsters, centipedes, insects, spiders, agree
with the Annelid “worms” in being built up of a series of rings
or segments. Some or all of these segments bear limbs, and these
limbs are jointed, as the term Arthropod implies. The skin
forms an external sheath or cuticle of a stuff called chitin, and
this firm sheath helps us to understand how the limbs became
well-jointed. The chitin seems in some way antagonistic to the
occurrence of ciliated cells, for none seem to occur in this large
series unless it be in the strange type Peripatus. The chitin has
also to do with the moulting or cuticle-casting which is common
in the series, for-the cuticle is generally rigid and does not expand
as the body grows, hence it has to be cast and a new one made.
Finally, Arthropods have a nervous system like that of Annelids — -
a double dorsal brain connected by a ring round the gullet with a
double chain of ganglia along the ventral surface. But the life of
most Arthropods is more highly pitched than that of Annelids.
The sense-organs are more highly developed, brains are larger and
more complex, the ganglia of the ventral chain tend to become
concentrated ; there is division of labour among the appendages ;
there are new internal organs such as a heart ; the whole body
is better knit together. A crayfish may part with his claw and
grow another in its place, but the animal will not survive being cut
in two as some kinds of Annelids do.

The series includes at least five classes : —

Crustacea, almost all aquatic, and breathing by gills.

Protracheata, represented by the genus Peripalus.

Myriapoda, centipedes and millipedes.

Insecta, more or less aerial.

Arachnida, spiders, scorpions, mites, etc.

CHAP. XV

Backbonelcss Ani Dials

I

239

The members of the last four classes usually breathe by means
of air-tubes or tracheae, which penetrate into every part of the body,
or in the case of spiders and scorpions, by “ lung-books,” which
seem like concentrated and plaited tracheae. The King-crab
( Limulus ), which is very often ranked along with Arachnids, is
aquatic, and breathes by peculiar “gill-books.”

(a) Crustacea. — Except the wood-lice, which live under bark
and stones, the land-crabs which visit the sea only at the breeding

Fig. 45. — Nauplius of Sacculina. (From Fritz Muller.)

time, and some shore-forms which live in great part above the tide-
mark, the Crustaceans are aquatic animals, and usually breathe by
gills. Each segment of the body usually bears a pair of append-
ages, and each appendage is typically double. Among these ap-
pendages much division of labour is often exhibited, some being
sensory, others masticatory, others locomotor. In the higher forms
the life-history is often long and circuitous, with a succession of
larval stages.

The lower Crustaceans are grouped together as Entomostraca.
They are often small and simple in structure ; the number of

I

24° The Study of Animal Life tart iii

segments and appendages varies greatly. The little larva which
hatches from the egg is usually a “ Nauplius ” — an unsegmented
creature with only three pairs of appendages and a median eye.

The brine -shrimps ( Artemia ), the related genus Branchipus ,
the old-fashioned freshwater A pus ; the common water-flea Daphnia
and its relatives, like Leptodora and Aloina, are united in the order
of Pbyllopods.

The small “water-fleas” of which Cypris is a very common
representative, and which are very abundant in sea and lake, form
the order of Ostracods.

Another “ water-flea ” Cyclops and many more or less degenerate
“ fish-lice ” and other ectoparasites (e.g. Chondracanthus, Caligus,
Lenina) are known as Copepods. The free-swimming forms often
occur in great swarms and are devoured by fishes.

The acorn -shells ( Balamis ) crusting the rocks, the barnacles
( Lepas ) pendent from floating “timber,” and the degenerate Sacculina
under the tail of crabs, represent the order Cirripedia.

The higher Crustaceans are grouped together as Malacostraca.
The body usually consists of nineteen segments, five forming the
head, eight the thorax, six the abdomen or tail. In most cases the
larva is hatched at a higher level of structure than the Nauplius
represents, but the shrimp-like Penaus begins life as a Nauplius
while the crab is hatched as a Zoea, the lobster in a yet higher
form, and the crayfish as a miniature adult.

Simplest of these higher Crustaceans, in some ways like a
survivor of their hypothetical ancestors, is the marine genus Nebalia,
but we are more familiar with the Amphipods (e.g. Gammants)
which jerk themselves along sideways or shelter under stones both
in fresh and salt water. The wood-louse Oniscus has counterparts
( Asellus , Idotea ) on the shore, and several remarkable parasitic
relatives. Among the highest forms are the long -tailed lobsters
( Homarus , Palinurus ), and crayfishes ( Astacus ), and shrimps
( Crangon ), and prawns ( Palcemon , Pandalus ) ; the soft -tailed
hermit crabs (Pagurus) ; and the short tailed crabs (e.g. Caticer,
Care inns, Dromia).

{b) Protracheata. — Peripatus. This remarkable genus, repre-

Fig. 46. — Peripatus. (From Chambers’s EncycJof. ; after Moseley.)

sented by about a dozen widely-distributed species, seems to be a
survivor of the ancestral insects. Worm-like or caterpillar-like in

CHAP. XV

Backboneless Animals

241

appearance, with a soft and beautiful skin, with unjointed legs, with
the halves of the ventral nerve-cord far apart, and with many other
remarkable features, it has for us this special interest that it
possesses the air- tubes characteristic of insects and also little
kidney-tubes similar to these of Annelids.

(e) Myriapoda. — Centipedes and Millipedes. — These animals
have very uniform bodies, there is little division of labour among the
numerous appendages. The head is distinct, and bears besides the
pair of antennae (which Peripattis and Insects also have) two paiis
of jaws. The Centipedes are flattened, carnivorous, and poisonous ;
the Millipedes are cylindrical, vegetarian, and innocuous ; moreover,
they have two pairs of legs to most of their segments.

Fig. 47. — Winged male and wingless female of Pneumora, a kind of
grasshopper. (From Darwin.)

(,/) Insecta. — Insects are the birds of the backboneless series.
Like birds they are on an average active, most have the power of
flight, many are gaily coloured, sense-organs and brains are often
highly developed.

Contrasted with Peripatus and Myriapods, they have a more
compact body, with fewer but more efficient limbs. They are
Arthropods, which are usually winged in adult life, breathe air
by means of tracheae, and have frequently a metamorphosis in their
life-history. To this definition must be added the anatomical facts
that the adult body is divided into three regions, ( 1 ) a head with
three pairs of mouth -appendages ( = legs) and a pair of sensitive
outgrowths (antennae or feelers) in front of the mouth, (2) a thorax
with three pairs of walking legs, and usually two pairs of wings,
and (3) an abdomen without appendages, unless occasional stings,
egg-laying organs, etc., be remnants of these.

R

242

PART Ml

The Study of Animal Life

' The wings are veiy characteristic. They are flattened sacs of
skin, into which air-tubes, blood-spaces, and nerves extend. It is
possible that they had originally a respiratory, rather than a
locomotor function, and that increased activity induced by bettered
respiration made them into flying wings.

The breathing is effected by means of the numerous air-tubes
or tracheae which open externally on the sides and send branches
to every corner of the body. As the air is thus taken to all
the tissues, the blood-vascular system has little definiteness, though
there is (as in other Arthropods) a dorsal contractile heart. The
larvae of some insects, e.g. dragonflies, mayflies, etc., live in
the water, and the tracheae cannot open to the exterior (else the
creature would drown), but they are sometimes spread out on
wing-like flaps of skin (“tracheal gills”), or arranged around the
terminal portion of the food-canal in which currents of water are
kept up.

The student should learn something about the different mouth-
organs of insects and the kinds of food which they eat ; about the
various modes of locomotion, for insects “ walk, run, and jump with
the quadrupeds, fly with the birds, glide with the serpents, and
swim with the fish ; ” about the bright colours of many, and the
development of their senses.

In the simplest insects — the old-fashioned wingless Thysanura
and Collembola — the young creature which escapes from the egg-
shell is a miniature adult. There is no metamorphosis. So with
cockroaches and locusts, lice and bugs ; except that the young are
small, have undeveloped reproductive organs, and have no wings,
they are like the parents, and all the more when the parents (e.g.
lice) also are wingless.

In cicadas there is a slight but instructive difference between
larvae and adults. The full-grown insects live among herbage, the
young live in the ground, and the anterior legs of the larva; are
adapted for burrowing. Moreover, the larval life ends in a sleep
from which an adult awakes. But much more marked is the differ-
ence between the aquatic lame of mayflies and dragonflies and the
aerial adults, in which we have an instance of more thorough though
still incomplete metamorphosis.

Different, however, is the life of all higher insects — butterflies
and beetles, flies and bees. From the egg-shell there emerges a
larva (maggot, grub, or caterpillar), w'hich often lives an active
voracious life, growing much, and moulting often. Rich in stores
of fatty food, it falls into a longer quiescence than that associated
with previous moults and becomes a pupa, nymph, or chrysalis.
In this stage, often within the shelter of a silken cocoon, great
transformations occur ; the body is undone and rebuilt, wings bud

chai*. xv Backboneless Animals 243

out, the appendages of the adult are formed, and out of the pupal
husk there emerges an imago, an insect fully formed.

(e) Arachnida. — Spiders, Scorpions, Mites, etc. — This class is
unsatisfactorily large and heterogeneous. In many the body is
divided into two regions, the head and breast (cephalothorax), with
two pairs of mouth parts and four pairs of walking legs, the
abdomen with no appendages. Respiration may be effected by
the skin in some mites, by tracheae in other mites, by tracheae plus
“ lung-books ” in many spiders, by “ lung-books ” alone in other
spiders, by “gill-books” in the divergent king-crab.

The scorpions with a poisoning weapon at the tip of the tail,
the little book-scorpions ( Chelifer ), the long-legged harvest-men
(e.g. Phalangium) ; the spiders proper — spinners, nest -makers,
hunters ; the mites ; the strange parasite (Pentastomum) in the
dog’s nose ; the quaint king-crab ( Limulus ) — last of a lost race,
with which the ancient Trilobites and Eurypterids were connected ;
all these are usually ranked as Arachnids !

6. Molluscs. — It seems strange that animals, the majority of
which are provided with hard shells of lime, should be called
mollusca ; for that term first used by Linnaeus is a Latinised version
of the Greek malakia , which means soft. Aristotle applied it
originally to the cuttlefish, which are practically without shells, so
that its first use was natural enough, but the subsequent history of
the word has been strange.

Cockle, mussel, clam, and oyster; snail and slug, whelk and lim-
pet ; octopus, squid, and pearly nautilus ; what common character-
istics have they ? Most of them have a bias towards sluggishness,
and on the shields of lime which most of them bear, do we not read
the legend, “ castles of indolence ” ? But this sluggishness is only
an average character, and the shell often thins away. The scallop
{Pec ten) and the swimming Lima are active compared with the
oyster, and they have thinner shells ; the snails which creep slowly
between tides or on the floor of the sea are heavily weighted, while
the sea-butterflies (Pteropods) have light shells, and most cuttlefish
have none at all.

The shell is very distinctive, but we are not able to state
definitely how it is formed or what it means. In most of the
embryo molluscs which have been studied there is a little pit or
“shell-gland” in which a shell begins to be formed, but the shell
of the adult is in all cases made by a single or double fold of skin
known as the “ mantle.” In some cases where the shell seems to
be absent, e.g. in some slugs, a degenerate remnant is still to be found
beneath the skin, while in other cases {e.g. most cuttlefish) its
absence is to be explained as a loss, since related ancestral species
possess it. There are, however, two or three primitive forms

244

PART III

The Study of Animal Life

( Chaloderma, Neomenia ) where an incipient shell is represented
only by a. few spicules or plates of lime.

The shell is made by the folded skin or “mantle” ; it consists
for the most part of carbonate of lime along with a complex organic
substance called conchiolin ; it shows three layers, of which the
outermost is somewhat soft and without lime, while the innermost
shines with mother-of-pearl iridescence. The whole product is a
cuticle— something formed from the skin ; its varied colours and
forms are beautiful ; it is a protective shield ; but there are many

Fig. 48. — The common octopus. (From Chambers’s Encyclofi. ; after Brehm.)

questions about shells which we cannot answer. Where does the
carbonate of lime come from, since that salt is often far from
abundant in the water in which most molluscs live? Have they
the power of changing the abundant sulphate of lime in sea-water
into carbonate of lime, perhaps by an interaction with waste products
excreted from the skin ? Is the shell an expression of the constitu-
tional sluggishness of the animal since it seems on the whole to be
most massive in the most sluggish, least so in the most active forms ?

Most molluscs are marine, on the shore, in the open sea, in the
great depths ; there are also many freshwater forms, e.g. the
mussels Anodon and Unio, and the snails, Lymnaus, Planorbis,

CHAP. XV

Backboneless Animals

245

and Paludina ; the terrestrial snails and slugs are legion. Among
those of the shore the naked Nudibranchs are often in colour and
form protectively adapted to their surroundings; those of the open
sea (Ileteropods, Pteropods, and many cuttlefish) are active and
carnivorous, with light shells or none ; in the dark depths many
are blind or in other ways rudimentary, but food seems to be so
abundant that there is almost no need to struggle for it.

As to diet, there are three kinds of eaters — carnivores, such as
the active swimmers we have mentioned, besides the whelks and
many other burglars who bore through their neighbours’ shells, and
the Testacella slugs ; vegetarians, like the periwinkle, the snail, and
most slugs ; and thirdly, almost all the bivalves, which feed on
microscopic plants and animals, and on organic debris wafted to
the mouth by the lashing of the cilia on the gills and lips. In this
connection it is important to notice that all molluscs except bivalves
have in their mouths a rasping ribbon or toothed tongue ( radula ,
odontophore ) by which they grate, file, or bore with marked effect.
Of parasites there are few, but one Gasteropod, Entoconcha
mirabilis , which lives inside the Holothurian Synapta, is very
remarkable in its degeneration. It starts in life as a vigorous
embryo like that of most marine snails, it becomes a mere sac of
reproductive organs and elements.

In structure, molluscs differ remarkably from the arthropods
and higher “worms” in the absence of segments and serial
appendages. They are not divided into rings, and they have no
legs.

To begin with, they were doubtless (bilaterally) symmetrical
animals, and this symmetry is retained in primitive forms like the
eight-shelled Chiton and in the bivalves. But most of the snails
are twisted and lop-sided, they cannot be symmetrically halved.
For this asymmetry the strange dorsal hump formed by the viscera,
and the tendency that the single shell would have to fall to one side,
are sometimes blamed. That this lop-sidedness is not necessarily
a defect, but rather the reverse, is evident from the success not
only of the snail tribe but of many other asymmetrical animals.

The skin has a remarkable fold (double in the bivalves) known
as the “mantle,” the importance of which in making the shell we
have already recognised. Another very characteristic structure is
the so-called “ foot,” a muscular protrusion of the ventral surface,
an organ used in creeping and swimming, leaping and boring, but
almost absent in the sedentary oysters.

We rank the molluscs high among backboneless animals, partly
because of the nervous system, which here as elsewhere is a
dominating characteristic. There are fewer nerve centres than in
most Arthropods or in higher “ worms,” but this is in most cases

246 The Study of Animal Life part hi

a sign of concentration. There is a ( cerebral ) pair with nerves
which supply the head region, another {pleural) pair with nerves to
the sides and viscera, a third {pedal) pair whose nerves govern the
foot, and often other accessory centres of which the most important
are visceral. In the somewhat primitive eight-shelled Chiton and its
neighbours, the nervous system is the most readily harmonised with
that of other Invertebrates ; in bivalves the three pairs of centres
are far apart ; in most snails and in cuttlefish the three are con-
centrated in the head-regions, and it is those forms with concentrated
ganglia which show some signs of cleverness and emotion.

Life-History. — Most molluscs pass through two larval stages
before they acquire their characteristic adult appearance. The
first is interesting because it is virtually the same as the young
stage of many “worms.” It is a barrel -shaped or pear-like
embryo with a ring of locomotor cilia in front of the mouth, and is
known as a Trochosphere.

After a while this changes into a more characteristic form called
the Veliger. It bears on its head a ciliated cushion or velum often
produced into lobes ; the body has a ventral “ foot” and a dorsal
“shell-gland.” In aquatic Gasteropods the visceral hump begins
to appear at this stage.

The eggs of cuttlefish differ from those of other molluscs in their
rich supply of yolk, which serves for a prolonged period as capital
for the young, and the two larval stages noticed above are skipped
over. There are other interesting modifications in the life-history
of terrestrial and freshwater forms, witness the little larvae of the
freshwater mussel which are kept within the gills of the mother till
the approach of some sticklebacks or other fish, to which the
liberated young then fix themselves.

History. — The shells of molluscs are well preserved in the rocks,
and palaeontologists have been very successful in tracing long series.

The chief types are all represented in the Cambrian strata — a
fact which forcibly suggests the immensity of yet earlier ages.
They are abundant from the Silurian onwards. The snails have
gone on increasing, and are now more abundant than ever ; the
bivalves cannot be said to have diminished, but the Cephalo-
pod tribe has dwindled. Of the Nautiloid type of Cephalopods,
of which there are crowds of fossil forms, only the pearly Nautilus
now survives, and though there are many kinds of naked cuttle-
fish in our seas there are ten times as many shelled ancestors
in the rocks. The geological record confirms what we should
otherwise expect, that the lung-breathing snails and the freshwater
bivalves were somewhat late in appearing.

Prof. Ray Lankester has reconstructed an ideal ancestor which
combines the various molluscan characteristics in a satisfactory

CHAP. XV

Backboneless A nimals

247

fashion, and may be something like the original mollusc. Whence
that original sprang is uncertain, but the common occurrence of the
trochosphere larva and some of the characters of the primitive
Gasteropods (Neomenia, Chcetoderma , Chiton ) suggest the origin
of molluscs from some “ worm ” type or other. We can be sure of
this, however, that the series must have divided at a very early
epoch into two sets, the sluggish, sedentary, headless bivalves on
the one hand, and the more active and aggressive snails and cuttle-
fish on the other.

Relation to Man. — Irresistibly we think first of oysters, which
Huxley describes as “gustatory flashes of summer lightning,”
and over which neolithic man smacked his lips. But many others,
cuttlefish, ear-shells ( Haliotis ), mussels ( Mytihis edulis), peri-
winkles (Littorina littorea ), cockles ( Cardinal corda/um), etc. etc., are
used as food, and many more as bait. In ancient days, as even
now, the shells of many were used for ornaments, instruments,
lamps, vessels, coins, etc. ; the inner layer of the shell furnishes
mother-of-pearl ; concretions around irritating particles become
pearls in the pearl-oyster ( Margaritana ) and in a few others ; the
Tyrian purple was a secretion of the whelk Purpura and the
related Murex ; and the attaching byssus threads of the large bivalve
Pinna may be woven like silk.

On the other hand, a few cuttlefish are large enough to be
somewhat dangerous ;• the bivalve Teredo boring into ship-bottoms
and piers is a formidable pest, baulked, however, by the pre-
valent use of metal sheathing ; the snails and slugs are even more
voracious than the birds which decimate them.

Conchology was for a while a craze, rare shells have changed
hands at the cost of hundreds of pounds, such is the human “ mania
of owming things.” But the shells are often fascinating in their
beauty, and poetic fancy has played lovingly with such as the
Nautilus.

CHAPTER XVI

BACKBONED ANIMALS

i. Balanoglossus — 2. Tunicates — 3. The Lancelet — 4. Round-
Mouths or Cyclostomata — 5. Fishes — 6. Amphibians —
7. Reptiles — 8. Birds — 9. Mammals

According to Aristotle, fishes and all higher animals were “ blood-
containing,” and thus distinguished from the lower animals, which
he regarded as “ bloodless.” He was mistaken as to the absence of
blood in lower animals, for in most it is present, but the line which
he drew between higher and lower animals has been recognised in
all subsequent classifications. Fishes, amphibians, reptiles, birds,
and mammals differ markedly from molluscs, insects, crustaceans,
“worms,” and yet simpler animals. The former are backboned
(Vertebrate), the latter backboneless (Invertebrate).

It is necessary to make the contrast more precise, [a) Many
Invertebrates have a well-developed nerve-cord, but this lies on the
ventral surface of the body, and is connected anteriorly, by a ring
round the gullet, with a dorsal brain in the head. In Verte-
brates the whole of the central nervous system lies along the dorsal

Fig. 49. — Diagram of “ Ideal Vertebrate,” showing the segments of the body,
the spinal cord, the notochord, the gill-clefts, the ventral heart. (After Haeckel.)

surface of the body, forming the brain and spinal cord. These
arise by the infolding of a skin groove on the dorsal surface of the
embryo, (b) Underneath the nerve-cord in the Vertebrate embryo

CHAP. XVI

Backboned Animals

249

is a supporting rod or notochord. It arises along the roof of the
food-canal, and serves as a supporting axis to the body. It per-
sists in some of the lowest Vertebrates {e.g. the lancelct) ; it persists
in part in some fishes ; but in most Vertebrates it is replaced by a
new growth — the backbone — which ensheaths and constricts it.
(c) From the anterior region of the food-canal in fishes and tadpoles
slits, bordered by gills, open to the exterior. Through the slits
water flows, washing the outsides of blood-vessels and aerating the
blood. These slits or clefts are represented in the young of all
Vertebrate animals, but in reptiles, birds, and mammals they are
transitory and never used. Amphibians are the highest animals in
which they are used for breathing, and even then they may be
entirely replaced by lungs in adult life. They are evident in tad-
poles, they have disappeared in frogs, (d) Many an Invertebrate
has a well-developed heart, but this always lies on the dorsal
surface of the body, while that of fish or frog, bird or man, lies
ventrally. (e) It is characteristic of the eye of backboned animals
that the greater part of it arises as an outgrowth from the brain,
while that of backboneless animals is directly derived from the skin.
But this difference is less striking when we remember that it is from
an infolding of skin that the brain of a backboned animal arises.

But while the characteristics of backboned animals can now be
stated wdth a precision greater than that of sixty years ago, it is no
longer possible to draw with a firm hand the dividing line between
backboned and backboneless. Thus fishes are not the simplest
Vertebrates ; the lamprey and the glutinous hag belong to a more
primitive type, and are called fishes only by courtesy ; simpler still
is the lancelet; the Tunicates hesitate on the border line, being
tadpole-like in their youth, but mostly degenerate when adults ;
and the worm-like Balanoglossns is perhaps to be ranked as an
incipient Vertebrate. The extension of knowledge and the appli-
cation of evolutionary conceptions obliterate the ancient landmarks
of more rigid but less natural classification.

1. Balanoglossus. — Balanoglossus is a worm - like animal,
represented by some half - dozen species, which eat their way

Fig. 50. — Balanoglossus, showing proboscis, collar, and gill -slits.

through sandy mud off" the coasts of the Channel Islands, Brittany,
Chesapeake Bay, and other regions. Its body is ciliated and divided
into distinct regions — a large “proboscis” in front of the mouth, a

PART III

250 The Study of Animal Life

firm collar behind the mouth, a part with numerous gill-slits behind
the collar, and finally a soft coiled portion with the intestine and
reproductive organs. The size varies from about an inch to 6
inches, the colours are bright, the odour is peculiar ; the sexes are
separate. But Ba/anoglossus is most remarkable in having a dorsal
supporting rod (like a notochord) in the “proboscis” region, a
dorsal nerve-cord running along the back and especially developed
in the collar, and a series of gill-clefts on the anterior part of the
food-canal. It is therefore difficult to exclude Ba/anoglossus from

Fig. 51.— Cephalodiscus, a single individual, isolated from a colony. It is much
magnified. (From Chambers’s Encyclop. ; after Challenger Report, by
MTntosh and Harmer.)

the Vertebrate series, and it is likely that the same must be said
of another strange animal, Cephalodiscus, discovered by the Chal-
lenger explorers.

2. Tunicates. — Hanging to the pennon-like seaweeds which
fringe the rocky shore and are rarely uncovered by the tide, large
sea-squirts sometimes live. They are shaped like double-mouthed
wine - bags, 2 or 3 inches in length, and water is always being
drawn in at one aperture and expelled at the other. Usually they
live in clusters, and their life is very passive. We call them sea-
squirts because water may spout forth when w-e squeeze their

Backboned Animals

CHAP. XVI

25 1

bodies, while the title Tunicate refers to a characteristic cloak or
tunic which envelops the whole animal.

There is not much to suggest backbonedness about these Tuni-
cates, and till 1866 no one dreamt that they could be included in
the Vertebrate series. But then the Russian naturalist Kowalevsky
discovered their life-history. The young forms are free-swimming
creatures like miniature tadpoles, with a dorsal nerve-cord,. a sup-
porting rod in the tail region, gill-slits opening from the food canal,
a little- eye arising as an outgrowth of the brain, and a ventral
heart.

There are only two or three genera of Tunicates, especially one
called Appetidicularia, in which these Vertebrate characteristics are
retained throughout life. The others lose them more or less com-
pletely. The young Tunicates are active, perhaps too active, for a
short time ; then they settle down as if fatigued, fix themselves by
their heads, absorb their tails, 'and become deformed. The nervous
system is reduced to a single ganglion between the two apertures ;
the original gill-slits are replaced by a great number of a different
character ; the eye is lost. From the skin of the degenerate animal
the external tunic is exuded. It is a cuticle, and consists, in part
at least, of cellulose, the substance which forms the cell-walls of
plants. Thus this characteristically vegetable substance occurs
almost uniquely in the most passive part of a very passive animal.
The sea-squirt’s metamorphosis is one of the most signal instances
of degeneration ; the larva has a higher structure than the adult ;
the young Tunicate is a Vertebrate, the adult is a nondescript. We
cannot tell how this fate has befallen the majority, nor why a few
are free-swimmers, nor why Appetidicularia retains throughout life
the Vertebrate characteristics of its youth. Do the majority over-
exert themselves when they are “ tadpoles,” or are they constitu-
tionally doomed to become sedentary ?

Tunicates are hermaphrodite — a very rare condition among Ver-
tebrates ; some of them exhibit “ alternation of generations,” as the
poet Chamisso first observed ; asexual multiplication by budding is
very common, and not only clusters but more or less intimate
colonies are thus formed.

Tunicates live in all seas, mostly near the coast from low water
to 20 fathoms, and usually fixed to stones and rocks, shells and sea-
weed. A few are free-swimming, such as the fire-flame ( Pyrosoma ),
a unified colony of tubular form, sometimes 2 or 3 feet in length,
and brilliantly phosphorescent. Very beautiful are the swimming
chains of the genus Salpa, whose structure and life-history alike are
complicated.

Tunicates feed on the animalcules borne in by the water
currents, and some of them must feed well, so rapidly do they grow

25 2 The Study of Animal Life part m

and multiply. Unpleasant to taste, they are left in peace, though
a crab sometimes cuts a tunic off as a cloak for himself.

3- Tile Lancelet. — The lancelet ( A mphioxus) is a simple
Vertebrate, far below the structural rank of fishes. It is only
about 2 inches in length, and, as both English and Greek names
suggest, it is pointed at both ends. On the sandy coasts of warm
and temperate seas it is widely distributed.

From tip to tail of the translucent body runs a supporting noto-
chord ; above this is a spinal cord, with hardly a hint of brain.
The pharynx bears a hundred or so gill-slits, which in the adult
are covered over by folds of skin, so that the water which enters
by the mouth finds its way out by a single posterior aperture.
Although Amphioxus has no skull, nor jaws, nor brain, nor limbs,
it deserves its position near the base of the Vertebrate series. The
sexes are separate, and the eggs are fertilised outside of the body.
The development of the embryo has been very carefully studied,
and is for a time very like that of Tunicates.

4- Round-Mouths or Cyclostomata.— The hag -fishes and
the lampreys and a few allied genera must be excluded from the
class of fishes. They are survivors of a more primitive race.
They are jawless, limbless, scaleless, and therefore not fishes.

The lampreys ( Petromyzon ) live in rivers and estuaries, and also
in the wider sea. They are eel-like, slimy animals. The skeleton
is gristly ; the simple brain is imperfectly roofed ; the single nostril
does not open into the mouth ; the rounded mouth has homy teeth
on the lips and on the piston-like tongue ; there are seven pairs of
gill-pouches which open directly to the exterior and internally into
a tube lying beneath and communicating with the adult gullet ; the
young are blind and otherwise different from the parents, and may
remain so for two or three years.

Though lampreys eat worms and other small fry, and even dead
animals, they fix themselves aggressively to fishes, rasping holes
in the skin, and sucking the flesh and juices. They also cling to
stones, as the name Petromyzon suggests.

Some species drag stones into a kind of nest. They spawn in
spring, usually far up rivers, for at least some of the marine
lampreys leave the sea at the time of breeding. The young are in
many ways different from the parents, and that of the small river
lampern {Petromyzon branchialis ) used to be regarded as a distinct
animal — Ammoccetes. The metamorphosis was discovered two
hundred years ago by Baldner, a Strasburg fisherman, but was
overlooked till the strange story was worked out in 1856 by
August Miiller. Country boys often call the young “nine-eyes, ’
miscounting the gill apertures, and the Germans also speak of
veun-augen.

CHAP. XVI

Backboned Animals

253

The sea lamprey (P. marinus) may measure three feet ; the
river lamprey ( /’. Jluviatilis) about two feet ; the small lampern or
stone -grig (/’. branchialis or plancri] about a foot. The flesh is
well known to be palatable.

The glutinous hag ( Myxine glutinosa) is an eel -like animal,
about a foot in length, of a livid flesh colour. It is common at
considerable depths (40 to 300 fathoms) off the coasts of Britain
and Norway, and, when not feeding, lies buried in the mud with
only its nostril protruded. Like the lamprey, it has a smooth
slimy skin, a gristly skeleton, a round suctorial mouth with teeth.
The single nostril communicates with the food-canal at the back
of the mouth, and serves for the inflowing of water ; the six gill-
pockets on each side open directly into the gullet, but each has an
excurrent tube, and the six tubes of each side open at a common
aperture. The animal lives away from the light, and its eyes are
rudimentary, hidden beneath skin and muscles. The skin exudes
so much slime that the ancients spoke of the hag “ turning water
into glue.”

In several ways the hag is strange. Thus J. T. Cunningham
discovered that it is hermaphrodite, first producing male elements,
and afterwards eggs, and Nansen has corroborated this. The eggs
are large and oval, each enclosed in a “horny” shell with knotted
threads at each end, by which a number are entangled together.
How they develop is unknown. The hags devour the bait and
even the fish from the fisherman’s lines, and some say that they bore
their way into living fishes such as cod.

5- Fishes. — Fishes are in the water as birds in the air, — swift,
buoyant, and graceful. They are the first backboned animals with
jaws, while scales, paired fins, and gills are their most character-
istic structures. The scales may be hard or soft, scattered or
closely fitting, and are often very beautiful in form and colour.
The paired fins are limbs, as yet without digits, varying much' in
size and position, and helping the fish to direct its course. The
gills are outgrowths of skin with a plaited surface, on which the
branching blood-vessels are washed by the water. They are the
breathing organs of all fishes, but in the double-breathing mud-
fishes ( Dipnoi ) the swim-bladder has come to serve as a lung, and
there are hints of this in a few others.

There are at least four orders of fishes : —

(1) The cartilaginous fishes (Elasmobranchs or Selachians) are for
the most part quite gristly, except in teeth and scales. Among
them are the flattened skates and rays with enormous fore-fins,
while the sharks and dogfish are shaped like most other fishes.
Their pedigree goes back as far as the Silurian rocks, in which
remains of shark-like forms are found. A Japanese shark ( Chla -

254

PART III

The Study of Animal Life

mydoselachus) is said to.be very closely allied to types which occur
in the. Old Red Sandstone. Allied to the Elasmobranchs, but
sometimes kept in a separate division, are two genera, the Chimara
or King-of-the-Herrings, and Callorhynchus, its relative in Southern
Seas.

(2) The Ganoid fishes are almost, if not quite, as ancient as the

Elasmobranchs, but their golden age, long since past, was in Devonian
and Carboniferous ages. There are only some seven different kinds
now alive. Two of these are the sturgeons ( Acipenser ) and the
bony pike ( Lepidosleus ). The latter has a bony skeleton ; the

sturgeon is in part gristly. An armature of hard scales is very
characteristic of this decadent order.

(3) In Permian times, when Reptiles were beginning, a third
type of fish appeared, of which the Queensland mud-fish (Ceratodus)
seems to be a direct descendant. In this type the air-bladder is
used as a lung, thus suggesting the transition from Fishes to Am-
phibians. Perhaps this order was always small in numbers ; now-
adays at least there are only two genera — Ceratodus, from the
fresh water of Queensland, and Protopterus, from west and tropical
Africa ; while another form, sometimes called a different genus
( Lepidosireii ), is recorded from the Amazons. Double-breathers cfr
Dipnoi we call them, for they do not depend wholly upon gills, but
come to the surface and gulp air into their air-bladder. Mud-
fishes they are well named, for as the waters dry up they retire into
the mud, forming for themselves a sort of nest, within which they
lie dormant.

(4) In the Chalk period the characteristically modern fishes
(Teleosteans), with completely bony skeletons, began. Herring
and salmon, cod and pike, eel and minnow, and most of the com-
monest fishes belong to this order. Heavy ironclads yield to swift
gunboats, and the lithe Teleosteans have succeeded better than the
armoured Ganoids.

The wedge-like form of most fishes is well adapted for rapid
swimming. Most flat fish, whether flattened from above down-
wards like the gristly skate, or from side to side like the flounders
and plaice, live at the bottom ; those of eel - like shape usually
wallow in the sand or mud ; the quaint globe-fish float passively.
The chief organ of locomotion is the tail ; the paired fins help to
raise or depress the fish, and serve as guiding oars. In the climb-
ing perch they are used in scrambling ; in the flying fish they are
sometimes moved during the long swooping leaps. In eels and
pipe-fish they are absent ; in the Dipnoi they have a remarkable
median axis. The unpaired fins on the back and tail and under
surface are fringes of skin supported by rays.

Fishes are often resplendent in colours, which are partly due to

chap, xv Backboned Animals 255

pigments, partly to silvery waste-products in the cells of the outer
skin, and partly to the physical structure of the scales. Some-
times the males are much brighter than the females, and grow
brilliant at the breeding season. In some cases the colours har-
monise with surrounding hues of sand and gravel, coral and sea-
weed ; while the plaice and some others have the power of rapidly
changing their tints.

Fishes feed on all sorts of things. Some are carnivorous, others

Fia. 52. — The gemmeous dragonet {Callionymus lyra), the male above,
the female beneath. (From Darwin.)

vegetarian, others swallow the mud. By most of them worms,
crustaceans, insect-larvae, molluscs, and smaller fishes are greedily
eaten. Strange are some of large appetite [e.g. Chiasmodon niger),
who manage to get outside fishes larger than their own normal
size 1

Of their mental life little is known. Yet the cunning of trout,
the carefulness with which the mother salmon selects a spawning-
ground, the way the archer-fish ( Toxoles ) spits upon insects, the
nest-making and courtship of the stickleback and others, the pug-
nacity of many, show that the brain of the fish is by no means asleep.

256

PART III

The Study of Animal Life

The males are often different from the females — smaller, brighter,
and less numerous. In some cases they court their mates, and
fight with their rivals. Most of the females lay eggs, but a few
bony fishes and many sharks bring forth living young. In two
sharks there is a prophecy of that connection between mother and
offspring which is characteristic of mammals. The fish’s egg is
usually a small thing, but those of Elasmobranchs are large, being
rich in yolk and often surrounded by a mermaid’s purse. This
egg-case has long tendril-like prolongations at the corners, these
twine automatically around seaweed, and the embryos may be
rocked by the waves until the time of hatching. When the egg is
enclosed in a sheath, or when the young are hatched within the
body of the mother, fertilisation must take place internally, but in
most cases the male accompanies the female as she spawns, and
with his milt fertilises the eggs in the water or on the gravelly
spawning-ground. As love for offspring varies inversely with their
number, there is little parental care among the prolific fishes.

Most fishes live either wholly in the sea or wholly in fresh
water, but some are indifferent, and pass, at spawning time espe-
cially, from one to the other. A few, such as the climbing
perch, venture ashore, while the mud -fishes and a few others
” can survive drought for a season. In caves several blind fishes
live, and species of Fierasfer find more or less habitual lodging
inside sea-cucumbers and some other animals.

The fishes which live in deep water are interesting in many
ways. Gunther has shown that from 80 to 200 fathoms the eyes
are rather larger than usual, as if to make the most of the dim
light. Beyond 200 fathoms “small-eyed fishes as well as large-eyed
occur, the former having their want of vision compensated for by
tentacular organs of touch, whilst the latter have no such accessory
organs,” and can see only by the fitful light of phosphorescence.
“ In the greatest depths blind fishes occur, with rudimentary eyes,
and without special organs of touch. ” The phosphorescence is pro-
duced by numerous marine animals and by the fishes themselves.

6. Amphibians. — The Amphibians which now live are neither
numerous nor large. Giant Amphibians or Labyrinthodonts began
to appear in the Carboniferous period, but most of the modern
frogs and toads, newts and salamanders, are relatively pigmies.

Young Amphibians always breathe by gills, as Fishes do, and in
some cases these gills persist in adult life. But whether they do
or not, the full-grown Amphibians have lungs and use them. The
skin is characteristically soft, naked, and clammy. Amphibians
are the first Vertebrates with hands and feet, with fingers and toes.
Unpaired fringes are sometimes present on the back and tail as in
Fishes, but are never supported by fin-rays.

CHAP. XVI

Backboned Animals

257

The class includes four orders, of which the Labyrinthodonts
are wholly extinct, the other three being represented by tail-less
frogs and toads (Anura), by newts and salamanders (Urodela) with
distinct tails, and by a few of worm-like form and burrowing
habit, e.g. Ccecilia. Some, the last for example, are terrestrial, but
usually live in damp places ; most pass their youth at least in fresh
water ; none can endure saltness, and they are therefore absent from
almost all oceanic islands. The common British newts ( Triton and
Lissotriton ), and the often brightly-coloured salamanders (Sala-
mandra ) have in adult life no trace of gills ; the rice-eel ( Amphiuma )
and the genus Menopoma lose their gills, but persistent clefts indi-
cate their position ; the blanched blind Proteus from caves and the
genus Rfenobranchus keep their gills throughout life. Tire remark-
able Axolotl from North American lakes occurs in two forms, both
of which may bear young ; the one form (Axolotl) has persistent
gills, the other form ( Amblystoma ) loses them, and the change
from the Axolotl to the Amblystoma is in part associated with the
passage from the water to the swampy shore. A large fossil dis-
covered by Scheuchzer in the beginning of the eighteenth century
was quaintly regarded as a fossil man and as a testimony of the
deluge. But Cuvier showed that Scheuchzer’s Homo diluvii testis
was but a large newt.

The common frogs (Rana), the Surinam toad ( Pipa ), the
common toads ( Bufo ), and the tree-frogs (fly la) illustrate the tail-
less order Anura. In none of them is there in adult life any trace
of gills.

The worm-like, limbless, burrowing Amphibians (Gymnophiona)
must not be confused with the blind- or slow-worms, which are
lizards. There are only very few genera, Siphonops, Rhinatrema ,
Efncrium, Ccecilia. The newly-born Ccecilia has external gills,
but these are soon lost. The eyes are covered with skin, but are
well developed.

The race of Amphibians began in the Carboniferous ages.
Most of the Labyrinthodonts which flourished then and in the two
succeeding periods were newt-like in form, but some were serpen-
tine. They seem to have been armoured, and were sometimes
large.

Amphibians are naturally sluggish. For long periods they can
fast and lie dormant ; they can survive being frozen quite stiff,
and though tales of toads within stones are mostly due to mistakes
or fancies, there are some authentic cases of prolonged imprison-
ment.

Few are found far from water, and the gilled condition of
the young is skipped over only in a few cases. In the black
salamander (Salamandra atra) of the Alps, which lives where

S

258

PART III

The Study of Animal Life

pools are scarce, the young, after living and breathing for a time
within the mother, are born as lung-breathers ; also in some
species of tree-frogs ( Hylodes ), which live in situations where water
is scarce, the gilled stage is omitted.

The development of the common frog should be studied bj
every student of natural history. The eggs are fertilised as they
are being laid. The division of the ovum can be readily observed.
In its early stages the tadpole is fish-like, with a lamprey-like

Fig. S3- -The life-history of the Frog.

mouth. External gills are replaced by an internal set, and as
metamorphosis is accomplished these disappear and the lungs
become active. The larva feeds first on its own yolk, then on
freshwater plants, then on small animals or even on its own
relatives ; then it fasts, absorbing its tail, and finally it becomes an
insect-catching frog.

The food of adult Amphibians usually consists of insects, slugs,
and worms ; most of the larvae are for a time vegetarian. Though
Amphibians often live alone, crowds are often found together at the
breeding season. Then the sluggish life wakes up, as the croak-
ings of frogs remind us. Quaint are many of their reproductive
habits, to some of which allusion has already been made. Such

CHAP. XVI

Backboned. A nimals

259

animals as the Surinam toad [Pi pa americana) and the Obstetric
frog ( Alytes obstetricans) suggest that the Amphibians make ex-
periments in eugenics.

7. Reptiles.— Fishes and Amphibians are closely allied ; so
Reptiles are linked to Birds, and more remotely to Mammals also.
Those three highest classes — Reptiles, Birds, and Mammals — are
very different from one another, but they have certain characters in
common. Most of them have passed from the water to dry land ;
none of them ever breathe by gills ; all of them have two embryonic
birth-robes— amnion and allantois — which are of great importance
in early life. Compared with the other Vertebrates, the brains are
more complex, the circulation is more perfect, the whole life has a
higher pitch. As symbols of mammal, bird, and reptile, take the
characteristic coverings of the skin — hair, feathers, and scales.
Hair typifies strength and perhaps also gentleness ; feathers suggest
swift flight, the beauty which wins love, and the down which lines
the warm nest ; scales speak of armour and cold-blooded stealth.

But we need not depreciate reptiles, nor deny the justice of that
insight which has found in them the fittest emblems of the omni-
potence of the earth. If Athene of the air possesses the birds,
surely the power of the dust is in the grovelling snakes. Few
colour arrangements are more beautiful than those which adorn the
lithe lizards. The tortoise is an example of passive energy, self-
contained strength, and all but impenetrable armature. The
crocodiles more than the others recall the strong ferocity of the
ancient extinct dragons. Nor should we judge reptiles exclusively
by their living representatives, any more than we should judge
the Romans by those of the decadent Empire. It is interesting to
remember the long-tailed toothed Archaopteiyx , the predecessor of
modern birds, just as it is to recall the giant sloths which pre-
ceded the modern Edentate mammals ; but it is essential to include
in our appreciation of Reptiles the giant dragons of their golden
age. Most modern forms are pigmies beside an Ichthyosaurus 25
feet long, a Megalosattrus of 30, a Titanosaurus of 60, or an
Atlantosaurus of 100, all fairly broad in proportion. We have still
pythons and crocodiles and other reptiles of huge size, and we do
not deny Grant Allen’s remark that a good blubbery “ right whale ”
could give points to any deinosaur that ever moved upon Oolitic
continents, but the fact remains that in far back times (Triassic,
Jurassic, and Cretaceous) reptiles had a golden age with a pre-
dominance of forms larger than any living members of the class.
Besides size, however, the ancient saurians had another virtue,
apparently possessed by both small and great — they were pro-
gressive. lor, with toothed birds on the one hand and flying or
flopping reptiles on the other, it seems probable that birds had

260

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The Study of Animal Life

their origin from feverish saurians which acquired the power of
flight, and it is also possible that some, perhaps pathological,
mother reptile, overflowing in the milk of animal kindness, and
retaining her young for a long time within her womb, was the fore-
runner of the mammalian race.

While there are many orders of extinct reptiles — Ichthyosaurs,
Plesiosaurs, Deinosaurs, Pterosaurs, and other saurians not yet
classified with certainty — the living forms belong to four sets — the
lizards, the snakes, the tortoises, and the crocodiles — to which a
fifth order should perhaps be added for the New Zealand “lizard”
Hatteria or Sphenodon , which is in several respects a living fossil.

The Lizards (Lacertilia). — The lizards form a central order of
Reptiles, but the members are a motley crowd, varied in detailed
structure and habit. Usually active in their movements, though
fond, too, of lying passive in the sunshine, they are often very
beautiful in form and colour, and not uncommonly change their
tints in sympathetic response to their surroundings. Most lay eggs,
but in some, e.g. the common British lizard ( Lacerta or Zootoca
vivipara), and the slow-worm, the young are hatched within the
mother.

Among the remarkable forms are the Geckos, which with
plaited adhesive feet can climb up smooth walls ; the large Monitors
( Varanus ), which may attain a length of 6 feet, and prey upon
small mammals, birds, frogs, fishes, and eggs ; the poisonous
Mexican lizard ( Heloderma horridum), with large venom -glands
and somewhat fang-like teeth; the worm-like, limbless Amphis-
bcena ; the likewise snake-like slow-worm (Angitis fragilis), which
well illustrates the tendency lizards have to break in the spasms of
capture ; the large Iguanas, which frequent tropical American
forests, and feed on leaves and fruit ; the sluggish and spiny
“Horned Toad” (Phrynosomd) ; the Agamas of the Old World
comparable to the Iguanas of the New ; the Flying Dragon (Draco
volans), which, with skin outstretched on extended ribs, swoops
from tree to tree; the Australian frilled lizards (Chlamydosaurus)
and the quaint thorny Moloch ; the single marine lizard (Oreo-
cephalus or A mblyrhynchus cristatus) from the Galapagos ; and the
divergent Chamaeleons, flushing with changeful colour.

The New Zealand Hatteria or Sphenodoil is quite unique, and
seems to be the sole survivor of an extinct order — Rhynchocephalia.
It was in it first of all that the pineal body — an upgrowth from the
mid-brain of backboned animals — was seen to be a degenerate
upward-looking eye.

Snakes or Serpents (Ophidia). — These much modified
reptiles mostly cleave to the earth, though there are among them
clever climbers, swift swimmers, and powerful burrowers. Though

CHAP. XVI

Backboned Animals

261

Fig. 54.— The wall-lizard ( Lncerta muralis), three differently coloured and marked varieties of the same species.

ffVmrvilnrl from ^

262

PART III

The Study of Animal Life

they are all limbless, unless we credit the little hind ciaws of some
boas and pythons with the title of legs, they flow like swift living
streams along the ground, using ribs and scales instead of their lost
appendages, pushing themselves forward with jerks so rapid that
the movement seems continuous. Without something on which to
raise themselves they must remain at least half prostrate, but in the
forest or on rough ground there are no lither gymnasts. Their
united eyelids give them an unlimited power of staring, and, accord-
ing to uncritical observers, of fascination ; yet most of them seem
to see dimly and hear faintly, trusting mainly for guidance to the
touch of their restless protrusible tongue and to their sense of
smell. Their only language is a hiss or a whine. Most of them
have an annual period of torpor, and all periodically cast off their
scales in a normally continuous slough, which they turn outside-in
as they crawl out. Almost all lay eggs, but in a few cases (e.g.
the adder) the young are hatched within the mothers, and this
mode of birth may be induced by artificial conditions. Think not
meanly of the serpent, “it is the very omnipotence of the earth.
That rivulet of smooth silver — how does it flow, think you? It
literally rows on the earth with every scale for an oar ; it bites the
dust with the ridges of its body. Watch it when it moves slowly —
a wave, but without wind ! a current, but with no fall ! all the
body moving at the same instant, yet some of it to one side, some
to another, or some forward, and the rest of the coil backwards ;
but all with the same calm will and equal way— no contraction, no
extension ; one soundless, causeless, march of sequent rings, and
spectral procession of spotted dust, with dissolution in its fangs,
dislocation in its coils. Startle it — the winding stream will become
a twisted arrow ; the wave of poisoned life will lash through the
grass like a cast lance. It scarcely breathes with its one lung (the
other shrivelled and abortive) ; it is passive to the sun and shade,
and cold or hot like a stone ; yet ‘ it can outclimb the monkey,
outswim the fish, outleap the zebra, outwrestle the athlete, and
crush the tiger.’ It is a Divine hieroglyph of the demoniac power
of the earth— of the entire earthly nature. As the bird is the
clothed power of the air, so this is the clothed power of the dust ;
as the bird is the symbol of the spirit of life, so this of the grasp and
sting of death.” 1

This well-known and eloquent passage is not perfectly true, —
thus the serpent breathes not scarcely but strongly with its one
lung, — but, while you may correct and complete it as you will, I am
sure that you will find here more insight into the nature of serpents
than in pages of anatomical description.

1 Ruskin’s Queen of the Air.

CHAP. XVI

Backboned Animals

263

A few snakes have mouths which do not distend, skull bones
which are slightly movable, teeth in one jaw (upper or lower)
only, and rudiments of hind legs. These are included in the
genera Typhlops and Anomalepsis , and are small simple ophidians.

Many are likewise non-venomous snakes, but with wider gape
and more mobile skull bones, and with simple teeth on both jaws.
Some are very large and have great powers of strangling. Such
are the Pythons, the Boa, and the Anaconda. To these our grass
snake ( Tropidonotus ua(rix) is allied.

Many poisonous snakes have large permanently erect grooved fangs
in the upper jaw, and a salivary gland whose secretion is venomous.
Such are the cobra ( Naja tripudians ), the Egyptian asp ( Naja haje ),
the coral snakes ( Elaps ), and the sea snakes ( Hydrophis ).

Other poisonous snakes have perforated fang teeth, which can
be raised and depressed. Such are the vipers ( Vipera), the British
adder ( Pelias berus), the copperhead ( Ancistrodon contortrix), the
rattlesnakes ( Crotalus).

Tortoises and Turtles (Chelonia). — Boxed in by a bony
shield above and by a bony shield below, and often with partially
retractile head and tail and legs, the Chelonians are thoroughly
armoured. On the average the pitch of their life is low, but their
tenacity of life is great. Slow in growth, slow in movement, slow
even in reproduction are many of them, and they can endure long
fasting. It is said that a tortoise walked at least 200 yards, twenty-
four hours after it was decapitated, while it is well known that the
heart of a tortoise will beat for two or three days after it has been
isolated from the animal. In connection with their sluggishness it
is significant that the ribs which help to some extent in the respira-
tory movements of higher animals are soldered into the dorsal
shield, thus sluggish respiration may be in part the cause, as it is
in part the result, of constitutional passivity. All the Chelonians
lay eggs in nests scooped in the earth or sand.

The marine turtles (e.g. Sphargis, Chelone), the estuarine soft-
shelled turtles (e.g. Aspidonectes), the freshwater turtles {e.g.
Emys), and the snapping turtle ( Chelydra ) are more active than the
land tortoises, such as the European Testudo grceca, often kept as
a pet. The tortoise of the Galapagos Islands ( Testudo elephant opus),
the river tortoise ( Podocnemys expatisa) of the Amazon, the bearded
South American turtle ( Chelys malamata), and the green turtle
( Chelone mydas ) attain a large size, sometimes measuring about
3 feet in length.

Crocodilians (Crocodilia). — Crocodiles, alligators, and gavials
seem in our present perspective very much alike — strong, large,
heavily armoured reptiles, at home in tropical rivers, but clumsy
and stiff-necked on land, feeding on fishes and small mammals,

264 The Study of Animal Life part iii

growing slowly and without that definite limit which punctuates
the life -history of most animals, attaining, moreover, a great
age, freed after youth is past from the attacks of almost every
foe but man. The teeth are firmly implanted in sockets ; the
limbs and tail are suited for swimming, and also for crawling ; the
heart is more highly developed than in other reptiles, having four
instead of three chambers. The animals lie in wait for victims,
and usually drown them, being themselves able to breathe while
the mouth is full of water, if only the nostrils be kept above the
surface.

In many ways Reptiles touch human life, the poisonous snakes
are very fatal, especially in India ; crocodilians are sometimes
destructive ; turtles afford food and “ tortoise shell lizards are
delightfully beautiful.

8. Birds. — What mammals are to the earth, and fishes to the
sea, birds are to the air. Has anything truer ever been said of

Fig. 55.—' The Collocalia, which from the secreted juice of its salivary glands
builds the edible-bird’s-nest. (Adapted from Brehm.)

them than this sentence from Ruskin’s Queen of llie Air ? “The
bird is little more than a drift of the air brought into form by
plumes ; the air is in all its quills, it breathes through its whole
fratae and flesh, and glows with air in its flying, like a blown

chap, xvi Backboned Animals 265

flame : it rests upon the air, subdues it, surpasses it, outraces it ; — •
is the air, conscious of itself, conquering itself, ruling itself.”

Birds represent among animals the climax of activity, an index to
which may be found in their high temperature, from 2°-i4° Fahren-
heit higher than that of mammals. In many other ways they rank
high, for whether we consider the muscles which move the wings
in flight, the skeleton which so marvellously combines strength
with lightness, the breathing powers perfected and economised by a
set of balloons around the lungs, or the heart which drives and
receives the warm blood, we recognise that birds share with
mammals the position of the highest animals. And while it is true
that the brains of birds are not wrinkled with thought like
those of mammals, and that the close connection between mother
and offspring characteristic of most mammals is absent in birds, it
may be urged by those who know their joyousness that birds feel
more if they think less, while the patience and solicitude con-
nected with nest-making and brooding testify to the strength of
their parental love. Usually living in varied and beautiful sur-
roundings, birds have keen eyes and sharp ears, tutored to a sense
of beauty, as we may surely conclude from their cradles and love
songs. They love much and joyously, and live a life remarkably
free and restless, qualities symbolised by the voice of the air in
their throat, and by the sunshine of their plumes. There is more
than zoological truth in saying that in the bird “ the breath or spirit
is more full than in any other creature, and the earth power least,”
or in thinking of birds as the purest embodiments of Athene of
the air.

But just as there are among mammals feverish bats with the power
of true flight, and whales somewhat fish-like, so there are excep-
tional birds, runners like the ostriches and cassowaries, swimmers
like the penguins, criminals too like the cuckoos and cow-birds in
which the maternal instincts are strangely perverted. As we go
back into the past, strange forms are discovered, with teeth, long
tails, and other characteristics which link the birds of the air to the
grovelling reptiles of the earth. Even to-day there lives a
“ reptilian-bird ” — Opisthocomus — which has retained more than
any other indisputable affinities with the reptiles. Professor W. K.
Parker, one of the profoundest of all students of birds, described
this form in one of his last papers, and there used a comparison
which helps us to appreciate birds. They are among backboned
animals what insects are among the backboneless — winged pos-
sessors of the air, and just as many insects pass through a cater-
pillar and chrysalis stage before reaching the acme of their life as a
flying imago, so do the young birds within the veil of the egg-
shell pass through somewhat fish-like and somewhat reptile-like

266

The Study of Animal Life

1'AK.T HI

and less adorned female of Spatliura— a genus
irds. (From Darwin, after Brehm.)

chap, xvi Backboned Animals

267

stages before they attain to the possession of wings and the enjoy-
ment of freedom.

The great majority of birds are fliers, and possess a keeled
breast-bone, to which are fixed the muscles used in flight. To
this keel or carina they owe their name Carinatte. The flying
host includes the gulls and grebes, the plovers and cranes, the
ducks and geese, the storks and herons, the pelicans and cormo-
rants, the partridges and pheasants, the sand grouse, the pigeons,
the birds of prey, the parrots, the pies, and about 6000 Passerine or
sparrow-like birds, including thrushes and warblers, wrens and
swallows, finches and crows, starlings and birds of paradise. To
these orders we have to add Opisthocomus, from which it is perhaps
easier to pass to some of the keeled fossil birds, some of which
possessed teeth.

Distinct from the keeled fliers, both ancient and modern,
are the running-birds, which
are incapable of flight, and
therefore possess a flat raft-
like breast bone, to which
they owe their title Ratitce.

Nowadays these are few in
number, the Ostrich and the
Rhea, the Cassowary and
Emu, and the small Kiwi.

Beside these must be ranked
the giant Moa of New Zea-
land, not long extinct, and
the more ancient, not less
gigantic Aipyoniis of Mada-
gascar, while farther back
still, from the Chalk strata
of America, the remains of
toothed keelless birds have
been disentombed.

The most reptilian, least
bird -like of birds is the
oldest fossil of all, placed in
a sub-class by itself, the
Arckaoptery. r (lit. ancient
bird) from strata of Jurassic
age.

9. Mammalia. — Of the

Fig. 57. — Restoration of the extiact moa (Din-
oniis ingens ), and alongside of it the little
kiwi ( Apteryx vtantc/li). (From Cham-
bers’s Encyclop. ; after F. v. Hoclistetter.)

highest class of animals — the Mammalia — I need say least for they
are most familiar. Most of them are terrestrial, four-footed, and
hairy. Bats and whales, seals and sea-cows, are obviously excep-

268

PART III

The Study of Animal Life

tional. The brain of mammals is more highly developed than
that of other animals, and in the great majority there is a prolonged
(placental) connection between the unborn young and the mother.
In all cases the mothers feed the tender young with milk.

In the class there are three grades : —

(1) In the Duckmole ( Ornithorhynchus ) and the Porcupine
Ant-Eater ( Echidna ), and perhaps another genus Proechidna, the
females lay eggs. In many other ways these exclusively Austral-
asian mammals are primitive, exhibiting affinities with reptiles.

(2) In the Marsupials, which, with the exception of some
American Opossums, are also Australasian, the young are born at
a very tender age, as it were, prematurely. In the great majority
of genera, the mothers stow them away in an external pouch, where
they are fed and sheltered till able, to fend for themselves. In
Australia the Marsupials have been saved by insulation from stronger
mammals, which seem to have exterminated them in other parts
of the earth, the Opossums which hide in American forests being
the only Marsupials surviving outside Australasia, though fossils
show that the race had once a much wider distribution. In their
Australian retreat, apart from all higher Mammalia (mice, rabbits,
and the like being modern imports) the Marsupials have evolved
along many lines, prophetic of the higher orders of mammals.
There are “carnivores” like the Thylacine and the Dasyure,
“ herbivores” like the Kangaroos, “ insectivores ” like the banded
ant-eater Myrmecobius, and “rodents” like the Wombat.

(3) In all the other orders of mammals there is a close con-
nection between mother and unborn offspring.

Two orders are lowly and distinctly separate from the others
and from one another — the Edentata represented by sloths,
ant-eaters, armadillos, pangolins, and the Aard-Vark ; and the
Sirenia or Sea-Cows which now include only the dugong and the
manatee.

Along one fairly definite line we may rank three other orders
— the Insectivores, the Bats, and the Carnivores. The hedgehog,
which is at once a lowly and a central type of mammal, may be
taken as the beginning of this line. Along with shrews, moles,
porcupines, the hedgehogs form the order Insectivora. To these
the Bats (Cheiroptera), with their bird-like powers of flight, are
linked, while the Carnivora (cats, dogs, bears, and seals), though
progressive in a different direction, seem also related.

Comparable to the Insectivores, but on a different line, are the
gnawing Rodents, rabbits and hares, rats and mice, squirrels and
beavers. This line leads on to the Elephants, from the company
of which the mammoths have disappeared since man arose on the
earth. With the Elephants, the rock-coneys or Hyraxes — “ a feeble

chap, xvi Backboned Animals 269

folk ” — seem to be allied. Both are often included in the great
order of hoofed animals or Ungulates, along with the odd-toed

Fig. 58. — Phenacodus primcrtnts, a primitive extinct mammal from the lower
Eocene of N. America. The actual size of the slab of rock on which it rested
was 49 inches in length. (From Chambers’s Encyclop. ; after Cope.)

animals — horse, rhinoceros, and tapir, and a larger number of
even-toed forms, hog and hippopotamus, camel and dromedary,

Fig. 59. — Head of gorilla. (From Du Chaillu.)

and the true cud-chewers or ruminants such as sheep and cattle,
deer and antelopes. From the ancient predecessors of the modern

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The Study of Animal Life

Ungulates, it seems likely enough that the Cetaceans (whales and
dolphins) diverged.

A third line, which we may call median, leads through the
Lemurs, on to Monkeys. It must be noted, however, that these
lines, which seem distinct from one another if we confine our
attention to living mammals, are linked by extinct forms. Thus a

remarkable fossil type, Phcnacodas , is regarded by Cope as pre-
senting affinities with Ungulates, Lemurs, and Carnivores.

The monkeys which most closely resemble man in structure,
habits, and intelligence, are the so-called anthropoid apes, the
gorilla, the chimpanzee, the orang-utan, and the gibbon. A
second grade is represented by the more dog-like, narrow-nosed
Old World apes, such as the baboons and mandrills. Lower in
many ways are the broad-nosed New World or American monkeys,
e.g. the numerous species of Cebus, some of which are the familiar

CHAP. XVI

Backboned A nimals

271

companions of itinerant musicians, while lowest and smallest among
true monkeys are the South American marmosets. Distinct from
all these, probably outside the monkey order altogether, are the
so-called half-monkeys or Lemurs.

We might describe the clever activities of monkeys, the shelters
which some of them make, their family life, parental care and
sociality, their docility, their intelligent habits of investigation, and
their quickness to profit by experience ; but it would all amount to
this, that their life at many points touches the human, that they
are in some ways like growing children, in other ways like savage
men, though with more circumscribed limits of progress than either.

ORDERS OF MAMMALS.

MONOTREMES

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272 The Study of Animal Life part m

SURVEY OF THE ANIMAL KINGDOM

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BIRDS.

Flying-Birds. Running-Birds.

Placentals.
MAMMALS. Marsupials.

Monotremes.

Snakes. Lizards. REPTILES. Crocodiles. Tortoises.

Double- Breathers.

Bony-Fishes.

FISHES. „ .,

Ganoids.

Elasmobranchs.

AMPHIBIANS.
Newt. Frog.

CYCLOSTOMATA.
Lamprey. Hagfish.

LANCELET.

TUNICATES.

Trisects Arachnids

BALANOGLOSSUS.

Cuttlefish.

Gasteropods.

MOLLUSCS.

Bivalves.

Myriapods.

Peripatus.

ARTHROPODS.

Crustaceans.

ANNELIDS.

“WORMS."

FLAT-WORMS.

Feather-stars.

Brittle-stars.

Starfish.

ECHINODERMS.

Sea-urchins.

Sea-cucumbers.

Ctenophores. Jellyfish. Sea-Anemones. Corals.
STINGING-ANIMALS or CG2LENTERATES.
Medusoids and Hydroids.

SPONGES.

Infusorians. Rhizopods. Gregarines.

SIMPLEST ANIMALS.

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PART IV

THE EVOLUTION OF ANIMAL LIFE

CHAPTER XVII

THE EVIDENCES OF EVOLUTION

I. The Idea of Evolution — 2. Arguments for Evolution : Physio-
logical’, Morphological, Historical — 3. Origin of Life

We observe animals in their native haunts, and study their
growth, their maturity, their loves, their struggles, and their
death ; we collect, name, preserve, and classify them ; we
cut them to pieces, and know their organs, tissues, and
cells ; we go back upon their life and inquire into the secret
working of their vital mechanism ; we ransack the rocks for
the remains of those animals which lived ages ago upon the
earth ; we watch how the chick is formed within the egg,
and yet we are not satisfied. We seem to hear snatches of
music which we cannot combine. We seek some unifying
idea, some conception of the manner in which the world of
life has become what it is.

1. The Idea of Evolution. — We do not dream now,
as men dreamed once, that all has been as it is since all
emerged from the mist of an unthinkable beginning ; nor
can we believe now, as men believed once, that all came
into its present state of being by a flash of almighty volition.
We still dream, indeed, of an unthinkable beginning, but
we know that the past has been full of change ; we still

T

2 74 The Study of Animal Life part iv

believe in almighty volition, but rather as a continuous reality
than as expressed in any event of the past. Thus Erasmus
Darwin (1794), speaking of Hume, says “he concluded
that the world itself might have been generated rather than
created ; that it might have been gradually produced from
very small beginnings, increasing by the activity of its
inherent principles, rather than by a sudden evolution of
the whole by the Almighty fiat.” In short, we have
extended to the world around us our own characteristic
perception of human history ; we have concluded that in all
things the present is the child of the past and the parent
of the future.

But while we dismiss the theory of permanence as
demonstrably false, and the theory of successive cataclysms
and re-creations as improbable,1 without feeling it necessary
to discuss either the falsity or the improbability, we must
state on what basis our conviction of continuous evolution
rests. “ La nature ne nous offre le spectacle d’aucune
creation, c’est d’une continuation etemelle.” “As in the
development of a fugue,” Samuel Butler says, “ where,
when the subject and counter-subject have been announced,
there must thenceforth be nothing new, and yet all must
be new, so throughout organic nature — which is a fugue
developed to great length from a very simple subject —
everything is linked on to and grows out of that which
comes next to it in order — errors and omissions excepted.”

2. Arguments for Evolution. — What then are the facts
which have convinced naturalists that the plants and the
animals of to-day are descended from others of a simpler
sort, and the latter from yet simpler ancestors, and so on,
back and back to those first forms in which all that suc-
ceeded were implied ? I refer you to Darwin’s Origiti of
Species (1859), where the arguments were marshalled in
such a masterly fashion that ’ they forced the conviction

1 I use the word in its literal sense — ' ‘ not admitting of proof. ” It is
not my duty nor my desire to discuss the poetical, or philosophical,
or religious conceptions which lie behind the concrete cosmogonies of
different ages and minds. To many modern theologians creation
really means the institution of the order of nature, the possibility of
natural evolution included.

chap, xvii The Evidences of Evolution 275

of the world. To the statements of the case by Spencer,
Haeckel, Huxley, Romanes, and others, I have given
references in the chapter on books. Darwin’s arguments
were derived (a) from the distribution of animals in space ;
(J>) from their successive appearance in time, ( c ) from actual
variations observed in domestication, cultivation, and in
nature ; (d) from facts of structure, e.g. homologous and
rudimentary organs, (e) from embryology. I shall simply
illustrate the different kinds of evidence, and that under
three heads — (a) physiological, (b) structural, (c) his-
torical.

(a) Physiological. — A study of the life of organisms
shows that the ancient and even Lirmrean dogma of the
constancy or immutability of species was false. Organisms
change under our eyes. They are not like cast-iron ; they
are plastic. One of the most striking cases in the Natural
History Collection of the British Museum is that near the
entrance, where on' a tree are perched domesticated pigeons
of many sorts — fantail, pouter, tumbler, and the like —
while in the centre is the ancestral rock-dove Columba livia,
from which we know that all the rest have been derived.
In other domesticated animals, even when we allow that
some of them have had multiple origins, we find abundant
proof of variability. But what occurs under man’s super-
vision in the domestication of animals and in the culti-
vation of plants occurs also in the state of nature. N atural
“ varieties ” which link species to species are very common,
and the offspring of one brood differ from one another and
from their parents. How many strange sports there are
and grim reversions ! and, as we shall afterwards see,
modifications of individuals by force of external conditions
are not uncommon. Those who say they see no variation
now going on in nature should try a month’s work at identi-
fying species. I have known of an ancient man who dwelt
in a small town • he did not believe in the reality of railways
and to him the testimony of observers was as an idle tale ;
he was not daunted in his scepticism even when the railway
was extended to his town, for he was aged, and remained
at home, dying a professed unbeliever in that which he had

PART IV

2 76 The Study of Animal Life

chap, xvii The Evidences of Evolution 277

never seen. Conviction depends on more than intelligence,
often on emotional vested interests.

( b ) Morphological. — There are said to be over a million
species of living animals, about half of them insects.
Even their number might suggest blood-relationship, but our
recognition of this becomes clear when we see that species
is often united to species, genus to genus, and even class
to class, by connecting links. The fact that we can make
at least a plausible genealogical tree of animals, arranging
them in series along the lines of hypothetical pedigree, is
also suggestive.

Throughout long series, structures fundamentally the
same appear with varied form and function ; the same bones
and muscles are twisted into a variety of shapes. Why this
adherence to type if animals are independent of one
another ? How necessary it is if all are branches of one
tree.

By rudimentary organs also the same conclusion is
suggested. What mean the unused gill-clefts of reptiles,
birds, and mammals, unless the ancestors of these classes
were fish-like ; what mean the teeth of very young whale-
bone whales, of an embryonic parrot and turtle, unless they
are vestiges of those which their ancestors possessed ? There
are similar vestigial structures among most animals. In
man alone there are about seventy little things which might
be termed rudimentary ; his body is a museum of relics. We
are familiar with unsounded or rudimentary letters in many
words; we do not sound the “ 0” in leopard nor the “1”
in alms, but from these rudimentary letters we read the
history of the words.

(c) Historical. — Every one recognises that animals have
not always been as they now are ; we have only to dig to
be convinced that the fauna of the earth has had a history.
But it does not follow that the succession of fauna after
fauna, age after age, has been a progressive development.
What evidence is there, of this ?

In the first place, there is the general fact that fishes
'appear before amphibians, and these before reptiles, and
these before birds, and that the same correspondence

278

The Study of Animal Life part iv

between order of appearance and structural rank is often
true in detail within the separate classes of animals. There
are some marvellously complete series of fos-
sils, especially, perhaps, that of the extinct
cuttlefishes, in which the steps of progressive
evolution are still traceable. Moreover, the
^ long pedigree of some animals, such as the
horse, has been worked out so perfectly that
more convincing demonstration is hardly pos-
sible. In Professor Huxley’s American Ad-
dresses■, or in that pleasant introduction to
zoology afforded by Professor W. H. Flower’s
little book on the horse (Modern Science
Series, Lond., 1891), you will find the story
of the horse’s pedigree most lucidly told :
how in early Eocene times there lived small
quadrupeds about the size of sheep that
walked securely upon five toes, how these
animals lost, first the inner toe, while the
third grew larger, and then the fifth ; how the
third continued to grow larger and the second
and fourth to become smaller until they dis-
appeared almost entirely, remaining only as
small splint bones ; and how thus the light-
footed runners on tiptoe of the dry plains
were evolved from the short - legged splay-
footed plodders of the Eocene marshes. Fin-
ally, there are many extinct types which link
Fan’d hind7eet°of order to order and even class to class, such

the horse and as that strange mammal Phenacodus. which
some of its an- °

cestors, show- seems to occupy a central position in the
mg the gradual serjes s0 numerous are its affinities, or such
the number of as those saurians which link crawling reptile
Chambers^™ to soaring bird.

cyclop.-, after Another historical argument of great im-
Marsh.) portance is that derived from the study of

the geographical distribution of animals, but this cannot be
appreciated without studying the detailed facts. These
suggest that the various types of animals have spread from

chap, xvii The Evidences of Evolution 279

definite centres, along convenient paths of diffusion, varying
into species after species as their range extended.

But the history of the individual is even more instructive.
The first three grades of structure observed among living
animals are: (1) Single cells (most Protozoa), (2) balls of
cells (a few Protozoa which form colonies), and (3), two-
layered sacs of cells (eg. the simplest sponges). But these
three grades correspond to the first three steps in the indi-
vidual life-history of any many-celled animal. Every one
begins as a single cell, at the presumed beginning again ;
this divides into a ball of cells, the second grade of struc-
ture ; the ball becomes a two-layered sac of cells. The

Fig. 63. — Antlers of deer (1-5) in successive years ; but the figure might almost
represent at the same time the degree of evolution exhibited by the antlers
of deer in successive ages. (From Chambers’s EncycloJ> .)

correspondence between the first three grades of structure
and the first three chapters in the individual’s life-history is
complete. It is true as a general statement that the indi-
vidual development proceeds step by step along a path
approximately parallel to the presumed progress of the
race, so far as that is traceable from the successive grades
of structure and from the records of the rocks. Even in
regard to details such as the development of antlers on stags
the parallelism of racial and individual histoiy may be
observed. Of this correspondence it is difficult to see any
elucidation except that the individual in its life-history in
great part re-treads the path of ancestral evolution.

I have illustrated these evidences of evolution very

28o

PART IV

The Study of Animal Life

briefly, for they have been stated many times of late years.
The idea of evolution has also justified itself by the light
which it has cast not only on biological, but on physical,
psychological, and sociological facts. There has never been
a more germinal idea ; it is fast becoming organic in all
our thinking.

To those who feel a repugnance to the doctrine of
descent, I suggest the following considerations : —

(1) In so far as conclusions do not affect conduct, it
seems wise to conserve what makes one happiest. If your
intellectual and emotional necessities are better satisfied,
for instance, by any one of the creationist theories than
by that of a gradual and natural progress from simple
beginnings to implied ends, and if you feel that your sense
of the marvel, beauty, and sacredness of life would be
impoverished by a change of theory, then I should not seek
to persuade you.

(2) But as we do not think a tree less stately because
we know the tiny seed from which it grew, nor any man
less noble because he was once a little child, so we ought
not to look on the world of life with eyes less full of wonder
or reverence, even if we feel that we know something of its
humble origins.

(3) Finally, we should be careful to distinguish between
the doctrine of natural descent, which, to most naturalists,
seems a solemn fact, and the theories of evolution which
explain how the progressive descent was brought about.
For in regard to the causal, as distinguished from the modal
explanation of the world, we are or ought to be uncertain.

3. Origin of Life. — It is no dogma, nor yet a “ law
of Biogenesis,” but a fact of experience, to which no excep-
tion has been demonstrated, that living organisms arise
from pre-existent organisms — Omne vivum e vivo.

As to the origin of life upon the earth we know nothing,
but hold various opinions. (1) Thus it is believed that life
began independently of those natural conditions which come
within the ken of scientific inquirers ; in other words, it is
believed that the first living things were created. That
this belief presents intellectual difficulties to many minds

CHAP. XVII

The Evidences of Evolution 281

may mean that its fittest expression in words has not been
attained, or is unattainable. (2) It has been suggested
that germs of life reached this earth in the bosom of
meteorites from somewhere else. This at least shifts the
responsibility of the problem off the shoulders of this planet.
(3) It is suggested that living matter may have been evolved
from not-living matter on the earth’s surface. If we accept
this suggestion, we must of course suppose that in not-living
matter the qualities characteristic of living organisms are
implicit. The evolutionist’s common denominator is then
as inexpressibly marvellous as the philosopher’s greatest
common measure.

CHAPTER XVIII

THE EVOLUTION OF EVOLUTION THEORIES

I. Greek Philosophers — 2. Aristotle — 3. Lucretius — 4. Evolution-
ists before Darwin — 5. Three old Masters: Buff on, Erasmus
Darwin, Lamarck — 6. Charles Darwin — 7. Darwin's Fellow-
workers — 8. The Present State of Opinion

The conception of evolution is no new idea, it is the human
idea of history grown larger, large enough to cover the
whole world. The extension of the idea was gradual, as
men felt the need of extending it ; and at the same moment
we find men believing in the external permanence of one
set of phenomena, in the creation of others, in the evolution
of others. One authority says human institutions have been
evolved ; man was created ; the heavens are eternal. Ac-
cording to another, matter and motion are eternal ; life was
created ; the rest has been evolved, except, perhaps, the
evolution theory which was created by Darwin.

1. Greek Philosophers. — Of the wise men of Greece
and what they thought of the nature and origin of
things, I shall say little, for I have no direct acquaintance
with the writings of those who lived before Aristotle.
Moreover, though an authority so competent as Zeller has
written on the “Grecian predecessors of Darwin,” most of
them were philosophers not naturalists, and we are apt to
read our own ideas into their words. They thought, indeed,
as we are thinking, about the physical and organic universe,
and some of them believed it to be, as we do, the result of

ch. xviii The Evolution of Evolution Theovies 283

a process ; but here in most cases ends the resemblance
between their thought and ours.

Thus when Anaximander spoke of a fish-like stage in the
past history of man, this was no prophecy of the modern
idea that a fish-like form was one of the far-off ancestors of
backboned animals, it was only a fancy invented to get over
a difficulty connected with the infancy of the first human
being.

Or, when we read that several of these sages reduced
the world to one element, the ether, we do the progress of
knowledge injustice if we say that men are simply returning
to this after more than two thousand years. For that
conception of the ether which is characteristic of modern
physical science has been, or is being, slowly attained by
precise and patient analysis, whereas the ancient conception
was reached by metaphysical speculation. If we are
returning to the Greeks, it is on a higher turn of the spiral,
so far at least as the ether is concerned.

When we read that Empedocles sought to explain the
world as the result of two principles — love and hate —
working on the four elements, we may, if we are so inclined,
call these principles “ attractive and repulsive forces ” ; we
may recognise in them the altruistic and individualistic
factors in organic evolution, and what not ; but Empedocles
was a poetic philosopher, no far-sighted prophet of evolu-
tion.

But the student cannot afford to overlook the lesson
which Democritus first clearly taught, that we do not
explain any result until we find out the natural conditions
which bring it about, that we only understand an effect
when we are able to analyse its causes. We require a so-
called “mechanical,” or more strictly, a dynamical explana-
tion of results. It is easy to show that it is advantageous
for a root to have a root-cap, but we wish to know how the
cap comes to be there. It is obvious that the antlers of a
stag are useful weapons, but we must inquire as precisely
as possible how they first appeared and still grow.

2. Aristotle. — As in other departments of knowledge,
so in zoology the work of Aristotle is fundamental. It is

284 The Study of Animal Life part iv

wonderful to think of his knowledge of the forms and ways
of life, or the insight with which he foresaw such useful dis-
tinctions as that between analogous and homologous organs,
or his recognition pf the fact of correlation, of the advan-
tages of division of labour within organisms, of the gradual
differentiation observed in development. He planted seeds
which grew after long sleep into comparative anatomy and
classification. Yet with what sublime humility he says : “ I
found no basis prepared, no models to copy. Mine is the
first step, and therefore a small one, though worked out with
much thought and hard labour.” Aristotle was not an
evolutionist, for, although he recognised the changefulness of
life, the world was to him an eternal fact not a stage in a
process.

“ In nature, the passage from inanimate things to animals is so
gradual that it is impossible to draw a hard-and-fast line between
them. After inanimate things come plants, which differ from one
another in the degree of life which they possess. Compared with
inert bodies, plants seem endowed with life ; compared with
animals, they seem inanimate. From plants to animals the passage
is by no means sudden or abrupt ; one finds living things in the
sea about which there is doubt whether they be animals or plants.”
“ Animals are at war with one another when they live in the same
place and use the same food. If the food be not sufficiently
abundant they fight for it even with those of the same kind.”

3. Lucretius. — Among the Romans Lucretius gave
noble expression to the philosophy of Epicurus. I shall
not try to explain his materialistic theory of the concourse
of atoms into stable and well-adapted forms, but rather
quote a few sentences in which he states his belief that the
earth is the mother of all life, and that animals work out
their destiny in a struggle for existence. He was a cosmic,
but hardly an organic evolutionist, for, according to his
poetic fancy, organisms arose from the earth’s fertile bosom
and not by the gradual transformation of simpler predecessors.

“ In the beginning the earth gave forth all kinds of herbage and
verdant sheen about the hills and over all the plains ; the flower}’
meadows glittered with the bright green hue, apd next in order to
the different trees was given a strong and emulous desire of grow-

ch. xviii The Evolution of Evolution Theories 285

ing up into the air with full unbridled powers. . . . With good
reason the earth has gotten the name of mother, since all things
have been produced out of the earth. . . .

“ We see that many conditions must meet together in things in
order that they may beget and continue their kinds ; first a supply
of food, then a way in which the birth-producing seeds throughout
the frame may stream from the relaxed limbs. . . . And many
races of living things must then have died out and been unable to
beget and continue their breed. For in the case of all things which
you see breathing the breath of life, either craft or courage or else
speed has from the beginning of its existence protected and pre-
served each particular race. And there are many things which,
recommended to us by their useful services, continue to exist con-
signed to our protection.

“ In the first place, the first breed of lions and the savage races
their courage has protected, foxes their craft, and stags their prone-
ness to flight. But light-sleeping dogs with faithful heart in breast,
and every kind which is born of the seed of beasts of burden, and at
the same time the woolly flocks and the horned herds, are all con-
signed to the protection of man. For they have ever fled with
eagerness from wild beasts,, and have ensued peace, and plenty of
food obtained without their own labour, as we give it in requital of
their useful services. But those to whom nature has granted none
of these qualities, so that they could neither live by their own
means nor perform for us any useful service, in return for which
we should suffer their kind to feed and be safe under our protection,
those, you are to know, would lie exposed as a prey and booty
of others, hampered all in their own death-bringing shackles, until
nature brought that kind to utter destruction.”

4. Evolutionists before Darwin. — From Lucretius I
shall pass to Buffon, for the intervening centuries were un-
eventful as regards zoology. Hugo Spitzer, one of the histo-
rians of evolution, finds analogies between certain mediaeval
scholastics and the Darwinians of the nineteenth century,
but these are subtle comparisons. Yet long before Darwin’s
day there were evolutionists, and the first of these who can
be called great was Buffon.

We must guard against supposing that .the works of
Buffon, or Lamarck, or Darwin were inexplicable creations
of genius, or that they came like cataclysms, without warning,
to shatter the conventional traditions of their time. For all
great workers have their forerunners, who prepare their

286

PART JV

The Study of Animal Life

paths. Therefore in thinking out the history of evolutionist
theories before that of Buffon, we must take account of
many forces which began to be influential from the twelfth
century onwards. “ Evolution in social affairs has not
only suggested our ideas of evolution in the other sciences,
but has deeply coloured them in accordance with the
particular phase of social evolution current at the time.” 1
In other words, we must abandon the idea that we can
understand the history of any science as such, without
reference to contemporary evolution in other departments
of activity. The evolution of theories of evolution is bound
up with the whole progress of the world.

In trying to determine those social and intellectual forces
of which the modern conception of organic evolution has
been a resultant, we should take account of -social changes,
such as the collapse of the feudal system, the crusades, the
invention of printing, the discovery of America, the French
Revolution, the beginning of the steam age ; of theological
and religious movements, such as the Protestant Reforma-
tion and the spread of Deism ; of a long series of evolu-
tionist philosophers, some of whom were at the same time
students of the physical sciences, — notably Descartes,
Spinoza, Leibnitz, Herder, Kant, and Schelling ; of the
acceptance of evolutionary conceptions in regard to other
orders of facts, especially in regard to the earth and the
solar system ; and, finally, of those few naturalists, like De
Maillet and Robinet, who, before Buffon’s day, whispered
evolutionist heresies. The history of an idea is like that
of an organism in which cross-fertilisation and composite
inheritance complicate the pedigree.

5. Three old Masters. — Among the evolutionists before
Darwin I shall speak of only three — Buffon, Erasmus Darwin,
and Lamarck.

Buffon (1707-1788) was born to wealth and was wedded
to Fortune. He sat in kings’ houses, his statue adorned their
gardens. As Director of the Jardm du Roi he had oppor-
tunity to acquire a wide knowledge of animals. He com-
manded the assistance of able collaborateurs, and his own
1 Article “Evolution” (P. Geddes) in Chambers's Encyclopedia.

ch. xvui The Evolution of Evolution Theories 287

industry was untiring. He was about forty years old when
he began his great Natural History, and he worked till he
was fourscore. He lived a full life, the success of which
we can almost read in the strong confidence of his style.

‘ Le style, c’est l’homme meme,” he said ; or again, “ Le
style est comme le bonheur ; il vient de la douceur de Fame.”
Rousseau called him “ La plus belle plume du si£cle ; ”
Mirabeau said, “ Le plus grand homme de son sifecle et de
bien d’autres ; ” Voltaire first mocked and then praised him ;
and Diderot also eulogised. Buffon was first a man then
a zoologist, which seems to be the natural, though by no
means universally recognised, order of precedence, and we
have pleasant pictures of his handsome person, his magnifi-
cence, his diplomatic manners, and a splendid genius, which
he himself called “ a supreme capacity for taking pains.”

Buffon’s culture was very wide. He had an early
training in mathematics, and translated Newton’s Fluxions ;
he seems to have been familiar with the chemistry and
physics of his time ; he was curious about everything.
Before Laplace, he elaborated an hypothesis as to the origin
of the solar system ; before Hutton and Lyell, he realised
that causes like those now at work had in the long past
sculptured the earth ; he had a special theory of heredity
not unlike Darwin’s, and a by no means narrow theory of
evolution, in which he recognised the struggle for existence
and the elimination of the unfit, the influence of isolation
and of artificial selection, but especially the direct action of
food, climate, and other surrounding influences upon the
organism. It is generally allowed that there is in Buffon’s
writings something of that indefiniteness which often charac-
terises pioneer works, and a lack of depth not unnatural in
a survey so broad, but they exhibit some remarkable illustra-
tions of prophetic genius, and a lively appreciation of
nature.

It is probable that Buffon’s treatment of zoology gained
freedom because he wrote in French, having shaken off the
shackles which the prevalent custom of writing in Latin
imposed, and it cannot be doubted that his works did some-
thing to prepare the way for the future reception of the

288

PARI' IV

The Study of Animal Life

doctrine of descent. He had a vivid feeling of the unity
of nature, throwing out hints in regard to the fundamental
similarity of different forms of matter, suggesting that heat
and light are atomic movements, denying the existence of
hard-and-fast lines — “ Le vivant et l’animd est une propridtd
physique de la mati&re 1” protesting against crude distinctions
between plants and animals, and realising above all that
there is one great family of life. Naturalists had been
wandering up and down the valleys studying their charac-
teristic contours ; Buffon took an eagle’s flight and saw the
connected range of hills, — “ l’enchainement des etres.”

Erasmus Darwin (1731-1802), grandfather to the
author of the Origin of Species , was a large-hearted, thought-
ful physician, whose life was as full of pleasant eccentricities,
as his stammering speech of wit, and his books of wisdom.
We have pleasant pictures of the philosophical physician
of Lichfield and Derby, driving about in a whimsical un-
stable carriage of his own contrivance, prescribing abundant
food and cowslip wine, rich in good health and generosity.
Comparing his writings with those of Buffon, an acquaint-
ance with which he evidently possessed, we find more
emotion and intensity, more of the poet and none of the
diplomatist. He approached the study of organic life on
the one hand as a physician and physiologist, on the other
hand as a gardener and lover of plants ; and, apart from
poetic conceits, his writings are characterised by a direct-
ness and simplicity of treatment which we often describe as
“ common-sense.”

He believed that the different kinds of plants and animals
were descended from a few ancestral forms, or possibly
from one and the same kind of “ vital filament,” and that
evolutionary change was mainly due to the exertions which
organisms made to preserve or better -themselves. He
showed that animals were driven to exertion by hunger, by
love, and by the need of protection, and explained their
progress as the result of their endeavours. Buffon under-
rated the transforming influence of action, and laid emphasis
upon the direct influence of surroundings ; Erasmus Darwin
emphasised function, and regarded the influence of the

ch. xvm The Evolution of Evolution Theories 289

environment as for the most part indirect. Let us quote
some conclusions from his Zoonomia (1794): —

“ Owing to the imperfection of language the offspring is termed
a new animal, but is in truth a branch or elongation of the
parent, since a part of the embyron animal is, or was, a part of the
parent, and therefore in strict language cannot be said to be entirely
new at the time of its production ; and therefore it may retain
some of the habits of the parent-system.”

“The fetus or embryon is formed by apposition of new parts,
and not by the distention of a primordial nest of germs included
one within another like the cups of a conjuror.”

“ From their first rudiment, or primordium, to the termination
of their lives, all animals undergo perpetual transformations ; which
are in part produced by their own exertions in consequence of
their desires and aversions, of their pleasures and their pains, or
of irritations, or of associations ; and many of these acquired forms
or propensities are transmitted to their posterity.”

“ As air and water are supplied to animals in sufficient profusion,
the three great objects of desire, which have changed the forms of
many animals by their exertions to gratify them, are those of lust,
hunger, and security.”

“This idea of the gradual generation of all things seems to have
been as familiar to the ancient philosophers as to the modern ones,
and to have given rise to the beautiful hieroglyphic figure of the
■wpGrrov ipbv, or first great egg, produced by night, that is, whose
origin is involved in obscurity, and animated by s, that is, by
Divine Love ; from whence proceeded all things which exist.”

On Lamarck (1744-1829) success did not shine as it
did on the Comte de Buffon or on Dr. Erasmus Darwin.
His life was often so hard that we wonder he did not say
more about the struggle for existence. As a youth of six-
teen, destined for the Church, he rides off on a bad horse
to join the French army, then fighting in Germany, and
bravely wans promotion on his first battle-field. After the
peace he is sent into garrison at Toulon and Monaco,
where his scientific enthusiasm is awakened by the Flora
of the south. Retiring in weakened health from military
service, he earns his living in a Parisian banker’s office,
devotes his spare energies to the study of plants, and
writes a Flore fran^aise in three volumes, the publica-
tion of which (1778) at the royal press was secured by

U

290

PART IV

The Study of Animal Life

Buffon’s patronage. As tutor to Buffon’s son, he travels
in Europe and visits some of the famous gardens, and we
can hardly doubt that Buffon influenced Lamarck in many
ways. After much toil as a literary hack and scientific
drudge, he is elected to what we would now call a Professor-
ship of Invertebrate Zoology, a department- at that time
chaotic. In 1794 he began his lectures, and each year
brought increased order to his classification and museum
alike. At the same time, however, he was lifting his anchors
from the orthodox moorings, relinquishing his belief in the
constancy of species, following (we know not with what
consciousness) the current which had already borne Buffon
and Erasmus Darwin to evolutionary prospects. In 1802
he published Researches on the Organisation of Living
Bodies ; in 1809 a Philosophie Zoologique ; from 1816-
1822 his Nattiral History of Invertebrate Aminats, a large
work in seven volumes, part of which the blind naturalist
dictated to his daughter. Busy as he must have been with
zoolog)', his restless intellect found time to speculate — it
must be confessed to little purpose — on chemical, physical,
and meteorological subjects. Thus he ran an unsuccessful
tilt against Lavoisier’s chemistry, and published for ten
years annual forecasts of the weather, which seem to have
been almost always wrong. Nor did Lamarck add to his
reputation by a theory of Hydrogeology , and his scientific
friends who were loyal specialists shrugged their shoulders
more and more over his intellectual knight-errantry.

Poverty also clouded his later years, his treasured
collections had to be sold for bread, his theories made no
headway, his merits were unrecognised. Yet now a La-
marckian school is strong in France and in America, and
even those who deny his doctrines admit that he was one
of the bravest of pioneers.

Of Lamarck’s Philosophie Zoologique , Haeckel says,
“ This admirable work is the first connected and thoroughly
logical exposition of the theory of descent.” And again, he
says, “To Lamarck will remain the immortal glory of
having for the first time established the theory of descent
as an independent scientific generalisation of the first order,

ch. xvni The Evolution of Evolution Theories 291

ns the foundation of the whole of Biology.1, But the verdict
of the majority of naturalists in regard to Lamarck’s doctrines
has not tended to be eulogistic. Cuvier, in his Eloge de M.
de Lamarck delivered before the French Academy in 1832,
said, “A system resting on such foundations may amuse
the imagination of a poet, etc., . . . but it cannot for a
moment bear the examination of any one who has dissected
the hand, the viscera, or even a feather.” The great Cuvier
was a formidable obscurantist.

But let us hear Lamarck himself : —

“ Nature in all her work proceeds gradually, and could not pro-
duce all the animals at once. At first she formed only the simplest,
and passed from these on to the most complex.”

“ The limits of so-called species are not so constant and unvary-
ing as is commonly supposed. Spontaneous generation started
each particular series, but thereafter one form gives rise to another.
In life we should see, as it were, a ramified continuity if certain
species had not been lost.”

“The operations of Nature in the production of animals show
that there is a primary and predominant cause which gives to
animal life the power of progressive organisation, of gradually
complicating and perfecting not only the organism as a whole, but
each system of organs in particular.”

“ First Law. Life by its inherent power tends continually to
increase the volume of every living body, and to extend the
dimensions of its parts up to a self-regulated limit.

* ‘ Second Law. The production of a new organ in an animal body
results from the occurrence of some new need which continues to
make itself felt, and from a new movement which this need origin-
ates and sustains.

“ Third Law. The development of organs and their power of
action are constantly determined by the use of these organs.

“ Fourth Law. All that has been acquired, begun, or changed in
the structure of individuals during the course of their life is pre-
served in reproduction and transmitted to the new individuals
which spring from those which have experienced the changes.”
These four laws I have cited from Lamarck’s Histoire Naturelle,
but in illustration of the emphasis with which he insisted on use
and disuse, I take the following passages, translated by Samuel
Butler, from the Philosophic Zoologique : —

“ Every considerable and sustained change in the surroundings
of any animal involves a real change in its needs.”

292 The Study of Animal Life part iv

“Such change of needs involves the necessity of changed
action in order to satisfy these needs, and, in consequence, of new
habits.”

“It follows that such and such parts, formerly less used, are
now more frequently employed, and in consequence become more
highly developed ; new parts also become insensibly evolved in the
creature by its own efforts from within.”

‘ ‘ These gains or losses of organic development, due to use or
disuse, are transmitted to offspring, provided they have been- com-
mon to both sexes, or to the animals from which the offspring have
descended.”

The historian of the evolution of evolution theories
should take account of many workers besides Buffon,
Erasmus Darwin, and Lamarck; of Treviranus (1776-
1837), whose Biology or Philosophy of Living Nature (1802-
1805) is full of evolutionary suggestions ; of Geoffroy St.
Hilaire, who in 1830, before the French Academy of
Science, fought with Cuvier, the fellow-worker of his youth,
an intellectual duel on the question of descent ; of Goethe
who, in his eighty-first year, heard the tidings of Geoffroy’s
defeat with an interest which transcended the political
anxieties of the time, and whose own epic of evolution sur-
passes that of Lucretius ; of Oken’s speculative mist, amid
which the light of evolutionary ideas danced like a will-o’-
the-wisp ; of many others in whose mind the truth grew if
it did not blossom. But we must now recognise the work
of Charles Darwin.

6. Darwin. — Though the general tenor of Darwin’s life
- — the impression of an industrious open-minded observer
and thinker, the picture of a man full of mercy', kindliness,
and peace — was familiar to many, his biography has filled
in those little details which make our impression living.
We see him now, as in a Holbein picture, with all the
paraphernalia of daily pursuit round about him. His high
chair, his orderly shelves, his torn-up reference books, his
window-sill laboratory, his yellow-back novels, his snuff-
box, and a hundred little touches, make the picture alive.
We learn, too, his methods of laborious but never toilsome
work, and the gradual progress of his thought from the con-
ventionalism of youth to the convictions of matured man-

ch. xvm The Evolution of Evolution Theories 293

hood. We read the curve of his moods, steadier than that
of most men, without any climax of speculative ecstasy, free
from any fall to a depth of pessimism. We hear his own
sincere voice in his simple autobiography, and even more
clearly perhaps in the unconstrainedness of his abundant
letters. There was seldom a great life so devoid of little-
ness, seldom a record of thought so free from subtlety.
There seems to be almost nothing hid which we could
wish revealed, or uncovered which we could wish hidden.
Darwin’s life was as open as the country around his her-
mitage.

Marcus Aurelius gives thanks in his roll of blessings
that he had not been suffered to keep quails ; so Darwin, in
recounting his mercies, does not forget to be grateful for
having been preserved from the snare of becoming a
specialist. From a more partial point of view, we have
reason to be thankful that he became a specialist, not in
one department, but in many. As a disciple of Linnaeus,
he described the species of barnacles in one volume, and
followed in the steps of Cuvier in anatomising them in
another. Of tissues and cells he knew less, being as
regards these items an antediluvian, and outside the guild
of those who dexterously wield the razor, and in so doing
observe the horoscope of the organism. Of protoplasm,
in regard to which modern biology says so much and knows
so little, he was not ignorant, for did he not study the
marvels of the state known as “ aggregation” ?

But it is not for special research that men are most
grateful to Darwin. Undoubtedly, if clear insight into the
world around us be esteemed in itself of value, the author
of Insectivorous Plants , The Fertilisation of Orchids , The
Movements of Plants, The Origin of Coral Reefs , The
Formation of Vegetable Mould, etc., runs no risk of being
forgotten. But though our possession of these results swells
the meed of praise, we usually regard them as outside of
Darwin’s real work, which, as every one knows, was his
contribution to the theory of organic life.

This contribution was threefold — (a) He placed the
theory of descent on a sure basis ; ( b ) he shed the light

294 The Study of Animal Life part iv

of this doctrine on various groups of phenomena ; and {c) he
essayed the problem of the factors in evolution.

(a) The man who makes us believe a fact is to us
more important than the original discoverer. And so
Darwin gets credit for inventing the theory of descent,
which in principle is as old as clear thought itself, and in
its biological application was stated a hundred years before
the publication of the Origin of Species (1859). The con-
ception was no new one, but Darwin first made men believe
it. The idea was not his, but he gave it to many. He did
not originate ; he established. He converted naturalists to
an evolutionary conception of the organic world.

(b) Having got people to believe the theory of
descent, — the theory of development out of preceding
conditions, — Darwin went on to show how the conception
would illumine all facts to which it was applicable. In his
work on the expression of emotions, and in scattered chap-
ters, he showed how the light might be shed upon the
secrets of mental activity. Whenever it was seen that
the doctrine could justify itself in regard to general organic
life, it was eagerly seized as an organon for the exploration
of special sets of facts. The phoenix revived and flew
croaking amid the smoke of burning systems. How one
discussed the evolution of language, and another that of
industry ; how the natural history of ethics was sketched
by one thinker, and the descent of institutions by another ;
how the conception has forced its way into the cloister
and the political arena, and has even found expression in
theories of literature, art, and religion, — is an often-repeated
story.

( c ) We have noticed that Buffon, and, let us add, Trevir-
anus, firmly maintained that the direct influence of the
external conditions of life was an important factor in evolu-
tion. We have also seen that Erasmus Darwin and Lamarck
were strongly convinced of the transforming power of use
and disuse. When Charles Darwin began to think and
write on the origin of species, he also recognised the trans-
forming influences of function and of environment. But
with the Buffonian or Lamarckian position he was never

ch. xviii The Evolution of Evolution Theories

295

satisfied ; he advanced to one of his own — to the theory of
natural selection, the characteristic feature of Darwinism.

Let us state this theory, which was foreseen by Matthew,
Wells, Naudin, and others, was developed simultaneously
by Darwin and by Alfred Russel Wallace, and has attained
remarkable acceptance throughout the world.

All plants and animals produce offspring which, though
like their parents, usually differ from them in possessing
some new features or variations. These are of more or
less obscure origin, and are often termed fortuitous or in-
definite. But throughout nature there is a struggle for
existence in which only a small percentage of the organisms
born survive to maturity or reproduction. Those which
survive do so because of the individual peculiarities which
have made them in some way more fit to survive than their
fellows. Moreover the favourable variation possessed by
the survivors is handed on as an inheritance to their off-
spring, and tends to be intensified when the new generation
is bred from parents both possessing the happily advan-
tageous character. This natural fostering of advantageous
variations and natural elimination of those less fit, explain
the general modification and adaptation of species, as well
as the general progress from simpler to higher forms of
life.

This theory that favourable variations may be fostered
and accumulated by natural selection till useful adaptations
result is the chief characteristic of Darwinism. Of this
theory Prof. Ray Lankester says : “ Darwin by his discovery
of the mechanical principle of organic evolution, namely, the
survival of the fittest in the struggle for existence, completed
the doctrine of evolution, and gave it that unity and au-
thority which was necessary in order that it should reform
the whole range of philosophy.” And again he says : “ The
history of zoology as a science is therefore the history of
the great biological doctrine of the evolution of living things
by the natural selection of varieties in the struggle for exist-
ence,— since that doctrine is the one medium whereby all
the phenomena of life, whether of form or function, are
rendered capable of explanation by the laws of physics and

296 The Study of Animal Life part iv

chemistry, and so made the subject-matter of a true science
or study of causes.” I have quoted these two sentences
because they illustrate better than any others that I have
seen to what exaggeration enthusiasm for a theory will lead
a strong intellect. But listen to a few sentences from
Samuel Butler, which I quote because they well illustrate
that the critics of Darwinism may also be extreme, and in
the hope that the contrast may be sufficiently interesting to
induce you to think out the question for yourselves.

“Buffon planted, Erasmus Darwin and Lamarck watered,
but it was Mr. Darwin who said ‘ That fruit is ripe,’ and
shook it into his lap. . . . Darwin was heir to a dis-
credited truth, and left behind him an accredited fallacy.

. . . Do animals and plants grow into conformity with
their surroundings because they and their fathers and
mothers take pains, or because their uncles and aunts go
away? . . . The theory that luck is the main means of
organic modification is the most absolute denial of God
which it is possible for the human mind to conceive. . . .”

7. Darwin’s Fellow-workers. — But we must bring this
historical sketch to a close by referring to four of the more
prominent, of Darwin’s fellow-workers — Wallace, Spencer,
Haeckel, and Huxley.

Alfred Russel Wallace, contemporary with Darwin,
not only in years, but in emphasising the truth of evolution-
ary conceptions, and in recognising the fact of natural
selection, has been justly called the Nestor of Biology. No
one will be slow to appreciate the splendid unselfishness
with which he has for thirty years sunk himself in the Dar-
winian theory, or the scientific disinterestedness which leads
him from the vei-y title of his last work 1 to its close, to
say so little — perhaps too little — of the important part
which he has played in evolving the doctrine. “ It was,”
Romanes says, “ in the highest degree dramatic that the
great idea of natural selection should have occurred inde-
pendently and in precisely the same form to two working
naturalists ; that these naturalists should have been country-
men ; that they should have agreed to publish their theory
1 Darwinistn, London, 1889.

ch. xvm The Evolution of Evolution Theories 297

on the same day ; and last, but not least, that, through the
many years of strife and turmoil which followed, these two
English naturalists consistently maintained towards each
other such feelings of magnanimous recognition that it is
hard to say whether we should most admire the intellectual
or the moral qualities which, in relation to their common
labours, they have displayed.”

Mr. Wallace is a naturalist in the old and truest sense,
rich in a world -wide experience of animal life, at once
specialist and generaliser, a humanist thinker and a social
striver, and a man of science who realises the spiritual
aspect of the world.

He believes in the “ overwhelming importance of natural
selection over all other agencies in the production of new
species,” differs from Darwin in regard to sexual selection,
to which he attaches little importance, and agrees with
Weismann in regard to the non -inheritance of acquired
characters.

But the exceptional feature in Wallace’s scientific philo-
sophy is his contention that the higher characteristics of
man are due to a special evolution hardly distinguishable
from creation.

Wallace finds their only explanation in the hypothesis
of “ a spiritual essence or nature, capable of progressive
development under favourable conditions.”

Herbert Spencer must surely have been an evolution-
ist by birth ; there was no hesitation even in the first strides
he took with the evolution-torch uplifted. A ponderer on
the nature of things, and the possessor of encyclopaedic
knowledge, he grasped what was good in Lamarck’s work,
and as early as 1852 published a plea for the theory of
organic evolution which is still remarkable in its strength
and clearness. The work of Darwin supplied corroboration
and fresh material, and in the Principles of Biology ( 1 863-66)
the theory of organic evolution first found philosophic, as
distinguished from merely scientific expression. To Spencer
we owe the familiar phrase “ the survival of the fittest,”
and that at first sight puzzling generalisation, “ Evolution is
an integration of matter and concomitant dissipation of

2 98 The Study of Animal Life part iv

motion, during which the matter passes from an indefinite
incoherent homogeneity to a definite coherent heterogeneity,
and during which the retained motion (energy) undergoes a
parallel transformation.” He has given his life to establish-
ing this generalisation, and applying it to physical, biological,
psychological, and social facts. As to the factors in organic
evolution, he emphasises the change-producing influences of
environment and function, and recognises that natural selec-
tion has been a very important means of progress.

Ernst Haeckel, Professor of Zoology in Jena, and
author of a great series of monographs on Radiolarians,
Sponges, Jellyfish, etc., may be well called the Darwin of
Germany. He has devoted his life to applying the doctrine
of descent, and to making it current coin among the people.
Owing much of his motive to Darwin, he stood for a time
almost alone in Germany as the champion of a heresy.
Before the publication of Darwin’s Descent of Man, Haeckel
was the only naturalist who had recognised the import of
sexual selection ; and of his Natural History of Creation
Darwin writes : “ If this work had appeared before my
essay had been written, I should probably never have com-
pleted it.” His most important expository works are the
above-mentioned Natiirliche Schopfungsgeschichte (1st ed.
1868 ; 8th ed. 1889) ; and his Anthropogenic (1874, trans-
lated as The Evolution of Man). These books are very
brilliantly written, though they offend many by their remorse-
less consistency, and by their impatience with theological
dogma and teleological interpretation. His greatest work,
however, is of a less popular character, namely, the Generelle
Mo7phologie (2 vols., Berlin, 1866), which in its reasoned
orderliness and clear generalisations ranks beside Spencer’s
Principles of Biology.

Huxley, by whose work the credit of British schools of
zoology has been for many years enhanced, was one of the first
to stand by Darwin, and to wield a sharp intellectual sword
in defence and attack. No one has fought for the doctrine
of descent in itself and in its consequences with more keen-
ness and success than the author of Man's Place in Nature
(1863), American Addresses, Lay Sermons, etc., and no one

ch. xvm The Evolution of Evolution Theories 299

has championed the theory of natural selection with more
confident consistency or with more skilfully handled
weapons.

8. The Present State of Opinion. — As Wallace says in
the preface to his work on Darwinism , “ Descent with
modification is now universally accepted as the order of
nature in the organic world.” But, while this is true, there
remains much uncertainty in regard to the way in which the
progressive ascent of life has come about, as to the mechan-
ism of the great nature-loom. The relative importance of
the various factors in evolution is very uncertain.1

The condition of evolution is variability, or the tendency
which animals have to change. The primary factors of
evolution are those which produce variations, which cause
organic inequilibrium. Darwin spoke of variations as
“ fortuitous,” “ indefinite,” “ spontaneous,” etc., and frankly
confessed that he could not explain how most of them arose.

Ultimately all variations in organisms must be due to
variations in their environment, that is to say, to changes in
the system of which organisms form a part. But this is
only a general truism.

1 All naturalists, however uncertain in regard to the factors in
evolution, accept the doctrine of descent — the general conception of
evolution — as a theory which has justified itself. It is not indeed so
demonstrable as is the doctrine of the conservation of energy, but it is
almost as confidently accepted. Few naturalists, however, have
attempted any philosophical justification of their belief. This is strange,
since it should surely give pause to the dogmatic evolutionist to reflect
that his own theory has been evolved like other beliefs, that his
scientific demonstration of it rests upon assumptions which have also
been evolved, that the entire system of evolutionary thought must be a
phase in the development of opinion, that, in short, he cannot be
dogmatic without being self-contradictory. See A. J. Balfour’s Defence
of Philosophic Doubt, pp. 260-274 (London, 1879). In regard to the
philosophical aspects of the doctrine of evolution see Prof. Knight's
essay on “ Ethical Philosophy and Evolution” in his Studies in Philo-
sophy and Literature (Lond. 1879), and, with additions, in Essays in
Philosophy (Boston and New York, 1890) ; Prof. St. George Mivart’s
Contemporary Evolution (Lond. 1876) ; E. von Hartmann’s Wahrhcit
und Irrthum im Daruiinismus ; an article by Prof. Tyndall on “Vir-
chow and Evolution” in Nineteenth Century, Nov. 1878 ; and articles
on “ Evolution ” by Huxley and Sully in Encyclopaedia Britatinica.

3°°

PART IV

The Study of Animal Life

There are evidently three direct ways in which organic
changes may be produced : ( i ) From the nature of the
organism itself ; i.e. from constitutional or germinal peculiar-
ities which are ultimately traceable to influences from
without ; (2) from changes in its functions or activity, in
other words, from use and disuse ; or (3) from the direct
influence of the external conditions of life — food, temperature,
moisture, etc.

Thus some naturalists follow Buffon in emphasising the
moulding influence of the environment, or agree with
Lamarck in maintaining that change of function produces
change of structure. But at present the tide is against
these opinions, because of the widespread scepticism as to
the transmissibility of characters thus acquired.

Those who share this scepticism refer the origin of
variations to the nature of the organism, to the mingling
of the two different cells from which the individual life
begins, to the instability involved in the complexity of the
protoplasm, to the oscillating balance between vegetative
and reproductive processes, and so on.

One prevalent opinion regards variations as arbitrary
sports in “ a chapter of accidents,” but according to the
views of a minority variations are for the most part definite,
occurring in a few directions, fixed by the constitutional
bias of the organism. The minority are “ Topsian ” evolu-
tionists who believe that the modification of species has
taken place by cumulative growth, influenced by function
and environment, and pruned by natural selection. To the
majority the theory that new species result from the action
of natural selection on numerous, spontaneous, indefinite
variations, is the “ quintessence of Darwinism ” and of truth.

Until we know much more about the primary factors
which directly cause variations it will not be possible to
decide in regard to the precise scope of natural selection
and the other secondary factors which foster or accumulate,
thin or prune, which in short establish a new organic
equilibrium. The argument has been too much in regard
to possibilities, too little in regard to observed facts of
variation.

ch. win The Evolution of Evolution Theories 301

The secondary factors of evolution may be ranked under
two heads : —

1. Natural Selection, or the survival of the fittest in the
struggle for existence, and 2. Isolation, or the various means
by which species tend to be separated into sections which
do not interbreed.

Natural selection is a phrase descriptive of the course of
nature, of the survival of the fit and the elimination of the
unfit in the struggle for existence. It involves on the one
hand the survival, i.e. the nutritive and reproductive success
of the variations fittest to survive in given conditions, and
on the other hand the destruction or elimination of forms
less fit. Suitable variations pay ; nature or natural selection
justifies and fosters them. Maternal sacrifice or cunning
cruelty, the milk of animal kindness or teeth strong to
rend, distribution in space or rate of reproduction, are all
affected by natural selection. But it is another thing to say
that all the adaptations and well-endowed species that we
know have been produced by the action of natural selection
on fortuitous, indefinite variations. This is what Samuel
Butler calls the “ accredited fallacy.”

Secondly, there seem to be a great many ways by which
a species may be divided into two sections which do not
interbreed, and if this isolation be common it must help
greatly in divergent evolution.

Thus Romanes, who has been the chief exponent of the
importance of isolation, on which Gulick has also insisted,
says : “ Without isolation, or the prevention of free inter-
crossing, organic evolution is in no case possible. It is
isolation that has been ‘ the exclusive means of modifica-
tion,’ or more correctly, the universal condition to it.
Heredity and variability being given, the whole theory of
organic evolution becomes a theory of the causes and con-
ditions which lead to isolation.”

Secondary Factors. Primary Factors.

302

The Study of Animal Life part iv

SUMMARY OF EVOLUTION THEORIES.

Variations all ultimately due to External Influences.

Direct

action of the
environment
produces
environ-
mental
variations,

Organismal,
constitutional,
congenital,
or germinal
variations
may be either
definite or indefinite.

Use and
disuse and
change
of function
produce
functional
variations

wh
if trans

ich

missible,

(certainly

transmis-

sible).

wh
if trans

ich,

missible,

may

accumulate

as

environ-

mental

modifications

of

species.

All cases

By the
persistence
of the original
conditions
these may
grow into
new
species.

By natural
selection in
the struggle
for existence
these may
give rise to
new
species.

may

be affect

ed by

may

accumulate

as

functional

modi-

fications

of

species.

“ isolation.”

The process of natural selection will affect all cases, but is
less essential for those marked * .

Origin of Variations. Origin of Species.

CHAPTER XIX

THE INFLUENCE OF HABITS AND SURROUNDINGS

I. The Influence of Function — 2. The Influence of Surroundings —
3. Our own Environment

1. The Influence of Function. — A skilled observer can
often discern a man’s occupation from his physiognomy,
his shoulders, or his hands. In some unhealthy occupa-
tions the death-rate is three times that in others. Disuse
of such organs as muscles tends to their degeneration, for
the nerves which control them lose their tone and the
circulation of blood is affected ; while on the other hand
increased exercise is within certain limits associated with
increased development. A force de forger on devient
forgeroti.

If we knew more about animals we might be able to cite
many cases in which change of function produced change of
structure, but there are few careful observations bearing on
this question.

Even if we could gather many illustrations of the
influence of use and disuse on individual animals, we should
still have to find out whether the precise characters thus
acquired by individuals were transmissible to the offspring,
or whether any secondary effects of the acquired characters
were transmissible, or whether these changes had no effect
upon succeeding generations. As there are few facts to argue
from, the answers given to these questions are not reliable.

It is easy to find hundreds of cases in which the constant

3°4

PART IV

The Study of Animal Life

characters of animals may be hypothetically interpreted as
the result of use or disuse. Is the torpedo-like shape of
swift swimmers due to their rapid motion through the
water, do burrowing animals necessarily become worm-like,
has the giraffe lengthened its neck by stretching it, have
hoofs been developed by running on hard ground, are horns
responses to butting, are diverse shapes of teeth the results
of chewing diverse kinds of food, are cave-animals blind
because they have ceased to use. their eyes, are snails lop-
sided because the shell has fallen to one side, is the
asymmetry in the head of flat fishes due to the efforts made
by the ancestral fish to use its lower eye after it had formed
the habit of lying flat on the bottom, is the woodpecker’s
long tongue the result of continuous probing into holes, are
webbed feet due to swimming efforts, has the food-canal in
vegetarian animals been mechanically lengthened, do the
wing bones and muscles of the domesticated duck compare
unfavourably with those of the wild duck because the habit
of sustained flight has been lost by the former ?

But these interpretations have not been verified ; they
are only probable. “ It is infinitely easy,” Semper says,
“ to form a fanciful idea as to how this or that fact may be
hypothetically explained, and very little trouble is needed to
imagine some process by which hypothetical fundamental
causes — equally fanciful — may have led to the result which
has been actually observed. But when we try to prove by
experiment that this imaginary process of development is
indeed the true and inevitable one, much time and laborious
research are indispensable, or we find ourselves wrecked on
insurmountable difficulties.”

Not a few naturalists believe in the inherited effects
of functional change mainly because the theory is simple
and logically sufficient. If use and disuse alter the
structure of individuals, if the results are transmitted and
accumulate in similar conditions for generations, we require
no other explanation of many structures.

The reasons why not a few naturalists disbelieve in the
inherited effects of functional change are (i) that definite
proof is wanting, (2) that it is difficult to understand how

ch. xix Influence of Habits and Surroundings 305

changes produced in the body by use or disuse can be
transmitted to the offspring, (3) that the theory of the
accumulation of (unexplained) favourable variations in the
course of natural selection seems logically sufficient. 1
should suspend judgment, because it is unprofitable to argue
when ascertained facts are few.

But if you like to argue about probabilities, the following
considerations may be suggestive : —

The natural powers of animals — horses, dogs, birds, and
others — can be improved by training and education, and
animals can be taught tricks more or less new to them, but
we have no precise information as to any changes of
structure associated with these acquirements.

Individual animals are sometimes demonstrably affected
by use or disuse. Thus Packard cites a few cases in which
some animals — usually with normal eyes — have had these
affected by disuse and darkness ; he instances the variations
in the eyes of a Myriapod and an Insect living in partial
daylight near the entrance of caves, the change in the eyes
of the common Crustacean Gammarus pulex after confine-
ment in darkness, the fact that the eyes of some other
Crustaceans in a lake were smaller the deeper the habitat.

There are many more or less blind animals, and Packard
says “ no animal or series of generations of animals, wholly
or in part, can lose the organs of vision unless there is some
appreciable physical cause for it.” If so, it is probable that
the appreciable physical cause has been a direct factor in
producing the blindness.

Not a few young animals have structures, Such as eyes
and legs, which are not used and soon disappear in adult
life. Thus the little crab Pinnotheres^ which lives inside
bivalves and sea- cucumbers, keeps its eyes until it has
established itself within its host. Then they are completely
covered over and degenerate. The same is true of many
internal parasites, and Semper concludes that “ we must
refer the loss of sight to disuse of the organ.” Perhaps the
same is true of some blind cave-animals, in which the eyes
are less degenerate in the young, and of the mole, whose
embryos have between the eyes and the brain normal optic

X

PART IV

306 The Study of Animal Life

nerves which usually degenerate in each individual life-
time.

The theory that many structures in animals are due to
the inherited results of use and disuse has this advantage,
that it suggests a primary cause of change, whereas the
other theory assumes the occurrence of favourable variations
and proceeds to show how they might be accumulated in
the course of natural selection, that is to say by a secondary
factor in evolution.

When we find in a large number of entirely distinct
forms that the same habit of life is associated with the same
peculiarities, there is a likelihood that the habit is a direct
factor in evolving these. Thus sluggish and sedentary
animals in many different classes tend to develop skeletons
of lime, as in sponges, corals, sedentary worms, lamp-shells,
Echinoderms, barnacles, molluscs. Professor Lang has re-
cently made a careful study of sedentary creatures, and this
result at least is certain that the same peculiarity often occurs
in many different types with little in common except that
they are sedentary. But till one can show that sedentary life
necessarily involves for instance a skeleton of lime or some-
thing equivalent, we are still dealing only with probabilities.

2. The Influence of Surroundings. — In ancient times
men saw the threads of their life passing through the hands
of three sister-fates — of one who held the distaff, of another
who offered flowers, and of a third who bore the abhorred
shears of death. In Norseland the young child was visited by
three sister Noms, who brought characteristic gifts of past,
present, and "future, which ruled the life as surely as did
the hands of the three Fates. So too in days of scientific
illumination, we think of the dread three, but, clothing our
thoughts in other words, speak of life as determined by the
organism’s legacy or inheritance, by force of habit or
function, and by the influences of external conditions or
environment. What the living organism is to begin with,
what it does or does not in the course of its life, and what
surrounding influences play upon it, — these are the three
Fates, the three Noms, the three Factors of Life. Organ-
ism, function, and environment are the sides of the bio-

ch. xix Influence of Habits and Surroundings 307

logical prism. Thus we try to analyse the light of life. But
Inheritance in its widest sense is only another name for the
organism itself, and function is simply the organism’s activity.
The organism is real ; the environment is real, in it we live
and move ; function consists of action and reaction between
these two realities. Yet the capital which the organism
has to begin with is very important ; conduct has some
relation to character, and function to structure ; the sur-
roundings— the dew of earth and the sunshine of heaven
— silently mould the individual destiny.

A living animal is almost always either acting upon its
surroundings or being acted upon by them, and life is the
'relation between two variables — a changeful organism and
a changeful environment. And since animals do not and
cannot live in vacuo , they should be thought of in relation
to their surroundings. You may kill the body and cut it to
pieces, and the result may be interesting, but you have lost
the animal just as you lose a picture if you separate figure
from figure, and all from the associated landscape or interior.
The three Fates are sisters, they are thoroughly intelligible
only as a Trinity.

The most certain of all the relations between an organism
and its surroundings is the most difficult to express. We
see a small whirlpool on a river, remaining for days or
weeks apparently constant, with the water circling round
unceasingly, bearing the same flotsam of leaves and twigs.
But though the eddy seems the same for many days, it is
always changing, currents are flowing in and out ; it is the
constancy of the stream and its bed which produces the
apparent constancy of the whirlpool. So, in some measure,
is it with an animal in relation to its surroundings. Streams
of matter and energy are continually passing in and out.
Though we cannot see it with our eyes, the organism is
indeed a whirlpool. It is ever being unmade and remade,
and owes much of its apparent constancy to the’ fact that
the conditions in which it lives — the currents of its stream
— are within certain limits uniform.

But as we cannot understand the material aspects of an
animal’s life without considering the streams of matter and

3°8 The Study of Animal Life part iv

energy which pass in and out, neither can we understand
its higher life apart from its surroundings.

To attempt a natural history of isolated animals, whether
alive or dead, is like trying to study man apart from society.
For it is only when we know animals as they live and move
that we discover how clever, beautiful, and human they
are. Thus Gilbert White’s Selbor?ie is a natural history ; and
therefore we began our studies with the natural life of
animals — their competition and helpfulness, their adaptations
to diverse kinds of haunts, their shifts and tricks, their
industries and their loves.

At present, however, we have to do with the relation
between external and internal changes. We must find out
what the environment of an organism is, and what power it
has. In a smithy we see a bar of hot iron being hammered
into useful form. Around a great anvil are four smiths
with their hammers. Each smites in his own fashion as
the bar passes under his grasp. The first hammer falls,
and while the bar is still quivering like a living thing it
receives another blow. This is repeated many times till the
thing of use is perfected. By force of smiting one becomes
a smith, and by dint of blows the bar of iron becomes
an anchor. So is it with the organism. In its youth
especially, it comes under the influence of nature’s hammers ;
it may become fitter for life, or it may be battered out of
existence altogether. Let us try to analyse the various
environmental factors.

(a) Pressures. — First we may consider those lateral and
vertical pressures due to air or water currents and to
the gentle but potent force of gravity. The shriek of the
wind as it prunes the trees, the swish of the water as it
moulds the sponges and water-leaves, illustrate the tunes of
those pressure-hammers. Under artificial pressure embryos
have been known to broaden ; even the division of the egg is
affected by gravity ; water currents mould shells and corals.
The influence of want of room must also be noticed, for by
artificial overcrowding naturalists have slowed the rate of
development and reared dwarf broods ; and the rate of
human mortality sometimes varies with the size of the

ch. xix Influence of Habits and Surroundings 309

dwelling. It is difficult, however, to abstract the influence
of restricted space from associated abnormal conditions.

(b) Chemical Influences. — Quieter, but more potent, are
the chemical influences which damp or fan the fire of life,
which corrode the skin or drug the system, which fatten or
starve, depress or stimulate. Along with these we must
include that most important factor — food.

When a lighted piece of tinder is placed in a vessel
full of oxygen it burns more actively. Similarly, super-
abundance of oxygen makes insects jump, makes the
simplest animals more agile, and causes the “ phosphores-
cent ” lights of luminous insects to glow more brightly ;
and young creatures usually develop more or less rapidly
according as the aeration is abundant or deficient. The
most active animals — birds and insects — live in the air and
have much air in their bodies ; sluggish animals often live
where oxygen is scarce ; changes in the quality of the
atmosphere may have been of importance in the historical
evolution of animals. Fresh air influences the pitch of
human life, and lung diseases increase in direct ratio to
the amount of crowded indoor labour in an area.

By keeping tadpoles in unnatural conditions the usual
duration of the gilled stage may be prolonged for two or three
years. The well-known story of the Axolotl and the Ambly-
stonia is suggestive but not convincing of the influence of
surroundings. These two newt-like Amphibians differ slightly
from one another, in this especially that the Axolotl retains
its gills after it has developed lungs, while the Ambly stoma
loses them. Both forms may reproduce, and they were
originally referred to different genera. But some Axolotls
which had been kept with scant water in the Jar din des
Plantes in Paris turned into the Amblystoma form; the two
forms are different phases of the same animal. It was a
natural inference that the Axolotls were those which had
remained or had been kept in the water, the Amblystoma
forms were those which got ashore. But both kinds may
be found in the water of the same lake and the metamor-
phosis may take place in the water as well as on the shore.
For these and for other reasons this oft -told tale is not

3io

PART IV

The Study of Animal Life

cogent In another part of this book I have given examples
of the state of lifelessness which drought induces in some

Fig. 64. — Axolotl (in the water) and Amblystoma (on the land).

simple animals, and from which returning moisture can
after many days recall them.

Changes may also be due to the chemical composition
of the medium, as was established by the experiments of

Fig. 65. — Side view of male Artemia salina (enlarged).
(From Chambers’s Encyclof).)

Schmankewitsch on certain small Crustaceans. Among the
numerous species of the brine-shrimp Artemia , the most
unlike are A. salina and A. milhauscnii ; they differ in the

ch. xix Influence of Habits and Surroundings 31 1

shape and size of the tail and in the respiratory appendages
borne by the legs ; they are not found together, but live in
pools of different degrees of saltness. Now Schmankewitsch
took specimens of A. salina which live in the less salt water,

Fig. 66. — Tail-lobes of Arlemia salina (to the left) and of Artemia milhauscnii
(to the right) ; between these four stages in the transformation of the one into
the other. (From Chambers’s Encyclop. ; after Schmankewitsch.)

added salt gradually to the medium in which they were
living, and in the course of generations turned them into
A. milhausenii. He also reversed the process by freshening
the water little by little. Moreover, he accustomed A. salina
to entirely fresh water, and then found that the form had
changed towards that of a related genus, Branchipus. This
last step has been adversely criticised, but it is allowed that
one species of brine-shrimp was changed into another.

Many interesting experiments have been made on the
effect of chemical reagents on cells, but these are perhaps
of most interest to the student of drugs. Still the fact that
the form of a cell and its predominant phase of activity
may be entirely changed in this way is important, especially
when we remember that it was in single cells that life first
began, and is now continued. Even Weismann agrees with
Spencer’s conclusion that “ the direct action of the medium
was the primordial factor of organic evolution.”

To Claude Bernard, the main problem of evolution
seemed to be concerned with variations in nutrition :
“ devolution, c’est l’ensemble constant de ces alternatives
de la nutrition ; c’est la nutrition consideree dans sa
rdalit^, embrassde d’un coup d’ceil h travels le temps.”
John Hunter and others have shown how the walls of the

312 The Study of Animal Life part jv

stomach of gulls and other birds may be experimentally
altered by change of diet, and the same is seen in nature
when the Shetland gull changes from its summer diet of
grain to its winter diet of fish. The colours of birds’ feathers,
as in canaries and parrots, are affected by their food. A
slight difference in the quantity and quality of food deter-
mines whether a bee -grub is to become a queen or a
worker, royal diet evolving the reproductive queen, sparser
less rich diet evolving the more active but unfertile worker.
Abundant food favours the production of female offspring,
while sparser food tends to develop males. Thus, in frogs,
the proportion of the sexes is normally not very far from
equal ; in three lots of tadpoles an average of 5 7 per hun-
dred became females, 43 males. But Yung has shown that
the nutrition of the tadpoles has a remarkable influence on
the sex of the adults. In a set of which one half kept in
natural conditions developed into 54 females to 46 males,
the other half fed with beef had 78 females to 22 males.
In a second set of which one half left to themselves
developed 61 females to 39 males, the other half, fed with
fish, had 81 females to 19 males. Finally, in a third set,
of which one half in natural conditions developed 56 females
to 44 males, the other half, to which the especially nutritious
flesh of frogs was supplied, had no less than 92 females
to 8 males.

When food is abundant, assimilation active, and income
above expenditure, the animal grows, and at the limit of
growth in lower animals asexual multiplication occurs.
Checked nutrition, on the other hand, favours the higher
or sexual mode of multiplication. Thus the gardener
prunes the roots of a plant to get better flowers or repro-
ductive leaves. The plant-lice or Aphides, which infest
our pear-trees and rose-bushes, well illustrate the combined
influence of food and warmth. All through the summer,
when food is abundant and the warmth pleasant, the
Aphides enjoy prosperity, and multiply rapidly. For an
Aphis may bring forth young every few hours for days
together, so rapidly that if all the offspring of a mother
Aphis survived, and multiplied as she did, there would

CII. XIX Influence of Habits and Surroundings 313

in the course of a year be a progeny which would weigh
down 500,000,000 stout men. But all through the
summer these Aphides are wholly female, and therefore
wholly parthenogenetic ; no males occur. In autumn, how-
ever, when hard times set in, when food is scarcer,, and the
weather colder, males are born, parthenogenesis ceases,
ordinary sexual reproduction recurs. 'Moreover, if the
Aphides be kept in the artificial summer of a greenhouse,
as has been done for four years, the parthenogenesis con-
tinues without break, no males being born to enjoy the
comforts of that environment. Periods of fasting occur
in the life -history of many animals, and these are very
momentous and progressive periods in the lives of some,
for the tadpole fasts before it becomes a frog, and the
chrysalis before it becomes a butterfly. Lack of food, how-
ever, may stunt development, as we see every day in the
streets of our towns.

(c) Radiant Energy. — Of the forms of radiant energy
which play upon the organism, we need take account only
of heat and light, for of electrical and magnetic influence
the few strange facts that we know do not make us much
wiser.

We know that increased warmth hastens motion, the
development of embryos, and the advent of sexual maturity.
An Infusorian ( Stylonichia ) studied by Maupas was seen
to divide once a day at a temperature of 7°-io° C., twice
at io°-i5°, thrice at i5°-2o°, four times at 2o°-24°, five
times at 24°-27° C. At the last temperature one Infusorian
became in four days the ancestor of a million, in six days
of a billion, in seven days and a half of 100 billions, weigh-
ing 100 kilogrammes. By consummately patient experi-
ments, Ballinger was able to educate Monads which lived
normally at a temperature of 65° Fahr., until they could
flourish at 158° Fahr.

Cold has generally a reverse action, checking activity,
producing coma and lifelessness, diminishing the rate of
development, tending to produce dwarf or larva-like forms.
The cold of winter acting through the nervous system
changes the colour of some animals, like Ross’s lemming,

PART IV

3 1 4 The Study of Animal Life

to advantageous white. Not a few animals vary slightly
with the changing seasons. Thus many cases are known
where a butterfly produces in a year more than one brood,

Fig. 67. — Seasonal dimorphism of Pa/tilio ajax ; to the left the winter form
(variety Telainonides ), to the right the summer form (variety Marcellas).
(From Chambers’s Encyclop. ; after Weismann.)

of which the winter forms are so different from those born
in summer that they have often been described as different
species. It is possible that this is a reminiscence of past
climatic changes, such as those of the Ice Ages, as the

Fig. 68. — Seasonal changes of the bill in the puffin ( Fraicrcula arctic<i)\ to the
left the spring form, to the right the winter form, both adult males. (After
Bureau.)

result of which a species became split up into two varieties.
Thus Arasc/mia levana and Araschnia prorsa are respect-
ively the winter and summer forms of one species. In the

ch. xix Influence of Habits and Surroundings 315

glacial epoch there was perhaps only A. levana , the winter
form ; the change of climate has perhaps evolved the
summer variety A. prorsa. Both Weismann and Edwards
have succeeded, by artificial cold, in making the pupae which
should become the summer A.prorsa develop into the winter
A. levana. Nor can we forget the seasonal moulting and
the subsequent change of the plumage in birds, so marked
in the case of the ptarmigan, which moults three times in
the year. In the puffins even the bill is moulted and
appears very different at different seasons. But in these
last cases the influence of environment must be very
indirect.

Light is very healthful, but it is not easy to explain its
precise influence. Our pulses beat faster when we go out
into the sunlight. Plants live in part on the radiant
energy of the sun, and perhaps some pigmented animals do
the same. Perhaps the hundreds of eyes which some mol-
luscs have are also useful in absorbing the light. It is also
possible that light has a direct influence on the formation of
some animal pigments, as it seems to have in the develop-
ment of chlorophyll. We know, from Poulton’s experiments,
that the light reflected from coloured bodies influences the
colouring of caterpillars and pupae, but this influence seems
to be subtle and indirect, operating through the nervous
system. It is also certain that living in darkness tends to
bleach some animals, and 'it is probable that the absence
of light stimulus has a directly injurious effect upon the
eyes of those animals which live in caves or other dark
places. But I have already explained why dogmatism in
regard to these cases should be avoided.

One case of the influence of light seems veiy instructive.
It is well known that flat fishes like flounders, plaice, and
soles lie or swim in adult life on one side. This lower side
is unpigmented ; the upper side bears black and yellow
pigment-containing cells.

One theory of the presence of pigment on the upper
side and its absence on the other is that the difference is
a protective adaptation evolved by the natural selection of
indefinite variations. But it is open to question whether the

3 1 6 The Study of Animal Life part iv

characteristic is so advantageously protective as is usually
imagined : thus the coloured upper side in soles is very
often covered with a layer of sand. Soles come out most
at night, most live at depths at which differences of colour
are probably indistinct. In shallower water the advantage
is likely to be greater, though the white under-side slightly
exposed as the fish rises from the bottom may attract atten-
tion disadvantageous^. Moreover, if we find in a large
number of different animals that the side away from the
light is lighter than that which is exposed, and if we can
show that this has in many cases no protective advantage
whatever — and I believe that a few hours’ observation will
convince you that both my assumptions are correct — then
there is a probability that the absence of light has a direct
influence on the absence of pigment.

But we are not left to vague probabilities ; Mr. J. T.
Cunningham has recently made the crucial experiment of
illuminating the under sides of young flounders. Out of
thirteen, whose under-sides were thus illumined by a mirror
for about four months, only three failed to develop black
and yellow colour-cells on the skin of the under-sides. It
is therefore likely that the normal whiteness of the under-
sides is due in some way to the fact that in nature little light
can fall on them, for they are generally in contact with the
ground.

(d) Animate Surroundings. — We have given a few
instances showing how mechanical or molar pressures,
chemical and nutritive influences, and the subtler physical
energies of heat and light, affect organisms. There is a
fourth set of environmental factors — the direct influence of
organism upon organism. In a previous chapter we spoke
of the indirect influences different kinds of organisms exert
on one another, and these are most important, but there are
also results of direct contact.

Much in the same way as insects produce galls on
plants, so sea- spiders ( Pycnogonidce ) affect hydroids, a
polype deforms a sponge, a little worm ( Myzostoma ) makes
galls on Crinoids. Prof. Giard has described how certain
degenerate Crustaceans parasitic on crabs injuriously affect

cn. xix Influence of Habits and Surroundings 317

their hosts, and some internal parasites produce slight
modifications of structure. Interesting also are the shelters
or domatia of some plants, within which insects and mites
find homes.

We can speak more confidently about the influence of
surroundings than we could in regard to the influence of
use and disuse, because the ascertained facts are more
numerous. Those interested in the theoretical importance
of these facts should attend to the following considerations.

It is essential to distinguish between cases in which
we know that external conditions influence the organism
and those in which tve think they may have done so. Thus
it is probable that the degeneracy and other peculiarities of
many parasites are results of external influence and of
feeding, and also in part of disuse, but we cannot state
this as a fact.

Most of the observations on the influence of external
conditions give us no information as to the transmissi-
bility of the results. It is not enough to know that a
peculiarity observed to occur in peculiar surroundings was
observed to recur in successive generations living in the
same surroundings. For (1) it might be an indefinite
variation — a sport due to some germinal peculiarity —
which happened to suit. In such a case it would be
transmissible, but it would not be a change due to the
environment. And (2) even when it has been proved that
the peculiarity is due to the direct influence of the environ-
ment, and observed to recur in successive generations, still
its transmissibility is not proven, for it may be hammered
on each successive generation as it was on the first. We
can say little about the transmissibility or evolutionary
importance of changes of structure due to surroundings
because most of the observations were made before the
scepticism as to the inheritance of acquired characters
became dominant. Only in a few cases, such as that of the
brine-shrimps, was the cumulative influence traced through
many generations. In dearth of facts we should not be
confident, but eager for experiment.

Surroundings may influence the organism in varying

PART IV

3 1 8 The Study of Animal Life

degrees. There may be direct results, rapid parries after
thrusts, or the results may be indirect ; they may affect the
organism visibly in the course of one generation, or only
after several have passed.

Some animals are more susceptible and more plastic
than others. Young organisms, such as caterpillars and
tadpoles, are more completely in the grasp of their environ-
ment than are the adults. Thus Treviranus, who believed
very strongly in the influence of surroundings, distinguished
two periods of vita minima — -in youth and in old age —
during which external conditions press heavily, from the
period of vita maxima — in adult life — when the organism
is more free. To some kinds of influence, e.g. mechanical
pressures, passive and sedentary organisms such as sponges,
corals, shell-fish, and plants, are more susceptible than are
those of active life. And it is during a period of quiescence
that surrounding colour tells on the sensitive caterpillars.

3. Our own Environment. — The human organism, like
any other, may be modified by its environment, for we
lead no charmed life. Those external influences which
touch body and mind are to us the more important, since
we have them to some extent within our own hands, and
because our lives are relatively long. Even if the changes
thus wrought upon parents are not transmissible, it is to
some extent possible for us to secure that our children grow
up open to influences known to be beneficial, sheltered from
forces known to be injurious.

As the influence of surroundings is especially potent on
young things — such as caterpillars and tadpoles — all care
should be taken of the young child’s environment during
the earliest months and years, when the grip that externals
have is probably much greater than is imagined by those
who believe themselves emancipated from the tyranny of
the present.1

As passive organisms are more in the thrall of their
surroundings than are the more active, we feel the import-
ance of beauty in the home, that the organism may be

1 Cf. Matthew Arnold's poem, “ The Future,” and Walt Whitman's
“ Assimilations.”

ch. xix Influence of Habits and Surroundings 319

saturated with healthful influence during the periods in
which it is most susceptible. The efforts of Social Unions,
Kyrle Societies, Verschonerungs-Vereine, and the like, are
justified not only by their results,1 but by the biological
facts on which they more or less unconsciously depend.
There would be more progress and less invidious com-
parison of ameliorative schemes, if we realised more vividly
that the Fates are three. Though it is not easy to appre-
ciate the three sides of a prism at once, of what value is
liberty on an ash-heap, or equality in a hell, or fraternity
among an overpopulated community of weaklings ? Organ-
ism, function, and environment must evolve together, and
surely they shall.

Poets have often compared human beings to caterpillars ;
it may be that no improvement in constitutions, functions,
or surroundings will make us winged Psyches, yet it may be
possible for us to be ennobled like those creatures which in
gilded surroundings became golden. Surely art is warranted
by the results of science, as these in time may justify them-
selves in art.

1 Ideally stated in Emerson's well-known poem of “Art.”

CHAPTER XX

HEREDITY

i. The Facts of Heredity — 2. Theories of Heredity : theological,
vietaphysical, mystical, and the hypothesis of pangenesis —
3. The Modern Theory of Heredity — 4. The Inheritance of
Acquired Characters — 5. Social and Ethical Aspects — 6. Social
Inheritance

WE have spoken of the three Fates which were believed to
determine of what sort a life should be. With the decay
of poetic feeling, and in the light of common science, the
forms of the three sisters have faded. But they are realities
still, for men are thinking more and more vividly about the
factors of life, which to some are “powerful principles,”
to others living and personal, to others unnameable.
Biologists speak of them as Heredity, Function, and En-
vironment : the capital with which a life begins, the

interest accruing from the investment of this in varied vital
activities, and the force of circumstances. But while it is
useful to think of Heredity, Function, and Environment as
the three fates, we must not mystify matters by talking as
if these were entities acting upon the organism. They
are simply aspects of the fact that the animal is bom and
lives. The inheritance is the organism itself, and heredity
is only a name for the relation between successive genera-
tions. Moreover, the function of an organism depends
upon the nature of the organism, and so does its suscep-
tibility to influences from without.

I would at present define heredity as the organic relation

chap, xx Heredity 321

between successive generations, choosing this definition
because it is misleading to talk about “heredity” as a
“ basal principle in evolution,” as a “ great law,” as a
“ power,” or as a “ cause.” When I call heredity a
“ Fate,” it is plain that I speak fancifully, but “ principle”
and “ law” are dangerous words to play with. We cannot
think of life without this organic relation between parents
and offspring, and had species been created instead of being
evolved there would still be heredity.

i. The Facts of Heredity. —An animal sometimes
arises as a bud from its parent, and in rare cases from an
egg which requires no fertilisation, but apart from these
exceptions, every animal develops from an egg-cell with
which a male-cell has united in an intimate way. The
egg-cell supplies most of the living matter, but the nucleus
of the fertilised egg-cell is formed in half from the nucleus
of the immature ovum, in half from the nucleus of the
spermatozoon. Let us emphasise this first fact that each
parent contributes the same amount of nuclear material to
the offspring, and that this nuclear stuff is very essential.

Another fact is more obvious, the offspring is very like
its kind. One of the first things that people say about an
infant is that it is like its father or its mother, and the
assertion does not arouse any surprise, although the truer
verdict that the infant is like any other of the same race is
received with contempt. But every one admits that “ like
begets like.”

This likeness between offspring and parent is often far
more than a general resemblance, for peculiar features and
minute idiosyncrasies are frequently reproduced. Yet one
must not assume that because a child twirls his thumbs
in the same way as his father did the habit has been
inherited. For peculiar habits and structures may readily
reappear by imitation, or because the offspring grow up in
conditions similar to those in which the parents lived.

Abnormal as well as normal characters, “ natural ” to
the parents, may reappear in their descendants, and the list
of weaknesses and malformations which may be transmitted
is long and grim. But care is required to distinguish

Y

322

PART IV

The Study of Animal Life

between reappearance due to inheritance and reappearance
due to similar conditions of life.

Then there is a strange series of facts showing that an
organism may reproduce characteristics which the parents
did not exhibit, but which were possessed by a grandparent
or remoter ancestor. Thus a l;izard in growing a new
tail to replace one that has been lost has been known to
grow one with scales like those of an ancestral species. To
find out a lizard’s pedigree, a wit suggests that we need only
pull off its tail. When such ancestral resemblance in ordi-

Fig. 69. — Devonshire pony, showing the occasional occurrence of ancestral
stripes. (From Darwin.)

nary generation is very marked, we call it “ atavism ” or
“ reversion/’ but of this there are many degrees, and
abnormal circumstances sometimes force reversion even
upon an organism with a normal inheritance. A boy
“ takes after his grandfather ” ; a horse occasionally exhibits
stripes like those of a wild ancestor ; a blue pigeon like the
primitive rock-dove sometimes turns up unexpectedly in a
pure breed ; or a cultivated flower reverts to the simpler
and more normal wild type. So children born during
famine sometimes show reversions, and some types of
criminal and insane persons are to be thus regarded.

chap, xx Heredity 323

But every animal is usually a little different from its
parents, and except in cases of “identical twins” cannot be
mistaken for one of its fellow-offspring. The proverbial
“ two peas ” may be very unlike. Organisms are variable,
and this is natural, for life begins in the intimate
mingling of two units of living matter perhaps very dif-
ferent and certainly very complex. The relation between
successive generations is such that the offspring is like
its parents, but various causes producing change diminish
this likeness, so that we no longer say “ like begets like,”
but “ like tends to beget like.”

There are, I think, two other important facts in regard
to heredity, but both require discussion — the one because
some of the most authoritative naturalists deny it, the other
because it is difficult to understand.

I believe that some characters acquired by the parent as
the result of what it does, and as impacts from the surround-
ing conditions of life, are transmissible to the offspring. In
other words, some functional and environmental variations
in the body of the parents may be handed on to the
offspring. This is denied by Weismann and many others.

The other fact, which has been elucidated by Galton,
is that through successive generations there is a tendency
to sustain the average of the species, by the continual
approximation of exceptional forms towards a mean.

2. Theories of Heredity — historical retrospect. —
Theories of heredity, like those about many other facts,
have been formulated at different times in different kinds
of intellectual language — theological, metaphysical, and
scientific — and the words are often more at variance than
the ideas.

(a) Theological Theories. — It was an old idea, that the
germ of a new human life was possessed by a spirit, some-
times of second-hand origin, having previously belonged to
some ancestor or animal. So far as this idea persists in the
minds of civilised men, it is so much purified and sublimed
that if the student of science does not believe it true,
he cannot wisely call it false.

(b) “ Metaphysical Theories — F or a time it was com-

PART IV

324 The Study of Animal Life

mon to appeal to “ vires formativa ,” “ hereditary tendencies,”
and “ principles of heredity,” by aid of which the germ
grew into the likeness of the parent, and this tendency
to resort to verbal explanations is hardly to be driven from
the scientific mind except by intellectual asceticism. For
my own part, I prefer such “metaphysical” mist to the
frost of a “materialism” which blasts the buds of wonder.

< [c ) “ Mystical Theories .” — During the eighteenth cen-
tury and even within the limits of the enlightened nineteenth,
a quaint idea of development prevailed, according to which
the germ (either the ovum or the sperm) contained a miniature
organism, preformed in all transparency, which only required
to be unfolded (or “ evolved,” as they said), in order to
become the future animal. Moreover, the egg of a fowl
contained not only a micro-organism or miniature model of
the chick, but likewise in increasing minuteness similar
models of future generations. Microcosm lay within micro-
cosm, germ within germ, like the leaves within a bud
awaiting successive unfolding, or like an infinite juggler’s
box to the “ evolution ” of which there was no end. This
“ preformation theory” or “ mystical hypothesis ” was virtu-
ally but not actually shattered by Wolff’s demonstration of
“ Epigenesis ” or gradual development from an apparently
simple rudiment. But the preformationists were right in
insisting that the future organism lay (potentially) within
the germ, and right also in supposing that the germ involved
not only the organism into which it grew but its descendants
as well. The form of their theory, however, was crude and
false.

(d) Theories of Pangenesis. — Scientific theories of here-
dity really begin with that of Herbert Spencer, who in
1864 suggested that “physiological units” derived from
and capable of growth into cells were accumulated from the
body into the reproductive elements, there to develop the
characters of structures like those whence they arose. At
dates so widely separate as are suggested by the names of
Democritus and Hippocrates, Paracelsus and Bufifon, the
same idea was expressed — that the germs consist of samples
from the various parts of the body. But the theories of

chap, xx Heredity 325

these authors were vague and in some respects entirely
erroneous suggestions. The best-known form of this type
of theory is Darwin’s “ provisional hypothesis of pan-
genesis ” (1868), according to which (a) every cell of the
body, not too highly differentiated, throws off characteristic
gemmules, which ( b ) multiply by fission, retaining their
peculiarities, and ( c ) become specially concentrated in the
reproductive elements, where ( d ) in development they grow
into cells like those from which they were originally given
off. This theory was satisfactory in giving a reasonable
explanation of many of the facts of heredity, it was unsatis-
factory because it involved many unverified hypotheses.

The ingenious Jeeger, well known as the introducer of
comfortable clothing, sought (1876) to replace the “gem-
mules ” of which Darwin spoke, by characteristic “ scent-
stuffs,” which he supposed to be collected from the body
into the reproductive elements.

Meanwhile (1872) Francis Galton, our greatest British
authority on heredity, had been led by his experiments
on the transfusion of blood and by other considerations
to the conclusion that “ the doctrine of pangenesis, pure
and simple, is incorrect.” As we shall see, he reached
forward to a more satisfactory doctrine, but he still allowed
the possibility of a limited pangenesis to account for those
cases which suggest that some characters acquired by the
parents are “ faintly heritable.” He admitted that a cell
“may throw off a few germs” (i.e. “gemmules”) “that
find their way into the circulation, and have thereby a
chance of occasionally finding their way to the sexual
elements, and of becoming naturalised among them.”

W. K. Brooks, a well-known American naturalist, pro-
posed in 1883 an important modification of Darwin’s theory,
especially insisting on the following three suppositions :
that it is in unwonted, and abnormal conditions that the cells
of the body throw off gemmules ; that the male elements
are the special centres of their accumulation ; and that the
female cells keep up the general resemblance between
offspring and parents. For further modifications and for
criticism of the theories of pangenesis, I refer the student

326 The Study of Animal Life part iv

to the works of Galton, Ribot, Brooks, Herdman, Plarre,
Van Bemmelen, and De Vries.

3. The Modern Theory of Heredity. — In the midst of
much debate it may seem strange to speak of the modern
theory of heredity, but while details are disputed, one clear
fact is generally acknowledged, the increasing realisation of
which has shed a new light on heredity. This fact is the
organic continuity of generations.

In 1876 Jaeger expressed his views explicitly as follows :
“ Through a long series of generations the germinal proto-
plasm retains its specific properties, dividing in develop-
ment into a portion out of which the individual is built up,
and a portion which is reserved to form the reproductive
material of the mature offspring.” This reservation, by
which some of the germinal protoplasm is kept apart, during
development and growth, from corporeal or external influ-
ences, and retains its specific or germinal characters intact
and continuous with those of the parent ovum, Jaeger
regarded as the fundamental fact of heredity.

Brooks (1876, 1877, 1883) was not less clear: “The
ovum gives rise to the divergent cells of the organism, but
also to cells like itself. The ovarian ova of the offspring
are these latter cells or their direct unmodified descendants.
The ovarian ova of the offspring thus share by direct
inheritance all the properties of the fertilised ova.”

But before and independently of either Jaeger or Brooks
or any one else, Galton had reached forward to the same
idea. We have noticed that he was led in 1872 to the
conclusion that “ the doctrine of pangenesis, pure and
simple, is incorrect.” His own view was that the fertilised
ovum consisted of a sum of germs, gemmules, or organic
units of some kind, to which in entirety he applied the
term stirp. But he did not regard this nest of organic
units as composed of contributions from all parts of the
body. He regarded it as directly derived from a previous
nest, namely, from the ovum which gave rise to the parent.
He maintained that in development the bulk of the stirp
grew into the body — as every one allows — but that a cer-
tain residue was kept apart from the development of the

chap, xx Heredity 327

“ body ” to form the reproductive elements of the offspring.
Thus he said, in a sense the child is as old as the parent,
for when the parent is developing from the ovum a residue
of that ovum is kept apart to form the germ-cells, one of
which may become a child. Besides Galton, Jaeger, and
Brooks, several other biologists suggested this fertile idea
of the organic continuity of generations. Thus it is ex-
pressed by Erasmus Darwin and by Owen, by Haeckel,
Rauber, and Nussbaum. But it is to Weismann that the
modern emphasis on the idea is chiefly* due.

Let us try to realise more vividly this doctrine of organic
continuity between generations. Let us begin with a fertil-
ised egg-cell, and suppose it to have qualities abcxyz. This
endowed egg- cell divides and redivides, and for a short
time each of the units in the ball of cells may be regarded
as still possessed of the original qualities abcxyz. But
division of labour, and rearrangement, infolding and out-
folding, soon begin, and most of the cells form the “body.”
They lose their primitive characters and uniformity, they
become specialised, the qualities ab predominate in one
set, be in another, xy in another. But meantime certain
cells have kept apart from the specialisation which results
in the body. They have remained embryonic and un-
differentiated, retaining the many-sidedness of the original
egg-cell, preserving intact the qualities abcxyz. They form
the future reproductive cells — let us say the eggs.

Now when these eggs are liberated, with the original
qualities abcxyz unchanged, having retained a continuous
protoplasmic tradition with the parent ovum, they are evi-
dently in almost the same position as that was. There-
fore they develop into the same kind of organism. Given
the same protoplasmic material, the same inherent quali-
ties, the same conditions of birth and growth, the results
must be the same. A single-celled animal with qualities
abcxyz divides into two ; each has presumably the qualities
of the original unit ; each grows rapidly into the form of
the full-grown cell. We have no difficulty in understanding
this. In the sexual reproduction of higher animals, the
case is complicated by the formation of the “body,” but

32S The Study of Animal Life part iv

logically the difficulty is not greater. A fertilised egg-cell
with qualities abcxyz divides into many cells, which, becom-
ing diverse, express the original qualities in various kinds
of tissue within the forming body. But if at an early stage
certain cells are set apart, retaining the qualities or charac-
ters abcxyz in all their entirety, then these, when liberated
after months or years as egg-cells, will resemble the original
ovum, and are able like it to give rise to an organism,
which is necessarily a similar organism.

To call heredity “the relation of organic continuity
between successive generations,” as I define it, seems a
truism to some, but it is in the realisation of this truistic
fact that the modern progress in regard to heredity consists.

To ask how the inherent qualities of the ovum become
divergent in the different cells of the body, or how some
units remain embryonic, or how the egg-cell divides at
all, is to raise the deepest problems of biology, not of
heredity. To answer such questions is the more or less
hopeless task of physiological embryology, not that of the
student of heredity. Recognising the fact of organic con-
tinuity, various writers such as Samuel Butler, Hering,
Haeckel, Geddes, Gautier, and Berthold, have sought in
various ways to make it clearer, e.g. by regarding the re-
production of like by like as an instance of organic memory7.
As these suggestions are unessential to our argument, I
shall merely notice that there are plenty of them.

How far has this early separation of the future repro-
ductive cells from the developing body been observed ? It
has been observed in several worm-types — leeches, Sagitta ,
thread-worms, Polyzoa, — in some Arthropods (e.g. Moina
among crustaceans, CJtirononius among Insects, Phalangidre
among spiders), and with less distinctness in a number of
other organisms, both animal and vegetable. In most of
the higher animals, however, the future reproductive cells
are not observable till development has proceeded for some
days or weeks. To explain this difficulty7, Weismann has
elaborated a theory which he calls “ the continuity of the
germ-plasmaP The general idea of this theory is that of
organic continuity between generations, and this Weismann

chap, xx Heredity 329

has done momentous service in expounding. But for the
detailed theory by which he seeks to overcome the diffi-
culty which has been noticed above I refer those interested
to Weismann’s Papers on Heredity (Trans. Oxford, 1889).

4. The Inheritance of Acquired Characters. — (a) His-
torical.— We have seen that variations, or changes in char-
acter, may be constitutional , i.e. innate in the germ ■ or
functional , i.e. due to use or disuse ; or environmental , i.e.
due to influences of nutrition and surroundings. Many
naturalists have believed that gains or losses due to any of
these three sources of change might be transmitted from
parent to offspring. But nowadays the majority, with
Profs. Weismann and Lankester at their head, deny the
transmissibility of either functional or environmental
changes, and believe that inborn, germinal, or constitu-
tional variations alone are transmissible.

This scepticism is not strictly modern. The editor,
whoever he was, of Aristotle’s Historia Animalium , differed
from his master as to the inheritance of injuries and the
like. Kant maintained the non -inheritance of extrinsic
variations, and Blumenbach cautiously inclined to the same
negative position. In more recent times the veteran morpho-
logist His expressed a strong conviction against the inherit-
ance of acquired characters, and the not less renowned
physiologist Pfliiger is also among the sceptics. A few
sentences from Galton (1875), whose far-sightedness has
been insufficiently acknowledged, may be quoted : “ The
inheritance of characters acquired during the lifetime of the
parents includes much questionable evidence, usually diffi-
cult of verification. We might almost reserve our belief
that the structural cells can react on the sexual elements at
all, and we may be confident that at the most they do so in
a very faint degree — in other words, that acquired modifica-
tions are barely, if at all, inherited in the correct sense of
that word.”

But Weismann brought the discussion to a climax by
altogether denying the transmissibility of acquired charac-
ters.

(l>) Weismann’s position. — Weismann’s reasons for

33°

PART IV

The Study of Animal Life

maintaining that no acquired characters are transmissible
are twofold,— first because the evidence in favour of such
transmission consists of un verifiable anecdotes ; second
because the “ germ -plasma,” early set apart in the de-
velopment of the body, remains intact and stable, unaffected
by the vicissitudes which beset the body.

It is natural that Weismann, who realised so vividly the
continuity between germ and germ, should emphasise the
stability of the “germ-plasma,” that he should regard it
as leading a sort of charmed life within the organism un-
affected by changes to which the body is subject. But has
he not exaggerated this insulation and stability ?

Of course Weismann does not deny that the body may
exhibit functional and environmental variations, but he
denies that these can spread from the body so as to affect
the reproductive cells thereof, and unless they do so, they
cannot be transmitted to the offspring.

On the other hand, innate or germinal characters
must be transmitted. They crop up in the parent be-
cause they are involved in the fertilised egg-cell. But as
the cell which gives rise to the offspring is by hypothesis
similar to and more or less directly continuous with the
cell which gave rise to the parent, similar constitutional
variations will crop up in the offspring.

We must admit that most of the old evidence adduced
in favour of the transmission of acquired characters may
be called a “handful of anecdotes.” For scepticism was
undeveloped, and when a character acquired by a parent
reappeared in the offspring, it was too readily regarded as
transmitted, whereas it may often have been acquired by
the offspring just as it was by the parent.

Weismann has two saving clauses, which make argu-
ment against his position peculiarly difficult. (i) He
admits that the germ-plasma may be modified “ever so
little ” by changes of nutrition and growth in the body ;
but may not an accumulation of many “ ever- so Tittles ”
amount to the transmission of an acquired character ? (2)

Fie admits that external conditions, such as climate, may
influence the reproductive cells along with , though not

chap, xx Heredity 331

exactly through , the body ; but this is a distinction too
subtle to be verified.

These two saving-clauses seem to me to affect the strin-
gency of Weismann’s conclusion, but in his view they do
not affect the main proposition that definite somatic modifi-
cations or changes in the body due to function or environ-
ment have no effect on the reproductive cells, and therefore
no transmission to offspring.

(c) Arguments against Weismann’s position. — In arguing
against Weismann’s position that no acquired characters
are inherited, I shall first illustrate the arguments of others,
and then emphasise that which appears to me at present
most cogent.

(1) Some have cited against Weismann various cases
where the effects of mutilation seemed to be transmitted,
and Weismann has spent some time in experimenting with
mice in order to see whether cutting off the tails for several
generations did not eventually make the tails shorter. It
did not — a result which might have been foretold. For we
have known for many years that the mutilations inflicted
on sheep and other domesticated animals had no measur-
able effect on the offspring. Even the numerous cases of
tailless kittens produced from artificially curtailed cats have
no cogency in face of the fact that tailless sports often arise
from normal parents. Moreover, it is for many reasons not
to be expected that the results of curtailment and the like
should be inherited. For there is great power of regener-
ating lost parts even in the individual lifetime ; the result
of cutting off a tail is for most part merely a minus quantity
to the organism ; the imperfectly known physiological re-
action on nerves and blood-vessels might perhaps result in
a longer rather than a shorter tail in the offspring.

(2) Various pathologists, led by Virchow, have empha-
sised the fact that many diseases are inherited, but their
arguments have usually shown how easy it is to misunder-
stand Weismann’s position. No doubt many malformations
and diseases reappear through successive generations, but
there is lack of evidence to show that the pathological
variations were not germinal to begin with. It is sadly

332

FART IV

The Study of Animal Life

interesting to learn that colour-blindness has been known
to occur in the males only of six successive generations,
deaf mutism for three, finger malformations for six, and so
with harelip and cleft palate, and with tendencies to con-
sumption, cancer, gout, rheumatism, bleeding, and so on.
But these facts do not prove the transmission of functional or
environmental variations ; they only corroborate what every
one allows, that innate, congenital, constitutional characters

Fig. 70. — Half-lop rabbit, an abnormal variation, which by artificial selection
has become constant in a breed. (From Darwin.)

tend to be transmitted. Yet some cases recently stated by
Prof. Bertram Windle seem to suggest that some patho-
logical conditions acquired by function may be transmitted.
But even if a non-constitutional pathological state acquired
by a parent reappeared in the offspring, we require to show
that the offspring did not also acquire it by his work or
from conditions of life, as his parent did before him.

(3) Some individual cases seem to stand some criticism.

Two botanists, Hoffmann and Detmer, have noted such
facts as the following — scant nutrition influenced the flowers
of poppy, Nigella, dead-nettle, and the result was trans-

chap, xx Heredity 333

mitted ; peculiar soil conditions altered the root of the
carrot, and the result was transmitted.

Semper gives a few cases such as Schmankewitsch’s
transformation of one species of brine-shrimp ( Artemia ) into
another, throughout a series of generations during which
the salinity of the water was slowly altered.

Eimer has written a book of which even the title, “ The
Origin of Species, according to the laws of organic growth,
through the inheritance of acquired characters,” shows how
strongly he supports the affirmative side of our question.
But much as I admire and agree with many parts of Eimer’s
work, I do not think that all his examples of the inheritance
of acquired characters are cogent. One of the strongest
is that cereals from Scandinavian plains transplanted to
the mountains become gradually accustomed to develop
more rapidly and at a lower temperature, and that when
returned to the plains they retain this power of rapid
development. I am inclined to think that the strongest
part of Eimer’s argument is that in which he maintains that
certain effects produced upon the nervous system by peculiar
habits are transmissible.

(4) Another mode of argument may be considered. To
what conception of evolution are we impelled if we deny
the inheritance of acquired characters ? Weismann believes
that he has taken the ground from under the feet of
Lamarckians and Buffonians, who believe in the inheritance
of functional and environmental variations. The sole fount
of change is to be found in the mingling of the kernels of
two cells at the fertilisation of the ovum. On these varia-
tions natural selection works.

But even if we do not believe in the inheritance of
acquired characters, it is open to us to maintain that by
cumulative constitutional variations in definite directions
species have grown out of one another in progressive evolu-
tion. Thus we are not forced to restrict our interpreta-
tions of the marvel and harmony of organic nature to the
theory of the action of natural selection on indefinite for-
tuitous variations.

Prof. Ray Lankester’s convictions on this subject are so

334 The Study of Animal Life part iv

strong, and his dismissal of Lamarckian theory is so
emphatic, that I shall select one of his illustrations by way
of contrasting his theory with that of Lamarckians.

Many blind fishes and crustaceans are found in caves.
Lamarckians assume, as yet with insufficient evidence, that
the blindness is due to the darkness and to the disuse
of the eyes. Changes thus produced are believed, again
with insufficient evidence, to be transmitted and increased,
generation after generation. This is a natural and simple
theory, but it is not a certain conclusion.

What is Prof. Ray Lankester’s explanation ?

“ The facts are fully explained by the theory of natural
selection acting on congenital fortuitous variations. Many
animals are born with distorted or defective eyes whose
parents have not had their eyes submitted to any peculiar
conditions. Supposing a number of some species of Arthro-
pods or fish to be swept into a cavern, those individuals with
perfect eyes would follow the glimmer of light and eventually
escape to the outer air, leaving behind those with imperfect
eyes to breed in the dai'k place. In every succeeding
generation this would be the case, and even those with
weak but still seeing eyes would in the course of time
escape, until only a pure race of eyeless or blind animals
would be left in the cavern.” This is a possible explanation,
but it is not a certain conclusion.

(5) The argument which I would urge most strongly is
based on general physiological considerations. It gives
no demonstration, but it seems to establish a presump-
tion against Weismann’s conclusion. He maintains that
functional and environmental changes in the body cannot
be transmitted because such changes cannot reach the
stable and to some extent insulated reproductive elements.
But this cannot requires proof, just as much as the converse
can.

The organism is a unity ; cell is often linked to cell by
bridges of living matter ; the blood is a common medium
carrying food and waste ; nervous relations bind the whole
in harmony. Would it not be a physiological miracle if the
reproductive cells led a charmed life unaffected even by

ciiAr. xx Heredity 335

influences which touch the very heart of the organism ? Is
it unreasonable to presume that some influences of habit and
conditions, of training and control, saturate the organism
thoroughly enough to affect every part of it ?

A slight change of food affects the development of the
reproductive organs in a bee-grub, and makes a queen out of
what otherwise would have been a worker. A difference of
diet causes a brood of tadpoles to become almost altogether
female. There is no doubt that some somatic changes
affect the reproductive cells in some way. Is it incon-
ceivable that they affect them in such a precise way that
bodily changes may be transmitted ?

It must be admitted that it is at present impossible to
give an explanation of the way in which a modification
of the brain can affect the cells of the reproductive organs.
The only connections that we know are by the blood, by
nervous thrills, by protoplasmic continuity of cells. But
there are many indubitable physiological influences which
spread through the body of which we can give no rationale.
Because we cannot tell how an influence spreads, we need
not deny its existence.

It is at least conceivable that a deep functional or
environmental change may result in chemical changes
which spread from cell to cell, that characteristic products
may be carried about by the blood and absorbed by the
unspecialised reproductive cells, that nervous thrills of
unknown efficacy may pass from part to part. Nor do we
expect that more than a slight change will be transmitted
in one generation.

Weismann traces all variations ultimately to the action
of the environment on the original unicellular organisms.
These are directly affected by surrounding influences, and
as they have no “ body ” nor specialised reproductive
elements, but are single cells, it is natural that the char-
acters acquired by a parent-cell should also belong to the
daughter-units into which it divides. And if so, is it not
possible that the reproductive cells of higher animals, being
equivalent to Protozoa, may be definitely affected by their
immediate environment, the body ? Moreover, if it were

336

PART IV

The Study of Animal Life

proved that the definite changes produced on an individual
by influences of use, disuse, and surroundings, do not reach
the reproductive cells, and cannot, therefore, be transmitted,
it is not thereby proved that secondary results or some results
of such definite changes may not have some effect on the
germ-cells. The conditions are so complex that it seems
rash to deny the possibility of such influence.

* Certainly it is no easy task to explain all the adapta-
tions to strange surroundings and habits, or the majority of
animal instincts,, or the progress of men, apart from the
theory that some of the results of environmental influence
and habitual experience are transmitted. I am certainly
unable to reconcile myself to the opinion that the progress
of life is due to the action of natural selection on fortuitous,
indefinite, spontaneous variations.

I believe that the conclusion of the whole matter should
be an emphatic “not proven” on either side, -while the
practical corollary is that we should cease to talk so much
about possibilities (in regard to which one opinion is often
as logically reasonable as another), and betake ourselves
with energy to a study of the facts.

5. Social and Ethical Aspects. — All the important
biological conclusions have a human interest.

The fact of organic continuity between germ and germ
helps us to realise that the child is virtually as old as the
parent, and that the main line of hereditary connection
is not so much that between parent and child as “that
between the sets of elements out of which the personal
parents had been evolved, and the set out of which the
personal child was evolved.” “ The main line,” Galton
says, “ may be rudely likened to the chain of a necklace,
and the personalities to pendants attached to the links.”
To this fact social inertia is largely due, for the organic
stability secured by germinal continuity tends to hinder
evolution by leaps and bounds either forwards or backwards.
There is some resemblance between the formula of heredity
and the first law of motion. The practical corollary is
respect for a good stock.

That each parent contributes almost equally to the off-

chap, xx Heredity 337

spring suggests the two-sided responsibility of parentage ;
but the fact has to be corrected by Gabon’s statistical con-
clusion that the offspring inherits a fourth from each
parent, and a sixteenth from each grandparent ! Inherited
capital is not merely dual, but multiple like a mosaic.

If we adopt a modified form of Weismann’s conclusion,
and believe that only the more deeply penetrating acquired
characters are transmitted, we are saved from the despair
suggested by the abnormal functions and environments of
our civilisation.

And just in proportion as we doubt the transmission of
desirable acquired characters, so much the more should we
desire to secure that improved conditions of life foster the
individual development of each successive generation.

That pathological conditions, innate or 'congenital in the
organism, tend to be transmitted, suggests that men should
be informed and educated as to the undesirability of
parentage on the part of abnormal members of the com-
munity.

But while no one will gainsay the lessons to be drawn
from the experience of past generations, it should be noticed
that Virchow and others have hinted at an “ optimism of
pathology,” since some of the less adequately known abnor-
mal variations may be associated with new beginnings not
without promise of possible utility. It seems, moreover,
that by careful environment and function, or by the inter-
crossing of a slightly tainted and a relatively pure stock, a
recuperative or counteractive influence may act so as to
produce comparatively healthy offspring, thus illustrating
what may be called “the forgiveness of nature.”

6. Social Inheritance. — The widest problems of
heredity are raised when we substitute “ fraternities ” for
individuals, or make the transition to social inheritance —
the relation between the successive generations of a society.

The most important pioneering work is that of Galton,
whose unique papers have been recently summed up in a
work entitled Natural Inheritance. Galton derived his
data from his Records of Family Faculties , especially con-
cerning stature, eye-colour, and artistic powers ; and his

z

338 The Study of Animal Life part iv

work has been in great part an application of the statistical
law of Frequency of Error to the records accumulated.

The main problem of his work is concerned with the
strange regularity observed in the peculiarities of great
populations throughout a series of generations. “ The
large do not always beget the large, nor the small the
small ; but yet the observed proportion between the large
and the small, in each degree of size and in every quality
hardly varies from one generation to another.” A specific
average is sustained. This is not because each individual
leaves his like behind him, for this is not the case. It is
rather due to the fact of a regular regression or deviation
which brings the offspring of extraordinary parents in a
definite ratio nearer the average of the stock.

“ However paradoxical it may appear at first sight, it is
theoretically a necessary fact, and one that is clearly con-
firmed by observation, that the stature of the adult offspring
must on the whole be more mediocre than the stature of
their parents — that is to say, more near to the median
stature of the general population. Each peculiarity of a
man is shared by his kinsmen, but 071 an average in a less
degree. It is reduced to a definite fraction of its amount,
quite independently of what its amount might be. The
fraction differs in different orders of kinship, becoming
smaller as they are more remote.”

Yet it must not be supposed that the value of a good stock
is under-estimated by Galton, for he shows how the offspring
of two ordinary members of a gifted stock will not regress
like the offspring of a couple equal in gifts to the former,
but belonging to a poorer stock, above the average of which
they have risen.

Yet the fact of regression tells against the full transmission
of any signal talent. Children are not likely to differ from
mediocrity so widely as their parents. “ The more bounti-
fully a parent is gifted by nature, the more rare will be his
good fortune if he begets a son who is as richly endowed as
himself, and still more so if he has a son who is endowed
more largely.” But “The law is even-handed ; it levies an
equal succession -tax on the transmission of badness as of

chap, xx Heredity 339

goodness. If it discourages the extravagant hope of a gifted
parent that his children will inherit all his powers, it no less
discountenances extravagant fears that they will inherit all
his weakness and disease.”

The study of individual inheritance, as in Galton’s
Hereditary Genius, may tend to develop an aristocratic and
justifiable pride of race when a gifted lineage is verifiable
for generations. It may lead to despair if the records of
family diseases be subjected to investigation.

But the study of social inheritance is at once more demo-
cratic and less pessimistic. The nation is a vast fraternity,
with an average towards which the noble tend, but to which
the offspring of the under-average as surely approximate.
Measures which affect large numbers are thus more hopeful
than those which artificially select a few.

Even when we are doubtful as to the degree in which
acquired characters are transmissible, we cannot depreciate
the effect on individuals of their work and surroundings.
In fact there should be the more earnestness in our desire to
conserve healthful function and stimulating environment of
every kind, for these are not less important if their influences
must needs be repeated on each fresh generation. “ There
was a child went forth every day ; and the first object he
looked upon, that object he became ; and that object
became part of him for the day, or a certain part of the
day, or for many years, or for stretching cycles of years.” 1

Nor can we forget how much a plastic physical and
mental education may do to counteract disadvantageous
inherited qualities, or to strengthen characters which are
useful.

Every one will allow at least that much requires to be
done in educating public opinion, not only to recognise all
the facts known in regard to heredity, but also to admit the
value and necessity of the art which Mr. Galton calls
“ eugenics,” or in frank English “ good-breeding.”

1 Walt Whitman’s "Assimilations.”

APPENDIX 1

ANIMAL LIFE AND OURS

A. Our Relation to Animals

i. Affinities and Differences between Man and Monkeys.

In one of the works of Broca, a pioneer anthropologist of renown,
there is an eloquent apology for those who find it useful to con-
sider man’s zoological relations.

“ Pride,” he says, “ which is one of the most characteristic traits
of our nature, has prevailed with many minds over the calm testi-
mony of reason. Like the Roman emperors who, enervated by all
their power, ended by denying their character as men, in fact, by
believing themselves demigods, so the king of our planet pleases
himself by imagining that the vile animal, subject to his caprices,
cannot have anything in common with his peculiar nature. The
proximity of the monkey vexes him, it is not enough to be king of
animals ; he wishes to separate himself from his subjects by a deep
unfathomable abyss ; and, turning his back upon the earth, he takes
refuge with his menaced majesty in a nebulous sphere, ‘ the human
kingdom.’ But anatomy, like that slave who followed the con-
queror’s chariot crying, Mei?iento te hominem esse , anatomy comes
to trouble man in his naive self-admiration, reminding him of the
visible tangible facts which bind him to the animals.”

Let us hearken to this slave a little, remembering Pascal’s
maxims : “ It is dangerous to show man too plainly how like he is
to the animals, without, at the same time, reminding him of his
greatness. It is equally unwise to impress him with his greatness,
and not with his lowliness. It is worse to leave him in ignorance
of both. But it is very profitable to recognise the two facts. ”

It is many years since Owen — now a veteran among anatomists
—described the “all-pervading similitude of structure” between

APP. I

341

Animal Life, and Ours

man and the highest monkeys. Subsequent research has continued
to add corroborating details. As far as structure is concerned,
there is much less difference between man and the gorilla than
between the gorilla and a monkey like a marmoset. Yet differences
between man and the anthropoid apes do exist. Thus man alone
is thoroughly erect after his infancy is past, his head weighted with
a heavy brain does not droop forward, and with his erect attitude
his perfect development of vocal mechanism is perhaps connected.
We plant the soles of our feet flat on the ground, our great toes
are usually in a line with the rest, and we have better heels than
monkeys have, but no emphasis can be laid on the old distinction
which separated two-handed men (Bimana) from the four-handed
monkeys (Quadrumana), nor on the fact that man is peculiarly
naked. We have a bigger forehead, a less protrusive face, smaller
cheek-bones and eyebrow ridges, a true chin, and more uniform
teeth than the anthropoid apes. More important, however, is the
fact that the weight of the gorilla’s brain bears to that of the smallest
brain of an adult man the ratio of 2 : 3, and to the largest human
brain the ratio of 1 : 3 ; in other words, a man may have a brain
three times as heavy as that of a gorilla. The brain of a healthy
human adult never weighs less than 31 or 32 ounces ; the average
human brain weighs 48 or 49 ounces ; the heaviest gorilla brain
does not exceed 20 ounces. “The cranial capacity is never less
than 55 cubic inches in any normal human subject, while in the
orang and the chimpanzee it is but 26 and 27J cubic inches
respectively. ”

But differences which can be measured and weighed give us little
hint of the characteristically human powers of building up ideas and
of cherishing ideals. It is not merely that man profits by his
experience, as many animals do, but that he makes some kind of
theory of it. It is not merely that he works for ends which are
remote, as do birds and beavers, but that he controls his life
according to conscious ideals of conduct. But I need not say much
in regard to the characteristics of human personality, we are all
conscious of them, though we may differ as to the words in which
they may be expressed ; nor need I talk about man’s power of
articulate speech, nor his realisation of history, nor his inherent
social sympathies, nor his gentleness. For all recognise that the
higher life of men has a loftier pitch than that of animals, while
many think that the difference is in kind, not merely in degree.

2. Descent of Man. — The arguments by which Darwin and
others have sought to show that man arose from an ancestral type
common to him and to the higher apes are the same as those used
to substantiate the general doctrine of descent. For the Descent
of Man was but the expansion of a chapter in the Origin of Species ;

342

Al'f'.

The Study of Animal Life

the arguments used to prove the origin of animal from animal were
adapted to rationalise the ascent of man.

{a) Physiological. — The bodily life of man is like that of mon-
keys ; both are subject to the same diseases ; various human traits,
such as gestures and expressions, are paralleled among the “ brutes ” ;
and children born during famine or in disease are often sadly
ape-like.

(b) Morphological. — The structure of man is like that of the
anthropoid apes, none of his distinctive characters except that of
a heavy brain being momentous, and there are about seventy
vestigial structures in the muscular, skeletal, and other systems.

(c) Historical. — There is little certainty in regard to the fossil
remains of prehistoric man, but some of these suggest more, primi-
tive skulls, while the facts known about ancient life show at least
that there has been progress along certain lines. Moreover, there
is the progress of each individual life, from the apparently simple
egg-cell to the minute embryo, which is fashioned within the womb
into the likeness of a child, and being bora grows from stage to
stage, all in a manner which it is hard to understand if man be
not the outcome of a natural evolution.

3. Various Opinions about the Descent of Man.— But

opinion in regard to the origin of man is by no means unanimous.

(a) A few authorities, notably A. de Quatrefages, maintain a
conservative position, believing that the evolutionist’s case has not
been sufficiently demonstrated. But the majority of naturalists
believe the reverse, and think that the insufficiencies of evidence in
regard to man are counterbalanced by the force of the argument
from analogy.

(b) Alfred Russel Wallace has consistently maintained a position
which seems to many a very strong one. “I fully accept,” he
says, “ Mr. Darwin’s conclusion as to the essential identity of man’s
bodily structure with that of the higher mammalia, and his descent
from some ancestral form common to man and the anthropoid apes.
The evidence of such descent appears to me overwhelming and
conclusive. Again, as to the cause and method of such descent
and modification, we may admit, at all events ' provisionally, that
the laws of variation and natural selection, acting through the
struggle for existence and the continual need of more perfect
adaptation to the physical and biological environments, may have
brought about, first that perfection of bodily structure in which he
is so far above all other animals, and in co-ordination with it the
larger and more developed brain, by means of which he has been
able to utilise that structure in the more and more complete sub-
jection of the whole animal and vegetable kingdoms to his
service.”

I

343

Animal Life and Ours

“ But because man’s physical structure has been developed
from an animal form by natural selection, it does not necessarily
follow that his mental nature, even though developed pari passu
with it, has been developed by the same causes only. ” Wallace
then goes on to show that man’s mathematical, musical, artistic,
and other higher faculties could not be developed by variation and
natural selection alone. “Therefore some other influence, law, or
agency is required to account for them.” Indeed this unknown
cause or power may have had a much wider influence, extending
to the whole course of his development. “ The love of truth, the
delight in beauty, the passion for justice, and the thrill of exulta-
tion with which we hear of any act of courageous self-sacrifice, are
the workings within us of a higher nature which has not been
developed by means of the struggle for material existence.” At
the origin of living things, at the introduction of consciousness, in
the development of man’s higher faculties, “ a change in essential
nature (due, probably, to causes of a higher order than those of the
material universe) took place.” “The progressive manifestations
of life in the vegetable, the animal, and man — which we may
classify as unconscious, conscious, and intellectual life — probably
depend upon different degrees of spiritual influx. ”

In discussing problems such as this there is apt to be misunder-
standing, for words are “but feeble light on the depth of the un-
spoken,” and perhaps no man appreciates his brother’s philosophy.
Therefore, I refrain from seeking to controvert what Wallace has
said, especially as I also believe that the nature of life and mind
are secrets to us all, and that the higher life of man cannot be
explained by indefinite variations which happened to prosper in the
course of natural selection.

But it seems to me (i) to be difficult to divide man’s self into
an animal nature which has been naturally evolved and “a
spiritual nature which has been superadded,” or to separate man’s
higher life from that of some of the beasts. (2) When we find
that any fact in our experience, such as human reason, cannot
be explained on the theory of evolution which we have adopted, it
does not follow that the reality in question has not been naturally
evolved, it only follows that our theory of evolution is imperfect.
A theory is not proved to be complete because it explains many
facts, but it is proved to be incomplete if it fails to explain any.
Thus if man’s higher nature cannot be explained by the theory of
natural selection in the struggle for existence, then that theory is
incomplete, but there may be other theories of evolution which are
sufficient. (3) It is difficult to know what is meant by spiritual
influx — for our opinions in regard to those matters vary with
individual experience. We may mean to suggest the interpola-

344

API'.

The Study of Animal Life

tion of a power of a secret and supersensory nature, distinct from
that power which is everywhere present in sunbeam and rain-
drop, bird and flower. Then we are abandoning the theory of a
continuous natural evolution. Or we may mean to suggest that when
life and mind and man began to be, then possibilities of action and
reaction hitherto latent became real, and all things became in a
sense new. Then, while maintaining that life and mind are new'
realities with new powers, we are still consistent believers in a con-
tinuous natural evolution. (4) Perhaps the simplest conception is
that more than once suggested in this book, that the world is one
not twofold, that the spiritual influx is the primal reality, that there
is nothing in the end which was not also in the beginning.

(c) Prof. Calderwood has recently stated w'ith clearness and
conciseness what difficulties surround the task of those who w'ould
explain the evolution of man. “ So far as the human organism is
concerned, there seem no overwhelming obstacles to be encountered
by an evolution theory ; but it seems impossible under such a theory
to account for the appearance of hoir.o sapiens — the thinking, self-
regulating life, distinctively human.” Again, I have no desire to
enter into controversy, for I recognise the difficulties which the
student of comparative psychology must tackle, but it seems
important that the following consideration should be kept in mind.

It is not the first business of the evolutionist to find out how one
reality has grown out of another, but to marshal the arguments
which lead him to conclude that one reality has so evolved. We
have only a vague idea how a backbone arose, but that need not
hinder us from believing that backboned animals were evolved from
backboneless if there be sufficient evidence in favour of this con-
clusion. We do not know how birds arose from a reptile stock,
but that they did so arise is fairly certain. We cannot explain the
intelligence of man in terms of the activity of the brain ; we are
equally at a loss in regard to the intelligence of an ant. What we
have to do is to compare the structure of man’s brain with that of
the nearest animals, and the nature of human intelligence with that
of the closest approximations, drawing from the results of our
comparison what conclusion we can. The general doctrine of
descent may be established independently of the investigations of
physiologist and psychologist, valuable as these may be in elucidat-
ing the way in which the great steps of progress have been made.

(d) Finally there is the opinion of many that man is altogether
too marvellous a being to have arisen from any humbler form of
life. But to others this ascent seems the stamp of man’s nobility.

4. Ancestors of Man. — Of these we know nothing. The
anthropoid apes approach him most closely, each in some particular
respect, but none of them nor any known form of life can be called

i Animal Life and Ours 345

man’s ancestor. It is possible that the race of men — for of a
first man evolutionists cannot speak — began in Miocene times,
as offshoots from an ancestral stock common to them and to the
anthropoids. We often hear of “ the missing link,” but surely no
one expects to find him alive. And while we have still much to
learn from the imperfect geological record, it must be remembered
that what most distinguishes man will not be remarkable in a fossil,
for brains do not petrify except metaphorically, nor can we look for
fossilised intelligence or gentleness.

Fig. 71. — Young gorilla. (From Du Chaillu.)

5- Possible Factors in the Ascent of Man. — In regard to
the factors which secured man’s ascent from a humbler form of life
we can only speculate.

(a) We have already explained that organisms vary, that the
offspring differ from their parents, that the more favourable changes
prosper, and that the less fit die out of the struggle. Thus the race
is lifted. Now, from what we know of men and monkeys, it seems
likely that in the struggles of primitive man cunning was more
important than strength, and if intelligence now became, more than
ever before, the condition of life or death, wits woyld tend to
develop rapidly.

(b) When habits of using sticks and stones, of building shelters,
of living in families, began — and some monkeys exhibit these — it is
likely that wits would increase by leaps and bounds.

(r) Professor Fiske and others have emphasised the importance of
prolonged infancy, and this must surely have helped to evolve the
gentleness of mankind.

346

APP.

The Study of Animal Life

(d) Among many monkeys society has begun. Families com-
bine for protection, and the combination favours the development
both of emotional and intellectual strength. Surely “ man did not
make society, society made man.”

B. Our Relation to Biology.

6. The Utility of Science. — As life is short, all too short for
learning the art of living, it is well that we should criticise our
activities, and favour those which seem to yield most return of
health and wealth and wisdom.

We are so curious about all kinds of things, so omnivorously
hungry for information, that the most trivial department of know-
ledge or science may afford exercise and mental satisfaction to its
votaries. The interest and pleasantness of science is therefore no
criterion.

Nor can we be satisfied with the assertion that science should
be pursued for science’s sake. As in regard to the kindred dictum,
“ art for art’s sake,” we require further explanation — some idea! of
science and art. For it is not evident that knowledge is a good in
itself, especially if that knowledge be gained at the expense of the
emotional wealth which is often associated with healthy ignorance.

Nor is it safe to judge scientific activity by the material results
which the application of knowledge to action may yield. For a seed
of knowledge may lie dormant for centuries before it sends its shoots
into life, and many of the material results of applied science are not
unmixed blessings. Moreover, too narrow a view may be taken of
material results, so-called “ necessaries ” of existence may be exalted
over the “super-necessaries” essential to life; in short, what lies
about the mouth — the nose, the ears, the eyes, the brain — may be
forgotten.

We are nearer the truth if we combine the different standards of
science, and unify them by reference to the human ideal.1 The utility
of science, and of biology among the other kinds of knowledge, is
to supply a basis of fact —

(a) For the practice of useful arts (such as hygiene and
education), and for the guidance of conduct :

(l) For the satisfaction of our desire to understand and enjoy
the world and our life in it.

7. Practical Justification of Biology.— The world of life
is so web-like that almost any part may touch or thrill us. It is
therefore well that we should learn what we can about it.

On plants we are very dependent for food and drink, for shelter

1 See Ruskin, The Eagle's Nest (1880).

i Animal Life and Ours 347

and clothing, and for delight. Their evil influence is almost
restricted to that of disease germs and poisonous herbs.

Animals likewise furnish food (perhaps to an unwholesome
extent) ; and parts of their bodies are used (sometimes carelessly)
in manifold ways. Among those which are domesticated, some,
such as canary and parrot, cat .and dog, are kept for the pleasure
they give to many ; others, such as dog, horse, elephant, and
falcon, are used in the chase ; others, notably the dog, assist in
shepherding ; horse and ass, reindeer and cattle, camel and
elephant, are beasts of burden ; others yield useful products, the
milk of cows and goats, the eggs of birds, the silk of silkworms,
and the honey of bees.

Formerly of much greater importance for good and ill as direct
rivals, animals have, through man’s increasing mastery of life, become
less dangerous and more directly useful. Only in primitive con-
ditions of life and in thinly-peopled territories is something of the
old struggle still experienced. Their influence for ill is now for the
most part indirect, — on crops and stocks. Parasites are common
enough, but rarely fatal. The serpent, however, still bites the
heel of progressive man.

Man’s relations with living creatures are so close that systematic
knowledge about them is evidently of direct use. Indeed it is in
practical lore that both botany and zoology have their primal roots,
and from these, now much strengthened, impulses do not cease to
give new life to science.

If increase of food-supply be desirable, biology has something to
say about soil and cereals, about fisheries and oyster-culture. The
art of agriculture and breeding has been influenced not a little by
scientific advice, though much more by unrationalised experience.
If wine be wanted, the biologist has something to say about grafting
and the Phylloxera, about mildew and Bacteria. It is enough to
point to the succession of discoveries by which Pasteur alone has
enriched science and benefited humanity.

But if we take higher ground and consider as an ideal the health-
fulness of men, which is one of the most obvious and useful
standards of individual and social conduct, the practical justification
of biological science becomes even more apparent.

Medicine, hygiene, physical education, and good-breeding (or
“eugenics”) are the arts which correspond to the science of
biology, just as education is applied psychology, as government is
applied sociology, and as many industries are applied chemistry and
physics. It would be historically untrue to say that the progress in
these arts was due to progress in the parallel sciences ; in fact the
progressive impulse has often been from art to science. “ La
pratique a partout devance la theorie,” Espinas says, and all

34§

APP.

The Study of Animal Life

historians of science would in the main confirm this. But it is
also true that science reacts on the arts and sometimes improves
them.

There may be peculiar aberrations of the art of medicine due to
the progress of the science thereof, but these are because the science
is partial, and hardly affect the general fact that scientific progress
has advanced the art of healing. The results of science have like-
wise supplied a basis to the endeavours to prevent disease and to
increase healthfulness, not only by definite hygienic practice but
perhaps still more by diffusing some precise knowledge of the
conditions of health.

The generalisations of biology, realised in men’s minds, must in
some measure affect practice and public opinion. Spencer’s
induction that the rate of reproduction varies inversely with the
degree of development sheds a hopeful light on the population
question ; the recognition of the influence which function and sur-
roundings have upon the organism suggests criticism of many
modes of economic production ; a knowledge of the facts and
theory of heredity must have an increasing influence on the art of
eugenics. Nor can I believe that the theory of evolution which
men hold, granting that it is in part an expression of their life and
social environment, does not also react on these.

In short, the direct application of biological knowledge in the
various arts of medicine, hygiene, physical education, and eugenics,
helps us to perfect our environment and our relations with it, helps
us to discover — if not the “elixir vitae” — some not despicable
substitute. And likewise, a realisation of the facts and principles of
biology helps us to criticise, justify, and regulate conduct, suggest-
ing how the art of life may be better learned, how human relations
may be more wisely harmonised, how we may guide and help the
ascent of man.

8. Intellectual Justification of Biology. — But another
partial justification of Biology is found in our desire to understand
things, in our dislike of obscurities, in our inborn curiosity. There
is an intellectual as well as a practical and ethical justification of
the study of organic life.

Through our senses we become aware of the world of which we
form a part. We cannot know it in itself, for we are part of it and
only know it as it becomes part of us. We know only fractions of
reality — real at least to us — and these are unified in our experience.

(i) In the world around us we are accustomed to distinguish
four orders of facts. “ Matter ” and “ energy ” we call those which
seem to us fundamental, because all that we know by our senses
are forms of these. The study of matter and energy — or perhaps
we may say the study of matter in motion — considered apart from

i Animal Life mid Ours 349

life, we call Physics and Chemistry, of which astronomy, geology,
etc., are special departments.

(2) But we also know something about plants and animals, and
while all that we know about them is still dependent upon changes
of matter and motion, yet we recognise that the activities of the
organism cannot at present be expressed in terms of these. There-
fore we find it convenient to speak of life as a new reality, while
believing that it is the result of some combination of matters and
energies, the secret of which is hidden.

(3) But we are also aware of another reality, our own mind. Of
this we have direct consciousness and greater certainty than about
anything else. And while some would say that what we are
conscious of when we think is a protoplasmic change in our brain
cells or is a subtle kind of motion, it is truer to say that we are
conscious of ourselves. It is our thought that we know, it is our
feeling that we feel, and as we cannot explain the thought or the
feeling in terms of protoplasm or of motion, we find it convenient to
speak of mind as a new reality, while believing it to be essentially
associated with some complex activity of protoplasm the secret of
which is hidden. For our knowledge of our own mental processes,
and of those inferred to be similar in our fellows, and of those
inferred to be not very different in intelligent animals, we establish
another science of Psychology.

(4) But we also know something about the life of the human
society of which we form a part. We recognise that it has a unity
of its own, and that its activities are more than those of its
individual members added up. We find it convenient to regard
society as another synthesis or unity — though less definite than
either organism or mind — and to our knowledge of the life and
growth of society as a whole, we apply the term sociology.

Thus we recognise four orders of facts and four great' sciences —

4. Society Sociology.

3. Mind Psychology.

2. Life Biology.

1. Matter and Energy . . . Physics and Chemistry.

Each of these sciences is dependent upon its predecessor. The
student of organisms requires help from the student of chemistry
and physics ; mind cannot be discussed apart from body ; nor can
society be studied apart from the minds of its component members.

Each order of realities we may regard as a subtle synthesis of
those which we call simpler. Life is a secret synthesis of matter
and energy ; mind is a subtle form of life ; society is a unity of
minds.

But it must be clearly recognised that the “matter and energy”
which we regard as the fundamental realities are only know'n to us

35° The Study of Animal Life app. i

through what is for us the supreme reality — ourselves — mind. And
as in our brain activity we know matter and energy as thought, I
have adopted throughout this book what may be called a monistic
philosophy.

Having recognised the central position of Biology among the
other sciences, we have still to inquire what its task precisely is.

Our scientific data are (i) the impressions which we gather
through our senses about living creatures, and (2) the deductions
which we directly draw in regard to these. Our scientific aim
is to arrange these data so that we may have a mental picture of
the life around us, so that we may be better able to understand
what that life is, and how it has come to be what it seems to be.
Pursuing what are called scientific methods, we try to make the
world of life and our life as organisms as intelligible as possible.
We seek to remove obscurities of perception, to make the world
translucent, to make a working thought-model of the world.

But we are apt to forget how ignorant we are about the realities
themselves, for all the time we are dealing not with realities, but
with impressions of realities, and with inferences from these im-
pressions. On the other hand, we are apt to forget that our deep
desire is not merely to know, but to enjoy the world, that the heart
of things is not so much known by the man as it is felt by the child.

APPENDIX II

SOME OF THE “BEST BOOKS” ON ANIMAL LIFE

To recommend the “ best books ” on any subject is apt to be like
prescribing the “best diet.” Both depend upon age, constitution,
and opportunities. The best book for me is that which does me
most good, but it may be tedious reading for you. Moreover,
books are often good for one purpose and not for another ; that
which helps us to realise the beauty and marvel of animal life may
be of little service to those who are preparing for any of the
numerous examinations in science. But the greatest difficulty is
that we are often too much influenced by contemporary opinion,
so that we lose our power of appreciating intellectual per-
spective.

The best way to begin the study of Natural History is to
observe animal life, but the next best way is to read such accounts
of observation and travel as are to be found in the works of
Gilbert White, Thoreau, Richard Jefferies, and John Burroughs,
or in Bates’s Naturalist on the Amazons, Belt’s Naturalist in
Nicaragua , and Darwin’s Voyage of the “Beagle." Sooner or later
the student will seek more systematic books, but it is not natural
that he should begin with a text-book of elementary biology.

In introducing you to the literature devoted to the study of
animals, I shall avoid the bias of current opinion by following the
history of zoology. I shall first name some of the more technical
books ; secondly, some of the more popular ; thirdly, some of the
more theoretical. If I may make the distinction, I shall first
mention books on zoology, secondly those on natural history,
thirdly those on biology.

A. Zoology.

(i) We can form a vivid conception of the history of zoology
by comparing it with our own. In our childhood we knew and

352

APP.

The Study of Animal Life

cared more about the useful, dangerous, and strange animals than
about those which were humble and familiar ; we had more in-
terest in haunts and habits than in structure and history ; we
were content with rough-and-ready classification, and cherished
a feeling of superstitious awe in regard to the indistinctly-known
forms of life. We were inquisitive rather than critical ; we
accepted almost any explanation of facts, and, if we tried to inter-
pret, forced our borrowed opinions upon nature instead of trying
to study things for ourselves. So was it with those naturalists who
lived before Aristotle.

We must also recognise that the science of zoology had its
beginnings in a practical acquaintance with animals, just as botany
sprang from the knowledge of ancient ' agriculturists and herb-
gatherers. Much information in regard to the earliest zoological
knowledge has been gathered from researches into the history of
words, art, and religious customs, and there is still much to be
gleaned. Therefore I should recommend the student to dip into
those books which discuss the early history of man, such as
Lubbock’s Prehistoric Times (1865), and Origin of Civilisation
(1870) ; Tylor’s Primitive Cultzire (1871), and Anthropology
(1881); Andrew Lang’s Myths, Ritual, and Religion ; besides
works on the history of philosophy, such as those of Schwegler and
of Zeller, which give some account of ancient cosmogonies.

(2) But just as there are precocious children, so there was an
early naturalist, whose works form the most colossal monument to
the intellectual prowess of any one thinker. The foundations of
zoology were laid by Aristotle, who lived 384-322 B.c. He
collected many observations, and argued from them to general
statements. He records over five hundred animals, and describes
the structure and habits, the struggles and friendliness, of some
of these. His is the first definite classification. His work
was dominated by the idea that animal life is a unity and part
of a larger system of things. In part his works should be read,
and besides the great edition by Bekker (Berlin, 1831-40),
there is a translation of The Parts of Animals by Dr. Ogle, and
of The History of Animals by R. Cresswell. See also G. J.
Romanes’s “ Aristotle as a Naturalist,” Nineteenth Century (Feb.
1891, pp. 275-289).

(3) After the freedom of early childhood, and in most cases
after precocity too, there comes a lull of inquisitiveness. Other
affairs, practical tasks, games and combats, engross the attention,
and parents sigh over dormant intellects ; so the historian of
zoology sighs over the fifteen centuries during which science
slumbered. The foundations which Aristotle had firmly laid
remained, but the walls of the temple of knowledge did not rise.

n Some of the 11 Best Books" on Animal Life 353

The seeds which he had sown were alive, but they did not germi-
nate. Men were otherwise occupied, with practical affairs, with
the tasks of civilisation alike in peace and war, though some at
their leisure played with ideas which they did not verify. There
were some exceptions; such as Pliny (23-79 a.d.), a diligent but
uncritical collector of facts, and Galen (130-200 a.d.), a medical
anatomist, who had the courage to dissect monkeys ; besides the
Spanish bishop Isidor in the seventh century, and various Arabian
inquirers. It will not be unprofitable to look into the Natural
History of Pliny, which has been translated by Bostock and
Riley.

(4) But just as there is in our life a stage — happy are those who
prolong it — during which we delight in fables and fairy tales, so
there was a long period of mythological zoology. The schoolboy
who puts horse-hairs into the brook, and returns after many days
to find them eel-like worms, is doing what they did in the Middle
Ages. For then fact and fiction were strangely jumbled ; credulity
ran riot along the paths of science ; allegorical interpretations and
superstitious symbolisms were abundant as the fancies which flit
through the minds of dreamers. Scientific inquiry was not en-
couraged by the theological mood of the time ; and just as Scotch
children cherish The Beasts of the Bible as a pleasantly secular book
with a spice of sacredness which makes it legitimate reading on
the Sabbath, so many a mediaeval naturalist had to cloak his
observations in a semi-theological style.

In illustration of the mood of the mediaeval naturalists, which
is by no means to be carelessly laughed at, read John Ashton’s
Curious Creatures (Lond., 1890), in which much old lore is retold,
often in the words of the original writers. The most characteristic
expression of mythical Zoology is a production often called Physio-
logies. It is found in about a dozen languages and in many
different forms, being in part merely a precipitate of floating
traditions. It is partly like a natural history of the beasts of the
Bible and prototype of many similar works, partly an account of
the habits of animals, the study of which modern zoologists are
apt to neglect, partly a collection of natural history fables and
anecdotes, partly a treatise on symbolism and suggestive of the
poetical side of zoology, partly an account of the medicinal and
magical uses of animals. For many centuries it seems to have
served as a text-book, a fact in itself an index to the slow progress
of the science. Its influence on art and literature has been con-
siderable, and it well illustrates the attempt to secure for the
unextinguishable interest in living things a sanction and foothold
under the patronage of theology. A series of fifty emblems is
described, among others the lion which sleeps with its eyes open,

2 A

354

AM*.

The Study of Animal Life

the lizard which recovers its sight by looking at the sun, the eagle
which renews its youth, the tortoise mistaken for an island, the
serpent afraid of naked man, and the most miserable ant-lion,
which is not able either to take one kind of food or digest the
other.

(5) But delight in romance is replaced by a feeling of the need
for definite knowledge, and the earlier years of adolescent man-
hood and womanhood are often very markedly characterised by a
thirst and hunger for information. Which of us — now perhaps
blase with too much learning — does not recall the enthusiasm for
knowing which once swayed our minds ? Stimulated in a hundred
ways by new experiences and responsibilities, our appetite for facts
was once enormous. This was the mood of naturalists during the
next great period in the history of zoology.

The freer circulation of men and thoughts associated with the
Crusades ; the discovery of new lands by travellers like Marco
Polo and Columbus ; the founding of universities and learned
societies ; the establishment of museums and botanic gardens ; the
invention of printing and the reappearance of Aristotle’s works in
dilution and translation ; and many other practical, emotional, and
intellectual movements gave fresh force to science, and indeed to
the whole life of man. If we pass over some connecting links,
such as Albertus Magnus in the thirteeenth century, we may call
the period of gradual scientific renaissance that of the Encyclo-
paedists. This somewhat cumbrous title suggests the omnivorous
habits of those early workers. They were painstaking collectors
of all information about all animals ; but their appetite was
greater than their digestion, and the progress of science was
in quantity rather than in quality. Prominent among them were
these four, the Englishman Edward Wotton (1492- 1555), who
wrote a treatise De Differentiis Animalium ; the Swiss Conrad
Gesner (1516-65), author of a well-known Historia Animalium ;
the Italian Aldrovandi (b. 1522); and the Scotsman Johnston
(b. 1603).

About the middle of the eighteenth century the best aims of the
Encyclopaedists were realised in Buffon’s Histoire Nalurelle, which
appeared in fifteen volumes between 1749 and 1767. This work
not only describes beasts and birds, the earth and man, with an
eloquent enthusiasm which was natural to the author and pleasing
to his contemporaries, but is the first noteworthy attempt to
expound the history or evolution of animals. Its range was very
wide ; and its successors are not so much single books as many
different kinds of books, on geology and physical geography, on
classification and physiology, on anthropology and natural history.
There is a good French edition of Buffon’s complete works by

II

Some of the “ Best Books ” on Animal Life 355

A. Richard 1S25-2S), and at least one English translation. Three
large modern books on natural history correspond in some degree
to the Histoire Naturelie , viz. Cassells Natural History, edited by
P. Martin Duncan (6 vols. ; London, 1882) ; The Standard or
Riverside Natural History, edited by J. S. Kingsley (6 vols. ;
London, 18S8); and a remarkable work well known as Brelnn’s
Thierleben, of which a new (3rd) edition is at present in progress
(10 vols.; Leipzig and Wien, 1890). Those who read German
will find in Carus Sterne’s (Ernst Krause’s) Werden und Vergehen
(3rd ed. ; Berlin, 1886) the most successful attempt hitherto
made to combine in one volume a histoiy of the earth and its
inhabitants.

(6) From Buffon till now the history of biology shows a pro-
gressive analysis, a deeper and deeper penetration into the structure
and life of organisms. From external form to the internal organs,
from organs to the tissues which compose them, from tissues to
their elementary units or cells, and from cells to the living matter
itself, has been the progress of the science of structure — Mor-
phology. From habit and temperament to the work of organs,
from the functions of organs to the properties of tissues, from these
to the activities of cells, and from these finally to the chemical and
physical changes in the living matter or protoplasm, has been the
progress of the science of function — Physiology. Such is the lucid
account which Prof. Geddes has given of the last hundred years’
progress; see his article “Biology” in the new edition of
Chambers’s Encyclopedia. Following the metaphor on which we
have already insisted, we may compare this century of analysis to
the period of ordered and more intense study which in the individual
life succeeds the abandonment of encyclopaedic ambitions.

We should clearly understand the histoiy of this gradually
deepening analysis of animals ; for if we would be naturalists
we must retread the same path. The history of biology has still
to be written, but there are already some useful books and papers,
notably — J. V. Carus, Geschichte der Zoologie (Miinchen, 1872) ;
J. Sachs, Geschichte der Botanik (Miinchen, 1875), translated
into English (Oxford, 1890); W. Whewell, History of the
Inductive Sciences (London, 1840) ; articles “ Morphology ”
and “Physiology,” Encyclopaedia Brilannica, by P. Geddes and
M. Foster; H. A. Nicholson, Natural History: its Rise and
Progress in Britain (Edinburgh, 1888); A. B. Buckley, Short
History of Natural Science ; E. Perrier, La Philosophic Zoologique
avant Darwin (Paris, 1884); Ernst Krause (Carus Sterne), Die
Allgemeine Weltanschauung in Hirer historischen Entwickelung
(Stuttgart, 1889). Very instructive, not least so in contrast,
are two articles, “Biology” (in Chambers’s Encyclopaedia), by

35^ The Study of Animal Life AI.j>.

P. Geddcs, and “Zoology” (in Encyclopedia Britannicd), by £.
Ray Lanlcester.

If we think over the sketch which Professor Geddes has given,
we shall see how easy it is to arrange the literature — the first step
towards mastering it. (a) The early anatomists were chiefly
occupied with the study of external and general features, very
largely moreover with the purpose of establishing a classification.
The Systcma Nature of Linnaeus (1st ed., 1735; 12th, 1768) Ls
the typical work on this heavily-laden shelf of the zoological
library. It is to such books that we turn when we wish to
identify some animal, but the shelf is very long and most of the
volumes are very heavy. Each chapter of Linne’s Systema has
been expanded into a series of volumes, or into some gigantic
monograph like those included in the series of “ Challenger ” Reports ,
or The Fauna and Flora of the Gulf of Naples. If I am asked
to recommend a volume from which the eager student may identify
some British flower, I can at once place Hooker’s Flora in his
hands. But it is more difficult to help him to a work by which he
may identify his animal prize. There are special works on British
Mammals, Birds, Fishes, Molluscs, Insects, etc., but a compact
British Fauna is much wanted. I shall simply mention Bronn’s
Klassen und Ordnungen des Thierreiches, a series of volumes still
in progress ; Leunis, Synopsis des Thierreiches (Hanover, 1 886) ;
the British Museum Catalogues (in progress) ; and P. FI. Gosse’s
Manual of Marine Zoology of the British Islands (1856).

If) Cuvier’s R'cgne Animal (1829) is the typical book on the
next plane of research — that concerned with the anatomy of organs.
I should recommend the student on this path to begin with Pro-
fessor F. Jeffrey Bell’s Comparative Anatomy and Physiology (Lond.,
1886) ; after which he will more readily appreciate the text-books
on Comparative Anatomy by Huxley, Gegenbaur, Claus, Wieders-
heim, Lang, etc. As an introduction I may also mention my
Outlines of Zoology (Edin., 1892). As a book of reference
Hatchett Jackson’s edition of Rolleston’s Forms of Animal Life
(Oxford, 1888) is of great value, not least on account of its
scholarly references to the literature of zoology. The zoological
articles in the Encyclopedia Britannica, many of which are pub-
lished separately, are not less useful. As guides in serious practical
work may be noticed — A Course of Elementary Instniction in
Practical Biology by Profs. T. H. Huxley and H. N. Martin,
revised by Profs. G. B. Howes and D. H. Scott (Lond., 1S8S) ;
Howes’s Allas of Practical Elementary Biology (Lond., 1885);
A Course of Practical Zoology by Prof. A. Milnes Marshall and
Dr. C. FI. Hurst (3rd ed., Lond., 1892); Prof. C. Lloyd
Morgan’s Animal Biology (Lond., 18S9); Vogt and Yung, Traiti

II

Some of the “ Best Books ” on Animal Life 357

d'Atiatomie compart e pratique (Paris, 1885-92) or in German
(Braunschweig) ; Prof. W. K. Brooks’s Handbook of Invertebrate
Zoology for Laboratories and Seaside Work (Boston, 1882); Prof.
T. J. Parker’s Zootomy (Loncl., 1884) and Practical Biology
(Lond., 1S91).

(c) As early as 1801, Bichat had penetrated beneath the organs
to the tissues which compose them, and his Anatomie Gene rale is
the forerunner of many works on minute anatomy or histology.
From the comparative histology of animals by Leydig ( Histologie ,
1867) the zoological student must begin, but to follow it up he must
have recourse to the pages of scientific journals. As a guide in
microscopic work, Dr. Dallinger’s new edition of Carpenter’s well-
known work, The Microscope (Lond., 1891) may be cited.

(it) In 1838-39, Schwann and Schleiden, two German naturalists,
clearly stated a doctrine towards which investigation had been
gradually tending, namely, that each organism was built up of
cells, and originated from a fertilised egg-cell. In the establish-
ment of this “cell-theory ” the study of structure became deeper,
and the investigation of animal cells still becomes more and more
intense. To gain an appreciation of this step in analysis, the
student may well begin with the article “ Cell ” in the new edition
of Chambers’s Encyclopedia, and with the articles “Morphology”
and “Protozoa” in the Encyclopedia Britannica. From these he
will discover how his studies may be deepened.

(e) Finally, with the improvement of microscopic instruments
and technique, investigation has touched the bottom, as far as
biology is concerned, in the study of the living stuff or protoplasm
itself. Again, I refer you to the articles “Protoplasm” in the
Encyclopedia Britannica and in Chambers’s Encyclopedia.

I shall not follow the history of physiology in detail, but content
myself with saying that (a) from the conception of a living body
ruled by spirits or dominated by a temperament, physiologists passed
to consider it (b) as an engine of living organs, then (r) as a com-
plex web of tissues, then (d) as a city of cells, and finally (e) as a
whirlpool of living matter. I recommend you to read first the
article “ Physiology ” in the Encyclopedia Britannica, then Huxley’s
Crayfish (International Science Series), and his Elementary Text-
book of Physiology, then Jeffrey Bell’s Comparative Anatomy and
Physiology and Lloyd Morgan’s Animal Biology, after which you
may pass to larger works such as the text-books of Kirkes (new ed. ,
1892) ; Bunge (Lond., 1890) ; Landois and Stirling, McKendrick,
and Foster, and to the studies on comparative physiology by
Krukenberg, Vergleichend- Physiologische Studien and Vortrdge
(Heidelberg, 1882-88).

In the above summary nothing has been said about the history

35§

APP.

The Study of Animal Life

of animals in their individual life (embryology), nor of their gradual
appearance upon the earth (palaeontology), nor about their distri-
bution in space. As regards embryology, begin with the article
in Chambers’s Encyclopedia, and pass thence to the text-books
of A. C. Iladdon, F. M. Balfour, M. Foster and F. M. Balfour,
O. Hertwig, Heider and Korschelt, etc. A short account of
distribution in time will be found in A. Heilprin’s Distribution of
Animals (International Science Series), from which advanced
students may pass to the Text -book of Paleontology by Ii. A.
Nicholson and R. Lydekker (2 vols., Lond. and Edin., 1889), to
the French work of Gaudry, Les enchainements du inonde animal
dans les temps geologiques (Paris, 1888-90), or to the German
works of Zittel and of Neumayr. Heilprin’s book is again the
best introduction to the study of distribution in space, while
Wallace’s Geographical Distribution of Animals (Lond., 1876)
remains the principal work of reference.

For progressive research I may refer the student to the Journal
of the Royal Microscopical Society (edited by Prof. F. Jeffrey Bell),
which gives summaries of recent researches ; the Quarterly Journal
of Microscopical Science (edited by Profs. E. Ray Lankester, Klein,
Sedgwick, and Milnes Marshall) ; and of course Nature, in which
summaries and discussions are often to be found. More popular
journals are the American Naturalist and Natural Science.

Of all elementary books the best to begin with are two volumes
by A. B. Buckley, Life and her Children (backboneless animals),
and Winners in Life's Race (backboned animals) ; but I shall now
mention other ways of beginning.

B. Natural History.

“ Certain dreadfully scientific persons, who call themselves by
the name of naturalists, seem to consider zoology and comparative
anatomy as convertible terms. When they see a creature new to
them, they are seized with a burning desire to cut it up, to analyse
it, to get it under the microscope, to publish a learned book about
it which no one can read without an expensive Greek lexicon, and
to put up its remains in cells and bottles. They delight in an
abnormal haemapophysis ; they pin their faith on a pterygoid pro-
cess ; they stake their reputation on the number of tubercules on
a second molar tooth ; and they quarrel with each other about a
notch on the basisphenoid bone.” Thus, in a breezy way, did the
Rev. J. G. Wood laugh at the morphological zoologists. But his
good-humoured criticism is apt to be misleading. For if science,
as such, be justifiable, the work of the anatomist is warranted as

II

Some of the " Best Books" on Animal Life 359

part of it, and is neither less nor more valuable than that of the
field naturalist. We may criticise the details of the anatomist’s
analysis, we may believe that his discipline is often pressed
unnaturally upon students, we may beseech him to be less
pedantic ; but to remind him that the study of structure requires
to be supplemented by the study of life is like reminding the field
naturalist that animals have bones and muscles. Both are true
statements, but somewhat obvious.

The zoologist has deliberately given himself up to analysis, and
if the world is to become translucent to us, we must include within
our knowledge what he can tell us about the structure and activities
of animals, alike as unities and as complex combinations of organs,
tissues, and cells. Let us agree to call this serious study, including
the morphological and physiological aspects which we have already
explained, “zoology.” We must acknowledge that few of us can
become zoological experts. But let not this hinder us from per-
ceiving that it is not difficult to understand towards what end and
by what method Linnaeus and Cuvier, Bichat and Claude Bernard,
and the other great masters worked ; nor let it deter us from using
all natural opportunities of practically observing the forms and
powers of animal life. We shall soon feel that “zoology” is
neither less interesting nor less essential than the work of the
field naturalist, we shall recognise that its terminology is not more
complex than that of seamanship, and we may even admit that
from clear zoological thinking our contemplation of nature acquires
an additional intensity of emotion. “ Tout naturaliste cachait plus
ou moins un amateur d’idylles ou d ’eclogues.” What Hamerton
says with reference to an artist’s education applies also to the
student of science : “ The harm is not in the study (of plants),
it is in the forgetfulness of large relations to which this minute
observation of nature has occasionally led those who were addicted
to it.” Zoologists are not the only workers who sometimes lose
their sense of perspective.

Now, however, I would address those who have little time or
opportunity for “ zoology,” but who have an interest in the life
and habits of animals, and desire to appreciate these more
thoroughly. This knowledge of animals as personalities — in
struggle and friendliness, in hate and love, in birth and death,
I would call “natural history,” in contrast to analytic “zoology”
on the one hand, and generalising “biology” on the other. For
I restrict the latter term to the general theory of life — its nature
and origin, its growth and continuance. It matters little what
names are given to these three aspects of the study of animal life ;
thus what I call “Natural History” Brof. Ray Lankester calls
more precisely “Bionomics”; but it is important to recognise all

APP.

360 The Study of Animal Life

the three as essential, and to cease from drawing prejudiced com-
parisons between them.

Their relations may be summarised as follows : —

“NATURAL HISTORY."

Study of the
real life
of

{fauna
class
order
genus
species
families
pairs

individuals

I in relation
< to
\ one another

Sand to their
surroundings.

(5) Organism.
(4) Organs.

(3) Tissues.

(2) Cells.

(1) Protoplasm.

Study of Structure
(Morphological)

Study of Activities
(Physiological).

'ZOOLOGY."

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To those interested in “Natural History,” there is little need
to give the primary word of counsel “ Observe,” for to do so is
their delight ; nor do they need to be told that sympathetic feeling
with animals, delight in their harmonious beaut)', and poetical
justice of insight which recognises their personality, are qualities
of a true naturalist, as every one will allow, except those who are
given up to the idolatry of that fiction called “ pure science.”
There is a maniacal covetousness of knowledge which one has
no pleasure in encouraging. We do not want to know all that is
contained even in Chambers’s Encyclopedia , though we wish to
gain the power of understanding, realising, and enjoying the
various aspects of the world around us. We do not wish brains
laden with chemistry and physics, astronomy and geology, botany

II

Some of the " Best Books ” on Animal Life 361

and zoology, and other sciences, though we would have our eyes
lightened so that we may see into the heart of things, our brains
cleared so that we may understand what is known and unknown
when we are brought naturally in face of problems, and our emotions
purified so that we may feel more and more fully the joy of life.
Therefore I would, in the name of education, urge students to
begin naturally, with what interests them, with the near at hand,
with the practically important. A circuitous course of study,
followed with natural eagerness, will lead to better results than the
most logical of programmes if that take no root in the life of the
student.

Let me suggest some of these indirect ways of beginning.
Begin with domesticated animals and their history. See Darwin’s
Variation of Animals and Plants under Domestication (1S68), etc.
Concentrate your attention on some common animals. See, for
instance, Darwin’s Formation of Vegetable Mould through the
action of Worms (1881); Mivart’s Frog (Nature Series, London);
Huxley’s Crayfish (Intemat. Sci. Series, London) ; M ‘Cook’s
North American Spiders (2 vols., Philadelphia, 1889-90); F.
Cheshire’s Bees and Bee-keeping (vol. i., Lond., 1886); Lubbock’s
Ants, Bees, and Wasps (Internat. Sci. Series, London) ; Flower’s
Norse (Lond., 1891).

Enjoy your seaside holiday. See Charles Kingsley’s Glaucus ;
J. G. Wood’s Common Objects of the Sea-Shore (1857); P. H.
Gosse’s Manual of Marine Zoology (1856), and Tenby, G. II.
Lewes’s Seaside Studies (Edin. 1S5S) ; L. Fredericq, La Lutte pour
F existence chez les Animaux Marins (Paris, 1889).

Form an aquarium. See J. G. Wood’s Fresh and Salt Water
Aquarium ; P. H. Gosse, The Aquarium (1854), and many similar
works.

Begin a naturalist’s year-book. See the Naturalist's Diary
by Roberts ; the Field Naturalist' s Handbook, by J. G. and
Th. Wood (Lond., 1879); and K. Russ, Das hcimische
Naturleben im Kreislauf des fahres ; Ein Jahrbuch der Natur.
(Berlin, 1889).

Observe the animals you see on your country walks. See
J. G. Wood’s Common Objects of the Country (1858), The Brook
and its Banks (1889) ; Life of a Scotch Naturalist, Thomas
Edward, by Samuel Smiles ; The Moor and the Loch, by J.
Colquhoun (Edin. 1840, 8th ed. 1878) ; Wild Sports and Natural
History of the Highlands, by Charles St. John (Lond., illust. ed.,
1878); Woodland, Moor, and Stream, edited by J. A. Owen
(Lond., 1889); W. Marshall, Spaziergange eines Naturforschers
(Leipzig, 1888) ; Lloyd Morgan’s Sketches of Animal I.ife (Lond.,
1892), etc. etc.

362 The Study of Animal Life afp.

Another natural way of beginning is to work out some subject
which attracts you. It becomes a centre round which a crystal
grows. Muybridge’s photographic demonstrations of animal loco-
motion have interested us in the flight of birds, let us follow this
up by observation and by reading, e.g., Ruskin’s Love's Meinie
(1881); Pettigrew’s Animal Locomotion (Internat. Sci. Series,
1873); Marey’s Animal Mechanism (Internat. Sci. Series, 1874);
Marey’s Le Vol des Oiseanx (Paris, 1890).

The colours of animals appeal to many people. Read E. B.
Poulton’s volume (1890) in the Internat. Sci. Series, and Grant
Allen’s Colour Sense, and F. E. Beddard’s Animal Colouration
(Lond., 1892).

The relations between plants and animals are entrancingly
interesting. Watch the bees and other insects in their flight,
and read Darwin’s volumes on the Fertilisation of Orchids (1862)
and on Cross- Fertilisation ( 1 8 7 6) ; Hermann Muller’s Fertilisation
of Flowers (transl. by Prof. D’Arcy Thompson, Lond., 1883);
Kerner’s Flowers and their Unbidden Guests ; the articles on
“ Insectivorous Plants,” in Encyclop. Britannica , and in Chambers’s
Encyclop., or Darwin’s work (1875).

Again, many of us are directly interested in foreign countries.
Let the practical interest broaden, it naturally becomes geographical
and physiographical, and extends to the natural history of the
region. No more pleasant and sane way of learning about the
ways and distribution of animals could be suggested than that
which follows as a gradual extension of physiographical knowledge.
See Dr. H. R. Mill’s Realm of Nature, and the following samples
from the long list of books by exploring naturalists : —

A. Agassiz, Three Cruises of the "Blake” (Boston and New York,
1888).

S. W. Baker, Wild Beasts and Ways: Reminiscences of Europe ,

Asia, Africa, and America (London, 1890).

H. W. Bates, Naturalist on the Amazons (5th ed. , London,
1884).

T. Belt, Naturalist in Nicaragua (2nd ed., London, 1888).

W. T. Blanford, Observations on Geology and Zoology of Abyssinia
(Lond., 1870).

P. B. Du Chaillu, Exploratiotis and Adventures in Equatorial Africa,
(Lond., 1861); Ashango Land ( 1867).

R. O. Cunningham, Notes on the Natural History of the Straits of
Magellan (Edin., 1871).

Darwin, Voyage of the “ Beagle ” (1844, new ed. 1890).

H. Drummond, Tropical Africa (Lond., 1888).

H. O. Forbes, A Naturalist's Wanderings in the Eastern Archi-
pelago (Lond., 1885).

Guillemard, Cruise of the " Marchesa" (Lond., 1886).

II

Some of the “ Best Books ” on Animal Life 363

A. Heilprin, The Bermuda Islands (Philadelphia, 1889).

S. J. Hickson, A Naturalist in North Celebes (London, 1889).

W. H. Hudson, The Naturalist in La Plata (Lond., 1892).

A. v. Humboldt, Travels to the Equinoctial Regions of America ;

Aspects of Nature (Trans. 1849); Cosmos ('Frans. 1849-58).
Lumholtz, Among Cannibals (Lond., 1889).

H. N. Moseley, Notes by a Naturalist on the ' ' Challenger" (Lond. ,
1879, new ed. Lond., 1892).

A. E. Nordenskiold, Voyage of the “ Vega " (Lond., 1881).

F. Oates, ed. by C. G. Oates, Matabele Land and the Victoria
Falls, a Naturalist's Wanderings in the Interior of S. Africa
(1881).

N. M. Przewalski, Wissenschaftliche Resultate der nach Centralasien
untemommenen Reisen (Leipzig, 1889).

H. Seebohm, Siberia in Europe (Lond., 1880) ; and Siberia in Asia
(1882).

J. E. Tennent, Natural History of Ceylon (Lond., 1861).

Wyville Thomson, The Depths of the Sea (Lond., 1873) ; Narrative of
the Voyage of the “ Challenger " (1885). Cf. A. de Folin, Sous
les Mers (Paris, 1887) ; H. Filhol, La Vie au fond dcs Mers
(Paris, 1886) ; W. Marshall, Die Tiefsee und ihr Leben (Leipzig,
1888).

Tristram, The Flora and Fauna of Palestine,

Tschudi, Thierleben der A Ipenwelt.

A. R. Wallace, Malay Archipelago (Lond., 1869); Tropical Nature
(1878) ; Island Life (1880).

Ch. Waterton, Wanderings in South America (ed. by J. G. Wood,
1878).

C. M. Woodford, Naturalist among the Head-hunters (London,
1890).

Prominent among those who have helped many to realise the
marvel and beauty of nature, a widely-felt gratitude ranks Gilbert
White, Plenry Thoreau, Charles Kingsley, Richard Jefferies, J. G.
Wood, John Ruskin, and John Burroughs.

Gilbert White (1720-1793) is known to all as the author of
The Natural History and Antiquities of Selborne, in the County of
Southampton (1788), a book consisting of a series of letters addressed
to a few friends. A good edition is that by J. E. Harting (6th ed.,
London, 1888), but there is a cheaper one, edited by Richard
Jefferies, in the Camelot Series.

Henry Thoreau (1817-1862), the author of Walden, A Week
on Concord, and other much-loved books.

Charles Kingsley (1819-1875). See his Glaucus (Lond.,
1854) ; Water- Babies ; and popular lectures.

3^4

APP.

The Study of Animal Life

Richard Jefferies (1848-1887).

See The Eulogy of Richard Jefferies, by Walter Besant (London,
1888), and the following works, some of which are published in
cheap editions: The Gamekeeper at Home (1878): Wild Life
in a Southern Coimty (1879) ; The Amateur Poacher (1880) ;
Round about a Great Estate (1881) ; Nature near London
(1883) ; Life of the Fields (1884) ; Red Deer (1884) ; The Open
Air (1885).

J. G. Wood, whom we have lately lost, has done more than
any other to popularise natural history in Britain.

See Life of J. G. Wood , by his son, Theodore Wood (Lond., 1890) ;
My Feathered Friends (1856) ; Common Objects of the Seashore
(1857) ; Common Objects of the Country (1858) ; his large
Natural History ( 1859-63); Glimpses into Pet land (1862) ; Homes
without Hands (1864) ; The Dominion of Man (1887) ; and other
works.

John Ruskin. See the Eagle's Nest, Queen of the Air, Love's
Meinie, Proserpina, Deucalion , and Ethics of the Dust.

John Burroughs.

See the neat shilling editions of Wake Robin (1871), Winter Sun-
shine (1875), Birds and Poets (1877), Loczists and Wild Honey
(1879), Pepacton (1881), Fresh Fields (1884), Signs and Seasons
(1886).

See also : —

Grant Allen, The Evolutionist at Large; Vignettes from
Nature, etc.

Frank Buckland, Curiosities of Natural History (London,
1872-77), and his Life.

P. II. Gosse. Romance of Natural History (London, 1860-61).

P. G. IIamerton, Chapters on Animals ; The Sylvan Year
(3rd ed., London, 1883).

W. Kirby and W. Spence, Introduction to Entomology
(London, 1815).

F. A. Knight, By Leafy Ways ; Ldylls of the Field (London,
1889).

Phil Robinson, The Poet's Birds (London, 1SS3); and The
Poet's Beasts (London, 1885).

Andrew Wilson, Leaves from a Naturalist's Note-Books ;
Chapters on Evolution, etc.

II

Some of the “ Best Books ” on Animal Life 365 ,

C. Biology.

Having offered counsel to those who would study the literature
of Zoology and of Natural History, I shall complete my task of
giving advice by addressing those who are strong enough to
inquire into the nature, continuance, and progress of life. It is
to students of mature years that this “biological” study is most
natural, for young folks should be left to see and enjoy as much
as possible, till theories grow in them as naturally as “wisdom
teeth.” This also should be noted in regard to the study of
evolution and the related problems of biology, that though all the
generalisations reached must be based on the research and observa-
tion of zoologists, botanists, and naturalists, and are seldom fully
appreciated by those who have little personal acquaintance with
the facts, yet sound and useful conclusions may be, and often are,
obtained by those who have had no discipline in concrete scientific
work.

Besides the general question of organic evolution there are
special subjects which the student of biology must learn to think
about: Protoplasm, or “the physical basis of life;” Repro-
duction, Sex, and Heredity, or “the continuance of life;” and
Animal Intelligence, or “the growth of mind.” Before passing
to the literature on these subjects, it may be noted that there are
two general works of pioneering importance, namely, Plerbert
Spencer’s Principles of Biology (2 vols., Lond., 1864-66), and
Ernst Haeckel’s Generclle Morphologic (2 vols., Berlin, 1866).

Protoplasm. — Of this the student should learn how little we
know. Yet this is not very easy, since the most important recent
contributions, such as those of Professors Piering and Gaskell, are
inaccessible to most. The gist of the matter, however, may be
got hold of by reading : (a) three articles in the Encyclopedia
Britannica , “Physiology” (Prof. M. Foster), “Protoplasm”
(Prof. P. Geddes), and “ Protozoa” — the large type — (Prof. E. Ray
Lankester) ; (h) the Presidential Address to the Biological Section
of the British Association, 1889, by Prof. Burdon Sanderson
(Nature, xl., September 1889, pp. 521-526); and (c) the article
“Protoplasm” in the new edition of Chambers’s Encyclopedia.
Of the abundant literature on the philosophical questions which
the scientific conception of living matter raises, I shall mention
Huxley’s address on “The Physical Basis of Life,” published
among his collected essays; Hutchison Stirling’s tract, “As
regards Protoplasm;” the chapter on “Vitalism” in Bunge’s
Physiological Chemistry (translated, London, 1890).

Reproduction, Sex, and Heredity. — For adult students,
and no others should be encouraged to face the responsibility of

366

API'.

The Study of Animal Life

inquiry into such matters, the most convenient introduction will
be found in The Evolution of Sex (Contemporary Science Series,
Lond., 1889), by Prof. Geddes and myself. In that work there
are references to others. A survey of modern opinions and con-
clusions in regard to heredity may be obtained from the article in
Chambers’s Encyclopedia, whence the student will pass unbiassed
to the essays of Weismann, Papers on Heredity and Kindred
Subjects (translated by E. B. Poulton, S. Schonland, and A. E.
Shipley, Oxford, 1889), to the works of Francis Galton, especially
his Natural Inheritance (Lond., 1889), and to other important
books mentioned in the article referred to.

Animal Intelligence. — A recent work by Professor C. Lloyd
Morgan, Animal Life and Intelligence (Lond., 1890), supplies the
best introduction to those interesting questions in the discussion of
which the biologist becomes a psychologist. The most reliable
treasury of facts is certainly G. J. Romanes’s Animal Intelligence
(Internat. Sci. Series, 4th ed., Lond., 1886), to which may
be added Couch’s Illustrations of Instinct (1S47), Lauder Lindsay’s
Mind in Animals (1879), Buchner’s A us deni Geistcsleben der Thiere
(2nd ed., Berlin, 1877) and Liebe und Liebesleben in der Thierwelt
(Berlin, 1879) ; Max Perty, Ueber das Seelenleben der Thiere (Leipzig,

1876) ; Houzeau, Des Facultes mentales des Animaux (Brussels,
1872). Of unique value is the work of A. Espinas, Des Societes
Animates, Etude de Psychologie comparee (Paris, 1877). See also
P. Girod, Les Societls chez les animaux (Paris, 1890). I should
also mention that Brehm’s Thierleben (1863-69), a great work now
in process of re-edition (10 vols., Leipzig), is a marvellous
treasury of information in regard to the ways and wisdom of
animals, and that we have in Verworn’s Psycho-Physiologische
Protisten Siudien (Jena, 1889) a very interesting and important
study of the dawn of an inner life in the simplest animals or
Protozoa. Of the ingenious work of animals, an admirably terse
description is given in F. Houssay’s Les Industries des Animaux
(Paris, 1889). For theories of instinct, see especially Romanes,
Mental Evolution in Animals (Lond., 1883); Darwin, Origin of
Species ; Wallace, Contributions to the Theory of Natural Selection-,
Spencer, Principles of Psychology and Principles of Biology ; G. H.
Lewes, Problems of Life and Mind (Lond., 1874-79); Samuel
Butler, Life and Habit (Lond., 1S7S) ; J. J. Murphy, Habit and
Intelligence-, E. von Hartmann, Das Unbewusste vom Stand-
punkte der Physiologic und Descendenztheorie (2nd ed., Berlin,

1877) ; Schneider, Der Thierische Wille (Leipzig, 1880) ; Eirner,
Organic Evolution ; Weismann, Papers on Heredity.

The Fact of Organic Evolution. — The student’s first task
in regard to Evolution is to make himself acquainted with the

II

Some of the “ Best Books ” on Animal Life 367

arguments which show that the animals and plants now alive are
descended from simpler ancestors, these from still simpler, and
so on back into the mists of life’s beginnings. To realise that the
present is child of the past is to realise the fact of Evolution, and
the surest way to grasp the biological verification of this fact is to
undertake a course of practical study. Failing this, we must, I
suppose, read up the subject. Romanes’s Evidences of Evolution
(Nature Series, Lond.) gives a convenient statement of the case,
and his Rosebery Lectures will be more exhaustive. Clodd’s
Story of Creation: a plain account of Evolution (Lond., 1888)
sums up the evidence in small compass ; another very terse state-
ment will be found in H. De Varigny’s Experimental Evolution
(Lond., 1892); Haeckel’s Natural History of Creation (Berlin,
1S6S) — the most popular of his works, now in its eighth edition
(Jena, 1S90) — is available in translation (Lond., 1879); Huxley’s
American Addresses (Lond., 1877) have even greater charm of
style; Carus Sterne’s Werden und Vergehen (3rd ed., Berlin,
1 886) is perhaps the best of all popular expositions; while the
thorough student will find most satisfaction in the relevant
portions of Darwin’s Origin of Species, and Spencer’s Principles
of Biology.

History of Evolution Theories. — As the idea of Evolution
is very ancient, and as it was expounded in relation to animal life
by many competent naturalists before Darwin’s intellectual coin
became current throughout the world, it is unwise that students
should restrict their reading to Darwinian and post-Darwinian
literature. The student of Evolution should know how Buffon,
Erasmus Darwin, Lamarck, Treviranus, the St. Hilaires, Goethe,
even Robert Chambers, and many other pre-Darwinians dealt with
the problem. Those who desire to preserve their sense of historical
justice should read one or more of the following : Huxley’s article
on “ Evolution ” in the Encyclopaedia Brilannica ; Samuel Butler’s
interesting volume on Evolution Old and New (Lond., 1879);
Perrier’s Philosophic Zoologique avant Dai-win (Paris, 1884); the
historical chapters of Haeckel’s Natural History of Creation ;
Carus’s Geschichle der Zoologie, and some other historical works
already referred to (p. 355) ; A. de Candolle’s Hisloire des
Sciences et des Savants depuis deux Siicles ( Geneve, Bale, 1883);
Carus Sterne’s (Ernst Krause’s) excellent work, Die Allgemeine
l Veltanschauung (Stuttgart, 1889) ; De Quatrefages, Charles
Darwin el ses prlcurseurs frangais (Paris, 1870).

Darwinism. — The best account of the Darwinian theory of
Evolution, especially of the theory of natural selection which
Charles Darwin and Alfred Russel Wallace independently elabo-
rated, is Wallace’s Darwinism (Lond., 1889). From this the

368

AI'I*.

The Study of Animal Life

student will naturally pass to the works of Darwin himself- — The
Origin of Species by means of Natural Selection ; or, the Pre-
servation of Favoured Races in the Sl> uggle for Life (Lond.,
1859) ; The Variation of Animals and Plants under Domestication
(2 vols. , Lond., 1 S6S) ; The Descent of Man, and Selection in
Relation to Sex (Lond., 1871), etc. ; the earlier works of Wallace,
especially his Contributions to the Theory of Natural Selection
(Lond., 1871); Spencer’s Principles of Biology — cf his articles
on “ The Factors of Organic Evolution ” {Nineteenth Century,

1 886); Haeckel’s Generelle Morphologie, and Natural History of
Creation. As a popular account of Darwin’s life and work, Grant
Allen’s Charles Darwin (English Worthies Series, 3rd ed., Lond.,

1 886) has a deserved popularity ; G. T. Bettany’s similar work
(Great Writers Series, Lond., 1886) has a very valuable biblio-
graphy ; but for full personal and historical details reference must
be made to the Life and Letters of Charles Darwin, by his son
Francis Darwin (3 vols., Lond., 1887).

Recent Contributions to the Theory of Evolution.—

At the present time there is much discussion in regard to the
factors of organic Evolution. The theory of Evolution is still
being evolved ; there is a struggle between opinions. On the
one hand, many naturalists are more Danvinian than Darwin was,
— that is to say, they lay more exclusive emphasis upon the theory
of natural selection ; on the other hand, not a few are less Darwinian
than Darwin was, and emphasise factors of Evolution and aspects
of Evolution which Darwin regarded as of minor importance.

Of those who are more Darwinian than Darwin, I may cite as
representative : Alfred Russel Wallace who, in his Darwinism,
subjects Darwin’s subsidiary theory of sexual selection to destructive
criticism ; August Weismann who, in his Essays on Heredity,
denies the transmissibility of characters acquired by the individual
organism, as the results of use or disuse or of external influence ;
and E. Ray Lankester, see his article “ Zoology ” in the Encyclo-
pcedia Britannica, and his work on the Advancement of Science
(Lond., 1890). The student should also read an article by Prof.
Huxley, “The Struggle for Existence, and its Bearing upon Man”
in the Nineteenth Century, Feb. 1888.

' See also : —

Samuel Butler, Evolution Old and New (Lond., 1879), Luck or
Cunning (Lond. , 1887), and other works.

Prof. E. D. Cope, Origin of the Fittest (New York, 1887).

Prof. G. H. T. Eimer, Organic Evolution, as the Result of the
Inheritance of Acquired. Characters, according to the Laws of
Organic Growth (Jena, 1888). Trans, by J. T. Cunningham
(Lond., 1890).

II

Some of the “ Best Books ” on Annual Life 369

Prof. T. Fiske, Outlines of Cosmic Philosophy (Lond. . 1874), Dar-
winism, and other Essays ( Lond. , 1875).

Prof. P. Geddes, Article "Variation and Selection,” Encyclopedia
Dritannica ; "Evolution,” Chambers’s Encyclopedia, new ed.
Cf. The Evolution of Sex, and forthcoming work on Evolution,
Organic and Social.

E. Gilou, La Lutte pour le Bien-etre (1890).

Rev. J. T. Gulick, Divergent Evolution, through Cumulative Segre-
gation (Journ. Linn. Soc. xx., 1888).

P. Kropotkine, "Mutual Aid among Animals," Nineteenth Century
(Sept, and Nov. 1890).

Lanessan, La Lutte pour l' Existence et l' Association pour la Lutte
(Paris, 1882).

Prof. St. George Mivart, The Genesis of Species (Lond., 1871),
Lessons from Nature (Lond., 1876), On Truth (Lond., 1889).

Prof. C. Lloyd Morgan, Animal Life and Intelligence (Lond.,
1890).

Prof. C. V. Nageli, Mechanisch - physiologische Abstammungslehre
(Miinchen and Leipzig, 1884).

Prof. A. S. Packard, Introduction to the Standard or Riverside
Natural History (New York and Lond., 1885).

Dr. G. J. Romanes, Physiological Selection (Journ. Linn. Soc. xix. ,
1886), and forthcoming Rosebery Lectures on the Philosophy
of Natural History.

Prof. K. Semper, The Natural Conditions of Existence as they affect
Animal Life (Internat. Sci. Series, Lond., 1881).

Dr. J. B. Sutton, An Introduction to General Pathology (Lond.,
1886). Evolution and Disease (Contempor. Sci. Series, Lond.,
1890).

INDEX

Absorption, 145
Acacias guarded by ants, 29, 30
Acquired characters, 329-336
Actions, automatic, 155
habitual, 155
innate, 155
intelligent, 155

Alternation of generations, 189
Amoeba, 213
Amphibians, 9, 256, 257

parental care among, no, in
Amphioxus, 252
Angler-fish, 118
Animalculists, 191
Animals, everyday life of, 1-124
domestic life of, 95, 116
industries of, 117-124
life-history of, 184-203
past history of, 204-209
social life of, 67-94
and plants, resemblances and
contrasts, 167-171
relation of simplest to more
complex, 171-174
Annelids, 231-234
Antlers, 279
Ants, 78-84

and aphides, 119, 120
and plants, 29
Aphides, 82, 312
multiplication of, 38
Arachnida, 243
Archoplasm, 183

Aristotle, 283, 284
Armour of animals,. 34, 35
Artemia, 310, 311
Arthropods, 10, 238
Atavism, 322
Autotomy, 64-66
Axolotl, 309

Backboned animals, 9, 222-247
Backboneless animals, 9, 10, 248
272

Bacteria, 21, 22
Balance of nature, 19-21
Balanoglossus, 9, 249, 250
Bathybius, 219
Beauty of animals, 15-17
Beavers, 25, 74, 75
Bees, 78-84

Biology, justification of, 34-50
Birds, 9, 264-267

parental care among, 114, 115
Blind animals, 305
Body, functions of, 144-149
parts of, 174-183
Books, 351-369
Boring animals, 25
Bower birds, 98
Brachiopoda, 235
Brine-shrimp, 310, 31 1
Buffon, 286

Caddis w'orms, 61
Carbohydrates, 134

II

37 2 The Study of Animal Life

Caterpillars, 50, 51
Cats and clover, 29
Cave-animals, 334
Cell-division, 158-183
Cells, 128, 147, 179-183
Centipedes, 241
Cestoda, 229
Chaetopoda, 231-233
Challenger Expedition, 5, 6
Chamasleons, 52
Chemical elements, 135

influences in environment, 309,
3i3

Circulation, 146
Classification of animals, 8-1 1
Ccelenterates, 222-228
Cold, effect of, 313
Colonies, 70, 71
Colour-change, 52, 53
Colouring, protective, 48, 49
variable, 49-51
Colours of animals, 49-53
of flat-fishes, 315
Commensalism, 68, 69
Competition, internal, 67
Concealment of animals, 47
Conjugation, 214
Consciousness, 1 50-152
Co-operation, 69
Corals, 26, 27, 227
Coral snakes, 59
Courtship of birds, 96
mammals, 96
spiders, 101-105
Crabs, masking of, 61, 62
and sea-anemones, 68, 69
Cranes, gregarious life of, 73
Crayfish, 25
Crocodilians, 263, 264
Cruelty of nature, 43-45
Crustacea, 239, 240
life-history of, 198-202
Cuckoo, 1 14, 1 15
Cuttlefish, 52, 66
Cyclostomata, 252

Darwin, Charles, 292-296
Erasmus, 288, 289

Deep-sea fishes, 2 56
life, 6

Descent of man, 341-345
Desiccation, 41-43
Digestion, 145
Distribution of animals, 3-8
Disuse, results of, 305, 306
Division of labour, 69-71, 143,
144

Dormant life, 41-43
Drought, effect of, 41-43

Earthworms, 22-24
Echinoderms, 10, 65, 66, 235-238
Ectoderm, 196
Eggs, 191, 192
Elaps, 59

Elephant hawk-moth, 59
Encystation, 41
Endoderm, 196
Environment, 306-319
Ephemerides, 106, 107
Epiblast, 196
Epigenesis, 324

Evolution, evidences of, 273-281
factors of, 299-302
theories, history of, 282-301
of sex, 188

Extinct types, 206, 207

Family, evolution of, 91
life, 91
Fats, 134
Feigning death, 66
Fertilisation, 193-195
Filial regression, 338
Fishes, 9, 253-256

parental care among, 109, no
Flight of birds, 123, 124
Flowers and insects, 28, 29
Flukes, 229

Food, influence of, 310-313
Freshwater fauna, 6-8
Friar-birds, 59
Frog, 258

Function, influence of, 303
GastrjEA theory, 197

Index

37 3

Intelligence, lapse of, 166
Intelligent actions, 155
Iron, importance of, 19
Isolation, 300, 301
Ivory, 31

Jellyfish, 226

Kallima, S3
Kidneys, work of, 145

Gastmla, 195, 196
Genealogical tree, 12, 13
Geological record, imperfection of,
205

Germ-plasma, 328
Giant reptiles, 259
Glow-worm, courtship of, 100
Gregarines, 21 1
Gregarious animals, 71-74
Grouse attacked by weasel, 40

Habitat, change of, 47
Habitual actions, 155
Haeckel, 298
Hagfish, 253
Halcyon, 116
Hatteria, 260
Heat, influence of, 313
Heredity, 320-339
Hermaphroditism, 188
Hermit-crabs, masking of, 63
Hirudinea, 234
Homes, making of, 121-123
Hornbill, brooding of, 114
Horse, pedigree of, 278
Hunting, 118, 119
Huxley, 298
Hydractinia, 69, 70
Hypoblast, 196

Ichneumon flies, 64
Idealism, 142
Impressions, 151
Industries of animals, 116-124
Infusorians, 21 x
multiplication of, 38
Innate actions, 155
Insects, 241-243
parental care of, 108
and flowers, 28
Instinct, 153-166
origin of, 163-166
Instincts defined, 11
incomplete, 158
mixed, 163
primary, 163
secondary, 163
Insulation of animals, 46

Lamarck, 289-292
Lamprey, 252
Lancelet, 9, 252
Land animals, 8
Leaf insects, 54
Leeches, 234
Lemming, Ross’s, 50
Lemurs, 46

Life, chemical elements of, 135-
137

energy of, 127
haunts of, 3-8
machinery of, 130, 131
origin of, 140-142, 280
struggle of, 32-45
variety of, 3
wealth of, 1-17
Light, influence of, 315, 316
Liver, work of, 145
Living matter, 131-135
Lizards, 260

Love of mates, 90, 91, 96

and care for offspring, 105-116
and death, 106
Luciola, courtship of, 100
Lucretius, 284, 285

Macro pod, parental care of, no
Mammals, 9, 267-271
Man as a social person, 94

considered zoologically, 340-
346

Marine life, 3-6
Marsupials, 46
Masking, 61-63-
Materialism, 141, 142

374 '

The Study of Animal Life

Mates, love of, 90, 91, 96
Mayflies, 106, 107
Metamorphosis of Insects, 243
Mesoderm or mesoblast, 196
Migration of birds, 74
Millepedes, 241
Mimicry, 57-61
Mites, desiccation of, 41, 42
Molluscs, 10, 243-247
Monkeys, 270, 271, 341
gregarious life of, 71
Monogamous mammals, 96
Moss-insect, 55
Moulting, 315
Movement, 144

Movements of animals, 123, 124
Mud-fish, 8
Mygale, 36
Myriapoda, 241

Natural selection, 295
Nematoda, 231 v

Nemerteans, 230
Nervous system, 148
Nudibranchs, 56
Number of animals, 14, 15
Nutrition, 144
Nutritive relations, 27, 28

Odours and sexual attraction,

105

Offspring, care for, 105-116
Ontogeny, 203
Ooze, 220

Organic continuity, 203, 326-329
Organs, 175

change of function of, 178
classification of, 178
correlation of, 176
order of appearance of, 175,
176

rudimentary, 178, 179
substitution of, 178
Orioles, 59
Ovists, 191
Ovum, 191-193
theory, 196

Oysters, mortality of, 43

Palaeontological series, 206
Palaeontology, 204-209
Pangenesis, 324
Parasitic worms, 229-231
Parasitism, 47, 48
Parthenogenesis, 189-193
Partnerships among animals, 68,
69

Perception, 151
Peripatus, 10, 240
Phasmidae, 53
Phenacodus, 269, 270
Phyllopteryx, 54
Phylogeny, 203
Physiology, 125-152
Pigeon, 275, 276
Pineal body, 260

Plants and animals, 19, 20, 28-31,
168-171

Polar globules, 193
Polyzoa, 235

Preformation theories, 191, 324
Pressures, effect of, 300
Protective resemblance, 53
Proteids, 134, 135
Protomyxa, 212
Protoplasm, 131-135
Protopterus, 41
Protozoa, 11, 210-221
colonial, 173, 174
classes of, 21 1
life of, 214

“immortality" of, 172
psychical life of, 215-218
structure of, 213
and Metazoa, transitionbetween,
88, 89, 171-174
Psychology, 149
Pupae of caterpillars, 50
Puss-moth, 63, 64

Radiant energy, influence of,
3!3-3l6

Recapitulation, 197, 279
Reflex actions, 155
Reproduction, 184-190
Reptiles, 9, 259-264
Respiration, 146

Index

375

Reversion, 322
Rhizopods, 212
Rotifers, 7, 42, 234
Round-mouths, 9, 252
Rudimentary organs, 277

Saccophora, 62
Sacculina, 48

Sea-horse, parental care of, no
Seasonal dimorphism, 314
Segmentation, 195
Sensations, 151
Sex, 96*

Sexualreproduction, 186-188
selection, 98
Shells of molluscs, 243
Shepherding, 1x9, 120
Shifts for a living, 46-66
Skunk, ss

Snails and plants, 30
Snakes, 260-263
Social inheritance, 337-339
life of animals, 67-94
organism, 93, 94
Societies, evolution of, 87
Song of birds, 96
Spencer, 297, 298
Spermatozoon, 192, 193
Sphex, 121

Spiders, courtship of, 101-105
bird-catching, 36
Sponges, xi, 222
Spongilla, 186
Spring, biology of, 95, 96
Starfish, 235

Stickleback, courtship of, 99
parental care of, 109, no, 122
Stinging-animals, n, 223-228
Storing, 120, 121
Struggle for existence, 32-45
Surrender of parts, 64-66
Symbiosis, 69

Tapeworms, 229
Termites, 24, 84-87
Tissues, 179, 180
Tortoises, 263
Toxotes, 118
Trematoda, 229
Tunicates, 9, 250, 251
Turbellaria, 228

Variation, 299

Vertebrata, characters of, 19, 248,
249

Vital force, 19
Vivarium, 20, 21
Volvox, 187

Wallace, 296, 297
Warning colours, 55, 56
Weapons of animals, 34
Web of Life, 18-31
White Ants. See Termites
Worms, 10, n, 228-235

Yolk, 195

Zoology, history of, 352-357

THE END

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