ttlQLOGY

OTHER WORKS BY J. ARTHUR THOMSON

THE WONDER OF LIFE

SECOND IMPRESSION

Fully illustrated by Colour and Line drawings.
Demy 8vo, cloth, gilt top, 125. 6d. net

DARWINISM AND HUMAN LIFE

FOURTH IMPRESSION (Second Edition)
Illustrated. Demy 8vo, 7s. 6d. net

The Times says ' " Professor Thomson is one of the most lucid
and able exponents of Darwinism."

LONDON: ANDREW MELROSE LTD.

LIFE OF A TARN : WATER-SPIDERS, TADPOLES, NEWTS

(I)
(FRONTISPIECE]

THE BIOLOGY OF
THE SEASONS

BY

J. ARTHUR THOMSON, M.A.

Regius Professor of Natural History in the University of Aberdeen

AUTHOR OF

"THE WONDBR OF LIFE," "DARWINISM AND HUMAN LIFE," "HEREDITY,"

"THE STUDY OF ANIMAL LIFE," "HERBERT SPENCER," "THE SCIENCE OF

LIFE," "OUTLINES OF ZOOLOGY," "AN INTRODUCTION TO SCIENCE";

JOINT-AUTHOR OF "THE EVOLUTION OF SEX " AND "EVOLUTION"

•I'M

WILLIAM SMITH

FOURTH IMPRESSION

LONDON: ANDREW MELROSE LTD.

3 YORK STREET, COVENT GARDEN, W.C.

1915

BIOLC

^

G

Published
Reprinted

May
September ign
February
December

PREFACE

THE aim of this book is to get at the gist or inwardness
of the seasonal drama, without going too minutely
into the details of the successive scenes. In other words,
it is a study of certain biological aspects of the seasons, not
in any sense a naturalist's year-book, that I have essayed.

The book is intended for all who enjoy the pageant of
the year and the drama of the seasons, and who see some-
thing of the import of the annual analysis — as if through
a prism — of the evolutionary flow of things. There is
some reason to believe that Man was helped to find himself
long ago by his discovery of the Year — with its educative
object-lesson of recurrent sequences and long processions
of causes. Similarly to-day we may be helped to live on
more equal terms with Time by getting back into close and
appreciative touch with the march of the seasons. But
if that touch is to be natural to men of to-day, it must be
scientific as well as practical and emotional. Hence this
contribution to a Biology of the Seasons. It is hoped that
it may be of particular service to those who have to conduct
courses of Nature-Study, which should certainly follow
the seasons as closely as possible.

I am well aware that this series of studies and sketches
— some more impressionist, some more analytic — cannot
be more than illustrative of the biological outlook on the
seasons. For it is a big problem to try to detect the
seasonal punctuation of individual development and of

vi PREFACE

racial evolution, to trace out the inter-relations of organic
rhythms and external periodicities. The ideal would be to
study the organismal drama of the year with the sympathetic
feeling of the old naturalists, such as Gilbert White, with
Darwin's dominant sense of correlation and evolution, and
with Spencer's grasp of the unity of science ! No one
knows better than myself how far my reach has exceeded
my grasp in this fascinating inquiry. Perhaps, however,
the book may give a stimulus to the serious study of
Phenology or Season-Lore.

I am not forgetful that many naturalists have studied
the life of plants and animals in its varied seasonal ex-
pression, and that many of them have found the study so
rich in reward that they have sought to attract others to
it. From Gilbert White's evergreen Natural History of
Selborne to Professor L. C. Miall's Round the Year — to
mention two books remarkable in their accuracy, insight,
and sincerity — there has been a succession of Naturalist
Year-Books. But the aim of this volume is at once more
general and more intimate. It is an attempt to get at
the underlying principles.

J. ARTHUR THOMSON.

MARISCHAL COLLEGE,

THE UNIVERSITY, ABERDEEN,

April 1911.

CONTENTS

PAGE

INTRODUCTION .....«» i

PART I
THE BIOLOGY OF SPRING

IMPRESSIONIST SKETCH . . . . -19

YOUNG THINGS. ... . . 26

THE TALE OF TADPOLES . . . -32
THE EEL-FARE ... ... 41

CATERPILLARS . . ... 51

RHYTHMS IN PLANT LIFE . . . .60

THE RETURN OF THE BIRDS . 68

SOME QUESTIONS CONCERNING MIGRATION . . -76

RE-AWAKENINGS . . . . . .86

SPRING FLOWERS . . . . . .92

PART II
THE BIOLOGY OF SUMMER

IMPRESSIONIST SKETCH " ." . . . -103

SUMMER FLOWERS » . ' . . . .112

SUMMER INDUSTRIES . . . . > . -123

COURTSHIP OF BIRDS . . . . . 135

THE SONG OF BIRDS • . . . . .148

THE NATURAL HISTORY OF NESTS . . . 157

BIRDS' EGGS . . . . . . . 170

WITHIN THE EGG • . . * , . . 179

LEARNING TO LIVE . . • . * . . 186
THE PLASTICITY OF LIFE ..... 197

ADOLESCENCE . . . . . . .211

vii

viii CONTENTS

PAGE

THE PLAY OF ANIMALS • . . . .218

THE DUST OF THE AIR ..... 229

THE EPHEMERIDES . . . . . . 233

PART III
THE BIOLOGY OF AUTUMN

IMPRESSIONIST SKETCH . ' ". . .' . 239

THE FALL OF THE LEAF . . .. . .250

SHOWERS OF GOSSAMER . . . . -255

THE SIGNIFICANCE OF PALOLO • .. . • . 261
AUTUMN FRUITS ...... 267

SEED -SCATTERING . . . . * • 274

THE WORK OF EARTHWORMS . . . . .281

DEEPER PROBLEMS OF MIGRATION . . ' . 285

THE STORY OF THE SALMON . . . . •••"* 299

AGAINST THE STREAM ..... ¥ 304

PART IV
THE BIOLOGY OF WINTER

IMPRESSIONIST SKETCH . ., . . -311

THE NATURAL HISTORY OF REST . . . . 323

HIBERNATION . . . * . . . . 332

THE WHITE WINTER COAT f§ , <|« . . • 339

THE SQUIRREL'S STORE . . . . . 344

JETSAM . . . . . . . . 346

OLD AGE AND DEATH. . . . . . ,,. 356

LIST OF ILLUSTRATIONS

I. LIFE OF A TARN : WATER-SPIDERS, TAD-
POLES, NEWTS .... Frontispiece

II. PUFFINS AT THEIR BREEDING-PLACE . . Facing p. 68

III. EARLY FLOWERS AND HUMBLE-BEE . . „ 88
IV. SPRING : LUPINS AND OYSTERCATCHER . „ 98

V. HERON FISHING. . . . . „ 128

VI. DIPPER ON A STREAM . . . . ,,152

VII. NESTING-PLACE OF KITTIWAKES . . „ 188

VIII. LAMBS AT PLAY „ 220

IX. SQUIRREL AND FALLEN LEAVES IN WOOD . „ 252

X. PARTRIDGES IN HARVEST FIELD . . „ 270

XL PTARMIGAN AND MOUNTAIN HARE . . „ 340

XII. A SHORE POOL, SEA- ANEMONES AND HERMIT-
CRAB . . « •* • • » 352

THE

BIOLOGY OF THE SEASONS

INTRODUCTORY

BY the Biology of the Seasons we mean the study
of the phenomena and phases of life — in plants
and in animals — in relation to the time of year with
which they are especially connected. That this is a very
natural — perhaps the most natural — method of biological
study will be at once evident to many. Perhaps it would
be evident to all, were it not that many of us, dwelling in
cities and becoming careworn, have lost much of that
interest and delight in the seasonal drama which is char-
acteristic of country-folk in happy conditions. Not that
these country-folk are given to talk much about it, a
silence which has given rise to the extraordinary idea that
the delights of the country were discovered by the town.

The old-fashioned appreciation of the seasons was ex-
pressed, as we all know, in many fairy tales and myths, such
as those of the Sleeping Beauty and of Proserpina, and it
needs but little insight to see that these are really " fairy
tales of science " — often, indeed, of surprising accuracy. In
this connection, it may be noted that naturalists owe thanks
to the poets for consistently helping to keep the appreci-
ation of the seasons alive. From Homer to Horace, from
Gawain Douglas to Thomson's "Seasons," from Tennyson
to Meredith's "Lyrics and Ballads of the Earth," there is a
I

THE BIOLOGY OF THE SEASONS

glorious succession of seasonal poetry. Here, as in many
other respects, poetry may instruct her stern and sometimes
rather superior sister — Science. But as the years go by,
will it not become plain that the poet, the physiologist, and
the philosopher (shall we not include the theologian ?), are
trying to say the same thing in different words ?

That the method of seasonal biological study is education-
ally sound is best proved by experiment. But it is perhaps
enough to ask the simple question : What kind of scientific
lore concerning living creatures would we most naturally teach
our children in Spring? This is a sensitive touchstone of
educational validity. Surely our tale should be of the open-
ing buds and the early flowers, the return of the birds and
the quickening of the chrysalids. Similarly in autumn, we
should inquire into the withering leaves, the ripening fruits,
the scattering of seeds, the farewells of the birds, and the
general sinking into sleep. Only thus can we lessen the gap
between learning and living ! And every year, since the
inquiry is not easy, we should return with more penetrating
questions to watch the endless pageant of the seasons,
studying each thing " in its time " when it is beautiful. The
seasonal order of studying " animated nature " — at first
along Natural History lines and later as a biological inquiry
— is practically convenient, and it keeps us in harmony with
out-of-door interests, both of work and of play ; but there
is an even deeper vindication. The seasons have subtle
influences on human life, and the natural phenomena of
the outer world will be studied with most organic sympathy at
the time of their occurrence.

" Four seasons fill the measure of the year ;
There are four seasons in the mind of man."

The older naturalists — before Darwin's day — made many
careful pictures of the life of plants and animals as it is lived

INTRODUCTORY 3

in Nature. The indefatigable patience, the keen observa-
tion, and the sympathetic insight of many of these pre-
Darwinian naturalists must remain as models to which in
these later days, with improved methods, we try to approxi-
mate. Gilbert White's " Selborne," above all, remains
evergreen. But the old records are for the most part con-
tributions to Natural History rather than to Biology. To
most of their authors there was wanting the biological key
which Darwin first taught men to use. We mean not merely
the idea of organic evolution, that the present is the child
of the past, though that is indeed the " Open Sesame " of
Nature — but other biological conceptions as well — of
protoplasm and its changes, of the rhythms of life, of effec-
tive response to external stimuli, of the correlation of
organs and of division of labour, and of the correlation of
organisms in the web of life.

The difference between the old naturalists and the new,
which came partly through Darwin's influence and partly
because the time was ripe, may be readily perceived if we
compare, for instance, the older naturalist-travellers with the
new. No one can dispute the virility — sometimes rising to
greatness — of the work done by Thomas Pennant, Peter
Pallas, Gesner, Humboldt himself, and the crowd of more
specialist -travellers who followed these ; but there is a
difference in kind between their results and those embodied
in Darwin's Voyage of the Beagle, and in other narratives of
naturalists' journeyings — by Wallace, Bates, Belt, Moseley,
Hickson, Hudson, Rodway, Scott Elliot, Alcock, and some
others. Biological ideas have become dominant ; analysis
has become more penetrating ; the pictures have a broader
perspective and a deeper insight. Through and through we
feel that the travellers are dealing, not merely with interest-
ing things that they are delighted to describe, but with an
evolutionary drama that they are trying to understand.

4 THE BIOLOGY OF THE SEASONS

Similarly we find in modern studies of plant and animal
life in our own country — of the shore-fauna or of the flora of
lakes, of birds and their nests, or of flowers and their visitors
— that the biological note is becoming more and more
dominant. In some cases it is obvious that the evolution
idea forms the unifying centre of the study. In the same
way, it is by an emphasis on underlying principles that a
Biology of the Seasons should differ from a Natural History
of the Year. And that is our aim in this book.

EXTERNAL PERIODICITIES

The physical fact of most importance in connection with
the biology of the seasons is the familiar one — that the sun
is our main source of energy, and that, according to our
seasonal relation to it, we get varying amounts of heat and
light. With this primary relation are associated many
secondary seasonal variations, — in rain-fall, barometric
pressure, winds, tides, and so on. The Biology of the Seasons
has for its central task an inquiry into the adaptations of
living creatures to the external periodicities, which we sum
up in a rough, popular way in speaking of Spring, Summer,
Autumn, and Winter. The astronomical division of the
year is familiar : — From the Vernal Equinox to the Summer
Solstice ; from the Summer Solstice to the Autumnal
Equinox ; from the Autumnal Equinox to the Winter
Solstice ; from the Winter Solstice to the Vernal Equinox.
But this precise division of the year is not very useful bio-
logically, and some compromise must be accepted.

Thus, for practical purposes, we may agree that in
North Temperate regions, Spring is late March, April, and
May ; Summer is June, July, and August ; Autumn is
September and October ; Winter is November, December,
January, February, and part of March. The basal fact,

INTRODUCTORY 5

from the biological point of view, is that the ratio of heat-
supply in summer to that in winter is as 63 : 37.

VITAL RHYTHMS

Since ever physiology had any meaning, men have been
aware of the twofold process of waste and repair that goes
on in the living body. On the one hand, there are as-
similative or constructive chemical changes, as the result
of which complex substances are built up ; on the other
hand, there are disruptive or destructive chemical changes,
as the result of which complex substances are broken
down. The two sets of processes together include most
of the important chemical changes in the body, which are
summed up in the term metabolism. There is general
agreement that, from the chemical point 0} mew, " the life-
process consists in the metabolism of proteids," as Pro-
fessor Verworn puts it.

Generalising from his studies on colour sensation,
Professor Hering was led to regard living (physiologically
considered) as an alternation of two kinds of activity,
both induced by stimulus, the one kind of activity tending
to storage, construction, assimilation of material ; the other
kind of activity tending to explosion, disruption, and
disassimilation. Certain cells of the liver, for instance, are
kept toned-up to be makers of animal starch or glycogen
— that is assimilation. But when the muscles of the heart
are kept toned-up to be continually oxidising carbon-
compounds in the muscle-substance — that is disassimi-
lation.

Generalising from his studies on nervous activities,
Professor Gaskell was also led to regard living (physio-
logically considered) as an alternation of two processes,
one of them a stimulated running-down or disruption

6 THE BIOLOGY OF THE SEASONS

(katabolism), the other a more autonomic winding-up or
construction (anabolism).

But without going further into interpretations, which
remain uncertain, we may say that all physiologists are
agreed about the fact, that there is in all living a twofold
process of waste and repair, of discharge and restitution, of
activity and recuperation. And it is the preponderance
now of the one, and again of the other, that constitutes
the fundamental rhythm of life. As it is said in Ecclesi-
astes iii. : "To everything a season ... a time to break
down and a time to build up ... a time to cast away
stones and a time to gather stones together ... a time
to get and a time to lose ... a time to keep and a time
to cast away."

Besides the alternation of predominant anabolism and
predominant katabolism, though ultimately dependent on
it, there are numerous periodicities in the life of organ-
isms. The growth of the embryo is sometimes markedly
periodic. Thus Dr. A. Fischel says of duck-embryos,
that " the growth of the whole length of the embryo as
well as that of the several regions of the body is periodic."
It is said of some very simple organisms that they can
continue to move only as long as a certain substance
within them holds out ; when that is used up there is no
movement possible until after a period of nutrition. They
have to be re-charged. So in nerve-cell and muscle-cell,
wonderful engines as they are, there is a necessary limita-
tion to the output. Rest must alternate with work. We
see a similarly fundamental periodicity in the see-saw
between nutrition and reproduction, between vegetating
and flowering. " A time to embrace, and a time to refrain
from embracing."

Our point is that living creatures are inherently pre-
disposed to be rhythmic, and that on this predisposition

INTRODUCTORY 7

the external periodicities operate. The fundamental
problem of the Biology of the Seasons is to trace the relations
between the external periodicities and the vital rhythms.
Our central thesis is that life is rhythmic, and that it is
punctuated by the seasons and by other external periodic
influences.

Let us take a few illustrations. Many vegetable cells,
such as simple Algae, feed during the day and divide at
night. The deeply rooted inherent contrast between nutri-
tion and reproduction is externally punctuated. Flowers
open and shut, wake and sleep, periodically. Biological
virtuosos with leisure have made " floral clocks." Some
flowers are intermittent even in their fragrance.

The lines of growth on shells and on some bones indicate
periodicity, like the rings of growth on a tree, or the rings
on the rattlesnake's rattle, and this self-registering of
alternations is widespread — as the four illustrations may
suggest — in organic nature. In most cases it seems that
the punctuation is from without, while the necessity of the
alternation is from within. We can read summer and
winter on the scales and otoliths of fishes, just as we
can read day and night on a bird's feather. The increase
to the scales in the summer period is different from that
in the winter period, and the daily variations in the bird's
blood-pressure are sometimes registered, when feathers are
a-making, by the beautiful cross-bars. There is periodic
waxing and waning of venomousness in snakes, and there
are well-known periods in some diseases. Even the times of
cock-crowing sometimes correspond to external periodicities
of temperature.

Some of the correlations between external and internal
changes admit of very direct interpretation ; thus we
understand at once that green plants are intensely active
during the day and relatively restful at night, the hidden

8 THE BIOLOGY OF THE SEASONS

process of " photo-synthesis " being necessarily at a
standstill in the dark.

That is a simple case, but many correlations re due to
a circuitous nexus, as in the case of the relatio between
the amount of sunshine in Spring and the abundance of
mackerel around our coasts. Mr. G. E. Bullen finds that
for the years 1903-1907 there appears to be a correlation
between the number of mackerel taken during May and
the amount of Copepod plankton, upon which the mackerel
feed, taken in the neighbourhood of the mackerel fishing
grounds during the same month. Mr. W. J. Dakin
shows that the food of the Copepods consists largely of
the vegetable organisms of the plankton, such as diatoms,
and of Infusorian-like organisms called Peridinidae. But
the production of this microscopic plankton, the " stock "
of the " sea-soup/' depends partly on the composition of
the sea-water, partly on the temperature, and partly on
the amount of light available. There seems to be no
correlation between the surface temperature and the
abundance of mackerel, but Dr. E. J. Allen of the Ply-
mouth Marine Laboratory, who has brought all these
facts eloquently together, has shown that there is a real
correspondence between the amount of sunlight and the
catches of mackerel.

In some cases the correspondence between external
events and vital events seems unmistakable, and yet we
cannot understand the connection. Thus Professor Kofoid
has brought forward some striking evidence of a correlation
between lunar changes and quantitative changes of river
plankton, which seems even more mysterious than the
connection between the full moon and the excitement of
lunatics, or between sun-spots and trade-strikes.

There are several correlations as certain as that between
the Spring sunshine and the supply of mackerel at Billings-

INTRODUCTORY 9

gate, in regard to which we must confess that we do not
see the r ional interpretation. And the case of the
mackerel f ads us to the result — very valuable in inter-
pretative .^science — that a genuine correlation may be
established through a circuitous nexus. It may turn out,
in spite of the phrase "all moonshine," that the moon
causes vital tides.

In the case of long-established correlations between
external periodicities and internal vital changes, it seems
that the former may come to be needed only as liberating
stimuli or trigger-pullers. The internal periodicity may
become, in the course of ages, so thoroughly ingrained
constitutionally, that it requires only an appropriate touch
at the appropriate time to keep the business going smoothly.
In this connection we may refer to Professor Semon's pretty
experiment with young acacias (Albizzia lophanthd). They
had never been exposed to the normal alternation of day
and night, to which their race responds by expanding and
closing the leaves. Semon exposed them to artificial days
and nights of six hours' or twenty-four hours' duration,
but the plants exhibited the twelve-hours' cycle quite
unmistakably — though just a little altered. After this
experiment, Semon exposed his plants to continuous dark-
ness or to continuous illumination. The twelve-hours'
cycle still manifested itself for a time, but gradually
became indistinct. Here we see the ingrained hereditary
periodicity struggling against inappropriate stimuli — in-
appropriate to an extent that could hardly ever occur in
nature.

It is said that the tropical African mudfish (Protopterus),
taken to North Europe and kept with abundant water, tends
to become dormant at what corresponds to the African
dry season, when it normally goes to sleep for half the year.
It is said that migratory birds in cages become restless at

ro THE BIOLOGY OF THE SEASONS

the proper season though they are living in conditions
of great comfort. In such cases the internal periodicity
seems to assert itself even in the absence of the normal
stimulus.

CURVES OF LIFE

It is useful, then, to think of the course of life as an
ascending and descending curve — sometimes like a semi-
circle, sometimes like an ellipse halved lengthwise, some-
times like a parabola, when seen from a distance. If we
get near it and peer closely into it, we find that the curve
has endless minor irregularities, like a pulse tracing or
like a barometer tracing. On the whole, however, there is
an up-grade, steep or gradual, from egg to embryo, from
embryo to larva, from larva to a miniature of the adult,
from this to the adolescent, and thence to the fully developed
organism ; then there is a crest, long or short, of maturity ;
and then there is a down-grade, marked by decreasing
vigour, sinking down through senescence to the nadir of
death.

We rather like to think of the complete life as a parabolic
curve — without beginning of days or end of years — for who,
in face of the facts regarding ancestral inheritance and the
continuity of the germ-plasm, can insist very dogmatically
on beginnings or endings? What we call the individual
is part of a larger life. It is like a particular form of wave
in the sea, individualised for a brief moment, but only
intelligible as part of a great system of currents.

Let us keep, however, to the broad facts. The creature
rises from the vita minima of early embryonic life to the
vigour of adolescence and to the full strength of maturity.
At its limit of growth it often reproduces, and this is, as
often, the beginning of a descent. Quickly or slowly, but

INTRODUCTORY il

surely, it sinks on the down-grade to the vita minima of
senescence, which ends in death. The contour of the curve
differs, of course, for different kinds of creatures, but the
broad fact of cyclic development remains.

In the case of annual plants or annual animals, our
problem is to compare the trajectory of the life-history with
the curve that serves to register graphically certain big
physical facts of the year, notably the distribution of solar
energy. And when the plant or animal lives for more than
a year — it may be for stretching cycles of years like the
North American Sequoias, one of which spanned the whole
period from the birth of Aristotle to the death of Darwin —
we have to collate the periodicities of the year with minor
undulations on the main life-curve.

THE LIVING CREATURE AND ITS SURROUNDINGS

In its broadest statement the central problem of the
Biology of the Seasons is to investigate the relation between
the changeful organism and its changeful environment
within the period of the year. But this relation is manifold,
not simple, and it obtains in various degrees of directness.

We do not know what life in principle is, but we may
describe living as action and reaction between organisms
and their surroundings. This is the fundamental relation
— the absolute dependence of living creatures on appro-
priate surroundings. In fact, the two are inseparable. The
living creatures are real just in the same sense as their
surroundings are real, and function is but a descriptive
term for the dynamic relations between them. Thus we
cannot abstract the living creatures from their sphere of
essential surroundings. When we try to do this they die —
even in our thought of them, and our biology sinks into
necrology.

12 THE BIOLOGY OF THE SEASONS

Huxley compared a living creature to a whirlpool in
a river ; it is ceaselessly changing, yet always apparently
the same ; matter and energy stream in and stream out ;
it is the unessential flotsam that has most permanence ;
the whirlpool has an individuality and in varying degrees
a unity, yet it is wholly dependent upon the surrounding
currents. One may push the whirlpool metaphor too far,
so as to give a false simplicity to the facts, for there is no
denying that when vital whirlpools began to be, there also
emerged what cannot be discerned in the crystal or in the
dewdrop — the will to live, a capacity of persistent experi-
ence, and the power of giving rise to other lives. The vital
whirlpool is a creative agent as well as a creature. To
ignore this is to attempt a falsely simple natural history.
But what Huxley's metaphor of the whirlpool does vividly
express is a great commonplace and a great truth — the
fundamental dependence of living creatures upon their
surroundings. We cannot understand either the whirlpool
or the trout apart from the stream.

A very important corollary of this fundamental every-
day relation has to do with development. In some way
which we cannot picture, the fertilised egg-cell contains
the potentiality of a particular living creature — a tree, a
daisy, a horse, a man. If this inheritance is to be realised
there must be an appropriate environment, supplying not
merely food and oxygen, but essential liberating stimuli
of many kinds. Without this "nurture" the inherited
" nature " can achieve nothing. The development of
every character implies the interaction of the two sets of
factors — the internal organisation and the external sphere
of influences.

Since the " nurture " that plays an essential part in
the development of " nature " is changeful, it often induces
modifications in the young organism, and this modifiability

INTRODUCTORY 13

by external influences is continued throughout life.
Different creatures differ greatly in their susceptibility, but
they are all in the grip of a complex environment which
acts on them in rough or in subtle ways. Whether we
think of the seasons or the climate, the soil or the sea, we
find that this environment is intricately variable. Indeed
every kind of plant and animal is continually passing into
a new environment of chemical, mechanical, dynamic, and
animate influences which play upon it. All through the
ages this has been going on; living creatures have been,
as it were, ceaselessly passing over a series of anvils on
which the hammers of external influences play, with tunes
of ever-increasing complexity. It is evident that every
increase in the fulness of life implies additional complexity
in the incidence of external forces. Every increase in
locomotive power, for instance, increases the multiplicity
and multiformity of action and reaction between the
animal and its surroundings.

Part of the Biology of the Seasons, then, consists in
studying the dints made on living creatures by something
unusual in the play of the inanimate hammers — by some
change in the surge of the wave, the swish of the wind,
the salinity of the water, the composition of the soil, the
humidity of the air, the temperature, the illumination, and
so on. The organism is continually running the gauntlet
of environmental forces, which may induce responses or
modifications. These may be defined as structural changes
in the body of an individual, directly induced by changes in
function or in environment, which transcend the limit of
organic elasticity, and thus persist after the inducing
conditions have ceased to operate. Thus the tanning
which follows prolonged sun-burning in the Tropics may
persist as a permanent modification throughout the rest
of the individual life.

14 THE BIOLOGY OF THE SEASONS

But besides seasonal modifications, we have to recognise
a possibility which is only beginning to be studied, which
adds to the complexity of the biological problem — the
possibility that external changes may serve as variational
stimuli, inducing germinal changes which find expression
in the next generation.

The ingenious zoologist, Professor Semon, has recently
propounded a theory which may be noticed in this con-
nection. It is called the theory of the " Mneme," and it is
based on the fact that when living matter is affected by a
stimulus its quality cannot be the same as it was before the
stimulus. There is some residual effect, which Semon calls
an engram. All stimuli, Semon believes, produce engrams,
and the sum of the engrams of a living creature is its
" Mneme " — its organic reminiscences we may almost say.
The " Mneme " may have particular importance in cases
where penetrating stimuli, like those of the seasons, recur
periodically, revivifying old impressions and re-enforcing
them.

Some biologists believe that this line of thought is
useful, and that by following it we may come to understand
how the results of experience may be treasured from
generation to generation, although individually acquired
modifications in the ordinary sense are not entailed. The
effects of a stimulus may radiate through the organism,
may pass from part to part by nerve paths and proto-
plasmic bridges, and may in some cases reach even the
germ-cells in their recesses, thus influencing the next
generation. This remains a speculation.

But apart from possibilities of inheritance, it seems to
us safe to say that the ceaselessly changing march of the
seasons brings to organisms — which are agents, not mere
pawns in the game — new possibilities of creation, of garner-
ing experience, of trading with time.

INTRODUCTORY 15

We have lingered over the relations between living
creatures and their surroundings, because this is in great
part the subject of the Biology of the Seasons, and because
the influence of surroundings on the creature is often spoken
of too glibly as if it were one and simple, whereas it is
manifold and complex.

BOOK I. — SPRING

BOOK I. — SPRING

IMPRESSIONIST SKETCH

ERMINAL, Floreal, Prairial "—these were the
VJF names given to the Spring months at a famous
Spring-tide, over a hundred years ago, when men in the
April folly of their hearts dreamed that they could make
all things new. But the new names proposed, which are
certainly not without merit, have passed away with many
other things ; the old names remain, and perhaps they are
well enough. They are certainly better than those of the last
section of the year, where the art of naming that began in
Eden touches low- water mark. The old names are well
enough, we say, for is not March a month of warring, of
elemental strife, when the sun gains his well-assured annual
victory ? And is not April indeed the month of opening ?
The earth that has been frost-bound opens, and the seedlings
lift their heads, drowsily nodding, " nutating," as the botan-
ists put it, bending and bowing to the different points of the
compass, swithering between the peace of automatism and
the pleasures of sentiency. The buds open, and the leaves
unfold,a literal " evolutio of inherited potentialities expressed
under an appropriate environment of liberating stimuli."
The spring flowers open and the newly awakened insects
visit them. Of a surety, April is the time of opening — of
the earth, of the seeds, of the buds, of the flowers, of the
eggs, and of the womb, of the song of birds, and of the heart
of man.

20 THE BIOLOGY OF THE SEASONS

As one of the simple poets of the seasons said —

*'Up! — let us to the fields away,
And breathe the fresh and balmy air ; 1
The bird is building in the tree,
The flower has opened to the bee,
And health, and love, and peace are there."

Natures's optimism in the Spring-tide is irresistible ; the
frost cannot stand before the sun. They bound Dionysus
fast, but they might as well have tried to stop the rush of
sap in the vines covering the hillside. Zagreon they cut in
pieces, but he had to be put together again. Gloomy
Dis robbed Demeter of her Proserpina, but did she not come
again out of Hades ? Baldur the beautiful was slain with
the wintry mistletoe, but if he did not come to life again,
he was at least well avenged by another member of his
inexhaustible race. Dornroschen was pierced by a cold
spindle, but she slept and did not die, and the Prince kissed
her awake. Likewise, in the torrid zone, where life is
conquered by heat, not by cold, the Phoenix was consumed,
only to rise triumphant from the ashes of his burning. Do
not all these images mean much the same thing, that life is
insurgent and indomitable ? The northern Winter seems to
slay, but the hurt is seldom beyond Spring's curing. Winter
seems to put out the fires of life, but the Spring breeze fans
them into rampant flame. The corn of wheat that seems
to die brings forth much fruit. The Spring's gospel of
resurrection is irresistible.

The Winter is over and gone, but it has been long and
hard. Month after month Demeter has been mourning in
our midst — a Mater Dolorosa — seeking her lost child every-
where, often angry and terrible, often plaintive and tearful,
veiling her lost beauty but not her deep distress. Yet all
the while she has shown the strong virtue of maternity.
For, explain it who will, she has nursed, without food or

IMPRESSIONIST SKETCH 21

drink, the tender life of Keleos, and the youth flourishes
bravely. Does this old story not refer to that common-
place of the biology of Winter that Mother Earth has been a
careful nurse of the seeds committed to her charge ? That
the seeds are " adapted " to the Earth is familiar to all, but
in common honesty we must recognise that without putting
herself about the Earth looks after them well.

In any case, we observe in Spring that the rise of tempera-
ture has quickened the seeds, prompting the formation of
nuclein compounds and the division of cells (which organic
growth implies). Ferments have dissolved the hard stores
of reserve-material into soft nutriment. The very minions
of Death — the Bacteria — have helped to loose the bands of
birth, and the seedlings are rising from the ground. For
now the anger of Demeter is stayed, Proserpina has returned
from the kingdom of the dead, mother and daughter rejoice
together. And in a world where all is so wonderful, " so full
of death, so bordering upon heaven," is there anything so
wonderful as this meeting of life and death, as this raising
of what we call dead into what we call living, as this power
that green plants have to win the sun's aid, that they may,
by secret alchemy, transmute the beggarly elements of
water, soil, and air into the bread and wine of life ? We can
understand the dying Keats saying that of all things the
most beautiful was the growing of the flowers — " the growing
of the flowers." And there will certainly be reason for deep
regret if the study of the Biology of the Seasons, in leading
students to a theory of " photo-synthesis/' loses the vision
of the returning Proserpina.

The great god Pan is with us again, tangibly but never
visibly. We feel him in the warm Spring breeze, and every-
where we hear his merry pipes. Now he is among the
rustling withered reeds, quickening them to leafage, and
setting the birds a-singing ; now he is over the rippling lake,

22 THE BIOLOGY OF THE SEASONS

swifter than any swallow. Yesterday we heard him in the
glen, good-humouredly tossing a naughty cuckoo's tidings
to one of her many lovers ; to-day he roams by the lake-
side, and sets the daffodils dancing. Their exuberance and
gracefulness are typical of the. Spring, as is their " abandon-
ment " when the breeze caresses them, and some are near
enough the water to be mirrored there.

But Pan's pipes are not always merry. He sighs eerily
through the gorge and among the crags, where Boreas,
in the winter, so ruthlessly slew Pitys, whom Pan loved.
What a terrible destruction that was ; acre after acre of
lusty trees, brought to the ground, like legions before some
inevitably victorious, because continuous, horde of bar-
barians. We are remembering some of the Perthshire
woods, after the terrible storm that swept the Tay Bridge
away.

See the God : who ever did ? But do we not catch in
these floating spider-webs the fringe of his flowing robe ?
Men saw it of old, for they called it Godsamer.

It is difficult to distinguish the various voices in the
Spring medley, and our myths are apt to get mixed ; now
it is Pan, and again it is the Pied Piper who gathers life
in his train ; now it is Zephyrus playing with Chloris, and
again it is Orpheus, whom none can resist. But the facts
are plain, and that is what most concerns us ; the birds,
who went forth before the winter, changing their season
in the night, and " wailing their way from cloud to cloud
down the long wind," have returned rejoicing with Spring
in their voices. Whether it be the naughty cuckoo, who has
hoaxed all the poets, or the dove, who is morally not
much better, or the virtuous stork on the roof-trees, or the
nightingale melodious, or the lark at heaven's gate — every-
where from the orchestra which gathers strength every
day, we hear but one motif, <( Hither, my love, here ; here

IMPRESSIONIST SKETCH 23

I am, here ; the winter is over and gone ; arise, my love,
my fair one, arise and come away."

Dornroschen, the Sleeping Beauty, has been kissed awake
again. One after another had striven in vain to win a
way through the barriers which encircled the place of her
sleeping ; but at length the Prince and Master came, to
whom all was easy — the sunshine of the first Spring day.
And as he kissed the Beauty, all the buglers blew, both
high and low, the cawing rooks on the trees, and the croak-
ing frogs by the pond, each according to his strength and
skill. All through the palace there was such a reawaken-
ing : of the men-at-arms, — we call them bears and hedge-
hogs ; of the night-watchmen, known to us as bats ; not
to speak of the carpet-sweepers, like the dormice and ham-
sters— all were reawakened. The messengers went swiftly
forth, we are told, the dragon-flies like living flashes of
light ; the bustling humble-bees, making a good deal of
fuss, but refreshing themselves considerably at " The
Willow Catkins " by the way ; the moths flying softly
by night on secret service. How accurate the old stories
are : " The scullery-boy got a long delayed box on the ear
when the cook awoke " ; I saw the wood-snail draw in
his horns as the thrush swept swiftly by.

These Spring days are the days of youth — of seedlings,
buds, and fresh blossom, of tadpoles, nestlings, and lamb-
kins : of which, as of children, there are two thoughts
which we cannot help thinking.

The first is a thought of Easter, of the forgiveness of
Nature, of its infinite power of making a fresh start. In
Autumn we saw the vine robbed of all its leaves — trans-
figured in their dying — and hard-bound by the frost ; but
Dionysus smiled at his captors, and now the tender vines
put forth a sweet smell. We saw the sloe in winter, bare
as a skeleton in the desert, but black ; we see it now covered

24 THE BIOLOGY OF THE SEASONS

with white blossom, which we almost mistook for sno\v
still unmelted. We saw the hedger strip the hawthorn
till it was pitiful in its nakedness ; we see it now covered
with bursting buds, and it will soon be the time of May-
blossom. From amid the withered leaves the wood-
anemones are rocking like foam-balls on a wreck-strewn
sea ; and from the ditches, just the other day black, empty,
and uninviting in the extreme, the marsh marigolds have
raised their golden cups — their King-cups — to be filled with
sunshine. We wished the birds farewell in Autumn as
they passed overhead to lands that keep the sun, and
now they are gathering around us again, and every swift's
scream seems a promise, not a threat. Every lark in the
meadow voices forth a promise. The butterflies seemed to
fade away with the withering flowers, but their successors
are flitting by. The shore-pools and the ponds seemed
but a little while ago empty of life, or thickly frozen over
— sullen at all events — but now, each is beginning to be
like a busy city. For as surely as the old things pass away,
so all things are made new. From what seemed a sealed
tomb, life has arisen indeed.

But, if we can express the second Spring thought, it
will be seen that there is a deeper sense in which these are
the days of new things. It is, we see, the time of marrying,
pairing, and mating.

" For the old god Pan hath taken a wife,
And the whole world shares their mirth.
And all things that be of their company
Are reft of rue and assoiled from strife
By the one great breath of the joy of life
That passes round the earth."

It is the time of giving birth to new lives. It is the time
when new lives, begun long since, indeed begin to be. In
all these young lives there is what is new ; no one of them
is quite like its parents, but each carries with it the promise

IMPRESSIONIST SKETCH 25

of better or worse ; in the phrase of the biologists, this is
the time of variations. It may be, indeed, that the new-
ness is simply that what was of evil in the parents has
been forgiven in their children, which is cause for rejoicing ;
but sometimes it is that the little child — be it human or
water-baby — really leads the race, as was said long ago.
It may be, of course — there's the rub — that the promise
is never fulfilled, for the playful lamb which we all so much
admire grows into a very stolid sheep, (man has such a
way of making young things stupid) ; the very active-
minded chick becomes a most matter-of-fact hen ; the
"promising" young anthropoid becomes a careworn,
abruti, and rather cross-grained, elderly ape. Need we
point the moral ? The fact — at once hopeful and tragic
— is that the young life is often ahead of its race. If the
promise be fulfilled, then the world makes progress, and
that is Spring.

But come, let us join in the mood of the season which
is joyous. Let us mix all our metaphors, and let us light
the Beltane fires (they are still always blazing at the proper
time in some parts of the North), and let us keep the
Floralia (they are still always kept in the South). For,
while biology is well, to enjoy the realities which it tries
to formulate is better ; and, as was said by one who knew
no fear of winter in his year —

" To make this earth our hermitage
A cheerful and a changeful page,
God's bright and intricate device
Of days and seasons doth suffice."

YOUNG THINGS

ONE of the dominant notes of Spring is youthfulness.
It is the season of young things — of seedlings,
buds, and young blossom, of tadpoles, nestlings, and
young lambs. It is the time of new beginnings, of hopes
and promises ; in a word, it is the time when all the world
is young. Let us consider some of the young things of
Spring.

One of the fundamental but inconspicuous Spring
phenomena is the multiplication of minute organisms in
the waters. They swarm with water-babies. Sometimes
the whole surface of the lake is green with minute plants,
and we speak of " the breaking of the meres/' The same
is true of pond and river, of estuary and sea, though it
must be remembered that in the great expanses of open
sea — the pelagic realm — the conditions of life are much
more uniform year in year out than in the shore waters
or the lakes. Everywhere the multiplication of minute
organisms is the necessary prelude to the general re-popula-
tion. A single Infusorian may be the ancestor of a million
by the end of a week ; water-fleas eat the Infusorians,
fishes eat the water-fleas, and so the basal multiplication
influences a long sequence of incarnations. A little one
becomes a thousand, and supplies a nutritive stimulus to
a long chain.

Young gnats and mosquitoes are among the many
very interesting " water-babies " to be found in stagnant
freshwater pools in Spring. The mother insect, who has

YOUNG THINGS £7

spent the Winter in hiding, lays two or three hundred eggs
on an early morning in Spring. She does so in such a way
that they adhere to form a minute raft — about a quarter of
an inch across — which floats on the surface of the pool, and
can neither be submerged nor wetted. Each egg is some-
what cigar-shaped, with the upper end pointed, and the
lower end with a lid, which opens to let the larva out into
the water. The larva speeds most of its time hanging
head downwards from the surface-film, through which it
protrudes a respiratory air-tube. Very delicate hair-like
organs sweep microscopic particles into the mouth. If you
push the larva below the surface it sinks to the bottom,
but it can jerk itself up again tail foremost. There are
no limbs, but the tail part can strike the water vigorously,
and there are numerous tufts of bristles on the sides of
the body.

The larva feeds and grows and moults, and after
three or four moults it is full-grown — almost half an inch
in length. It then passes into a pupa-stage, very markedly
contrasted with the larva, and within the pupa-skin the
transformation from larval to adult structure, which has
been in progress for some time, is accomplished. The
pupa has a strange shape, with a big " head-end " that
seems all out of proportion, and with a paired paddle at
the posterior end. It rests at the surface, head upwards,
breathing by two horn-like or trumpet-like tubes. It
does not eat at all, and when it is alarmed it has to swim
forcibly downwards, so buoyant is its body. After three
or four days of pupa-hood the cuticle splits along the back,
the limbs are pulled out of their sheaths, and the gnat
emerges, not without risk and difficulty. It rests for a
short time, standing on its own husk, and then flies off
into a very different world. The whole period of develop-
ment is about a month, and there may be many successive

28 THE BIOLOGY OF THE SEASONS

broods. Every one knows how fond the females are of
blood ; the males feed daintily on nectar, if they feed at
all, and spend most of their short life in aerial dances.

One of the irresistible general impressions is that of
the abundance of life, especially of minute life. As regards
animals, this is seen most convincingly by those who study
the sea, with its teeming surface population (the Plankton),
or who fix their attention on some particular area, such as
a shore-pool or a pond. It is an impression for a lifetime
to go into a fish-hatchery and see the rows of rocking
cradles in which the young fry are swarming, perhaps a
hundred thousand in one box. But from many different
sides we get the same impression — thousands of tadpoles in
the ditch, countless swarms of grubs and caterpillars on
land, clouds of mosquitoes rising from the marshes, hundreds
of seedlings from one oak tree, an innumerable army of
lemmings mustering in the valleys of the Tundra. Life
is like an inexhaustible fountain — a spring.

A correlated impression is of the abundance of death.
The mortality among the young is enormous. Out of a
million oyster-embryos only one survives. Every one re-
members Darwin's famous seed-plot in which so many lives
began and so few grew up. Out of 533 larvae of the large
garden white butterfly collected by Professor Poulton,
422 died from ichneumon parasites ; four out of every five —
a great mortality. The infantile mortality in one of our
British towns was 160 per thousand the other year. Every-
where we get the impression of a massacre of the innocents ;
" so careful of the type she seems ; so careless of the single
life."

Sometimes the thinning process takes strange forms,
as in the capsules of the great whelk (Buccinum undatum),
whose shell children hold to their ears that they may listen
to the fancied echo of the distant sea, or in the vases of the

YOUNG THINGS 29

common dog-whelk (Purpura lapillus), which are fastened
to the shelves among the rocks. The numerous eggs in
each capsule or vase are not all hatched at the same time ;
some are a little earlier than the others, and the pioneers
devour the laggards as they come on the scene — a curious
instance of cannibalism in the cradle, an extreme form of
the struggle for existence at the very threshold of life.

One of the biological certainties in regard to young
things is their extraordinary plasticity, their power of
acquiring modifications as the results of some peculiarity
in nurture. By modifications we mean structural changes
induced by peculiarities in surroundings or functioning.
Every inheritance implies an appropriate environment of
nutritive and other stimuli, apart from which the legacy
cannot be realised. The inherited nature requires its
appropriate nurture, and peculiarities in nurture — whether
of food or sunshine, of use or disuse, of education or the
lack of it — result in modifications. We must return to
this very important subject, but meanwhile we note one
of the general impressions of the Spring season, that young
things are plastic, much in the grip of their surroundings,
and very liable both for good and ill to put on veneer, to
acquire modifications which are neither inherited nor
transmissible.

The tricks that one can play with tadpoles, cater-
pillars, and other young things are endless ; and the extra-
ordinary modifiability of young children is one of the great
facts of life. Every one knows and feels this in a general
way ; poets like Walt Whitman and Matthew Arnold have
given it fine expression, but perhaps only the biologists
quite realise the plasticity of the young life. It is, within
limits, like clay in the potter's hands. This is the other
side of heredity, so to speak.

Another general biological impression that we get from

30 THE BIOLOGY OF THE SEASONS

watching many of these young things is that there is much
truth in the frequently exaggerated idea of recapitulation.
The conclusion that an animal climbs up its own genealogical
tree is not to be taken literally, and Haeckel's more stately
way of phrasing the idea, " Ontogeny tends to recapitulate
Phylogeny," requires numerous reservations. The living
creature is specific, itself and nothing else, from the very
start, and it may show this in unexpected ways and very
early in development ; but yet its early form and structure
may in many cases be accurately described as old-fashioned
and generalised. It is not till the sixth day that the chick
within the egg begins to put on distinctively avian features,
and it seems to us not inaccurate to say that during the
previous five days it has been following a path precisely
parallel to that along which a young crocodile travels.
In a great number of cases, it is true, the young creature
is a sort of nurse or vehicle of the definitive organism that
is to be, and its salient features are adaptive to peculiarities
of the larval life and not in the very least ancestral ; at
the same time, when we inquire into the details of the
organ-making (organogenesis) we often find that the
successive developmental stages bear a striking correspond-
ence to what we believe were the successive evolutionary
steps. For these and other reasons — based on animal and
human child-study — we adhere to a modified form of the
much-abused recapitulation-doctrine, believing that the in-
dividual development of an organism tends to be a general
recapitulation, often much condensed and telescoped, of the
historical evolution of its race.

When we observe the growing of young things, whether
they be seedlings or tadpoles, we have to reconcile two
sets of facts — organic inertia on the one hand and organic
divergence on the other. On the one hand, we see the
persistent tendency to complete hereditary resemblance,

YOUNG THINGS 31

and the deep-laid arrangements, beautifully simple withal,
for securing this. The child is as old as its parents, a chip
of the old block, a pendant from a continuous chain of
germ-cells. On the other hand, we see the expression of
what is perhaps even more primitive — the tendency to
vary, to be something new, to be creative. The living
creature is a Proteus. In a deep sense, the little child
leads the race. And there is no time when we realise this
so much as in Spring, which, being the great season of
birth, is also the season of making all things new.

THE TALE OF TADPOLES

r ¥ ~"*HE frogs are among the earliest heralds of the
Spring, for although their croaking (in March or
earlier) may not be particularly attractive in our ears,
it has the same deep motif as the nightingale's song.
It is a " love "-call. Awakening after a winter's lethargy
and fasting, the frogs creep out of the mud of the pond
and call to one another. They unite in couples, and the
eggs laid by the female in the water are fertilised by the
male just as they are laid. These eggs form the familiar
masses of " frog- spawn " that we see in the ditches and
ponds — often, it must be allowed, in places which a little
more intelligence would have avoided.

It is profitable to pause to take a good look at this frog-
spawn, for it illustrates a number of biological ideas, and
perhaps we may be fortunate enough to see with a pocket-
lens the eggs dividing into two, four, eight, and more cells,
as if they were being cut by an invisible knife. Each egg in
our common British frog (Rana temporaria) is about a tenth
of an inch in diameter ; it is almost entirely black, all but a
small white lower pole ; it is surrounded by a large sphere of
non-living jelly, corresponding to the white of egg in a hen's
egg ; and there is no egg-shell. The whole mass, often of
2000 eggs, sinks at first, but afterwards floats freely.

Let us consider the biological significance of these
spheres of jelly around the eggs, for it is very interesting to
notice how they are justified on count after count, though
they are non-living extrinsic investments. The spheres

THE TALE OF TADPOLES 33

buoy up the eggs and at the same time obviate overcrowd-
ing. In the little chinks between the spheres there are often
groups of green unicellular plants which liberate oxygen
in the sunlight and use up the carbonic acid gas which the
developing eggs produce — a most profitable association, a
miniature illustration of the balance of Nature. But there is
a fauna as well as a flora of frog-spawn, and the chinks are
tenanted by small fry — such as water-fleas and rotifers —
some of which eventually loosen the gelatinous envelopes,
helping the larval-frogs to escape. Others, it must be
admitted, seem to wait to devour. Once again, the en-
velopes of jelly are useful in lessening the risks of jostling
— which might be fatal to the delicate embryos — when the
wind raises waves in the pond, or when a water-hen or coot
splashes in among the spawn. Moreover, the j elly seems to be
unpalatable to most water animals, and it is so slippery that
few birds can make anything of it. Finally, it may be that
the clear spheres serve as so many greenhouses, enabling the
ova to make the most of the sun's rays. All this illustrates
the scientific view of Nature as an arena where efficiency in
any form always counts.

About a fortnight or three weeks after the individual
life began, that is, after fertilisation, the minute larvae are
hatched from the delicate envelope of the ovum, and begin
to wriggle about in the dissolving jelly. They are somewhat
awkward-looking, half-made creatures at first, and when they
emerge from the jelly they are mouthless, limbless, eyeless,
and gill-less. They attach themselves, often in long rows,
to water-weed, the adhesion being effected by a paired
cement-gland below the position of the future mouth. A
bulging on the ventral surface of the body indicates the posi-
tion of the still unused remains of the legacy of yolk.

Soon after hatching three pairs of external gills grow out,
the first much the largest, one upon each of the first three
3

34 THE BIOLOGY OF THE SEASONS

branchial arches. These are not comparable to the ex-
ternal gills of a young shark or skate, which are really
elongated internal gills projecting through the gill-clefts.
They are comparable to the true external gills seen in the
young of some very archaic fishes, still living to-day, the
Polypterus of the Gambia and some other African rivers, and
two of the mud-fishes, Protoptems from Africa, and Lepido-
siren from the Amazons. One or two days after hatching
(in our common Rana temporaria) another important
structure appears on the larva — the mouth is formed in the
centre of a groove in front of the adhesive organs, and
hundreds of small horny teeth are developed.

When the food-canal becomes open, four pairs of gill-
clefts break out from the pharynx, and a gill-cover overlaps
the first set of gills. These dwindle and are absorbed, their
place being taken by a second set of gills supported by the
hinder margin of the lower halves of four gill- arches. As
these are enclosed in a gill-chamber and as they form a
second set, it is natural to compare them to typical fish-gills.
But they are really in the strict sense external, and they are
certainly skin-covered. Each gill-chamber has at first its
opening, but that of the right side joins with that of the left.

About a month after hatching the larval frog is in many
ways fish-like : for instance, it has a two-chambered heart
which drives impure blood to the gills, which are enclosed by
a gill-cover. It swims by its laterally compressed tail,
which shows a well developed unpaired fin, without fin-rays,
however, which support the unpaired fins of fishes. In a
very general way it may be said that the developing frog
visibly climbs up its own genealogical tree. It is this
general idea, indeed, of recapitulation that makes the study
of the frog's life-history perennially interesting. It re-enacts
the epoch-making colonisation of the dry land, and in many
of its internal changes, e.g. in the making of the three-

THE TALE OF TADPOLES 35

chambered heart, it probably re-enacts what took place
very long ago — before the Coal-Measures were laid down
in Britain — when Amphibians evolved from a Piscine stock.
But what took the race long ages to accomplish is achieved
by the individual in a few days, — a fact so familiar that
we are apt to forget its marvellousness — the mystery of
cumulative and condensed inheritance.

With the acquisition of a mouth the larva begins to feed
eagerly, nibbling at plants in the water, and also eating
animal food. As a consequence it grows, and the food-canal,
in particular, becomes very long and coiled like a watch-
spring. It is interesting to notice the relatively great length
of the intestine during the predominantly vegetarian period,
for it is usual in the animal kingdom to find a diet of
vegetable food — which is somewhat slowly digested —
associated with length of food-canal or with some equiva-
lent of length. As the tail becomes stronger and the power
of locomotion increases, the horse-shoe shaped adhesive
organ is converted into two small discs which gradually
disappear.

A new stage is marked by the appearance of the hind-
limbs as minute projecting buds at the boundary between
trunk and tail. Why should hind-limbs appear earlier
than the fore-limbs, which are, moreover, much shorter ?
Investigation shows that they begin to develop at the
same time — a fact which gives additional point to the
question. The fore-limbs are delayed by the gill-cover,
which does not impede the hind-limbs, and they eventually
emerge, the left one through the " spiracle," the right one
by a rupture. Perhaps we get some insight into the
orderliness of developmental processes when we notice
that the microscopic lashes or cilia which have hitherto
covered the skin of the larva now disappear. In most
cases, except as regards reproduction, what we may call

36 THE BIOLOGY OF THE SEASONS

" Animate Nature " (for shortness) is conspicuously
economical.

After the appearance of the hind-legs, the larvae come
often to the surface to breathe. They are learning to use
their lungs, which have been slowly developing for some
time as pockets projecting into the body-cavity from the
under side of the gullet. The tadpoles are now about
two months old, and in having lungs as well as gills they
may be compared to the double-breathing Mud-Fishes or
Dipnoi. As the lungs become established and functional,
the gills dwindle, and an intricate series of internal changes
leads from an essentially fish-like heart and circulation
to the characteristic Amphibian arrangements.

After a period of hearty feeding, with consequent in-
crease in size and strength, the tadpole begins to show
signs of approaching metamorphosis. It loses its appetite,
it becomes much less energetic. The tail begins to break
up internally, its muscles and other structures become
disintegrated and dissolved, and most of the material
is swept away in the blood stream to help in building
up a better head. Wandering amoeboid cells, which are
present in almost all animals except threadworms and
lancelets, seem to play an important part in the extra-
ordinary process of absorbing the tail, working like sappers
and miners among the debris, dissolving some of the
material, carrying some away. In certain respects what
occurs is comparable to violent inflammation. It is like a
pathological process which has become normal, and thus
from watching tadpoles we get a glimpse of a deep-reaching
theory of disease as " a perturbation which contains no
elements essentially different from those of health, but
elements presented in a different and less useful order."
Often, at least, a disease implies a series of metabolic
changes which are not in themselves in any way extra-

THE TALE OF TADPOLES 37

ordinary — only they are out of place, out of time, and
out of order.

One of the many careful observers of the annual wonder
— the metamorphosis of the tadpole — gives the following
terse statement of some of the more obvious changes :
" The horny jaws are thrown off ; the large frilled lips
shrink up ; the mouth loses its rounded suctorial form
and becomes much wider ; the tongue, previously small,
increases considerably in size ; the eyes, which as yet have
been beneath the skin, become exposed."

As the tail shortens more and more, the tadpole, rapidly
ceasing to be a tadpole, recovers its appetite and feeds
greedily on animal matter, sometimes on its younger
fellows. The abdomen shrinks, the stomach and liver
enlarge, the intestine becomes relatively narrower and
shorter. The tail is reduced to a short projecting stump,
and, apart from this, the adult shape has been reached.
Disinclination for a purely aquatic life becomes marked,
and the young frogs clamber ashore. As they have lost
all trace of gills, they are apt to drown in aquaria unless
they have floating rafts to climb on to, or some other
means of breathing dry air.

It is difficult to say which aspect of the development
of tadpoles is most interesting. As we have seen, it is
interesting in its main features as a modified recapitulation
of that transition from aquatic to aerial respiration, from
water to terra firma, which must have marked one of the
most important epochs in the evolution of Vertebrates.

But it is equally interesting to go into minute detail
and notice that the young tadpole's small tongue has not
much muscularity about it ; that as the tongue increases
in size the muscles also increase, but yet are quite unable
to move the tongue, though perhaps of some service in
compressing glands ; and that, as the metamorphosis is

38 THE BIOLOGY OF THE SEASONS

accomplished and the frogling hops ashore, the muscles
of the tongue are at length strong enough to shoot out the
tongue on the day-dreaming fly. The peculiar interest of
this is that Amphibians were the first animals to have a
movable tongue, that of fishes being even worse than
flabby, entirely non-muscular.

It is very interesting to consider in the same way the
other momentous acquisitions made by the race of Amphib-
ians— such as fingers and toes, and the power of gripping
things, vocal cords, and the power of speech — though
how much they have to say in their extraordinary jabber
no one knows.

Another interesting consideration is the variety of
solutions that this one animal, the frog, offers to the
problems of its life. Even in mathematics, we believe,
there may be more than one solution to a problem, and
every one knows that this is true of the practical problems
of human life. There is considerable variety in the
solutions of the problems of Brodwissenscha/t, though in
strictness, we suppose, the fact of the matter is that the
conditions of the typical problems are diverse, and there-
fore the solutions are diverse. But our point is this, that,
to the two great problems of nutrition and respiration (if
they are really two, for is not oxygen a kind of food ?),
the frog offers in the course of its life-history an unusual
diversity of answer.

It will feed on its legacy of yolk, on unicellular Algae,
on the epidermis of aquatic plants, on the vegetable debris
in the water, on animal matter by the way, on its own
tail (of course in a sort of surreptitious phagocytic fashion),
on its own brethren, on dead things in the water (tadpoles
clean delicate skeletons beautifully), and, by and by, when
it comes to its own, after a remarkable gustatory curric-
ulum, it will feed on living insects and little else. Yet

THE TALE OF TADPOLES 39

the way it feeds as an adult, e.g. on beetles much too large
for it, is often far from saying much for its varied gas-
tronomic education.

And again, as regards the fundamental problem of
breathing, we find the newly hatched tadpole breathing
through its skin in the old-fashioned manner of earthworm
and leech ; then follow in succession, the first set of
external gills, the gill-clefts, the second set of external gills,
which are usually called internal ; then follows a period
with gills and lungs together ; then there is the transition
to terrestrial life with pulmonary and (retained) cutaneous
respiration ; finally, in winter, the hibernating frog,
retiring into the mud-fortresses of its remote ancestors,
breathes by its skin only.

Several experimenters have found that the numerical
proportion of the sexes in frogs appears as ij it were modi-
fiable by changes in the nutrition. Thus Professor Yung,
of Geneva, fed tadpoles with minced beef, and found that
the percentage of females was 78, instead of 54 as in the
control set in natural conditions. He fed another set with
fish flesh, and the percentage rose to 81, as against 61 in
the control set. In a third set, to which the flesh of frogs
was supplied, the percentage rose from 56 to 92 ! It has
to be noted, however, that subsequent experimenters have
not confirmed these results, which are also open to the
fatal objection that the sex of those tadpoles that died
was not determined. It may have been that the change
of diet affected the males prejudicially and favoured the
survival of females. While the results of the experiments
cannot, without further inquiry, bear the interpretation
originally put upon them, they are still interesting, even
if due to differential mortality. It is a well-known fact
that in some places, in natural conditions, the percentage
of females is very high, though 57 seems to be the average.

40 THE BIOLOGY OF THE SEASONS

Before leaving the tadpoles, interesting in so many
ways, let us think over the year's life of the frog. Through-
out the winter months the frogs lie near the pond, buried
in the mud, mouth shut, nose shut, eyes shut, with the
heart beating feebly, breathing through their skin, and
eating nothing. The awakening in Spring is followed
immediately by pairing and egg-laying, and the aquatic
juvenile life of the tadpoles occupies about three months.
In summer there is a remarkable migration to the fields
and meadows, and many hundreds of froglings, about the
size of a first-finger nail, are seen on the march from
the pond. The adults also migrate, and the meaning in
both cases is the same — that they seek out places where
insects abound. Of the many that go forth, only a remnant
returns, for there is great mortality in the fields, where
there are many physical risks and many alert enemies. The
grass snake alone accounts for a good many in some parts
of England. Those that escape — whether youngsters or
old experienced hands — return to the pond in the autumn,
and go into winter-quarters in the mud.

THE EEL-FARE

ONE of the sights of Spring is the "eel-fare," that
is to say, the migration of young eels from the
sea up the rivers. They are about 2j in. in length, and
like a very stout knitting-needle in girth. They come
in countless crowds, and they keep on coming for hours
sometimes — a seemingly endless procession, the head of one
almost touching the tail of another, and all hugging the
bank or at least avoiding the strong currents. Sunlight
seems to be an indispensable stimulus to their persistent
ascent of the stream, for when the sun went down behind
the hills the procession we were watching suddenly stopped,
the elvers had sunk into the mud or hidden beneath stones.
The sunset is their rest signal. Their brain is wound up
to go on — straight on — and wonderful feats are recorded
in the way of s warming-up the sides of waterfalls and
overcoming other obstacles. It has been said that those
that are going to be females go much farther up-stream
than those that are going to be males ; but this lacks
corroboration. It sounds rather like an ex parte asser-
tion.

These migrating elvers have been well known to field-
naturalists for many centuries, but it is only within recent
years that we have been able to tell whence they come and
whither they go. It seems that all the eels of North and
West Europe come from deep water in the Atlantic to the
west of the British Isles and France, and perhaps as far

south as the Canaries — the apparent spawning-grounds

4*

42 THE BIOLOGY OF THE SEASONS

being on a belt running from north to south along the
continental slope towards the eastern part of the Atlantic
depths.

The " mystery of the eel " has engaged the attention of
many naturalists, who have contributed to our present-
day approximation to a solution. The biggest contribu-
tions are four, (a) In 1880, Jacoby proved that eels
remained barren in fresh water, and suggested that the
sexual maturity was not attained until they had gone
far out into deep water, (b) About 1896, Grassi and
Calandruccio concluded, from their observations in the
Mediterranean, that the eel matures in deep water, where
its eyes become larger ; that it spawns in deep water, where
its eggs float ; that the development includes a meta-
morphosis, and that the larval form is the peculiar trans-
parent pelagic creature which had been called Leptocephalus
brevirostris. They found these in considerable numbers in
the deep water of the Straits of Messina, (c) About 1906,
Schmid found numerous specimens of this Leptocephalus
along a belt from the Faroes southwards, described the
metamorphosis into the " glass-eel " stage, and brought
forward evidence of a migration shorewards during the
process of change, (d) Another naturalist, Petersen, also
deserves credit for showing that what had been called
" silver " eels, with a silvery coat and big eyes, are the
mature forms of the " yellow " eels of the ponds. They
put on a " wedding garment " as they are about to go
down to the sea.

As neither the first nor the final chapter in the life-
history of the common eel is as yet known, neither the eggs
nor the spawning adults having been discovered, one
naturally asks for evidence in support of the statement that
has been made as to their birthplace. The evidence, which
we owe to the researches of Dr. Johs. Schmid, consists

THE EEL-FARE 43

in the discovery of places where the larvae of the eel
are actually the commonest fishes towards the surface.
Arguing by analogy from the case of other fishes where
great swarms of larvae occur near known spawning grounds,
Dr. Schmid infers that the birthplace of the eels must lie
along the belt of the abundant occurrence of larvae.

Though absolute certainty is awanting, there is good
reason to believe that the eggs are "bathypelagic," that is
to say, that they occur floating at considerable depths.
This is true of some other members of the eel family,
of argentines, and of other deep-sea fishes, and it must be
contrasted with cases like the herring, where the eggs are
dimersal (i.e. attached to the bottom), and cases like most
of our food-fishes, where the eggs are pelagic (i.e. floating
at or near the surface of the open sea).

It is probable that the eggs of eels are hatched in complete
or almost complete darkness, at a depth of at least 1000
metres, where there is a pressure of about 100 atmospheres
and a temperature of over 70° C. Nothing is actually known
of the first chapters in the development — the forming of
the body, the early nutrition — all is still in darkness till
we reach the stage known as the Leptocephalus.

For a long time naturalists have known of a thin, trans-
parent open-sea creature — which was called Leptocephalus,
and regarded as a peculiar kind of fish. By careful observa-
tions along various lines it has more recently been shown
that the Leptocephali — for there are several different
species — are stages in the life-history of eels. We shall
only mention two contributions. In 1864, the American
naturalist, Dr. Theodore Gill, now a veteran in the ranks
of ichthyologists, concluded on anatomical grounds that
Leptocephalus morisii was the larva of the conger-eel.
In the summer months of 1886, at the marine laboratory
of RoscofT, in Brittany, Professor Yves Delage observed

44 THE BIOLOGY OF THE SEASONS

the gradual transformation of a Leptocephalus into a young
conger.

Let us linger for a little over the Leptocephali. They
are about 3 in. long, almost as thin as knife-blades, and
as clear as glass, except that the iris of the eye is silvery.
In this transparency they resemble many of the open-sea
animals — " sea-butterflies," " salps," and the like — with
which they consort, and it may be that the character is of
protective value, for they are almost invisible in the water.
They are found in greatest abundance at a depth of about
fifty fathoms, but are often got close to the surface. They
seem to have a diurnal change in their level in the sea,
coming nearer the surface at night. They are said to
swim with beautiful undulating movements, more leisurely
than rapid, and they often remain quite still — at rest in
the water. So far as is understood, they do not feed and
therefore do not grow. They may be spoken of as the
second great chapter in the life-history of the eel.

At this point it may be explained that besides Lepto-
cephalus brevirostris, which is the larva of the common eel,
there are two other kinds of Leptocephali, which are the
larva of the conger-eel and of the deep-sea eel, and four
other kinds which have not yet been linked to their re-
spective adults. One of them, called Leptocephalus
hyoproroi'des, is of particular interest, because it is as yet
the only form in which it has been possible to trace back
the Leptocephalus stage to an earlier, not fully grown,
pre-Leptocephalus stage. In other words, the end of
Chapter I. is in this case known, and connected with
Chapter II. It is noteworthy that the pre-Leptocephalus
is also pelagic.

To return to the life-history. In the late autumn, so
the story goes, the knife-blade-like larvae of the eel begin to
undergo a slow metamorphosis, as the outcome of which

THE EEL-F ARE 45

they assume in miniature the semblance of their parents.
In the first period of change, the height of the body is reduced
so that a form of body results that is in the main eel-shaped.
Thus, out in the Atlantic, " glass-eels " or " transparent
elvers," are fashioned. " In contrast to the earlier flat
Leptocephalus stages these are now strong and swift as
arrows in their movements." During the second part of
the metamorphosis the length of the body is reduced, and
the elvers migrate, pressing in from the open sea to the
fresh water or the shallow coastal waters, where they can
complete their metamorphosis and begin again to feed and
grow. For the whole of the change is a fasting period, as
is so often the case in developmental transformations — a
biological justification of asceticism. And it lasts about a
year !

The remarkable diminution in length, which occurs in
the metamorphosis from the Leptocephalus to the
" glass eel " stage, amounts to i centimetre, and careful
weighings of the two stages have shown that the meta-
morphosis involves an actual loss of substance, the dry-
weight of the " glass-eels " being only one-third of that
of the Leptocephali. That means, of course, that during the
fasting period of eight or nine months there is a literal con-
sumption of a considerable part of the material of the body.

These results of the careful work of Dr. Schmid and
his colleagues can be readily enough summed up, but it
is of some importance to understand that the provisional
story of the life-cycle has been built up of numerous ob-
servations— which were not very striking by themselves.
Thus we read that the captures in May were all Lepto-
cephali, while those in September were mostly in process
of metamorphosis ; that the later stages in September
were nearer shore than the earlier stages, which points
to shoreward migration during metamorphosis ; and so on.

46 THE BIOLOGY OF THE SEASONS

The area on the continental slope away to the west
of the English Channel is regarded as the most northerly
of the main spawning places of the eel in the Atlantic,
and it is very interesting to notice that the recorded dates
of eel-fares in the various British rivers correspond approxi-
mately to the distances from the main spawning ground.
To give a few illustrations, " the elvers first appear at
Spain and far south at the French west coast (at Bayonne),
namely, in the last months of the year (October to December),
somewhat later farther north on the French west coast
in January, still more to the north in February, and in the
Channel in February to March. In South- West England
(Bristol Channel) the fishery also begins in February, or
rather in March." On the Danish North Sea coast the
ascent of the elvers begins in April or May, on Scottish
rivers, like the Tay and the Dee, it usually begins in May.
This is, of course, but a sample of the evidence that has
accumulated to show that the date of the eel-fare corre-
sponds, on the whole, with the distance the young eels have
had to swim from their spawning place. They are ready
to start about November, but they do not reach the Katte-
gat till May — after a long journey. The discovery of the
spawning grounds has also explained why such colossal
numbers of elvers are sometimes seen in the Severn — the
arms of the Bristol Channel form a huge trap for a large
contingent of the main migratory host.

What happens in the case of the common eel seems
to be paralleled in the case of the conger. It is a more
southern form, and its larvae do not come farther north
than Rockall. The Leptocephali do not occur over such
great depths as those of the eel, but there is the same sort
of metamorphosis and the same sort of shoreward migra-
tion. But the conger remains in the sea.

As we began by noting, the elvers pass up the rivers

THE EEL-PARE 47

in huge numbers, overcoming difficulties that seem at
first sight insuperable. They often " swarm " up the sides
of falls ; they may get up drain-pipes into ponds ; they
not infrequently make excursions into the damp grass of
meadowland. Perhaps no animal exhausts the possibilities
of habitat so thoroughly as the eel — it has experience of
the deep sea, the open sea, the shore, the river, the pond,
and even the solid earth !

They may remain in ponds for many years, growing
steadily larger year after year, for, like many other fishes,
they have no definite limit of growth. There is a record
of an eel that was kept in captivity " for upwards of forty
years, growing to a length of 4^- ft., being already of large
size at the time of its capture." But, however long they
may live and thrive in fresh water, they do not breed there.

Two or three rare cases are known of female eels taken
from fresh water which had well developed ovaries or
roes, but no evidence of spawning has ever been forth-
coming. Furthermore, the eels which are caught going
down the rivers to the sea in autumn are not in a ripe con-
dition, though it is probable that they very soon become
so under the stimulus of their old environment.

In the ordinary course of events, the females become
almost mature " silver " eels in seven or eight years (7-12
years) ; we have seen big individuals, approaching a yard
in length, descending the Dee at Aberdeen. The males
put on " silver" at an earlier age, usually about four and
a half years (four and a half to seven), and they are several
inches smaller than the females. The maximum dimensions
are 19 in. and 39 in. respectively.

The fact is, then, that as the eels approach maturity
they become restless and seek the sea, if they, may attain
unto it. For, in some cases, the pond which was with
difficulty reached by an elver, is not more easily left by

48 THE BIOLOGY OF THE SEASONS

an eel. An overland excursion is sometimes required, 01
a drain-pipe may serve. In passing from the rivers to
the sea the males are said to lead the way in some cases,
as statistics of capture seem to bear out. They go down
to the depths of the sea, from which there is certainly
no return. But whether they die after spawning, as is
probable enough, no one knows with certainty.

A life-history so weird and circuitous as that of the
eel raises many questions, and the need of some general
interpretation is obvious. To some extent that is supplied
by the theory to which many facts point, that the common
eel is originally a deep-water fish which has secondarily
taken to fresh waters, just as the salmon is a freshwater
fish which has secondarily taken to feeding in the sea.

Part of the argument is based on the fact that animals
usually go back to their original home to spawn. The toad
is in the main a terrestrial animal, but it spawns in the
water. The land-crab often lives far from the sea, but it
journeys to the shore at the spawning season.

Again, from the fact that most members of the eel
family (Anguillidae) are marine fishes and only a few enter
fresh water, we may infer that the habitat of the exceptional
minority is secondary. It is, furthermore, very signifi-
cant that, out of a total of about 150 species, about fifty
are found in the Deep Sea in the stricter sense, going down
to 2500 fathoms.

The deep-sea eel (Synaphobranchus pinnatus) of the
North-East Atlantic keeps to the abyssal habitat, which
was probably primitive for the common eel. Its larvae
have never been taken so near the surface as the Lepto-
cephali of the common eel, never, indeed, above about 50
fathoms. There is nothing to suggest a movement towards
the shore. On the contrary, the larvae sink during metamor-
phosis towards the floor of the sea, where they become mature.

THE EEL-FARE 49

To speak of the common eel as originally a deep-sea
fish requires, perhaps, the safeguarding statement, that
there is no reason to believe in the autochthonous abyssal
origin of eels. Before the eels colonised the great depths
they were probably littoral fishes, specialised for burrowing
in the mud, and for making their way through holes among
the stones. Perhaps this hypothetical, even more remote,
habitat has its organic reminiscence in the shoreward
migration of the glass-eels.

To the question why eels which have reached repro-
ductive age in rivers flowing into the North Sea, for in-
stance, should travel far out into the Atlantic to spawn,
it may be answered that most parts of the North Sea are
too shallow, and where the depths are sufficient the tempera-
ture is too low.

Let us revise the general sweep of the life-history of
this remarkable deep-water fish which has left the abysses
and has entered into intimate practical relations with
man. It probably begins its life below the 5oo-fathom
line on the verge of the Deep Sea in the stricter sense —
that dark, cold, calm, silent, plantless world. It develops
and starts in life, and feeds and grows, far below the surface.
It rises to the upper waters as a transparent, sideways
flattened, knife-blade-like larva. It is gradually trans-
formed into a glass-eel with an energetic disposition, and
after about a year it is one of a million elvers passing up
a river. If it is not fortunate, it may take much more
than a year to reach the feeling-ground, for which it has
doubtless some organic, deeply sub-conscious desire; those
that ascend the rivers flowing into the Eastern Baltic
have journeyed over 3000 miles. Eventually they pass
up the streams, and there is a long period of growth in
slow-flowing reaches and in fish-stocked ponds. There
is never any breeding in fresh water ; but after some
4

50 THE BIOLOGY OF THE SEASONS

years restlessness seizes the adults as it seized the larvae —
but a restlessness due to a reproductive, not a nutritive,
motive — and there is an excited return journey to the sea —
the verge of the deep sea — where, as far as we know, the
individual life ends in giving origin to new lives.

CATERPILLARS

THE sight of the first butterflies is always gladdening,
even when they are the mischievous cabbage whites
(Pier is). For it is an indication that summer is set-
ting in. Most of these early butterflies have spent the winter
in the pupa-state, hidden away in sheltered retreats. They
emerge and pair ; the females lay their eggs ; these develop
into the caterpillars which are often so abundant in the
summer months. As we have studied young creatures in
the sea and in the fresh waters, we may take caterpillars
as examples of young creatures on dry land.

A typical caterpillar — the larva of a butterfly or a moth —
shows a hard polished head and a body of thirteen rings.
The head is strengthened by a median shield and two side-
plates bearing half a dozen simple eyes and minute three-
jointed feelers — in marked contrast to the large com-
pound eyes and long feelers of the adults. In the service of
the mouth there are three pairs of minute appendages — the
mandibles and two pairs of maxillae. On the second pair
of maxillae, fused to form the labium, there is in many cases
a spinneret from which a thread of silk issues. In not a few
caterpillars there are also mandibular glands secreting a fluid
which is usually defensive, occasionally digestive as well.
Associated with the silk-glands, the old entomologist
Lyonnet found accessory glands, whose secretion seems to
glue one thread of silk to another and perhaps helps the
silk to harden quickly. Each thread of silk shows a glassy
core of pure silk, made at the expense of the living matter

5»

52 THE BIOLOGY OF THE SEASONS

of the cells of the silk-glands, and outside the silk there is
a delicate fatty sheath which can be removed by washing.
The caterpillars use the silk to attach themselves to twigs,
to save themselves when they are about to fall, to lower
themselves from a branch to the ground, and to make a
cocoon for the period of metamorphosis. But there are
many caterpillars that are not silk-spinners.

Returning to the structure of the caterpillar, we see that
the first three rings behind the head bear five-jointed legs
ending in a point. This region corresponds to the thorax
of the full-grown butterfly or moth, and though the legs of
the larva do not in the strict sense become those of the adult,
they correspond to them. Behind the thorax, and quite
continuous with it, is the abdomen, which consists of ten
segments. In most cases, however, the ninth is telescoped
and difficult to see. Short unjointed legs, ending in peculiar
gripping structures with a double crown of hooks, occur on
the third, fourth, fifth, and sixth rings of the abdomen,
and a large pair (sometimes transformed into protrusible
whips) is borne on the tenth and last. There are, of course,
occasional departures from the rule that there are five pairs
of pro-legs. Thus in the " loopers," which move in a
characteristic way, familiar in the common magpie moth
(Abraxas grossulariata), there are only two pairs.

There are paired breathing apertures, leading into air-
tubes or tracheae, on the first thoracic ring, and on the eight
foremost abdominal rings. Not infrequently the body is
thickly covered with hairs which have irritant properties ;
or instead of hairs there may be bristles, spines, or warts.
Some caterpillars have offensive thoracic glands ; thus those
of the puss-moth larva secrete formic acid. Inside the body
there are, of course, organs corresponding to those that we
possess — brain and nerve-cord, food-canal and associated
glands, complex muscles, air-tubes, a heart, excretory tubes,

CATERPILLARS 53

and large fatty bodies. It is not within our purpose to discuss
any of these things, but it is necessary to recognise that the
caterpillar is a very highly organised creature.

Most caterpillars lead an active life, moving about in
search of food. Some rove by day and others by night.
In some dim way they are aware of the appropriate food-
plants, passing others by, and certain kinds may often
be seen exploring in a most business-like fashion. The
procession caterpillars of the genus Cnethocampa, which
rest together in a huge common web, go on the march in
large numbers, sometimes in single file, sometimes in broad
ranks. In the Italian Riviera one of the procession cater-
pillars (Cnethocampa pityocampa) makes a great silken
shelter on the branches of the Aleppo Pine, and often eats
them quite bare, doing great damage. They are checked a
little by the larva of a beautiful beetle (Calosoma) which
" forces its way into the silken nest and destroys the inmates.
So voracious is this grub that it kills many more of the
caterpillars than it can possibly eat. It is wisely protected
by those who are interested in the preservation of the pine
forests." These procession larvae may be seen on the
march about the date of the vernal equinox, forming long
lines on the road, the head of one almost touching the tail
of another. As they go they sometimes secrete a composite
thread, continuous to their headquarters on the tree. It
has been shown experimentally that they instinctively follow
the leader, and that he may abdicate his position in favour of
another. The experiment has been tried of making a circle
of the procession, the head of the leader being brought into
contact with the hind end of the last on the file, and such a
circle has been known to go on circling for days — a fine
illustration of the non-intelligence of instinct.

The biological significance of the procession is that the
caterpillars are seeking for a suitable soft place in which to

54 THE BIOLOGY OF THE SEASONS

bury themselves for pupation. When they find it, they
mass together, and move round and round paying out silk
and loosening the soft soil. In this way they gradually sink
below the ground, where they lie dormant, undergoing
metamorphosis through the summer. The moths emerge
in autumn.

These destructive caterpillars are familiar sights in some
parts of the Riviera, and they have many interesting
features in addition to their processions. Thus the loosely
attached hairs, which are covered with fine recurved
booklets, are very irritant to many people (and not at all to
others), causing a rash on the skin when the caterpillars
are handled.

Mr. W. F. Kirby writes : " The hairs of the proces-
sionary larvae, which are very loosely attached and studded
with exceedingly fine and recurved hooks, cause violent
inflammation on the skin of men and animals, partly by thus
adhering to it, and partly in consequence of a fine dust with
which they are covered. On this account the neighbour-
hood of the nests of these larvae, which are intermingled
with these hairs, is dangerous, for the surrounding air is filled
with loose hairs and dust, which are liable to be inhaled, and
to give rise to internal inflammation and swellings, which
have sometimes caused death. The inflammation caused
by the hairs of the larvae may be relieved or averted by
rubbing the skin with oil."

Another feature in the life of caterpillars is their enormous
appetite. Some of them seem never to stop eating, and
a species of Polyphemus is said to eat 86,000 times its
own weight in a day. The contrast between this and the
dainty meals of the butterfly or its not infrequent fasting
is almost diagrammatic — the larva is the nutritive, vegeta-
tive, growing phase ; the adult is ascetic and reproductive.
In the great majority of cases caterpillars are vegetarian,

CATERPILLARS 55

and it seems that they can digest only the fluid parts of
their food, which sheds some light on the enormous quantity
eaten.

The extraordinary voracity of caterpillars is associated
with rapid growth, and this with periodic " moulting."
As in the other jointed-footed or arthropod animals (such
as centipedes, spiders, and crustaceans), the body is covered
with a chitinous cuticle — a layer not in itself living or
cellular, made by the underlying living skin. It is really
of the nature of a secreted shell ; it cannot grow, and it
has little expansibility. Therefore, as the caterpillar grows,
it is continually becoming too large for its protective
cuticle, and that has to be moulted. Five moults very
frequently occur. Every moult is extraordinarily thorough-
going, involving all the many intuckings of the outer layer,
and the caterpillar is emphatically out of sorts at every
moult. There seem to be serious respiratory difficulties,
and there is considerable inflammation. The moult is a
critical event in the life-history, and the process often
ends fatally.

After the caterpillar has reached its normal limit
of growth it passes, as every one knows, into a resting
phase, which is often prolonged for many months. It
becomes a pupa, nymph, or chrysalis, and undergoes
metamorphosis. In many butterflies and some small
moths, the larva fastens itself by its tail to a twig ; in many
other cases it suspends itself by a silken thread ; some hide
between two leaves fastened together by silk ; many
burrow beneath the ground ; most moths make some sort
of cocoon or shelter, which may be of pure silk neatly
wound, or of silk mixed with hair and all manner of
external things — such as pieces of leaf, bark, moss, and
lichen, and even grains of earth. These cocoons are
usually constructed in sheltered corners, and are often very

56 THE BIOLOGY OF THE SEASONS

inconspicuous. The finest pupa-cases are surely those
which are spun of silk (in most moths), and the making of
them in a few days is an extraordinary instance of the
intensity of chemical processes in the body, and also of
great muscular activity on the part of a creature that is
about to fall into sleep. The long thread of silk is a secre-
tion, that is to say, it is a not-living organic substance
manufactured at the expense of the living matter of the
cells composing the silk-glands. It is spun into a cocoon
by persistent movements of the head, which must imply
great exertion ; thus the larva of Polyphemus is said to
move its head a quarter of a million times in making its
cocoon.

Within the pupa cuticle a remarkable process occurs,
which has excited the wonder of many generations of
naturalists, and is still imperfectly understood. The body
of the larva is broken down and is built up again on a
new architectural plan. Clusters of active embryonic cells
become the foci of new formation, and wandering amoeboid
phagocytes, working like sappers and miners among the
tissues, transport material from place to place. Although
the breaking-down (or histolysis) which precedes the re-
construction (or histogenesis) is never so thoroughgoing
as in flies, where the pupa returns almost to an egg-like
state, there is a gradual transformation of almost all the
organs. One may compare what occurs to a not unfamiliar
sight, the piece-meal pulling down of a large building,
such as a railway station, and its pari passu reconstruction,
but all so regulated that the essential activity — and what
else is life! — does not come to a standstill.

When the reconstruction is completed — which may
take a couple of weeks or as many years — the fully formed
insect or imago emerges from the pupa-case — its last
moult. It is often rather soft and flabby on its emergence,

CATERPILLARS 57

but it soon hardens up and there is no more growing.
Many of the details of the liberation of the butterfly or
moth are extremely interesting, thus there are often lids
which open neatly ; there is sometimes a transitory head-
organ that helps the escape, just like the " egg-tooth "
with which young birds break through the egg-shell ; the
puss-moth secretes caustic potash from its mouth which
dissolves away the pupa-case.

The ranks of the caterpillars are thinned by the weather,
by many birds, and by other harassing enemies, such as
the Ichneumon flies which lay their eggs in the juicy
body. The risks that caterpillars run are so many that
their survival is sometimes surprising. In the main it is
secured in two ways — by sheer force of numbers on the
one hand, and by numerous protective adaptations on the
other. The importance of the latter, which are often very
subtle, will be better realised when we remember, what
Alfred Russel Wallace pointed out, that it is essential for
most caterpillars to escape even a tentative peck. The
soft-walled tense character of the body is " extremely
dangerous, for a slight wound entails great loss of blood,
while a moderate injury must prove fatal."

The protective adaptations are manifold. Hairy cater-
pillars are left alone by most birds, though the cuckoo seems
to relish them. Not a few secrete offensive fluids, such as
formic acid, when they are touched. Some have an un-
pleasant smell, and others are unpalatable, as experiment
has shown. Some hide during the day, others play 'possum
when touched. Some lash with their tail whips and strike
" terrifying attitudes/' But the subtler line of adaptation
is that seen in the numerous instances of protective re-
semblance. Thus some caterpillars are extraordinarily like
stunted twigs or little knobs on a stem ; others are like
little splinters of wood or the curled margins of withered

RHYTHMS IN PLANT LIFE

EVERY one recognises that, in a general way, Summer
is a season of great activity among plants, and
Winter a season of rest. This is one of the broad
expressions of the fact that all life is rhythmic. Professor
Pfeffer, one of the highest authorities on the physiology
of plants, has summed up the situation in one of
his terse paragraphs : l " All life is rhythmic in character,
each life-cycle being a repetition of a preceding one, and
during the progress of the grand period of each in-
dividual, various periodic movements occur in growing
and adult organs. Further, all metabolism consists of
rhythmically recurrent processes of anabolism and kata-
bolism. In addition to this autogenic rhythm, regularly
repeated external factors may induce a secondary or aitio-
genic rhythm, and the phenomena observed in nature are the
result of the co-operation of these two forms of rhythm."

Some of the clearest examples of periodicity are found in
the alternations of vegetative and reproductive periods, and
it has been shown in a variety of cases, especially among
Algae and Fungi, that reproduction is induced by appro-
priate changes in the external conditions. It can be hurried
on, or kept back, or suppressed for prolonged periods. The
beautiful experiments of Klebs on Algae, such as Vaucheria,
Spirogyra, and Hydrodictyon, show that the external con-
ditions punctuate the life-processes, determining whether

1 The Physiology of Plants, vol. ii. Trans, by Ewart, Oxford, 1903,
p. 197-

RHYTHMS IN PLANT LIFE 61

there shall be a period of vegetative growth, or asexual
reproduction, or sexual reproduction. As Pfeffer says :
" In Algae, the stimulation is usually due to such factors as
light, water, or temperature, and a regular alternation of
generations would be maintained by a constant periodicity
of the climatic factors." In the higher plants, as in the
higher animals, there seems to be a relatively greater freedom
from the direct grip of the environment, and the altered
conditions which bring about flowering, for instance, may be
of internal origin, that is to say, not in direct dependence on
the march of the seasons or any other external periodicity.
Keeping in mind this general idea of internal rhythm and
external punctuation, let us think of some of the fundamental
facts of plant life in spring.

GERMINATION

Increasing warmth, more light, softer winds, and
Spring showers — these are some of the familiar physical
conditions of the universal reawakening in Spring. Were
we wise enough we should be able to trace the whole chain of
causes — the long succession of stimuli — which connects the
increased share of the sun's energy with the germination of
seeds, the ascent of sap, the unpacking of buds, the return of
the migrants, the rise of song in the bird's throat, the awake-
ning of the sleepers, the emergence of the butterfly from
the chrysalis, the quickening of the pulse in man. " Our
very hearts have caught the charm that sheds a beauty
over earth."

Let us first think for a little of the germination of seeds.
Among plants, as among animals, one of the lines of evolu-
tion which is discernible is that which leads to prolonged
connection between the mother organism and its offspring.
In a seaweed, for instance, what leaves the parent organism

62 THE BIOLOGY OF THE SEASONS

isusuallya single cell, but it is an acorn — a formed young thing
— which falls from the oak tree. The salmon spawns on the
gravelly bed of the river, but to the mammalian mother a
child is born. There is progress not merely to viviparity,
but to bringing forth an offspring at a more and more ad-
vanced stage. The embryonic period tends to swallow up
the larval period. The advantage is plain, for, other things
being equal, the less weak and helpless an organism is when
it leaves its parent, the greater are its chances of surviving.
Robert Chambers, the author of the Vestiges of Creation,
made much of this sound and simple idea. There is pro-
digious infantile mortality among many of the lower animals
— especially among those which have no parental care either
conscious or unconscious. We need only recall that the
conger-eel is said to have about ten millions of eggs. Part of
the object of fish-hatcheries is to shelter the developing em-
bryos and larvae until they are able to do a little in the way of
fending for themselves. It has been suggested that one of
the reasons why the giant reptiles disappeared from off the
face of the earth was that their eggs were persistently
devoured by egg-eating birds and mammals.

The seeds which are so numerous in the ground — so
numerous that Darwin reared eighty seedlings from a single
clodlet on a bird's foot — represent an enormous store of
potential energy. They have a long history behind them.
" Formed in the warmth and brightness of last summer's sun,
ripened in the glow of Autumn, they fell to the ground, were
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 remained asleep; but not
dead — slow preparation was being made for the new day." 1

While a few seeds, such as those of poplars, must ger-
minate at once (i.e. in a few weeks) if they are to develop at
1 Study of Animal Life, p. 127.

RHYTHMS IN PLANT LIFE 63

all, this is not the way with the majority. For most there is
a period of quiescence — which for some may be experiment-
ally shown to be imperative. That it is not purely adaptive
to the inhospitable state of the earth and the cold weather, is
proved by the fact that some seeds will not germinate at once
even in propitious conditions, and that others wait over
several years. This may be interpreted partly as an alterna-
tion of rest after activity — just as the embryo hydra develops
for a while and then rests for six weeks ; partly as a conse-
quence of the firm protective husks and of the relatively
enormous quantity of capital or reserve products with which,
like a development-inhibiting legacy, so many seeds are
weighted ; and partly as adaptive to the seasons.

The analogy between dormant seeds and dormant eggs
is far-reaching, and may be followed into details. Thus it
seems to be a necessary condition for the development of
some animals, such as the Phyllopod Crustaceans Apus and
Branchipus, that the ova should be subjected for a period to
desiccation. In many cases one of the conditions of the
survival of the animal egg is the possession of a firm pro-
tective shell, which is obviously comparable to the husk of
the seed, just as the yolk is to the seed's albumin.

Noting as the main physical conditions — warmth and
moisture — we recognise as the chief facts in germination : —

(1) The insoaking of water, often through a specially
porous area, such as the brown mark or hilum at the base
of the bean ;

(2) The reawakening of the protoplasm (and we must
remember how peculiarly thirsty for water plant-proto-
plasm is) ;

(3) A fermenting process by which the hard stores in
the seed are rendered soluble and diffusible by a process
comparable to animal digestion ; and

(4) The interesting way in which Bacteria — the minions

64 THE BIOLOGY OF THE SEASONS

of Death — help to loosen the bonds of birth — rotting away
the hard husks.

The fermentation which goes on in seeds and seedlings,
making hard reserve material available for transport and
transformation, brings home to us the fundamental unity
of vital processes. There is a close resemblance between
digestive fermentations in animals, which make the solid
food diffusible, and the fermentations in plants. The list
of chemical substances known to be common to plants
and animals is enormous, and it includes a number of
digestive ferments.

Thus the diastase which Professor Vines and others have
proved to be present in every green leaf is comparable to
the ptyalin in our salivary secretion. Both change starch
into sugar. A diastatic ferment certainly occurs in many
seeds, bringing about the same change, and various ob-
servers have found a peptic ferment like that in our
stomachs, turning proteids into peptones. And Professor
J. Reynolds Green found a ferment like that of the animal
pancreas in the seeds of the Lupin.

There is, however, great discrepancy among chemical
physiologists in regard to these peptic ferments in seeds,
and we cannot enter into the very difficult questions
involved. Suffice it to say that there is often much stored
proteid in seeds — more than there is for a time in the
young plant. In some way this condensed reserve
material is made available. There is no doubt that seed-
lings have a peptic ferment which acts in the presence
of an organic acid, but its presence remains doubtful in
many seeds where some sort of digestion must go on.
Perhaps the protoplasm of the seed sometimes does its
own fermenting of reserve material, without the aid of
any specialised ferment.

The rapidity of growth that follows germination in a

RHYTHMS IN PLANT LIFE 65

good season is sometimes almost magical. Kropotkin
tells us that around Tobolsk the sown fields are harvest
fields in about two months ; and Brehm has given us a
graphic picture of the coming of the Siberian spring, which
shows a greater abruptness than in our latitude. In a
few days the desert is as the rose, the barren grounds of
the Tundra become a garden, the Steppes are covered
with lilies, and the silent hills shout for joy. All of which
would be impossible were it not that in seed and bud,
in rhizome and corm, there is an enormous storehouse of
treasure waiting as it were for a word, the " Open Sesame "
of sun and shower.

But the legacy of the young plants is soon exhausted,
and they begin to fend for themselves. At this transition
there is sometimes a slight hiatus, which may be compared
to weaning, or perhaps more accurately, to the loss of
weight that occurs in mammalian offspring for a few
days after birth. The well-known " swooning " or waning
growth of the young corn at a certain stage corresponds
to the exhaustion of the seed-store and to the beginning
of entirely independent nutrition. This leads us naturally
to think of another feature of plant-life in Spring — the

uprush of sap.

ASCENT OF SAP

No fact of plant life is more important than this ascent
of sap, but we are far from a complete understanding
of it. The facts are that water, bearing mineral salts in
solution, passes from the soil into the roots by physical
osmosis modified to some extent by the facts that the cells
of the root are living. The inward flow is greatest in
Spring and least in Winter; its rapidity and pressure
vary within wide limits.

The upward path is by the cells and vessels of the young
wood, as may be proved in a variety of ways. Thar it is
5

66 THE BIOLOGY OF THE SEASONS

not by the bark is proved by the fact that the leaves of
a tree from which a ring of bark has been removed are
still able to flourish. That the path is not by the central
wood is plainly shown by the fact that a tree whose heart
has rotted out may still bear fresh and vigorous leaves.
Thus we may at once assert that the upward path of the
sap is by the outer or younger wood.

As to the use of the ascending current, the answer is
complex. It forms the whole food-supply of the plant
except the gases absorbed by the leaves from the air.
The water enters into the formation of starch and proteids,
and the salts also help more or less directly. The water
also serves to maintain the vigour of the protoplasm, for
abundance of water is almost always a condition of activity
in plant cells. Finally, no small part of the water makes
good the loss which leaves are always suffering from
radiation.

The factors are (i) the difference of density between
root cells and soil water ; (2) the suction from the leaves
which obviates the dilution of the whole plant ; (3) the action
of capillary forces ; and (4) the special activity of certain
cells on the upward path.

UNPACKING OF BUDS

Comparable in many ways to the germination of seeds
is the unpacking of buds, which is equally characteristic
of the Spring. Like the seeds, the buds were made in the
abundance of a past summer ; they express the super-
abundance of vegetative life. Like the seeds, the buds
are adapted to contain much within small compass, and
are protected by scales which correspond to husks. Like
the seeds, the buds have a period of quiescence after the
period of formation, for many of them remain nine months
or so in a dormant state,

RHYTHMS IN PLANT LIFE 67

Of interest is the neat way in which the young leaves
are packed within the bud, being usually twisted in a
spiral, corresponding to the spiral which the leaves eventu-
ally exhibit when they are unfolded and outspread upon
the shoot or branch.

The prime conditions of the unpacking of buds are, of
course, to be found in the Spring sunshine and the Spring
rain. Under the influence of increasing warmth the
water from the soil ascends to the sleeping buds and recalls
the cells to activity. These swell, become active, and
multiply, and the pressure from within bursts the scales
outside, which in dying away have saved the tender life
within.

MULTIPLICATION

One of the fundamental and far-reaching facts about
the life of plants in Spring is much less familiar than the
germination of seeds, the rise of the sap, and the opening
of buds. It is the extraordinarily rapid multiplication
of minute water-plants — of unicellular Algae in particular.
The importance of this lies in the provision of an almost
exhaustless food-supply for water animals. The complex
organic substances which the plants build up, with the
sun's aid, from air, water, and salts in solution, become
part and parcel of one animal after another through long
series of reincarnations. As to the rapidity with which
a pond or a lake becomes peopled with minute plants,
when Spring sets in, we can form little conception, for a
single one may become a thousand in two or three days,
and a million by the end of a week. In a particular
case, Professor Zacharias notes that within ten days the
numbers may be increased sixfold, and that there may be
over 70,000 (72,950) in a single litre.

THE RETURN OF THE BIRDS

THE migration of birds is one of the most striking,
as it is one of the most beautiful, of seasonal
phenomena. Their regular coming and going, often com-
pared to the flow and ebb of tides, has excited the admira-
tion of the observant in all ages. " Yea," the Hebrew
prophet said, " the stork in the heaven knoweth her
appointed times ; and the turtle and the crane and the
swallow observe the time of their coming," and still we wait
expectant in the Spring for the return of the cuckoo and
the nightingale, or watch wonderingly in the Autumn the
departure of those birds " who change their season in the
night, and wail their way from cloud to cloud down the
long wind/'

Regarding the flow and ebb of the feathered tide our
ignorance is still immense, but that is no reason for leaving
the subject severely alone till its formulae can be stated.
Much has been discovered in regard to migration ; much is
in process of being discovered ; there is always fascination
in a subject which is developing. The Indians used to
name some of the months after the conspicuous migrants ;
and whether we understand the why and how of the move-
ments, they are certainly before us to be seen, enjoyed, and
puzzled over. We shall confine ourselves in this chapter
to a statement of the fundamental facts, leaving till later
any discussion of the problems or of the methods of investi-
gation.

(i) In the Northern Hemisphere, migration is a very

PUFFINS AT THEIR BREEDING-PLACE
(II)

» '

THE RETURN OF THE BIRDS 69

general phenomenon, but it varies greatly in its con
spicuousness — that is, as to the number of birds taking part
at one time, and as to the length of the flight . Gatke tells us
that from ten o'clock on the night of the 28th October 1882
to early next morning, golden-crested wrens eddied round the
lighthouse at Heligoland thick as flakes in a snowstorm, and
that they covered every square foot of the island. In the
same year, about the beginning of the second week of
October, flocks of the same beautiful birds were simul-
taneously observed at all the lighthouses, lightships, and
many land-stations from Guernsey in the south to Bressay
among the Shetlands in the north. That is to say,
the breadth of the marching column was something like
640 geographical miles. In other cases, the migration
occurs without our seeing any excited crowds ; yesterday
they were with us, and to-day they are gone.

In Britain most of the mass-movements of migrants
take place at night, so that we get little impression of the
enormous numbers, except when they call as they pass
overhead, or are drawn, especially on misty nights, within
the bewildering fascination of the lighthouse. The light-
house-keepers and ornithologists who have been allowed
for a time to bear them company, have sometimes great
experiences "—of birds in countless hosts, drifting by in
feathery tides ; birds passing for days together, literally
square miles of them ; birds by day and birds by night,
flying in regular steady waves or in bewildering rushes/'

" Who can recount what transmigrations there
Are annual made ? What nations come and go ?
And how the living clouds on clouds arise ?
Infinite wings ! till all the plume-dark air
And rude resounding shore, are one wild cry."

And as to the distance travelled, it may be from Scotland
to Ireland, as seems to be true of some peewits ; or from

70 THE BIOLOGY OF THE SEASONS

Eastern to Western Scotland, as with many starlings ; or
from hill to valley, or from moorland to shore. We have
been able to prove that a thrush may migrate from
Aberdeenshire to Lisbon, and a black-headed gull to Bor-
deaux, but these are only short journeys — probably parts
of a longer prospective journey in the cases mentioned.
It has been proved that storks from Germany may migrate
to Natal, and of some other birds it may be said with
confidence that they fly half across the earth. The Curlew
Sandpiper and the Knot breed so far north that their eggs
have rarely been found, and yet the birds have been seen
in New Zealand in winter ! " They must have performed
a southern flight equal to nearly half the circumference of
the globe."

Even more striking is the very interesting fact reported
by Dr. W. S. Bruce of the Scotia, that the Arctic Tern was
observed " wintering " in the Antarctic summer in 74° i'
S. lat. It is well known as a breeding bird on our own
coasts to 82° N. lat. We have here, so far as is known,
" the greatest latitudinal range of any vertebrate animal."

(2) In the Northern Hemisphere most birds migrate
between a colder area which love enlivens, where they
breed, and a warmer area where hunger is avoided, where
they winter. It is a cardinal fact, to which there are few
exceptions, that birds breed in the coldest part of their
migratory range.

In emphasising the fact that most birds in the Northern
Hemisphere are migratory, and that in a perfectly definite
way, we must, however, make it plain that the range of the
migration may be very limited, and that many kinds of
birds are only partial migrants, some individuals leaving
the country and others staying. In many cases the
migration is greater than it seems, because the place of
individuals that have slipped southwards in Autumn may

THE RETURN OF THE felRDS 71

be taken by other birds who come to Britain from the
Continent.

The broad fact that birds breed in the coldest part of
their range implies that the Spring immigrants into a North
Temperate country come, on the whole, from the south
or south-east, and that the Autumn emigrants fly, on the
whole, towards the south. This very general statement is
not inconsistent with more detailed statements, for instance,
that many immigrants come to Britain from the Continent
in Autumn and may swell the throng of our partial
migrants.

We have little secure knowledge of the precise winter-
quarters of those birds which spend their summer with us,
but the general fact of an autumnal movement from Arctic
and North Temperate Zones to lands nearer the Equator,
and of a reverse vernal movement, is certain. Of particular
interest are those cases, like that of the stork already
mentioned, where the birds " keep always on the summer
side of the Equator," where, in other words, they enjoy the
northern summer, and, fly ing across the Equator, find a second
summer in the Southern Hemisphere.

It must be clearly understood that migration is more
than a mass-movement, such as is familiar in the case of
Pallas' s Sand Grouse, which has repeatedly invaded Britain
from the East in considerable numbers. Migration is to be
distinguished from gradual extensions of the range of
distribution, from tentative explorations in search of food,
and from invasions of new territory under urgent stress of
over-population. True migration is a regularly recurrent
oscillation between a place of breeding and nesting and a
place of feeding and resting ; it is an adaptation to the
seasons and to the conditions of reproduction ; the impulse
which prompts it is now instinctive, but the trigger is
pulled by external stimuli.

72 THE BIOLOGY OF THE SEASONS

(3) In a North Temperate country like Britain, we may
divide the birds into five sets, which are not very rigidly
limited from one another.

First, there are the Summer visitors, such as swift and
swallow, cuckoo and nightingale, who arrive from the south
and south-east in the wake of Spring, with Spring in their
voices. They remain to breed, but leave our shores again in
the Autumn. We see some of them congregating excitedly,
taking trial flights, as it were saying good-bye many times
over ; they start on their journey ; they pass the coast
lighthouses in the night ; they traverse the pathless sea ;
they speed on, it may be along the west coast of Africa, or
across the blue waters of the Mediterranean ; they reach
winter-quarters somewhere — in the Nile Valley, in Madeira,
in South Africa — somewhere. There they abide until the
cold and dark days in the north are past ; thence they
return in Spring, some of them at least love-prompted, to
our budding hedgerows and reawakened woods.

Among the more familiar Summer visitors to Britain,
we may mention cuckoo, nightingale, swift, swallow,
martins, ring-ousel, willow- wren, whitethroat, and fly-
catchers. The name of the last suggests the obvious
remark that the majority of the Summer visitors are
insectivorous.

Second, there are the Winter visitors, such as fieldfare
and redwing, snow-bunting and some northern ducks.
They arrive in Autumn, chiefly from the north and north-
east ; they are with us during the cold, raw months ; they
fly northwards again in Spring, to sing their love-songs — if
they have any — in the inhospitable " barren grounds " of
the Tundra or amid the surge which surrounds the northern
skerries. Many of our Winter visitors in the wider sense
come as additions to the ranks of those species that are
represented in the country throughout the whole year.

THE RETURN OF THE BIRDS 73

Third, there are the Birds of Passage in the narrow
sense, such as some of the sandpipers, the great snipe, and
the little stint. They occur for a short time on our shores,
which are neither warm enough nor cold enough for their
constitutions, resting twice a year on their way farther
south or farther north. It must be clearly realised that
the classification we are using is entirely relative; a bird
of passage in one part of the country may be a Summer or
Winter visitor in another part. It is similarly necessary to
see clearly that the cuckoo is a Summer visitor for Britain,
but a Winter visitor for Mediterranean countries.

Fourth, it seems clearest to make another division for
those birds that are often called " partial migrants " —
that are never unrepresented in the country, for while
some go, others stay, and the places of those who go are
often taken by individuals from farther north. Thus we
may see thrushes, lapwings, goldfinches, larks (and many
more might be named) every month of the year in Britain,
but there is none the less a migration of some of these birds.

Fifth, a few birds seem to deserve to be called
" residents" — those, namely, that do not leave the country
at all, or only in relatively small numbers. The most
stationary of the residents is the Red Grouse, — the only
bird peculiar to Britain, — which never leaves our shores.
But even this bird has its small migration, passing from
a higher to a lower level on the hills and moor as the Winter
comes on. If would be pedantic, we think, not to class
blackbird and robin and house-sparrow among the residents.
As we have hinted, however, many birds that seem to be
residents are partial migrants ; they seem to be always
with us, but sometimes careful observation has shown that
the individuals are not the same.

Lastly, there are those irregular migrants who may be
called " casual vagrants "—American birds, for instance,

74 THE BIOLOGY OF THE SEASONS

that somehow make their way across the Atlantic. Thus
the Kildeer Plover, a distinctively North American bird,
was shot at Peterhead in 1868, and has been recorded since.
The occurrence of these " casuals " varies in interest ; in
some cases the occurrence is so rare that we may almost
call it a curiosity ; in other cases it is repeated year after
year, and may indicate an extension of range.

(4) Another general fact admitted by all is that the
migratory movements are marked by a high degree of
regularity. Whatever it is, migration is not a haphazard
business. The same kinds of birds return to the same part
of the country about the same time and leave about the
same time. The puffin is a good instance of punctuality
in arrival, the swift shows the same virtue in its departing.
There is some evidence to show that the same pair of birds
may return in successive Springs to the same nesting-place,
but the only way of making sure of this is to mark the birds.
This has been done in the case of house-martin and stork.
We can personally vouch for an interesting fact brought
out in the course of a Bird-Migration Inquiry now in
progress, that a swallow ringed in 1909 came back to the
same farm in 1910.

While some migration is always going on, the greater
movements are to be seen, as every one knows, in Spring and
Autumn. In Spring we look for the return of our singing-
birds ; in Autumn they say good-bye again. But the turn
of the tide northwards must be put as early as February,
when we hear the honk-honk of the wild geese as they make
for the north, and see their impressive flying phalanx ; and
the turn of the tide southwards must be put as early as mid
June when the adult cuckoos begin to get restless, and fly off,
leaving their young ones to the care of their duped foster-
parents. At present, however, we wish simply to em-
phasise the fundamental fact of orderliness of movement

THE RETURN OF THE BIRDS 75

both as regards space and time. We shall discuss some of
the many uncertainties and some of the difficult problems
of migration in subsequent studies. Meanwhile, let us
keep the broad facts clear, and realise the wonder of them.
" Any one," Gatke says, " who on dark, starless Autumn
nights has heard the babel of voices of these hundreds of
thousands and even millions of birds travelling past him
overhead, in one fixed direction and in undiminishing
numbers for the space of whole months, without the help of
any guiding mark discernible by human eye, cannot fail
to be led, by the supreme grandeur of this phenomenon, to
speculate as to what kind of capacities the unfailing per-
formance of such an act is due ; more especially, if like
myself he has for more than half a century watched the
phenomenon recurring regularly at each solstice with the
same unerring precision as the planets in their courses."

SOME QUESTIONS CONCERNING MIGRATION

WE have stated, in the preceding chapter, some of the
general facts regarding Bird-Migration. These
lead on to a series of extremely interesting questions which
must be answered very tentatively until more data are
collected and critically scrutinised. At the same time, they
are not so far from solution as some deeper problems which
we propose to discuss in a later chapter.

Since migration, as we have seen, implies an alternation
between a relatively colder breeding-place and a relatively
warmer wintering and resting-place, the general trend of
the journey ings must be from north to south, and back
again. But this picture is far too simple. The autumnal
north to south flight may end up with a great sweep to the
east, and in the north of Europe there is a very important
movement from east to west, sometimes with a final sweep
towards the south.

" On dark autumn nights," Gatke says, " the sky is often
completely obscured by vast multitudes of plovers, curlews,
godwits, oyster-catchers, greenshanks, sandpipers, and
many other less vociferous species, such as larks and
thrushes, whose voices, resonant from afar, proclaim
clearly through the stillness of the night from what direc-
tion in the sky they are arriving, while the notes of the
departing travellers, gradually growing fainter and fainter,
announce in a manner equally distinct in what direction
they are continuing their journey. The whole flight proceeds,

SOME QUESTIONS CONCERNING MIGRATION 77

without pause or change, in one incessant stream from east
to west."

Hosts of birds gather in Autumn from the plains of
Russia and Finland, and pass along the southern shores of
the Baltic to Holland or the like, where the direction is
turned southwards. Certain contingents seem to follow
the valleys of the Rhine and Rhone, thus finding their way
to the Mediterranean, and across that to North Africa.
Other contingents seem to follow a coast route, crossing,
it may be, by Heligoland to the South of England, and
thence across to France and Portugal, but finally landing,
like the others, in North Africa.

For some birds there is a considerable body of evidence
as to the routes followed. The common swallow, for
instance, seems on the whole to fly north and south. Large
numbers are seen in Autumn making their way down the
west coast of Africa, perhaps reaching the Cape ; those
from Eastern Europe are said to work their way southwards
by the Nile Valley. Corresponding species or varieties
in North America seem to fly to Brazil, and in North Asia
to Burmah.

In illustration of a north to south movement, Gatke
cites the case of the Red-Spotted Bluethroat. Those that
breed in Norway are supposed to winter in North-East
Africa ; those that breed in Kamchatka are supposed to
winter in South Asia. That those moving from Norway
southward do not veer to the west, is indicated by the
absence of the bird from France and Spain and its great
rarity in England.

Gatke was very strongly of opinion that the vernal
flight was more direct than the autumnal. Of the birds
that pass through Heligoland in Autumn, not more than
half, he said, return by that route in Spring. The others
cut across. Indeed, as Gatke put it, if the autumnal flight

78 THE BIOLOGY OF THE SEASONS

be represented by the perpendicular and base of a right-

w|v^-^
angled triangle + _^*^^ , the vernal flight may be

S ^ E

represented by the hypotenuse. When the autumnal
flight is altogether from north to south, the vernal flight
cannot be more direct ; but, as we have seen, there are many
birds which show in Autumn an east to west and then a
southerly movement. As facts accumulate, it will be
possible to test Gatke's interesting suggestion as to the
greater directness of the Spring flight, which, as yet, some-
what outstrips the evidence. If there is this marked
change of flight in Spring, it will increase the difficulty of
understanding the path-finding.

We are still very much in the dark in regard to the
termini of the autumnal southward flight, and it is a great
satisfaction to be able to point to definite facts secured by
ringing individual birds. Thus Dr. Thienemann has
proved up to the hilt that many North European storks
winter in North Africa and go as far south as Natal. That
a large proportion of our Summer visitors go to Africa is
probably true, but definite information is scanty. What
is known in most cases is simply that no birds of a particular
kind are left in Autumn in a northern country, and that
there is a practically simultaneous arrival of a large repre-
sentation of this particular kind of bird in a southern country.
But it is a big step from this general fact to the particular
statement that night- jars from the English Lake District
go to East Africa by the Great Lakes. Yet it is this kind
of statement which one desires to make.

A second question in regard to which we lack adequate
information is as to the altitude of the migratory flight.
There is much reason to fear that many of the statements
made in this connection are greatly exaggerated. Observers
with telescopes have seen birds crossing the moon's disc

SOME QUESTIONS CONCERNING MIGRATION 79

at a height of 5 miles, and have even identified them as
woodpeckers and so forth. Mr. F. Chapman saw no fewer
than 262 in five hours. Gatke was of opinion that many
migrating birds, such as curlews, in full flight keep at an
elevation of 10,000 ft. or more; while Eagle Clarke notes
that he saw enormous numbers of larks, starlings, and
thrushes flying very low across the North Sea. It is
probable, however, that these low-flying birds form a small
minority. Careful observers have recorded hearing the
voices of crowds of migrants passing overhead on dark
nights, and have argued from the distinctness of the notes
that the birds could not be very high. It seems unlikely
that birds habitually fly at a height of anything like
10,000 ft., for that would involve the serious disadvantages
of rarefied air and low temperature. On the other hand,
if low flying is common, we ought to see more migration
than we do. The fact is, we do not know much about
the altitude of migratory flight.

A third question which cannot be answered without
more data concerns the velocity of the migratory flight,
in regard to which startling statements are often made.
It seems reasonable to allow that migration represents a
climax of activity, when the organism is attuned to great
deeds, the easy-going bird flying swiftly, the low-flying bird
ascending to higher strata, the diurnal bird flying by
night, and so on; but the estimates which even experts
have made of a rate of 200 miles an hour require to be
substantiated.

Two or three methods have been tried, e.g., observing
the time birds took to pass from one visible point to another ;
observing the time a bird of known size took to become
invisible ; and arguing from the absence of records of a bird's
occurrence between two countries, A and B, that the bird
flies from the one to the other without stopping. Gatke

80 THE BIOLOGY OF THE SEASONS

observed that curlews, godwits, and plovers went 4 miles
in one minute — a prodigious rate if it could be kept
up. It is, however, obviously fallacious to infer from
the rate of a sprint how much could be covered in an
hour.

It is interesting to notice Gatke's reference to an old
story of Henry ii.'s falcon which escaped from Fontaine-
bleau and was captured twenty-four hours later at Malta.
Thirty-six miles an hour ! some have said in astonishment ;
but the knowing old ornithologist pointed out that the speed
must have been at least twice as great. The falcon rested
during the night, did a little hunting, had a meal and a
digestive rest, and did not hurry after all !

Yarrell mentions the fact that in a race from Ghent to
Rouen a carrier pigeon flew at the rate of 100 geographical
miles in an hour, but Gatke regarded this as a very mediocre
performance. By collating observations with John Cor-
deaux in England in regard to flocks of hooded crows
crossing from Heligoland to Britain, Gatke arrived at the
result (certainly open to suspicion) that these birds fly at
a rate of 108 geographical miles per hour, doing 320 miles
in about three hours. The possible — perhaps probable —
fallacy is obviously that the flocks whose times of starting
and of arrival were carefully noticed may not have been
the same flocks at all. But 108 miles per hour is nothing
like the pace of some other birds! The Northern Blue
Throat (Cyanecula suecica), a little bird like a robin, flies
in Spring from the Nile and Central Africa (10° to 27° N.
lat.) to Northern Europe, to Heligoland by the way. It
reaches Heligoland about dawn. Because the bird is very
rare in intermediate areas, having only a very isolated
occurrence, Gatke concluded that it flies continuously, and
there are several other facts suggestive, though not de-
monstrative, of this conclusion. At all events, Gatke's

SOME QUESTIONS CONCERNING MIGRATION 81

data led him to the remarkable result that the bird accom-
plishes a journey of 1600 miles or so in nine hours, that is,
at a rate of 180 geographical miles per hour. But if this
speed can be attained by the blue-throat, what may we
not believe of really swift birds, such as hobby, swallow,
and plover. The Virginian Plover (Charadrius pluvialis)
is believed (by those who are satisfied with the assump-
tions) to pass in one magnificent flight of fifteen hours
from Labrador to North Brazil, about 3200 geographical
miles. That would correspond to a velocity of 212
geographical miles per hour, and we shall draw the line
here.

Tegetmeier has given facts which show that a carrier
pigeon may keep up a rate of 55 miles an hour for several
successive hours, and by many observations on herons
crossing a narrow strait I convinced myself one holiday that
a mile a minute is not an exaggeration. It may be recalled
that large birds, such as pheasants, have been known to fly
right through plate-glass shop windows, which indicates a
high velocity.

While admitting that facts are few, we venture to adhere
to the idea that the migrational flight at its height may
well be something far above the ordinary performance.
For in migration the bird is often at high tension ; as we
have already noticed, low-fliers sometimes fly high, diurnal
birds may fly by night, easy-going birds may attain to great
speed. If we succeed in forcing a corncrake to winged flight
in this country, we see a somewhat lumbering performance,
which gives little hint of what the bird can do in migration.

CONTRAST OF SPRING AND AUTUMN FLIGHT

As we have seen, the Spring flight is in great part
northward, the Autumn flight in great part southward ;
6

82 tHE BIOLOGY OF THE SEASONS

and, speaking in the same rather vague manner, we may
say that the spring-tide is moved by " love " and the
autumnal - tide by "hunger." Although the subject
requires more exact study, we may admit that there
is some truth in what many observers have stated as to
a difference in the character of the movement at the two
seasons.

The Autumnal movement is relatively less intense ;
there is more dallying — at least, till they get fairly agoing.
In some cases, as Mr. Eagle Clarke points out, the reason
is obvious : " Food is still abundant in their favourite
resting haunts, and there is no particular hurry to move
southwards."

Of the Spring movement, Gatke says " unrest and
impelling haste are everywhere the prominent characters " ;
there is no division of the journey into stages, nor any
tendency to long spells of rest. "Das ewig weibliche zieht
sie heran."

As to the order of flight, likewise, one wishes that there
were more security. Gatke's conclusions in regard to the
396 birds studied in passage at Heligoland were, in the
main, three : that the Autumn migration is (with one ex-
ception) initiated by the young birds, which begin to move
about six or eight weeks after they leave the nest ; that
the parents of these young birds do not get restless till
a month or two months later ; and that among the adults
the handsomest old males are the last to set out on the
migratory journey. In Spring this order of succession is
reversed ; the gay old males are the first to arrive, and the
immature young birds come last. The exception referred
to above is, of course, the cuckoo, for the parents leave
long before the young ones, which they have foisted on to
the care of other birds.

In his World of Life — a remarkable achievement for a

SOME QUESTIONS CONCERNING MIGRATION 83

veteran of eighty-eight— Dr. Alfred Russel Wallace has
severely criticised the view that the young birds make the
autumnal journey alone. He admits Gatke's observation,
with which the Heligolanders used to be practically familiar,
that the young birds arrive first and alone, the adult birds
appearing a week or two later. But he rejects the inference
that the young birds start on their migration alone, and
before their parents. According to Wallace, what probably
happens is this : that the older birds and stronger young
ones, flying together, pass over Heligoland without stopping ;
that those young birds that sink down on Heligoland are
the weaker individuals, much fatigued ; and that those
adults that arrive later on the island do not represent by
any means the main contingent, but rather the crippled,
the unmated, the partially moulted, and so on. On this
view, he thinks, " all the facts are explained without having
recourse to the wildly improbable hypothesis of flocks
of immature birds migrating over land areas and sea
quite alone, and a week in advance of their parents or
guides."

This criticism is a useful one, and certainly the marvel
of migration is great enough without being gratuitously
enhanced. On the other hand, practised ornithologists
develop observational power to a very remarkable degree,
and there are numerous testimonies to the fact that great
crowds of young birds have been seen leaving British shores
before the adults have got on the move, and that great crowds
of young birds have been seen arriving on our shores from
the Continent in Autumn with, as far as could be detected,
no adults amongst them. It is, indeed, practically impossible
to be sure that there are no old experienced hands among
the youngsters, but of their apparent absence there is
considerable expert evidence. Moreover, it should be
pointed out that, even on Dr. Wallace's interpretation of

84 THE BIOLOGY OF THE SEASONS

the data, we have to face the fact that, whether the
young birds that alight on Heligoland started alone or
not, they have to leave the island again without adult
guidance.

In the presence of considerable information in regard
to a number of birds, we adhere to the view that in many
cases the young are the first to start on their southward
journey in Autumn and the last to arrive on their return
journey in Spring. Even among the adults there is
sometimes a curious separation of the sexes — possibly
because they fly at unequal rates.

That the old birds should delay longer than their
children is not in itself surprising, for many of them require
rest after the arduous labours of nest-making and feeding
the young. Moreover, many of them have to undergo
a moult before they start, and from this the young are
exempt.

Another matter, in regard to which generalisation is
rash because data are few, is the influence of weather on
migration. It seems likely that the weather conditions
that obtain when and where a mass-movement begins are
of more moment than those into which the birds pass in
the course of their flight. Puffins, for instance, arrive
on our coasts with extraordinary punctuality, no matter
what the weather is like. It is certain, however, that
unfavourable weather may involve enormous increase of
mortality, which is probably always very high, and may
even put a stop to the flight altogether. Very dense fog
and a head-on gale may make flight impossible. Mr.
Eagle Clarke has supplied definite facts as to the delay
of some migrations by stormy weather, but he admits the
general statement that birds in their movements seem to
be very indifferent to meteorological conditions. As to
the fact often referred to, that many birds are seen

SOME QUESTIONS CONCERNING MIGRATION 85

migrating southwards in Autumn with the north wind
behind them, it has been justly observed that this is
because the weather conditions that have prompted the
birds to start are also those which cause a north wind
to blow across Britain.

REAWAKENINGS

THE welcome one gives in Spring to the returning
swallow and cuckoo soon broadens. There are many
old friends, and there is a thrill in the first sight of
each of them. For this one has been in the Far South, this
other in disguise ; one has been in hiding, and another has
gone down in sleep to the very gates of death. As an in-
stance of those that are reawakened, we may take the
humble-bees, which reappear in April or May. Queens or
females, they are — sole survivors of last year's brood,
who have passed the Winter at rest in some sheltered hole
in a mossy bank.

They fly to the early flowering plants, such as the
willows, from whose fragrant catkins they get their first
meal. There is a dwarf willow on the golf-links, one of the
smallest of trees, not more than a couple of inches in height,
and it is there that we find the newly roused queens year
after year. After some recuperation they look out for a
suitable nesting-place, where they make a more or less bowl-
like cradle of wax, containing a small quantity of pollen
mixed up with nectar. In this mass several eggs are laid,
and then the cradle is closed. After a short rest the queen
goes on to make a second cradle or cell connected with the
first, and then a third, and so on, each with its batch of eggs
and a small store of food. The store is so scanty, however,
that the developing larvae soon exhaust it, and the queen has
to feed them through a hole made in the lid of the cradle.

After a month or so has elapsed the first brood emerges,

REAWAKENINGS 87

each member from within its silken cocoon. These are all
"workers," — that is to say, usually sterile females, — but they
are not structurally different from the queens, as the worker
hive-bees are. The first set of daughters begin to help the
queen-mother to collect provender, and soon there is a second
set. The queen ceases to forage and remains in the nest,
exclusively maternal. Some of her daughters may produce
eggs, which develop without being fertilised. In any case,
towards the end of Summer numerous drones or males are
produced and several fully developed females — the future
queens.

Thus there is a large family — consisting of one queen-
mother, many workers, a smaller number of drones, numerous
young queens, and, it may be, some grandchildren. A nest
of Bombus terrestris in August contained 35 young
queens, 20 drones, and 160 workers. The average number
of a colony of Bombus muscorum in Britain is said to be
about 120— namely, 25 females, 36 males, 59 workers. But
the family as such is shortlived, thus differing markedly
from the bee-hive. All the members die off in the Autumn,
except a few fertilised queens, which rest, as we have seen,
throughout the Winter.

The nest of the humble-bee, which country boys often
destroy for the sake of the honey, is at a far lower level of
architecture than that of the hive-bee or the wasp. The
cells are of different sizes, those of the queens being largest,
of the workers smallest. They are not regularly arranged in
tiers, but a second set is built on the ruins of the first. No
cell is used twice as a cradle, but an old cradle may be used
for storage. An understanding of the nest is not facilitated
by the fact that some of the cells are built, not by Bombus,
but by a friendly parasitic bee (Psithyms or Apathus) that
lives in the humble-bees' nests. Dr. David Sharp writes : *

1 Cambridge Natural History, vol. vi. p. $7.

88 THE BIOLOGY OF THE SEASONS

" A nest of Bombus, exhibiting the various pots projecting
from the remains of empty and partially destroyed cells,
presents, as may well be imagined, a very curious appearance.
Some of the old cells apparently are partly destroyed for
the sake of the material they are composed of. Others are
formed into honey-tubs, of a makeshift nature. It must be
recollected that, as a colony increases, stores of provisions
become absolutely necessary, otherwise in bad weather the
larvae could not be fed. In good weather, and when flowers
abound, these bees collect and store honey in abundance ;
in addition to placing it in the empty pupa-cells, they
also form for it special receptacles ; these are delicate
cells made entirely of wax filled with honey, and are always
left open for the benefit of the community. The existence
of these honey-tubs in bumble-bees' nests has become known
to our country urchins, whose love for honey and for the
sport of bee-baiting leads to wholesale destruction of the
nests. According to Hoffer, special tubs for the storing of
pollen are sometimes formed ; these are much taller than the
other cells. The Psithyrus that live in the nests with the
Bombus are generally somewhat larger than the latter,
and consequently their cells may be distinguished in the
nests by their larger size. A bumble-bee's nest, composed
of all these heterogeneous chambers rising out of the ruins
of former layers of cells, presents a scene of such apparent
disorder that many have declared that the bumble-bees do
not know how to build."

There are many points of fascinating interest in respect
to humble-bees. There is the extraordinary industry
throughout the summer — the collecting of pollen and nectar
from the flowers, the making of the cells in the nests, the
feeding and tending of the young. It is difficult to refrain
from quoting too much from Dr. Sharp's great contribution
to Entomology ; we venture to give one of his notes on

EARLY FLOWERS AND HUMBLE-BEE
(III)

REAWAKENINGS 89

industry : " Some work even at night. Fea has recorded
the capture of a species in Upper Burmah working by moon-
light, and the same industry may be observed in this country
if there be sufficient heat as well as light . Godart, about two
hundred years ago, stated that a trumpeter-bee is kept in some
nests to rouse the denizens to work in the morning : this has
been treated as a fable by subsequent writers, but is con-
firmed in a circumstantial manner by Hoffer, who observed
the performance in a nest of Bombus ruderatus in his labora-
tory. On the trumpeter being taken away, its office was, the
following morning, filled by another individual. The trum-
peting was done as early as three or four o'clock in the
morning, and it is by no means impossible that the earliness
of the hour may have had something to do with the fact that
for two hundred years no one confirmed the old naturalist's
observation."

The inter-relations of humble-bees with other living
creatures are manifold. Darwin has shown how they form
a link in the chain that binds cats and clover-crop, and they
are similarly bound up with the pollination of many other
flowers. They have numerous enemies — the field-mice that
burglar their nests, many insects that destroy the larvae, and
at least one bird, Merops apiaster, the bee-eater. Numerous
mites are often seen on their bodies.

Perhaps the most extraordinary feature in the economy
of Bombus is their tolerance for their Dopp el-Ganger,
Psithyrus, which are inmates of their nests. Host and guest
are like one another : " They were not distinguished by the
earlier entomologists ; and what is still more remarkable,
each species of Psithyrus resembles the Bombus, with which
it usually lives. There appear, however, to be occasional
exceptions to this rule, Smith having seen one of the yellow-
banded Psithyrus in the nest of a red-tailed Bombus.
Psithyrus is chiefly distinguished from Bombus by the

90 THE BIOLOGY OF THE SEASONS

absence of certain characters that fit the latter insects for
their industrial life ; the hind tibiae [fourth joints of the leg]
have no smooth space for the conveyance of pollen, and, so
far as is known, there are only two sexes — males and perfect
females. The Bombus and Psithyrus live together on the
best terms, and it appears probable that the latter do the
former no harm beyond appropriating a portion of their food
supplies. Schmiedeknecht says they are commensals, not
parasites ; but it must be admitted that singularly few
descriptions of the habits and life-histories of these interest-
ing insects have been recorded " (Sharp, loc. cit. p. 59).

When there are too many guests, the family remains
small, but the relations of host and guest remain quite
friendly. The arrival of a new guest creates apparent
excitement, but there seems to be some fascination about the
big, lazy intruder. A well-established friend of the family
is said to resent the appearance of a newcomer. Altogether,
the association is a strange riddle.

Humble-bees are very familiar animals, but there is still
much to be learned in regard to their ways — what deter-
mines the production of workers, drones, or queens, what
time is required for the development of each, what deter-
mines the occasional parthenogenesis of workers, and so on.
These and other points, such as the great variability in the
colour of the abundant hair, require further investigation,
which is sure to be richly rewarded.

It is impossible to pass from the humble-bee without
noticing the interesting position it occupies in the evolu-
tionary series of bees. Let us run up the scale.

First, there are solitary bees like the leaf-cutter,
Megachile, who bores a tunnel in wood, lines the end of it
with neatly cut pieces of rose-leaf, deposits pollen, nectar,
and eggs, shuts the door, and flies away.

Second, there is a stage represented by a rare bee,

REAWAKENINGS 91

Ceratina, who behaves as the leaf-cutter does, but waits
about till her young ones are hatched, and then flies away
with them.

Third, there are mining bees, like Andrena, that make
many tunnels in one place, with a distinct tendency to be
gregarious, though each digs a distinct hole for itself.

Fourth, there is the stage represented by Halictus, where
several combine to make a burrow or street in the sandy
bank, and then dig their respective tunnels opening
separately into it.

Fifth, there is the temporary community represented by
Bombus, where only the queens survive the Winter. But it
is very interesting to notice, especially in connection with
seasonal punctuation, that just as there are some northern
humble-bees that have no workers and no community, so
there are some southern humble-bees, as in Corsica, which
survive as a big family or incipient community through the
Winter.

Sixth, the climax of the series is reached in the
permanent society of the hive-bee, where workers as well as
queens live through the Winter.

SPRING FLOWERS

EVERY observer will admit that there is a certain
regularity in the succession of flowers in the course
of the year. Most of them have their times of ap-
pearing, just as the birds have. To find a foxglove or a
viper's bugloss blossoming in early Spring, or wood-
anemones and wild hyacinths in late Summer, would surprise
us as much as to see a full-grown cuckoo in Autumn. It is
interesting to try to analyse the order of this seasonal
procession or pageant, though we may not be able to do
so with much success.

Perhaps we may arrange the early Spring flowers in
four groups. There are not a few, such as willow, hazel,
alder, dog's mercury, and so on, that have very little in
the way of decorative parts. In many cases they are
practically reduced to the essentials — stamens and carpels.
There are relatively few flower- visit ing insects at this time
of year, and a large proportion of the earliest flowers are
pollinated by the wind. In a second group we may rank
those, like the Hellebores, that have their petals and sepals
(or perianth parts) of a greenish colour — that is to say,
not very far removed from the normal green-leaf type.
Thirdly, there is a noteworthy group of early Spring
flowers that are white. The wood-anemones, which rise in
the wood from amid the withered leaves and toss in the wind
like foam-balls, illustrate this type, and snowdrops, wood-
sorrel, and sloe-blossom immediately rise in the mind.

There is such a thing as white flower-pigment (antholeucin),

92

SPRING FLOWERS 93

but in most cases the petals or sepals are white, just as
foam is white, because of innumerable gas-bubbles in the
cells. They may be literally spoken of as living foam.
Fourthly, there are brightly coloured Spring flowers, like
the tulips and irises, that make even the steppe country
resplendent, or the marsh marigolds in our ditches and
the wild hyacinths in our woods.

One of the most obvious general facts is that all the
Conifers in North Temperate countries flower very early in
the year — in March, April, and May. This is interesting
when we remember, what every one knows, that they
represent a much older stock than the ordinary flowering
plants. It is proved by their structure, and also by their
history in the rocks, that " Gymnosperms " are much more
ancient than " Angiosperms." Why should they all
flower early ?

It is probable that numerous factors contribute to
this result. First of all, they are trees, with a large store
of potential energy and in a very different position from
annuals, for instance. Secondly, many are thick-skinned
evergreens, and therefore hardy, without the usual thorough
Winter's break in the assimilation processes. Thirdly,
they come of an old hardy stock, much tried for many
ages during the evolution of our present-day climate.
Fourthly, they are anemophilous — that is to say, pollinated
by the wind, and requiring no insects to visit them ; they
are, therefore, not prejudiced by flowering at a time of
year when insects are scarce.

A general fact to be borne in mind when thinking of
our early Spring flowers is that most of them blossom
so soon in virtue of stores previously acquired. It is
plain that trees have, on the whole, the start of herbs
because of their perennial stems and branches, which mean
not only a great store of potential energy, but also the

94 THE BIOLOGY OF THE SEASONS

possibility of having ready-made buds in position foi
unfolding. In some cases, such as the alder, even the
flower-buds are made the previous Summer. It is inter-
esting also to notice, what Grant Allen points out, that
many of our early flowering trees, like lilac, hawthorn,
and laburnum, are plants which have a long life before
they flower. They have a prolonged nutritive or vegetative
period before reproduction begins, and this is doubtless
one of the conditions of their hardiness. Another, even
more frequent, adaptation to early flowering is the posses-
sion of an underground store in the form of rhizome, corm,
or bulb, as may be illustrated by dog's mercury, primrose,
coltsfoot, celandine, hyacinth, and snowdrop.

While those Spring flowers that have only stamens
and pistil may be regarded as persisting on primitive lines,
there are others which may be regarded as persisting on
juvenile lines. We mean that they tend to be bud-like —
as if some slight arrestment occurred in the opening of
the blossom. This may be illustrated by crocus and globe-
flower.

Another general impression that we get when we take
a wide survey is that the colours of the early flowers are
lighter than those of summer, and that colours deepen
as the sunshine increases. Of course, there are many
exceptions ; but many of these, such as tulips, hyacinths,
daffodils, crocuses, irises, are bulbous plants, which places
them in a very different position from ordinary annuals
and biennials. The whole subject of pigments, alike in
plants and animals, is exceedingly difficult, and one must
beware of hasty generalisation. The same colours may
depend upon different pigments ; the same pigment may
have different colours ; a very slight change in the alka-
linity or the acidity of the cell sap may produce a great
difference in the colour of a pigment. And while progress

SPRING FLOWERS 95

has been made by a number of valuable studies, notably
Dr. Marion Newbigin's Colour in Nature, our knowledge
of the composition, origin, and primary import of pigments
is still scanty. With this caution in mind, we adhere to
the thesis that the heightening of colour is associated with
the increased intensity of sunshine, though this does not
necessarily mean that the correlation is one of direct cause
and effect. It is plain, for instance, that most of the
flowers are adapted for insect-pollination, not wind-pollina-
tion, and it may be argued that the flower-visiting insects
— which increase in number as the Summer sets in — have
throughout long ages consistently selected the variants in
the direction of brighter coloration. But we must return
to this subject.

In a very interesting essay on " The Philosophy of
Flower Seasons " (American Naturalist, 1893, pp. 769-781),
Mr. Henry L. Clarke has maintained the thesis that the
more primitive flowers tend on the whole to appear earlier.
Let us illustrate his line of argument.

Though there are among Monocotyledons some very
highly specialised forms, such as orchids in one direction
and grasses in another, it is generally admitted that Mono-
cotyledons represent a lower grade of evolution and an
older stock than most of the Dicotyledons.

Now, what place do the Monocotyledons take in the
year's procession ? Think of snowdrops, daffodils, irises,
wood hyacinths, and so on. The general statement is
surely that, apart from specialised forms, the great majority
of Monocotyledons flower in Spring or early Summer.
The specialised grasses, on the other hand, culminate in
Summer, and some continue on into Autumn. The less
specialised sedges are distinctly earlier, thus the genus
Carex culminates in May, though the type-genus Cyperus
belongs to August and September. Similarly, Liliaceae

96 THE BIOLOGY OF THE SEASONS

predominate in Spring, though, again, the type-genus Lilium
culminates in Summer. The highly specialised Orchidaceae
are distinctly Summer flowers.

Likewise, among the Dicotyledons, it will be allowed that
the hypogynous forms with superior ovaries are more primi-
tive than the epigynous forms with inferior ovaries, and the
dialypetalous condition more primitive than the gamopetal-
ous condition. Here, again, the more primitive come first.

Earliest of the hypogynous flowers are the Ranun-
culaceae : celandine and buttercup, hepatica and anemone,
marsh marigold, and so on, appear early — all " wearing
the trembling pearls of Spring." But the more specialised
forms, such as columbine, larkspur, and monkshood, are
later, and some clematis belong to Summer. But most
of the typical Hypogynae are Spring flowers. The Rosaceae,
perigynous forms, are later in starting than the more
primitive Ranunculaceae, and reach perfection in late May
and through June.

" Turn," says Mr. Clarke, " to the Epigynae : Capri-
foliaceae (honeysuckle) and Rubiaceae (bedstraws), though
scattered, predominate in Summer ; Campanulaceae, par-
ticularly in late Summer and in Autumn, the finest type,
Campanula americana, coming in September. Late in
Summer and in September the Lobeliaceae are in fullest
perfection, the splendid Lobelia cardinalis and L. syphi-
litica being late. And lastly, we meet the vast order
Compositae, undoubtedly nearly the highest of flowering
plants. So numerous a group would naturally spread
throughout the seasons ; but, mark, it comes in all its glory
late in August and straightway through the Autumn, when
we have, among many, those gorgeous genera, Solidago
(Golden rod) and Aster. Here the fact confronts us that
in the Autumn the higher Sympetalae hold sweeping pre-
dominance over the lower Choripetalae."

SPRING FLOWERS 97

The same general induction may be reached by singling
out highly specialised forms belonging to certain orders,
and noting that they appear usually later than their more
average relatives. The pondweeds (Potamogetori) , peculi-
arly specialised among Naiadaceae, come late ; Smilax, a
Midsummer flower, is markedly more specialised than
the Spring-flowering Liliaceae ; Columbine comes after
Celandine ; of aquatic Nymphaeaceae (near relatives of
Ranunculaceae), the most specialised Nelumbo is latest
to flower ; Grass of Parnassus, an aberrant relative of the
Saxifrages, belongs to late Autumn, and the Sundew also
flowers in late Summer ; the aquatic Bladderworts are
wholly Summer flowers ; and so on through a long list.

Yet another mode of approach is to take a single genus,
and follow its species. Mr. Clarke takes the Slipperwort
(Cypripedium). " Earliest, in late May, comes the little
white C. candidum ; a little later the low, stemless type
with its large complicated flower, C. acaule\ still later
the small flowered but tall-growing C. parviflorum ; later
yet, the large cousin of the last, C. pubescens ; and latest,
late in June, most robust, vigorous, and conspicuous, the
splendid C. spectabile."

Let us hear the conclusion of this interesting inquiry
into the succession of flowers in their seasons. " From
early Spring to late Autumn there is a progression in the
general character of the flower-groups, from the lower to
the higher — successive groups succeeding each other in
time, parallel groups coming synchronously. The later
in order may be types of a higher character of develop-
ment, or they may be specialisations of a group whose
normal forms belonged to an earlier season. In short, in
their blooming season, the more perfect succeed the more
simple; the aberrant, the normal; the specialised, the
generalised."
7

98 THE BIOLOGY OF THE SEASONS

While Mr. Clarke's thesis seems to have a considerable
body of evidence to support it, we cannot regard it as
more than a partial interpretation. The problem is a
complex one, and, as Mr. Clarke recognises, the time when
a flower blooms is a function of many determinants, both
fixed and variable. It may be of interest to tabulate these.

(1) Much depends upon the plant's peculiarities of
constitution ; thus those that have stores of reserve
material, which means energy, in corm and bulb, tuber
and rhizome, stem and evergreen leaves, will be able to
flower earlier than those that have no reserves.

(2) Of importance also is the nature of the plant's
habitat and its availability at different seasons. " The
Spring flowers seek largely the protection of the wood-
lands ; marsh plants reach perfection mainly in latest
Spring and through the Summer, though some, like Caltha,
are early ; the aquatics of ponds and river glory in the
Summer sun ; and the flowers of meadow and prairie and
thicket margin luxuriate from Midsummer to the end of
Autumn."

(3) Another factor is the mode of pollination ; by wind
or by insects, and by some kinds of insects rather than
others. It is plain that we cannot look for a large pro-
portion of insect-pollinated flowers in very early Spring.
It is true that insects may, in the course of time, adapt their
life-history to suit the flowers on which they depend, but
it is obvious that a bee-pollinated flower is not likely to
survive if it takes to blossoming only at a time when there
are no bees about.

(4) Something must also be allowed for the geographical
origin of any particular plant. A wanderer from a colder
country will naturally flower early in its new home.

(5) After allowing for these (and probably other)
factors, we return to the thesis that the time of flowering

SPRING FLOWERS 99

depends to some extent on the plant's position in the
evolutionary series. The simpler, the more normal, the
more generalised, in short, the older, tend to flower first.

" The most simple and generalised forms, coming first
in the course of floral evolution, have had longest time
in which to adapt themselves to existing climatic con-
ditions ; and, reciprocally, climatic conditions have become
more and more favourable to the rapid development of
the said forms. So a floral type that ages ago would have
reached its perfection only after a long continuance of
favouring seasons, now may burst into the fulness of its
maturity with the first warmth of Spring.

" But as change succeeded change, in the course of time
a maximum point would be reached, from which the con-
ditions would become less and less favourable to the rapid
development of types surviving from an earlier age. Then
these would dwindle from the earth — replaced, driven out,
by those that had come into existence in a later age.

" Thus, in the ages to come, the early flowers of to-day
will disappear, to be replaced by what are now our later
flowers ; whose place, in turn, will be filled by forms that
are yet to be."

Let us therefore be glad in the Spring flowers which,
like ourselves, are children of a day.

Let us, as Solomon said, crown ourselves with rose-buds
before they be withered.

BOOK II.— SUMMER

BOOK II.— SUMMER

IMPRESSIONIST SKETCH

THE tide which begins to rise in Spring reaches high-
water mark in Midsummer, when it often makes for
itself a new shore. The buds are replaced by leafy boughs,
activity during the day is intense ; the bud-like early flowers
are succeeded by others of more liberal beauty ; young
things pass through adolescence to mature strength ; and
Love is justified in her children. For Summer is the time of
maximum output and income of energy, when the fires of
life not only burn brightest, but are built up for another
season ; it is the time of intensest effort, rising even to
madness, the time of richest beauty and fullest joy.

Although we are wont to associate Summer with rest and
holiday-making, this is an urban, not a rustic, generalisa-
tion. Midwinter is the countryman's resting-time ; in
Midsummer he is hard at work. So with Nature, for in
Summer most work is done, and great stores of energy are
accumulated for another year.

Whether we think of the green leaves in which the powers
of light and life co-operate to raise simple substances into
complexity, the inorganic into the organic ; or of the bees
who so industriously visit the flowers and store up honey in
the hive ; or of the birds gathering food for their callow
young ; or of the haymakers busy in the heat of the day, we

get the same impression of vigorous work, at the various

103

104 THE BIOLOGY OF THE SEASONS

planes of unconscious, instinctive, intelligent, and rational
life.

The biggest fact in the Biology of Summer is perhaps the
most obvious one, that it is then that life comes nearest, or,
what comes to the same thing, is most exposed to the source
of all mundane energy — the sun. Thus the Biology of
Summer has for its central problem the influence of heat
and light upon life. Now there is heat that burns, as we
see in the Steppe vegetation after the dry season ; and there
is light that kills, notably in the case of the disease germs
or Bacteria which a forenoon of clear sunshine destroys
so beneficently ; but the general fact, demonstrable by
numberless experiments, is that the heat and light of
Summer renew the energies of living creatures. Indeed, we
all depend from year to year on the power that green plants
have of inducing the sunlight to help them to make food
for us.

At the very opposite end of the scale — for there is a long
gamut of life from wheat plant to man — is it not true that
seeking the sun and seeking more life are synonymous for
some of us ? It is well known that the pulse-register or
sphygmograph proves that the sunshine vivifies the system.
Quite irrespective of warmth and comfort, quite apart from
the delights of the holiday mood, of being free, of hearing
the birds sing, and seeing the flowers in bloom, the sunlight
quickens the pulse and man's life.

" O solemn-beating heart
Of nature ! I have known that thou art
Bound unto man's by cords he cannot sever.
And what time they are slackened by him ever,
So to attest his own supernal part,
Still runneth thy vibration, fast and strong,
The slackened cord along ! "

And if in man — so often with a slackened cord — the sun-
light still awakens response, how much more in the animals

IMPRESSIONIST SKETCH 105

who throb with every pulsation of Nature's heart. And if
the sunlight finds voice in the bravura of birds, how much
more directly in the bustle of growing wheat !

The growing intensity of unconscious vegetative life is
registered in the increasing brightness of floral colour. For
although there are many bright flowers in early Spring —
the marsh marigold, which raises its golden cups from the
dank ditch ; the bright yellow celandine, which welcomes the
swallow ; the blue hyacinths, which make the wood-glade
glorious — " the heavens upbreaking through the earth " ; the
laburnum, with its " dropping wells of fire "; the periwinkle
and the ground-ivy, and the golden daffodils, whose dance
"outdoes the sparkling waves in glee" — yet the broad
fact is that as the days grow warmer and brighter, the
colours increase in intensity. Although we may not be
able to accept the meteorologist's suggestion — too simple to
be true — that the annual succession of colour corresponds
to the colour scheme of the rainbow, yet it seems demon-
strable that red and purple, blue and violet flowers, in
short, those of richer colour, become on the whole more
numerous as the days lengthen.

Ruskin, following Goethe, defined the real nature of the
flower when he said, " The leaf which loves the light has,
above all things, the purpose of being married to another leaf,
and having child-leaves, and children's children of leaves, to
make the earth fair for ever. And when the leaves marry
they put on wedding-robes, and are more glorious than
Solomon in all his glory, and they have feasts of honey, and
we call them flowers." For it is admitted by all that the
petals are transfigured leaves, and that the pollen-producing
and seed-producing parts of the flower are also modified
leaves. The feasts of honey or nectar are overflowing wells
of sugar in more or less useful places ; the fragrance which is
so often given off from these creatures that toil not may be

106 THE BIOLOGY OF THE SEASONS

remotely analogous to the musk-like and other odours which
exude from the skins of animals ; and the fine colour of the
wedding-robes, just like the yellow in some butterflies' wings,
is in some cases due to waste products, the ashes of the
flowers' hidden fires.

It cannot be said that we have by any means attained to
an understanding of either nectar or fragrance or colour ; we
are still children with flowers in our hands, just beginning to
know something about them. But we have got past the
preliminary stage of giving their insect visitors the whole
credit of evolving flowers, which is a little too like crowning
snakes for evolving the wisdom of the East ; we are now busy
trying to find out what nectar, fragrance, and pigments mean
primarily or physiologically in the internal economy of the
plant. The poet says of the flower : " It must be the flag
of my disposition, out of hopeful green stuff woven " ; the
religious mind says : " It is the handkerchief of the Lord, a
scented gift and remembrancer designedly dropt, bearing
the owner's name someway in the corners " ; the biologist
says : " Overflow of surplus sugar, sublimated vegetable
sweat, and literal beauty for ashes " ; — but the flower in the
crannied wall is a hieroglyph still.

Summer, we say, is the time of maximum industry, and
greatest of all is the unconscious work of the sunlit leaves
The results of this are seen in the filling of tubers and
rhizomes, corms and bulbs, and other storehouses ; in the
formation of next year's buds ; in the making of seeds and
the swelling of fruits ; — and again, indirectly, in the increased
store of potential energy which is thus brought by plants
within reach of animal life. The sunbeams dance over the
meadow, but some of them are trapped, and their dance is
lost in a dance of molecules which change partners in the
maze, link themselves in mobile groups, and reach their
climax of linkage in complex combinations, some more

IMPRESSIONIST SKETCH 107

stable, some more unstable. Many a meadow is almost
iridescent, we can hardly see the grass for flowers, each is in
a sense a fixed sunbeam ; the butterflies flit from blossom to
blossom, the sunbeam is in motion again. It is a ceaseless
series of transformations of energy.

That Summer is the time of intensest industry is plain
enough even among the plants, but this dominant impression
of what Summer means biologically is emphasised when we
watch its busy animal life. This is swayed in great part by
the twin impulses of Hunger and Love. There is eager
endeavour after individual well-being, and there is a not less
careful effort which secures the welfare of the young. The
former varies from a life and death struggle at the very
margin of subsistence to a gay competition in the pursuit of
aesthetic luxuries ; and the latter rises from physiologically
necessary life-losing and purely instinctive sacrifice to what
seems to us affectionate devotion. Whether we look out on
plants or animals or men during these Summer months of
intense life, the old question rises to our lips, " Warum treibt
sich das Volk so und schreit ? " and the answer, funda-
mentally true, but changeable within limits for different
existences, is ever, " Es will sich ernahren, Kinder zeugen,
und die nahren so gut es vermag."

The activity of ants, bees, wasps, and other insects,
represents Summer industry at a higher level than that in
the leaves. It is behaviour, instinctive behaviour. By
behaviour we mean that the creatures follow out a routine
whose individual acts are arranged in effective sequence.
By instinctive we mean that the behaviour does not seem
to require intelligent control, it is more or less independent
of education and experience — though it may be improved
by both. Most of those activities, which it is one of the
delights of Summer to watch, are performed in virtue
of inherited cerebral initiatives, if such an ignorance-

THE BIOLOGY OF THE SEASONS

confessing phrase be admissible. The animals are, so to
speak, constitutionally wound up to do what they do when
suitable stimuli occur. In many of their activities they
seem to be conscious automata, if we may infer consciousness
from the way in which intelligence often takes the reins
when something unusual disturbs the routine. But the
beauty of it is that the results of the conscious automatism
are often as perfect as the outcome of prolonged and
profound deliberation. As we look at the bee's honeycomb,
the wasp's nest, the spider's web, it seems as if art, in
the broad sense of skill, is perfected in becoming most
instinctive ; and surely the rationality of our world is as
plain in the web or the termitary, as it is in the Forth
Bridge or the Eiffel Tower.

Animal industry in its instinctive form gives one an
impression of ease and spontaneity ; they do not sweat
or whine, or hesitate or look worried. They remind
us of very perfect mechanisms which perform their task
without noise or jar, with a fine " smoothness." But
just as the machine has certainly its wear and tear, however
well concealed that may be, so is it with the instinctively
industrious animals. Recent researches prove that the
nerve-cells of a bee's brain are, at the end of a hard
day's work, unmistakably fatigued ; and, more than this,
a certain number seem quickly to go out of gear as the
Summer's work continues ; they die off until no more
are left than are sufficient for the necessary vital functions ;
and finally these also give way. There are hints of the
same sad fact even in man ; and although our knowledge of
the matter is very slight, we may dimly see why it is that
we are doomed, not only to become " old fogies," but to die
of " old foginess " should we escape a more merciful ending.
Along the same line of thought we may perhaps advance
to a better understanding of the saving reactions of daily

IMPRESSIONIST SKETCH 109

and seasonal sleep, by which fatigued nerve-cells are
recuperated before they have gone too far.

Representing a higher grade of activity than that of
the bees, is the parental industry of the birds, for it is
to a larger degree intelligent. We do not refer to the
building of nests, which we regard as an activity of Spring
(often continued into Summer), and as instinctive in greater
part ; we are thinking rather of the untiring activity
which so many exhibit in protecting, feeding, and finally
educating their young. The songsters are quieter than
they were, the wild lyrics have given place to more measured
psalms of life, partly, of course, because the ecstasy of
passion is over for the season, partly, perhaps, because the
birds have found keeping house a much more serious
business than falling in love and getting married. It is
such a familiar fact, that we are apt to miss the beauty
of it — the manner in which the love of mates broadens
into the love of offspring. Every one knows that the
two parent birds will work themselves thin in caring for
their young. We are not warranted in supposing that the
birds think of their sacrifice, any more than of the welfare
of the species, — they do not control their conduct in
reference to an ideal ; they are not moral, poor things, —
but is there not something wonderful in it, something,
as Socrates said, moving to tears, and yet consoling in our
relations one with another ?

But it must be noticed that the intensity of life, which
seems to us so characteristic of Summer, is by no means
unrelieved. Every one familiar with the country has
noticed that in days of intense heat the whole aspect of
Nature occasionally suggests sleepiness, especially about
noon. A few clouds hang motionless in a lofty blue sky,
the air is tremulous over the hot earth, the birds are all
hushed in the woods, the leaves droop after extreme

no THE BIOLOGY OF THE SEASONS

transpiration, the labourers have lain down in the shade
of the hedge, and there is scarcely a sound save for the
grasshoppers, whose interrupted chirping makes us feel the
vast background of silence. Doubtless our own sleepiness
exaggerates the impression ; but when even the leaves sink
into " sleep," saving themselves from too great loss of
water, few living things are likely to be wakeful. In
fact, what we experience even in this country is a sugges-
tion of the Summer slumbers or aestivation — of mud-fishes,
amphibians, and crocodiles, when the waters dry up in
the pools of tropical countries. It is interesting to corro-
borate this impression by visiting certain kinds of shore
pools in the heat of the day when there is a stillness like
that of an Eastern city in siesta, and in the morning or after-
noon when there is all the activity of a Donnybrook Fair.

There is another phenomenon that has often impressed
us on a bright and breezy Summer day — the sudden
appearance of a dark cloud, which, though heavy with
dust and rain, drifts rapidly across the sky. We can
follow its shadow as it sweeps over the fields and the firth ;
and as it blots out the sun from us for a few long seconds,
we feel a shiver of suspense. Of course this is mere
sentimentalism, but the precise physiology of the shiver
might be interesting, for instance in its illustration of the
connection between emotion and muscular movements.
At all events we take this cloud, no bigger than a man's
hand, as a symbol ; it is the external counterpart of the
tear which comes sometime to all of us to blot out God's
sun. Its shadow is Death's.

For in the midst of all the wealth and virility of life,
all the bustle and gaiety of Summer days, he with the
ever-harvesting sickle walks with swift feet. He mingles
with the haymakers, and one is carried senseless off the
field ; he troubles the waters of the seaside town, and the

IMPRESSIONIST SKETCH in

ranks of the children who romped merrily on the sands
are thinned ; he passes among the flocks, and many need
no more shepherding ; he breathes among the dancing
day-flies, and they sink with the setting sun. And why
in the midst of life is there so much death, against which
there is no standing or defiance even among the strongest ?
It is in part due to the fact that although the sunlight
is the most powerful antagonist of the pestilence that
walketh in darkness, to wit, the omnipotent disease-germs
or Bacteria, the warmth and overflowing plenty of Summer
days favour their fatal multiplications; as is illustrated
by many fevers. It is partly because the machinery of
life is by no means perfectly self-repairing, and that the
organism in living is continually going into debt — death
being the extreme of insolvency; as is illustrated by all
organisms whose efforts are followed by irremediable nerve
fatigue. And it is partly because during an early chapter
in life's history immortality was pawned for love, and
death was made a price for giving rise to new lives;
as is illustrated by so many butterflies and other animals,
not to speak of flowers, which die soon after reproducing.
But no one can have realised what the work of Summer
actually means, without feeling that there is profound truth
in the doctrine of reincarnations, that nothing is ever really
lost in this economical world. Matter is ever circulating, in
Summer most actively ; energy is ever changing, in Summer
most of all. Nothing is ever lost; all things flow. The
moistened dust and the quivering air become the grass,
the grass the deer, the deer the huntsman, the huntsman
the tiger, the tiger — with the aid of Bacteria — grass again.
For so the world goes round, and, " after last, returns the
first, though a wide compass round be fetched."

SUMMER FLOWERS

WE have seen that the Biology of Summer has for
its two main problems the manifold effect of heat
and light upon living creatures, and the increasing prepon-
derance of reproduction over nutrition, of flower over leaf,
of " Love " over " Hunger." Heat, within limits, makes the
wheels of life go more quickly round ; it accelerates de-
velopment and the lashing of cilia ; it makes egg-cells twin,
and it keeps the green flies parthenogenetic ; and it has
a hundred other influences. Light promotes assimilation
in leaves and slows growth ; it induces pigmentation and
quickens our pulse ; it makes Bacteria live so quickly that
they die ; and it has a hundred other influences. But our
present study is concerned with the growing preponderance
of flower over leaf.

Every one knows that a typical flower is made up of four
different kinds of parts, arranged in circles or whorls, one
within the other. Outermost are the sepals, making up the
calyx ; they are usually firm and green ; they protect the
bud and steady the opened flower. Next come the petals,
making up the corolla ; they are usually delicate and
coloured, often fragrant, and often making nectar ; they thus
attract insect-visitors, and they are also useful in protecting
the even more important parts farther in. The third whorl
consists of the rod-like stamens, whose heads or anthers
make the golden-yellow fertilising dust or pollen. The inner-
most parts of the fourth tier are the carpels, which bear
microscopic eggs, each of which, if fertilised, will develop into

SUMMER FLOWERS 113

an embryo plant. Or, to put it in another way, the carpels
bear possible seeds or ovules, which become real seeds when
the fertilising golden dust penetrates into them.

It was a very important — unifying and clarifying — dis-
covery, in which the poet Goethe had a large share, that the
flower is really made up of four tiers of leaves, adapted to
different uses — protective and steadying leaves, protective
and attractive leaves, pollen-making leaves, and seed-making
leaves. The different parts all grow out of the flower-stalk
as leaves do, and they often hark back to their primary con-
dition— for instance, when the plant is overfed. A Canter-
bury bell may become a crowded green tuft, and most
" double " flowers are due to stamens becoming petaloid.
Another argument (out of many) may be found in the flower
of the water-lily, where the substantial green sepals pass
quite gradually into white petals, and these narrow into
straps, which pass into yellow stamens. In this flower and
others like it we find it difficult to tell where sepals stop and
petals begin, or where petals stop and stamens begin. In
such ways we may convince ourselves that, though the four
parts of the flower have different names and forms and uses,
they have, fundamentally, a common nature, for they are all
leaves, transformed in various ways and combining to fulfil
the plant's chief end — that it should produce seeds which
will bear next year's flowers. This was a discovery of the
same nature as one of older date — that the forelimb of a
frog, the paddle of a turtle, the wing of a bird, the flipper of
a whale, the wing of a bat, and the arm of man, and so forth,
are all fundamentally the same in essential structure and in
mode of development ; but the discovery of the nature of
the flower was perhaps a greater illumination.

In one of the letters in Fors Clavigera, Ruskin com-
mented somewhat savagely on the kind of botany that
rejoiced in proving that there was " no such thing as a

H4 THE BIOLOGY OF THE SEASONS

flower " ; but further reflection lead him to see the signifi-
cance of Goethe's thesis, and he then wrote a famous passage,
which describes the nature of the flower in a beautiful way,
combining inaccuracy and insight in a manner absolutely
incomparable. " You will find," he said, " that, in fact, all
plants are composed of essentially two parts — the leaf and
the root — one loving the light, the other darkness ; one
liking to be clean, the other to be dirty ; one liking to grow
for the most part up, the other for the most part down ; and
each having faculties and purposes of its own. But the pure
one which loves the light has, above all things, the purpose of
being married to another leaf, and having child-leaves, and
children's children of leaves, to make the earth fair for ever.
And when the leaves marry they put on wedding-robes, and
are more glorious than Solomon in all his glory, and they
have feasts of honey, and we call them flowers."

In the great majority of cases the pollen is carried from
one flower to another of the same kind by an insect intent
on its own affairs — collecting nectar and pollen. As the
dusting with pollen secures not only fertilisation, but cross-
fertilisation, and as the latter is sometimes the only possible
mode, and sometimes, at least, the most advantageous mode
as far as the crop of seeds is concerned, we are not surprised
to find that flowers exhibit numerous adaptations which
attract insect-visitors of a profitable kind, and secure that the
visits are made the most of.

Taking the simplest attraction first — that of nectar-
production — we have no difficulty in recognising its natural-
ness. The plant is a sugar-factory ; the leaves make enough
and to spare ; there is a surplus which oozes out as " a feast
of honey." But an unregulated overflow would be obviously
disadvantageous in attracting unwelcome guests, thus
nectaries become floral, and their position in the flower is
often finely strategic. When the fit and proper visitors have

SUMMER FLOWERS

come and gone, when pollination has been effected, when the
season is getting on, then the nectaries close up, the feast is
over, and the fruit begins to fill. We are aware that nectar is
often more than sugar, that it may include balsam and gum,
and so forth ; we are aware that a big book might be written
about nectaries ; but we are only concerned here in stating the
general biological aspect of a very familiar fact — the flowers'
feasts of honey.

The second accessory characteristic of the flower is
fragrance, to which many insects are extremely susceptible.
What is the primary significance of this incense, whose
secondary advantageousness is so obvious ? The answer
which suggests itself is that the fragrant substances are
waste-products — in some cases by-products — of the essential
metabolism that goes on in the plant. It will be remembered
— we have only to think of woodruff and lavender and pepper-
mint— that the fragrant substances often occur in leaves,
though flowers have made a speciality of their production.
The chemists have distinguished a great number of these
aromatic compounds, such as the soporific aminoid in haw-
thorn ; the benzoloids in mignonette and violets ; the
paraffinoids in valerian, pelargonium, and roses ; the
turpenoids in orange and lavender ; the strange indoloids,
said to arise from broken-up proteids, in aroids, Aristo-
lochia, and Rafflesia which attract carrion-loving flies. There
are said to be over five hundred of these aromatic compounds
on the catalogue, and there are doubtless very many more.
For different species, when they are worthy of the name,
show individuality in their chemical processes as well as
in structure and habit, and it seems not unlikely that we
are as near the heart of the matter when we distinguish
flowers by their fragrance as when we count the microscopic
chromosomes in their nuclei. As with nectar-production,
so with fragrance ; there are endless subtleties of adapt a-

n6 THE BIOLOGY OF THE SEASONS

tion, one of the most familiar being that some flowers, such
as Grass of Parnassus, give forth incense only in the sunshine,
while others, like the Evening Campion, reserve this for the
night.

After discussing the volatile ethereal oils to which the
odours of plants are due, Professor S. H. Vines says : " With
regard to the function and fate of these aromatic substances,
it appears that they are of no use in the constructive pro-
cesses ; they are to be regarded as waste-products, destined,
for the most part, to be thrown off. . . . We may venture
upon the general statement that the higher plants, at least,
cannot avail themselves of carbon when combined in an
aromatic molecule for the purposes of their constructive
metabolism. . . . Although the aromatic substances are
probably to be regarded simply as waste-products, yet some
of them are indirectly of use to the plant. We have seen
that the odours of plants are due to the presence of volatile
ethereal oils, and it has been ascertained that the odours of
flowers serve to attract insects, and thus contribute to ensure
fertilisation." l

The third accessory characteristic of the flower is its
colour, which appears to be attractive to many of the insect-
visitors. Let us consider the colour, first of all, in its internal
or physiological aspects. It is due to a great variety of
pigments, some of which are more intelligible than others.
Some are fixed in protoplasmic corpuscles, notably those of a
yellow, orange, brown (and rarely blue) colour. These are
mostly derivatives of the leaf-green or chlorophyll, and the
yellow anthoxanthin is a common example. The others are
dissolved in the cell-sap, notably those of a white, violet,
blue, red (and rarely yellow) colour. Most of these are deriva-
tives of tannin and other bitter principles, and the blue
anthocyanin is a common example.

i S, H, Vines, Lectures on the Physiology of Plants, Cambridge, 1886.

SUMMER FLOWERS 117

Our knowledge of pigments is still far from satisfactory,
but there is considerable evidence that many of them are
useless by-products in the economy of the plant. Thus Pro-
fessor Vines says : " With regard to their chemical nature, the
colouring matters of plants are considered to be closely con-
nected with the aromatic group of substances. As to their
physiological significance, they may be regarded simply as
waste-products in so far as their direct use in constructive
metabolism is concerned ; but indirectly they are, in many
cases, of great importance. Chorophyll is essential to
the process of the formation of organic substance from
carbon dioxide and water. The colours of flowers play an
important part in attracting insects to visit the flower, and
by this means cross-fertilisation is ensured."

It seems safer at present to avoid general formulation, for
there are many indications, both among plants and animals,
that pigments have very diverse meanings in the internal
economy of the organism. Some are unimportant by-
products, of little or no direct internal use after they are
formed ; others are very important by-products, of much
direct internal use. Some seem to belong to the series of
reserve-products, but most seem to be waste-products — the
ashes of the vital fires. In some flowers the bright colouring
means scanty local nutrition; in others, too rapid life; in
some, too little moisture ; in others, too much light ; but
in the majority it means beauty for ashes.

As to the general secondary significance of the colour of
flowers, there is little doubt — it is attractive to insect -visitors
This proposition may be upheld without insisting that all
floral colour has this meaning, and without implying that
the colour affects the insect's eye as it does ours. Grant
Allen, in one of his brilliant essays, commits himself to the
impetuous and eliptical statement : " Insects produce
flowers ; flowers produce insects. The colour-sense pro-

THE BIOLOGY OF THE SEASONS

duces brilliant butterflies and brilliant beetles." Darwin
went the length of saying : " If insects had never existed on
the face of the earth, our plants would never have been
decked with beautiful colours.'*

Let us state the thesis more fully. Although many
flowers seem able to fall back on self-pollination, it is of
advantage to most that insects should visit them. Those
most visited are most certainly fertilised ; they produce
larger and more vigorous crops of seeds than those of the
same kind which have been little visited. Long ago some of
the primitive flowers began to form pigments as by-products
or waste- products of their everyday metabolism. Those that
varied in the direction of conspicuous or attractive colora-
tion were most visited, therefore most effectively fertilised,
and therefore most prolific in their multiplication. The
uncoloured or dully coloured were less likely to be visited, and
they would tend to go to the wall. In the case of each kind
of flower that was visited by insects attracted by colour,
there would thus tend to be a survival of the gay and an
elimination of the dull. When we keep the insects in their
proper place as the selectors of the variations which the plant
afforded, the thesis appears more reasonable.

If we are convinced that pigments are natural expressions
of the normal up-building and down-breaking of the plant,
if we can find physiological reasons why they should occur
(chloropyll apart) more particularly in connection with the
flower, and if we do not find any reason for regarding con-
spicuousness of colouring as disadvantageous, then, it seems
to us, we can keep insects in their place as selectors, and give
flowers some credit for their own beauty.

In regard to the attractive power of floral colour, there is,
to say the least, a need for cautiousness of statement. It
has been repeatedly observed that bees do not seem to care
much for yellow flowers, that they prefer blue-violet to any

SUMMER FLOWERS

other colour, that they frequent reds with a tinge of purple,
but leave cinnabar reds alone. In such observations it is
necessary to be very careful. A flower is a complex of
stimuli, and the fact that blue-violet blossoms are most
visited does not, in itself, prove that they are preferred
because of their colour.

Sir John Lubbock, now Lord Avebury, tried to get away
from the risk of fallacy by baiting different slips of paper
of different colours with the same sugar, and the interesting
and valuable result of his experiment was that the bees
" preferred " the blues and violets to yellows, and so on.
Even here, however, one must tread warily, since it seems
likely that the bee has established associations — partly
instinctive and partly based on previous experience, so that
the stimulus of certain colours may act merely as the
memorandum of previous good feeding. And, again, there
seems good sense in Plateau's objection, that observations
and experiments on this subject have not discriminated
adequately between colour and absolute intensity of illumi-
nation. Those insects that love light choose the brightest
surfaces; but brightness is one thing, and colour is
another.

Plateau worked a good deal with dahlias, which are
visited by humble-bees, butterflies, and other insects. His
method was to hide the colour and form of the inflorescence
by means of pieces of cardboard, which were variously
coloured (white, black, green, etc.), or by means of green
leaves. The results of his experiments led him to a heretical
conclusion : " The form and the colour do not seem to have
any attractive role ; the insects are evidently guided to the
capitula of the composites by some other sense than sight —
probably by smell." Now, we do not believe that these and
similar experiments have upset the theory that floral colour
is one of the attractive stimuli which draws insects to the

120 THE BIOLOGY OF THE SEASONS

flowers, but perhaps they may indicate the risk there is
of exaggerating a truth till it becomes false.

In support of the generally accepted view that brightly
coloured petals are attractive " signs " which draw customers
to the floral " Gasthaus," there is a multitude of observations
as to the frequency of visits paid by particular insects to par-
ticular flowers. It is instructive to give a holiday afternoon
to watching, for instance, how one of the big humble-bees (e.g.
Bombus hortorum) behaves on a flower-covered bank. She is
so extraordinarily selective. And as we see this, it sends a
thrill through us to remember that Aristotle watched the
same sort of thing more than two thousand years ago. In
his Natural History it is written : "A bee, on any one
expedition, does not pass from one kind of plant to another,
but confines itself to a single species — for instance, to violets —
and does not change until it has first returned to the hive."
After more than two thousand years, the botanist Kerner
von Marilaun, who wrote one of the most living of all the
botany books, watched not the hive-bee, but Bombus
montanus in an Alpine valley. He saw it visiting only
Anthyllis alpestris, and passing over Pedicularisjacquini and
P. incarnata ; while in another valley the same species of
bee buzzed from one Pedicularis blossom to another, and
passed over the Anthyllis attractions.

We have now a perfectly precise and rapidly growing
record of the habitual pollinators of particular flowers,
and there has already been more than one good example of
a truly biological (or oecological, if you like) student's
'' Flora," which tells for each plant, not only its diagnostic
characters, but its welcome and unwelcome insect-visitors,
its gall-producers (if it has any), its parasites, its seed-
distributors (if it has any), its characteristic environment,
and it? plant associates. In hoc signo laboremus.

Corroborations come also from wide outlooks, in which

SUMMER FLOWERS m

the exception often proves the rule. Thus Alfred Russel
Wallace, still happily the Nestor of the evolutionist camp,
pointed out long ago that there were few bright blossoms in
the Galapagos Islands (600 miles west of South America), and
that there were few insects. But in Juan Fernandez, 400
miles off Chili, there are several very conspicuous flowers,
though there are no bees, only four moths, and one butterfly.
There are, however, crowds of humming-birds, which are
pollinators of high degree.

In studying a problem like the inter-relations of flowers
and insects, it is necessary to pursue a rigorous analytic
method, abstracting off first one factor and then another,
inventing super-ingenious experiments to discover whether
the bee comes to the blossom because the blossom is
purple or because it is bright, because it is coloured or
because it is fragrant, because it is fragrant or because
it has lots of nectar, and so on. This is inevitable,
and it is thus that science is built up. We have a lurking
suspicion, however, that the scientific inquirer is apt
sometimes to end in fallacy by projecting his analytic inlook
upon Nature again. To return to a concrete case, we mean
that a foxglove flower is a complex of stimuli, and that the
bee which climbs up its spire is a complex of sensory recep-
tivities. In all likelihood, the bee visits the foxglove on a
bank and leaves out all others, not because the foxglove has
a subtle pinkish-purple colour, but because it is a foxglove.
It is the tout-ensemble that counts. But it is difficult, some-
how, to make good science of this.

It would be unpardonable to quit the subject of
summer flowers — even in these brief glimpses — without
coming back to reality — the gorgeous pageant of Flora's
Feast. The tide which sets in with a rush in Spring reaches
its high -water mark in Midsummer. Play gives place to
industry, and the extravagance of youth to the strenuous-

122 THE BIOLOGY OF THE SEASONS

ness of maturity. The buds are replaced by hard-working
leafy boughs with extraordinarily intense activity, especially
in the sunlight. The bud-like, more primitive, early flowers
are replaced by more liberal floral magnificence. On all
sides we see young things passing through adolescence to
mature strength, and love is crowned.

As a picturesque emblem of the fundamental fact — the
rising wave of life — we may, in conclusion, allude to the
observation of a remarkable scientific genius, Dr. Buchan,
who has left a deep mark in the science of Meteorology, that
of British plants which flower between April and July, the
succession of colours tends on an average to be the order of
the rainbow tints — from blue, through yellow, to red.

SUMMER INDUSTRIES

WE mean by industries those external activities which
are concerned with the sustenance and care and
development of life, or, in great part, with " production."
They are external activities, which operate directly on the
outer world, moving things about, changing matter and
energy from one form to another, bringing them into more
useful or, at any rate, more desirable shapes and arrange-
ments. Thus neither the beating of the heart nor thinking
can be called industries, though they are very important
activities, and the latter is very fatiguing.

Industries, then, are concerned with getting hold of
things and powers, transforming them, storing them,
distributing them, and, in the case of man, exchanging
them. The prime aim of industry, even though it be
unconscious, is to sustain and develop life ; its external
result is always a product, or some change in the form,
position, availability, or utility of a product. Thus war
is not an industry, but weaving is ; eating is not an industry,
but hunting is ; courting is not an industry, but keeping
the home agoing is. So this biological study of industries
does not even touch on a number of very interesting animal
activities, such as wars and wanderings, courtships and
plays.

A second and more difficult introductory note is
necessary. The activities and industries of animals are at
many different levels when considered from the point of
view of the associated mental and nervous control. We

123

124 THE BIOLOGY OF THE SEASONS

may arrange them on a staircase of five steps, or, better
still, on a long inclined plane marked by five more or less
clear divisions.

Lowest are those activities which go on without there
being any nervous system involved. Such are the most
important transformations of matter and energy that we
know of in the whole world, namely, those that go on
in green leaves, when, with the help of the sunlight shining
through a screen of chlorophyll, they form complex sub-
stances like the starch of the potato and the gluten of wheat
out of the simple elements of earth, water, and air. It
cannot be called an industry in the strictest sense, since
plants do not form products outside of themselves, but it
may be taken as an example of vital activity that goes on
without nervous control. We have no warrant for calling
it anything but unconscious. There are many internal
activities in animals on the same level ; they go on in-
dependently of direct control from the central nervous
system. It is well known that the turtle's heart will go on
beating long after the bulk of the animal has been made
into soup.

On a second level, there are simple reflex actions, which
usually require the possession of a definite nervous system,
but are not associated with what we call conscious control.
The organism does not know that it does them, unless it
happens to fix attention on their performance. We
touch a hot iron, and without, in the strict sense, willing it,
we draw our finger away. A stimulus has travelled up a
sensory nerve to the spinal cord, and a stimulus has passed
down a motor nerve to the muscles, commanding them to
effective action. This is a reflex action of a simple kind,
but there are many more elaborate activities and even
parts of industries which appear to be compound reflexes.
They are, as we say, automatic. If we may judge from

SUMMER INDUSTRIES 125

our own experience and from experiments made on animals,
some of them seem not to be attended with any central
consciousness at all, while of others it seems safer to say
that they do not rise to the focus of consciousness.

On a third level are those activities which are called
instinctive. By which is meant that they are performed
in virtue of an inherited capacity ; that they require no
learning or experience, though they are usually improved
by both; that they are shared alike by all members of
the species, or, at least, by those of the same sex. Most
animal industries must be included here, though there is
sometimes a spice of intelligence intermingled in their per-
formance. The spinning of spiders, the comb-building of
bees, the paper-making of wasps, the agricultural industries
of ants, and so on, seem to be, for the most part at least,
instinctive. The animals are, so to speak, hereditarily wound
up to do what they do. They are born with a ready-made
power of doing certain things well. The difficulty is that
some animals learn with great rapidity, so that it is often
impossible without experiment to distinguish what is
instinctive from what has been intelligently learnt. When
a complex performance is gone through without a hitch
the very first time it is attempted, and in the absence
of any model, we may be fairly sure that it is instinctive,
unless the performer has given other evidence of a high
order of intelligence. Experiment may prove this, thus
Professor Lloyd Morgan has been particularly successful in
getting at pure instinct by his method of studying young
birds hatched in an incubator and brought up in isolation.

On a fourth level are intelligent activities, which include
some animal activities and parts of others. Here a higher
note is struck. The animal is not only conscious, but
controlling and contriving. It adapts old means to new
ends, it profits by experience, it puts two and two together

126 THE BIOLOGY OF THE SEASONS

in a simple way at least. We cannot redescribe these
activities to ourselves without using psychological terms,
without supposing that the animal draws inferences of
some sort and thinks in the concrete at least. Thus when
a spider departs from its beaten path to make a web adapted
to entirely novel circumstances — for instance, to the wind
on the seashore — when a bee mends its web in a fashion
that we cannot help calling ingenious, when a monkey
works a screwdriver, when an elephant helps to make a
railway, and so on, we must allow at least a spice of intelli-
gence, and often much more. There is room, of course,
for much difference of opinion ; perhaps if the truth were
known, for man to speak of " admitting " the intelligence
of, say, an elephant or a collie is not far from the absurd.
We have to steer between two extremes — on the one hand,
of regarding animals as automatic machines of an amazing
intricacy ; on the other hand, of reading the man into the
beast. Because the hive-bee makes such beautiful hexagons,
it is not to be spoken of as mathematical ; on the other
hand, every naturalist must deprecate the arrogance of a
recent pronouncement that men were brain-organisms and
animals gut-organisms.

But there is a higher level still — that of rational activity ;
and, so far as we know, we have this field all to ourselves.
By rational, as distinguished from intelligent, is meant,
that we cannot imagine the activities being carried out
without general ideas, without conceptual inference as
distinguished from perceptual inference, without thinking
in the abstract. No one will suppose for a moment that
man is always on this high level ; in fact, he is on it far too
little, much of our industry, for instance, being in details
non-rational and even non-intelligent. Nor dare we deny
that some of the higher animals may show the beginnings of
conceptual inference or of rational activity. From an

SUMMER INDUSTRIES 127

evolutionist point of view, this seems highly probable. All
that we do say is, that there is no case of animal cleverness
on record which may not be described without crediting
the performer with general ideas — that is to say, all may
be accounted for on the supposition that the activity is
either instinctive or intelligent. Some lovers of animals
think that we might be more generous when we are at
it, but the scientific method holds fast by the law of parsi-
mony, which forbids us making larger assumptions than are
warranted by the facts.

The primitive human occupations of hunting, fishing,
shepherding, and farming afford a convenient classification
of a large group of animal industries — those concerned
with food-getting.

Of the primary activity of hunting there are many
modes. Lurking is illustrated by the crocodile at the
water's edge, by the snake in the grass, by the octopus
among the rocks ready to grapple a dreamy fish, by the
larval ant-lion who digs in the sand a pitfall for unwary
insects, and by a thousand more.

Others prowl about in search of their prey — the cats
large and small treading noiselessly with claws of steel
under their velvet gloves, the snakes gliding swiftly in the
jungle like Kipling's famous Kaa, the foxes alone, the
wolves in packs, the bats and owls and a hundred others by
night, the eagles and swifts and a thousand others by day,
the monkeys seeking out the orchards, the otter the trout-
pools, the walrus the mussel-beds, some with wondrous
swiftness like the weasel after the rabbit, others with great
leisureliness like snails on the hunt for mushrooms. There
is no end to the variety of ways and means.

Some of the details of device are full of interest. The
thrush breaks the snails' shells against a stone, making
heaps of the remains quaintly suggestive of the archaeo-

128 THE BIOLOGY OF THE SEASONS

legist's " kitchen-middens " ; rooks sometimes let fresh-
water mussels drop from a height on to the gravel, and it
was thus that a Greek eagle killed the poet ^Eschylus by
letting a tortoise drop on his bald head, which glistened like
a white stone ; the oyster-catcher knocks the limpet off the
rock with a dexterous stroke of its strong bill ; the grey
shrike stakes its victims on thorns.

Of hunting by means of snares the best illustrations are
of course afforded by spiders, of which one instance may
be given, on the authority of Dr. Emil Goeldi, formerly
Director of the Museum in Para. It concerns an early
rising spider, Epeiroides bahiensis, which was common in
Goeldi's garden at Para, though the web was never to be
seen. The Director's son, a boy of seven, determined to
sit up all night to solve the mystery, and he discovered a
very interesting peculiarity. The spider makes its web in the
early hours, but rolls it up and decamps with it after the
sun rises. Penelope-like it destroys its web daily, but not
without result to man as well as to itself, for it catches the
minute-winged males of the destructive Coccus insects, of
Dorthesia americana in particular. After retiring under the
shade of a leaf, the spider investigates the insects in its rolled-
up net, and spends the hot hours in digesting their juices.
Its behaviour reminded Dr. Goeldi of a southern bird-
catcher hastily gathering his roccolo together as the dawn
breaks, but with this difference, that the spider " does not
stop to pull out the captives, wring their necks, and throw
them into a bag. It gathers up its net and postpones the
work of revision until it gets home."

Fishing is only a variety of hunting, but may be con-
sidered separately for a moment. Typical of the patient
angler, the heron stands by the pool-side — still as a statue,
but able to strike with almost electric suddenness, or fly
away with dignity if we disturb his fishing. But perhaps

HERON FISHING
(V)

SUMMER INDUSTRIES 129

we should have given first place to the angler — Lophius
piscatorius — a fish who fishes, a fishing-frog he is often
called. He is very inconspicuous as he lies squat on the
sand in shallow water, and he is sometimes half covered
with sand. Three elastic rods, one of them very strong, rise
from the middle line of his back, and at the end of each
there dangles a shred of skin like bait at the end of a fishing-
line. These living fishing-rods are hinged at the base, so
that they can be lowered or raised, and they are obviously
transformed fin-rays. It is supposed by many that the
shreds of skin, dangling loosely in the water, suggest worms
to curious little fishes ; it is supposed, at least, that they
serve to attract attention ; what is certain is that many
small fishes are engulfed in the angler's wide gape, and
gripped firmly by backward-bending hinged teeth which
make entrance easy but exit difficult.

The tales of the fishing exploits of animals, like stories
of fishing at a higher level, are often a little difficult
1o believe. The deep-sea fish Chiasmodon niger has been
known to swallow a fish larger than itself ; a large spider
has been known to land a small fish ; the archer fish,
Toxotes jaculator, is said to make its living by shooting drops
of water, with Transatlantic precision, on passing insects.
But perhaps more instructive than such oddities is the habit
pelicans have of fishing in company, and wading shorewards
in a deadly crescent, prophetic of the seine-net. Clumsy
birds they are, but exhibiting a remarkable power of co-
operative industry, if reports are true. We venture to quote
Kropotkin's account : x " They always go fishing in numerous
bands, and after having chosen an appropriate bay, they
form a wide half-circle in face of the shore, and narrow it by
paddling towards the shore, catching all fish that happen to
be enclosed in the circle. On narrow rivers and canals they

1 Mutual Aid, 1902.

130 THE BIOLOGY OF THE SEASONS

even divide into two parties, each of which draws up on a
half-circle, and both paddle to meet each other, just as if two
parties of men, dragging two long nets, should advance to
capture all fish taken between the nets when both parties
come to meet. As the night comes they fly to their resting-
places, — always the same for each flock, — and no one has
ever seen them fighting for the possession of either the bay or
the resting-place. In South America they gather in flocks of
from forty to fifty thousand individuals ; some enjoy sleep
while the others keep watch, and others again go fishing."

Of shepherding, the only clear illustrations are to be found
among ants, some of which (e.g. Lasius niger and Lasius
bmnneus) keep aphides or green-flies, and others scale-
insects. This extraordinary habit was well known to
Linnaeus, who called the aphides the ants' cows (vacca
formicarum), and it has received considerable attention from
many observers. Perhaps it began in the simple fact that
the ants and the aphides frequented the same trees, dining,
as it were, at the same bountiful table. Then it was dis-
covered that the aphides would yield up some of their
" honey-dew " when licked or tickled, and the ants traded
on this. Gradually, perhaps, the ants began to take some
charge of their cattle, even building " aerial stables " for
them on the branches. The ants are accustomed to put
their pupae out to be sunned, and to carry them back again
when it rains ; perhaps this habit led on to what at first sight
is so startling, that the ants take aphides down into their
underground nests. " In Autumn the aphides lay eggs in
the cellars to which they have been brought by force or coax-
ing or otherwise, and these eggs the ants take care of,
putting them in safe cradles, and licking them as tenderly as
they do their own." It is probable that this very inter-
esting habit arose neither deliberately nor casually, but by
the gradual extension of habits previously established ; and

SUMMER INDUSTRIES 131

it must be remembered that ants and termites are remark-
able for their friendly associations with other insects, which
they tolerate in their nests, sometimes as useful inmates,
oftener apparently just as pets.

What we have just referred to recalls what Edward
Jacobson has recently reported regarding a mosquito which
seems to milk ants ! For that is what it comes to. The
mosquito frequents certain trees in Java, on which the ants in
question (Cremastogaster diformis) go to and fro. It hails a
passing ant and strokes the head with quick movements
of its forelegs and antennae, probably tickling, perhaps
massaging, the ant. In any case, the ant emits a drop of
juice, which the mosquito, sucks up. Then the ant goes on
its way, a pathetic instance of naturally good abilities, spoilt
by an exaggerated state-socialism. The gentle mosquito
has been named Harpagomyia splendens by de Meijere, who
points out that the creature cannot bite ! Jacobson found
two other Diptera in Java which seem also to have learned
how to tap ants. Like the mosquito, they have discovered a
deep wisdom in the old advice — " Go to the ant, thou
sluggard/'

Agricultural industries are again illustrated among the
ants. The harvesting of grain, believed in from ancient
days, but challenged by careful entomologists such as
Latreille, Huber, and Kirkby, has been satisfactorily de-
scribed by Moggridge and others. In his Agricultural Ant
of fexas, M'Cook gave an account of the abundant red-
bearded ant (Pogonomyrmex barbatus), which weeds out cir-
cular discs in open ground, tolerating only the needle-grass
(Aristida), whose seeds are gathered and stored along with
others in underground granaries. " Not a plant is allowed
to intrude upon the formicary bounds ; and, although often
seen, it was an interesting sight, after pushing through the
high weeds, to come upon one of these nests, and observe the

132 THE BIOLOGY OF THE SEASONS

tall, tough vegetation standing in a well-nigh perfect circle
around the edge of the clearing. The weeds had crowded up
as closely as they dared, and were held back from the for-
bidden grounds by the insects, whose energy and skill could
easily limit their bounds. Certainly, ants capable of such
work could readily have cleared away growing stalks of the
Aristida. In fact, after the seed has ripened in the late
summer, they are said to clear away the dry stalks in order to
make way for a new crop. It is this that j ust ifies the reputa-
tion of Barbatus as a farmer. She has not been seen — so far
as the author knows — sowing the seeds, but she permits
them to grow upon her formicary bounds, and afterwards
utilises the product." l

In a recent careful study of Messor barbatus, a leaf-
cutting and seed-gathering ant of Dalmatia, Professor F. W.
Neger of Tharandt noted that most of the seeds (of Legum-
inosae in particular) were allowed to begin to germinate
before the ants put them out to dry. This seems discrepant
with what is often stated, that ants treat the seeds in such a
way that they cannot sprout. But Neger suggests that the
germination permitted has the advantage of bursting the
seed-coats. It is then stopped by exposure, so that it does
not go far enough to ferment the starch into maltose and
dextrin. When the seeds are thoroughly dry and dead, they
are taken back again to the nest and chewed into a dough.
This is baked in the sun into minute biscuits, which are
stored. Here, in fact, we have an industry that comes very
near to cooking.

One of the most extraordinary habits of the termites or
white-ants, so abundant in warm countries, is that about
thirty different species feed on moulds which are grown
within the termitary on specially constructed maze-like beds
of chewed wood. The fungi are believed to afford a supply

1 H. C. M'Cook, Nature's Craftsmen, 1907.

SUMMER INDUSTRIES 133

of nitrogenous material which is scarce in the termite's
ordinary diet of wood. It is interesting that a similar habit
of growing moulds occurs in some of the true ants which
belong to quite a different order of insects. And a similarly
puzzling convergence is illustrated by the fact that termites,
like true ants, often have boarders in their hills, mostly small
beetles, neither hostile intruders nor parasites, but guests
which are fed and cared for apparently on account of a
palatable exudation, with a pleasant narcotising effect on
the termites !

Many animals, besides ants, illustrate storing, either for
themselves or for their offspring. We need not here do
more than mention squirrels and beavers, hive-bees and
scarabees, for we shall return to storing in its more
appropriate seasonal setting as an autumnal industry.

After the primitive industry of securing food, which has
so many forms, may be ranked that of making shelters, in-
cluding clothes. Although Carlyle and others have pointed
out that man is the only clothed animal, the point is debate-
able. It is difficult not to regard as clothing the cocoon of a
silk-worm or the case of a caddis-fly, and there are crabs
which fix seaweeds on to their backs, or cut off the tunic of
a sea-squirt and use it as a cloak.

Of making shelters there is an embarrassing wealth of
illustration. They are often hollowed out in earth and wood,
and vary from rough burrows like a rabbit's, to a beauti-
fully finished structure like the tube of the female trap-door
spider, with its hinged door and its side-room with a curtain
over the entrance. Or they may be made of light materials,
woven or sewn or somehow fastened together, one of the
most striking types being the decorated bower of the bower-
bird, since it is a house rather than a cradle, as most nests
are. Or they may be genuine buildings of clay or other
material. At one end we may place the substantial terrrn'-

134. THE BIOLOGY OF THE SEASONS

tary, sometimes ten feet high and strong enough for a man to
stand on ; at the other end the dainty nest of the wasp,
almost as light as a feather.

Let us take one instance of the manner of working — the
behaviour of the tailor-ant, Oecophylla smaragdina, common
in hot countries. One must confess to a feeling of relief at
finding recent circumstantial confirmation of some of the
extraordinary tales that have been told of this creature.
Professor E. Bugnion has recently vouched for the habit these
ants have of using their silk-secreting larvae as needle and
thread when they are binding leaves together to make a
nest ! They sometimes find it difficult to bring two rather
distant leaves close enough together to be sewn. Bugnion
confirms the tale that five or six will form a living chain to
bridge the gap. The waist of A is gripped in the mandibles
of B, who is in turn gripped by C, and so on — a literally
living chain, a notable gymnastic feat. Several chains will
work together for hours on end trying to draw two leaves
close together.

Even this brief study may serve to suggest a number of
general reflections. The first is simple enough, that these
industries of animals play a fundamental part in the business
of the earth. This is evident when we think of the bees that
fertilise the flowers, or of the earthworms that make the soil,
or of the coral polyps that build up islands, and so on, till one
may count a thousand. Secondly, although we are far from
confident as to the psychological interpretation of many of
the activities, the fact is plain that they are usually ex-
tremely effective in their performance and beautiful in their
result. Thirdly, although we must be careful in applying to
animals terms rich in ethical content, such as altruistic, the
fact is plain that great labour is often expended for others —
for the offspring — which the toilers in not a few cases never
survive to see,

COURTSHIP OF BIRDS

IN most birds the amatory period is sharply punctuated.
Their love is seasonal and part of the Spring. It
becomes parental, laps the family in its folds, and then it
seems to wane away into little more than kin-feeling, except
in those birds that are monogamous and lifelong com-
panions.

Partly, perhaps, because the time of ardent love is so
sharply punctuated, the seasonal expression of it is more
striking than in most other creatures. We see love con-
densed, so that for a time it sublimes the whole life. The
mood changes, the feathers change, the voice changes, the
very movements change, under the pervasive influence of
love.

Many male birds acquire their special characteristics of
colour and plumage, of song and flight, only as they approach
the crest of the wave of adolescence, and some only retain
their full glory while the love-impulse lasts. Some cock-
birds put on long plumes, feathery tresses, brightly coloured
combs and wattles, top-knots and curious markings, which
they display before their desired mates with what seem to us,
from a considerable mental distance, like emotions of love and
vanity. Others vie with their rivals in fierce tournaments,
and many try to sing their neighbours down. Some indulge
in quaint strutting dances, and others in elaborate displays of
their flying powers. Especially on the male side there is an
exaltation of the whole life — physical as well as psychical.

The whole subject of preferential mating among animals.

136 THE BIOLOGY OF THE SEASONS

is full of difficulties, and though birds have been so much
studied, there is still great uncertainty as to the significance
of their behaviour. It seems as though this must remain
until ingenious experiments are devised to test the inferences
from observation.

Every one recognises that the advent of the pairing season
is marked by a variety of unusual activities on the part of
male birds — activities of song and flight, of dance and dis-
play, which seem to express excited states of feeling and
to prompt similar responses on the female's part. We may
sum up the characteristic activities in the word " court-
ship," though there are few data which would enable us to
decide how far there is deliberate wooing on the one hand or
deliberate choice on the other.

SEX-DIMORPHISM

No one without a microscope can tell a male sea-urchin
from a female sea-urchin, and in the lower reaches of
the animal kingdom an external uniformity of the two sexes
is very common. As we ascend the series, however, differ-
ences between the sexes become more and more frequent and
conspicuous. The essential functions of the males and the
females become more and more different, as we may see if
we contrast starfish with fish, or fish with mammal ; their
habits of life diverge ; and to the primary differences there
are added all manner of secondary peculiarities. In the
higher reaches of the animal kingdom we come face to face
with marked " sex-dimorphism," familiar in the contrasts
of peacock and peahen, ruff and reeve, stag and hind, lion
and lioness. In the contrast of man and woman the
dimorphism finds its highest and subtlest expression.

As to the biological significance of this sex-dimorphism
there is much difference of opinion, and we can only hint at

COURTSHIP OF BIRDS 137

one of the lines of interpretation. There is much to be said
for the view that there is a deep constitutional difference
between the male and the female organism — an initial or
germinal difference in the balance of chemical changes. The
female seems to be relatively more constructive, relatively
less disruptive. There is a fundamental difference in what
we call figuratively the protoplasmic rhythm — the physi-
ological gearing. This initial difference leads to the
primary functional distinction between male and female.
But it also determines, either from the start, or after
maleness and femaleness have been in part established,
what particular expression will be given to a whole series
of minor characters — both structural and functional —
whether a masculine or a feminine expression. It is
convenient to keep the terms maleness and femaleness
for the primary functional distinction — the male salmon
depositing the fertilising milt upon the eggs which are
liberated from the roe or ovary of the female salmon ;
and to keep the terms masculine and feminine for the
contrasted expression that analogous characters find in
the two sexes.

We cannot here do more than indicate the nature of
the evidence in support of the view that a deep, initial,
constitutional difference expresses itself primarily in what
we call maleness or femaleness, and is also decisive, late
or early, directly or indirectly, in determining whether
detailed characters will find a masculine or a feminine
expression. One egg becomes a cock, another egg a hen ;
but no microscopic differences are detectable ; and no
one yet knows what gives the egg a bias towards
maleness or femaleness. In the higher animals at least
the divergence is initial, and in a short time it finds
visible expression. The developing creature gets on to
definitely male or female lines, and the getting on to

138 THE BIOLOGY OF THE SEASONS

male or female lines of development determines sooner
or later, whether the detailed characters take a masculine
or a feminine expression. In some cases, probably, the
initial constitutional difference is itself continued on in
the building up of every part, deciding, as it were, at
point after point, whether the hereditary characters
will express themselves in the masculine or in the
feminine mode. In other cases, certainly, it is the
saturating influence of the early established maleness or
femaleness that determines the masculine or feminine
development of detailed parts, and of habits as well as
structure.

What is the nature of the evidence that might be adduced
to illustrate the saturating influence of the primary male-
ness or femaleness, as the case may be? It is indirect
rather than demonstrative. The sex-dimorphism is per-
vasive, it goes through and through. As Havelock Ellis
says : "A man is a man to his very thumbs, and a woman
a woman to her little toes." The difference can be read
in the blood — so safe and subtle an index to what goes on
throughout the body. The difference can be read thrpugh-
out life — it is seen, for instance, in the baby boy and baby
girl, it is expressed in old age. It is seen even in the
different ways in which the two sexes take the same disease.

Of more technical evidence we give only one illustration.
A spae'd pullet may acquire not only the outward struc-
tural features of the opposite sex — cock's comb, wattles,
long hackle and tail feathers, rapidly developing spurs,
carriage, etc., but the behaviour as well, and the pugnacious
disposition !

It is very important, we think, to realise that masculinity
and femininity differ greatly in their accentuation. There
is no such contrast in the sexes of starfish, but it is
obtrusive in turkeys. And just as there are individual

COURTSHIP OF BIRDS 139

organisms in which the masculinity or femininity is below
par when compared with what is normal for the race in
question, so there are species in which the males are
relatively feminine and the females relatively masculine,
judging by what is seen in related species.

In the majority of birds which show sex-dimorphism the
males are distinctly the handsomer and more decorative.
They are keyed to a different pitch of artistic excellence.
Not that we would disparage any female bird; we only
mean that they are on another line. The males are more
luxuriant, exuberant, and elaborate. A cock chaffinch is
one masterpiece, the hen chaffinch is another.

Some of the exceptions are interesting, but difficult to
understand. In the Hemipods, or Bustard-quails, small
quail-like birds about the size of sparrows which inhabit
Africa, India, China, Burmah, Malay, and Australia, the
female is usually more brightly coloured than the male, and
also larger. " The male is a very plain-plumaged little
fellow, but the female towers above him in size, and has often
a black throat or a rufous collar as a distinguishing char-
acter." The apparently older species have the sexes alike,
so in this case it seems that the evolution of decorativeness
has been on the female side. Now it is very interesting
to notice that in these bustard-quails, in which the females
are the larger and handsomer, only the females call and
only the females fight. The males sit upon the eggs,
while the females roam about, "calling and fighting,
without any care for their obedient mates ; the males, and
the males only, tend the young, and are to be flushed along
with the brood." " After having deposited her three or
four eggs in an apology for a nest, the female leaves the
incubation and rearing of the young to be performed by
her husband, weak little man that he is, while she roams
about, seeking for some equally strong-minded lady to fight

140 THE BIOLOGY OF THE SEASONS

with." The study of these exceptional cases is very interesting
in connection with the theory of sex. Most snipes and sand-
pipers, Bowdler Sharpe notes, show a superiority in the
female sex, but usually in size alone. In the African and
Indian forms of Painted Snipe (Rostratula) the females are
brighter as well as larger. Among birds of prey the female is
often the larger and more powerful bird, but there is little
decorative difference.

One of the most striking of the exceptional cases is the
Red-necked Phalarope (Phalarope hyperboreus) , a graceful
fairy-like bird that breeds on the Arctic shore. The female
is a perfect female, but she is very masculine in several
ways, and is much more richly coloured than her mate.
The male is a perfect male, but he is very feminine
in some of his ways. We quote an account of their
behaviour.

Mr. E. W. Nelson writes: — "The dull-coloured male
moves about the pool apparently heedless of the surrounding
females. Such stoical indifference usually appears too much
for the feelings of some of the fair ones to bear. A female coyly
glides close to him, and bows her head in pretty submissive-
ness, but he turns away, pecks at a bit of food, and moves off ;
she follows, and he quickens his speed, but in vain ; he is
her choice, and she proudly arches her neck, and in many
circles passes and repasses close before the harassed bachelor.
He turns his breast first to one side, then to the other, as
though to escape, but there is his gentle wooer ever pressing
her suit before him. Frequently he takes flight to another
part of the pool, all to no purpose. If, with affected in-
difference, he tries to feed, she swims along side by side,
almost touching him, and at intervals rises on wing above
him, and, poised a foot or two over his back, makes a half-
dozen quick, sharp wing-strokes, producing a series of sharp,
whistling noises in rapid succession. In the course of time,

COURTSHIP OF BIRDS 141

it is said, water will wear the hardest rock, and it is
certain that time and importunity have their full effect upon
the male Phalarope, and soon all are comfortably married.
The captive male is introduced to new duties, and spends
half his time on the eggs, while the female keeps about the
pool close by."

MODES OF COURTSHIP

Let us select a few illustrations of different modes of
courtship among birds. Perhaps the first place must be
given to song, but this raises so many questions that it must
be dealt with separately. It must suffice here to refer to
its variety, and one of Brehm's sentences will serve.
" Dominated by love, the jay sings, whistles, and murmurs,
the magpie chatters, the croaking raven transforms his
rough sounds into gentle, soft notes, the usually silent grebe
lets its voice be heard, the diver sings its wild yet tuneful
ocean-song, the bittern dips its bill under water that the
only cry at its command may become a dull, far-sounding
booming." And what is one to say of the nightingale, the
mavis, the blackbird, the lark, the bullfinch, and so through
the long list of the Spring orchestra ? In some cases there
is a certain degree of instrumental music, for it has been
shown that the drumming or bleating of the snipe is due to
the bird's rapid passage through the air with the outer tail-
feathers held very tensely.

Secondly, there is all the glamour of graceful movement.
Birds of prey ascend to giddy heights, let themselves go,
almost touch earth, and are up again— circling, soaring,
hovering. The flight of the eagle-like bateleur of the
interior of Africa is marvellous at all times, but at the
pairing time it becomes " an incomparable mountebank

142 THE BIOLOGY OF THE SEASONS

performance in the air, a bewildering acrobatic display,
which seems to unite in itself all the arts of flight practised
by the other birds of prey." So it is with hundreds of
birds : emotion finds expression in motion ; swallow and
lark, dove and pipit, bee-eater and bunting — all have their
wonderful aerial displays.

Some that have no display of flying powers show off on
foot. Cocks strut, turkeys dance, cranes pirouette to the
verge of exhaustion, and even the solemn stork has its
minuet. The capercaillie and the black grouse, the pheasant
and the peacock, are among the famous dancers. Even the
phlegmatic albatross indulges in antics, and the tragopan
goes in for the most extraordinary posturing and posing.

A third aspect of the courting is seen in the combats of
rival males. It is an unforgettable experience to get up
before dawn in the Spring, to creep quietly up the hillside
and hide in a sheep-fold, thence to spy on the " lek " of the
polygamous Black Grouse. The cocks strut and fight on
the level sward near by ; the hens stand looking on, like the
dames at a tournament. The cock utters a peculiar in-
describable note, he spreads and depresses his highly
decorative tail, and indulges in extraordinary antics, often
ending with an excited charge on his rivals. When the
spectacle is at its height and the rising sun strikes the
combatants, it is difficult to believe that we are looking
at the familiar Black Grouse, so remarkable is the trans-
figuration. In the end the most successful cock flies off
with a following of fascinated hens.

There are hundreds of other cases, though none more
picturesque, of combat and parade. Self-assertiveness runs
riot. Love flames out luridly into jealousy. Every one
will be cock of the walk, and hence the fray. The biological
interest of a cock-fight is in its illustration of masculine
self-assertiveness becoming almost maniacal.

COURTSHIP OF BIRDS 143

Capercaillies fight till the snow is sometimes red with their
blood, and their tournament is associated with a not less
excited parade. The variable ruffs, which used to breed
abundantly in the marshy parts of England, but are now
little more than non-nesting visitors, illustrate combative-
ness carried almost to a pitch of absurdity. At the pairing
time they assemble in companies to joust, and they some-
times fight almost the whole day. In spite of all the fuss
and flurry, however, the exuberant combat ends, like many a
duel, without the rivals doing one another much harm.

In many cases it is far otherwise. The little swifts and
the great eagles sometimes fight to the death, and the same
may be true of ostriches and swans, storks and chaffinches,
and many other birds. The spur- winged plovers and spur-
winged geese are savage fighters. Weismann and Bordage
have called attention to the very interesting biological fact
that in some habitual fighters, like storks and game-cocks,
there is a remarkable regenerative capacity in the bill.
Large pieces of the bone as well as of the horn sheath may
be regrown after injury — a very unusual circumstance, for
in creatures high up in the scale of being the " regenerative
capacity " is usually very slight.

We quote a paragraph from A. E. Brehm to illustrate
further the wealth of variety in " courtship."

" The means by which a male bird declares his love and
conducts his courtship are very various, but, naturally, they
always accord with his most prominent gifts. One woos
with his song, another with his wings, this one with his bill,
and that with his foot ; one displays all the magnificence of
his plumage, another some special decoration, and a third
some otherwise unused accomplishment. Serious birds
indulge in play and joke and dignified pranks, silent ones
chatter, quiet ones become restless, gentle ones combative,
timid ones bold, cautious ones careless ; in short, all show

144 THE BIOLOGY OF THE SEASONS

themselves in an unwonted light. Their whole nature
appears changed, for all their movements are more active,
more excited than usual, and their conduct differs from their
ordinary behaviour in every respect ; they are possessed by
an intoxication which increases the elasticity of their nature
to such a degree that no flagging is ever perceptible. They
deprive themselves of sleep, or reduce it to a minimum with-
out weariness, and while awake they exert all their powers to
the utmost without fatigue."

It is all like a prototype and at the same time a caricature
of human wooing.

THEORY OF PREFERENTIAL MATING

Darwin believed that the female birds exercised a real
choice, yielding themselves to those cocks that pleased them
most. He also believed that the choice was definitely based
upon particular excellences of the chosen mates — fineness of
song, exuberance of plumage, agility in flight, winsomeness of
dance, or impressiveness in parade. He gave the hen-birds
credit for aesthetic preferences, and his general theory was
that by persistently selecting the males who varied in the
direction of finer song and brighter plumage, they had gradu-
ally evolved these qualities to a high pitch of perfection.
" The females," he said, " have, by a long selection of the
more attractive males, added to their beauty and other
attractive qualities. If man can in a short time give
elegant carriage and beauty to his bantams, according to
his standard of beauty, I can see no reason to doubt that
female birds, by selecting during thousands of generations
the most melodious or beautiful males, according to their
standard of beauty, might produce a marked effect." In
short, constitutional variations are common, and a variation
very advantageous to its possessor in courtship runs a fair

COURTSHIP OF BIRDS 145

chance of being established and of being perfected by the
success it entails. Sexual Selection is thus only a special
case of Natural Selection, with this difference, that the female
bird takes the place of the general environment in picking
and choosing what is fit, or in leaving out what is relatively
unfit.

Darwin's illustrious collaborateur, Alfred Russel Wallace,
has taken a different view of the facts. Attaching little
importance to the alleged Sexual Selection, he interprets
the sex dimorphism in terms of Natural Selection. Con-
spicuousness during incubation is dangerous. The more
conspicuous females are picked off the nest by hawks, foxes,
and the like, and hence only sober-coloured females remain.
According to Darwin, the gayness of male birds is due to
Sexual Selection on the part of the females ; according to
Wallace, the plainness of the female birds is due to Natural
Selection, which has eliminated those that persisted to the
death in their gay plumage. Darwin starts from uniform
sexes, and accounts for the gorgeous males by Sexual Selec-
tion ; Wallace starts from uniform sexes, and accounts for
the sober-coloured females by Natural Selection. In 1773,
the Hon. Daines Barrington, a naturalist still remembered as
the correspondent of Gilbert White, suggested that singing-
birds were small and the hen-birds mute for safety's sake.
This is in principle the same idea as that which Wallace
has elaborated.

It is quite possible that there is truth on both sides, for
Sexual Selection might in some cases act as an accelerant of
the evolution of bright plumage, while Natural Selection
might in other cases have a retarding influence when
conspicuousness was dangerous. The difficulty is to get at
the facts. We have not sufficient data to answer the crucial
question whether a considerable number of males are left out
in the cold unmated, and, if so, whether they are appreciably

146 THE BIOLOGY OF THE SEASONS

inferior in attractiveness or in stimulating power. If this is
not the case, the process of Sexual Selection does not work.

It seems very important that we should get to know more
in regard to the correlation of the masculine or the feminine
characters. There is a growing body of evidence to show
that the secondary differences between males and females
hang together physiologically, and that a condition of their
development in the individual is an internal liberating
stimulus from the essential reproductive organs. The
secondary sex peculiarities, which we may sum up as mascu-
linity or femininity, are the manifold outcrops of the deep
primary constitutional difference which leads to maleness or
to femaleness, which makes of one animal an egg-producer
and of another a sperm-producer. A study of the hereditary
relation throughout the world of organisms leads to the idea
that every germ has a dual inheritance of masculine and of
feminine characteristics. One or other of these will find
expression in development, according as the germ develops
towards maleness or femaleness. What determines the sex
is a still more difficult question.

Another useful idea has become clearer of late. It is now
generally believed that what the female chooses — if she
chooses — is not so much slight improvements in chirping or
song, slight excellences in colour or scent, but rather the
tout-ensemble of that male who most excites her sexual
interest.

As Weismann says : " Even though we certainly cannot
assume that the females exercise a conscious choice of the
handsomest male, and deliberate, like judges in a Court of
Justice, over the perfections of their wooers, we have no
reason to doubt that distinctive forms (decorative feathers
and colours) have a particularly exciting effect upon the
female, just as certain odours have among animals of so
many different groups, including the butterflies,"

COURTSHIP OF BIRDS 147

Though Darwin sometimes seems to credit the female
with no small degree of aesthetic fastidiousness, he also
states that " it is not probable that she consciously deliber-
ates ; but she is most excited or attracted by the most
beautiful, or melodious, or gallant males."

Lloyd Morgan puts the modern view tersely when he
says : " The most vigorous, defiant, and mettlesome male
is preferred, just because he alone affords a contributory
stimulation adequate to evoke the pairing impulse, with its
attendant emotional tone."

THE SONG OF BIRDS

IT is interesting to remember, when all the land is full of
song, that for many millions of years there was no living
voice upon the earth. Living creatures in abundance, but
all voiceless — such was the state of things until the time of
the Coal Measures, when amphibians appeared, presumably
with vocal cords as frogs and toads have to-day. It is true
that long before that there were insects, some of which were
perhaps able to chirp and hum as crickets and bees do now,
but this is rather instrumental than vocal sound-production.
In any case, apart from insects, there was for millions of
years no sound to break the silence of Nature — save the
inanimate noises of the waves and the cataract, the thunder
and the wind.

The invention of speech seems to have been due to the
amphibians, but they did not make much of it, and few of
their successors, the reptiles, made more. The snakes, for
instance, have no word but a hiss, and most of the reptiles
make no sound at all. Among birds, however, as every one
knows, vocal expression attains to a remarkable degree of
evolution, surpassed by man only, who has informed it with
reason. To keep our ideas clear, it must be recognised that
many birds and mammals have definite words, indicative of
particular things or expressive of definite emotions ; but song
and language mean something more. In language, of which
man seems to have a monopoly, there must be, if it is worthy
of the name, the expression of a judgment — a sentence,
however simple. In song there is rhythmic, modulated

THE SONG OF BIRDS 149

reiteration, whose significance is emotional, not informative.
It is idle, indeed, to pretend that hard and fast definitions
can be given — that is a pre-Darwinian demand — for there
are many approximations to song whose inclusion or ex-
clusion within the rubric must remain a matter of opinion.
The long-drawn-out, modulated pairing-call of many of the
waders, such as the redshank, is on the border-line, and
there are many who would call the reiterated call of the
cuckoo a stammering song of the simplest sort.

Professor Alfred Newton writes in this connection :
" It is necessary in a scientific spirit to regard every sound
made by a bird under the all-powerful influence of love or
lust as a ' Song.' It seems impossible to draw any but
an arbitrary line between the deep booming of the emeu,
the harsh cry of the guillemot (which, proceeding from
a thousand throats, strikes the distant ear in a confused
murmur like the roar of a tumultuous crowd), the plaintive
wail of the lapwing, the melodious whistle of the widgeon,
' the cock's shrill clarion/ the cuckoo's ' wandering voice/
the scream of the eagle, the hoot of the owl, the solemn chime
of the bellbird, the whip-cracking of the manakin, the
chaffinch's joyous burst, or the hoarse croak of the raven,
on the one hand, and the bleating of the snipe or the drum-
ming of the ruffed grouse, on the other. Innumerable
are the forms which such utterances take." It seems to
us, however, that, while there are no hard and fast lines, it
is possible and useful to distinguish between a simple love-
call and a modulated, reiterated " song." That none of
them are " songs " in the strict musical sense is admitted
on all hands.

The true singing-birds belong to the huge order of
Perchers or Passerines, which includes over six thousand
species, and has a practically world-wide representation.
But it is especially in the North Temperate region that song

150 THE BIOLOGY OF THE SEASONS

finds its highest expression, and perhaps there is no region
so highly favoured as Middle Europe, with its nightingale
and bullfinch, its blackbird and thrush, its lark and wren.
North America is not far behind with its bobolink and blue-
bird. It must be admitted that there are good singers in
many parts of the tropics, but they do not attain the domin-
ance characteristic of those in the North, and their songs
are apt to be drowned in the shrill screams of their neigh-
bours. In some warm countries, such as Brazil, the evolu-
tion of bird-song seems to have lagged far behind the
evolution of gorgeous plumage — one of the general facts
which suggest the familiar interpretation of song as a
factor in preferential mating.

In mammals, the seat of the voice is in the larynx, at
the top of the windpipe ; in birds, the vocal cords are not
in the larynx, but in a special song-box or syrinx at the
foot of the windpipe, where it divides into the two bronchial
tubes. Let us consider the mechanism very briefly. Three
parts have to be distinguished. There is the framework
of bone, consisting of several pieces, more or less movable
in relation to one another. There is the external muscula-
ture, moving the parts of the framework and controlled by
a rather complex innervation (implicating the twelfth
cranial nerve, the first cervical from the spinal cord, and
the sympathetic system in the neck). Thirdly, there are
vibrating membranes and elastic folds, which are kept in
varied degrees of tension by the action of the muscles,
so that various notes are produced by the air driven out
from the lungs.

It is of interest to note that the voice-box is most com-
plex in Passerine birds, and that within the wide limits
of this order there are many grades of differentiation,
especially in the masculature. Even among the true
songsters (the Passeres 0 seines) there are many grades of

THE SONG OF BIRDS 151

complexity, but Professor Valentin Hacker,1 who has given
special attention to the subject, points out that it is not
possible to establish a close parallelism between the com-
plexity of the muscular apparatus and the melodiousness
of the song. Thus the syrinx-musculature of the thrushes
(Turdidse) is in some respects less evolved than that of the
crows (Corvidae). As Hacker says, much must depend
on the differences in mental aptitude, temperament, and
musical taste in the various types.

It is well known that the males are almost always better
singers than their mates. Indeed, some females do not sing
at all. Hacker's comparison of the vocal mechanism in
the two sexes leads him to the general conclusion that
the female syrinx is marked by smaller size, weaker mus-
culature, a more primitive skeletal architecture, and less
evolved vocal cords. It remains at a slightly lower grade
of evolution. But although the structural differences may
account for differences in the strength and volume of the
voice, they do not explain the not infrequent difference in
the actual character of the song. This must depend on
mental differences in the two sexes.

For a few birds, such as the lapwing, it has been proved
that the capacity for uttering the characteristic call is
inborn. It depends in part on the particular peculiarities
of the vocal mechanism and in part on cerebral endow-
ments. Professor Hacker points out that birds belonging
to the same genus, but to different species, have often
certain combinations of notes in common, and he refers
also to the fact that a young blackbird in his first year
will sing a generalised thrush-song, which is not nearly
such a fine thing as a blackbird's. It is much to be
desired that careful experiments should be made to give
us more precise information as to what a bird can or

1 Der Getting der Vogel, Jena, 1900, p. 19.

152 THE BIOLOGY OF THE SEASONS

cannot do in the way of song when it is isolated from
its kin.

Although there is considerable uncertainty, it seems as
if the general character of the voice and of the call was
hereditarily determined, while the actual melody is acquired
by education. Imitation plays an all-important part,
and thus much depends on those who serve as models.
" In places where nightingales enjoy protection from cats
and other persecutors, there are naturally some very old
birds, who improve their melodies from year to year, both
as regards purity and strength of notes, and thus become
more and more efficient teachers of youth. In such cir-
cumstances the nightingale's song acquires a fineness and
gradually increasing perfection, while in other districts,
where the birds never live long, the general level of musical
culture is low."

Indirect evidence of the importance of imitation is
afforded by the well-known fact that many birds readily
pick up snatches of song from other birds, stealing one
another's music. According to Witchell, skylarks re-
produce the cries or songs of yellow bunting, tree-pipit,
swallow, blackbird, martin, house-sparrow, chaffinch, pee-
wit, wagtail, hedge-accentor, and so on ; but when he goes
on to include the " sheep's bleat," we must confess to a
strain on our faith. He says, however : " The * sheep's
bleat ' above mentioned is difficult to identify in so musical
a voice as that of the skylark ; it is a short but distinct
sound, only to be described in the word baa"

Another fact of fundamental importance in regard to
bird-song is its primary connection with mating. It has
its roots in love-calls uttered by the excited male, and
producing excitement in the coy female. We must return
to the theory, but it is important first to note the fact that
song wanes away or abruptly stops as the pairing season

DIPPER ON A
(VI)

STREAM

THE SONG OF BIRDS 153

passes. " Almost coinstantaneously with the hatching of the
nightingale's brood, the song of the sire is hushed, and the
notes to which we have for weeks hearkened with rapt
admiration are changed to a guttural croak, expressive of
alarm and anxiety, inspiring a sentiment of the most
opposite character. No greater contrast can be imagined,
and no instance can be cited which more completely points
out the purpose which song fulfils in the economy of the
bird ; for if the nightingale's nest at this early time be
destroyed or its contents removed, the cock speedily
recovers his voice, and his favourite haunts again resound
to his bewitching strains. For them his mate is content
again to undergo the wearisome round of nest-building
and incubation. But should some days elapse before
disaster befalls their callow care, his constitution under-
goes a change, and no second attempt to rear a family is
made." l

As to the theoretical interpretation of bird-song, various
suggestions have been made. The Darwinian view regards
the male bird's power of song as an asset in the business of
courtship. The best singers were most successful in
wooing, and thus the musical talent was improved genera-
tion after generation. It is not necessary to suppose that
improvement always implied a structural change in the
song-box mechanism ; for, while that doubtless went on,
what was mostly selected was probably a certain type of
constitution — an attractive fellow, in short. Nor is it
necessary to suppose that the coy females sit listening with
attentive and critical ear, like judges in a singing com-
petition. As we have already seen, the probability is that
a certain tout-ensemble of emotional display on the part
of the male, in which the song is one item, pulls the trigger
of an analogous emotional excitement in the female. There

1 Newton's Dictionary of Birds.

154 THE BIOLOGY OF THE SEASONS

is a tendency to transfer our analytic scientific way of
looking at things to birds and beasts that probably leads
us into many mistakes. It is extremely improbable that
any female bird accepts a suitor on account of his musical
or quasi-musical talents.

Another view, which has the great name of Wallace
behind it, interprets the love-call as a means of recognition
between related forms, and as a signal which brings sparsely
scattered birds together. It is highly probable that
singing sometimes has these secondary advantages, but the
frequent elaborateness of the song seems to require some
other interpretation.

Wallace also suggested that singing was a pleasure,
and probably helped as a safety-valve for superfluous
nervous energy, just as a dance does. Herbert Spencer
elaborated the same view that the song is not in any sense
a kind of courtship, but simply expressed an overflow of
nervous energy. The dog wags its tail when pleasurably
excited, the bird works the muscles of its syrinx. This
theory is too simple to be the whole truth, but it lays
emphasis on a very important fact — the close association
between emotion and muscular movements.

There seems much to be said for the thesis well worked
out by Professor Groos in his Play of Animals — that
instinctive coyness has been evolved as a feminine character-
istic of great importance as " the most efficient means of
preventing the too early and too frequent yielding to sexual
impulse. A high degree of excitement is necessary for both,
but the female has an instinctive impulse to prevent the
male's approach, which can only be overcome by persistent
pursuit and the exercise of all his arts." Song is one of
these arts by which the male stimulates his desired mate to
passion.

Nor is the female's response of less importance in

THE SONG OF BIRDS 155

intensifying the male's excitement, especially in cases where
what looks like coquetry is exhibited. Thus, as Groos
says, " the female cuckoo answers the call of her mate
with an alluring laugh that excites him to the utmost,
but it is long before she gives herself up to him. A mad
chase through tree-tops ensues, during which she con-
stantly incites him with that mocking call, till the poor
fellow is fairly driven crazy. The female kingfisher often
torments her devoted lover for half a day, coming and calling
him, and then taking to flight. But she never lets him out
of her sight the while, looking back as she flies and measuring
her speed, and wheeling back when he suddenly gives up
the pursuit."

The general conclusions of Professor Hacker's admirable
study of the song of birds may be briefly stated.

(1) Love-calls and song probably had their roots in
the simple recognition-call or characteristic signal of the
species. Gulls and guillemots, hawks and crows do not get
beyond this grade.

(2) The calls of the two sexes diverged and a certain
amount of specialisation appeared. Thus there came to
be special pairing-calls, serving not only for recognition,
but also for expressing and suggesting amatory excitement.
Cuckoos and woodpeckers illustrate this grade.

(3) As sex dimorphism became more accentuated — the
females becoming more passive and coy, the males more
active and insistent — the song acquired more and more
of its secondary significance as a suggestive excitant,
and (unconscious) Sexual Selection came to the aid of
Natural Selection. Thrush and nightingale are familiar
instances.

(4) Sometimes, however, the singing activity outlasts
the breeding or nuptial period. When it overflows into
other seasons it partakes of the nature of play, it acquires

156 THE BIOLOGY OF THE SEASONS

a third significance as an expression of a feeling of well-
being — a safety-valve for the joie de vivre. The yellow-
hammer, the water-ousel, and the robin may be men-
tioned as examples of birds that sing outside of the
nuptial season.

THE NATURAL HISTORY OF NESTS

NEST-MAKING is such a characteristic activity of
birds that we always think of " bird " and " nest "
together. But birds are by no means the only creatures
that build nests. The squirrel makes a big nest of moss,
leaves, and grass at a fork between two branches of a tree
or in a hollow of the stem. The sticklebacks glue together
the filaments of seaweed and make a serviceable nest,
where the eggs are laid and hatched. Many spiders make
true nests of silk, while others bind leaves together with
silken threads. The wasp's familiar construction is a house
as well as a nest. There are many other nest-makers,
yet our almost automatic association of " nest " and
" bird " is not without justification, since it is among
birds that nest-making reaches its greatest perfection,
variety, and beauty.

USES OF NESTS

The uses of nests are manifold. They are often adapted
to secure the safety of the eggs and young birds by being
inconspicuous or by being inaccessible. The period of
development and of helplessness lasts about a fortnight
in many finches, three weeks in the fowl, over a month in
petrels, towards six weeks in the swan, and over seven weeks
in the condor, and the risks of discovery are often great.
The nest means safety. Secondly, the eggs and the young
are cold-blooded — that is to say, they take on the

158 THE BIOLOGY OF THE SEASONS

ture of the surrounding world, and when they cool below
a point, which differs for different species, they cease to
develop and soon die. The nest often economises the animal
heat of the brooding bird, so that there is little waste.
Thus the accomplishment of the development within a
suitable time is secured. Mr. Pycraft starts the evolution
of nests with birds who gathered a small heap of grass and
sticks, and thus kept themselves and the eggs warm and dry
when the ground was damp. It is also evident that the
nest is convenient for feeding purposes — for the prolonged
gastric education on readily digestible food which many
young birds require. It is often a convenient temporary
prison for the nestlings, so that they are less liable to
imperil their lives by making premature excursions.
Sometimes the nest serves for a certain amount of home-
education. Furthermore, the nest is often a comfortable
and secure resting-place for the brooding bird. The breeding
period is a climax of activity ; it is soon to be followed by the
effort of migration ; the need for rest is obvious.

Dr. Alfred Russel Wallace has elaborated the theory, for
which there is much very interesting evidence, that when
both the cock- and hen-birds are of strikingly gay and
conspicuous colours, as in many kingfishers, the nest is such
that eggs and young and sitting birds are concealed from
view ; while, whenever the male is gay and conspicuous
and the nest is open so as to expose the sitting-bird to view,
the female is dull or obscure in her coloration. He shows
how this relation might come about in the course of Natural
Selection.

We usually associate a nest with - concealment or in-
accessibility, with some degree of privacy. But there are
familiar exceptions. A strong race, like that of the rooks,
can afford to indulge their social tendencies even in nesting,
and their conspicuous nests challenge attention, We find

THE NATURAL HISTORY OF NESTS 159

a contrast in the cranes, which feed together, play together,
and rest together — but nest separately. Sometimes the
gregariousness in nesting may be associated with the relative
rarity of suitable sites, as may be illustrated by our sand-
martins, or by the sociable grosbeaks, which join nest to
nest until the tree sometimes breaks down. An eloquent
testimony to the advantageous inaccessibility of certain
sites is afforded by the huge numbers of birds which some-
times possess them, as is well seen on " bird-bergs " like
Ailsa Crag and the Bass Rock, where gannets are so abun-
dant, or, in a different way, in the marshy ground, where
thousands of black-headed gulls often nest ,

A SERIES OF NESTS

Let us work up the series of nests from the simplest to
the most complex, following, almost necessarily, the article
" Nidification " in Newton's Dictionary of Birds. We
naturally begin with those birds in which the nest-building
— which comes as a serious practical task after the nuptial
song or the nuptial dance — is " scamped " or shirked.

The tern makes no more than a mere scraping on the
gravelly sand. It is the same with divers, thick-knees,
and sand-grouse. The stone-curlew and the night-jar
make no nest, nor any preparation of the soil, yet year after
year they select the same spot. In the case of guillemots
and razorbills, the egg is laid on a bare ledge of rock, and the
top-like shape is to some extent a safeguard against being
blown over or knocked over.

Many of the gulls, sandpipers, and plovers simply lay
their eggs in shallow hollows in the ground, adding a breast-
work of stems and leaves as incubation proceeds. The
ducks are mostly about the same level of nest-making, but
their depression is lined with down. The ringed plover

i6o THE BIOLOGY OF THE SEASONS

lays its eggs on the shingle, where they are so like rounded
pebbles that they are most effectively lost to ordinary
vision; and Professor Newton points out the interesting
fact that even when the bird lays its eggs on grassy
uplands, it still " paves the nest hollow with small stones."

One of the most charming of ground nests is that of the
eider-duck, where a thick quilt of down is accumulated
that can be drawn over the eggs when the mother-bird
goes down to the sea for food.

In not a few birds the only care is to bury the eggs — a
way of securing their safety that recalls suggestively the
habits of some reptiles, such as crocodiles, which are
historically antecedent to birds. The New Zealand kiwi
puts its single big egg in a hollow among the rhizomes of
the tree-fern ; the female ostrich lays her eggs in a hole
which the cock scrapes in the sand, and both birds share in
brooding. Some Mound-birds or Megapods bury their eggs
in the sand and leave them, while others heap a huge hot-
bed of dead leaves over the spot . Dr. Alfred Russel Wallace
has told us that many mother Megapods in Celebes come
from a distance of 10 to 15 miles to the vicinity of certain
warm springs, where they like to lay their eggs. A huge
mound is built, 5 to 6 yards high, 30 feet round, and many
mothers co-operate. After they have laid their eggs on
the mound they depart, leaving the eggs to hatch all un-
tended. If they stayed they would find difficulty in getting
enough to eat, for they feed upon fallen fruit ; and there is
no need for them to stay, since the young birds have a quite
unique adaptation — the quill feathers are so long to start
with that the chicks can fly away from the mound on the
very day of their birth.

Grebes and some rails collect pieces of water-plants and
" form of them a rude half-floating mass, which is piled on
some growing water-weed"; and while they do not shirk

tHE NATURAL HISTORY OF NESTS 161

incubation, they seem to trust partly to the heat of decom-
position. Here we have another illustration of the subtle
ways in which Bacteria are wrapped up in the bundle of
life. They bring about the decomposition which produces
heat, and this fosters the development of the unhatched
birds. The minions of decay and death are here utilised
in the production of life. There are many similar illustra-
tions of a sort of " inter-regnal co-operation," the best,
perhaps, being the internal partnership or symbiosis of
unicellular Algae with Radiolarians, with Sea-Anemones
and Corals, with simple " worms," and so on. Analogous,
though not " inter-regnal," is the intimate and most
profitable partnership between Bacteria-like microbes and
Leguminous plants, like Clover. This has led us far from
the grebe's nest, but the digression may be pardoned, since
there is no more fundamental conception in Natural History
than that of the Web of Life or the interlinkage of interests
in the economy of Nature.

We gradually work up from ground-nests to the earth-
mounds on which the flamingos sit, and on to rough
platforms like that of the wood-pigeon, through the floor
of which the eggs may be seen from below. Making a
fresh start, we reach the more elaborate stick nests of the
rooks and crows ; from these we pass to the heron's, where
a little bedding is added ; or to the magpie's, where the
erection is fenced round with thorns.

An offshoot in a different direction is represented by
birds that make burrows or tunnels or excavations of some
sort, getting as far as possible into private life. In its safe
retreat the sand-martin makes a scant bed of roots and
feathers collected from far and near. The kingfisher makes
a stranger one of undigested fish-bones. Sheldrakes and
puffins often utilise rabbit-holes. The woodpeckers carve
out holes in decaying trees ; the nuthatch plasters up part
ii

162 THE BIOLOGY OF THE SEASONS

of the doorway. The last instance suggests the case of the
hornbills, whose remarkable story has been so well told by
Mr. Pycraft and others. The female is weakly and moulting
at the breeding-time, and the male shuts her into a hole in
a tree-stem. The floor may have to be deepened, or it may
have to be raised with dry earth from the termitaries. The
doorway is built up, too, so that intruders are readily kept
out, while the hole is large enough to let the male bird's bill
in. It is on him that the labour devolves of finding food
for his mate, and afterwards for his family as well. He is
often worn thin with his other-regarding exertions, while
the female bird becomes fat. Sometimes, the story runs,
the male bird dies without having the reward of even seeing
his children.

Cases, like that of the hornbill, where there is some
building as an accessory to the nest, point the way to
definitely built nests, such as those of the swallow and the
house-martin. The swallow's is the more primitive of the
two — it is made of mud strengthened with pieces of straw ;
it is like " half a deep dish," open at the top ; it is built
against a rafter or a chimney ; it has a lining of small
feathers and soft grass. The house-martin's is also made of
mud, strengthened with pieces of straw or hair ; it is built
against the wall of a house or against a cliff ; it is like a
bowl in shape, with its open side against the surface selected,
and with a small entrance near the top ; there is a lining
of feathers, which the martin catches in the air, and pieces
of straw. It is difficult to understand how the bowl hangs
on to a smooth surface — even to a vertical pane of glass ;
it is interesting to watch the patient carefulness of the
builders, adding about half an inch every morning and no
more till next day, so that it hardens well, the whole edifice
taking about a fortnight.

A masterpiece along the line illustrated by swallow and

THE NATURAL HISTORY OF NESTS 163

martin is the nest of some of the South American oven-
birds (Furnarius) — for instance, of that species (F. rujus)
which is called the " hornero " or baker. The nest is about
the size of a child's head, and may weigh 8 to 9 Ib. ; it is built
in a conspicuous place — on a tree, or post, or house-roof.
It is made of mud and dung strengthened, as in the swallow
and martin, with some hair or dry grass, which is also used
as an internal lining. The walls are of almost brick-like
strength when well baked, and it is sometimes the work of
months to build them. The oven-bird's bill is quite small,
and it has to work slowly, pellet by pellet ; moreover,
when dry weather sets in, it is difficult to get material.
But the chief peculiarity of the nest is the presence of an
inner chamber ; there is an anteroom and a bedroom, as
Prof. Trail neatly puts it.

On a different line of evolution, though there is no lack
of connecting links, are the felt -work nests, cleverly made of
interwoven vegetable fibres and hair — in both cases a good
non-conducting material. Chaffinch and goldfinch make
open felt-work nests, which may be eked out with spiders1
webs and often beautifully disguised with moss and lichen.
Similar constructions, masterpieces of skill, are domed in the
wren and the bottle titmouse, slung like a hammock in the
gold-crest, suspended by a string in certain grossbeaks and
humming-birds. There seems to be no doubt that the nest is
sometimes balanced with lumps of earth — an extraordinary
device, when one comes to think of it.

Among these built nests there are endless refinements of
detail. The entrance may be narrowed ; the outside may
be masked ; the whole may be swung so loosely that no
snake could possibly enter ; the lining may be made like a
bed of down : thus MacGillivray counted 2379 feathers in
the nest of the long-tailed tit. In the nest of the common
thrush, which is plastered internally with rotten wood

164 THE BIOLOGY OF THE SEASONS

mixed with dung, or in the nest of the mistle-thrush, which
has a considerable foundation of mud, we have instances
of the numerous connecting types between hard-built and
felt-work nests . The tailor-birds make a thread of vegetable
fibre, and sew together the edges of a couple of leaves ; the
fantail warbler also uses a thread — knotted at the end — to
bind grass-stems into a canopy over its nest. Of certain
warblers (Aedon and Thamnobia) it is said that they in-
variably lay a piece of snake's slough in their nests, like the
horseshoe by the house-door.

The series of typical nests might be greatly prolonged,
but we must bring it to a close with a reference to what is
perhaps the most extraordinary of all nests — that of the
sea-swift (Collocalia). The bird occurs in great numbers
in Indian and Australian regions, and usually nests socially
in caves, both by the sea and among the mountains. The
peculiarity of the nest — the well-known " edible bird's-
nest " — is that it normally consists of the dried secretion
(largely mucin) of the salivary glands. When the first
nest has been gathered, the bird sometimes builds an
inferior type of nest, including a considerable quantity of
vegetable matter glued together with the hardened salivary
juice. It is worth recalling the fact that not a few of our
British birds moisten with their saliva the vegetable fibres
and the delicate twigs which they use for nest-making,
thereby rendering them more pliable. It seems likely that
the inferior nests of Collocalia, in which vegetable fibre
predominates, represent for this genus a primitive rather
than a degenerate type.

THE NATURE OF THE NEST is SPECIFIC

We have seen that there is a long inclined plane from no
nest at all to the most elaborate nest, but the important fact

THE NATURAL HISTORY OF NESTS 165

is that the character of the nest is distinctive of the species.
Each kind of bird keeps to its own kind of nest — with
relative constancy. In short, the nature of the nest is
specific, with a measure of variability such as we find in
structural specific characters. The blackbird is first
cousin of the thrush, but every country schoolboy knows
that the nests are very different, and so it is all round.
When birds build on an unusual site, or when they nest in
a locality where their favourite materials are scarce, the
nest may vary considerably from type, and we read every
year in the newspapers of extraordinary vagaries (doubtless
more extraordinary to us than to the bird !) as to site and
materials. Apart from cases of nests inside station-lamps
or letter-boxes, there is considerable variability in the open
country. The Golden Eagle may use a ledge of rock, a
forest tree, or even the thick herbage ; the heron may rest
on a lofty tree, in a sea-bank, or in the open fen. It is
well known that a bird may lazily use another bird's nest,
and the habit has become normal in the European cuckoo.
The familiar sight of sparrows evicting swallows is sugges-
tive of the possible origin of a regularly parasitic habit — if
it could be regularised so as not to kill off the swallows !

THE FASHIONING OF THE NEST

It is possible nowadays to see in a cinematograph series
the whole business of nest-building — in a few cases of more or
less exposed nests. In regard to many more difficult cases,
persistent and patient observation — with the help of a
good field-glass — has enriched science with detailed descrip-
tions of one of the most interesting of animal activities.
It is difficult, however, to venture on any general
statements. The hens do most of the work of building the
cradle, but the cocks often help. As birds are practically

166 THE BIOLOGY OF THE SEASONS

handless — a sacrifice involved in the turning of arms into
wings — the bulk of the work is done with the bill and with
the feet, and the body is used to mould the framework, the
bird turning round and round inside the growing nest, making
it fitter at every turn with a poke of the bill and a thrust of
the foot. The busy bird suggests at times an extremely
energetic and somewhat fussy sculptor, working on his clay,
dabbing here and dabbing there, smoothing down and
ruffling up, and pausing every now and then to look at it
with critical appreciation. But when we look at the finished
product, such as the nest of a chaffinch, we must stand
amazed at the artistic achievement. It may be safely said
that the wonder grows upon us as we probe deeper into the
details of the nest.

SUBJECTIVE ASPECT

It is not difficult to observe how a bird uses its bill and
feet in fashioning the nest, but it is very difficult to get near
the inward spirit. The only course is to select the interpre-
tation that fits the facts best and makes fewest assumptions.
Is the art of nest-building instinctive ? That is to say, has
the bird an inborn power of fashioning a nest of a par-
ticular type without education or experience? Does it
require only what the Germans call an Auslosungsreiz
— a liberating stimulus — to pull the trigger of an innate
capacity ? And is this innate capacity the outcome of
an age-long selection which favoured those individuals
whose brain varied in the direction of useful constructive
art?

In support of this way of looking at the nest, there are a
few observations, e.g. that canaries that had never seen more
than a shop-made felt nest have been known to make an
effective nest of moss and hair ; or that a greenfinch,
incubated by a canary in a canary's nest, made, in the course

THE NATURAL HISTORY OF NESTS 167

of time, a true greenfinch nest of fibrous roots, moss, wool,
and horse-hair.

There is also an indirect argument in support of the view
that the fashioning of the nest is instinctive ; it is based on
the fact that the nature of the nest is usually specific. That
each bird keeps, as a rule, to its own type of nest does not
exactly prove that the whole business is instinctive ; but it
points in that direction, and it seems to us to rule out the
view that each nest is the expression of independent and un-
prejudiced artistic skill. It must be noted, however, that so
great an authority as Dr. Alfred Russel Wallace refuses
altogether to admit this argument. According to his view,
" each species uses the materials it can most readily obtain,
and builds in situations most congenial to its habits. . . .
The materials of birds' nests, like those used by savage man
for his house, are, then, those which come first to hand ; and
it certainly requires no more special instinct to select them
in one case than in the other." Similarly, he interprets the
characteristic architecture of the nest in terms of the general
habits of the species, the nature of the tools (bill and feet)
they have to work with, and the material they can most
easily obtain.

The non-instinctive theory, supported by Dr. Wallace,
lays emphasis on imitation and tradition. While a bird may
inherit an indefinite tendency to build a nest at the proper
time, the manner of its building depends on the extra-
organic tradition of the species. From generation to genera-
tion there is a " tradition " registered in the nest itself, which
is, in a sense, a " permanent product," and including all the
possibilities of imitation and suggestion from previous and
contemporary nest-builders. Even with human mothers,
where there is intelligent awareness rather than vague
instinctive prevision, how important is the social tradition
of what is fit and proper in the way of provision for the future

168 THE BIOLOGY OF THE SEASONS

child — a tradition operative in various ways — through
memory of what has been seen, through models to imitate,
and through permanent registration in books. Similarly,
there may be a distantly analogous tradition among wrens
and weaver-birds, thrushes and chaffinches, as to the fit and
proper nest to build. In support of this view, it is said, for
instance, that chaffinches transported to New Zealand no
longer build the typical chaffinch nest. They have got
beyond the tradition.

Against Wallace's theory is the obvious fact that the
young birds do not see the building of the nest in which they
are hatched, but he supposes it to be sufficient that the young
birds before they leave the nest have " ample opportunities
of observing its form, its size, its position, the materials
of which it is constructed, and the manner in which those
materials are arranged." It may also be that the young
birds follow the lead of their seniors in nest-building the
following year, learning as they go along, and in some cases
they may not be ready for nest-building the first Spring, and
thus have further opportunities for watching what the older
birds do. But the fact is that careful experiments are
necessary before we can decide between the view that nest-
building is in the main an instinctive activity and Wallace's
conclusion that he cannot find in nest-building " a particle
of evidence to show the existence of anything beyond those
lower reasoning and imitative powers which animals are
universally admitted to possess."

Mr. Pycraft, on the other hand, writes : " In spite of the
dogmatic assertions of this eminent naturalist, there is
absolutely not only no evidence in support of his contention
that birds build by imitation, but all the known facts are
directly against him." . . . Thus " wild birds taken from
the nest before they can see, and kept in captivity under
suitable conditions, will, at the appropriate time, build a

THE NATURAL HISTORY OF NESTS 169

nest typical of their species." It is by an extension of
experiments of this sort that the interpretation of the sub-
jective aspect of nest -building will be raised above the level
of opinion.

It may be possible to combine the two theories in the
view that the fashioning of the nest is in greater part
instinctive, yet in some measure traditional, while we can
hardly doubt there is often a spice of personal intelligence
on the artist's part — especially evident when quite novel
sites and materials have to be dealt with. After quoting
some evidence, Professor Lloyd Morgan concludes, in his
Habit and Instinct, that " some birds build their nests true
to type, without opportunities or with but the slenderest
opportunities of imitation or instruction. It appears to me
that the evidence before us justifies the conclusion that nest-
building in definite ways is an instinctive activity ; but that
it is modifiable by individual experience."

BIRDS' EGGS

A LTHOUGH the eggs of birds are by no means very
/~~\ typical eggs, they are always those which the
word first suggests, and they perhaps deserve the first
place in our consideration, for they are interesting above
all other eggs, as the enthusiasm of the " oologists "
amply testifies. " In enthusiastic zeal for the pro-
secution of their favouritive researches," Prof. Alfred
Newton writes, " they have never yielded to, if they
have not surpassed, any other class of naturalists. If a
storm-swept island, only to be reached at the risk of life,
heid out the hope of some oological novelty, there was the
egg-collector. Did another treasure demand his traversing
a burning desert or sojourning for several winters within
the wildest wastes of the Arctic Circle, he endured the
necessary hardships to accomplish his end, and the posses-
sion to him of an empty shell of carbonate of lime, stained
or not (as the case might be) by a secretion of the villous
membrane of the parent's uterus, was to him sufficient
reward/' Eggs can be studied scientifically like other
things, and Professor Newton goes the length of saying
that hardly any branch of the practical study of Natural
History brings the inquirer so closely into contact with many
of its secrets. It is true that collecting birds' eggs may be
no better, and is often much worse, than collecting postage
stamps ; but if one ponders over the eggs and their problems,
there is abundant opportunity for scientific work, and there

have been some notable results. Thus we must credit

170

BIRDS' EGGS 171

the students of birds' eggs with being the first to appreciate
the intimate relationship between gulls and plovers —
which was afterwards proved up to the hilt on anatomical
lines by Huxley and others.

What is roughly called the yolk of a bird's egg is the
true egg-cell, which has been enormously dilated by its
store of reserve material. A drop of genuine living-matter
lies like an inverted watch-glass on the top of the yolk,
and from this drop the whole of the embryo is formed,
the yolk being simply a nutritive legacy. All round the
yolk there is a delicate vitelline envelope, and outside this
lies the white of egg or albumin, secreted by the walls of
the oviduct, and also nutritive. Round about the white of
egg there is a delicate, tissue-paper-like double shell-mem-
brane, the two layers of which are separated at the broad
end of the shell to form an air-chamber. Outside the shell-
membrane is the porous shell, which is formed from the
walls of the oviduct. It is often stained with pigments,
and it consists mostly of carbonate of lime, with a small
proportion of carbonate of magnesia and phosphate of
lime and magnesia. Experiments have shown that a hen
can make a normal carbonate of lime shell, although
there is no carbonate, but only other salts of lime in its
food.

One of the first facts that strikes us in connection with
birds' eggs is that there are so few in a clutch, compared
with the number in lower animals. The wren may have
eight or nine eggs, the mallard a dozen, and the long-tailed
tit as many as twenty ; but these large numbers are quite
exceptional. Many birds, such as the golden eagle and the
black guillemot, usually lay only two ; while others, like the
common guillemot and the little auk, have come down to
one. There are two ways of looking at the smallness of
the family. On the one hand, birds are typically flying

172 THE BIOLOGY OF THE SEASONS

creatures, and this limits the number of relatively large
eggs that they can bear at a time. On the other hand,
the great care that birds take of their eggs and young
makes survival, in spite of the small family, more practicable.
And, again, it must be remembered that many birds are
taxed to the utmost in feeding their young brood, so that
in this way an indirect check would be put on large
clutches.

The size of the egg depends, as in most cases, on the
amount of nutritive material or yolk, not on the amount
of living matter that there is to start with. In general
it bears some relation to the size of the bird. Of European
birds, the swans have the largest eggs, and the golden-
crested wren the smallest. It is said that the egg of the
extinct Moa of New Zealand sometimes measured 9 in.
in breadth and 12 in. in length, while that of the extinct
^pyornis of Madagascar held over two gallons — some six
times as much as an ostrich's egg, or a hundred and fifty
times as much as a fowl's.

It cannot be said, however, that the size of the egg is
more than generally proportional to that of the parent ;
for, while the cuckoo is much larger than a lark, the eggs
of the two birds are about the same size ; and, while the
guillemot and the raven are about the same size, the eggs
the former are in volume about ten times larger than of
those of the latter. Hewitson pointed out that " the eggs
of all those birds which quit the nest soon after they are
hatched, and which are consequently more fully developed
at their birth, are very large." Professor Alfred Newton
adds that " the number of eggs to be covered at one time
seems also to have some relation to their size." He con-
trasts the snipe and the partridge : the former has four
eggs, the latter as many as twelve ; the eggs are equal in
size, and the chicks in both cases are able to run about as

BIRDS* EGGS 173

soon as they are released from the shell. The snipe, though
a much smaller bird, can afford to have eggs as large as
those of a partridge, because it has only four, which always
lie with their points almost meeting in the centre. We
believe, however, that some account must be taken of the
habits of the various birds, and that a highly nutritive
sluggish bird, not flying about much at the breeding season,
will naturally have relatively larger eggs than a bird of
sparser diet and more active habit.

Birds' eggs show considerable diversity in shape; for,
while the majority are oval, many are " pear-shaped," as
in guillemot and snipe, many are approximately spherical,
as in owls and kingfishers, those of the sand-grouse are
obtuse at both ends, and those of grebes biconical. Even
within the species or clutch there may be considerable
variability, and a collection of abnormal hens' eggs presents
a whimsical appearance. There is, however, a norm for
each type, both of shape and size, and it is interesting
to observe that after abnormalities " regulative changes "
bring subsequently laid eggs back to the normal — a
phenomenon that leads us to the very heart of vitality.

The problem of the immediate factors that determine
the shapes of the eggs of birds has been discussed in a
very interesting paper by Professor D'Arcy W. Thompson
(Nature, 4th June 1908, pp. 111-113). The egg, consisting
of a slightly extensible membrane filled with an incom-
pressible fluid, is subject to external pressure from the
radially contractile oviduct, and an equation for the shell
that is formed can be worked out. It is pointed out that,
from the nature and direction of the usual peristaltic wave
in the oviduct, the pressure will be greatest somewhere
behind the middle of the egg ; in other words, the tube is
converted for the time being into a more conical form,
and the simple result follows that the anterior end

174 THE BIOLOGY OF THE SEASONS

of the egg becomes the broader and the posterior the
narrower.

But, while the primary reason why an egg has a
particular shape is doubtless to be found in the conditions
of pressure within the muscular oviduct, that is not incon-
sistent with finding that the shape is sometimes adaptive
to particular conditions in the life of the bird. Two
instances of this adaptiveness are well known. Eggs which
are markedly pear-shaped "are mostly those of birds which
invariably lay four in a nest ; and therein they lie with
their points almost meeting in the centre, and thus occupying
as little space as possible and more easily covered by the
brooding parent." But the guillemots and razor-bills
have also very markedly pear-shaped eggs, and the bird
usually lays only one or two. Darwin pointed out, however,
that this shape of egg was particularly well adapted to the
risks of the narrow rocky ledges on exposed cliffs, where the
eggs are laid without even an apology for a nest. If the
egg be jostled by a bird's foot or whirled by the wind, it
tends not to roll along, but to rotate on its short axis
without leaving the spot.

Eggs differ not a little in the texture of the shell. In
different families there is, often at least, a characteristic
shell-structure. Thus a cuckoo's egg can be recognised in
a clutch when it has the same colour as the eggs of the
foster-parent. There are said to be differences between
the egg-shells of the carrion crow (Corvus corone) and those
of the hooded crow (Corvus comix), which are two very
closely allied species, or, as some would say, colour-varieties
of one species. In some cases, it is said, the shell registers
hybridism — a very remarkable fact. It is another illustra-
tion of the great, though still vague, truth that the living
creature is a unity through and through, specific even in the
structure of the egg-shell within which it developed. For,

BIRDS' EGGS

although the shell is secreted by the walls of the oviduct,
it seems to be in some measure controlled by the life of the
giant-cell — the ovum — within.

It must be clearly understood that, if we compare a
hen's egg with frog's spawn, what we call " the yolk " is
equivalent to the dark-coloured egg-cell which lies within
the sphere of jelly ; the latter is equivalent to the white of
egg ; but the frog's egg has no hint of a shell !

The surface of the shell may be glossy or of very fine
grain, as in the kingfisher ; or opalescent, as in some
woodpeckers ; or burnished, as if glazed, as in the tinamou ;
or pitted, as in the emeu ; or greasy, as in ducks ; or
rough, with a chalky film, as in the gannet. In a few
cases the chalky layer hides a deeper layer with fine
colouring.

But the most striking feature of birds' eggs is their
diversity of coloration, which is often strikingly rich and
beautiful. Thanks to the spectroscopic work of the late
Dr. H. C. Sorby, who touched many departments of Natural
Science with a masterly hand, we know of seven well-
marked pigments in egg-shells. Six of these are allied
chemically to haemoglobin, the pigment of the blood ; the
seventh (lichenoxanthin) is common in plants, especially
in lichens, and may possibly be due in some curious way to
minute fungi in or on the egg-shell. The other pigments are
exuded into the oviduct as the eggs pass down, and there
is some reason for connecting their production with the
bursting of the eggs from the ovary.

In any case, minute drops of pigment are exuded from
the lining of the oviduct ; they adhere to and stain the egg-
shell, which is still soft. If the egg be at rest for the moment,
the pigment-drops are fixed as circular spots of colour.
But as the egg is usually rotating onwards down the
oviduct, the spots of pigment tend to become smeared

176 THE BIOLOGY OF THE SEASONS

splashes, or long streaks, or irregular blotches — often
conspicuous against a ground colour of white or of some
previously deposited pigment. This is only the A B C of
a difficult matter ; but with this simple fact clearly focussed
in the mind, it is very instructive to look over a collection
of eggs and interpret the precise well-fixed marks, the
clear-cut edges, the hair-lines, the spirals, the long-drawn-
out splashes, as indicative of the rest or the movement of
the egg during the period of painting. In many cases it
has obviously moved much before the paint was dry. In
this connection we must remember the general uniformity
of natural process. Given the same kind of bird, the same
size of egg, the same calibre of oviduct, the same pigments,
the same rate of egg-movement, and the coloration of
the egg will tend to be the same. And it is interesting to
know experimentally that abnormal conditions, such as
fright or captivity, may disturb the natural painting of
the egg-shell, or suppress it altogether. Thus we have seen,
for instance, a woodcock's clutch with pure white eggs-
most unprofitably conspicuous in the wood.

The next point of importance is that the coloration of
birds' eggs is variable, and sometimes very markedly so.
Notoriously variable are the eggs of the Black-Headed Gull
(Larus ridibundus) — from unspotted pale blue at one
extreme to very dark brown, with darker spots, at the
other. The eggs of the rook, the guillemot, and the cuckoo
are also good illustrations of variability. The bird cannot
alter the colour of the egg by willing it ; she is not influenced
by surrounding colours ; the eggs are only to a slight extent
modifiable by external influences. There is no doubt that
the variability in colouring is due to a peculiarity in the
constitution of the mother-bird. The important fact has
been noticed that, when a mother-bird has begun to lay eggs
of a peculiar coloration, she may continue to do so for

BIRDS' EGGS 177

years. The pleasant brown colour of the eggs of some
fowls is due to a variation which breeds true and does
not blend ; by taking certain well-known precautions in
breeding it can be, as it were, grafted on to a stock laying
white eggs.

We have described in a simple way the mechanism by
which birds' eggs are coloured ; we have seen that most
of the pigments are allied to the red pigment of the
blood ; we have noticed that in many cases birds have not
yet quite settled down to a stereotyped kind of egg-colora-
tion ; we must now ask whether the colouring has any
selective value, or, in other words, any vital significance.

In some cases, where the eggs are well hidden or are
almost quite safe, it is difficult to find any significance in
the colouring. It may express the unity of the organism,
but it seems to be useless in the present condition of the
species. Similarly, the colouring of deep-sea animals, or
the colouring of withered leaves, cannot be shown to have
any direct utility. Similarly, some of the internal organs
of animals have very fine colours, absolutely determined,
never haphazard, but yet valueless as regards optical
effect, because invisible.

On the other hand, it seems quite impossible to doubt
the occasionally great vital value of the coloration which
in other cases may be a negligible feature. We refer,
of course, to those cases where exposed eggs are incon-
spicuous because their coloration harmonises so well with
the surroundings. This is particularly striking in many
members of the Plover and Gull tribes, where it is almost
impossible to exaggerate the difficulty of finding the eggs
in their appropriate surroundings. This is a particularly
instructive case to think over, for one can understand that,
given an abundant crop of colour- variations and a severe
elimination-process, survival would be with the appropri-

178 THE BIOLOGY OF THE SEASONS

ately coloured eggs, or, in other words, with those birds
whose constitution turned out the appropriately coloured
eggs. This is not inconsistent with the view for which
there is something to be said that birds may to some
extent choose out spots which suit the colouring of their
eggs.

WITHIN THE EGG

A BIRD'S life begins when there comes about an intimate
and orderly union of the maternal and the paternal
inheritances — the result of which is a new creature, not free
to be or do anything it likes (a sort of freedom which has never
existed, and would not be worth much if it did), and yet not
fated to be a mere echo of its father or its mother, but with
some measure of originality, or individuality. It is a new
creature, in some ways quite unpredictable, though we may
be able to indicate beforehand some of the alternatives of
expectation. In this variability we have, in part, the
biological basis for the doctrine of personal freedom, which
tends to be dimmed by insistence on the inexorable continuity
which the hereditary relation also implies. The individual-
ised young creature, with a freedom of contingency, at least,
acts on and reacts to its nurture, until there is formed a sort
of personality, or character. This is a product of the
external as well as of the organic heritage — and it may lead
on to a truer freedom than that of mere contingency. Even
in the bird there is a self — it may be a very unique self
— with the power of being and doing differently from
its immediate ancestry. In so far as it avails itself of
its relative newness to respond or to fail to respond to
environmental nurture, there develops an individuality,
opposable to the trend of the natural inheritance, even
capable of approximating to the ethical idea of freedom.
The development of a bird is apparently a very smooth

nnd orderly process. There are no crises, no sharp turns, as

179

i8o THE BIOLOGY OF THE SEASONS

in the life-history of a frog or a butterfly. There is, indeed,
a very interesting " critical point/1 as it is called, when for
the first time the specific characteristics emerge. They have
always been there, of course, but have not hitherto found
more than generalised expression, as far as we can see. But
there is no crisis at that " critical point," so far as we know.
The process is smooth and orderly ; it is like the unfolding of
a bud, except that there are no visible preformed parts ; it is
like the working out of an idea in a master-mind who has no
hesitation or loose-ends or fluffiness in his concepts.

It may take a long time, comparatively speaking — six
weeks in the condor, three in the fowl, two in the finch — a
long time compared with the extreme rapidity with which the
complex architecture of many an insect is built up. And yet
what a short time, when we remember the thousands and
thousands of cell-divisions that have to occur, each as complex
a business as the crowning of a king ! What a short time,
when we remember that the developing embryo begins as a
single cell, with a nucleus half paternal, half maternal, andthat
it becomes within the shell a bird, which may be able to run
about whenever the shell is broken, which is in one family
(Mound-birds) able to fly when it is born. What a short time,
when we remember that the developing bird has to re-
capitulate in some measure the racial history of Vertebrates,
to climb up its own genealogical tree.

The stages of development are, in the case of a few birds,
such as hen, duck, and even kiwi, so well known from day
to day, that exact figures and models are obtainable. There is
no doubt whatever that some of the stages are only intelligible
when we look backwards as well as forwards. They have a
retrospective as well as a prospective significance ; they hint
at past history. Thus there are functionless gill-clefts which
point back to an extremely remote aquatic ancestry.

The luminous idea that development resumes evolution,

•>

WITHIN THE EGG 181

that ontogeny recapitulates phylogeny, that the developing
creature climbs up its own genealogical tree, has been of
service, but it has also been mischievous. It is so easily
exaggerated. Till the sixth day in the case of the chick the
embryo is not visibly a bird embryo ; it might be a reptile
embryo as far as external inspection tells us ; but it is never
like a fish, nor ever like any reptile, it is only like an embryo-
fish, an embryo-reptile. The recapitulation is rather in the
development of organs than in the development of the
embryo as a whole. The appearance and disappearance of
the notochord, the gill-clefts, and the visceral arches, the
stages in the development of heart and circulation, the brain
and the skull, are wonderfully like recapitulations, and we do
not know how any one could interpret the appearance and
rapid disappearance of old-fashioned organs like the noto-
chord and the gill-clefts except as vestigial relics of long- past
racial history. But it must be emphasised that the so-called
recapitulation is a very general one : that it is seen rather in
the stages of organs than in the phases of the whole creature ;
that it is a recapitulation of embryonic stages, not of adult
forms ; that it is often condensed and, as it were, telescoped ;
and that in very early days there are evidences of the
specific bird that is to be.

Embryology is entirely a modern science. Though
Aristotle (384-322 B.C.) watched the heart -beats of the still
unrecognisable chick within the egg, and had hold of the idea
that development is a progressive differentiation, he had
practically no successors before Harvey (1578-1657).

Harvey got a grip of the fact that almost every living
creature is produced from an egg — ovum esse primordium
commune omnibus animalibus — and of the fact that the
initial stage is not a preformed model, but something
apparently simple, in which, as he said, " no part of the
future organism exists de facto, but all parts inhere in

182 THE BIOLOGY OF THE SEASONS

potent ia." But Harvey had no way of accounting for the
wonderful primordium with which he started, at times he
was not even sure that it was entirely due to the parents.
" Neither the schools of physicians nor Aristotle's discerning
brain have disclosed the manner how the cock and its seed
doth mint and coine the chicken out of the egg."

We now know this much clearly, that the primordium
owes its peculiar virtue to the fact that it is continuous
through unspecialised cell-lineage with the fertilised egg
from which the parent arose. There is a sense, as
Galton said, in which the child is as old as the parent, for
when the parent's body is developing with manifold differ-
entiation from the fertilised ovum, a residue of unaltered,
unspecialised germinal material is kept apart to form the
reproductive cells, one of which may become the starting-
point of a child. Similarly Weismann, generalising from
cases where the lineage is visibly demonstrable, maintains
that the germinal material (germ-plasm) which starts an
offspring owes its virtue to being materially continuous with
the germinal material from which the parent or parents
arose. Since Virchow's Cellular-Pathologie in 1858, there has
been a growing acceptance of this idea of germinal con-
tinuity, which makes development a little less of a puzzle.
There is a beadlike continuous lineage of germ-cells, of
which individuals are the mortal pendants ; the parent is as
much a trustee of the germ-plasm as the producer of the
child. In a new sense, the child is a chip of the old block.

We do not know how the potentiality of a bird is con-
densed into a little clear drop of protoplasm with a nucleus
lying on the top of the yolk, just as we do not know how the
potentiality of doing very effective and wonderful things is
condensed into the pin-head brain of the exceedingly un-
teachable ant ; but we do know now how the germ-cell
differs from the cells of the body of the parent, being, through

WITHIN THE EGG 183

unspecialised cell-lineage, a direct descendant of the fertilised
egg from which the parent arose. The idea of germinal con-
tinuity has brought much light into biology.

We know in the case of the chick, for instance, exactly
how stage succeeds stage, often in a circuitous fashion as if
not going straight to the end; but we do not know the
mechanics of development, how each stage conditions the
next, except in a vague sort of way. The Archiv fur
Entwicklungsmechanik contains, however, many papers
which show that some analysis is quite feasible. In some
cases we know quite precisely that e will follow a, b, c, d, but
we do not know how it comes about. The descriptive
account is sometimes nearly perfect ; the causal analysis lags
far behind, especially because (i) development is growth, and
growth is of the very essence of life ; and (2) development is
the expression of a mosaic inheritance which is gradually
realised. Is it not very difficult often, in spite of our theories
of association, selective memory, controlled attention, infer-
ence, and so on, to give any feasible account of how one
thought grows into a bigger and better one, though we feel
sure that the idea had a development, is a product of con-
scious or subconscious antecedent stages ? The same sort of
puzzle faces us in the study of development. Out of the
apparently simple there emerges the obviously complex ; we
see the stages, but we do not yet fathom the how of them.
We often think of a rich inheritor with a thick cheque-
book ; we can give some consecutive account of him, but
ever and anon he surprises us by a new departure, which
means that he has cashed part of his legacy. So the develop-
ing bird is progressively cashing, i.e. expressing or realising,
part of its inheritance. But its ways are very orderly.

In a few hours the apparently simple drop of formative
protoplasm has become a disc of cells, in a few days it has
passed through the great events in vertebrate development —

184 THE BIOLOGY OF THE SEASONS

the making of the brain and spinal cord, the making of the
transitory skeletal axis (the notochord) and the foundation-
laying of the future backbone, the formation of the food-
canal, the establishment of the musculature, the body-cavity,
and so on.

Within a few days, it may be a week or more, the embryo
is recognisably a bird-embryo, within a few more days it is
recognisably a particular kind of bird — with cuckoo's feet
or kiwi's breast-bone, or the hoatzin's claws, or a pattern
of feather-tracts (before there are any feathers), which
is distinctive in most birds. Soon, moreover, it is
visibly, as it has been throughout invisibly, a particular
species of bird. Even audibly, for one may hear from
within the shell the characteristic call-note of the future
bird, e.g. of peewit, or gull, or coot, speaking before it is
born.

Not infrequently, however, some of the individual char-
acteristics of the bird are, as it were, held back from ex-
pression— the hereditary cheque not cashed — until some time
after birth. The facts go to show that this retardation of
expression is especially marked in regard to characters which
have been fixed relatively late in the racial history of the
species.

To put it concretely, it is a noteworthy fact that the
characteristic bills of spoon-bill, humming-bird, and scissor-
bill are not expressed until long after birth, just as part of our
own inheritance is often held latent for many years until
the appropriate, or it may be, to us, inappropriate time for
its expression comes — when its liberating stimulus —
A uslosungsreiz — arrives.

Meanwhile the patient task of incubation proceeds.
Usually the hen sits ; sometimes the two parents co-operate ;
rarely the patience is wholly masculine, as in the bustard-
quails. Sometimes, moreover, the incubation is left to the

WITHIN THE EGG 185

sun, or to the warmth of decomposing vegetable matter, as
in many mound-birds. And the cuckoo is notorious for
having found out the device of being maternally virtuous
by proxy.

An important point, of course, is that the embryo is very
imperfectly warm-blooded, and that the development will
slow or even stop if there be not a requisite warmth, and that
even the fledglings are very imperfectly warm-blooded and
may die if left for some hours exposed. Young birds are
very imperfectly warm-blooded in those cases where brooding
is habitual, and it is interesting to notice that old-fashioned
primitive birds, such as the Emeu (like old-fashioned primi-
tive egg-laying mammals), are also, as adults, imperfectly
warm-blooded.

Of great interest is the epoch — after two to six weeks —
when the embryo, well-formed, and it may be with a suit of
feathers, has used up its legacy of yolk, and must emerge. It
thrustsits bill at thebroad end of the eggintothe air-chamber,
which has been gradually growing larger ; it gets its lungs
inflated for the first time ; it becomes suddenly more vigorous
and writhes in its birth-robes ; it pecks with its egg-tooth at
the shell, makes a crack, a hole, a rent — and sinks squirming,
like a half-made thing, on the floor of the nest, or steps boldly
out into the world of action and freedom.

LEARNING TO LIVE

IN illustration of the concrete study of young animals,
we propose in this chapter to give a short account
of some observations made a number of years ago on the
behaviour of young gulls (Larus ridibundus) artificially
hatched. Our study was too slight to afford important
results like those reached by Professor Lloyd Morgan and
others, but it had its interest, especially as the observations
relate to a thoroughly wild bird, and not to the domesti-
cated chick.

The gullery which furnished the material for this study
was for many years one of the sights of Spring. The removal
of the bird — the black-headed gull — from the list of those
protected has reduced the colony to very small dimensions,
which is regrettable from a natural history point of view,
and also economically, since the bird is in the main insectiv-
orous, and does much good in destroying wireworms and
similar pests. But that by the way ; the gullery was a
sight to see — with four or five thousand birds nesting in a
somewhat circumscribed swampy area. When they rose in
alarm and filled the air with their wings and deafened us
with their harsh cries, we got a vivid impression of the
abundance of life. This was increased when the eye
became accustomed to detect the hundreds of nests. An-
other general fact of which one was apt to receive unpleasant
proof was the security of their nesting haunt from human
intrusion, for the foothold was treacherous in the extreme.

Repeated visits made one familiar with the gullery,

186

LEARNING TO LIVE 187

and a few observations may be noted. Although the thou-
sands of birds were extraordinarily quick to take alarm,
or at least to rise excitedly into the air, they submitted
in two or three minutes to the presence of an intruder
if he sat quite still under a covering of sacking. The birds
would then come within arm's length and settle down, though
the shape of the observer, who was peering through holes
cut in the sacking, formed the most conspicuous object in
the immediate environment. By this method of observa-
tion it was possible to make sure of the fact that the same
bird came back to the same nest. That is, of course,
what one would expect them to do, but as there may be
hundreds of nests within a small radius — at least half a
dozen on an area equal to that of an ordinary dinner-tab1 e
— and as the very uniform stretch of mud, tussocks, and
bog-bean stems presents to ordinary eyes few distinctive
marks, and as there is continuous rising, squabbling, and
re-settling, it seemed well to take some pains to fix the
attention on birds with some slight peculiarity in their
plumage, and to prove that they came back to their proper
nest. The extraordinary variability of the eggs may
facilitate the recognition of the nest during the da}'. On
one occasion it was observed that a very young nestling
of the first or second day, which had tumbled out of its own
nest and crawled to the next one, was accepted without
demur, which seems to be frequently the case with birds
that nest in large companies. On the other hand, older
youngsters, able to run about, were pecked at very viciously
when they came near a brooding bird.

It was worth while year after year to look at hundreds
of nests to get an indelible impression of the extraordinary
colour variability. No words can describe it, several
plates are necessary, but as the eye passed from, for
instance, unspotted pale blue to very dark brown with

i88 THE BIOLOGY OF THE SEASONS

darker spots, one felt that the bird had not settled down
to any particular colour or pattern. As in another well-
known case, the guillemot, the coloration is still varying
copiously. In both cases, it may be said that the locality
in which the eggs are laid makes the colour immaterial,
or at all events unimportant. One felt also that if cir-
cumstances should arise in which it became of survival
value that the eggs should be of a particular coloration,
there was present abundant raw material from which to
select.

Some eggs removed from the nests were transferred to
an incubator in the laboratory, and hatched there — the
usual method in an inquiry into instinctive behaviour.
Observations immediately after the artificial hatching were
rendered difficult by the imperfect warm-bloodedness
of the young birds. When removed from the incubator
or from a warmed box they were in a few minutes oppressed
by the cold, and uttered their cry of discomfort almost
continuously. As observations under conditions of dis-
comfort are fallacious, the birds were at first studied only
for a few minutes at a time.

Hatched with open eyes, which did not wink on the
approach of a finger, the young birds showed no sign of
any fear. A notable fact indeed was their extraordinary
self-possession throughout, though suspiciousness gradually
grew on them. It may here be noted that in early days
the presence of a cat or a dog did not seem to excite any
attention ; later on there was complete attention, but no
apparent fear. A gull two or three weeks old will run at a
fox-terrier and peck its nose ; but later on, before they
fly off, when about a month old, the birds utter the alarm
cry and retreat on the sudden appearance of a cat or dog.

Within a few hours after hatching the young birds
pecked at a finger or at a spoon, held close to them, with or

NESTING-PLACE OF KITTWAKES
(VII)

LEARNING TO LIVE 189

without food, but there was a lack of precision in their aim.
Many of the first day's pecks were misses, but the learning
was very rapid, and it was noted that the young gulls were
far ahead of young coots in the precision of their early
pecking. Even on the first day some fed repeatedly and
heartily, but this varied with the individual.

Some preening was observed on the first day, and the
general vertebrate action of raising the hind foot to scratch
the head — seen in frog, lizard, chick, kitten, etc. — was
frequently noticed. Almost from the first, too, there was
a slight use of the wings in balancing.

On the first day a young bird turned its head towards
the cheep of another in a separate compartment of the
incubator and cheeped as ij in response. A third, still
within the egg (chipped), often uttered a note, twice re-
peated, when the others cheeped. But only a few observa-
tions of this sort were made. Little or no attention was
paid to noises, except to a prolonged low whistle, which
was followed by cowering, even on the first day after
hatching.

On the second day the pecking was vigorous and pre-
cise ; the young birds followed bright objects by moving
the head and neck, and pecked at them in motion. They
attended to sleeve-links, ring, silver spoon, and similar
shining things. They would look up in answer to a tap
on the window of their cradle — perhaps because of the
actual vibration, but they took no heed of snapping fingers,
of the ring of a spoon on a glass beaker, of the rubbing
of a cork on glass, and many other striking noises. They
shrank a little from a sharp hand-clap close to them, but
did not cower, and it may have been the gust of air that
affected them. A prolonged low whistle again made them
crouch in silence, but after a number of trials on one day
(the second) one of them entirely ceased to respond. It

igo THE BIOLOGY OF THE SEASONS

would be interesting to discover whether there is in the
normal environment of the gullery some alarming sound
corresponding to the low whistle, for that and a hiss were
the only sounds (apart from their neighbours' cheeping)
that seemed to fix their attention and induce cowering.
Later on the birds learned to associate certain sounds
with their food supply.

The sensitiveness to cold, which unfortunately led to
a repeated reduction in the number of young birds, was still
very marked on the second day. Even on a rug in front
of the fire they would creep into the observer's hands or
crawl up his sleeve, apparently for warmth. At the pond
many of the young birds seemed to be in a state comparable
to cold coma, and it may be suggested that some measure
of this may be useful in tending to prevent premature
excursions which would in many cases inevitably land
the birds in the water.

As is well known, the adults are very combative birds,
and it was interesting to observe a fight early on the second
day of life. The child is father of the man. Beth pecked
at Aleph's bill, and Aleph responded, beginning a tussle so
forcible that separation seemed advisable. It was striking
in connection with these youthful tussles to notice the
interlocking of the bills, just as may be observed in the
combats of the adults. As has been pointed out by Bor-
dage, these bill-wrestlings are of biological interest in con-
nection with the regenerative capacity shown by injured
beaks in various kinds of birds, such as storks. At this
high level in the animal series it is rare to find much re-
generative capacity, and its retention in the case of birds'
beaks may be in part interpreted in the light of the fact
that injuries to the beaks are frequent in natural conditions.
For Lessona's famous law of the distribution of regenerative
capacity is that it tends to occur in those animals and in

LEARNING TO LIVE 191

those parts of animals which are in the natural condition
of their life very liable to non-fatal injury.

It is difficult to suppose that the second-day combat
was other than an early expression of the combative in-
stinct ; it could hardly be due to hunger in the case of Aleph
and Beth at any rate, for between their first and second
days they were fed at 3.30 a.m., at 6 a.m., at 9.30 a.m.,
and so on till 6 p.m. They would only take a little at a
time, but that greedily enough. It is probable that in
natural conditions the mother gives them mouthfuls with
great rapidity, but it seems very difficult to observe the
act of feeding at the gullery.

On the third day one of the young gulls had a bath,
and showed the completeness of the cleaning instinct. The
head was ducked sideways, shaken about, and re-ducked
precisely in the adult fashion, and this on a first experience
of water in bulk, and of course without any example.
After some cleaning the bird drank in the usual chick
fashion. Another bird, Omega, was put on its third day
into a deep bath : it screamed for a few seconds, then
settled down to paddling in a thoroughly efficient fashion,
but with a tendency to swim backwards. It washed its
head thoroughly, cleaned its bill with its foot, turning round
and round in the water like a top, and after the bath it
preened itself. Repeated experiments with different birds
showed perfectness of swimming powers without experience
or imitative stimulus, and perfect preening after the
bath.

In several cases the bath seemed to be premature, for
it was followed by extreme weakness and inability to
stand upright. After various treatments — warm milk,
a little oil, massage, and drying in a warm place, there
was rapid restoration to normal vigour.

Omega on its third day was fighting with X of two

192 THE BIOLOGY OF THE SEASONS

days ; a vigorous hiss on the observer's part made it cower
down into a corner, as if thoroughly frightened. The
fact is worth recording, since the almost complete absence
of fear was characteristic. The same bird Omega fought
on its third day with Y of two days, and they showed their
bills gripped in the adult fashion.

The observations made, though far from thorough, left
a strong impression that the wild bird is in some respects
more endowed at birth than the chick — than even the
cleverest chick, for they differ considerably.

For instance, while Lloyd Morgan's chicks would gorge
themselves with useless or hurtful things, such as red-
worsted worms, the young gulls were from the first judicious
in their eating. During the first two days they got some
cotton-wool from their bedding into their mouths, but this
was inevitable. They often pecked at useless things or
at conspicuous spots, such as a letter on a piece of paper,
and so persistently at spots on the feeding saucer than one
without spots had to be used, but they never swallowed
anything injurious or useless. They would test particles
of tobacco, for instance, with an exceedingly rapid touch,
but they never went beyond testing. The same held good
for young coots. One of the gulls, X, was tried repeatedly
with a little twisted roll of paper ; he pecked at it three
times after much provocation, but threw it away each
time. On the positive side, it may be noted that they ate
small worms in the garden and small insects without any
hesitation the very first time. A noteworthy achievement
was breaking a worm into pieces. A heavy meal of a
particular sort seemed to be followed next day by re-
pugnance to the same kind of food ; they showed that
kind of repentance which is " the weight of undigested
meals ate yesterday." Thus when Alpha and Beta ate
too much fish on Friday they would not touch it on

LEARNING TO LIVE 193

Saturday, but partook of liver freely; and similarly with
many other food-stuffs.

As to quickness of learning, the observation was made
in regard to two young birds taken from the nest, who were
having their first experience of food in a saucer, that the
elder, after having some food given to it, proceeded to
peck of itself, while the younger, who would at first peck
only at the bill of its senior, began within five minutes to
peck also out of the saucer.

As to words, the basis of experience was not sufficiently
wide to bear secure conclusions, but there seemed to be
at least four words, (a) There is the peep-peep uttered
before birth, and also long afterwards when the birds are
not quite comfortable. Sometimes in those artificially
reared it would not be heard for fifteen minutes or more.
It means cold, hunger, or some discomfort, (b) Secondly,
there is a deeper, more adult-like quack of two syllables,
uttered in excitement in the presence of food, (c) Thirdly,
there is a short alarm cry, uttered when the bird is suddenly
disturbed, (b) Fourthly, when the young bird appears to
be contented and very comfortable, it utters a plaintive,
almost sigh-like cheep.

One thing the gulls seemed to have to learn in their
artificial environment was to recognise water to drink,
but this may have been partly due to the fact that it was
presented to them in a very unnatural way — in saucers,
glass vessels, and shallow baths. Although thirsty, and
willing to take a drop from the end of a wet finger, they
would walk round, or even at first through, a saucer with-
out using their opportunity. Like Lloyd Morgan's chicks,
they drank when they got their bills wet by happening to
peck while standing in water, and they also drank when
thrown into water. Only after ten days' education did
one go straight to a dish of water placed on the floor and
13

194 THE BIOLOGY OF THE SEASONS

drink from it. An association was probably established
between a shining surface and drink, for some gulls about
three weeks old tried to drink from a glass lid removed from
a pasteboard specimen box and placed on the floor.

Numerous little observations grew into a general

impression that the kin instinct was strong, but it would

be important to investigate this point carefully. There

seemed to be, even from within the egg, a responsive

piping to those outside, whereas Lloyd Morgan's artificially

reared chicks paid no attention to the cluck of their mother

—of whom they had no experience whatever — when she

called from outside the door. A newly hatched gull,

called Beth, tried on the first day to make towards Aleph

in a separate compartment of the incubator ; an older

bird showed the greatest complaisance towards its younger

companion, who followed it about and often tried to snuggle

under its imperfect wing ; when a novice about to have

his first bath tumbled into the water, and screamed, being

for a moment confused, his companion, who had experience

of two previous baths, jumped in, swam to the novice,

and touched him. When two strangers were brought

together for convenience of warmth, there was in one case

amity after a few bill-peckings, while in another case they

were not seen nestling together till the third day. In two

cases when a gull had taken flight into freedom, leaving a

younger companion in the garden, the first to fly returned

several times to visit the younger until it also flew. It

was also interesting to notice that adults of the species

flew about overhead when the young in the garden were

approaching their time for flight. On the other hand, a

herring gull which had been shot in the wing and lived in

the garden displayed not the remotest interest in its small

congeners Nor were young coots interested in young gulls.

There seemed to be an instinctive following of one gull

LEARNING TO LIVE 195

by another, as is indeed common among birds. Indeed,
to find one in a large room in the summer twilight, the
quickest way was to set loose another. In confirmation
of what has been remarked by Thorndike, it may be noted
that one of the young gulls used to follow a little boy's
bare feet persistently over the lawn, nestling beside them
when he stood still.

Finally, it may be noticed that while there was for
three or four weeks great tameness and familiarity on the
part of the young gulls, the wild shyness and suspicion
seemed to grow quickly after they were able to rise from
the ground. The species is, of course, migratory, and there
seemed to be a growing restlessness towards the end of
July. But this may have been prompted by adults who
occasionally flew round and round overhead. It was
noteworthy, however, that there was a return of tameness
on the part of a younger bird after the flight of its senior
left it alone in the garden. It was once seen, for instance,
to thread its way through a group of children squatted on
the lawn, and coolly appropriate a strawberry from one
of the plates.

THE PLASTICITY OF LIFE

IN his first Law of Motion, Newton stated that " Every
body perseveres in its state of rest, or of uniform
motion in a straight line, except in so far as it is compelled
by forces to change that state/' In this magnificent
truism are summed up two aspects of Nature which are
everywhere familiar to us — the tendency to persist in a
given state or along a given path, and the liability to
diverge under the action of incident forces. We may call
the one the aspect of inertia, the other the aspect of change.
Constancy, continuance, persistence, we see on the one
hand ; change, compromise, novelty, on the other.

Is it not true even of that complex which we call our
personality ? Our mental environment, our intellectual
furniture, our ruling ideas — how they change for better
or worse as we live ; but beneath all there is a permanent
element — a certain style of mental architecture, so to
speak — which seems to change but little. The child, as
we say, is father of the man.

The twofold impression of novelty and of persistence
is familiar in history ; periodically everything seems to
become new, there are renaissances ; on the other hand,
history repeats itself ; some of the trade-tricks of the
Phoenicians or the banking-devices of ancient Babylon
recur to-day, and we say, with a sigh, that there is nothing
new under the sun.

We see the same two aspects in the history of that

complex which we call our body. It is ceaselessly chang-

196

THE PLASTICITY OF LIFE 197

ing ; it is always being un-made and re-made. We need
not believe the rough guess of the old physiologists, who
said that we were made all over again every seven years ;
but there is no doubt as to the ceaseless changes of break-
ing-down and building-up. In spite of all, however, the
body does in great measure retain its integrity. The
scrap of iron on the window-sill changes : it rusts ; it becomes
something else — oxide of iron. But the changes in the
living body are for prolonged periods not incompatible
with a certain permanence of character ; the body retains
its integrity. Chemically regarded, life is in great part a>
series of combustions ; but we may say of the organism,
"nee tamen consumebatur." There is a quality of per-
sistent sameness.

This important idea has been well expressed by Huxley
in his Crayfish, p. 84 : —

" To put the matter in its most general shape, the body
of the crayfish is a sort of focus to which certain material
particles converge, in which they move for a time, and
from which they are afterwards expelled in new com-
binations. The parallel between a whirlpool in a stream
and a living being, which has been often drawn, is as just
as it is striking. The whirlpool is permanent, but the
particles of water which constitute it are incessantly
changing. Those which enter it, on the one side, are
whirled around and temporarily constitute a part of its
individuality ; and as they leave it on the other side,
their places are made good by newcomers.

" Those who have seen the wonderful whirlpool, three
miles below the Falls of Niagara, will not have forgotten
the heaped-up wave which tumbles and tosses, a very
embodiment of restless energy, where the swift stream
hurrying from the Falls is compelled to make a sudden
turn towards Lake Ontario. However changeful in the

ig8 THE BIOLOGY OF THE SEASONS

contour of its crest, this wave has been visible, approxi-
mately in the same place, and with the same general form,
for centuries past. Seen from a mile off, it would appear
to be a stationary hillock of water. Viewed closely, it is
a typical expression of the conflicting impulses generated by
a swift rush of material particles.

" Now, with all our appliances, we cannot get within a
good many miles, so to speak, of the crayfish. If we could,
we should see that it was nothing but the constant form
of a similar turmoil of material molecules which are con-
stantly blowing into the animal on the one side, and stream-
ing out on the other."

While we agree that the metaphor is just and striking,
we feel that it has, like every other metaphor, its risks and
limitations. As we have said in another place, " One may
push the whirlpool metaphor too far, so as to give a false
simplicity to the facts, for when vital whirlpools began to
be, there also emerged what cannot be discerned in crystal
or dewdrop — the will to live, a capacity of persistent experi-
ence, and the power of giving rise to other lives."

But what especially concerns us at present is, that our
outlook on the animate world around us shows us at every
turn the contrast which we have reiterated — the contrast
between constancy and novelty, between continuity and
new departures, between inertia and changefulness. On
the one hand, there is the remarkable constancy between
successive generations, the persistence of a specific average,
the racial inertia ; on the other hand, there is the continual
emergence of the new, the abundant crop of new departures,
the racial mutability. Commonly, but not very accurately,
the contrast is stated as that between heredity and varia-
tion. More accurately, it is the contrast between
vital arrangements which tend to preserve an already
established order, and others which provide the raw

THE PLASTICITY OF LIFE 199

materials for further progress, or it may be, of course,
degeneracy.

When we realise how strong racial inertia is, and how
literally we are chips of that old block which is the average
of our stock, when we recognise that our inheritance is a
mosaic of ancestral contributions, when we learn the
inexorableness of what is called filial regression, which
brings the children of unusually gifted or unusually ungif ted
parents towards the mean of the race, we are apt to become
fatalistic. Therefore it is useful to illustrate, especially
in the Spring, something of the other aspect of life — its
plasticity. It must have been with some good reason that
a sagacious thinker like Buckle depreciated the importance
of heredity ; the reason was his vivid impression of the
power of nurture — surroundings and habits — in moulding
character, both bodily and mental.

There is a well-known shore animal, Lingula by name,
one of the lamp-shells or Brachiopods, which has been living
in the world since the earliest ages (the Cambrian) of
which we have fossil remains. Its direct ancestry is trace-
able for millions, probably several hundreds of millions, of
years. It is literally a " living fossil." It flourished in
the Cambrian ages, and flourishes very well still. It is
so abundant to-day on some shores that its body is sold
by the peck for food. Now the point of particular interest
is, that this ultra-conservative animal has not changed all
the time so far as we can tell from examination of the
shell. There may have been internal changes in the soft
parts, or there may not ; we have no evidence. But as
regards externals, Lingula has lived on for millions of
years unchanged. It illustrates a remarkable hereditary
constancy, sustained throughout a lapse of time which is
so great that we cannot even vaguely imagine it. It is
obvious that if all the living creatures we know had a story

200 THE BIOLOGY OF THE SEASONS

like Lingula, appearing in the Cambrian and living on
apparently unchanged until to-day, we should never have
had any theory of organic evolution to puzzle over. We
may regard Lingula, then, as the supreme instance of
static racial inertia ; and it does not stand alone. But
to judge of the history of animal life from cases like Lingula
is, as has been said, like judging the flow of a river by a
study of a small, quiet pool on its shore.

In contrast to the conservative Lingula we may take
the common jellyfish (Aurelia aurita) as a good illustration
of variability. It is constantly exhibiting variations, that
is, inborn changes of germinal origin which result in the
organism being different from the norm or average of its
species. We know from the records of zoology that it has
kept up this sporting for a great many years, though
nothing seems to come of it after all. It is normally a
tetrapartite animal, but sexpartite, pentapartite, and, more
rarely, tripartite forms occur ; and the detailed variations
are manifold. Similarly, whether we take pansies or
poultry, wild animals or tame, we get the same impression
of many a living creature as a Proteus. Whether we
examine the vertebrae of sloths or the teeth of apes, the
colour of dog-whelks or of guillemots' eggs, the external
characters of land-snails or of ruffs, we have the big fact of
variability staring us in the face. And whenever we begin
to compare specimens with their " specific characters,"
which are only averages, whenever we take the trouble to
measure and weigh, we discover that the fountain of
organic change is more copious than even Darwin dreamed
of. " Even Darwin himself," Wallace says, " did not realise
how much and how universally wild species vary/'

It is not to inherent variability, however, that the term
plasticity refers, but to modifiability, to the capacity of
being individually and directly changed in response to

THE PLASTICITY OF LIFE 201

changes in habits and surroundings. The changes which
crop up in a brood of jelly fishes or in the progeny of an
evening-primrose, seem to arise in the mysterious arcana of
the germ-cells. They are born, not made ; endogenous, not
exogenous. Modifications, on the other hand, are novel
responses to peculiarities in nurture ; they are physiologic-
ally traceable to changes in environment or in function, and
it is to them that our phrase, " plasticity of life," refers.

When an Englishman on foreign service becomes, in
the course of half a lifetime of work under a tropical sun,
so thoroughly tanned that the browning never disappears
through all his years of pension-life in a Scottish Highland
retreat — where the sun never scorches — we call that a
" modification/1 It is a structural change in the body
which transcends the limits of organic elasticity, and has
been so saturating that it persists after the originally
inducing causes have ceased to operate. We get clear of
vagueness if we adopt some such definition, and it is to the
capacity of undergoing such " modifications" that we wish
to restrict the term plasticity.

Sun-burning does not happen to be of much practical
importance, but it illustrates clearly what we mean by a
bodily modification directly due to environmental change ;
just as the formation of callosities or hard skin pads on
hands or feet may serve as an example of one which is
rather due to change in function than to change in sur-
roundings. What we wish to do is to show how broad a
biological basis this doctrine of modifiability or plasticity
has.

The fact that we wish to illustrate is the influence
of the environment in producing modifications. " 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

202 THE BIOLOGY OF THE SEASONS

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" (The Study of Animal Life, p. 308).

It seems convenient to begin with a set of influences
which may be associated together under the title molar or
mechanical. We refer to pressures — lateral and vertical,
to currents, to the action of gravity, to the amount of
available space.

Many years ago, Professor Semper took a number of
young freshwater snails (Limncea stagnalis), apparently
identical, and put them in different glass vessels, with the
same kind of water, the same kind of food, and so on, the
only known difference being that the volume varied. After
two months it became plain that they were not getting on
equally well ; those in the vessels of large volume were
growing apace, those in the small vessels were beginning to
lag behind. As others have since done, Semper reared a
series of dwarfs. Yung has also shown that the rate of
growth of tadpoles bears some relation to the ratio of the
amount of space to the number occupying it. Probably
there was some other factor besides the amount of room, but
there was no lack of food, air, or cleansing. In De Varigny's
repetition of Semper's experiments the conclusion arrived at
was, that the amount of exercise-ground at the top of the
water was a very important factor.

The trend of the branches on a tree often shows the
direction of the prevailing wind, and on some exposed parts
of our coast the surface of the tree-tops in the wood slopes

THE PLASTICITY OF LIFE 203

gradually upwards, as if it had been pruned with a knife.
The same sort of thing is seen in passive animals, such as
sponges and corals. Of particular interest are cases where
the same creature assumes quite different forms in different
surroundings : thus it seems well proved that the huge
Neptune's cup (Poteriori) is the free form of a little shell-
boring Clionid. Sometimes the environmental influences
are hard to separate from influences of function : thus
Camerano observed that tadpoles of Rana muta in swift
streams had longer and larger tails than those in quiet
pools near by.

A second set of environmental factors may be summed
up under the general title, chemical, including the chemical
composition of the surrounding air, water, soil, or other
medium, including also the quality and quantity of the
food. It may be fairly said that we are just beginning to
appreciate something of the subtlety of relations between
marine animals and the variable medium of sea-water in
which they live.

By altering the salinity of the water, Schmankewitsch
changed one variety of brine-shrimp (Artemia salina), in
the course of generations, into another variety, and
then reversed the process. It is very difficult to tell in
many cases how far the structural change is the direct
result of the environmental change, or how far the latter
is only the liberating stimulus of the former — setting free
some potentiality that was lying unexpressed in the egg
or young creature. Let us take a few illustrations col-
lected elsewhere.

" If the alkalinity of the sea-water be slightly altered,
the egg of a sea-urchin allows itself to be fertilised by the
sperm of a starfish, or of a crinoid, or of a mollusc (!),
producing larvae which all take after the mother. If the
chemical and physical state of the sea-water be slightly

204 THE BIOLOGY OF THE SEASONS

disturbed, artificial parthenogenesis can be induced in
starfish and sea-urchin, in worm and mollusc. Sometimes
the result of a slight chemical change is very perplexing,
and there are many experiments at which we look with
bated breath. Quaint abnormal larvae of sea-urchin and
frog are obtained by adding a little lithium salt to the water,
and the addition of a pinch of magnesium salt to the sea-
water containing embryos of the fish Fundulus heteroclitus
induces in a large number of these the development of a
single Cyclopean eye in place of the normal two eyes.
A small Crustacean called Gammarus, very common in
fresh water, has the habit of avoiding the light, but add a
little acid so that the solution is no stronger than ^g^th of
i per cent., and Gammarus swims towards the light.
Remove one or two of the metals from sea- water, keeping
up the alkalinity, and the sea-urchin's eggs all develop into
twins/'

The changes that may be brought about by altering
the qualities and quantity of the food are so numerous
and important, that we cannot wonder at Claude Bernard's
saying that evolution was throughout a function of nutri-
tion, or at the prominence which some sociologists give to
diet as a factor in human evolution. Although Mole-
schott's aphorism, " Der Mensch ist was er isst, " seems to
over-shoot the mark, the nutritive factor is one of the
strongest. Here again we must distinguish between a
directly modifying effect and the liberation of a latent
character. When we change the colour of canaries and
parrots by changing their diet, that seems to be a direct
effect ; but it is probable that the abundant and rich food
given to the queen-grubs in the beehive is not more than
liberating stimulus. Marchal reports that a scale-insect
(Lecanium corni) becomes another species (Lecanium
robiniantm) when reared on Robinia pseudoacacia instead

THE PLASTICITY OF LIFE 205

of on its own normal food-plant, though the reverse experi-
ment does not succeed. Every one knows how extraordin-
arily plants change in different soils, or under the influence
of manure, and it is to be suspected that some of the
hundreds of new parasitic worms that are continually being
described from new hosts are really old acquaintances
modified by a slightly different nutritive environment.
This suggests a line of experiment that is sure to lead to
interesting results.

A third group of environmental influences is that of
the physical energies — heat, light, and electricity. Heat
chiefly affects the rate of growth, promoting the formation
of nuclein-substances, and thus inducing cell-divisions.
A minute Infusorian (Stylonichia) studied by Maupas was
seen to divide once a day at a temperature of 7° to 10° C.,
twiceat io°to i5°,thriceat 15° to 20°, four times at 20°to24°,
and five times at 24° to 27° C. ... It is probably for this
fundamental reason that some molluscs are twice as large
in the Tropics as they are in Europe. In general, we may
say that increased warmth hastens growth and develop-
ment : in some cases it favours reproductivity, especially
of an asexual sort. The green-flies or Aphides multiply
prodigiously and parthenogenetically on our rose-bushes
and pear-trees in summer months, under the combined
influence of food and warmth ; when food becomes scarcer
and the weather colder in autumn, males are born, partheno-
genesis ceases, ordinary sexual reproduction recurs.

Cold retards growth and development. Thus Camerano
found that tadpoles of Rana muta remained tadpoles for
three or four years, when kept at a low temperature. The
period of development of the North Sea herring may be
doubled (extended to fifty days or more) by cooling
the water. The puzzle that the population of floating and
drifting marine animals is denser in the Arctic waters than

206 THE BIOLOGY OF THE SEASONS

in the Tropics, is perhaps explained by one of Professor
Loeb's experiments, which showed that lowering thetempera-
ture greatly increases the length of life of small crusta-
ceans. So in the cold waters there are more generations
living at the same time than there are in the Tropics.

As in other cases, it is difficult to distinguish the
direct physiological effect of a change of temperature from
the indirect effect due to the liberation of what is latent.
Lowering the temperature of the caterpillar box may be
followed by curious aberrations of colour in the moths and
butterflies, especially in the direction of darkening (melan-
ism). If the vessel containing some sea-urchin's eggs in
sea-water be placed near the stove for a short time, a large
proportion of them may form twins !

Light has subtle influences of many kinds, often illus-
trated by changes in coloration. Professor Poulton has
proved that the surrounding colour influences the colour
of caterpillars and pupae, apparently operating indirectly
through the nervous system. He showed, for instance,
that the caterpillars of the small tortoise-shell are for a
short time so sensitive, that those in a white or gilded box
have light or golden pupae, while those from a dark box
have dark pupae.

In the case of young flat fishes, such as soles and flounders,
light is the necessary stimulus for pigment-formation, and
the down-turned shaded side remains unpigmented. Mr.
J. T. Cunningham made the beautiful experiment of
placing a mirror on the floor of a tank where young flounders
were undergoing their gradual metamorphosis from sym-
metrical into asymmetrical forms. Out of thirteen young
flounders 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 down-
turned side, which normally remains white.

THE PLASTICITY OF LIFE 207

In the fourth place we may recognise a group of influ-
ences, much larger than might be supposed at first sight :
those which one living creature may exert upon another
by contact, pressure, irritation, poisoning, parasitism, and
so on. We may refer, for instance, to the hundreds of
different kinds of galls which are produced on plants as
reactions to a variety of stimuli, usually the salivary
secretions of the larvse of small Hymenoptera and Diptera
that have hatched within the leaf or twig. Or we may
mention the strange effects that follow the establishment
of the Sacculina parasite in a crab, and the deformations
that are due to other parasites. The pearls found in
various bivalves seem to be the beautiful sepulchres of
larval tapeworms or flukes, which the skin of the mollusc
smothers in layer after layer of translucent lime.

We have given only a few instances of modifiability —
one of the fundamental facts of the Biology of the Seasons
— but perhaps enough has been said to serve as a basis for
further study. Certain general results stand out.

It is noteworthy that young creatures, such as cater-
pillars and tadpoles, are far more modifiable than adults.
The reasons for this plasticity of youth are not far to seek :
the young and growing organism is less " set " ; it is still
arranging itself internally in many of its parts ; it has not
quite settled down ; it is more susceptible and less em-
barrassed. There seems almost no limit to the tricks
that may be played with tadpoles. Large portions may
be removed without apparent detriment, part of one may
be grafted on to another, their growth may be quickened
or slowed, and they may be kept for years from becoming
frogs at all.

All of this has its suggest iveness in reference to human
kind. We cannot hope to make a silk purse out of a sow's
ear, or tares into wheat, or bricks without straw, because

208 THE BIOLOGY OF THE SEASONS

of the inexorability of inheritance ; but we can, by judicious
changes in surroundings and habits, modify the individual
very much for the better, especially if we begin early
enough.

If we are to think clearly of modinability, we must
distinguish not only between inborn variations and acquired
modifications, but between direct modifications and the
secondary results of these, i.e. between direct modifications
and those changes to which the environmental change was
only the liberating stimulus — pulling the trigger that
allowed a latent character to find expression. We must
also admit the possibility — the discovery of which is one of
the most progressive steps in modern evolutionistic experi-
ment— that an environmental change may affect the next
generation without affecting the present one. Professor
Tower of Chicago worked for a dozen years on beetles of
the genus Leptinotarsa, which he subjected to unusual
conditions of temperature and moisture when the male or
female reproductive organs were at a certain stage in
their development. The result was to induce in the
offspring striking changes in colour and markings, and
also in some details of structure. Sometimes all the germ-
cells seemed to be affected, sometimes only a fraction of
them ; sometimes various changes resulted from the
same treatment ; some of the changes were brusque,
others showed intergrades with the parental conditions ;
sometimes the changes did not occur until after the lapse
of several generations in the unusual environment. It is
obvious, of course, that the experimenter could only
influence the reproductive cells through the body of the
parent, but the important point is that the body of the
parent was not affected. Here, in other words, we have
definite evidence of germinal variation evoked by environ-
mental stimulus.

THE PLASTICITY OF LIFE 209

There are several similar sets of facts in regard to plants,
and their elaboration is one of the most urgent and promising
of evolutionist inquiries. It is probable that we are here
on the track of discovering what may be called external
variational stimuli, and it may be that along this line of
experiment will be found an interpretation of some cases
suggestive of the transmission of modifications, which
is, for many reasons, highly improbable and, in any case,
unproved. It gives a fresh interest to the seasonal out-
look, too, to reflect that this complex and changeful environ-
ment, through which so many plants and animals, in spite
of all that we have said of their modifiability, pass callously
and unaffected, may yet be not without its influence on
generations yet unborn.

All naturalists are agreed in admitting that modifica-
tions are very common, that they are of much individual
importance, that they may have an indirect influence
through the parent's body on the offspring (especially
in the case of mammalian mothers), and that they may
have in various ways an indirect importance in evolution ;
but there is less agreement as to the answer to be given
to the following much-debated and often misunderstood
question : Does a structural change in the body, induced
by change of function, or by change in surroundings and
nurture generally, ever influence the germ-plasm in the
reproductive organs in such a specific or representative
way that the offspring will thereby exhibit the same modi-
fication that the parent acquired, or even a tendency
towards it ? For our part, we do not know of any clear
case which would at present warrant the assertion that a
bodily modification is ever transmitted from parent to
offspring.

What is certain, however, is that the plasticity of the
living creature admits of definite modifications being

210 THE BIOLOGY OF THE SEASONS

reimpressed on successive generations of individuals, and
a number of evolutionists (Mark Baldwin, Lloyd Morgan,
Osborn, and James Ward) have pointed out that modifica-
tions may thus serve as screens until coincident variations
(similar in appearance, though intrinsic — not extrinsic — in
origin, and with a greater grip) can emerge and establish
themselves.

Suppose, for a moment, that there was an island where
swarthiness of skin became, through climatic changes,
absolutely essential to success in life. Suppose that a large
proportion of the population became so tanned that they
met the critical test and survived — survived in virtue of
plasticity or modifiability. They would b.e in great
difficulties in regard to their children, awaiting the anxious
day when it would become plain that their children were
also plastic or modifiable in the direction of sun-burning.
Suppose, however, that meanwhile there was a widespread
constitutional tendency to swarthiness, suppose that more
and more innately swarthy children were born, does it
not seem extremely probable that the unentailed, purely
modificational swarthiness might act as a protective
screen, fostering the innate entailed swarthiness ?

To sum up, then, in a statement that will apply to
ourselves as well as to the plants and animals around us :
The complex environment produces modifications, which
are often very important to the individual, and may also be
of indirect importance in the evolution of the race ; it also
supplies the appropriate nurture (in the widest sense),
without which the inheritance cannot express itself ; and
it probably affords — though we know little of this as yet — a
succession of stimuli, provoking some of those germinal
variations which form the raw material of organic progress.

ADOLESCENCE

IT is impossible to refrain from continuing the line of
thought from the adolescence of animals to that of
man, but in so doing we must admit that there are great
differences. We have to remember that man is by nature
on a higher platform than that occupied by any of the
animals — a platform marked by language, reason, and
morality. We have also to remember that the human
environment differs very markedly from that of animals,
because of the rich external heritage expressed in social
institutions, historical records, literature, art, and so on.
Therefore, one should be very careful in carrying into a
discussion of human problems the conclusions that have
been reached by a study of animal life.

This cautious position is obviously sound, but it is apt
to become obscurantist. For it must not be forgotten that
there is an all-pervading unity among animal organisms,
including men ; there is essential similarity in structure,
in everyday functions, in manner of development, in the
nature of growth, in the punctuation of life, in the funda-
mental springs of conduct, and so on. It is therefore to
be expected that a study of animal life — embryonic, young,
adolescent, mature, and old — will have some light to throw
on human infancy, childhood, adolescence, maturity, and
old age. At the same time, it is a commonplace of scientific
method that every conclusion formulated in regard to a
particular order of facts — let us say the behaviour of birds —

212 THE BIOLOGY OF THE SEASONS

must be tested afresh when applied to another order of facts,
such as human conduct.

Returning to our figure of an ascending and a descending
curve, we see that the period of human adolescence is an
ill-defined part of the up-grade — after juvenile characters
have been for the most part lost, when adult characters
are being put on, when childish ways and childish things
are being put away and the life is taking definitive shape,
when sex-impulses begin to be more than whispers and the
limit of growth is within sight.

Our first note relates to the difficult question of growth.
From studies on animals it seems clear that growing is an
uphill business ; it is an ascent whose gradient becomes
always steeper and more difficult. It illustrates what is
called the law of diminishing return. At the same time,
though the juvenile rate of growth is never afterwards
attained, and in most cases is not even approached, there
is often a remarkable reacceleration during adolescence.
Like a good horse, the organism puts on a spurt as it gets
near the top of the hill.

Professor C. S. Minot compares the business of growing
to the building of a wall by one man. As the wall rises, the
man becomes more and more tired ; he has to lift the stones
higher ; he builds more and more slowly. The wall goes on
growing, but at a steadily diminishing rate. We may
say, perhaps, that just as he gets near his limit, beyond
which he cannot reach, he braces himself up for a rapid
effort.

Now, there is a corresponding acceleration associated with
human adolescence, and we do well to remember it, for
it means that the energies of the organism are necessarily
to some extent preoccupied with its own business. It is
an intricate and difficult problem]: there is increasing
stability and increasing instability, there is great vigour

ADOLESCENCE 213

and great " slackness " ; but the general statement seems to
us to be safe, that a rapidly growing adolescent is naturally
a good deal preoccupied — we mean, of course, organically,
not consciously, preoccupied — with his or her internal
affairs. This means that he or she should have plenty of
rest and plenty of play.

Our second note concerns internal rearrangements. If
we take a wide survey of adolescent animals, and mark
the beginning of the adolescent period by the assumption
of definitely adult characters and the laying aside of dis-
tinctively juvenile characters, then we must include in our
conception of adolescence the idea of internal change,
rearrangement, and readjustment. There is often among
animals a well-marked juvenile period, as we have seen, as
of caterpillars or of tadpoles, of kittens or of chicks ; there
is often a well-marked adult or mature period, of butterflies
or of frogs, of cats or of hens ; between the two lies the
ill-defined adolescent period, the biological hobble-de-hoy
phase, when the creature is neither juvenile nor adult,
but between the two. In this period there are often re-
adjustments and new adaptations. There may be increase
of complexity (differentiation) or the establishment of
more perfect unity (integration) — the two criteria of all
organic progress, whether individual or racial. The ado-
lescent creature is more complex than it was — from its teeth
to its nerve-paths ; it shows the structural results of
increased division of labour ; it differs from its juvenile
phase as the locomotive of 1910 differs from Stephenson's
" Puffing Billy/' But it also becomes more controlled,
unified, harmonious, more vertebrated and knit together ;
its character becomes set ; it gets a purpose in life. From
its plastic juvenile stage — often so delightfully irresponsible
— it differs in integration, just as the locomotive of 1910
differs from " Puffing Billy."

214 THE BIOLOGY OF THE SEASONS

It seems useful, therefore, to turn on the biological
light in considering the human facts, which are, in a way,
too near us to be fully appreciated. Let us think
vividly of the transition - period between tadpole and
frog, between caterpillar and butterfly, and so on, and
take back again to human life the impression of re-
differentiations and reintegrations (that is, of new com-
plexities and of new controls), of inflammatory crises and
of losses that mean gains. For thus we begin to under-
stand better why adolescence is so full of portent as well
as promise.

A third fact which lends further importance to adolesc-
ence is that it extends over the momentous, critical time
when decision is given in regard to the individual variations
which crop up during the juvenile period. We have seen
that each young thing is an original, that a child is always
leading the race, that it is in youth that the fountain of
unrealised capacity wells up. We have still to consider,
following Groos and others, the biological importance of
the play-period, when inborn variations have elbow-room,
when new departures have a chance, when there is an oppor-
tunity for originality to gain self-confidence, for a new
pattern of personality to gain some stability. Every one
knows that man, like other domesticated creatures, has
strong play instincts.

But on the heels of the period in which play instincts
find — or should find — full and free expression comes the
adolescent period, during which the conditions of the
struggle for existence, the rules of the serious game of life,
all sorts of restrictions and conventions, from the law of
the jungle to the etiquette of social behaviour, begin to
close in upon the individualities, the idiosyncrasies, the
peculiarities, in a word, the variations of the young life.
The organism must run the gauntlet of criticism, and often

ADOLESCENCE 215

it needs it much, if it is to survive well or survive at all. On
the other hand, the criticism, whether of circumstances
or of society, does not always make for progress, and many
fine buds are probably killed or spoilt. While it may be
impossible to lay down general rules for human adolescents,
the important thing is that we realise clearly what is happen-
ing. And since freshness is rare and monotony common,
it seems a wise rule that our judgments should lean to
mercy's side. Running the gauntlet may be necessary,
but let us be sparing with those heavy-handed snubs
which are so fatal to the growth of the saving grace of
originality.

In the fourth place, we may profitably link together the
two concepts of adolescence and plasticity. We have seen
that one of the biological certainties in regard to young
creatures is their plasticity in receiving modifications from
their surroundings. By modifications, as explained, we mean
changes due to peculiarities of nurture — changes neither
inherited nor transmissible, so far as we know. Now, great
modifiability, as seen in caterpillars and tadpoles, for
instance, is characteristic of youth, and it is often during
the adolescent period that decision is given whether a piece
of juvenile veneer is to persist or not. Undesirable youthful
veneer is often slipped off; effective veneer is often con-
firmed. When youthful modifications, for good or ill,
survive the adolescent period, the chances are that they
will persist throughout life.

In the fifth place, much of the biological importance of
adolescence is bound up with the central fact that it is the
period in which the promptings of sex-impulses first make
themselves normally assertive. In various ways — for in-
stance, by the liberation of chemical excitants (or hormones),
which saturate through and through the body — the sex-
impulses influence the whole being, transforming it not

2i6 THE BIOLOGY OF THE SEASONS

only externally, but in its inmost recesses. The trans-
formation may be almost violent — in man as in beast,
especially in the male sex — or it may be as gentle as the
coming of Spring.

The change is often a new beginning of life — it is to
be allowed for and respected. It should be seen in its
biological setting — as part of a world-wide process — yet
it is not to be hastily materialised. It should be seen
in an evolutionary light, in line with the evolution of
love in the animal kingdom. It may humble us at
times to recognise that adolescent experience in man-
kind is in some measure bound to be recapitulative, but
it will always make us hopeful to feel that it is part and
parcel of a great evolutionary movement, sharing in the
phylogenetic ascent from crude expressions of physical
fondness to what we must, in some sense, call spiritual
affection.

Considering the profound importance of the subject, we
may be pardoned for going a step further — recalling the
main thesis of an important paper by Mr. James Oliphant
in the International Journal of Ethics, in which it is pointed
out that in the course of civilisation there has been estab-
lished a sane tradition which sublimes sexuality by as-
sociating it with the best that is in us — chivalry, devotion,
self-control, worship. Unconsciously, for its own pre-
servation, humanity has idealised the sexual-impulse,
has detected its true inwardness, has linked passion to fine
feeling. In literature and art the ideal types of love in its
sublimest aspects have been immortalised, and with these
the minds of those who rejoice in their youth should be
filled, not as an artifice, but because thus a deeper meaning
and joy may be found. To fail duly to honour the sexual-
instinct means forcing it back in isolation as an animal
passion, whereas the lesson to be learned, until it become

ADOLESCENCE 217

organic, is to associate physical passion with the higher
emotions — to bind the insistent organic impulses into
unity with pride of flesh, pride of birth, a high standard
of cleanness and fitness, an honour of women, a love of
children, and a social self-respect.

THE PLAY OF ANIMALS

ONE of the most important indirect results of Darwinism
has been to convince naturalists that no fact of life
is trivial. To the inquisitive spirit everything is a problem ;
but the problem is illumined when we realise, as Bagehot
put it, that " everything is an antiquity " — the product of a
past often inconceivably long, an event, a personage, or,
it may be, only a " property " in the drama of evolution
which has filled the world-stage for millions of years. More-
over, it was part of Darwin's genius that he realised, more
than any other, the solidarity of Nature and the inter-
relations of things. The Systema Natures was the crowning
work of Linnaeus ; but it was a new system of Nature that
Darwin disclosed — a web of life — in which even the appar-
ently trivial fact is invested with momentous importance
because of its complex correlations with others. A moth,
escaping from an entomologist's window, is said to have
cost the United States a million of dollars ; a few sparrows
and rabbits, transported from their native home, disturb
the balance of life in two continents. The clay-clodlet
on a bird's foot may affect the fauna and flora of a district.

Similarly, play — whether of animals or of men — which
would have been regarded by most pre-Darwinian natural-
ists as a trivial thing — a sort of aside in Nature — has been
shown by Professor Groos to be of fundamental importance.
Let us see how this works out.

We need not spend time over any definition of play —
that comes last, not first. We see it all around us in the

Ml

THE PLAY OF ANIMALS 219

Spring-time, and we all have vivid reminiscences or present
experience of what it means. It is, to say the least, very
widespread among mankind, though one reads in Mr.
Kearton's entertaining book, With Nature and a Camera,
the following sentences in regard to the people of St.
Kilda : " I innocently asked the minister one day what
kind of games the children played. The old man smiled
good-naturedly at my ignorance, and answered : ' None
whatever ; their parents would consider it frivolity to have
them taught anything except climbing rocks, catching
sheep, and such other things as will become necessary to
them in after-life.' " Now, while we do not go the length of
placing play quite in the foreground of life, or of accepting
a brilliant artist's description of life as " a series of inter-
ruptions from golf/' we believe that Groos is right in his
thesis that play is fundamentally important. There are,
as we shall see, strong biological reasons for believing
that the good people of St. Kilda would increase their
present and future effectiveness, as well as happiness, if
they let the children play. That would probably do more
than increased postal communication to put aside " life-
harming heaviness."

When we watch the kittens with their ball, the dogs
and their sham-hunt, the lambs and their races, the monkeys
and their " tig," we get a vivid impression of play. We
may say, negatively, that play is not work, though it may be
as strenuous ; that play is not mere exercise, though,
perhaps, it exercises best ; that play has no seriously
perceived or conceived end for the sake of which it is
played, though it may be, while it lasts, most serious ; that
it is not necessarily social, for many an animal (like many a
man) seems to be quite happy playing alone ; and that it is
not necessarily competitive, though that often gives zest
to it. Of its positive content, we shall speak later. For

220 THE BIOLOGY OF THE SEASONS

purposes of clearness, we shall leave out of consideration
at present anything that might be interpreted as love-play
or courting-play, and keep mainly to the play of young
animals.

There are two main theories as to the play of young
animals, and the first is that play is an expression of over-
flowing vigour, energy, and animal spirits ; that it is the
byplay of vigour. This view was first clearly stated by
Schiller ; it was long afterwards elaborated by Herbert
Spencer — a strange contrast of champions.

This theory is simple ; but it is too simple, and it breaks
down badly. No doubt the young creature is an overflowing
well of energy ; but even the tired animal or child will
turn in a moment from fatigue to play. Moreover, the
theory does not in the least explain the characteristic forms of
play in different animals. In fact, the theory only states
one of the internal or physiological conditions of play —
there must be some energy to spare.

Schiller's theory of play was re-expressed, as we have
said, by Herbert Spencer ; but he, feeling its inadequacy,
eked it out by laying emphasis on imitation. The cause,
he said, is superfluous energy ; imitation defines the channel
of expression. The youngsters mimic in play what they
see their seniors doing in earnest.

This is a favourite theory, and there is a strong element
of truth in it. That it cannot be the whole truth seems
to have been shown experimentally. A kitten taken very
early from the mother will play profusely without any
known possibility of imitative stimulus.

The second theory of play is Darwinian, and Groos has
the credit of having developed it. According to this
theory, there are inborn play-instincts, characteristic in
form for different types. They may be stimulated by
superfluous energy and influenced by imitation, but they

THE PLAY OF ANIMALS 221

are in their essence instinctive. These play-instincts arose
like other innate idiosyncrasies (by germinal variation),
and they have been gradually established and strengthened
by the consistent elimination of the bad players (in sub-
sequent life-struggle).

But why should there be elimination of the bad
players ? Because play is justified in the business of life
in at least two ways ; firstly, because it is the apprentice-
ship to future work, the training for serious efforts, the
rehearsal before the real performance ; and, secondly,
because intellectual development probably flourishes
better in proportion as the brain is freed from the necessity
of bearing with it the hereditary mechanism for the perfect
performance of certain activities. If play can perfect any
instinctive activity before failure is vital, the weight of
a stereotyped inheritance is lessened.

But we may go a step further. Play is more than the
apprenticeship, the rehearsal, introductory to future life
and work. It is more than a means whereby the brain
may be freed from some of its hereditary burden, and thus
left more " educable." It is one of the few opportunities
which afford free scope for variations without too rigorous
selection. This is of very great importance as regards the
practical outlook of man, and perhaps also as regards art,
and we need hardly say that it has been an important
factor in the intellectual evolution of animals. In the
real business of life, most initiatives — " new departures,"
" idiosyncrasies," " variations " — are subject to rigorous
selection, which often nips them in the bud. Play is
Nature's device for granting temporary elbow-room for
variations, some of which may form part of the raw
materials of progress.

There seem to be two fundamental and primitive
forms of animal play — the play of movement, and the

222 THE BIOLOGY OF THE SEASONS

play of experiment. Let us, first of all, consider play of
movement.

" Most young things/' Hamerton says, " appear to
be reservoirs of pent-up natural energy that finds vent in
irrepressible gambols.0 But this takes specific forms in
different cases. Insects gambol in the air, birds among
the boughs, dolphins in the waves, and so on, endlessly —
each in its own way. There is no use in it, except that the
nerves and muscles are trained for future work. The heart
beats more quickly, the breathing is more rapid, the
peripheral blood-vessels expand, and there ensues that
happiness which is the reflex of healthy function.

Perhaps part of the significance of this simplest form of
play is to be found in the connection between pleasant
emotion and muscular movements. Such exuberance of
good spirits had the simple wood-chopper portrayed in
Thoreau's W alden, that when a thing amused him, " he
sometimes tumbled down and rolled on the ground with
laughter/' and perhaps we have here an expression of
primitive playfulness.

When we see beautiful sights, or hear fine sounds, or
the like, sensory impressions have, of course, travelled into
our brains. But they do not, so to speak, stop there.
They set agoing other messages, which travel out to the
heart, which beats differently ; to the larynx, which
vibrates ; to the lungs even, and to other parts. In short,
internal muscular movements occur. As the result of these,
a third set of messages travel in again to the brain ; and
when the circle is completed, we are pleased. Perhaps in
this way one gets nearer an understanding of certain
gambols and of the vocal play — the song — of birds. The
latter seems to be due to internal muscular movements
associated with strong emotions. In any case, there is
reason to believe in a deep and subtle connection between

THE PLAY OF ANIMALS 223

emotion and motion. Literally, Wordsworth's heart leaped
up when he beheld a rainbow in the sky, and filled with
pleasure as he watched the dancing daffodils.

The play-nature of animal movements is most obvious
when there is something unusual about them. Thus Alix
relates that on one occasion, when botanising on the Alps,
his dog ceased to follow him on the gradual path, and
seemed deliberately to choose a long slope of frozen snow.
There he lay down on his back, folded his legs, and slid down
like a toboggan. At the foot he rose quietly, looked up to
his astonished master, and wagged his tail. Alix imagined
that his dog had thought out the short-cut ; it is much more
likely that it was simply play — done for fun.

All movements that can be shown to have direct utility
must, of course, be excluded from the category of play ;
but a number of cases seem well substantiated. When
Romanes says of fishes, " nothing can well be more ex-
pressive of sportive glee than many of their movements,"
we feel that the statement is too general and vague ; but it
is difficult not to admit the genuineness of the movement
play of Macropods and of Sea-Horses. When Hudson says,
" I have spoken of the firefly's pastimes advisedly, for I
have really never been able to detect it doing anything
in the evening beyond flitting aimlessly about, like house-
flies in a room, hovering and revolving in company by the
hour, apparently for amusement," we feel the difficulty
of excluding some undiscovered utility ; but when we watch
monkeys on their swings, we feel that, if we are not to
make Nature magical, these are plays, and nothing else.

Let us pass to the other simple and primitive expression
of the play-instinct, what we may call experimenting —
when animals test things, often pulling them to pieces ;
or test themselves, often performing interesting feats ; or
test their neighbours, finding out how they will respond.

224 THE BIOLOGY OF THE SEASONS

For the endless task of finding out about the world has its
play-form — which is obviously one of the roots of science.

Speaking of his young goats, Mr. Hamerton says :
" If there is a basket in the place which will hold one of
them, and no more, the others will watch him with great
interest, and as soon as he jumps out (which he is never
very long in doing) the others inevitably jump in and out
again by turns. A game of this kind will last till one of the
kids has a new suggestion to make/'

One day it was the fashion among the kids to carry a little
sprig of green between the lips ; another day they tried to
upset the artist by getting under his seat ; from that they
passed to experimenting with the big dog, till "he could
stand it no longer and rushed out of the place, not trusting
himself to refrain from using his mighty jaws, which would
have crushed a kid's head like a nutshell."

As one sees, it is extremely difficult not to intermingle
inference with observation ; but there are some very careful
records bearing on the play of experiment. Thus we may
quote a few sentences from Miss Romanes' observations
on her Capuchin monkey — a very valuable and well-exe-
cuted piece of work : " He is very fond of upsetting things,
but he always takes great care that they do not fall upon
himself. Thus, he will pull a chair towards him till it is
almost overbalanced ; then he intently fixes his eyes on the
top bar of the back, and, as he sees it coming over his way,
darts from underneath, and watches the fall with great
delight ; and similarly with heavier things. There is a
wash-hand-stand, for example, which he has upset several
times, and always without hurting himself. One day he
played for a long time with a hearth-brush, learning to
unscrew the handle and, what was much more difficult,
putting it together again. When he had become by
practice tolerably perfect in screwing and unscrewing, he

THE PLAY OF ANIMALS 225

gave it up and took to some other amusement. One re-
markable thing is that he should take so much trouble
to do that which is of no material benefit to him." This
last remark is interesting, though it should have been ex-
pressed differently. It is part of the essence of play that
it is not of direct material benefit.

Passing from gambol and experiment to somewhat more
evolved forms of play, we find that a number of animal
games may be summed up under the title " sham-hunt."
Into this there seems to enter a psychological element of
self -illusion. The booty may be real, as when the cat
plays with the mouse, or both the booty and the chase
may be fictitious. The sham booty may be living, as
when the dog plays with a beetle, or, more commonly,
not living, as when the kitten plays with a ball of twine.

Many naturalists have written concerning the play of
a cat with the mouse. It has been interpreted as a whet-
ting of the cat's appetite, as a means of improving the
flavour of the mouse, and as elaborate cruelty. Romanes,
though a man of keen insight, committed himself to
the view that it illustrates the delight in torture. Prob-
ably these suggestions are all unnecessary. Surely,
what we see is just a little game, justified in the present
by the repetition of pleasant excitement, justified in the
future by the increased dexterity which it develops. When
exhibited by cats of mature years, it is perhaps just a
relapse into a favourite game of youth — and analogues
of this may be found among men. It must be remembered
that a great many carnivores play just as the cat does.
Their play is a practice for their work.

Another type of play is the sham-fight, which we see so

often between puppies or kittens. It has been described

among lions, tigers, hyaenas, wolves, foxes, bears, and other

carnivores ; among lambs, kids, calves, foals, and other

15

226 THE BIOLOGY OF THE SEASONS

ungulates ; it is also very common among birds. Care
must be taken to distinguish sham-fights from real fights,
and it may be admitted that among animals, just as among
boys, what begins in fun may readily pass into deadly
earnest. In a vivid description of the behaviour of two
young gluttons, Brehm says that nothing could be more
playful, they are almost never at rest for a minute, they
fight in fun all day, but every now and then the note of
earnest is struck.

Of much interest, considering the level at which they
occur, are the sham-fights of some ants. Near the begin-
ning of the nineteenth century, Huber related that on fine
days the meadow-ants collect outside the ant-hill and
hold sports, especially of a wrestling and gymnastic sort.
For a long time this story was rather scoffed at, and we
cannot wonder; but in 1874 Forel saw the same sight,
confessing at the same time that he should not have believed
it unless he had seen. The ants behaved like a crowd
of schoolboys riotous with fun — scrambling, wrestling,
jumping, and fighting. " Yet all," he says, " was without
anger and without any squirting of poison ; it was plainly
a friendly tournament." Fun seemed to be uppermost,
but it is possible that the apparent play might be a sort of
exercise or drill. It is also possible that the whole business
was misinterpreted, for it is notoriously difficult to get
mentally near animals in which instinctive behaviour is
dominant.

The sham-fight is one of a large group of social plays, of
which the characteristic note is rivalry — rivalry, however,
which has no serious reference to any material object of
desire. There is no doubt that the competitive element gives
zest to animal games as well as to those of man. It is not
essential, but it is an important auxiliary. It seems to be
a pleasure to the animal as to us " to be a cause " ; it is a

THE PLAY OF ANIMALS 227

greater pleasure to be a more effective cause than some one
else. We may refer to the races among lambs and kids,
wild horses, and asses ; the various forms of " tig " and
" follow my leader " in monkeys ; and to other rival
exhibitions of agility. Perhaps some forms of dance and
song should be included here, when they occur unconnected
with courtship. And even when they have some connection
with courtship, it is difficult to decide whether the court-
ship led to the play, or whether a form of play was utilised
in the courtship.

We may give one instance of the kind of competitive
display to which we refer, taking Mr. Hudson's description
of the cock-of-the rock (Rupicola) of tropical South America.
" A mossy level spot of earth surrounded by bushes is
selected for a dancing-place, and kept well cleared of
sticks and stones ; round this area the birds assemble,
when a cock-bird, with vivid orange-scarlet crest and
plumage, steps into it and, with spreading wings and tail,
begins a series of movements as if dancing a minuet ;
finally, carried away with excitement, he leaps and gyrates
in the most astonishing manner, until, becoming exhausted,
he retires and another bird takes his place." There are
similar displays among uncivilised races of men to-day.

To sum up : There are many play-instincts among
animals ; they have been wrought out in the course of
ages, partly as safety-valves for overflowing energy, partly
as the muscular correlates of emotion, partly as oppor-
tunities for the emergence of variations before too rigorous
selection begins, but mainly as periods for educating
powers which are essential in after-life. Animals, Groos
says, do not simply play because they are young ; they
continue young in order that they may play.

In short, play is so widespread because of its funda-
mental importance as the young form of work. The animals

228 THE BIOLOGY OF THE SEASONS

who played best when young, worked best, lived best,
perhaps loved best when they grew up, and thus through
the long ages the play-instinct has been fostered. It is
interesting, also, to notice that the animals which man has
succeeded in domesticating are notably playing animals.

If Groos's theory of animal play is biologically sound, as
it seems to us to be, it must apply also to human-kind.
Children's games are natural safety-valves, to close which
must mean disaster ; they are opportunities for the free
play of individuality, originality, idiosyncrasy — variations,
in short, more or less sheltered from selection ; they are
necessary to the perfecting of powers — physical, emotional,
and intellectual — which are afterwards of critical moment.
Play is thus a rehearsal without responsibilities, a pre-
liminary canter before the real race, a sham-fight before the
real battle, a joyous apprenticeship to the business of life.
Thus our study of animals playing in the Summer sunshine
gives a deeper meaning to the familiar saying, " All work
and no play makes Jack a 'dull boy." May we not twist
an old precept a little, and say, " Let us play while we can,
so that we may work when we will " ?

THE DUST OF THE AIR

ONE of the flies in the ointment of Summer is the dust.
It blinds and chokes us, making the highway journey
a penance ; it disfigures the hedgerows and spreads into
the meadows. Sometimes it rises in beautiful swirling
pillars which glide like wraiths along the road ; but, except
at a distance, dust is an abomination, and in many parts of
the world it is a terror. In the present transition age of
means of locomotion it is distressing to see how the dust
raised by automobiles has ruined beautiful wayside gardens ;
let us hope, however, that just because of motor-cars we
shall eventually have less road-dust than ever.

" Except at a distance," we said, for it is well known
that dust plays a very important role in making the world
beautiful, and it is well to consider this side of it. The
fundamental investigations, we believe, were those made a
good many years ago now by Dr. John Aitken, who first ex-
plained clearly the making of mist and the secret of fog.
Mist is a concentration of moisture round the dust particles
of the air, which are carried up from the earth's surface by
currents, by evaporation, and by volcanic action, or are
due to meteorites. Fog, in the same way, was shown by
Aitken to gather round the same minute foci ; and even the
raindrops have their black hearts. It is interesting to
look with a strong lens at the minute motes formed on the
well-cleaned glass-cover of a museum case during a foggy

day ; one sees that an almost microscopic drop has fallen

229

230 THE BIOLOGY OF THE SEASONS

and dried, leaving a circular mark with a dust particle in
the centre.

Mist, fog, cloud, and rain thus consist of more or less
wet dust-particles of great fineness ; or, to say the same
thing once again, fog is dust-dew. Familiar facts now,
but surely not without a certain poetry.

Aitken was led to a clever contrivance for actually
counting the myriad atomies of dust which play so im-
portant a part in making that curious mixture which we
call weather. The device was to make rain in the air, and
then count the drops. A measured sample of the sur-
rounding atmosphere is drawn into a receiver, where it is
diluted with a certain quantity of dustless air, and then
saturated with water. By a stroke or two of an air-pump,
it is expanded and chilled till the water vapour and the
dust fall together in a mimic shower of raindrops on a
polished plate.

When the miniature shower is over, that is to say, when
all the dust has fallen, the number of drops on a measured
area of this plate is carefully observed, and as each drop
has a dust particle in its heart, it is possible in this way to
count the motes which seem so incalculably numerous as
they " dance " on the path of a " beam of light."

By this simple apparatus for making rain and counting
motes, Dr. Aitken was able to gauge the quality of the air
in all sorts of places and conditions, and his method or some
modification of it is now in everyday use in Public Health
Departments and the like. We must be content to give
a few illustrative instances of this sampling. In the lecture-
room of the Royal Society of Edinburgh, before one of the
meetings, the air near the floor showed 275,000 dust-
particles in a cubic centimetre, but after the lapse of an
hour and three-quarters of meeting the scientific atmo-
sphere showed 400,000. Of obvious importance in connec-

THE DUST OF THE AIR 231

tion with less efficiently ventilated rooms, is the immense
increase in the number of dust-particles after the gas is
lighted of an evening. More sensational, perhaps, is the
fact that a cigarette smoker sends 4,000,000,000 particles,
more or less, into the air with every puff.

Of great biological importance is the contrast between
the freshness of the country and the dustiness of towns.
One clear day at Colmonell in Ayrshire there were only
500 particles (about the minimum) per cubic centimetre,
or 8200 per cubic inch, while on a wet morning near the
Central Station in Glasgow there were 466,000 per cubic
centimetre, or 7,642,400 per cubic inch. The brilliancy of
Swiss air is due to the comparative scarcity of dust, while
the dismal fogs of our large cities are due to its abund-
ance. The more dust-particles, in short, the murkier the
air, and what we call haze is often little more than dust.
The botanists tell us of plants which are particularly
sensitive to the dust in the air, and fade away when it
passes their limit of viability. The beautiful red Tropaeolum,
the summer ornament of so many cottages in the country, is
one of these dust-sensitive plants. Another fact of obvious
biological interest is the purifying effect of the rain. Aitken
and his followers have shown, for instance, how a heavy
shower may clean for a brief period the dust-laden atmo-
sphere of a town. A gale blowing from a pure quarter has
the same clarifying result.

It is characteristic of modern science that it appreciates
the cumulative importance of infinitesimally small items.
The commonplace that "many littles make a mickle" is a
generalisation which expresses some of the grandest results
of patient observation. So beside bacteria and earthworms,
beside coral polyps and chalk-forming animalcules, we must
rank dust as an agency of high importance. Whether it
be borne on the wings of the wind from one land-surface

232 THE BIOLOGY OF THE SEASONS

to another, or have what is vaguely called a " cosmic
origin " ; whether it be the up-blown powdery ashes of
distant volcanoes, or merely the dismal " smoke-nuisance "
of the world's workshop, dust is not wholly vile. For dust
is the heart of the beneficent rain, and in its gentle dropping
it has helped the earthworm to form the soil ; it has no
small share in making the sky blue above us ; and it adds
glory to the setting sun. Even if the east wind gloom,
so familiar in Britain, be due, as Lord Kelvin said, to " the
smoke of Europe moistened by the North Sea," against
this we must place the fact that without dust to form the
framework of the clouds, we should have no scenery in our
heavens.

THE EPHEMERIDES

ONE of the sights of the year, worth a long walk to see,
is the dance of the Mayflies or Ephemerides. Visit
in late May or in early June some likely stream slowly
flowing through the meadow, such a one as Longfellow wrote
of excellently —

" And silver white the river gleams,
As if Diana in her dreams
Had dropped her silver bow
Upon the meadows low."

It is best to go in the evening — to see the living cloud
rising from the water. Let us indulge in the dreamer's
power of synchronous vision, and see the whole life — the
long larval period of two or three years in the water, and
the short aerial love-dance lasting for an evening or two.
Long life indeed, but short love ; years of patience and
but a day of pleasure ; prolonged preparations, a climax,
and then the anti-climax of death. Biologically regarded,
the story of the Mayflies is simply one of the many variations
on the general theme of the antithesis between nutrition
and reproduction.

We see the eggs developing in the water — that was three
years ago — faintly stirred by the growing life within. We
think of them fancifully, lapped round about by the peaceful
stream ; but the facts do not tally with the fancy, for the
trout thin them sorely. The surviving embryos become
more aware of things — that much we may surely say.

Awakening from their rocking, they turn themselves in

233

234 THE BIOLOGY OF THE SEASONS

their cradles. Then the larvae creep forth, wash themselves
in the water, and hungrily fall upon their prey of still
smaller fry. The beautiful tracheal gills — we feel inclined
to call them water-wings — are spread out, and the air in
the water soaks into the blood with obviously invigorating
results. The larvae feed and grow and moult — a clearly
logical sequence ; they cast their cuticles time after time ;
they hide from the fishes.

At length there is the making of the wings and the
eventful emergence from the water. They cannot fly
much at first, for they are encumbered by a thin veil,
too truly suggestive of a shroud. They rest rather wearily
on the branches of the willows and on our clothes as we
stand watching them. We see them writhe and jerk, till
at length their last encumbrance, their " ghost " as some
entomologists have called it, is thrown off. Then the short
aerial life begins ; they swing to and fro as if in a dance ;
they dimple the smooth surface of the water with a touch
into smiling ; we see them chasing, embracing, separating.
There is great beauty in their film-like wings, in their large
lustrous eyes (of the males in particular), in the graceful
sweep of the long tail filaments.

They never pause to eat, they could not if they would.
Hunger is past, love is just begun, and in the near future
is death. The evening shadows grow longer — the shadow
of death is over the Ephemerides. The trout jump at
them, a few raindrops thin the throng, the stream bears
others away. The mothers lay their eggs in the water,
and after doing so many seem utterly spent, and die forth-
with. Here, as often elsewhere, reproduction is the be-
ginning of death, as well as of life. Cradle and tomb are
side by side. The males also pass, almost in a sigh, from
the climax of loving to the crisis of dying. Sometimes, as
the old entomologists said, not a single Ephemerid is left

THE EPHEMERIDES 235

" to sport in the beams of the morning sun." The eggs,
however, are in the water, and the race continues.

Turning homewards, the birds now silent, we cannot
help thinking of other Ephemerides — of patient larval
life, of metamorphosis, of shrouds angrily thrown aside
and wedding robes put on, of hunger that gives place to
love, of the sacrifice of maternity, of cradle and tomb
together. Yet we remember the promise of the future
beneath the surface of the unmoved river. The race con-
tinues. Under the horse-chestnut tree we tread upon the
petals which the wind has blown like white foam, but the
tree stands firm like that of Ygdrasil.1

1 In the above study, as also in those dealing with earthworms and
withering leaves, I have utilised some passages which I wrote and
published some years ago. I have to thank Mr. Murray for his kind
permission. The foundation of " The Ephemerides " will be found in my
Study of Animal Life, p. 106 (Murray: London, 1892).

BOOK III.— AUTUMN

837

BOOK III.— AUTUMN

IMPRESSIONIST SKETCH

THE life of plants and animals — and of man himself —
is rhythmic. Rest and repair alternate with work
and waste ; periods of hunger and self-increase are followed
by periods of love and species-continuing. There are
well-established internal rhythms, and these bear a relation,
partly of origin, and partly of present stimulus, to the
external periodicities of day and night, month and tide,
summer and winter. Just as the fatigue of evening and the
sleep of night express an external punctuation of an internal
rhythm, so it is with the decadence of Autumn and the rest
of Winter. The external changes — more oblique light,
a shorter day, increasing cold, and rising storms — act upon
living creatures which have, in the course of ages, become
predisposed to respond.

There is aptness in the usage which speaks of Autumn as
" the fall," for life then begins to go on the down-grade. It
is the ebb-tide of the year — a time of decadence. And it
is largely a matter of a diminished supply of solar energy ;
for just as it is the sun that quickens the seeds, raises the
sap, unpacks the buds, and opens the flowers, and our hearts
as well, in Spring, so it is the lack of sun that now casts a
spell upon life, putting the fires out and making us melan-
choly in the Autumn. It is the year's curfew and its
vespers. When the bells cease we know the silence for

Winter.

339

24o THE BIOLOGY OF THE SEASONS

I

Even the careless, who pause only for a moment to
Jisten to the curfew of the year, must perceive the sadness of
the notes, "Farewell and Death." They are heard in the
calls of the birds passing south who " wail their way from
cloud to cloud," in the rustle of the falling leaves, and in
the piping of a mournful wind which bears both birds
and leaves away. It is truly a time of withering and
decadence, of leave-taking and death.

But a more careful listener will hear very different
notes, which tell of the continuance of life in spite of death,
of preparation for the future amid the withering of the
present. The farewell that seemed for ever is for many
more accurately, " Au Revoir," " Auf Wiedersehen." For
the tide of life which has now turned in ebb is not one that
sinks sullen and empty from a rocky shore ; it is rather
like that which bears from some great seaport a fleet of
richly laden ships. The ebb of the year is the time when
fruits ripen, when seeds are scattered and sown ; it is not
an end, it is a new beginning. There is indeed stranding
and wreckage, as the dead birds among the jetsam tell
us plainly ; but the Autumn fruits are more characteristic.
They crown the plant's work for the year, and form the
cradles of next year's seedlings ; they protect the young
lives within the seeds, and also secure their dispersal.
Many of them harden, crack, and split like withered leaves,
which is just what many of them are ; others swell and
soften into succulence. The nectaries, through which
surplus sugars overflowed during flowering, forming feasts
of honey for the bees and other welcome visitors, have
now closed, and the sweetness is drafted into the ripening
fruit. Even the fragrance of the flower may be redistilled
in the flavour of the fruit, and the cheerful red glow of

IMPRESSIONIST SKETCH 241

the ripening apples is due to the same pigment as that in
the withering leaves of the Virginian creeper, or in the
gorgeous petals of the viper's bugloss, which is still erect
like a standard, amid the dead and dying on the moor.

The drops of water rise to the apex of the sunlit fountain,
enter for a brief moment into the formation of a rainbow,
and are hurried to the earth again. Such is life. The
organism rises to the crest of the wave, reaches its limit of
growth, and reproduces; then is hurried from the climax
of loving to the last crisis of dying. So all around us in
Autumn we see the little child Love, as in the world-famous
picture, holding the door against stalwart Death who
intrudes. The curfew tolls, the fires of life burn low, the
lights of love die out, the petals of the last poppy are shed,
the butterflies disappear with the sunbeams which danced
with the glistening leaves, Proserpina has perforce to go
down to Hades, — many a man and beast with her, — and
lowering storm-clouds draw a shroud over the earth. The
music of L' Allegro has died away ; hushed are Pan's merry
pipes ; there is no lilt of any bird ; II Penseroso begins to
prose : " Dun sky above, brown wastes around you are ;
from yon horizon dim stalks spectral death."

In Summer, in the abundance of life we saw death
harvesting ; in Autumn, in the midst of death, we are
impressed with the abundance of life. For Autumn is the
time of seed-scattering. The cotton-grass has unfurled
its white sails on the moor ; clouds of thistledown and
ragwort nutlets with equally dainty parachutes are swept
over the waste ; the hooked fruits of burdock, cleavers,
hound's tongue, and how many more, cling to our clothes
and to the sheep's fleece ; all sorts of pods and capsules
have opened, and gusts of wind — how much more the
equinoctial gales — have scattered and in many cases sown
the seeds. The prodigality is as unmeasurable as it is
16

242 THE BIOLOGY OF THE SEASONS

providential. These creatures have constitutions which
reproduce prolifically — prodigiously prolificacy, while
their forbears and cousins which were more economically
reproductive have all passed away. The survivors sur-
vive, but never fortuitously. In this set of cases which
we are considering, only those survived which had the
sufficiently prolific constitution. They survive, not only
because their constitution is strong, — that always counts
for much, — but because they are many ; and they are
many, primarily, because it is of the nature of simple
unsophisticated life to be abundant, to be prolific. It is a
stream which is always overflowing its banks. And so,
on this fine Autumn day, the harvest carts pass heavily
laden with sheaves, strong coveys of partridges darken the
stubble, the links are crowded with rabbits, the air is full
of whirling seeds, the fallow-ground is vibrating with
the gossamer threads of small spiders that have sunk to
earth and gone into hiding, the apples fall in showers in
the orchard, and we wonder, as men have wondered for
thousands of years, at the Abundance of Life.

II

It would be idle to deny that there is in Autumn — the
fall of the year — an irrepressible note of decadence ; it is
echoed in a whisper by the rustle of falling leaves. Bene-
ficent in their life, for all the plant's wealth is due to them,
they are beautiful in their dying. They have worked
themselves out, for it is more than a metaphor to speak of
the industry of the leaf ; liquid supplies are running
short, the sun's rays are fewer, the first shock of frost has
come, and the leaves must die. But before they die they
surrender to the plant all that they have still left that is
worth having. There is a retreat of particles down the

IMPRESSIONIST SKETCH 243

leaf-stalk into the stem. Thus the leaves fall virtually
dead, almost empty except of waste. They are like
empty houses from which the tenants have flitted, breaking
and burning some of the furnishings as they went, leaving
little more than ashes on the hearth. But Nature is ever
generous of beauty, and the dying leaves have a literal
" beauty for ashes." Theirs is a euthanasia, and if we
are at first inclined with the poets to weep with the wither-
ing, listening mournfully to " the ground- whirl of the
perished leaves of hope, the wind of Death's imperishable
wing," we must learn a deeper plant -lore, — that the leaves
which by their living have made the plant rich, make it
no poorer when they die; that their flush of death is a
prophecy of the petal's glory — for what is a petal but a
transfigured leaf ? and that even when fallen they may
serve as cradle-clothes for next year's seedlings. The
fact remains that just as the progressive life of the species
demands the death of individuals, and is within limits
unmoved thereby, so the forest-tree lives strongly on
though the leaves fall from its thousand branches. There
are those who cannot look upon the tree in its Autumn
glory without seeing the bare skeleton behind; but they
must learn to look longer, and then they will see that the
branches are already covered with next year's buds.

Ill

We hear another note of Autumn when we listen to
the calls of the migratory birds, as they pass overhead by
night, or congregate with excited clamouring before start-
ing on their southward journey. It is the note of autumnal
restlessness. Many little spiders show this, and pass from
field to field on silken parachutes, which the Germans
sometimes call " Der fliegende Sommer." There are also

244 THE BIOLOGY OF THE SEASONS

strange autumnal flights of certain beetles and moths,
the deer leave the heights for the low ground, and the
Greenland seal comes as far south as Scotland. Man
himself feels it, for many pilgrims at this season journey
southward " to warmer lands and coasts that keep
the sun." Some, we think, feel it strongly, perhaps in
deep organic reminiscence of ancestors who were wont
in Autumn to drive their herds to Winter quarters, or
launched their boats and made for the northern fiords to
reap their Winter harvest from the teeming waters. At
this season we have known one to walk miles, day after
day, simply to see the ships sailing out of the harbour,
and he could give no reason for the restlessness which
urged him. We can well believe that a habit begun, not
coercively from without, but as the expression of a con-
stitutional responsiveness to seasonal changes, might find
organic registration.

Most sensitive of all creatures to the breath of approach-
ing Winter — which they never face — and to hints of
scarcity, are the birds whose presence made the Summer
glad. Many are already gone, for the tide turned in
Midsummer ; " the last spent pulses of the great vernal
wave of migration have scarcely ceased to flow, before
the first ripples of the Autumn tide begin to be apparent/'
Many have slipped away, singly or in pairs, without a
good-bye ; others are still making up their minds, making
many " last appearances/' telling us excitedly day after
day, " We are going, we are going."

That they should go we do not wonder, for the leaves
are fallen from around their old shelters, the fruits have
been gathered or scattered, the seeds are sown, most
insects are dead or in safe resting-places, the daylight is
short for picking up the scraps of life that remain within
reach, it is becoming colder every week. We draw our

IMPRESSIONIST SKETCH 245

cloak about us shiveringly, as we wish the last migrants
" Bon voyage ! "

The history of this remarkable habit is wrapped up
with the evolution of climates ; thus many see in the
autumnal retreat a reminiscence of the Ages of Horror
which made whole faunas shudder — the Glacial Epochs.
The impulse to migrate perhaps expressed originally
what we have called a constitutional responsiveness to
seasonal change ; it seems now to be inborn or instinctive,
though it may still require the stimulus of the outer world
to pull the trigger. Moreover, after we have allowed all
we dare allow to the experience of successive years, to
the education of juniors by seniors, to a kind of social
tradition in the case of those that migrate in great squadrons,
we have still to fall back on the theory that a sense of
direction, developed in many animals, not yet wholly lost
in Man, has been brought to perfection in birds.

Of all pilgrimages — and there are many animals who
travel, such as reindeer and lemmings, whales and seals,
salmon and herring — this of birds is certainly the most
marvellous. Picture the rush of the feathered tide, spread-
ing sometimes for many square miles in the heavens, con
tinuing day after day without interruption

" Who can recount what transmigrations there
Are annual made ? What nations come and go ?
And how the living clouds on clouds arise ?
Infinite wings! till all the plume-dark air,
And rude resounding shore, are one wild cry."

Think of the velocity of the flight, an exaltation of
the bird's usual powers, perhaps reaching a hundred miles
an hour. Consider the extent of the flight, the dot-
terel passing from the North African steppes to the Arctic
tundra, the Virginian plover passing from Labrador to
North Brazil. Notice the breadth of the flying phalanx ;

246 THE BIOLOGY OF THE SEASONS

thus that of gold-crests has been known to strike our coasts
simultaneously from the Channel Islands to the Shetlands.
The altitude is also noteworthy, for many birds migrate at a
great height. Contrast the "wild mad rush" of Spring,
when the birds fly on the whole northwards, north-east-
wards, and north-westwards, at their utmost speed, by the
shortest route, and almost without a break, as if love called
them clamantly, with the less urgent westerly and southerly
flight in Autumn, when the young birds, reversing the Spring
order, are the first to leave. Nor forbid the shadow
which falls over the picture, but remember of the birds as
they fly that theirs is by no means always " a pleasant path
in the wake of retreating Summer or in the van of advancing
Spring," for migration is the great effort of their life, and to
many it is the last. For the elimination which must have
been raising the standard of racial fitness through the ages,
since migration began, by weeding out the inept and the
feckless, the dull of sense and the foolhardy, is still a dread
reality. But must we not confess that the swallow flying
south is " too wonderful for us " ?

IV

Some one has defined life — with autumnal melancholy —
as a slow dying. For, apart from the quasi-immortal Protists,
whose simplicity makes its possible for them to make good
their waste by constant and perfect repair, organisms always
tend more or less rapidly to get into physiological arrears.
Autumn is the time for balancing accounts, and then Death
often claims what Love has placed in pawn. Thus, of the
wasps whose nuptial flight we observed one of those harvest
days, the drone-lovers are already dead, their mates have
found sheltered nooks for their maternal and hibernal
slumbers, and the residue, almost automatic Spartans, have

IMPRESSIONIST SKETCH 247

urned out all the remaining grubs from their cradles, and
are themselves awaiting death in the first night's frost.

Life has also been defined as a struggle to avoid death,
or as an effort towards continuance, and here again there is
truth. For apart from parasites, who live the drifting life
of ease, continuance means effort and struggle between the
poles of love and hunger. And we undoubtedly miss part
of the Biology of Autumn if we do not recognise it as a time
of preparation for continued life.

The plant has been storing all Summer, and now the
reserves are all passifig from the more perishable parts, from
leaf to stem, from stem to root. There are stores in many
buds, well protected by scales which, themselves dying
away, save the delicate life within ; there are stores in
seeds, similarly protected by dead husks ; and so it is with
tuber and root-stock, corm and bulb, all are stores.

The beavers store branches cut into convenient lengths,
the squirrels store nuts, the field-mice grain, the moles earth-
worms, and so on through a long list. Many insects store
provender for offspring which they will not survive to see.
Some ants store grain, biting at the embryo and thus
preventing germination ; others chew grain and store it in
biscuit form ; a few take their cows — the Aphides — with
them into Winter quarters. It is said that hive-bees become
lazy in countries where there is practically no Winter, which
corroborates the suggestion that the success of North
Temperate peoples is partly due to that discipline in fore-
sight, as well as to the emphatic punctuation of life, which
the marked seasonal changes impose.

Autumn is the evening of the year, the beginning of rest,
the curfew, as we said ; and we must correct the oppressive
vision of a dying world with a thought of the reparation
which is given in sleep. The trees, some of them already
bare, the inert buds formed some months ago on the boughs,

248 THE BIOLOGY OF THE SEASONS

the seeds buried in the ground, the chrysalids hidden in
quiet resting-places, the eggs and larvae under still waters,
the lethargic frogs in the mud of the pond, the reptiles and
mammals who have found their winter nests — they are
not dead but sleeping. They await the good-morning of
another spring, and though to some this never comes, of
most it may be said that if they sleep, they shall do well.

" As is the world on the banks, so is the mind of man," —
it has its seasons too ; and no one at all sensitive can avoid
a suggestion of sadness in Autumn. For some, indeed, this
is apt to sink into pessimism. Of this as a philosophical
system, the biologist has, of course, nothing to say, but he
maintains that those who find only pessimism in Autumn
have been but partial students of the season, and he fancies
that this may be true of even larger things. He would rest
on the fact that the tree stands while the leaves fall, that
there is fruition in the midst of decadence, and continuance
of life in the midst of death. He knows that the apparent
" Vergehen " is the condition and the beginning of a new
" Werden." Even in dying he may have the joy of seeing
as much as he wants of himself living on in his children.
His vision of the past shows a cumulative progress of things,
and gives him a sustaining hope for the future ; and his
evolutionary postulate that there is nothing in the end
which was not also in the beginning, expresses his speech-
less faith that in the beginning was the Logos.

We have spoken of Autumn as the curfew of the year
partly because of the covering-up of many vital fires that is
then enforced, and partly also because of a memory of curfew
bells we used to hear in a country village long ago, which
seemed always to sadden and gladden in alternate notes —

IMPRESSIONIST SKETCH 249

saying, " Night and Morning, Death and Life ; Night and
Morning, Withering and Sowing ; Night and Morning,
Weariness and Rest ; Night and Morning." This was a
fancy, perhaps, as regards the bells, but it is a fact as regards
Autumn.

Climb the hill above the village, and watch the sun set
over the withering woods. Look out over the sea of gold,
mingled with fire, and broken by dark rocks which you know
to be pines. Accept the withering, but see also the harvest-
fields ; even on the bare boughs there are buds. Hear the
birds pass overhead, quite a babel of good-byes sometimes,
but many at least will return. Watch the seeds drift off the
dead plants as the wind sighs along the hillside, and know
that the race continues. Look Death in the face, and try to
see that he is, on the whole, kindly and wise.

Wait till the colours pale in the short twilight, till the cows
are driven home lowing, till the sheep are herded off the
exposed moorland lest snow come in the darkness, till the
birds that remain cease to call, till the lamps are lit in the
cottage windows. Wait on till the curfew tolls, till the lights
are put out one by one, — then know the rest and silence of
Autumn.

" Ueber alien Gipfeln
1st Ruh

In alien Wipfeln
Spiirest du
Kaum einen Hauch ;
Die Vogelein schweigen im Walde»
Warte nur, balde
Ruhest du auch."

THE FALL OF THE LEAF

LATE Autumn, which marks to many of us the beginning
of Winter work and Winter pleasures, means to the
wide world of life an ebb-tide — sometimes, indeed, a period
for rest and recuperation, or, as is often the case, a time for
dying, but always an ebb-tide. And one of the impressive
and extraordinarily beautiful signs of this, more striking
than the homing of the birds or the hibernation of mammals,
is the fall of the leaf — the index to the fall of the year. So
it is worth thinking awhile over the familiar sight of the
withering and falling leaves.

We have seen that the life of the plant is tidal ; it sets
in with a flood in Spring, manifesting itself in growth of
stem and exuberance of foliage ; it rises to the high-water
mark, and turns in Summer when the blossoms burst and
the flowers shine forth ; it is well on the ebb by Autumn,
bearing on its breast all manner of ripe fruits and seeds,
potent treasures to be cast on the shores of another Spring.
Each of these tidal periods, one may say, has its character-
istic colour : green and gold are the colours of young
Spring ; orange, red, and purple mark the full splendour of
Summer flowers ; and Autumn, with its flame-like, often
blood-like, withering leaves, rivals all that has gone before.
Is it not true to say that the ebb-tide gleams with the
glare of burning wrecks ?

Throughout the Summer the leaf has lived an intense
life, far more intense than we are inclined to give plants
credit for, building up with the aid of the sunlight no small

THE FALL OF THE LEAF 251

quantity of sugar and more complex carbon-compounds,
which are laid up in reserve in various parts of the plant.
In Autumn, however, the vitality is checked ; the move-
ments of the sap become very slight ; and the leaves begin
to die. It is partly that they are in some measure worn
out by the Summer's work, just as the bees are ; it is partly
that the physical world has changed. It is well that they
should die, lest they begin to undo what they have so well
done.

But before they die they behave in a beautifully adaptive
way. They surrender to the plant that bears them all the
residue of their industry that is worth having. There is a
gentle current of sugar and more complex things, even, they
say, of the subtler wealth of living matter, which ebbs from
the dying leaf into the stem before the breath of approach-
ing Winter.

The leaf, useful in dying as well as in living, becomes
more and more empty of all but waste, and as the retreat
of valuable material into Winter quarters is being accom-
plished, there is also preparation for the actual fall. Across
the base of the leaf-stalk, in a region which is normally
firm and tough, there grows inward a partition of soft
juicy cells, actively multiplying and expanding into a
springy cushion, which either foists the leaf off, or makes
the attachment so delicate that a gust of wind will soon
snap the bridge binding the living and the dead. This is
fine surgery, that the scar should be ready before the opera-
tion is performed. The more we look into the matter the
more we see how perfect are the adaptations connected
with the fall of the leaf.

Virtually dead the leaves now are, empty houses, all
dismantled, with little more than ashes on the hearth. But
these ashes — how glorious! for in yellow and orange, in
red and purple, in crimson and scarlet, the withering leaves

252 THE BIOLOGY OF THE SEASONS

shine forth. They are transfigured in the very article of
death, in the low beams of the Autumn sun.

One of the most interesting interpretations of the yellow
colour of many leaves in Autumn (and also of the pale
yellow — etiolation — of newly unfolded leaves in Spring)
is in terms of economy of material. Pure green chloro-
phyll contains carbon, hydrogen, oxygen, nitrogen, and
magnesium ; the yellow colouring-matters contain only
carbon, hydrogen, and oxygen. Thus, " by keeping back
the green chlorophyll in the Spring and reabsorbing it in
the Autumn, a saving would be effected in nitrogen and
magnesium, which are of great value to the plant."

Professor Stahl in particular has worked with this
interesting theory, for which there is considerable evidence.
When a leaf just about to turn yellow is taken from the
plant and kept in a moist chamber it remains green, while
its neighbour on the plant has changed to yellow. There
seems to be a migration of the green chlorophyll. When
the veins connecting a corner of leaf with the midrib are
severed, the corner remains green, while the other parts
remaining in connection with the main conducting vessels
change to yellow. Chemical analysis has shown that in
the yellow leaf, as compared with the green leaf, there is a
reduction in the amount of potassium, nitrogen, phosphoric
acid, iron, chlorine, and silica.

Sometimes it is the double green pigment — the chloro-
phyll— of the leaf that breaks up, forming little heaps of
yellow grains, and the leaves are golden. Sometimes, on
the other hand, amid the flux of molecules in the dying
leaf, there appears a special decomposition product —
anthocyanin, which along with the acids so often present
stains the leaf with red, or without the acids gives us
bluish purple, or along with the yellow grains above
mentioned shines out in gorgeous orange. It goes without

>€••>» » r

THE FALL OF THE LEAF 253

saying that the details of the process are intricate, and
that they vary considerably from plant to plant.

Finally the leaves fall gently from the trees, or after
writhing and rustling in the wind, as if loath to be separated,
are violently wrenched off and whirled along the ground.
Who can help hearing in this ground-whirl of perished
leaves " the wind of Death's imperishable wing " ? But
although we cannot ignore the curfew of the year, tolling
insistently in October, we recognise that the tree is not
really impoverished by the yearly loss of its leaves, while
they, on the other hand, weathered, faded and torn, and
mouldered by fungi, are buried by earthworms, to form,
with the help of bacteria, the vegetable mould in which
are born the seedlings of another year.

When we look back on the full Summer tide, Autumn
seems indeed to be bare and sad, especially in northern
countries. The fields are stripped ; the hedgerows are
silent ; withered grass, blackened herbage, and leafless
boughs contrast almost painfully with Summer's pageant.
But it is well to make the most of the present — to go before
it is too late to some height among the woods and watch
the waves of colour splashing in the wind. Let us gather
some browned bracken, lighten it up with leaves of oak and
rowan tree,, brighten it with a branch of a bramble, throw
in Virginian creeper and vine if we have them, and let us
recognise with gladness the persistent glory of the year.

Let us look forward, too, and see how the withering
leaves often prophesy the splendour of future flowers,
and recognise that the leafless boughs are only resting,
husbanding their strength for the triumphal outburst of
Spring. The buds are already there, the vigour of the
leaves that have fallen has given them their initiative.

The leaves live and die for the plant, which is enriched
by their Summer's work, and saved by their Autumn fall.

254 THE BIOLOGY OF THE SEASONS

And in their death, which seems to us very beautiful, we
see an expression of fundamental facts which have their
application to ourselves, that the life of the species requires
the death of individuals, that sacrifice is essential to progress,
and that while the leaves fall from its many branches the
tree of Life lives strongly on.

SHOWERS OF GOSSAMER

WE read of the Indian conjuror who throws a rope
into the air and climbs up it, but we can see spiders
actually doing something of this sort. It is especially,
though not by any means exclusively, in the Autumn that
threads of silk may be seen floating in the air, just visible
when the sunlight makes them glisten, or entangled in
incredible numbers on hedgerows and among the herbage.
Sometimes as we walk over the links and stoop down to
look along the short grass, we see that it is quivering with
myriads of silken lines, — the fallen threads of gossamer,
often iridescent in the sunlight.

The Germans sometimes call it " Der fliegende Sommer,"
and the French "Fil de la Vierge," and there is possibly
in the name gossamer an even more poetical suggestion.
But it is fine enough in itself to dispense with uncertain
etymological decorations. Of the fleeting Summer it is
indeed a hint, but it seems to occur in Britain at almost
every season, when there is fine clear weather.

Gossamer showers have attracted attention from early
times; thus Pliny records how it rained wool about the
Castle Carissa, and now and again they occur on such a
large scale that they force themselves on the attention of
the most careless. A good example is recorded in Gilbert
White's 23rd Letter : —

" On the 2ist September 1741, being then on a visit,
and intent on field diyersions, I rose before daybreak :
when I came into the enclosures, I found the stubbles and

355

256 THE BIOLOGY OF THE SEASONS

clover-grounds matted all over with a thick coat of cobweb,
in the meshes of which a copious and heavy dew hung so
plentifully that the whole face of the country seemed, as it
were, covered with two or three setting-nets drawn one over
another." The dogs could not hunt, " their eyes were so
blinded and hoodwinked that they could not proceed."

" About nine an appearance very unusual began to
demand our attention, a shower of cobwebs falling from
very elevated regions ; and continuing without any in-
terruption till the close of the day." These webs were not
single filmy threads, however, but " perfect flakes or rags."
" On every side as the observer turned his eyes might he
behold a continual succession of fresh flakes falling into
his sight, and twinkling like stars as they turned their
sides towards the sun."

In most cases the natural history of gossamer is as
follows : Young spiders and small spiders of a good many
different kinds seem to become restless in the Autumn.
They mount on the tops of plants, on fences, on the hand-
rail of a wooden bridge and the like ; they stand on tiptoe
with their head facing the gentle currents in the air ; they
emit from their spinnerets fine separate threads of silk.
They stand on tiptoe, but keep firm hold until the threads
of silk floated out on the breeze (if one may say so) are
sufficient to bear them. Then with a vault they let go,
and are borne by the gentle currents often to great distances.

They have, of course, no power of directing their move-
ments, but it seems likely that they can add to their
parachutes (setting more sail) or coil it up in part (taking
in a reef), so that they float farther or sink gently to the
earth, as the case may be. When tens of thousands of
small spiders do this on some suitable Autumn day, we
see a flight or shower of gossamer. Some of the spiders
— many different kinds indulge in ballooning — are borne

SHOWERS OF GOSSAMER 257

far — often, doubtless, too far. Thus Darwin noted that
huge numbers were carried on board the Beagle when it
was sixty miles off shore. There are other spiders, how-
ever, which cannot make long journeys, and do not rise
high off the ground. Professor Miall has observed that
gossamer in the air is always preceded, as well as followed,
by gossamer on the ground. A further study of gossamer-
making British spiders is much to be desired.

In his fine work on Spiders (1890), Dr. M'Cook
notes the interesting fact that the essential explanation
of gossamer was discovered in 1716 by a boy of twelve,
Jonathan Edwards, who afterwards became famous in
other connections — as an author, for instance, of a treatise
on The Freedom of the Will. He saw and figured the
" flying spiders/* and seems to have clearly understood
that the aeronaut was supported by the silk, and that it
was borne by currents. " If there be not web more than
enough just to counterbalance the gravity of the spider,
the spider, together with the web, will hang in equilibrio,
neither ascending nor descending otherwise than as the
air moves; but if there is so much web that its greater
rarity shall more than equal the greater density, they will
ascend till the air is so thin that the spider and web
together are just of an equal weight with so much air."
Which is not amiss for a boy of twelve. Nor is his note
on the silk itself : " Seeing that the web, while it is in the
spider, is a certain cloudy liquor with which that great
bottle tail of theirs is filled, which immediately, upon its
being exposed to the air, turns to a dry substance, and
exceedingly rarifies and extends itself."

Some details of one of the most remarkable phenomena

in Nature have been furnished by trustworthy observers

and experimenters, who have followed up the excellent

beginning made by the boy Jonathan Edwards. Gilbert

'7

258 THE BIOLOGY OF THE SEASONS

White wrote in 1775 : " The remark that I shall make on
these cobweb-like appearances, called gossamer, is that,
strange and superstitious as the notions about them were
formerly, nobody in those days doubts but that they are
the real production of small spiders, which swarm in the
fields in fine weather in Autumn, and have a power of
shooting out webs from their tails, so as to render them-
selves buoyant and lighter than air."

Inquiring into the problem why what rises should again
sink, he says : " If I might be allowed to hazard a sup-
position, I should imagine that those filmy threads, when
first shot, might be entangled in the rising dew, and so
drawn up, spiders and all, by a brisk evaporation into
the regions where clouds are formed ; and if the spiders
have a power of coiling and thickening their webs in the
air, as Dr. Lister says they have, then, when they were
become heavier than the air, they must fall."

Very interesting, in its mixture of keen observation
with a slight laxity of analysis, is the concluding paragraph
of the twenty-third letter. One quotes it, quite naturally,
as if it were a sacred book. It is certainly one of the
Pentateuch of " Nature-Study."

" Every day in fine weather, in Autumn chiefly, do I see
those spiders shooting out their webs and mounting aloft :
they will go off from your finger if you will take them into
your hand. Last Summer one alighted on my book
as I was reading in the parlour ; and, running to the top
of the page, and shooting out a web, took its departure
from thence. But what I most wondered at was, that it
went off with considerable velocity in a place where no air
was stirring ; and I am sure that I did not assist it with
my breath : so that these little crawlers seem to have,
while mounting, some locomotive power without the use
of wings, and to move in the air faster than the air itself,"

SHOWERS OF GOSSAMER 259

Dr. H. C. M'Cook, who has contributed so much in a
charming way to our knowledge of North American spiders,
gives a precise account of the spider's position during the
ballooning; and it is interesting to notice, as he points
out, that here again the gist of the matter was accurately
observed by Master Jonathan Edwards. " As the spider-
ling vaults upward, by a swift motion the body is turned
back downward, the ray of floating threads is separated
from the spinnerets and grasped by the feet, which also
by deft and rapid movements weave a tiny cradle or net
of delicate lines, to which the claws cling. At the same
time a second silken filament is ejected and floats out
behind, leaving the body of the little voyager balanced
on its meshy basket between that and the first filament,
which now streams up from the front. Thus our aeronaut's
balloon is complete, and she sits or hangs in the middle
of it, drifting whether the wind may carry her."

Dr. M'Cook makes a useful suggestion in regard to the
shreds and flakes often seen floating or sinking down
without any spiders about them. " In many, perhaps
in most, cases a number of feints are made before ascent.
A spider will take due position and spin out a thread ;
but it fails to mount aloft. Other unsuccessful attempts
follow, each producing a filament. These, while waving
to and fro in the eddying air, are often tangled together
before they are whipped off. Others again are united in
the air after release."

As we have seen, the Natural History of gossamer has
been in great measure cleared up. There is still much to do
in the way of filling in details, but in a general way we can
describe how gossamer is made and how it comes to be as it
is. It must be frankly confessed, however, that we do not
understand the biological significance of what we are able to
describe. It may be that these young spiders are dispersing,

260 THE BIOLOGY OF THE SEASONS

as young creatures tend to do, from the parental home, where
there is no longer room for them. It may be that the pinch
of hunger is making itself felt. It may be, on the other hand,
that there is an element of play and even adventure in the
business. We use the word "adventure" advisedly, for
spiders are alert, intelligent, original, individualistic creatures,
very different from ants and bees, and other oversocialised
creatures of instinctive routine. Once more, it is possible
that the ballooning may be, to some extent, like letting off
steam ; it may be that certain conditions induce an over-
production of silk ; this has to be got rid of, and some spiders
get rid of it in a highly original way. But we are not
trying to obscure our admission that we do not know the
biological significance of gossamer.

In any case, the extraordinary beauty of gossamer remains
a fact. Every alert person who has seen a long stretch of
golf-course, or acres of ploughed land, or a piece of moor,
or half a mile of hedgerow covered with gossamer, must
have admired the sight. The admiration grows when the
gossamer is bediamonded with dew or silvered with the frost,
or when the sun makes rainbows among it. It is one of the
most beautiful things in the world ; and when the threads
along the ground sparkle and vibrate, the earth seems to be
quivering, like a living thing, as far as the eye can reach.
It seems like an emblem of the intricacy of the threads in the
web of life. It recalls insistently Goethe's famous words
about Nature — " 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."

THE SIGNIFICANCE OF PALOLO

ONE of the most striking illustrations of the rhythmic
swing of life is to be found in the story of the " Palolo "
worms, which, briefly told, is somewhat as follows. Among
the crevices of the coral rocks around Samoa and Fiji and
some other Pacific islands, there is a very common greenish
sea-worm,scientificallynamed£>wmc^ym^'s, popularly Palolo.
In October and November every year, on or near the day
of the last quarter of the moon, there is an extraordinary
breeding swarm, and the waters are green with worms.
The swarming sets in just before sunrise, and often lasts for
less than half an hour. The numbers are past all con-
ception. The water is so thick with worms, Professor Hickson
says, that one cannot see down below two or three inches.
Professor Alexander Agassiz compared the sight to a great
area of thick vermicelli soup. It is a red-letter day for the
natives, who collect the delicate creatures in vessels and have
a great feast, as their forbears seem to have done for many
generations. It is said to be a red-letter day for the land-
crabs also, who arrange at that time to visit the worm-
strewn beach. What does it all mean ?

To understand it, we may begin near home by noticing
that in some of our British shore-worms, such as the re-
splendent Nereis virens, a remarkable change occurs in the
body at the breeding season. So striking is the transforma-
tion in some instances, that the breeding (" epitokous ")
phase has been mistaken for a distinct species. In some

forms the change affects only a part of the body, the posterior

261

262 THE BIOLOGY OF THE SEASONS

part becoming dilated and embellished, so that the animal
as some one has put it, is like a caterpillar in front and like a
butterfly behind. In many species, especially in the family
of Syllids, part of the body, laden with germ-cells, is set adrift
at the breeding-season, and, after swimming about for a while,
breaks up in the waters. This is what happens with the
palolo.

For the strangest feature of the palolo-swarm is not in
the enormous numbers — since the shore abounds in prolific
animals ; nor in the regularity of occurrence — since Nature is
full of these subtle rhythms ; nor in the fact that these
burrowers among the coral should be swimming in open
water, in a pelagic agony rather than a pelagic existence
(as Professor M'Intosh puts it) — since many shore-animals
have a pelagic or semi-pelagic phase in their life-history ; but
surely this, that all these writhing worms are headless. In
the most literal sense, they have all lost their heads ; they
are not worms, but parts of worms — the detached posterior
portions laden with germ-cells.

The story of the Pacific palolo is so extraordinarily
diagrammatic that no apology is needed for re-emphasising
its biological significance by noticing what happens with its
congener at Tortugas, Florida, Eunice fucata, the " Atlantic
palolo/' Dr. Alfred G. Mayer, who has made a great stride
by his studies in the intimate physiology of jelly-fishes, has
given a fine sketch of the annual event.

" The habits of the ' Atlantic palolo ' are quite similar
to those of the palolo worm of Samoa and the Fiji Islands.
The worms are, however, specifically different, the Atlantic
palolo being Eunice fucata Ehlers, and the Pacific worm
E. viridis Gray. Moreover, the annual breeding-swarm of
the Pacific palolo comes upon or near the day of the last
quarter of the moon in October and November, whereas the
Atlantic palolo swarms within three days of the day of the

THE SIGNIFICANCE OF PALOLO 263

last quarter of the moon between 2gth June and 28th

July."

The Atlantic palolo worms live within the crevices of
coral rock below the low-tide level. When mature they
are about 10 in. long and like thick string in girth.
Before sunrise on the morning of the day of the annual
breeding-swarm, the worm crawls out backwards from its
burrow and protrudes the sexual segments, which exhibit
a screw-like twisting and break off at a particular point.
" On being set free, they swim vertically upward to the
surface, where the posterior end of the worm continues
to progress rapidly along, moving backward."

The male " ends " are salmon red or dull pink ; the
female " ends " are greenish-grey or drab — the sex-contrast
eking itself out in colour. If an end be cut, each piece
continues to swim backward with its characteristic rolling
movement. Normally each worm — if we can call it a worm
— pursues its own course, " without regard to its fellows of
either sex" ; and they may be so abundant " that hardly
a square foot of the surface above the coral reefs at Tortugas
was free of a worm."

" When the sun is about to rise, and the first faint rays
of light fall over the ocean, the worms begin to contract
violently, so that the sexual products are cast out through
rents and tears in the dermo-muscular wall, and the torn
and shrivelled cuticula sinks down to die upon the bottom.
Light is not the sole, but only a contributory, cause of this
muscular spasm of contraction. . . . Any mechanical
shock will bring about an instant bursting of the worm,
the females being far more sensitive than the males."

" After casting off its posterior sexual segments, the
anterior part of the worm crawls back into its burrow and
regenerates a new sexual end. Only the mature worms cast
off their posterior ends ; the immature worms take no part

264 THE BIOLOGY OF THE SEASONS

in the swarming reaction." Now we begin to realise the
true inwardness of the phenomenon. At first we were
inclined to see, what is so obvious at many levels both
in plants and animals, that the beginning of new lives
means the waning of the old. But what we have is a
quaint suggestion of the little child Love holding the door
defiantly against the entrance of stalwart Death.

For the whole point of the palolo-swarm is that it
illustrates an evasion of the death-penalty on reproduction.
The trend of things says, as it were, to the Eunice, in the
origin of a new generation the parent must sacrifice itself.
But the palolo has answered back, which is the prerogative
of life, transcending all materialisms — has answered back
effectively, by the extraordinary adaptation of parting
with no small part of its body, and yet living on. In the
face of the trend of things, it hurls the defiance " Non
omnis moriar," and it still keeps true to its boast. And
this is Life — an automatism that can rebel.

The Pacific palolo swarms, as has been noted, upon or
near the day of the last quarter of the moon in October and
November ; the Atlantic palolo has its principal swarm
within three days of the day of the last quarter of the
29th June to 28th July moon, but the worm sometimes
responds to the first as well as to the last quarter of the
moon ; the Japanese palolo swarms in the Tokyo river at
the time of the new and the full moon.

Dr. Mayer has tried to discover the nature of the
stimulus to which the Atlantic palolo responds when it
swarms. He put some rocks with worms in them in a
scow-shaped live-car, which was floated, half-full of water,
on the sea. Thus an artificial " tideless sea " was arranged,
and the interesting result was that four out of eleven worms
swarmed normally.

" In nature all of the mature worms swarm at the

THE SIGNIFICANCE OF PALOLO 265

annual breeding-time, and this partial failure of the worms
to swarm may indicate that the changing pressure due to
rise and fall of tide over the reefs is a contributory, but
not a necessary, component of the stimulus which calls forth
the breeding-swarm. It is more probable, however, that
confinement within the wood-inclosed space of the live-car
and the lack of perfect circulation of water acted as a partial
preventive of the swarming, and that the reaction is wholly
independent of the rise and fall of the tide. In any event,
it is evident that the worms can swarm normally in a
tideless sea, and that rise and fall of tide is not a necessary
or sole cause of the swarming."

On the other hand, when the scows were provided with
light-tight wooden covers, so that the moonlight was kept
off, none of the worms swarmed. It seems, therefore, that the
worms require the stimulus of the moonlight. " In nature
the worms will swarm in overcast or cloudy weather, so
that even diffuse moonlight appears to be capable of calling
forth the breeding-season." We have here, therefore, a
striking instance of a constitutional change that is, so to
speak, punctuated by an external periodicity.

Dr. Mayer calls attention to another very interesting
aspect of the phenomenon. In the Atlantic palolo the
annual breeding-season is only of one to six days' duration,
and the males outnumber the females in the ratio of about
three to two ; whereas in Nereis, where the breeding-season
is fully one hundred days long, the males greatly outnumber
the females. "It is evident that a shortening of the
breeding-season would cause a greater concentration of
breeding individuals, and would therefore permit of a
relative decrease in the number of males and a corresponding
increase in the number of females ; for, whenever a female
swarms, it is important, for the preservation of the species,
that there should be a male near her to fertilise her eggs.

266 THE BIOLOGY OF THE SEASONS

If the breeding-season be of long duration, the males must
greatly outnumber the females to secure this fortuitous
proximity ; but if all of the females swarm within a few
days, very much fewer males will suffice to accomplish
this purpose."

" We have advanced beyond the period in the history of
biology when one had but to discover an advantage to
determine a cause ; but that some such cause may have
contributed to shorten the breeding-season in such animals
as the Atlantic, Pacific, and Japanese palolo worms is
shown by the fact that more eggs are fertilised when males
are near the female than when they are far away."

Thus we find in the palolo a fine instance, on the one
hand, of evading the penalty so often imposed on repro-
duction, and, on the other hand, of securing prodigal
multiplication while economising reproductive expenditure.

AUTUMN FRUITS

A LTHOUGH autumnal changes are the beginning
jT\ of the end to annual plants and animals, and
involve a check to the vitality of many others that are
longer lived, there are other processes which work in a
life-preserving direction. There are preparations for the
Winter, such as the laying up of stores inside the bodies of
plants and animals, or outside the body as well in the case
of animals ; and there are preparations for next year, such
as the completion of bud-making or the regrowth of
damaged feathers. One autumn night we sat looking
down on the village from the hill above, and as we watched
all the lights were put out one after another, though some-
times it was simply that the blinds were drawn and the
shutters closed ; we felt that the day was indeed over ; but
as we looked longer, there rose in our mind the picture
of banked-up fires, of things set in order for the morning,
and of other preparations for a new day, besides the chief
preparation of rest. It is the same in the household of
Nature. When we turn to fruits, however, we have to do
with preparations, not for the individual, but for the
continuance of the race. In a sense they crown the plant's
work for the year, but their significance is not individual.
They protect and scatter the seeds, but all that is in them
is loss to the individual plant. In the organic see-saw
between nutrition and reproduction, fruiting is the extreme
uplift of the reproductive end.

A fruit, regarded structurally, is the part of the flower

267

268 THE BIOLOGY OF THE SEASONS

that persists after pollination has been effected — that is to
say, after the possible seeds or ovules have become real
seeds. In most cases a fruit may be described as the
ripe seed-boxes, or as a collection of ripe seed-boxes, with
or without extra parts, such as the fleshy top of the flower-
stalk or a persistent calyx. In some cases, as in common
cereals, where a single seed fills the seed-box, fruit and
seed are practically identical, though the theoretical
difference remains clear. In order to understand the
different kinds of fruits, which represent different solutions
of a very interesting problem, we must also notice that
the wall of the fruit (the pericarp) often consists of several
layers, very different from one another. Thus in the
familiar case of a plum there is the firm outside skin
(epicarp), which keeps bacteria and moulds out until it
gets even a slight wound ; there is the fleshy pulp (meso-
carp), which is all loss to the parent plant, but attracts
the birds, which scatter the seeds ; and there is the very
hard "stone" (endocarp), which effectively preserves
the seed within — a living embryo — from being digested
in the bird's food-canal, from being frost-bitten in the
ground, from premature germination, and from other
risks.

The use of the fruit is to secure a measure of success for
the seeds ; but this requires analysis, (i) The seed is an
embryo plant with a legacy of nutritive material ; it grows
within the ovule from a microscopic egg-cell fertilised by
a pollen-grain ; it is, for a time, a very delicate young life.
One use of the fruit is to protect the developing seed from
bad weather. (2) Even when the seeds are fully formed
and have attained to great tenacity of life, there is need
for the fruit's protection, for instance, against small seed-
eating animals, such as boring beetles, or against larger
creatures, such as birds and rodents, which devour and

AUTUMN FRUITS 269

digest the seeds. (3) Not less important is the part the
fruits play in seed-scattering — which we propose to discuss
by itself — whether by explosion, or by adhesion to animals,
or by the formation of parachutes, or otherwise — including,
of course, by being themselves eaten ! (4) But even when
the seed has been successfully scattered and sown it may
require the fruit's protection in the ground. It may
not be ready to germinate, or the season for germination
may be many months ahead. The enclosing fruit, or its
innermost wall in many cases, may protect the seed from
the frost and from the appetite of many small animals
that work underground.

It is almost impossible to avoid using phrases which
suggest foresight on the plant's part, or some deliberate
fashioning of the fruit — which is of no use to itself — so as
to secure seed-scattering and seed-protection. But, while
the fact of adaptation is certain and becomes more and
more impressive the more we penetrate into its details,
and while it may be necessary to postulate a certain
primary adaptiveness in living creatures — a capacity for
effective response to stimuli and of effective creation of
what is new — we cannot, of course, imagine that the plants
take thought for the morrow or for the future of their
race, even in the most figurative sense. We must look
at the matter in a different way. Those plants that, for
constitutional reasons of their own, varied in the direction
of having effective fruits were the plants that survived.
Those plants that, for constitutional reasons of their own,
did not vary in the direction of having effective fruits
were eliminated from their place in the Earth's Flora. It
is a useful biological dictum that nothing succeeds like
success ; for when a plant, aiming at no mark (save, perhaps,
its own organic equilibrium and self- increase), made a
hit in the direction cf an effective fruit, it would have

270 THE BIOLOGY OF THE SEASONS

great success with its seeds, and its valuable idiosyncrasy
would be handed on, for subtle reasorjs perhaps aug-
mented, to an ever-increasing body of descendants.

Turning now to the many different kinds of fruits, we
must, from a general biological point of view, regard the
great diversity as an interesting illustration of the variety
of solutions that may be offered to one vital problem.
Linne recognised five different kinds of fruits, and Lindley
thirty-six ; but as this is not a botanical treatise, the smaller
number will suffice. First, there are the box-fruits, or
capsules, dry in character, and liberating the contained
seeds. Poppy-heads and pea-pods at once suggest them-
selves as examples. Second, there are splitters, or schizo-
carps, also dry, but not liberating the seeds. They break
into pieces, each of which encloses a seed. This is true of
the fruits of the hemlock and all Umbellifers, of mallows,
of Labiates. It is enough to look into the calyx of a ripe
White Dead Nettle to see that the fruit has neatly divided
into four nutlet-like pieces, each enclosing a single seed.
Third, there are nuts and nutlets (achenes), also dry and
not liberating the contained seed. In true nuts, such as
those of the hazel, there is a very hard fruit-wall, to which
the enclosed seed is not adherent ; in the fruits of a butter-
cup (achenes) the wall is not hard, and the enclosed seed
is not adherent; in grains of wheat the fruit -wall is
somewhat leathery, and the envelope of the seed is adherent
to it. This may serve as an illustration of how classification
proceeds, division within division, as long as there is a
clear basis of distinction.

Turning from the dry to the succulent fruits, we find
that there are two main kinds. There are the stone-
fruits, or drupes, with three layers, the middle one more or
less juicy, and the innermost one (the " stone ") always
very hard. Cherries and plums at once suggest them-

AUTUMN FRUITS 271

selves as examples. Lastly, there are berry- fruits in the
wide sense, where the seeds are embedded in pulp, as
in the case of gooseberry and currant and grape.

Besides these so-called simple fruits, each of which
represents one seed-box or ovary, there are more difficult
compound fruits, such as a strawberry, which is a collection
of tiny nutlets embedded on the surface of the fleshy
apex of the flower-stalk; or a bramble-fruit, which is a
cluster of drupes ; or a rose-hip, which is a collection of
nutlets inside the fleshy apex of the flower-stalk turned
into a cup. There are others, still more compound, which
correspond to a whole inflorescence or group of flowers,
such as the fig, which is a collection of fruits within a
juicy flower-stalk. The pine-apple is another familiar
example ; it seems to be a collection of fleshy berries and
fleshy bracts.

It may be noticed, too, that there are some very difficult
cases in regard to some of which the botanists themselves
are not always agreed. The fruit of the juniper seems to
be a reduced cone that has become fleshy ; in the yew
there seems to be a naked seed partly surrounded by a
fleshy seed-mantle or aril ; in the pomegranate the coats
of the seeds have become juicy ; the banana is, perhaps, a
long seedless berry ; the cucumber is a berry with a tough
epicarp ; the orange is a many-chambered berry with
juicy partition-walls and a leathery epicarp rich in oil
cavities ; and even the apple is often regarded as a berry.

It is easy to make fun of " botanical conundrums " :
" Why is a strawberry not a berry, when a date is ? " But
while an understanding of fruits will not be helped by
pedantry, it is likely to be helped by precision. To see
things clearly is often the first condition of insight. There-
fore, it is profitable to delay for a little, puzzling over the
real nature of certain difficult fruits. Let us take in

272 THE BIOLOGY OF THE SEASONS

illustration some of the fruits that are popularly and
erroneously called " nuts." Why is a Brazil-nut not a
nut ? Because it is a seed — one of many from a large box.
Why is a pea-nut not a nut ? Because it is a pod. Why
is a walnut not a nut ? Because it is the stone of a drupe.
Why is a horse-chestnut not a nut ? Because the fruit
is really a capsule with big seeds. Why is a cocoa-nut not
a nut ? Because it is the stone of a large drupe with a
leathery epicarp and a fibrous mesocarp. The hazel
has a typical nut with a sheath of succulent bracts at
the base; the beech has three-sided nuts with woody
external bracts ; the acorn is a nut with an extra scaly
cupule.

Towards an understanding of fruits, a few suggestions
may be offered. In the case of succulent fruits, we have to
remember that the green plant is a sugar-factory, that it is
an extremely anabolic organism with an income greatly
n excess of its expenditure, that it makes very much
more sugar than it needs, that some of this surplus over-
flows in the nectaries of the flowers, and that after the
nectaries close up the surplus may be drafted into the fruit.
Having got this elementary but fundamental fact clear,
we may go on to the secondary interpretation that juicy
fruits are well adapted for seed-scattering by fruit-eating
birds, and that plants with juicy fruits will therefore, in
certain conditions, prevail.

Again, in regard to fruits of the capsule type, which
liberate the seeds by splitting, either gently or explosively,
we have to remember that the sides of the box are usually
the carpels — that is to say, leaves modified for the production
of seeds. These carpels, like other leaves, are organs of a
limited length of life ; they are likely to die and wither,
and crack and shrivel, and fall off like other leaves. And,
again, it is this primary fact that should come first, and

AUTUMN FRUITS 273

insistence on the survival-value of the bursting of box-
fruits that should come second.

When we inquire into the chemistry of fruits one big
fact stands out clearly, that they have relatively little of
the more valuable reserve-stuffs. They have relatively
little proteid material, but if they are succulent they may
have much water and sugar. Seeds, on the other hand,
are rich in proteids, and the advantageousness of this is
plain, when we recognise that what is spent in the fruit
is lost, while what is stored in the seeds is legacy. Apart
from the seeds, it is said that it requires i£ Ib. of grapes,
2 Ib. of strawberries, 2j Ib. of apples, and 4 Ib. of pears to
furnish as much proteid as there is in one egg.

In the ripening of the fruit many interesting chemical
changes go on. There are fermentations, for instance,
such as that which changes the starch of the unripe fruit
into the sugar of the ripe fruit, or that which changes pectose
into pectin. There is the appearance of pigments, such as
the anthocyanin of the rosy-cheeked apple, which is the
same as the red of the withering leaf and of some flowers.
There is also the formation of ethers and oils and other
subtle compounds, some of which are aromatic, giving the
fruit a fragrance which is sometimes even finer than that
of the flower.

18

SEED-SCATTERING

MAN is harvesting and gathering into barns, but Nature
is scattering abroad and sowing, and nothing is
more characteristically autumnal than this dispersal of
seeds. It is one of the most interesting chapters in the
Natural History of the Seasons.

The import of the scattering is partly, of course, just
sowing, but it is also advantageous that what is sown
should be carried away from the shadow of the parent
plant or away from a crowded area. It is well that the
family should scatter. There is an attendant disadvantage
that many are lost altogether, and that others are borne
into very unsuitable situations. That the advantages
must in many cases far outweigh the disadvantages of
dispersal, may be safely inferred from the fact that the
adaptations securing it are so numerous and varied.

Perhaps the simplest of all ways is seen in box-fruits
which break up and allow the seeds to tumble out. They
may rebound to some distance when they fall, or they may
be blown by gusts of wind, or they may be carried by
runlets of water. The ants sometimes take the seeds of
the cow-wheat (Melampyrum) into their nests, as if they
mistook them for their own offspring, for they are not very
unlike cocoons.

It is evident, however, that the gentle breaking up of
a box-fruit can be improved upon, and there are various
degrees of explosive dispersal, from the popping of whin-
pods and broom-pods, which we often hear when sitting

274

SEED-SCATTERING 275

quietly in the country, to the energetic slinging of the
balsam (Impatiens noli-me-tangere). More extraordinary
is the almost animal violence of Hura crepitans, which
breaks into pieces, as if an explosive bomb, " with a report
like that of a pistol." In all cases what happens is, that
when the dying of the walls of the fruit reaches a certain
stage, there is a sudden release of certain tissue-tensions,
and hence the explosion. " In the case of the box (Buxus),
the smooth seeds are forcibly discharged by the contraction
of the pericarp, like a bean pressed between the fingers."
The pulling of the trigger is often due to the state of the
weather.

Another simple method of dispersal is illustrated by a
few dry fruits which adhere readily to passing animals,
such as rabbits, and eventually fall off, it may be far
from the site of the parent plant. The little brown nutlets
of Jack-run-the-hedge or cleavers (Gallium aparine) are
covered with asperities which take a firm hold ; those of
the burdock have long crochet-needle-like hooks ; and
the awns of grasses are also very effective for adhesion.
The fruits of Medicago are common in the fleece of sheep,
but it is difficult to regard this as a profitable mode of
dispersal.

The similarity of aquatic plants and animals in far-
separated freshwater pools is often very striking, and
part of the explanation is certainly, as Darwin pointed
out, that water-birds transport seeds and germs from
pool to pool on the mud attached to their feet. The same
is true of land-birds, which get clodlets fixed on their damp
feet. Darwin made a thorough study, after his wont,
of the fauna and flora of birds' feet, collecting the clodlets
and moistening them, to see what would come forth.
He proved up to the hilt the importance of this mode
of transport, and he was rewarded on one occasion by

276 THE BIOLOGY OF THE SEASONS

obtaining from one bird no fewer than eighty germinating
seeds.

This classic case may be quoted : " Professor Newton
sent me the leg of a red-legged partridge (Caccabis rufa)
which had been wounded, and could not fly, with a
ball of hard earth adhering to it, and weighing 6£ oz.
The earth had been kept for three years, but when broken,
watered, and placed under a bell glass, no less than eighty-
two plants sprung from it ; these consisted of twelve
monocotyledons, including the common oat, and at least
one kind of grass, and of seventy dicotyledons, which
consisted, judging from the young leaves, of at least three
distinct species. With such facts before us, can we doubt
that the many birds which are annually blown by gales
across great spaces of ocean, and which annually migrate —
for instance, the millions of quails across the Mediterranean
— must occasionally transport a few seeds embedded in
dirt, adhering to their feet or beaks ? "

A third method of dispersal is by means of parachutes,
which make it easier for the fruits to be carried by the
wind. We see the thistle-down and dandelion-down with
their beautiful hairy parachutes " sailing before the wind."
It is interesting to watch one enter by the open window
of a railway carriage, sail around once or twice, touching the
cushions for a moment, and then move on again, finally
passing out where it came in. There is something curiously
animal-like in its visit of inspection. An unforgettable
sight is a flight of clematis fruits — each a nutlet tipped
with a long white feathery plume. It is the hoary appear-
ance of the ripe fruits, massed together on the hedge, that
gives the plant one of its common names, Old-Man's-
Beard. When the fruits are set free by the breeze, the
plumes are often entangled in long rows, which float off
with a beautiful undulating motion, like silver serpents in

SEED-SCATTERING 277

the air. Strasburger refers to an experiment with the
hairy fruit of the artichoke, which was allowed to sink
in vacuo and in the air. " Compared with the accelerated
fall in a vacuum, the retardation exerted by the resistance
of the air (by which the opportunity for dispersal through
the agency of the wind is enhanced) is, in the first second,
as six to one."

Another form of the parachute adaptation is seen in the
winged fruits of the maple and the ash and the elm, and
some other trees. In the case of the maple there is a
heavy nutlet at one end ; the other is prolonged like an
insect's wing. If we throw the fruit into the air, as every
country schoolboy knows well, it sinks slowly down with
a beautiful twisting motion at some distance from where
we are standing. So, when this fruit is torn from the
tree by the wind, the parachute not only acts in a general
way like a float, giving the wind time to get a grip of it
and whirl it away, but it causes that peculiar gyrating
fall that even on a quiet day carries it far beyond the
tree's shadow. The importance of this for the seedling
is obvious.

Any structural peculiarity that increases area without
increasing weight will aid in wind-dispersal, and it is
interesting to notice that the same result is reached in
many different ways. The wings may be expansions of
the sepals, or of the seed-box, or of the seeds themselves.
" In a Bignonia seed, with its widely outspread glossy
wings, the centre of gravity is so disposed that the seed
floats lightly along through the air in an almost horizontal
course, and with a motion like that of a butterfly "
(Strasburger's Botany, p. 291).

In some cases the currents that transport seeds and
fruits are in water, not in air, and there may be structural
peculiarities that suit this well, such as water-tight tissues

278 THE BIOLOGY OF THE SEASONS

and gas-floats. In no other way could coco-nuts be carried
to isolated and uninhabited coral-islands, where they
sometimes form the beginning of terrestrial vegetation.
Writing of Keeling or Cocos Islands, coral formations
in the Indian Ocean, about six hundred miles distant
from the coast of Sumatra, Darwin called attention to
the number of seeds carried over from Sumatra and Java.
" It is interesting thus to discover how numerous the seeds
are, which, coming from several countries, are drifted over
the wide ocean. Professor Henslow tells me, he believes
that nearly all the plants which I brought from these
islands are common littoral species in the East Indian
Archipelago. From the direction, however, of the winds
and currents, it seems scarcely possible that they could
have come here in a direct line. If, as suggested with
much probability by Mr. Keating, they were first carried
toward the coast of New Holland, and thence drifted
back together with the productions of that country, the
seeds, before germinating, must have travelled between
1800 and 2400 miles."

One of the most effective means of securing dispersal
is that which seems at first glance to be least propitious —
that the fruit should be eaten. What seems, for a moment,
like a full stop, works well when it works at all, namely,
in cases where the seeds are not digested. Succulent
fruits are eaten by many birds and by a few mammals ;
they are eaten for their own sake, and the hard envelopes
of the seeds huthe case of berries, the hard endocarps of the
fruit in the case of drupes, save the seed from being digested.
It is passed out from the food-canal none the worse, in
some cases probably the better, often, naturally enough,
far from the place where the fruit was eaten. In this way
we can interpret the occurrence of an isolated gooseberry
bush far from any human dwelling.

SEED-SCATTERING 279

Some of the modes of scattering are peculiar and rare.
Thus the squirrel may forget some of his hidden stores
of beech-nuts, and germination may take place. There
is some evidence, too, that earthworms occasionally plant
trees.

Sometimes the fruit or the seed has some peculiarity
which mechanically assists lodgment in the soil, some-
what in the same way as the corkscrew-like automatic
boring of the egg-case of the Port Jackson shark effects
fixation in a crevice in the rocks. A long bristle or awn
in the stork's-bill and some grasses begins to twist under the
influence of the moisture in the soil, and literally bores its
way in. And again, the wall of the seed or the fruit may
have a mucilaginous sheath, as in the case of quince and
flax, which effects attachment to the soil, and also serves
to absorb water like a sponge. But even more interesting
is the adaptation in the pea-nut (Arachis hypogcea), whose
fruit stalk curves down to the ground and pushes the
pod in, reminding one in a quaint way of some animal
hiding its egg in the ground. Not less effective is the
behaviour of the ivy-leaved Toad-Flax (Linaria cymballaria) ,
which beautifies so many old walls. The fruit stalks
bend away from the light, which is learnedly called being
negatively heliotropic, and the result is that the capsules are
actually pressed into the crannies and crevices. A peculiar
idiosyncrasy has become the basis of an adaptation that
works extraordinarily well, as we may see in watching the
rapid spreading of this " Mother of Thousands," as the
plant is sometimes called, over a wall or a cliff which seemed
anything but a hospitable territory to colonise.

Cases like pea-nut and toad-flax suggest an approxima-
tion to what one is tempted to call " parental care," were it
not that such irrelevancies of expression are apt to mislead.
But they are rare, and certainly far from typical. The big

280 THE BIOLOGY OF THE SEASONS

biological fact which the seed-scattering in Autumn brings
home to us is the prodigality and wastefulness of life — such
a small proportion of the scattered seeds have any future. As
Tennyson said, Nature is "so careless of the single life " ;
" of fifty," or, as he afterwards suggested, " of myriad seeds,
she often brings but one to bear." In spite of all the neat
and effective adaptations, it must be said of a large number
of species that they succeed not because they are strong, but
because they are many. Wallace quotes Kerner to the
effect that a common British weed (Sisymbrium sophia)
often has three-quarters of a million seeds ; if all grew to
maturity for only three years the whole of the land-surface
of the globe would not hold them.

THE WORK OF EARTHWORMS

IN the damp Autumn weather the earthworms drag
many fallen leaves into their holes, and we may
think over their industry at this season, though there is
no time, save when the soil is hard-bound in frost, that they
are not busy — boring their way or eating their way under-
ground, grinding the particles small in their gizzards,
bringing castings up and taking leaves down, and doing
much more besides. In 1777, Gilbert White got at the very
root of the matter, and his memorable letter on the subject
cannot be read too often. " 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 consequently sterile.

282 THE BIOLOGY OF THE SEASONS

. . . These hints we think proper to throw out, in order to
set the inquisitive and discerning at work. A good mono-
graph of worms would afford much entertainment and
information at the same time, and would open a large and
new field in natural history."

Long afterwards one who was beyond most men " in-
quisitive and discerning " did set to work, and the mono-
graph that Gilbert White had wished for in 1777 was pub-
lished by Charles Darwin in 1881, the year before he died —
" the completion," he said, " of a short paper read before
the Geological Society more than forty years ago." With
his characteristic thoroughness and patience he collected
data year after year until he had worked out irrefutably
the part that earthworms have played in the history of
the earth, and proved that they deserve to be called the
most useful of animals. Here we have one of the finest of
object-lessons on the cumulative importance of little things.

By their burrowing the earthworms loosen the soil,
making way for the plant-roots and the raindrops. By
bruising the soil in their gizzards — perhaps the most
important mills in the world — they reduce the particles
to more useful powdery form. By burying the surface
with castings brought up from beneath, they have been
for untold ages turning the soil upside down — ploughers
long before there was any plough. By burying leaves
they have made a great part of the vegetable mould over
the whole earth. For, apart from very wet places and very
dry places, and salt soil near the sea, there are earthworms
of some sort everywhere. We recently found thirteen
midribs of the rowan or mountain-ash, radiating round the
mouth of one burrow like the spokes of a wheel ; the
withered leaflets had been carried down, two were still
sticking out at the entrance ; that meant ninety-one leaflets
to one hole, and this has been going on for countless years.

THE WORK OF EARTHWORMS 283

Darwin's statistics are eloquent, but we cannot give
more than a few samples. He showed that there are often
50,000 (and there may be 500,000) earthworms in an acre
of good soil ; that they often pass 10 tons of soil per acre
per annum through their bodies ; and that they often cover
the surface at the rate of 3 in. in fifteen years. Though a
common British worm only passes out about 20 oz. of earth
in a year, the weights deposited in a year on two separate
square yards which Darwin watched were respectively
675 Ib. and 8-387 lb., which correspond to 14! and 18 tons
per acre per annum. A field which was so thickly covered
with hard flints that it was known as " the stony field," was
left untouched for thirty years, after which, we are told, a
horse could gallop from one end to another without ever
striking a stone.

As we follow the work further, additional aspects of
importance are revealed. It is plain, for instance, that
the constant exposure of the soil-bacteria is bound to
have far-reaching effects both for good and ill. On the
one hand, it allows the microbes to be scattered by wind
and rain ; on the other hand, it exposes them to the action
of the sunlight, the most universal, effective, and econ-
omical of all germicides. In Yorubaland, on the West
Coast of Africa, Mr. Alvan Millson calculated (following
Darwin's methods) that about 62,233 tons of subsoil are
brought every year to the surface of each square mile,
and that every particle of earth, to the depth of two feet,
is brought to the surface once in twenty-seven years. It
need hardly be added that the district is fertile and healthy.

Earthworms also play their part in the disintegration
of rocks, letting the solvent humus-acids of the soil down
to the buried surface. Their castings on the hill-slopes
are carried down by wind and rain, and go to swell the
alluvium of the distant valleys or the wasted treasures of the

284 THE BIOLOGY OF THE SEASONS

sea. The well-known parallel ledges along the slopes
of grass-clad hills are partly due to earthworm castings
caught on sheep-tracks, and thus we begin to connect
the earthworms not only with our wheat-supply, but
with our scenery.

And as we began this short sketch by quoting Gilbert
White, so we shall close it by quoting Darwin. " When
we behold a wide turf -covered expanse, we should remember
that its smoothness, on which so much of its beauty de-
pends, is mainly due to all the inequalities having been
slowly levelled by worms. It is a marvellous reflection
that the whole of the superficial mould over any such area
has passed, and will again pass, every few years through
the bodies of the worms. The plough is one of the most
ancient and valuable of man's inventions ; but long before
he existed the land was in fact regularly ploughed, and
still continues to be ploughed, by earthworms. It may be
doubted whether there are many other animals which have
played such an important part in the history oj the world as
these lowly organised creatures.1'

DEEPER PROBLEMS OF MIGRATION.

THE first of the deeper problems is as to the position
of migrational movements on the inclined plane of
animal activities. Do they imply intelligent control at
every, or at any step ; is there anything habitual about
them, or have they an entirely instinctive basis, that is to
say, is the brain endowed by inheritance with ready-made
preparedness of a very definite kind for the great annual
effort of migration ? If we take this last view, there is no
reason to increase the puzzle by raising the wider question
of how instinctive activities arise at all, for that has no
special relevancy to this particular case. Every one knows
that the animal world is rich in examples of instinctive
activities, for the performance of which, without education
or experience, the brain is hereditarily endowed by the
establishment of definite nerve-paths or otherwise. Our
question is, whether birds have a specific hereditary pre-
paredness for their migratory movements, analogous to
that which bees have for burglaring the blossoms and
building a honeycomb, or that which spiders have for
spinning a complex web ?

That the migratory movement has an instinctive basis,
is suggested by a number of facts which have a cumulative
force, though they are not individually very convincing.
Migration shows a regularity and orderliness, without
much individuality and with little hint of caprice, which
is suggestive of the instinctive ; preparations are made

for the journey before — often long before — there is any

285

286 THE BIOLOGY OF THE SEASONS

real need for setting out, and before the wintry conditions
have begun to be appreciably felt ; the departure of young
birds apparently unguided, and similar phenomena, recall
the wonders of untutored instinct among insects ; and a
few observations on the restlessness of comfortably caged
birds at the proper season point in the same direction.
Matthew Arnold has a fine reference to the restlessness of
the captive stork when the time comes to travel south,
though in his picture the bird is supposed to see its fellows
passing overhead.

" And as a stork which idle boys have trapp'd,
And tied him in a yard, in Autumn sees
Flocks of his kind pass flying o'er his head
To warmer lands, and coasts that keep the sun; —
He strains to join their flight, and from his shed
Follows them with a loud complaining cry" —

Another of the arguments that may be used in support
of the conclusion that the migrational effort has an in-
stinctive basis, is that we find somewhat similar periodic
movements, from and to a breeding-place, in widely
separated divisions of the animal kingdom. We find
migrations of mammals, of sea-turtles, of fishes, such as
the salmon, of land-crabs, and of other types. But it is
uecessary to be careful in distinguishing from true migra-
tions— part of the essence of which is a return of adults
to their birthplace — certain other mass-movements which
are merely outpourings of superabundant population, or
enforced pursuits of a nomadic food-supply.

It is a migration when the land-crabs make their quick
march, sometimes of several miles, to the sandy coast to
have their eggs hatched in the old home, but it is not a
migration when the irresistible aerial army of locusts
spreads over the land. It is a migration when the salmon
and the sturgeon return to breed in their native fresh
waters, but it is not a migration when the mackerel shoals

DEEPER PROBLEMS OF MIGRATION 287

follow the distribution of minute crustaceans in the sea.
We recall the march of the lemmings from the Tundra,
and from the Scandinavian valleys, where they have
become too numerous ; they press westward in search of
food, through villages, over walls, across rivers, until they
reach the North Sea, which solves their population problem
But this is no more a true migration than are the invasions
of rats and voles that occur every now and then as the
result of some unwonted disturbance of the balance of
nature.

Among mammals there are not a few records of periodic
movements, for instance, among deer, among bats, and
among cetaceans, but they do not all fulfil the criteria of
true migration. This is illustrated, however, by many
seals, though not by our common British Phoca vitulina,
which travel periodically to their breeding-places.

In accepting the view that migration is instinctive,
we do not suppose that this explains much, or that there is
no learning to be done. The establishment of an instinct
requires analysis just like that of a habit, and there are many
instincts that are improved for the individual by experience.
We have to avoid the one extreme, well stated and forcibly
rejected by Mr. Dixon, that " birds migrate by instinct,
knowing not how or why, impelled along a course that
never errs or changes, flying from point to point with no
more mental effort than an arrow from a bow." The
prompting, this author says, is instinctive, but there is much
that the bird has to learn. The instinct is very variable
and often imperfect, for " birds blunder like human folk,
losing their way, and perishing in uncounted hosts/' We
have to avoid the other extreme of supposing that a success-
ful migratory journey is the outcome of sensory alertness
and good judgment. Somewhere between these two
extremes the truth probably lies. There is a migratory

288 THE BIOLOGY OF THE SEASONS

instinct, part and parcel of the bird's inherited constitution,
and doubtless varying in precision and in content in different
birds. But it is not inconsistent with this to believe that
keen senses, quick perceptions, good memory, obedient
following of leaders, and a sense of direction, are also of
great importance. We have ourselves so few instincts
that it is difficult for us to get mentally near creatures in
whose life instinctive activity bulks largely, but we need
not suppose that the migratory instinct is isolated from the
bird's highly evolved sensory life, or from its undoubtedly
good memory.

If we start right away with the astonishing migrational
movements of the knot or the curlew-sandpiper, and assert
that these have an instinctive basis, we may be accused
of escaping from a formidable difficulty under the shelter of
a word. But in evolutionary interpretation this impression
always arises when we begin by thinking of the most ela-
borate and finished product, instead of the simplest possible
illustrations. If we are thinking of the problem of the
evolution of the eye, we should not begin with man's or
the eagle's ; if we are thinking of the problem of the
evolution of sex, we should not begin with the elaborately
finished dimorphism of peacock and peahen, but with cases
like sea-urchins, where it requires a microscope to tell the
male from the female. So in regard to migration, we may
reasonably begin with the short migratory movements, say
of blackbirds, which are relatively simple affairs.

If we are convinced that there is warrant for speaking
of a migratory instinct, we may pass to the next question,
What conditions led to the establishment of this instinct?
When we think back imaginatively to the beginning of
migration, we see the emergence of a new idea, which is
called, in the technical language of Biology, a mutation.
A new constitutional type arose — the revolutionary, who

DEEPER PROBLEMS OF MIGRATION 289

would not take hard times lying down, who was sensitive,
alert, restless, unconventional, adventurous, and original,
who was a genius, in short, a Columbus-bird.

To meet a difficulty — such as hard Winters — there may
be detailed readjustments of what has been already estab-
lished ; the plumage may turn white, for instance, which
always helps, or a thick layer of fat may accumulate be-
neath the skin. But there is another way of meeting a diffi-
culty,— by evading it altogether, and that requires genius,
and that was how migration was started by a number of
highly original birds, who discovered that the prison-doors
were open, and who thought it was worth while trying
whether Land's End in Cornwall or elsewhere was really
Land's End.

All living creatures tend to flee from the uncomfortable,
and it is evident that, as the earth and the bird are consti-
tuted, things are against permanent residence in one place.
Moreover, in the course of the evolution of climates, since
birds began to be, there have been successive glacial
periods in which the Northern Hemisphere was certainly
not a fit winter-residence for birds, and for long ages not
a fit home for birds at all.

The greater part of the Northern Hemisphere once had
a much warmer and more equable climate than it now
enjoys. There were magnolias blooming in Greenland and
palms flourishing in England as they still do in mild places
like Penzance. It was perhaps relatively unimportant to
birds where they went, though they would tend to get
away from the hotter regions at the breeding and brooding
time, and would move southward from the more exposed
northern outposts when Winter came. But as the climate
became gradually more severe, and the snowline crept
lower and lower on the mountains, and great glaciers were
formed, birds had to move farther and farther south every

2QO THE BIOLOGY OF THE SEASONS

half-century. In many cases it became impossible to return
to the old home in Spring. The whole of Britain, for in-
stance, was probably ice-covered, except a narrow stretch
along the South of England. Those birds that could not
endure the more southerly breeding and brooding would
be eliminated, those that were slow to recognise the menace
of approaching Winter would be eliminated, and those that
had no sense of direction would be eliminated, and the
migratory instinct would diffuse itself and become more and
more precise.

After the Ages of Horror were passed and the ice had
in great part retreated to the Polar Regions, there came
about what we may still see continuing — the recolonisation
of the North Temperate Zone as a breeding area. At the
present time there are some birds, such as starlings, which
are pressing farther and farther northward year after year.
In connection with this return to old racial haunts which the
Ice Age had rendered quite unhabitable, we must remember
that other climatic changes were probably in progress
which made the South a more and more difficult region
for secure breeding and successful brooding.

In general terms, then, the present-day Spring migra-
tion northwards implies an organic reminiscence of the
original headquarters before the Ice Ages ; and the
present-day Autumn migration southwards implies an
organic reminiscence of the second home which was dis-
covered under the stress of the glacial invasion. And
the paths of the migrants to-day may still correspond in
some measure to those established by slow degrees as the
ice flowed and ebbed. It is certainly very significant
that many birds from the Continent should cross to the
South of England in Autumn and then curve farther south-
wards— in this way visiting the tract of Britain which was
not covered by the ice,

DEEPER PROBLEMS OF MIGRATION 291

Our view, then, is this, that an original instinctive
Mutation must be postulated, which amounted to " a new
idea," but was not an idea, which found expression in
restlessness, in sensory alertness, in adventurous experi-
ment, in a " Wander-trieb." Perhaps we see something
like the beginning of it to-day in animals which seem to
be sensitive to impending storm, and act accordingly. But
given some sort of definite beginning of a migratory in-
stinct, as a germinal mutation, we would account for the
diffusion and augmentation and specialisation of this by
the well-known Darwinian interpretation, especially elabo-
rated by Dr. Alfred Russel Wallace. Those individual
birds who were too dull, or too wilful, or too unplastic,
to take the hints and warnings of the increasing scarcity,
the cold winds, or it might be the dry heat, would be
eliminated. This elimination, still a dreadfully real pro-
cess, would, being discriminate, gradually raise the
standard of migratory capacity century after century,
millennium after millennium, for we must bear in mind
that the great climatic changes must have come about
with extreme slowness.

Another general theory of the conditions which led to
the establishment of a migratory instinct, lays the emphasis
on the food-supply. Many birds are prolific, and over-
crowding is apt to occur. They have to extend their range,
and they take the lines of least resistance as regards food.
They push northward in spring, exploring new grounds,
staying as long as they can, and retreating before the
Winter to the original home. Instead of crowding in one
area all the year, and involving themselves in want, they
exploit two areas, each for about half of the year. We
see the same sort of thing among men, for instance, in the
Summer migration to the high " alps," and the return in
Winter to the village in the valley. It has often been

292 THE BIOLOGY OF THE SEASONS

pointed out that the more prolific birds tend to have the
wider migratory range— a fact which fits in well with the
theory outlined. We venture to quote a statement of the
case from Mr. W. P. Pycraft's excellent History oj Birds
(1910) :—

" We may assume that the migratory species owe their
origin to the matter of food-supply. Composed of indi-
viduals subsisting on a food of universal range, but limited
in supply, they were enabled to roam farther afield as their
numbers strained this supply in their immediate neigh-
bourhood. Annually, however, a check was placed on
further extensions of range by the cares of breeding, and
by the diminution of food at the end of the breeding season,
— whether caused by climate or otherwise, — while behind
them the supply was increasing. Thus they were drawn
back towards their starting-point. Again threatened by
famine, they once more turned outwards, finding the earlier
depleted area restocked. These movements, in short,
were doubtless then, as now, periodic, and determined
largely, if not entirely, by seasonal changes. Such species,
increasing numerically with their increase in range, were
naturally automatically compelled to still farther extend
this to obtain the means of sustenance. That each indi-
vidual would return by the route he came by is but a
natural inference, and the same is true of the offspring of
each pair — hence the ' homing instinct/ and the formation
of British or other races of migrating species/'

Dr. Alfred Russel Wallace has laid emphasis on the
abundance of food in the Far North as a factor in establish-
ing migration. He quotes Mr. Seebohm : " Birds go to the
Arctic regions to breed, not by thousands, but by millions.
The cause of this migration is to be found in the lavish
prodigality with which Nature has provided food. Seed-
or fruit-eating birds find an immediate and abundant

DEEPER PROBLEMS OP MIGRATION 293

supply of cranberries, crowberries, and other ground fruit,
which have remained frozen during the long Winter, and are
accessible the moment the snow has melted, while insect-
eating birds have only to open their mouths to fill them
with mosquitoes." The vast hordes of mosquitoes (which
do not seem to trouble birds) and their larvae swarming
in the pools seem to account for "the very existence
of a considerable proportion of the bird-life in the
Northern Hemisphere."

Dr. Wallace goes on to say : " Abundance of food
suitable for both parents and young at the season of
breeding would inevitably attract birds of all kinds from
more southern lands, especially as the whole area would
necessarily have no permanent residents or very few, but
would, each recurring season, be an altogether new and
unoccupied, but most fertile country, to be reached, from
any part of the North Temperate lands, by merely following
up the melting snow. And as, a few months later, the
myriads of young birds in addition to their parents were
driven south by the oncoming of the cold and darkness,
they would find it necessary to travel farther and farther
southward, and would again find their way north when
the proper season arrived."

We have stated two theories of the origin of migration.
Neither is very convincingly complete by itself; perhaps
a combination of the two is best.

IMMEDIATE STIMULI OF MIGRATION

The next question is as to the immediate causes which
now pull the trigger of the migratory instinct twice
a year at the proper time. In the case of the Autumn
movement southward, we naturally think of (a) the in-
creasing cold and the lack of shelter, (b) the setting-in of

294 THE BIOLOGY OF THE SEASONS

stormy weather, (c) the marked shortening of the daylight
hours available for food-collecting, and (d) the dwindling
supply of insects and slugs, fruits and seeds, and the like.
In one or more of these external conditions we may perhaps
find sufficient liberating stimulus to set the migratory
instinct at work.

In many ways the return Spring journey to the birthplace
is more difficult to understand than the Autumnal journey
southwards. The stimulus may be the setting-in of dry
heat, or uncomfortable weather of some sort, or the shrink-
age of the water-pools, and there is the awakening or re-
awakening breeding instinct. On the other hand, a large
proportion of the birds who undertake the northerly
journey in Spring are immature, and cannot be prompted
by any breeding impulse. Again, though one cannot
wonder that birds should like to get out of the heat and
the crowd and the multitudinous enemies of lower latitudes,
we cannot shut our eyes to the hazards of nesting in the
Far North. The young bird, as we have seen, is for days
after hatching very imperfectly warm-blooded, and cannot
be left exposed for even a short time without fatal results.
It is probably the constitution of the bird that makes it
necessary for some to go so very far north, just as the
eels are constitutionally impelled to go far out and far down
into the Atlantic. Perhaps in both cases the constitution
was established in relation to the conditions of the ancient
headquarters, the old home of the stock. Thus there
may be a constitutional home-sickness, though no psychical
one. There is no warrant for supposing that the Knot has
a " fond memory " for its birthplace in Northern Siberia.
Although Professor William K. Brooks suggested that the
north-bound Spring migrant who ignores so many choice
spots on its route, may be like " The shuddering tenant
of the frigid zone/' who " Boldly proclaims that happiest

DEEPER PROBLEMS OF MIGRATION 295

spot his own," we are not inclined to go beyond the hypo-
thesis of a visceral Heimweh.

We must not press these considerations too hard, as if
living creatures were inert balls buffeted here and there by
sheer compulsion. The reasons we have given for the
autumnal and vernal movements are impelling rather
than compelling, they operate on constitutional pre-
dispositions. There are notable difficulties remaining,
and curious individual exceptions, such as that of the
cuckoo. Therefore let us turn for a moment, all unsatisfied
with explanations, to enjoy the mysteriousness of this
vital tide, agreeing with Gatke that " both phases of the
great movement unfold a picture of bird life of incom-
prehensible grandeur, presenting to our wondering sight
myriads of these restless wanderers hastening during the
long dark nights of Autumn, or the starlit midnight hours
of Spring, by many intersecting paths, to their far-off
Winter quarters or their nesting homes ; each species
following, at higher or lower regions in the sky, a sure
and definite road, not marked out for them along river
courses or mountain chains, but one that leads them,
independent of every physical configuration of the earth's
surface, and at heights many thousands of feet above it,
surely and safely to the distant goal."

This brings us to the question, How do the birds find
their way ? It is our strong conviction that before natural-
ists will make much of a question of this degree of difficulty
there will require to be many years of hard work at much
less exciting questions, such as What way do they find?
At the same time, it is very interesting to raise the very
difficult question of way-finding, and to consider the sug-
gestions that have been offered.

" Who calls the council, states the certain day,
Who forms the phalanx, and who leads the way ? "

296 THE BIOLOGY OF THE SEASONS

How is it that a swallow which has wintered in Africa
comes back to its birthplace in the South of England ?
How is it that young birds, who never left the parish before,
start off on a Summer evening and make their way to the
Nile Valley ? How do they keep their direction in the
dark and at great heights, or do they very often go very
badly astray ? If it be true that the northward-bound
Spring migrants often take a short cut, different from their
Autumn journey south, how is this to be thought of ?
Sailing northwards from the Cape by the West Coast route
one meets in Autumn numerous migrants making their
way south. Many of these rest for hours on the ship, but
most of them certainly continue their southward journey.
Why?

a. It has been suggested that success in way-finding
may be due to inherited experience, slowly cumulative
from generation to generation, enriched and specialised
by individually minute contributions. There are two great
difficulties in the way of this theory. In the first place, we
have no secure warrant for believing in the direct ent ail-
ment of the lessons of experience. In the second place, it is
difficult to see what content the experience could have in the
case of birds flying by night, and often at great heights, as
so many do.

b. A second theory attributes the success of the
migratory effort to tradition, and there may be some truth
in this attractive suggestion. The idea is that those lead
well one year who followed well for several years before.
There may be in each rushing troop some old, experienced
guides. Again, however, there are difficulties. Every
individual experience must have a content of definite and
concrete impressions, but what precise experience is to be
had out of a night journey at a high altitude over the
pathless sea? If we begin by traversing a difficult and

DEEPER PROBLEMS OF MIGRATION 297

dangerous path by daylight and establish a detailed experi-
ence, we can afterwards proceed, in a very interesting way,
to strip off one aid after another, until we can walk safely
on a very dark night with only a white stone, or something
of that sort, here and there to guide us. But there is no
evidence that birds learn to find their way after the fashion
we have just indicated. Moreover, there is the difficulty
that the young birds seem often to fly by themselves. In
the case of the cuckoo there does not seem to be an adult
left in the country when the young ones leave us in Autumn.
But it is not known that they are less successful than other
birds.

c. A third theory attributes the success of migratory
way-finding to sensory acuteness, and it seems likely that
there is some truth in this view. Numerous observations
show that migrants sometimes follow coast-lines, river- valleys,
lines of islands, and so on. We need not attend to stories
of birds following the roll of the waves, or guiding their
course by the stars, which are not scientifically much above
the level of the suggestion that they utilised the lines of
longitude, but the visual and auditory powers of birds are
so keen that we should be slow to exclude the possibility
that they utilise all possible landmarks.

d. In the dearth of facts, the tendency of the scientific
mood is to leave a question of this sort quite unanswered,
but to those who feel the necessity of coming to some
finding — albeit a provisionary one — we should recommend
the hypothesis of " a sense of direction," to which various
considerations point. There are many hints of this mys^
terious sense in other animals. We know it in cats and
dogs, in cattle and horses, of whose way-finding powers in
most intricate situations there is abundant evidence. It
has been satisfactorily proved in bees. There are apparent
illustrations of it in nomad human races and in exceptional

298 THE BIOLOGY OF THE SEASONS

civilised men, like the hero of Du Manner's Martian, who
always knew where the North Pole was, when he was in
good health at least.

The " homing " of pigeons is very suggestive in this
connection. They may be transported in a basket by train
or steamer and set free many miles from their dovecot —
and they are usually soon home. According to Tegetmeier,
an acknowledged authority, the power is mainly the out-
come of great sensory acuteness, and requires training if
the birds are to excel.

Professor Newton spoke of the migration of birds as
" perhaps the greatest mystery which the whole animal
kingdom presents— a mystery which attracted the attention
of the earliest writers, and can in its chief point be no more
explained by the modern man of science than by the simple-
minded savage or the poet or prophet of antiquity." But
this was perhaps too pessimistic. Admitting that " our
ignorance is still immense," may we recognise some hints of
progress towards greater clearness. We are slowly learning
to sift our data and to put our questions in more useful
form. Three methods have been followed with much
success. The first, associated especially with the name
of Gatke of Heligoland, is that of registering the arrivals
and departures of birds on a small area that can be
thoroughly explored. The second, associated especially
with the name of Eagle Clarke of Edinburgh, is that of
collecting data from lighthouses and lightships and similar
strategic points as to the annual streams of migrants. The
third, associated especially with the name of Thienemann
of Rossitten, is that of marking birds with numbered
aluminium rings and registering the whereabouts of those
(a small percentage) that are heard of again.

THE STORY OF THE SALMON

HP* HE whole of this story is not yet told, and what there
X is of it equally good observers tell in somewhat differ-
ent ways. But these are not sufficient reasons for severely
leaving it out of our seasonal chronicle. The broad facts
are certain, though uncertainties still abound. They are
largely due, we think, to the fact that this much-esteemed,
but intellectually defective fish has in no small degree an
individuality of behaviour and a plasticity of constitution.
Its freshwater environment, moreover, is very diverse,
for every river has a character of its own. What is to be
avoided is forcing a formula on the salmon.

We might include the story of the salmon with appro-
priateness at almost any season, but we have taken it as
an autumnal study for two reasons, because our best views
of the salmon surmounting a fall (is not this what their
very name points to ?) have been got in Autumn, and because
salmon spawn in British rivers in late Autumn or Winter.
One of the leading authorities * states the law for Scotland,
that " the height of the spawning season in the earliest
river, viz. 7th November, is one month earlier than the
height of the spawning season in the latest river, viz.
8th December."

The salmon's eggs are laid in the gravelly bed of the
stream in shallow water. The female makes a furrow for
them with her tail, and covers it roughly after her attendant
mate has shed upon them the fertilising milt. One female

1 W. L. Calderwood, The Life of the Salmon (1907).
299

300 THE BIOLOGY OF THE SEASONS

may go on depositing eggs at intervals for several successive
days, and the rival males fight with one another fiercely
for their place in her train. The hooked and some-
what distorted jaws of big males seem to be adapted as
weapons.

The eggs have many enemies, such as trout, eels, water-
fowl, and insect larvae, which have plenty of time to find
them out, for three or four months must elapse before they
are ready to be hatched. There are many other risks of
failure ; they may be left exposed by a great drought, or
washed away by a flood, or smothered by a shifting of the
gravel. It. need hardly be said, therefore, that only a
small proportion of the eggs become " fry/*

The newly-hatched young are very sluggish, and lie
among the stones, living on their legacy of yolk, which
may last for fifty days. It lies in a ventral sac, which
rather inhibits the little creature's movements. About
the eighth week after hatching, the yolk has been wholly
absorbed, and the larvae, or " fry," are about an inch long.
They begin to feed greedily on minute organisms in the
water, they grow quickly (in marked contrast to their slow
development), in two months they double their size, and
by the end of a year they are somewhat trout-like " parr,"
about four inches in length. It is interesting to recall
that it is only some seventy years since Shaw, at Drum-
lanrig, proved that the parr is the young salmon, and not
a member of a supposed related species (Salmo salmulus)
of diminutive size.

In their second year (in most cases) the young salmon
lose their trout-like markings and put on their " sea- jacket "
— tints of olive and gold overspread with glistening silver.
In other words, they become silvery " smolts," which migrate
to the sea. The descent of the smolt to the sea, Mr.
Calderwood writes, " is prompted by a most powerful

THE STORY OF THE SALMON 301

instinct. Give fish in confinement as much and as care-
fully selected food as they can eat, and the silvery smolts
are in no way induced to forego their seaward migration.
For the healthy growth and development of the species
salmon, as we now know it, the bracing qualities of the
sea, with its rich feeding, are absolutely necessary." 1 . . .
" We have no evidence that smolts would starve in any
of our rivers if they did not descend when they do. No
doubt they get a greatly increased and varied amount
of food when they do go into the sea, but the time when
the migration takes place is the time when the best feeding
season is commencing, and it seems to me necessary to
take the natural instinct for a temporary marine sojourn
into account as well as the need for increase of food/'
The descent of the smolts is mostly in Spring, and they are
often about six or seven inches long when they put on their
" sea- jacket."

The smolts that are successful in making the journey to
the sea — for they have to run the gauntlet of many dangers
— enter upon a course of voracious feeding which lasts for a
variable period. They devour young herrings and haddocks,
the eggs and larvae of crustaceans, and so on, and grow
apace. At the same time, the thinning of the crop con-
tinues, for a new set of enemies has to be faced — gulls,
cormorants, coal-fishes, and the like.

It is a common belief that salmon-smolts, descending to
the sea in April or May, may return as " grilse " in June
or July of the same year, and it is likely enough that this
is sometimes the case. On the other hand, smolts marked
by Malloch in 1905 returned as grilse in 1906. 2 Moreover,
if it be the case that the character of the lines on the scales

1 The Life of the Salmon, by W. L. Calderwood, Inspector of Salmon
Fisheries for Scotland (Arnold : London, 1907).

* P. D. Malloch, Life-History and Habits of the Salmon, Sea-Trout,
Trout, and Other Fresh-Water Fish (A. & C. Black, 1910, 263 pp.).

302 THE BIOLOGY OF THE SEASONS

may be relied upon to show how often a salmon returns to
fresh water, then Malloch's conclusion seems secure that
many skip the grilse stage altogether, and do not return
till they are salmon. If the assumption be granted, then
many of the smolts marked in 1905 returned as small
Spring salmon in 1907, and many came up the Tay in the
following year, from 20 to 40 Ib. in weight, without having
been in fresh water since they were marked. In any case,
it may be safely said that the smolts are moved by a strong
impulse to go to the sea, that they feed voraciously and
grow quickly there, and that they return sooner or later
to spawn. Most, if not all, of the energy which the salmon
show in ascending the swift streams, and in leaping up
the falls, is accumulated during the variable marine period.
For after youth there is practically no feeding in fresh
water.

Again, as in so many other cases, we have a sharp anti-
thesis between a feeding and growing period on the one
hand, and a fasting and reproductive period on the other
hand. It is the antithesis of caterpillar and butterfly over
again ; but how different the guise ! Few salmon seem
to spawn more than once, and some die of spawning.
After the exhausting process, they are known as " kelts "
— thin and lanky, and out of condition. They return to
the sea, regain their tone, and eat ravenously. It is certain
that some live to a good age, for giants of 55 and 60 Ib.
have been caught with the rod, and even larger ones in
nets.

There are serious discrepancies, both of observation
and interpretation, in the current accounts of the life-
history of this very common creature. As we hinted at
the outset, the probable reason for this may be found in the
variability of the organism on the one hand, and in the
diversity of its environmental stimuli on the other.

THE STORY OF THE SALMON 303

We must bear in mind, however, the broad fact that the
salmon is what one might call a " bimodal " organism. As
an adult it has its consistently ascetic, freshwater period,
with the single orgasm of reproduction, and its consist-
ently Epicurean, marine period of nutrition. Punctuated
by the seasons, though, for the reasons stated, with import-
ant exceptions, there is an almost diagrammatic contrast
between the nutritive and the reproductive phases.

AGAINST THE STREAM

'THHE river was in high flood, and the salmon were
JL pressing up it. They had been out to sea, and were
lusty ; it was a sight to watch them leaping high into the
air over the first step of the salmon ladder, dashing ahead
with strong tail-strokes, and rising rapidly to the top of
the fall. Their hunger was swallowed up in love, for fishes
love — as fishes can. To put it in another way, they were
making for the spawning-ground, and they were fasting.
One recalls that many momentous changes occur during
fasting periods. For it is when fasting that caterpillars
become butterflies, and tadpoles frogs. Thus there is a
biological justification of asceticism, although " Der Hunger
als forderndes Princip " (as the Germans phrase it in their
inimitable fashion) may be carried too far. There is
also apt to be a strange unconscious hypocrisy about it,
too, for the caterpillar is quietly absorbing its " fatty
body," and the tadpole its tail — which is a luxury
after all.

To return to the salmon at the fall. The lithe body,
less silvery than usual, shot out of the water ; then followed
a plucky rush amid the bubbles ; then in seven cases out of
ten the fish was swept back before it had cleared the second
rung of the ladder. It was as exciting as a racecourse.
The favourite cleared one barrier after another, lost energy
at the last, and was swept back like a log, while another

with less dash about him cleared every one, and shot ahead

3*4

AGAINST THE STREAM 305

in the swift, smooth, sullen water above the fall. There was
pathos in the passiveness with which the unsuccessful
swimmer let himself be swirled back to the eddies at the
foot of the ladder. Like a spent horse, he could no more ;
but one knew that he was setting his teeth, so to speak,
for the next rush. One wished to know many things —
whether the males or females got up first, whether it had
become a matter of course to the old salmon, how often the
young grilse required to try, and how they felt when they
were baffled.

There are many ways of looking at such sights. The
practical point of view was well represented by the crowd
of town's boys. How many of them had " cleeks " n
their trousers, no one could tell ; but there were rumours
of a suspicious abundance of appetising fish - suppers
in the town. Probably the Game Laws do express a
certain sense of the sportsmanlike, and it seemed a
shame to cleek a "breathless" fish which a side current
carried shorewards. Yet as their fathers and grand-
fathers had held these to be part of the year's spoil, the
youths naturally resented any attempt to prevent them
from doing what had always been done. And there were
many fishes, for we were able to count fifty-one leaps in a
minute. It is easy to be " moral " about poaching after a
good breakfast, but what would the natural man have done
had he been hungry ? There is delight in the cutlets of
even a fasting salmon, and there is a monotony about
porridge and respectability.

The erudite scientific person was also represented. He
did not care for salmon-cutlets. Protoplasm and the
centrosomes for him ! Given, he said, the force of the
current, given an integrated aggregate of complex molecules
(called for convenience Salmo salar), with an inherited
nervous mechanism, explosive muscle-cells, and all the rest
20

306 THE BIOLOGY OF THE SEASONS

of it, and the leap of the salmon is a function of the velocity
of the water and the metabolism of the fish.

This is true in a way, but it is hardly the whole truth.
Unless p be taken to mean more than is usually granted,
it is a dull, one-sided fact. One misses in the formula any
recognition of the fact that the fish is also a spirit — a water-
sprite. It has a consciousness, an experience, some sort of
mental life, strong desires, and that byplay of activity
which we call emotion. It is a personality of a fishly sort.
We must admit that it cannot reason, this Salmo solar ;
its intelligence is of a low order ; but if it thinks little, it
feels much ; it is a water-baby. What surmounts the fall
is no torpedo, no automatic machine — that idol which
modern man projects upon Nature ; it is a creature with a
history — a unified history — remembering its cradle, liking,
in a cold-blooded way, its mate, enjoying its struggle against
the angry strength of the river.

There is no excuse for the naturalist who forgets to-day
what was said so long ago — " All flesh is not the same
flesh : but there is one kind of flesh of men, another flesh
of beasts, another of fishes, and another of birds " ; and we
do not forget. But there is more than one touch of flesh
which makes the whole world kin. To name one, phrase it
as you please, it is the genetic impulse that calls the salmon,
as it calls us. The melody is personal, varying with each
grade of being, but the motif is universal.

Phenomena are all very well, but why not see them also
as noumena sub specie ceternitatis ? Then the salmon
pressing up the stream, careless and thoughtless if you will,
but feeling the living hand of the past upon them, feeling
the promptings of the present — vague analogues of what we
call "love" — dimly perceiving the waters far ahead where

AGAINST THE STREAM 307

last year they found pleasure, become prototypes and
emblems of the great endeavourers who are the centres of
our hero-worship — even of those

" Who, rowing hard against the stream,
Saw distant gates of Eden gleam,
And did not dream it was a dream."

BOOK IV.— WINTER

BOOK IV.— WINTER

IMPRESSIONIST SKETCH

A TRUE judgment as to the vital import of a Northern
Winter is not altogether easy for us, here and now.
It is not so easy for us, apart from our science, as it was
for our ancestors, for we have become more and more
cunning in ignoring Winter. What was in early days
expressed in shelter, a fire, warm clothes, and fatty food
has become a fine art with us. It is not so easy here as it
is farther North to realise the Winter, for, in spite of all
our grumbling, a British winter is usually a mild affair.
It is not so easy now as it once was, for even our worst
winters are but far-off echoes of the Glacial Epoch, when
Winter not only conquered Summer in the annual contest,
but remained victoriously dominant throughout the year,
and for long ages. Thus it is evident that to do Winter
justice we have need to question the Lapps and Samoyedes
and other dwellers in the Far North, or, where these have
not voices that we can understand, explorers like Nansen
and Peary ; we must think of the Polar Regions, of Alpine
life above the snow-line, or of that dark, silent, plantless,
intensely cold world — the Deep Sea — where the spel]
of Winter is unrelieved and perennial ; and we must let
our imagination travel back to the Ice Ages — the Ages
of Horror — during which whole faunas shuddered. Unless
we make some such efforts, which we can only suggest,

3"

312 THE BIOLOGY OF THE SEASONS

we are likely to estimate the power of Winter too lightly,
and fail in seeing to what degree it casts a spell, often a
fatal one, upon life.

Let us put it in another way : To realise what Winter
may still mean for us, we must leave the city and visit the
open country, especially to the North. We must see, not
the gaiety of the artificially heated town, but the frozen
fiord ; not men muffled up in beaver coats, but the beavers
themselves in their frozen dam; not the winter-garden,
but the trees in a garb of ice ; not the cattle chewing in
their stalls, but the dead birds lying under the trees.

II

A true appreciation of Winter was long since expressed
in the story of the Sleeping Beauty. She was richly
dowered with vigorous beauty and joyous grace, but all
her gifts were shadowed by the foreboding of early death.
This doom, however, was transmuted into a kinder spell,
which bound her to sleep, but not to dying. All care not-
withstanding, the spindle pierced her hand, she fell into
deep sleep, whence at last the Prince's kiss served for her
awakening. Various commentators apart, the meaning
is plain : vThe Princess was our fair earth with its glow of
life, her youth was Summer — often shadowed, the fatal
spindle was the piercing cold, the spell-bound sleep was
Winter's long rest, the kiss that awakened was the first
strong sunshine of Spring. The beautiful old story is
literally one of the " fairy-tales of science."

In the same way, though there is much else in the
myth, Balder the Beautiful represented the virility and
vitality of the sunny Summer ; and the twig of gloom, the
mistletoe, which flourishes and fruits in Winter, and was
fatal to B alder , was the emblem of the freezing cold which

IMPRESSIONIST SKETCH 313

so often brings sudden death or the quiet peace of sleep.
A similar interpretation holds for the subtle story of
Proserpine.

Ill

But let us turn from fancy to fact, though, perhaps,
there is sometimes more trueness to Nature in the fairy-
tale than in scientific text-book. The astronomers tell
us of the general law that on either hemisphere 63 per cent,
of the total heat of the year is received during Summer
and 37 per cent, in Winter ; but this statement, funda-
mental as it is, hardly expresses the full force of the case.
For the astronomers are thinking, and, from their point
of view, rightly, of a year with only two seasons ; therefore,
as we are dealing with four, we must refer part of the 37
per cent, received in Winter to late Autumn and part to
early Spring, leaving Winter poor indeed.

The same authorities also tell us that the length of
Summer and Winter is variable ; thus we have now about
1 86 days of Summer and 179 days of Winter (in the two-
season sense), while it is but a geological yesterday since in
the Ice Ages the Summer lasted for only 166 days, and 199
lay in the grasp of Winter. This is again very important,
for the total amount of warmth received has obviously to
be divided by the number of days in the season to give
us a numerical expression of the average daily sun-heat
at any given time. Yet, finally, this must not hide from us
the commonplace of experience that it is not the average
temperature which, so to speak, says yea or nay to this
or that form of life ; it is rather the occurrence of certain
maxima and minima — a terrible heat-wave or a week of
very frosty nights. After one exceptionally cold night
some years past, over two hundred birds were found dead
round the stacks in a small steading.

314 THE BIOLOGY OF THE SEASONS

IV

To the cold and the scarcity of food which Winter in-
volves in this and more northerly latitudes there is great
variety of response or reaction on the part of living creatures.
Of this variety let us take a few illustrations. Thus most
of our birds, emblems of freedom, escape the spell by
flight ; and, though death is often fleeter still and overtakes
them by the way, there can be no doubt that the migration-
solution is an effective one. Literally, they have no
Winter in their year. Among those partial migrants who
are hardy enough or foolhardy enough to risk remaining
with us in Winter the mortality is often disastrously high.
Winter after Winter may be weathered, and then, as we
have already noticed, there may be a severe thinning of
the ranks.

Other creatures, unequal to the long and adventurous
journeys of the birds, retire into winter-quarters, in which
they lie low, awaiting happier days. Thus the earth-
worms burrow more deeply than ever below the reach of
the frost, the lemmings tunnel their winding ways beneath
the icy crust of the Tundra, all manner of insects in their
pupa-stages lie inert within cocoons or other protective
envelopes in sheltered corners, the frogs bury themselves
deeply in the mud of the pond, and the slow-worms coil
up together in the penetralia of their retreats — all trying
to get below the deadly grip of the frost's fingers.

Others, again, such as the Arctic fox, the mountain hare,
the ermine, the Hudson's Bay lemming, and the ptarmigan,
face the dread enchantment of Winter, but turn paler and
paler under the spell, until they are white as the snow
itself — a safety-giving pallor. They have a constitutional
tendency to change their colour, and the external cold
pulls the trigger that sets the process at work. It is well

IMPRESSIONIST SKETCH 315

known of Arctic fox and mountain hare, for instance, that
the degree of whiteness varies from year to year with the
intensity of the Winter. As for its utility, this is, at least,
twofold — the white dress is of service in the chase or in
flight, while, on the other hand, it is the most economical
and comfortable dress for a warm-blooded animal when
the external temperature is very low.

Man, himself, gets inside other creatures' skins and
bids defiance to weather, or, having in his cunning tapped
one of the earth's great stores of energy — a coal-bed — sits
comfortably by his hearth, gloating in what is really the
warmth of a larger sun than that which now sends him
in the wintry months too little cheer. But his indiffer-
ence to the Winter has, in part, a very precarious basis,
as a prolonged coal-strike shows ; it is, in part, a privilege
of the few, as a glance along our streets suffices to prove ;
it is, in part, merely local, as a short journey northwards
may convince us. Man, too, like the birds, often migrates
even from our British mildness to a sunnier South, and he
knows, like many a creature of less high degree, of winter-
refuges, whether in a poorhouse at home or a " pension "
abroad.

To many organisms, both of high and low degree, the
alternative comes — to sleep or die. The spindle cannot
be escaped, the cold shall pierce like a sword — but sleep !
and it may be well. Of this " sleep " there are, indeed,
many degrees, from the mysterious latent-life of frozen
seeds and animal germs to the almost equally mysterious
true hibernation of marmot and hedgehog. Often, too,
it must be admitted that what began in slumber ends by
becoming sleep's twin sister, Death. Yet we understand
so little of these more or less dormant states in their rela-

3i6 THE BIOLOGY OF THE SEASONS

tions to one another, or, indeed, of any one — even sleep —
by itself, that we must be content here to use the word
somewhat loosely when we say that Winter is to many
forms of life a sleep-bringer.

The great hypnotist lifts his hands, and the sap stands
still in the tree, and the song is hushed in the bird's throat ;
he makes his passes, and growth ceases in bud and seed, in
cocoon and egg ; he breathes, and sleep falls upon marmot,
hamster, and hedgehog, upon tortoise, frog, and fish,
upon snail and insect ; he commands — his voice is the
North Wind — and the water stands in the running brooks,
and the very waves of the fiord are still. Even in our
own mild country, is not the freezing of a considerable
part of Loch Fyne upon record ?

Apart from the state of latent life — in which a paste-
eel, for instance, may lie neither actively living nor really
dead for fourteen long years, and seeds for several decennia,
though not since the days of the Pharaohs — there is no
form of sleep so near to death as this to which the Wizard
of the North commands the true hibernators. Somnolence
penetrates to the deepest recesses of the creature's con-
stitution, as the expert histologist has shown us in his fine
study of the minute structural changes observed in the
cellular elements of the sleeping hedgehog.

The heart of the hibernator beats feebly and somewhat
irregularly, the breathing movements are at long intervals
and very sluggish, the food-canal is empty, income is
(apart from oxygen) at zero, and expenditure is but little
more. The sleeper may be immersed in water for twenty
minutes, or subjected for some time to noxious gases, but
without apparent effect in either case. The fat, accumu-
lated in days of plenty, is slowly burnt away, sustaining
in some measure the animal heat. In the warm-blooded
mammal the normal power of keeping an approximately

IMPRESSIONIST SKETCH 317

constant body-temperature is in abeyance for a time,
and the body cools to a degree which in ordinary life
would be fatal ; irritability wanes to a minimum ; the
ordinary reflexes are at most faint, and the creature
steadily loses weight. The real wonder is that it keeps
alive.

The slumberers differ much in the soundness of their
sleep. Thus there are light sleepers, like the dormouse,
the harvest mouse, and the squirrel ; and heavy sleepers,
like hedgehog, hamster, and marmot, or like the tortoise,
whom the crack of doom would scarce disturb. But
it and all other sound sleepers must yield to the snail
who overslept himself so far that when he awoke it was
in a case in the British Museum, wherein he bore a ticket
already many years old. There was another Rip Van
Winkle snail who awoke to find himself an extinct species ;
but that, as they say, is another story !

After we allow for the tendency that cold has to produce
coma, of which Alpine travellers have told us tales, for
the drowsiness which is said — let us hope it is true — to
take the edge off starvation, and for the sleepiness in-
duced, e.g., in church or lecture-room by confined atmo-
sphere, of which no proof is required, there seems to be need
of further physiological explanation. It has been shrewdly
suggested that the retention of waste-products during
hibernation induces a state of "auto-intoxication" — a
drugging or poisoning of the system with its own excre-
tion, a banking-up and smothering of the fire of life with
its own ashes. It seems a plausible view that this will
tend to keep the sleepy sleeping, and the idea may be
hazarded that one of the reasons why plants are not more
wideawake is just this retention of nitrogenous waste-
products. For it is well known that plants do not get rid
of these. The same is in a measure true of the sea-squirts

3i$ THE BIOLOGY OF THE SEASONS

or Ascidians, which in their adult life are sedentary and
sleepy animals, curiously plant -like in a number of ways,
notably in the mantle of cellulose which invests the
body.

The general import of hibernation is in most cases plain.
Life saves itself by ceasing to struggle, by retiring within
its entrenchments. Death is baffled by a deep device,
in which activity virtually ceases without life itself being
surrendered. Hibernation is the finest organic illustration
of the policy of " lying low."

Yet there are other aspects of the Winter's sleep. To
some it is a time of repair — a long night — after the nervous
fatigue of a long day. Thus it is not difficult to understand
that, quite apart from the weather, it is good that the
queen humble-bee should sleep through the Winter, just
as it is well for the fisherman that he should loaf after
the storm. In short, we return to our main thesis, that
life is rhythmic, and that the seasons punctuate it.

To others the sleep is in some measure a preparation
for a new day. Thus in the seeds which slumber in the
earth, each a young life, there is a rotting away of the
husks which the delicate embryo could scarce burst, and
later on there are processes of fermentation, by which
the legacy of hard, condensed food-material is made
available for the young plant. That it is not merely the
unpropitious weather and the hard soil which make it
necessary for the seeds to remain asleep may be proved
by experiment, and it is also proved by the fact that not a
few normally lie dormant for several years. Similarly,
within the cocoons there lie the chrysalids, quaintly
mummy-like and inert to all appearance, but slowly
undergoing that marvellous transformation, the result
of which is the winged butterfly — the Psyche.

IMPRESSIONIST SKETCH 319

VI

It seems a true paradox that one of the great facts in the
Biology of Winter is the frequency of Death. Not that
there is any season when Death is not busy, or any oppor-
tunity which he does nor seize ; he picks and chooses
among the newborn of the early Spring, he lays pitfalls for
the adolescent, he thins the ranks of Summer's industry,
he puts in a full stop at the limit of growth, he forces open
the door which Love seeks to keep closed, he harvests in
Autumn ; but it is in Winter that his power is most felt.
It is the time of least heat, least light, least food, and,
therefore, of least resistance and lowest vitality.

The influence on plant-life is most obvious and direct ;
a large fraction of the income of radiant energy is cut off,
the water-supply is also reduced, and there is further risk
that the frost cause bursting of cells and vessels within the
plant just as in our houses. The diminished vigour of
plant -life means less food for the animals, and on them, too,
the relative lack of warmth and sunlight has a directly
disastrous effect. Given, as Shelley pictures,

" A winter such as when birds die
In the deep forests, and the fishes lie
Stiffened in the translucent ice, which makes
Even the mud and slime of the warm lakes
A wrinkled clod, as hard as brick,"

the decimating influences are perceptible on every side.
Thus after a hard Winter there is eloquent statistical
evidence forthcoming of the mortality from moor and
forest, lake and seashore. Winter is indeed a time of rest
and sleep, but as surely of elimination and death.

Death always means the irrecoverable cessation of
bodily life, but it has many forms — violent, microbic,
and natural — each, again, with its subdivisions, and it

320 THE BIOLOGY OF THE SEASONS

cannot be said in any off-hand way that the rate of mortality
from every form of death is greatest in Winter. Thus there
is an interesting seasonal distribution of disease, of suicide,
and even of accidents. Yet the general induction appears
safe enough that in northern lands Winter is the time of
severest elimination. Thus the season which is apt to seem
dull to the field-naturalist is full of interest to the evolu-
tionist. The hedgerows are bare and the woods silent,
the pools are clear and apparently devoid of life, the shore is
comparatively barren, even the sea has lost certain elements
of its wonted abundance. And, though much of this
scarcity is only apparent — life lying low, or asleep, or on a
journey — we must allow that in many cases life is altogether
sped. Proserpina has gone down to Hades. Balder the
Beautiful is dead. We have, in short, to recognise the
inexorable process of Natural Selection, whereby the
relatively less fit to the conditions of their life tend to be
eliminated, i.e. tend to die before the normal time, and to
leave behind them less than the normal number of offspring.
Winter is the time when the tree of Life is most rigorously
pruned. And this is in many cases well ; for, hard as the
saying is, the elimination of individuals is one of the con-
ditions in the persistence of a strong race.

In our study of the decadence of Autumn, we spoke of
the death of individuals, and of the consolation which is
offered in the persistence of the race, but we cannot think
long over such matters without recognising that the race
itself may perish. We need only reverse the hands of the
geological clock a few minutes, as it were, to be convinced
of this. We need only go back to the more recent Ice Ages —
the ages of Winter's tyranny — which are not long past, as
time goes. Indeed, we need not leave human or even
modern history at all to find sadly abundant illustrations
of lost races.

IMPRESSIONIST SKETCH 321

Keeping, however, to recent animal history, where are
the bears who had their dens in Athole, or the wild boars
of the great Caledonian forest, or the busy beavers who cut
their logs in the Pass of Killiecrankie, or the white bulls who
wallowed in the dark waters of the hidden tarns, or the
wolves with which Wales paid her tax to King Edgar ?

Or, again, where are the early companions and rivals
of our forefathers in Britain — the cave-lion, the cave-bear,
the cave-hyaena, the shaggy mammoth and the woolly
rhinoceros ? We know them only by their bones in the
caves, though it may be that our inheritance still includes
some of the hardihood, wisdom, and gentleness which they
and others like them helped to work out in man.

Or, going much further back, where are the delicately
beautiful graptolites, the quaint trilobites, the giant sea-
scorpions, the ancient heavily-armoured fishes, the giant
amphibians, the monstrous terrestrial reptiles, the huge
sea-serpents or Pythonomorphs, the flying dragons, the
toothed birds, the old-fashioned early mammals. The
most powerful, the most fertile have not been spared, even
those which seem as though they had been built not for
years but for eternity, have wholly passed away without
leaving any direct descendants to-day. This is no case of
leaves falling from off the tree ; it is a lopping of branches.

For some of these lost races, competition was doubtless
too keen — they outlived their prosperity and went to the
wall ; for others, the force of changing circumstances was
too strong — they were not plastic enough to change ; for
others, perhaps, over-specialisation or gigantic size or
feverish activity was fatal ; for others, it may be that their
constitution was in some critical respect at fault, and that
they went down to destruction, as Lucretius finely phrased
it, " hampered all in their own death-bringing shackles."

However the extinction came about, it was thorough-

21

322 THE BIOLOGY OF THE SEASONS

going, and these lost races have been blotted out as though
they had never been. We cannot console ourselves with
any notion that such disappearance is a misnomer for
transmutation into some nobler form ; that may be true
of certain species, which have direct descendants to-day,
but it is not true of what we call lost races. Nor is there
consolation in the notion that the atoms which were once
wrapped up in that whilom bundle of life known as the
ichthyosaurus may now be part and parcel of us ; for we
feel that those particular combinations which we have called
lost races — those smiles of creative genius — have gone, gone
as utterly as the snow-wreaths of yester year.

Thus from the elimination now observable around us
in this wintry season our thoughts naturally pass to the
great world-wide process, continuous since life began,
which embraces us also in its inexorable sifting. It does
not, indeed, explain us, nor the organisms we know, any
more than the pruning-hook explains the tree ; but given
life and growth, we cannot understand our history or that
of living creatures apart from elimination. In short, we
need our Winter to explain our Summer, and this perhaps
is the only consolation which the biologist can suggest to
the discontented, that the alternation of Summer and
Winter is part of the mechanism which has made the
history of the world a progressive development.

THE NATURAL HISTORY OF REST

A N outlook on the animate world in Winter impresses
f~\ us with the rest fulness of living creatures. Seeds
are resting in the ground, buds are resting on the boughs,
chrysalids are resting in sheltered nooks, the frogs are
resting in the mud by the pond-side, the hedgehog is
resting amid the woody wreck. Winter in North Temperate
countries is a time of rest. Vital activity gradually in-
creases in the Spring months, and reaches its climax in
Summer; in Winter we see the down-grade of the curve,
which often never re-ascends, but goes lower and lower
to the nadir of death.

The physical basis of rest is to be found in the fact of
the conservation of energy, for no material system, how-
ever wonderful, can create energy. It takes in, it gives out,
it transmutes, but it cannot create. Therefore when it
expends energy in work, and exhausts its store, it must
stop or rest till it gets more. But the matter is compli-
cated by the external rhythms of day and night, of months
and tides, of seasons and cycles of years, to which it has
been the business of living creatures for millions of years
to adjust themselves as harmoniously as possible. Thus
we find long periods of expenditure without appreciable
income, which are startling from a mechanical point of
view.

We are led from many sides to recognise that the living
creature is different from any inanimate machine. If it

is a machine, it is a self-regulating, self-stoking, self-

323

324 THE BIOLOGY OF THE SEASONS

adjusting, self -increasing, self -repair ing, self-reproducing
machine. In fact, in all this it is so marvellous, so ultra-
mechanical, that we are sometimes apt to treat it, including
ourselves, as if the law of the conservation of energy does
not apply. But there is no reason to believe that the
student, for instance, who invokes what he calls his " will-
power " (a most useful habit within limits) when he ought
to go to bed, or who says that he is " too busy to be tired "
(usually a short-lived boast), is any exception to the general
fact of the conservation of energy, and of its tendency
to degradation into that unprofitable mode of motion
which we call diffused heat.

We are tempted to make exceptions of ourselves in
this restless overworked age, partly because, by traditional
dualism, we often think of life too mystically, as if it
were a tireless entity. We call upon the resources of the
spirit to flog the jaded flesh. But on any theory this is
fallacious, except for a temporary spurt. For if the
resources of the spirit are reserve powers of the nervous
system accumulated in days of rest, such as Sundays, then
they are strictly limited. And if they are altogether
metakinetic spiritual powers, even then they can only enter
into the vital equation by controlling the ordinary corporeal
energies, which, by hypothesis, were approaching the limit
of exhaustion. Perhaps it is wiser to recognise that to
make an antithesis of body and soul is a medievalism.
The living organism is a unity.

But we are in a manner right in making a distinction
between the inanimate system, where the equation showing
income and expenditure is always relatively clear, and
the animate system, where the proof of the conservation
of energy is a much more difficult matter. We have
often kept little water-mites for long periods in glass jars,
where the supply of food must be small in the clear water,

THE NATURAL HISTORY OF REST 325

and yet whenever we look at these water-mites they are
dashing about with headlong velocity, expending energy
without apparent exhaustion, continually rushing and
hustling, as if they were going to catch a train. That
they ever catch anything we do not know. We suppose,
indeed, that there is some microscopic food in the water,
and that the mites sometimes rest when we are not looking
at them, but they have always seemed to us fine instances
of what is in some degree true of all living creatures —
they have an extraordinary power of accumulating energy,
and of accumulating it acceleratively. We know that
when we heat a bar of iron, or charge a Ley den jar, or
in any other way pass energy into an inanimate system,
the transfer becomes more difficult as we proceed ; there is
more and more tendency to the dissipation of the energy
accumulated, and there are effects retardative of further
transfer. But, as Prof. Joly points out, it is the opposite
with living creatures, and this is their great dynamic
peculiarity. They have extraordinary powers of storing
energy, and on the strength of their stores they may go
on without food or rest for many days. It is a realisation
of this power which leads many to deny the claims of
rest, and to forget that living on capital has its limits.
But although such periods of defiance may be happy and
brilliant, it is a perilous habit.

When we contrast the animate and the inanimate after
this fashion, there rises in the mind the remarkable fact
that the sublimest examples of unrestingness are afforded
by the movements of the heavenly bodies, and of the
earth itself. For how many millions of years have all
these revolutions been going on, without haste, without
rest ? And what of that mysterious, unceasing movement
of our whole solar system towards an unknown goal in
space ? But the point is, we suppose, that these heavenly

326 THE BIOLOGY OF THE SEASONS

bodies are not, after all, doing very much. Perhaps the
mite is more of an agent than they ! It is expending
more energy relatively to its system, and it is not simply
going on in virtue of initial momentum. It is busy. The
heavenly bodies that do much in the way of giving off
energy, as our sun does, must some day rest. We have
only to look up to "yon dead world the moon" to see a
world at rest, though it is swept along unceasingly.

Our thoughts also travel readily to the peculiar rest-
lessness of radium. Incessantly, and without appreciable
loss, the grain of radium pours forth heat and light. One
kind of radium ray is said to consist of little streams of
infinitesimally small corpuscles, which travel at the rate
of 100,000 miles a second. But after all, the radium
grain is being slowly used up ; it gives off a something
which is being turned into something else ; it finds a
relative rest in disintegrating.

Let us linger still over the contrast of the lifeless and
the living. Throw a ball of potassium on the basin of
water, and it rushes about, fizzing and flaring like a thing
possessed, but in a minute all its marvellous activity is
over, its life as such is sped. But watch, by way of
contrast, the similar movements of the little whirligig
beetle on the pool ; it goes on for a while, like a little
water-sprite, darting here, there, and everywhere over the
surface, expending much energy. Unlike the potassium
pill, however, it does not go out — for a long time at least.
When the gong to which it is adapted sounds, it ceases
to move, and begins to munch. It re-stokes its engine.
When it is tired, or when the external curfew to which
it is adapted tolls, it takes a rest. So it persists for weeks
and months, and, if it get big rests, it may be for years. In
fact, whether they be whirligig beetles or the trees of the
forest, living creatures are material systems which have

THE NATURAL HISTORY OF REST 327

the power of taking rests. This is part of their essential
secret. Conversely, the man who loses the power of taking
rest becomes a machine.

We must not, of course, think of the need for taking
rests as in any way a new need, which has arisen in a
restless age. The need for rest is primitive, and the resting
habit has its roots in the remotest past, and its reason in
the nature of things.

The argument is obvious and trite. Since all activity,
mental as well as bodily, emotional as well as intellectual,
involves expenditure of energy, the rate of work must
periodically diminish, there must be relative rest, there
must be time for the most primitive form of rest which
consists in re-stoking the living engine. There are some
minute unicellular animals which are said to continue to
move about as long as the store of a certain substance
within their cell holds out. When that store is exhausted
their motor activity is at an end for the time being. Before
it begins again, they must accumulate more fuel for the
living fire. Here the conditions of rest are seen in their
simplest expression. There must be at least a rest for
eating — but we do not need to go far to see how much
even this is grudged by " the Minister and Interpreter of
Nature."

Other needs for rest have gradually arisen. There
must be time for the fuel to warm up, for the food to become
thoroughly available. But there is much more than this.
The activities of daily life, including the stoking itself,
involve wear and tear of the vital machinery. There must
be rest for repair. In the simplest animals this wear and
tear is reduced to a minimum, or the repair is approximately
perfect, so that little rest is required. They do not seem
even to need to die. In more complex animals, however,
the wear and tear is greater as life becomes fuller, the

328 THE BIOLOGY OF THE SEASONS

agencies for repair have a more difficult task, especially as
regards hard-worked organs, such as heart and brain, liver
and kidneys. Rest becomes more and more imperative.
Often the only alternative is death.

Rest is also required when new adjustments have to
be made in the body, when there is to be any radical re-
construction, as in the metamorphosis of the grovelling
earth-bound caterpillar into the free-flying Psyche or
butterfly, or when there has been a relatively trivial change,
such as sloughing off an old husk, or when wounds have
to be healed. In Hilton's well-known Rest and Pain
the therapeutic value of rest is demonstrated.

We need not linger over the analogies which the facts
suggest for our guidance, and that not merely on the
physical but also on the psychical plane. If we are to be
kept whole or if we are to be healed, if we need to moult
our worn-out armour and present a new front to the world,
if we are to reconstruct our system of experience, if we are
to have any metamorphosis, the analogy of Nature points to
the fact that we must rest. In many cases, as we have
seen in a previous study, the larval insect returns in its
pupa stage to an almost embryonic simplicity, but the
outcome of its rest is its conversion into an emblem of joy
and freedom. It is born again.

It is obvious, especially in the animal kingdom, that
the need for rest is often bound up with the giving origin
to new lives. The queen humble-bee, after its arduous
maternal labours, sleeps through the Winter. So the birds
that fly southwards, after an exceedingly busy Summer,
find a time of relative rest and ease in warmer lands
where food is abundant and easily procured.

As we hinted in one of our Spring studies, there seems
good sense in what Professor Whitman remarks in connec-
tion with the brooding of birds. The supply of heat to

THE NATURAL HISTORY OF REST 329

the eggs is "an incidental utility that had nothing to do
with the nature and origin of the instinct." To find the
real meaning we have to go farther back, and then we see
that a recuperative rest naturally follows an exhausting
reproductive period. Far below the level of birds, long
before there was any incubation, we find animals resting
beside their laid eggs or beside their young ones. We
grant that this habit also afforded protection, and that it
may also be an expression of parental love, but the point
is that resting is primitive and incubation derivative.

Even in the plant world we see the contrast between
the literal hard work of the vegetative period, when every
leaf is a busy laboratory, and the flowering and fruiting
period, when the activity is not in getting but in trans-
muting what has been already gained. And now in
Winter we see the leafless trees having, as it were, a deep
sleep.

Let us now turn from the general conditions which make
rest necessary to the function of the nervous system in
this connection. The nervous system is very sensitive to
fatigue and to the poisoning of the body with accumulated
waste products ; one of its many functions is that of warning
the body when it is time to rest. But at the same time,
as every one knows, the nervous system is extremely
sensitive to stimulus ; it has in some way great resources
within itself ; and thus a practical antinomy often comes
about. The nervous system is often capable of the treason
of urging the body on when the weak flesh would fain rest.
On the one hand, it is a rest-index that automatically puts
on the brake ; on the other hand, it is a spur which incites
the tired steed to further effort. The contradict oriness of
these two functions is one of the difficulties of a healthy life.
Put in another way, the difficulty is that the human resting
instinct is very slightly developed, and that many find it

330 THE BIOLOGY OF THE SEASONS

troublesome to develop a resting habit, which should be
formed early if its full utility is to be appreciated.

Furthermore, the difficulty is complicated by our habit
of damping down the signals which our rest-index gives us.
The extreme signal to rest, as Hilton pointed out, is pain.
That is the use of pain. But long before it comes to pain
we usually get many signals, which we show no little
ingenuity in ignoring. As on the steamers racing on the
American rivers, we manipulate the safety-valve so that its
whistle indicative of over-pressure may not annoy us. There
are many pleasant devices for damping down the rest-
signal which our nervous system is almost always ready to
give us for our good.

A strenuous American is reported to have said : "I
have managed to get a sort of steam-engine into my brain
which gives me little rest, and would wear out my body if
I did not happen to have the constitution of a buffalo/'
This is not exactly how a neurologist would express it, but
the idea is plain, and the confession indicates one of the
dangers of our civilisation, — not of too much thinking,
there is little risk of that, — but that one function of the
nervous system, which is to prompt to action, to excite,
should grow out of all proportion to another function,
which is to inhibit, to control, to quiet, to enforce rest.
Over-conscientiousness, or rather over-narrow conscientious-
ness, may lead to what the American called "a sort of
steam-engine in the brain, which gives little rest." Un-
fortunately for the individual, the busy American's " con-
stitution of a buffalo," which enabled him to endure, is not
so common as might be desired, partly perhaps because
previous generations have taken too little rest.

A Scotch mining engineer, who had spent many years
of hard work in Spain, said that half of his toil was in com-
bating the over-restful habit of the Spaniard. As every one

THE NATURAL HISTORY OF REST 331

knows, the stage Spaniard will never run if he can walk,
never walk if he can sit, never sit if he can lie, and what so
much irritated the engineer from a more energetic climate
was what he called " the everlasting Mariana, Mariana —
To-morrow, To-morrow." But the Spaniard's " Mariana "
has its lesson for the American " with a steam-engine in his
brain," and that lesson is Rest. The Nemesis of disre-
garding it is in the ugly word Neurasthenia, — nerve-fatigue,
over nerve-fatigue, chronic nerve-fatigue, hereditary nerve-
fatigue, — so the dismal story runs till the child is born so
tired that it dies.

One of our strongest instincts is the work-instinct, to
work at what is natural to us, and it is often too strong for
our imperfectly developed rest-instinct, which is almost as
important. A narrow conscientiousness which besets too
many of us says " Work," and we work long after it can be
called day. " We have our work," we say, but we lose
Art, and our work becomes toil. Is there not something
to be said for the Spaniard's "Mariana," or for the Irishman's
advice, " Be aisy ; and if you can't be aisy, be as aisy as
you can " ? This is all the more important since it is obvious
that in many respects our organisms have not kept pace
with our social evolution.

HIBERNATION

IT is instructive to look over the list of British Mammals
and to inquire what solution each offers to the
problem of Winter. The migratory birds' solution of
evading the hard times altogether is not open to any
mammals except bats, and we have few facts regarding their
migration. Some of our mammals lay up stores and do not
hibernate, e.g. the harvest-mouse and the wood-mouse ;
others lay up stores and also sleep, e.g. the field-vole and
the squirrel ; others neither store nor sleep, but turn white,
e.g. stoat and mountain hare ; others neither store nor
turn white, but hibernate, e.g. hedgehog, common shrew,
and bat ; others again do nothing but brave the rigour
of the Winter, e.g. fox and polecat. The mole occupies a
somewhat peculiar position, since it can continue its work
and find food below the reach of the frost ; moreover, it
sometimes makes a store of earthworms which form a staple
part of its diet . The water-shrew is another non-hibernator,
and we can understand this since the thorough freezing up
of rivers or even streams is a rare occurrence. What we
see in going over the entire list is, that those which do not
hibernate have usually some other marked adaptation
to the Winter, such as the habit of storing or of changing
colour. In default of anything of this sort and of a callous
constitution which can defy storm and scarcity, the animal
may save itself by hibernating. It passes into a state when
it can starve without feeling it, it lies low with dulled

sensitiveness instead of fretting itself to death in a struggle

333

HIBERNATION 333

with the Winter, it keeps in hiding when it is not alert
enough to do itself justice, and it gives its body a long rest.

A survey of the Winter-sleepers seems to show that the
life-saving reaction must have arisen by the natural selection
of variants in the direction of the hibernating habit. That
is to say, those that were constitutionally able to assume
a comatose condition when the cold weather set in, yet
without endangering their lives, were the survivors. On
this view we can understand how it is that the hibernating
habit is definitely related to the other habits of the creature
— for instance, why it should occur in the land-shrew, but
not in the water-shrew. It is an adaptive character.

But although the hibernating habit may be exhibited
by one species of mouse and not by another, being in no
way wrapped up with a special kind of constitution, we
must recognise that it means in the higher reaches of life
a somewhat delicate adjustment of an ordinary constitu-
tion. When a mammal whose constitution is not adjusted
to hibernation falls into a cold -coma it is not likely to
awaken. This is familiar to us in the case of man and his
stock.

WINTER SLEEP OF COLD-BLOODED ANIMALS

Many cold-blooded animals, which take on the
temperature of the surrounding world, pass into a leth-
argic state in Autumn. Professor Semper says that they
are " lulled to sleep by the falling temperature/' but it
must be understood that their condition is very different
from sleep as we know it. Often it seems more like
" Sleep's twin-sister, Death," so thorough is the stoppage
of all activity. The common edible snail, Helix pomatia,
closes the door of its shell with a hard lid of lime and slime,
and keeps the door shut for four months. All this time
it is fasting ; its respiration must be extremely sluggish

334 THE BIOLOGY OF THE SEASONS

through that calcareous wall ; its heart, even when the
shell is broken, is beating very feebly. This is far below the
level which we know in sleep. How much more is that
the case with, for instance, the pupae of butterflies and
other insects, in which the whole structure of the larva
has been broken down and is in process of slow recon-
struction. No doubt all these states are at different
levels on an inclined plane, but there is a great contrast
between the disorganised pupa, which sinks back sometimes
till it is practically a winter-egg that has to be hatched a
second time, and the comatose but quite intact snail.
There is another great contrast, between the comatose snail
and the sleeping dormouse.

PHYSIOLOGY OF HIBERNATION

The physiology of hibernation is still very incomplete,
but a few general statements may be ventured : —

1. It is very frequently the case that some store of re-
serve material exists within the animal which is consumed
during the hibernation, serving, for instance, to sustain
the animal heat. Thus a store of fat, accumulated when
food was abundant, may serve, as it were, to keep the
fire "in," though it cannot do much more.

2. A second general statement may be ventured, that
hibernating animals show a very marked slackening of
all the vital functions. The heart beats feebly and ir-
regularly ; the breathing movements are " shallow and
infrequent, sometimes coming practically to a standstill " ;
there is no excretion from the kidneys, or next to none ;
the usual muscular reflexes are weak, and the senses are
not readily stimulated. In short, the whole metabolism
of the creature is at a very low ebb.

3. Very significant is the fact that in hibernating

HIBERNATION 335

mammals there seems to be a suspension of the normal
" warm-bloodedness," or the power of retaining an almost
constant body-temperature. To appreciate this, a short
digression is necessary. The animal heat of the body is
mainly due to the chemical processes involved in the
contraction and life (apart from contraction) of muscle,
the secretion of glands, the oxidations in the blood, and
even in the work of the brain. There is necessarily a
similar production of heat in the cold-blooded animals,
but they have no physiological adjustment for con-
serving what they produce. They are thus dependent
on the temperature of the surrounding medium, towards
which they always approximate. In warm - blooded
animals, however, there is a somewhat intricate nervous
mechanism which adjusts income and expenditure of heat,
regulating both the heat-production and the heat-loss.
The passive muscles, for instance, can be incited if need
be to produce more heat ; or, on the other hand, a dilation
of blood-vessels and a flow of sweat may cause the animal
to lose more heat. And this automatic regulation is so
smooth in its working that the body-temperature of birds
and of mammals remains constant, year in year out,
except in peculiar cases, such as the fledgling in the
deserted nest which has not got its thermotaxic mechanism
established, or the fevering animal in which the mechanism
goes out of gear, or the birds among the snow which have
their regulating mechanism worn out by the hopeless
attempt to respond to the prolonged exposure, or, lastly,
the hibernating mammals.

In the hibernating mammal, what happens is, that
as the outer world gets colder and colder, the heat-regulat-
ing mechanism ceases to act, and the creature is saved
from the collapse consequent on a certain defeat, by be-
coming temporarily cold-blooded (or poikilothermal). Its

336 THE BIOLOGY OF THE SEASONS

temperature ceases to be constant, and follows the fluc-
tuations in the external world. Meanwhile the creature
sleeps. Should the external temperature fall too far, the
sleeper may never awaken, or it may waken suddenly
and make violent efforts to get warm before it dies.

Horvath made the interesting and important observa-
tion that a zizel, Spermophilus citillus, lying in its winter
sleep, always has nearly the same temperature as the
surrounding air. " In one case the temperature of the
room was 2° C. above zero, and a thermometer inserted
in the rectum marked exactly the same degree ; in another
experiment the animal was sleeping in a room at about
9° to 10° for several days, and its body (in the rectum) was
at 8-4°. This shows that during their Winter sleep warm-
blooded animals become truly cold-blooded ; at any rate
this is true of the zizel, since its temperature corresponds
with that of the surrounding atmosphere/' l

4. In his remarkable work on The Natural Conditions of
Existence as they affect Animal Life (1881), Professor Karl
Semper called attention to the value of Horvath's studies
on hibernating mammals, referring to two in particular:
"It is usually supposed that the awakening of winter-
sleepers is occasioned by a rising temperature ; but in
Horvath's investigations this was never the case ; during
two hours and forty-five minutes, which, in the one
experiment communicated, were needed for complete
awakening, the temperature of the room remained exactly
the same — 10° C. — as during the three previous days when
the animal was still asleep. This proves that the waking
up must be caused by some internal cause which we do not
yet know."

"But his other observation is far more remarkable;
namely, that during the awakening, the body-temperature
1 Semper 's Animal Life, p. 112.

HIBERNATION 337

rises rapidly, and much more rapidly during the second
half of the process than at the beginning ; for instance,
in the experiment which is given in detail it rose
in the first hour and forty-five minutes only about
6-6° C., and in the following fifty minutes about 17°. This
remarkably rapid increase of body-heat took place, more-
over, without any vigorous movements, which might
otherwise have been supposed to cause it — even the
rapidity of breathing showed no increase corresponding
to the rise of temperature."

In relation to our general thesis that " Life is rhythmic,
and that it is punctuated by the seasons and other external
periodicities/' Horvath's results are of much interest.
Much more requires to be done, but they seem to suggest
that an internal periodicity has been definitely established,
which now runs its course with some degree of autonomy,
apart from external stimuli. The sleeper may awaken
constitutionally, whether the Spring be warm or cold, just
as Q man may awaken after his usual amount of sleep
whether the morning be light or dark. But more facts
are required.

It may be, as Semper pointed out, that the problem
is complicated by the nutritive condition of the hibernator.
Thus Dr. August Forel, famous for his studies on ants,
believed that influences determined by food were more
important than those of temperature. " A dormouse
that he kept went to sleep even at a high temperature of
the air, in August and September, and slept as soundly as
in a true winter sleep, while its body temperature was
never more than a few degrees higher than the air."

There is much that is obscure in the physiology of
hibernation, but several general facts stand out clearly.
It is a very effective life-saving expedient, — an abandon-
ment of the struggle to make ends meet, a banking up

338 THE BIOLOGY OF THE SEASONS

of the fires of life so that there is extremely slow com-
bustion,— and it works well as long as the external tempera-
ture does not fall below +1° C. It is probably also very
useful in giving the organs and tissues of the body a long
rest — a rest even from eating. It represents an interesting
reminiscence of a more primitive physiological state when
the temperature-regulating mechanism was not yet well
established in the ancestral mammals. Of this primitive
condition we have a permanent illustration in the Mono-
tremes, which are imperfectly warm-blooded. Thus the
temperature of the Spiny Ant-eater (Echidna) varies with
that of its surroundings through the extraordinary range
of 10° C. — a fine instance of a physiological connecting
link between cold-blooded and warm-blooded. And that
is just what every hibernating mammal also illustrates.

THE WHITE WINTER COAT

\ FAMILIAR human reaction to the conditions of life in
Ji\. winter is a change of dress. We clothe ourselves in
the skins of other mammals, putting on layer after layer of
wool, and, it may be, a fur coat on the top. Similarly it is
known of many mammals that they grow a thicker and longer
coat of hair as the days become colder. But what concerns
us now is the change of colour to white, as we see it, for
instance, in the mountain hare, among mammals, and in
the ptarmigan, among birds. How does this change come
about, and what is its significance ?

In the first place, as to the occurrence of this peculiarity of
changing to white in winter, it is exhibited by distinctively
Northern creatures — the Arctic fox (Canis lagopus), the
Hudson's Bay lemming (Cuniculus torquatus), the ermine
(Mustela erminea), the mountain hare (Lepus variabilis), the
American hare (Lepus americanus), and the ptarmigan
(Lagopus albus). This is interesting, since permanent white-
ness is characteristic of many Northern animals, such
as Polar bear and American Polar hare, Greenland falcon,
and snowy owl. It is probable, therefore, that changing
to white is advantageous for the same reasons as permanent
whiteness.

It is also instructive to notice that some of the mammals
that usually turn white do not always change, and that this
is connected with the habitat. Thus the Arctic fox (Canis
lagopus) does not usually turn white in Iceland ; the
mountain hare rarely changes in Ireland ; and white stoats

339

340 THE BIOLOGY OF THE SEASONS

or ermines are comparatively rare in England. The infer-
ence is that the changes which bring about the whiteness
require at least the stimulus of a considerable degree of cold.
It does not by any means follow that the cold is the direct or
mechanical cause of the whiteness.

To the question, What actually takes place when the white
dress is put on, a fairly secure answer can be given in some
cases. But in other cases we have not as yet sufficient data.
It is well known that the stoat or ermine (Mustela erminea),
which is brownish -red in summer, usually becomes a beautiful
white in winter, all but the black tip of the tail. How is this
effected ? The older naturalists, such as Bell, who wrote on
British Mammals, believed that the brownish-red hairs lost
their pigment and became white, which is not in any way
improbable. But Professor William MacGillivray was one
of the first to doubt the accuracy of this view, pointing, for
instance, to a specimen caught in December, which showed
a mixture of white and brownish-red hairs. " The hairs of
the latter colour were not in the least degree faded, and those
of the former were much shorter, and evidently just shoot-
ing ; so that the change from brown to white would seem to
take place by the substitution oj new white hairs jor those oj the
summer dress." This view has been confirmed by the very
careful investigations of Professor G. Schwalbe.

Several instances of stoats of a brown colour patched with
white, in which the white hairs were of the same length as
the brown, led MacGillivray to think that " sometimes the
brown hairs themselves, on the application of intense cold,
become whitened " ; and of this as an exceptional occurrence
there is some modern corroboration. For in the case of the
mountain hare, in which, according to MacGillivray, the
white winter hairs are due to fresh growth, the investigation
of von Loewis leads to the conclusion that brown hairs may
sometimes be changed, in situ, into white ones,

THE WHITE WINTER COAT 341

In a famous experiment made by Sir John Ross, a
Hudson's Bay lemming was kept in the cabin of the
ship through the winter and did not change colour. But
on the first of February it was exposed on deck and it had
several white patches next day. It turned white in a week,
and died a few days afterwards. In this case the blanching
must have been due to a change in individual hairs, such
as sometimes occurs very rapidly in man as the result of a
nervous shock. It is probable, as Mr. F. E. Beddard points
out in his interesting book on Animal Coloration (1892),
that the suddenness of the change robbed the experiment
of part of its value in proving that the cold is the stimulus
that induces the blanching. " The cold was administered
in a sudden dose, which may have produced an effect
analogous to a nervous shock."

In the case of the American hare, the investigations
of Welch (Proc. Zool. Soc., 1869) seem to show that the
process of assuming the white colour is twofold. On the
one hand, there is a new growth of white hair ; on the
other hand, there is a slow blanching of coloured hairs.

The whiteness of hair or feathers is due negatively to
the absence of the usual pigment, and positively to the
presence of minute gas bubbles in the cells. A new white
hair or feather is not in any special way difficult to under-
stand, it simply implies some slight change in the chemical
processes involved in all development. The pigment is
not formed or not completely formed, and gas vacuoles
are abundant in the cells. It seems, sometimes, as if the raw
material (or chromogen) of the pigment were present, but
the magic touch of the ferment required to make this a
coloured stuff is absent.

When a hair already coloured becomes white very
suddenly, there seems to be a rapid change in the pigment
material, which ceases to be coloured. It is well known

342 THE BIOLOGY OF THE SEASONS

that a very slight change of alkalinity or acidity will change
the colour of a flower, and that boiling water makes the
blue lobster red. But when a hair or feather becomes
white slowly, the change may be of a quite different kind.
For Metchnikoff has shown that the wandering amoeboid
cells — the phagocytes — of the body, which discharge so
many useful offices, pass into the hair and down again,
carrying a microscopic burden of pigment material.
Whether the change be quick or slow, there is an associated
physical change in the accumulation of gas vacuoles.
For the whiteness of grey hair is like the whiteness of foam.

When we remember that albinos often crop up as the
result of inborn variations in all sorts of animals, even
the blackest of them ; that albinism occurs in all possible
degrees of thoroughness ; that mammals periodically
moult their hair and birds their feathers — there seems no
particular difficulty in understanding how species may
have arisen with the constitutional idiosyncrasy of assuming
a white dress in winter, provided always that the change
can be shown to be distinctly advantageous.

There appear to be various advantages in a white dress
in very cold snowy regions. For a hot-blooded animal,
with a temperature high above that of the surrounding world,
the loss of heat is less with white hairs or white feathers
than with any other colour of dress. It is physiologically
the most comfortable dress, putting least strain on the
complex mechanism that regulates the body-temperature
in warm-blooded animals. This is probably the chief
advantage of turning white in winter, but it must also be
admitted that a white dress is the least conspicuous in
snowy regions as well as the most comfortable.

Where the struggle for existence is keen, it may be but
a little thing that turns the balance towards survival
or elimination. Professor Davenport had 300 chickens in

THE WHITE WINTER COAT 343

a field, 80 per cent, white or black and conspicuous, 20
per cent, spotted and inconspicuous. In a short time
twenty-four were killed by crows, but only one of the
killed was spotted. In this case the quality of whiteness
was disadvantageous, but in the North or among the
mountains those animals who turn white in winter are
likely to have their chances of life improved. This, at
least, is an outline of the selectionist interpretation of the
origin and significance of the white winter dress.

No better example of a victorious creature could be
given than the snowy owl (Nyctea scandica), a native of
the barren grounds of the " Far North/' that sometimes
visits us in very cold winters. It is a big bird, about two
feet in length, of white plumage with variable dark spots
and bars ; it has a strong and easy flight, and hunts by
day, picking up snow-birds like the ptarmigan, snow-
mammals like the Alpine hare, besides lemming and mice,
and even fishes. It has a wide distribution and a successful
life ; it seems indifferent to storms, except in so far as
they destroy its food ; it is wary but fearless, and a pair
of them will attack a man who comes near the nest among
the reindeer moss. The male is said to feed the mother
and her large brood. The harmony between the plumage
and the snowflakes is but one expression of the successful
balance that this great bird has struck between the in-
surgent claims of an imperious nature and the insouciance
of a merciless physical environment of the very hardest
type. " The cry, seldom heard, is wild and wailing," but
it is a cry of victory, for the bird has solved its problem and
is master of its fate. There seems a dim consciousness of
this in its fierce eyes.

THE SQUIRREL'S STORE

THE storing instinct is shown by diverse kinds of
animals at different levels of organisation. It
must have been evolved over and over again independently.
We think at once of ants, harvest-mice, beavers, even
moles — a few of the animals that store as the squirrel does.
Perhaps it is just a step or two in advance of the not un-
common habit of hiding or burying surplus food, but we
can readily understand how important it is in countries
where there is scarcity of food in Winter, and for animals
whose food keeps well, and which do not hibernate.

Storing is an autumnal industry on the squirrel's part.
Hazel-nuts, beech-nuts, and acorns are hidden in many
separate hoards, for the wisdom of not putting all the eggs
into one basket has been realised in practice at least. It
is interesting to notice that the young squirrels, which are
born about May, remain at home for a year, which is
perhaps another reason for storing.

It is difficult to say what a squirrel will not eat, — from
fruits to the eggs and young of wood-pigeons, from fir-cones
to sappy shoots, — but its characteristic food is the hazel-
nut. Holding the nut in its paws, the squirrel cuts a circle
so that the shell falls into two parts, often halves, and it
peels off all the brown skin before it begins to bite. Gilbert
White pointed out long ago that " there are three creatures,
the squirrel, the field-mouse, and the bird called the nut-
hatch, which live much on hazel-nuts ; and yet they open
them each in a different way. The first, after rasping off

344

THE SQUIRREL'S STORE 345

the small end, splits the shell in two with his long fore-teeth,
as a man does with his knife ; the second nibbles a hole
with his teeth, so regular as if drilled with a wimble, and
yet so small that one would wonder how the kernel can
be extracted through it ; while the last picks an irregular
ragged hole with his bill ; but as this artist has no paws to
hold the nut firm while he pierces it, like an adroit workman,
he fixes it, as it were, in a vice, in some cleft of a tree, or in
some crevice, when, standing over it, he perforates the
stubborn shell."

Those who have kept squirrels are in general agreement
as to their considerable attainments in the way of intelli-
gence. But we are probably mistaken if we credit them
with any forethought of the Winter. It is more likely that
the storing is instinctive. This is not contradicted by
the fact that in mild parts of the country squirrels some-
times omit to store. For it is well known that instinctive
activities often require particular stimuli to pull the trigger
which leads to their expression.

Another point of interest lies in the fact that the squirrel
is not much of a winter-sleeper. This makes the need for
storing more obvious. In very cold districts and severe
Winters the squirrel sleeps a good deal, but it usually lies
up only for a day or two at a time, and sometimes it does
not slumber at all. Thus in the storing device we see
simply one of the many ways of escaping from the grip of
Winter. Most of the birds fly away, the mountain hare
turns white as snow, the bats fall into deep sleep, most plants
pass into a resting stage, and so on — many other creatures
follow the squirrel's adaptation and lay up stores for the
evil days.

JETSAM

IN spite of many disappointments, there is always a
mild excitement in a walk along the shore — especially
after a storm. One never knows what one may discover
among the jetsam — the rubbish, as some people would say.
But this is to miscall the jetsam, for although there is some-
times an element of rubbish — the debris of civilisation —
the uninviting word is seldom appropriate in reference to
the whole. What we mostly find is the wreckage of life —
creatures that have been torn from their moorings, or that
have been forced by currents into the grip of the incoming
tide, or that have been battered to death and then swept
ashore. The jetsam differs greatly at different seasons
and in different localities, but it may be of interest to take
a representative sample.

The sand is sometimes mixed with dead or dying
Foraminifera (chalk-forming unicellular animals), such as
the beautiful Polystomella, which is like a microscopic
miniature of a Nautilus shell — an instance of that con-
vergence of architecture which we often find among un-
related forms at very different levels in the animal kingdom.
This Polystomella, which we can sometimes see as a white
speck on the freshly dislodged seaweed, is a good illustration
of the relative nature of simplicity. It is a single cell, — a
unit of living matter, — but it is structurally very complex
in comparison with a drop of white of egg. It has a spiral
chambered shell ; it occurs in two different types (like

males and females, though that does not seem to be the

346

JETSAM 347

meaning of the dimorphism), and it has an intricate life-
history.

Much higher in the scale of being are the sponges, such
as " Mermaids' Gloves," " Elephant Ears," " Crumb of
Bread," and the like, to give them their quaint but not
inappropriate popular names. They have been wrenched
away from their anchorage and tossed up on the beach.
We cannot look at them with irreverence, for the sponges
were the first animals to be successful in having a " body " ;
and, though they have no organs, they illustrate tissues in
the making. We try a piece against our skin, and discover
in its rasping effect why even large British forms are of no
use for toilet purposes. From a zoological point of view, it
is profitable to scrutinise a big sponge carefully, for there
are sometimes interesting creatures in its recesses. A
sponge is often a living thicket, in which small animals play
hide-and-seek.

Even more plant-like than the sponges are the zoo-
phytes, which we find so abundantly among the piled-up
seaweed or growing on it — colonies of polyps protected
within a firm tubular investment, often aborescent in their
mode of growth, and always fascinatingly beautiful.
There is something suggestive in the technical names of
the great types — Tubularians, Campanularians, Sertu-
larians, and Plumularians, or in the popular names like " sea-
fir." Very plant-like, indeed, most of them appear; but that
is again only a superficial resemblance of "convergence,"
as observation of the living creatures makes plain, for
they have mouths and food-canals, waving tentacles and
stinging lassos, and many of them bud off swimming-bells
or medusoids, which swim in the Summer seas like miniature
jelly-fishes.

Sometimes the whole of the flat beach is thickly strewn
with true jelly-fishes — a distinctive element in the Summer

34$ THE BIOLOGY OF THE SEASONS

jetsam. They consist in large proportion of " animated
sea-water," and it is instructive to watch them in all stages
of evaporation till only a thin transparent disc is left on the
sand. One remembers the striking fact that quite a number
of extinct genera have been described from their exact
impress on fine-grained rocks. Jelly-fishes are obviously
open-sea animals, and their abundant occurrence on the
shore illustrates wastage. They have lost their bearings
or got into the grip of inshore currents.

Sometimes tossed up together are two creatures which
are almost violently contrasted, though, as a matter of fact,
they are not very distantly related, namely, Dead Men's
Finger (A Icyonium) , a flabby, fleshy colony with no pretence
to elegance, and the Sea-Pen (Pennatula), a graceful plumose
colony with a central axis and the polyps arranged on
pinnules up each side, like the barbs of a feather.

There is sometimes a whole bank of the flexible tubes
of Lanice conchilega, a worm that binds shell fragments
and sand-particles together, literally " making ropes of
sand," and there is never difficulty in finding calcareous
worm-tubes, like those of Spirorbis, attached to the seaweed,
or those of Serpula on shells and stones. Now and again
among the seaweed we find the sea-mouse, Aphrodite, like
an entangled fragment of a rainbow, so iridescent is it.

Piled up in great quantities often are the fronds of the
sea-mat (Flustra), leaf -like or seaweed-like till the eye
catches the innumerable small holes tenanted by the
animals forming the colony. The biologist handles it
with some affection, for was it not the subject of Darwin's
first scientific paper? And those who enjoy "beauty-
feasts " cannot do better than give some time to the
numerous calcareous relatives of the sea-mat which form
exquisite growths on shells and stones. In illustration of
contrast between two types not very distantly related,

JETSAM 349

we may compare the gelatinous translucent Alcyonidium
gclatinosum and the lace-like Membranipora membranacca
spreading like a film on the large fronds of seaweed.

Among the transient components of the jetsam are the
delicate shells of the heart-urchin (Echinocardium) , which
we find with all the spines rubbed off and beautifully white.
The tread of a black-backed gull's foot is enough to break
them, and they soon pass into the common denominator
of the sand. The purple heart-urchin (Spatangus) is hardly
less brittle. It is interesting to find the strong common
sea-urchin (Echinus), with all its spines worn off and the
balls where their sockets fit on to the shell polished smooth.
The masticating mill or lantern which Aristotle saw more
than two thousand years ago has fallen out and lies by itself
on the sand — a puzzling structure to those who do not
know what it is, and equally puzzling to those who, knowing
what it is, inquire how it came to be. Allied to the sea-
urchins are the starfishes, which are often well represented
in the jetsam, sometimes occurring in the so-called " comet
form " — one arm in process of budding off the missing five.
For the regenerative capacity of these creatures is extra-
ordinarily great — a missing arm can be regrown and a
surviving arm can regrow all the rest.

As we search among the jetsam, crowds of " sand-
hoppers " spring high into the air, light again on the sand,
and are gone. Many of them are so like the sand in colour
that it is difficult to see them till they move, and then they
burrow with great rapidity. Some of them " feign death,"
as we say in our ignorance, when they are touched, and
will lie absolutely motionless for many minutes. Suddenly
the machinery begins to move again, they spring into
the air, and we see no more of them. These shore-
amphipods are interesting in many ways, but we cannot
do more than refer to the important part they play in

350 THE BIOLOGY OF THE SEASONS

the littoral economy by cleaning things up. They devour
everything that is edible in the dead bodies of animals,
both large and small, and make beautifully clean skeletons,
just as the ants do in the meadow. Along with these
genuine inhabitants of the shore there are representatives
of the same crustacean class in the jetsam. In the early
Summer especially we find many moults — from the glassy
husks of acorn-shells or barnacles to the substantial cast
shell of the edible crab.

On many beaches the most conspicuous component of the
jetsam is that furnished by molluscs, whose shells afford an
unstinted " beauty-feast." In shape and colour they are
singularly attractive, and they are full of unsolved problems.
Even to the simplest question, What is the chemistry of
their formation ? we can give no answer, though there are
reasons for suspecting that shell-making is an organised way
of using up waste-products.

In the regular lines patent on the surface of the shell,
and often accentuated by fine gradations of colour, we
have a fine instance of the periodicity of growth, and
doubtless also, if we knew enough, of punctuation from
without.

To get a good instance of the correlation of habit and
structure, we have only to lift a dog- whelk's shell and contrast
it with a periwinkle's. The former has a notch at the mouth
of the shell, in which, during life, there lies a breathing-tube
(or respiratory siphon) ; the former has no notch and no
siphon. And the interesting point is, that those with the
notch are almost invariably carnivorous and those without
the notch are vegetarian.

Many of the bivalves, such as the very common Venus
gallina, show a neatly bored hole up near the hinge, and
this explains their presence in the jetsam ! The hole was
bored by a carnivorous gastropod, which killed the bivalve

JETSAM 351

and devoured its body, leaving the empty shell to be
tossed up on the sand.

There are many curious items in the molluscan jetsam.
These chaffy balls that the wind blows along the sand
are the empty egg-capsules of the giant whelk or " roaring
buckie " — cradles which were the scene of a grim struggle
for existence between the first hatched larvae and those
that emerge later. These translucent " sea-pens " of
chitin and these " sepiostaires " of spongy lime which are
collected for cage-birds to peck at, are both the vestiges
of the vanished shells of squid and sepia. Sometimes a
whole fleet of cuttle-fishes gets into the grip of the tide and
is stranded on the flat beach, where they writhe their arms
impotently till the gulls give them their release.

Backboned animals do not contribute much to the
jetsam, but here and there we find a stranded fish, a bird
that has been killed, or a porpoise that has run aground.
Not very uncommon in some places is the body of an angler
or fishing-frog. This interesting fish often half buries
itself in the sand in relatively shallow water, and the lure
that dangles from the end of a long dorsal fin-ray seems
to attract little fishes to their destruction. A fresh speci-
men that has come too near the shore will afford an un-
forgettable instance of adaptation, for the numerous teeth
on the jaws that border the enormous gape are hinged at
their base, bending inwards at the least touch, so that
entrance to the mouth is as easy as exit is difficult.

A distinctive " common object of the seashore " is the
four-cornered " mermaid's purse/' with each corner drawn
out into a tendril. It is the egg-case of a skate or of a dog-
fish ; it is made of keratin or horn, just as our finger-nails
are ; its tendrils twine automatically around seaweed, so
that the laid egg is saved from being smothered in the mud,
and is rocked by the waves till the embryo is ready to be

352 THE BIOLOGY OF THE SEASONS

hatched. Then a chemical change in the white of egg
dissolves the horny shell along a line of weakness at one
end, and the young fish emerges. Those mermaids' purses
thrown up on the shore are usually emptied egg-shells, as
the opening at one end shows.

The birds among the jetsam are often of great interest —
even of biological interest . Thus the large number of young
guillemots and razorbills in Summer suggests the mortality
incident on the first plunge from the rocks. It is the first
step that costs, but in some cases the natural mortality is
artificially exaggerated by salmon-nets, in which many
marine birds get entangled and drowned. It is interesting
in another connection to find the stranded bodies of puffins
in the winter-time, when there is not a puffin to be seen on
any part of the coast for hundreds of miles. These bodies
have been washed in from the open sea, where many of our
Northern puffins seem to spend the winter months. And
he must be dull indeed who experiences no thrill in finding
among the seaweed on a winter day a rarity like the wedge-
tail petrel, a distinctively pelagic bird, killed perhaps by
flying against a ship, and probably washed in from a great
distance out to sea.

What a variety of biological impressions we gain from
this walk among the shore-jetsam. There is sometimes an
overmastering impression of the abundance of life. When
we see the stranded fleet of jelly-fishes, scores of squids in one
small bay, zoophytes to fill a sack with, a litter of sea-mats,
hundreds of fragile heart -urchins, and so forth, we return to
the old image that life is a stream that is always overflowing
its banks.

Nor can we walk along the shore looking at the jetsam
without being impressed with the variety of different kinds,
as well as with the uncountable number of individuals.
Even if we do nothing but gather shells (on a good shore for

JETSAM 353

them) we feel that we are in the presence of an overflowing
form-fountain, prodigal multiplicity, endless resources.

" But what an endlesse worke have I on hand
To count the sea's abundant progeny,
Whose fruitful seede farre passeth those on land,
And also those which wonne in th' azure sky.
How much more eath to tell the starres on hy,
Albe they endlesse seem in estimation,
Than to recount the sea's posterity,
So fertile be the floods in generation,
So huge their numbers and so numberlesse their nation."

Another impression is of the wastage of life — in regard
to which the physical forces are quite careless. There is
absolute insouciance in Nature. The beach is strewn with
jetsam as thickly as the woodland with withered leaves, but
it is a jetsam largely made up of corpses. There are, indeed,
empty shells tossed up, and the moults of crabs and various
items of this sort, but the great bulk of the jetsam consists
of corpses.

In contemplating the jetsam we see one aspect of the
struggle for existence, the non-competitive aspect — 4he
struggle between organisms and their physical environment,
between life and fate. What is thrown up on the shore
between tide-marks is only a small part of what is con-
tinually being dislodged by storms, and there can be no
doubt that there is a ceaseless thinning. It may be that
this sometimes leaves appreciably more room for those
creatures which are not thinned, and it may be that within
the members of a species those that vary in the direction
of resisting dislodgment survive in appreciably greater
numbers. But we have no data. It seems likely, indeed,
that in many cases there is no Natural Selection at all, for
that is a much narrower category than the Struggle for
Existence. From the absence of uniformity in the jetsam
in a tract of shore which we have studied for many years
we have a general impression that much of the elimination
23

354 THE BIOLOGY OF THE SEASONS

is quite indiscriminate, and therefore without direct import-
ance in evolution. It is very important to understand
clearly that the only eliminative processes that can be
regarded as counting for much in evolution are those
which are discriminate and consistent.

Another consideration of some interest is brought home
to us when we watch the jetsam being covered up by the
sand either borne in by the tide or blown by the wind. We
see how the first step towards fossilisation might be taken
when some change in currents piles up a heavy sandbank
near the high-tide mark, burying a sample of the jetsam.
But even if the sample was a good one, and if all should be
preserved in a future sandstone, the result would be far
from a fit representation of the local fauna of our times. It
would be almost as misleading to judge of the civilisation of
the early twentieth century by the debris washed up on the
beach near a large town. Nor should one fail to notice that
even if a whole stretch of jetsam were quickly buried, many
items would have no chance of being preserved or of being
well preserved, for the Amphipods and Bacteria and other
scavengering creatures have already begun their destructive
work. The sea's memoranda are apt to pass quickly beyond
all hope of deciphering.

We cannot watch the jetsam through several consecutive
days without getting vivid illustrations of the circulation
of matter. The squid is scarcely dead before the gulls are
pecking at it, and even land birds like rooks come down to
the feast. The Amphipods already referred to are con-
tinually doing with their microscopic nibbling what birds do
when they pick a dead fish clean. We lift up the substantial
shell of an oyster or of a " roaring buckie " and find it
riddled with holes, neatly bored as if with a gimlet, — the
work of a boring sponge Cliona, which thus helps the shell
a long way towards its incorporation with the sand. It is an

JETSAM 355

interesting occupation for a leisure hour to sit with a lens
in hand sifting the sand — distinguishing here a fragment
of shell and there a piece of a sea-urchin's spine, here a
remnant of an acorn-shell's rampart and there a Fora-
minifer. One can arrange a series of grades of fineness, like
different samples of sugar ; they are stages in the process
of reduction towards that lowest common denominator
which we call the sand of the seashore.

OLD AGE AND DEATH

ALL around us, if we will, we may see living creatures
growing from the apparent simplicity of germs to
the obvious complexity of adult organisation. But from
their earliest hours they are singled and sifted. Out of
a million oyster-embryos energetically swimming in the
sea, it may be that only one reaches maturity, and even
then it may be that it has only survived to become what
Huxley playfully called " a gustatory flash of summer
lightning." In all ordinary cases, however, throughout
the animal kingdom there is abundant survival, and those
who escape the dangers of the first part of the Mirza
bridge form a strong contingent. As we watch them we
see that they wax stronger, attain a stable constitution,
adjust themselves masterfully to their environment, and
give rise to others like themselves. From almost every
point of view the curve of their life rises, and they are
full of promise. We see life victorious and triumphant.

But as we continue to watch, we begin sooner or later
to detect a rift within the lute. We begin to detect
symptoms of decadence. Vigour slackens, the range of
activities narrows, the thrusts of adverse circumstances
or of intrusive disease are less successfully parried, the
organisms drift instead of swimming in the environmental
current, they lose their grip on their surroundings which
seem to close in upon them, they sometimes show internal
symptoms of weakening and atrophy — in a word, they
%row old.

OLD AGE AND DEATH 357

Our problem is to try to understand more clearly why
it is that the curve of life, after attaining what the thought-
ful biologist Treviranus called a vita maxima, should
begin to droop, sinking quickly or very slowly to a nadir
of vita minima, at the threshold of death. Why do
living creatures grow old, or, to be more accurate, why do
many living creatures grow old ?

As this is a very difficult problem — not admitting as
yet of complete solution — we must work round about
it, instead of venturing on a direct attack. By patiently
approaching it from different sides, we may reach in the
end some greater clearness. Shakespeare had the problem
before him when he wrote : " And so, from hour to hour,
we ripe and ripe, And then, from hour to hour, we rot and
rot, And thereby hangs a tale." But the tale is not as yet
coherent.

One of the interesting results of modern Biology is
expressed in the somewhat startling phrase, which we
owe to Professor Weismann — the immortality of the Proto-
zoa. This implies that the simplest animals (and plants
too for that matter) — the unicellular organisms — are not
subject to natural death in the same degree as higher
forms are. It seems that many of them, at least, are
practically immortal. They may be devoured, they may
be crushed, they may be killed in a hundred ways ; some
are liable to fatal infection from microbes ; but of their
natural death there is no definite proof.

In the open sea there are countless millions of uni-
cellular organisms — both plants and animals — Foramini-
fera, Radiolaria, Diatoms, Desmids, and so forth — which
are continually being killed by vicissitudes of temperature
and the like. Dying, they sink slowly down, like a cease-
less, gentle snow-shower, it may be through miles of water,
to form no inconsiderable part of the food-supply of the

358 THE BIOLOGY OF THE SEASONS

animals who people that dark, cold, silent, eternally calm
world which we call abyssal. But so far as we know, these
sinking atomies have all been killed ; they are subject to
violent or environmental death, but not to natural death.

It may be noted, in passing, that many of the Protozoa
are but little troubled by bacterial or microbic infection,
which is so fatal to higher forms. Metchnikoff has shown
that Amoebae, for instance, are able to engulf and digest
various kinds of very virulent microbes, just as the wander-
ing amoeboid cells or phagocytes of higher animals (and
our own indispensable bodyguard) are able to do. To
certain minute parasites, however, even the Amoebae
succumb.

How is it, then, that these simple pioneer organisms
escape natural death ? The presumably true answer is
twofold : that being relatively very simple, — in a sense
without a body, — they are able to sustain with persistent
success the vital equation between waste and repair ;
and that their common mode of multiplying (by dividing
into two or more units) is inexpensive and not attended
with any loss of life. On the one hand, we reach the idea
that death was " the price paid for a body " ; on the other
hand, we see that in the simplest forms of life immortality
has not yet been pawned for love.

In many living creatures the giving origin to new lives
is the beginning of death. The annual plant dies as its
seeds are scattered. Many a worm, many an insect, never
survives the climax in which it gives origin to others like
itself. ' ' Quasi cursores lampada t radunt , ' ' and as the torch
is handed on to another, the runner falls and dies. Even
among backboned animals, cases are known, e.g. of
lampreys and eels, in which the parents collapse and die
after reproduction. The little fish Aphia pellucida is like
an annual among plants, it lasts only for a year. Repro-

OLD AGE AND DEATH 359

duction is exhausting and often fatal. But this does not
apply to the Protozoa.

Among unicellular organisms the process of multiplica-
tion is simple and inexpensive, and correspondingly rapid.
One becomes two by dividing, and we cannot speak of
death when there is nothing left to bury. A little one soon
becomes a thousand. From one Infusorian there may be
a million in four days.

It seems, however, that there is, in some cases at least,
a limit to the number of successive divisions that can occur
in an isolated family of Infusorians all descended from one,
and in the absence of that pairing of unrelated forms
which normally occurs in natural conditions. After a
certain number of generations — which can be extended by
using stimulants, such as strychnin — senile decay sets in,
the new members are born old, they are dwarfish and de-
generate ; soon they cease to be able to feed or divide.
Even at this low level of organisation it is only through the
fire of love that the phoenix of the species can renew its
youth. Without conjugation of unrelated forms the family
comes to an end.

Now it may be that this limitation to the number of
successive cell-divisions has a deep significance in regard
to the growth of higher animals, which is, of course, accom-
plished by successive cell-divisions. Here, too, there are
limits to multiplication and renewal. In brains, notably,
the cells stop dividing or multiplying at a very early date —
it may be before birth ! Thus we see the force of Professor
Weismann's sentence : " The real cause of death is to
be looked for, not in the using up of the body-cells, but
rather in the limits to the reproductive power of cells."

What has been said throws light upon the problem
of senescence in the higher forms of life. It is to be re-
garded not simply as an intrinsic necessity ; it is incident

360 THE BIOLOGY OF THE SEASONS

on the complexity of the bodily machinery, on the accumu-
lation of arrears in the process of repair, on the limits
which are set to the multiplication or renewal of cells, and
also on the occurrence of organically expensive modes
of reproduction.

The general idea is that the wear and tear is not quite
counteracted by food and rest. The recuperation is often
incomplete, and there is an accumulation of physiological
arrears. The organism gets quickly or slowly into debt.
The items may be infinitesimal, and in many animals a
violent death comes before their accumulation begins to
tell. In other cases they mount up and lead to that physio-
logical insolvency which we call senescence and death.

The case of the worker hive-bee illumines the whole
subject. In our childhood many of us — who are constitu-
tionally fond of laziness — used to be urged to consider " the
little busy bee" which "improves each shining hour," but
a more intimate and critical knowledge of bees and their
behaviour has entirely shaken our confidence in this exem-
plar of our childhood. Let us lift only one corner of the
seamy side, by asking how the shining hour improves the
busy bee. When we ask this question we find that the
worker hive-bee grows old with extraordinary rapidity, and
often dies a few weeks after its industry begins. It grows
old while it is still young, a victim to over-exertion. With
all its getting, it gets not wisdom, but foolishness, for its
brain-cells go steadily and surely out of gear. A large
number pass into a state of irrecoverable fatigue- collapse.
As Professor Hodge says : " The nerve cells, in the course
of the bee's daily work, gradually cease to be functional,
and die off, until no more are left than are sufficient
for the necessary vital functions." Thus the premature
growing old of the bee is a warning against over-industry.

We have sketched what may be called the general

OLD AGE AND DEATH 361

wear-and-tear theory of senescence, but many more detailed
suggestions have been brought forward. From a large
series of measurements, on the growth of guinea-pigs in
particular, Professor C. S. Minot of Harvard reached the
conclusion that the rate of increase in weight (measured
in percentage of total weight) steadily falls from the earliest
days after birth. Whereas the first ten per cent, of addition
in weight is made in about two days, the twenty-fifth
addition of ten per cent, (absolutely much greater) requires
nearly eighty-eight days. In fact, growth illustrates the
law of diminishing return. It is an uphill business all
the time, but the hill gets steeper and steeper as we go up,
until at length the gradient becomes impracticable and
growth stops.

Minot compares the business of growing to the building
of a wall by one man : " The wall is built and grows larger,
develops, but the man grows more and more tired, and as he
grows more fatigued, and as the wall becomes higher, the
progress thereon becomes slower and slower, but the wall
has developed all the time. So we see that the body
develops all the time, but the power to continue the develop-
ment of the body steadily diminishes." Professor Minot
maintains that the law holds true of man, of chickens, of
rabbits, of dogs, of ferrets, and of some other animals.

We cannot follow Professor Minot when he goes on to
say that there is from earliest youth onwards " a gradual
loss of vitality." We do not know — no one knows — what
vitality precisely means, but it surely means more than the
rate of growth in weight. It may be that in some domesti-
cated animals, such as sheep, cattle, and poultry, there is a
decrease in the range of vital activities and interests after
adolescence is past, and it may be that the two-year-old
child lives a more strenuous day than a man of sixty ; but
these are exceptional cases, When we consider how much

362 THE BIOLOGY OF THE SEASONS

else a typical wild animal does with its income besides
growing in size and weight, we find it difficult to believe
in the " gradual loss of vitality " which seems to Professor
Minot to be a general phenomenon of life.

Minot has sought to establish a second corollary of his
law, — that as the body grows older there is an increas-
ing disproportion between the cell-substance (cytoplasm)
and the nucleus (nucleoplasm) . He believes that the
cytoplasm increases out of proportion to the nucleoplasm,
and thus interferes with the power of growth. It is inter-
esting to find that Minot's views as to the importance of
the relation between nucleus and cell-substance, which
were first stated in 1890, have found of recent years con-
siderable confirmation. Professor Richard Hertwig of
Munich has brought forward a large number of very in-
teresting facts showing the importance of the relation
between nucleus and cytoplasm, and has given an elaborate
discussion of the whole subject.

Somewhat analogous to Minot's view is that of Kasso-
witz, who points out that as life goes on there is more and
more accumulation of what one may call half-used sub-
stances, such as fat, the body becoming, as it were, smothered
in the results of incomplete combustion.

Demange, the author of a French treatise on old age,
seems to interpret all the phenomena in terms of the
degenerative changes in the walls of the arteries. These
show hardening or sclerosis, the nutrition of surrounding
cells is thereby lessened, and atrophy sets in. As is often
said, " A man is just as old as his arteries." There can be no
doubt as to the importance of this view, but we wish to
know why the arterial wall should become sclerotic. More-
over, the theory is far too human in its reference ; many old
animals show no trace of arterial sclerosis.

According to Metchnikoff, the symptoms of old age

OLD AGE AND DEATH 363

may be for the most part summed up in the conception of
atrophy — or insufficient nutrition. This defective nutrition
is the prelude to an internal conflict in which the wandering
amoeboid cells or phagocytes, and one kind in particular,
which he calls macrophagous, attack the nobler tissues which
are no longer vigorous, which have ceased to produce pro-
tective substances, which have been poisoned, or which
have been overloaded.

We must also notice the suggestion that the setting-in
of old age is due to local exhaustion of certain parts of the
bodily machinery with which few of us are familiar — the
organs of internal secretion — such as the thyroid gland.
These normally furnish to the blood some more or less
obscure specific substances without which vigour cannot
be sustained, or antitoxin substances, for instance, which
enable the body to resist poisons, including those of its own
formation. It should be remembered that even an innocent
substance like sugar may act as a poison. This view has
led to the suggestion of various modern elixirs of life —
from injections of common salt upwards — intended to re-
place the deficiency due to local breakdown. None of the
elixirs has as yet proved itself markedly efficacious, nor has
any good reason been given why organs of internal secretion
should be exhausted sooner than many other organs.

After considering these and other suggestions as to the
immediate causes of old age, we feel bound to conclude
that in spite of their importance in furnishing descriptive
details of the familiar process, they do not throw much
light on its necessity. The law of the conservation of
energy makes us aware that, defiant as the organism is,
arrears are likely to accumulate in the activity of a com-
plex system, but the immortality of the Protozoa shows
that this dynamic bankruptcy is not inevitable. We know
that a carefully constructed inanimate engine may outlive

364 THE BIOLOGY OF THE SEASONS

three generations of the animate engines who controlled
it, and we know that of two organisms, apparently equal in
complexity, one may be old in twelve months, and another
may be still young in twelve years. It is easy to speak of
accumulated debts, of diminished trophic activity of nerves,
of hampering superfluity of half-used products and of
diminishing activity of internal secretion, of the struggle of
parts within the organism and of the limitations to pro-
longed cell-divisions ; but why should it be so at all, and
why should the results be so different in different cases ?

We are not surprised, therefore, to find a specialist on
senility (Dr. W. H. Allchin) declaring : " We do not
know why the body, after it has reached a state of maturity
and vigour, should gradually decline ; why, when once an
even balance between tissue-waste and restitution is estab-
lished, it is not maintained indefinitely." It is easy to
understand why individual human beings with poor
inheritance, unnatural environment, and vicious habits
should exhibit senile involution and die ; it is often difficult
to understand how they manage to live so long ! but these
abnormal, though frequent, cases do not touch the bio-
logical problem of normal senescence. All the signs of
human senility may be seen in a patient under twenty years
of age ; but this sad fact hardly touches the general problem
of normal senescence — which is so elusive.

As we think over such facts as we have hinted at, the
suspicion grows strong that we are apt to miss biological
truth by being too anthropocentric. Man is in many ways
a very artificial organism — he is super-organic. He has
an external heritage not less important than that embodied
in his germ-plasm ; he has often a self-made environment
not less important than that which he was born into ; he
has peculiar functions and habits — both for good and ill —
which are all his own ; and there is good reason for sup-

OLD AGE AND DEATH 365

posing that the impression of old age which we get from the
majority of our aged fellow-beings is very different from
what we should have inferred from an impartial survey of
animal life.

Perhaps we may recognise three grades : —

a. In many human beings, in not a few domesticated
animals, e.g. horse, dog, cat, and in some semi-domesticated
animals, notably bees, and possibly in some wild animals,
the close of life is marked by senility. The organism is no
longer in full possession of its faculties ; more than that,
some function or other — notably that of the nervous and
sensory systems — has gone out of gear. Intelligence has
waned, instincts have ceased to ring true, unified control is
lost, the senses are dimmed and dulled, even locomotion
becomes impossible, the life is reduced to an existence —
an existence which could not be prolonged except under
artificial conditions comparable to those of an incubator for
premature infants.

b. In a minority of civilised human beings, in some
domesticated animals, and in a few wild animals, the
decline of life is marked by senescence. Growth has long
since stopped, and decrease in weight and stature has been
going on ; there is a general shrinkage, of brain and spinal
cord, of spleen, lymphatic glands, and kidneys ; the gonads
have ceased to be active; there is narrowing or even
obliteration of capillaries ; the bones become thinner,
weaker, and of course lighter ; and the corresponding
functions are slackened in each case in adjustment to the
weakening of the bodily engine. A slight shrinkage of
articular cartilages, a slight weakening of dorsal muscles,
brings about the normal stoop. A slight atrophy brings
about the normal grey hairs — which in this category may
be a crown of glory.

c. For many animals it must be said that they reach

366 THE BIOLOGY OF THE SEASONS

the length of their life's tether without any trace of either
senility or senescence. They pass their climacteric of
vigour, it may be ; they may be old in years, but certainly
not in structure ; they pass off the scene — with a violent
shove — victims to violent death. It is impossible to tell
whether the vital energies were or were not really impaired,
but we know that in many fishes and reptiles, for instance,
which have lived long, and have in the end died violently,
there is not in their organs or tissues the least hint of senile
involution or even of senescence.

In a special category must be ranked the immortal
simple animals which never grow old, which disappear
directly into other individualities like themselves ; of which
enough has already been said.

Let us now see if we can make further progress towards
clearness by proceeding on a quite different tack, by
considering the great variety there is in the duration of
life. This has often been made the subject of popular
remark and of quite fanciful popular estimate. Weis-
mann quotes from Jacob Grimm an old German saying :
" A wren lives three years, a dog three times as long as a
wren, a horse three times as long as a dog, and a man three
times as long as a horse — that is, eighty-one years. A
donkey attains three times the age of a man, a wild goose
three times that of a donkey, a crow three times that of
a wild goose, a deer three times that of a crow, and an
oak three times the age of a deer." It need hardly be
said that most of these figures are quite fictitious, e.g. the
estimate of the deer's duration of life at six thousand, and
the oak's at twenty thousand. By counting the wood rings
in some of the great Californian trees an age of two thousand
years and more has been estimated, but some say that
more than one double ring of wood is sometimes formed in
one year.

OLD AGE AND DEATH 367

In one of his celebrated essays Weismann has sought
to show that it is impossible to find the key to the great
differences in the ages of animals by any simple reference
to size, or to complexity, or to rate of growth, or to rate
of life. " The strength of the spring which drives the
wheel of life does not solely depend upon the size of the
wheel itself, or upon the material of which it is made,"
or upon its rate of movement. The duration of life has
been, in part at least, punctuated from without and in
reference to large issues ; it has been gradually regulated
in adaptation to the welfare of the species.

It is true that large animals usually live long, and that
small animals are often short-lived : an elephant may
live two hundred years, a horse forty, a blackbird eighteen,
a mouse six, and many insects only a few weeks or days.
But then a cat or a toad may live as long as a horse
(forty), a pike or a carp as long as an elephant (two
hundred), a crayfish as long as a pig (twenty), and the
sea-anemone " Grannie," which died a natural death in
Edinburgh on 4th August 1887, was at least sixty-six years
old.

Flourens hazarded the generalisation that the length
of life was always five times the period of growth ; but
the horse, for instance, matures in four years, and may
live to be forty or more.

On general grounds, already hinted at, we might sup-
pose that very active animals wear themselves out quickly,
while sluggish creatures live long. Instances of trees
living for a millennium rise at once in the mind ; on the
other hand, the male ants live only for a few weeks, while
the queen-ant may live for thirteen years, and the workers
for several years. Birds are exceedingly active animals,
but some of them have a long life ; there are cases of
ravens, falcons, eagles, vultures, living half more than

368 THE BIOLOGY OF THE SEASONS

a century — in captivity, of course, which would lessen their
expenditure of energy.

The clergy have longer lives than other professional
men, but most of them live a very active life. St. Antony
did not mix much in practical affairs and died at one
hundred and five ; Titian was all his life about a court,
and painted a fine picture at ninety-six.

Perhaps the most astounding fact in regard to human
length of life is that brought out in such statistical researches
as those of Tarchanow, that throughout the world from
equator to poles the duration of life remains on the average
the same. This is an astounding fact when we consider
the diversity of race, of diet, of occupations, and of sur-
roundings. There are short-lived and long-lived families,
for longevity is hereditary ; there are life-sparing and
deathful occupations and habits ; there are pleasant and
unwholesome surroundings ; yet the average duration of
life for different peoples and countries is about the same.
This makes us feel that the punctuation of the length of
life, which is so diverse among individuals, is, as regards
the species, referable to much wider issues than the im-
mediate surroundings, diet, habits, or rate of life. We
see no alternative to the conclusion that the clock of
human life has been regulated in the course of the ages
in reference to the wide issues which we sum up in the
conception " the welfare of the species."

We have expounded a general reason why higher
organisms must grow old : the perfect self-repairing
capacity of the unicellulars is no longer possible when
the bodily mechanism is very complex and when repro-
duction is physiologically expensive. But this natural
interpretation of senescence fails to suggest why a dozen
different kinds of animals of about the same size and
complexity, and with similar modes of reproduction, should

OLD AGE AND DEATH 369

grow old at very different times. An attempt to explain
the diversity of longevity by reference to the immediate
conditions of life also fails. We have to face the fact that
while the rate at which the wheels go round is doubtless
very important for individual cases, it cannot be the key
to an understanding of the diversity in the average dura-
tion of life in more or less similar species. Many sluggish
animals, such as molluscs, are short-lived ; many active
animals, such as birds, are long-lived. Nor can we find
the solution in considering the diverse environments, diets,
industries, and so on. We are thus prepared for the next
step in the argument.

Weismann's theory is that in the course of time, after
many experiments, so to speak, the length of life in a species
has been regulated in reference to the rate of multiplication
and the average mortality. The punctuation is from
without, not from within ; it is Natural Selection that has
determined — and that slowly, after grave consideration
as it were — where the stops come in : the semicolon of
maturity, the colon of senescence, and the full stop of
natural death. In other words, the internal constitutional
arrangements which secure that an elephant can survive
for two hundred years and a freshwater sponge for less
than a year, have been gradually wrought out or regulated
in relation to the welfare of the species.

Let us take a concrete case : the golden eagle, weighing
9 to 12 lb., is intermediate as regards weight between hare
and fox ; all three are very active ; all three are very
complex. But while the hare lives ten years, and the fox
fourteen, the golden eagle lives sixty. Weismann says
that this has been in the course of time regulated in refer-
ence to various big facts of life, e.g. that the two mammals
are more fertile than the bird, that there is less mortality
among the young mammals than among the young birds,
24

370 THE BIOLOGY OF THE SEASONS

that the young mammals are sooner able to look after
themselves, and so on. If the golden eagle matures at
about ten years, and lays two eggs a year, " then a pair will
produce one hundred eggs in fifty years, and of these only
two will develop into adult birds ; and thus on an average a
pair of eagles will only succeed in bringing a pair of young
to maturity once in fifty years." For this reason, golden
eagles have a high degree of longevity.

Before we pass to the striking contrast between man
and animals as regards growing old, let us consider for a
little some of the human signs of old age. What are the
signs of normal senescence ?

According to one line of interpretation at least, we have
one of the sublimest pictures of senility in Ecclesiastes xii.
The mind and senses begin to be darkened, the winter of
life approaches with its clouds and storms ; the arms —
the protectors of the bodily house — tremble, the strong
legs bow, the grinders cease because they are few, the
apples of the eyes are darkened, the jaws munch with only
a dull sound, the old man is nervously weak and startled
even by a bird chirping, he is afraid of even hillocks, his
falling hair is white as the strewn almond blossoms, he
drags himself along with difficulty, he has no more appetite,
he seeks only for his home of rest, which he finds when the
silver cord is loosed or the golden bowl broken.

Let us take a more modern expression. Professor
Humphrey had direct or indirect knowledge of the state
of the body in five hundred men and women of eighty years
of age and upwards, when, in a famous lecture, he summed up
as follows : —

" In the normal ' descending ' development the relative
proportions of the several structures and organs are pre-
served, while weight, force, and activity are being lowered
by a gradual and well adjusted diminution of material and

OLD AGE AND DEATH 371

nutritive activity. During the time that the bones are
becoming lighter and less capable of offering resistance,
the muscles become, in like proportion, lighter and weaker,
and with a narrowing range of action ; and the associated
volitional and other nerve-apparatus exhibits a correspond-
ing lowering of energy and force. . . . The weakening
of the heart and the diminished elasticity of the arteries
provide a proportionately feebler blood-current ; and a
lower digestive power and a lessened appetite provide a
smaller supply of fuel, enough to feed, but not enough to
choke the slowing fires. ... It is upon the well ordered,
proportionately or development ally regulated, decline in
the several organs that the stages which succeed to maturity
are safely passed, and that crown of physical glory — a
healthy old age — is attained.

" A time comes at length when, in the course of the
descending developmental processes, the several parts of
the machine, slowly and much, though equally, weakened,
fail to answer to one another's call, which is also weakened,
when the nervous, the circulatory, and the respiratory
organs have not force enough to keep one another going.
Then the wheels stop rather than are stopped, and a develop-
mental or physiological death terminates the developmental
or physiological decay. . . . Yet, strange and paradoxical
as it may seem, this gradual natural decay and death, with
the physiological processes which bring them about, do not
appear to present themselves in the ordinary economy of
nature, but to be dependent upon the sheltering influences
of civilisation for the opportunity to manifest themselves,
and to continue their work."

Professor Humphrey's summing up may be taken as
an authoritative statement of the average state of affairs
in human old age, and it is in no way affected by the in-
teresting exceptions that we all know. Thus, for instance,

372 THE BIOLOGY OF THE SEASONS

Montaigne says of his father : "I have seene him, when
hee was past threescore years of age, mocke at all our
sports, and out-countenance our youthfull pastimes, with
a heavy furr'd gowne about him leap into his saddle ; to
make the pommada round about a table upon his thumb ;
and seldome to ascend any stakes without skipping three
or foure steps at once." We have known a venerable
naturalist of seventy-five make the ascent of Schiehallion,
and walk eight miles besides, without a trace of ill effects.
Similar examples are familiar to all, and they represent the
ideal, doubtless quite attainable, defiance of senility.
They illustrate the contrast between senility and senescence.

Senescence is the normal process of growing old, as we
see it in constitutionally strong men who have lived very
healthful lives (within or without civilisation), and in those
wild animals that live to a great age in natural conditions.
Senility is the process of marked degeneration, which is
often seen in old age (and sometimes long before it). And
the biological fact which seems to us of most importance
is the striking one that man and his domesticated animals
have almost a monopoly of senility, while wild animals
rarely show any trace of it.

It may be said that most wild animals die a violent
death in the majority of cases before they exhibit even
senescence. But some live to a great age, and the im-
portant fact is the practical absence of senile degeneracy,
except in relatively unimportant parts, such as the teeth.
Apart from captive carp and the like, which must be dis-
counted, fishes that have demonstrably lived for a great
many years (as the rings on their scales, bones, and ear-
stones show) do not exhibit any trace of senile degeneration.
Dr. F. Werner, an expert student of reptiles, emphasises
the fact that even in giant specimens of crocodile and snake
" no trace of senile degeneration could be detected."

OLD AGE AND DEATH 373

In concrete illustration of old age phenomena, let us
take Metchnikoff s account of the hair turning grey in man,
and his account of the state of a very old captive parrot.
Turning grey can hardly be called more than a pheno-
mena of senescence ; the parrot showed senility, so that
the two cases do not quite illustrate the contrast that
usually obtains between man and beast in old age.

In almost all animals, from sponges to mammals, there
is, within or apart from the vascular fluids, a bodyguard of
wandering amoeboid cells, technically called phagocytes.
It is well known that they perform many functions both
in health and in disease : they form a bodyguard, struggling
with invading microbes, surrounding and engulfing irritant
particles, transporting useful material, helping to repair
wounds, aiding in the regeneration of lost parts, and in
metamorphosis, and so on. To the pathologist, " phago-
cytosis5' has become a word of comfort, and perhaps there
has been some exaggeration of its importance. But no one
can deny that the phagocytes play an important and
versatile part in the vital economy.

If we hold a hair against a strong light we see at once a
distinction between a lighter central portion — the medulla,
and a darker peripheral portion — the cortex. Both
parts are built up of cells, but the medullary part is the
more living of the two. Metchnikoff discovered that
the disappearance of pigment from hair beginning to
turn grey is due to the intervention of phagocytes. These
amoeboid cells appear in the medullary part of the hair
and make their way out into the cortex, where they absorb
the pigment granules, which they then remove from the
hair. In a hair beginning to turn white, there are many
phagocytes laden with pigment — especially about the root
of the hair. In absolutely white hair — the colour of which
;s due to gas bubbles — there are no phagocytes with

374 THE BIOLOGY OF THE SEASONS

pigment or only a few. " It is thus indubitable," Metchnikoff
says, " that the phagocytes of the hairs swallow up the
granular pigment of the cortical layer and transfer it
elsewhere, the result being the complete whitening of such
hair." This interesting discovery brings the whitening of
the hair into line with other processes in which phagocytes
play an important part. If it should be insisted that
even here there is senile atrophy, we are quite willing to
yield the point — the contrast would remain, however it
is phrased, between relatively trivial and superficial changes
in old age and others which imply the thoroughgoing
degeneration of important structures.

Something more serious than an absorption of decora-
tive pigment was revealed in MetchnikofFs study of an
aged parrot. It is known that these big-brained birds
often live to a great age ; for, although we may not accept
Humboldt's famous story of an aged parrot that spoke the
at uric language of a tribe of American- Indians for years
after there was any human survivor able to understand it,
we have to recognise the validity of other records showing
that parrots may outlive their long-lived owners and exceed
even fourscore years. It was a veteran, belonging to the
species Chrysotis amazonica, of which Metchnikoff made
a careful post-mortem, with the assistance of Mesnil
and Weinberg, and she must have been over eighty when
she died. During her declining years the captive was
feeble and senile ; but the striking fact was that a thorough
investigation of the tissues revealed little, except along
one (very important) line, that could be called degenerative
or deathful.

The post-mortem report on the aged parrot informs
us that the liver was slightly fatty, but showed no
hint of cirrhosis or any other disease ; the kidneys
were tending towards fatty degeneration, but showed

OLD AGE AND DEATH 375

no sclerosis or hardening ; the muscles and the heart
were quite normal, and so on. It goes without saying
that we must not generalise on one parrot, and very few
aged parrots have been scientifically utilised; but the
fact is quite clear — that this octogenarian was very sound
in most of its organs. It would have passed even a strict
Insurance Examiner on all points save one, and that
happened to be detected because the scientific eye was
predisposed to see.

Only in the fore-brain was there anything very note-
worthy— its nerve-cells were in many places surrounded
with nerve-devouring phagocytes. These " neuronophagous
cells " are well known in the brains of patients suffering
from certain neurotic diseases and from persistent intoxica-
tion ; they are also frequent in the brains of old men and
old mammals, but the authors never saw a case so marked
as that of this aged parrot. There seemed to be " an
intense phagocytosis" — the brain was being literally "de-
voured " by the " neuronophages." The noblest elements
of the organisation were falling victim to cells of the most
primitive type — comparable to the immortal amoebae.
Here we have a most interesting case of senility — and yet,
only local cerebral senility — in a captive creature. It is a
supplement to what we have already noticed in connection
with the brains of bees.

After this illustration, intended to bring out the contrast
between normal senescence with relatively trivial changes
and senility with marked degeneration or involution of
important structures, we venture to submit four theses, —
that few wild animals of great age show any senile degenera-
tion ; that few wild animals of great age show more than
signs of general senescence ; that many very old men show
no signs of senility, but only of senescence ; and that, as all
the so-called signs of human senility may be found illus-

376 THE BIOLOGY OF THE SEASONS

trated in young men under twenty, we may regard senile
degeneration as an unnecessary incident of old age !

Let us face the question : Why should wild animals
show so little trace of senility, which is often marked in
domesticated or captive animals ? why should they rarely
exhibit more than a slight senescence, while man often
exhibits a bathos of senility ?

In reference to the contrast between wild animals and
those tamed or in captivity, we have to remember that the
former seem usually to die a violent death before or after
old age has set in, but almost always before there has been
time for senility. From such violent death man more or
less protects the pet horses, dogs, cats, etc., whose life has
become entwined in his affections. Furthermore, while
natural death is due to the accumulation of physiological
bad debts, the character of the old age depends upon the
nature of these bad debts. Some are much more unnatural
than others ; they are much more unnatural in tame than
in wild animals.

As to man, in particular, let us recall a few facts which
may explain why he is unhappily notorious as the best
illustration of senility, (a) Being sheltered by Reason
from most of the extreme physical forms of the struggle for
existence, he can live for a long time with a very defective
hereditary constitution, which may end in a period of
undesirable senility, (b) Endowed as he is with Reason —
the capacity for handling general ideas and regulating his
conduct in reference thereto — man, especially in highly
civilised communities, is very deficient in the resting
instinct, and seldom takes much thought about resting
habits. A simple creature exhausts its stores of internal
fuel, the nervous system gives the signal " Hunger " or
" Fatigue," and infallibly the simple creature will eat or
rest if it can. Its brain is not disobedient. In higher

OLD AGE AND DEATH 377

animals, however, and especially in man, the matter is
much more complicated. The signals for stoking or resting
are plainly given, but some higher nerve-centre counter-
mands them. We disregard the moral of the worker-
bee's life, (c) The artificiality and injuriousness of many
human activities and environments must necessarily affect
the character of the physiological bad debts which lead on to
natural death. The death is inevitable ; but just as there is
more than one kind of bankruptcy, so there are different
forms of old age. Everything depends upon the nature of
the bad debts. We may have an old age such as Cicero
praised, or one whose days are labour and sorrow. As there
is no power of regeneration in the nervous system — for,
except in very rare cases of injury, we never get any new
nerve-cells after we are born — and as it is especially the
wearing out of the nervous system which makes the down-
grade of life often ugly, and as it is pre-eminently by rest
and change and a quiet mind that the nervous system is
kept young, we come again to the old commonplace, " Let
us be aisy ; and if we can't be aisy, let us be as aisy as we
can." (d) In contrasting man and the animals, we have
also, of course, to remember that in many cases there has
come about in human societies a system of protective
agencies which allow the old to survive through a period of
prolonged senility. We cannot do otherwise in regard to
those we love ; but it is plain that our better ambition would
be to raise the standard of our vitality so that, if we have an
old age, it may not be more than senescent.

After writing these hard sayings, we were relieved to
read what Dr. Humphrey said in 1885 : " Through the
growth of this germ (of sympathy) it was given to man to
introduce a new factor into the economy of Nature, and by
forethought, by mutual co-operation, and by care for
others, which are the very essence, at any rate the very best

378 THE BIOLOGY OF THE SEASONS

feature, of civilisation, to prolong life when by this very
forethought and sympathy life had become more valuable,
and when the prolongation of it had consequently become
more desirable ; and scope was thus afforded for the
carrying out of these descending or senile developmental
processes which must have been nearly dormant in the
earlier periods of human existence." "It is not to be
expected that this good seed should be without a blending
with tares ; and the scope thus given for the fuller
development of the physiological processes gave scope
also for the development of the pathological processes,
and enabled the various diseases to spring up and take
their course, afflicting not man only, but those animals
also which come under his fostering or protecting
influence."

" It may therefore be said that the prolongation of life
into and through the periods of decay, and into and through
the processes of disease — indeed almost, if not quite, the
very existence of decay and disease — are the result of
human forethought and sympathy. In other words, decay
and disease are, by civilisation, substituted for quick and
early death." This is a forcible and authoritative
statement, which leads us to doubt whether the humane
policy, which makes so much of the individual, is not
in some respects prejudicial to the best interests of the
race.

What have we to suggest ? Certainly no elixir vitae,
but a humdrum, common-sense prescription, the common
property of the oldest and the newest physicians, which
does, however, gain some added force from the biological
facts that have been submitted. Closer touch with Nature,
more open air, more change of environment, more versatility
of function, more effort to secure the lines of activity that
are organically most suitable and, therefore, most effective,

OLD AGE AND DEATH 379

less artificial stimulation, less " pressing," as golfers say,
stricter avoidance of nerve-fatigue, more resolute cultiva-
tion of resting-habits, an effort to heighten the standard
of vitality rather than an effort to prolong existence — such
are some of the conditions of remaining young.1

1 I have to thank the editor and proprietors of The London Quarterly
Review for kindly allowing me to utilise in the foregoing study an article
on " Growing Old " which I contributed several years ago.

INDEX

Abundance of life, 242, 352.

Acquired characters, 209.

Adolescence, 211.

Agassiz, 261.

Age of animals, 366.

Agricultural industries of ants, 131.

Aitken, John, 229.

Alcock, 3.

Allchin, Dr., 364.

Allen, E. J., 8.

Animal heat, 335.

Animals, temperature of, 336.

Ants, play of, 226.

Aristotle, 120, 181.

Astronomical division of year, 4.

Autumn, 239.

Avebury, Lord, 119.

Balder, 312.

Baldwin, Mark, 212.

Barrington, Hon. Daines, 145.

Bates, 3,

Beddard, F. E., 341.

Bees, 360.

Beetles, 208.

Belt, 3.

Birds, courtship of, 135; develop-
ment of, 179 ; eggs of, 170 ; of
passage, 73 ; return of, 68.

Brehm, 65.

Brine-shrimps, 203.

Brooding, 328.

Brooks, W. K., 294.

Bruce, W. S., 70.

Buchan, Dr., 122.

Buckle, 199.
Buds, unpacking of, 66.
Bugnion, Prof. E., 133.
Bullen, G. E., 8.

Calandrucci, 42.

Calderwood, W. L., 299.

Camerano, 205.

Cat and mouse, 225.

Caterpillars, 51, 206.

Chambers, Robert, 62.

Chapman, F., 79.

Chlorophyll, 252.

Clarke, Eagle, 82.

Clarke, H. L., 95, 97.

Cock of the Rock, 227.

Cold, influence of, 205.

Cold-blooded animals, 333.

Cold-coma, 317.

Colour of leaves, 252.

Colour change, 341.

Correlation between externalperiod

icity and internal changes, 9.
Courtship of birds, 135.
Cunningham, J. T., 206.
Curves of life, 10.

Darwin, 3, 62, 147, 257, 275, 278,

282.

Davenport, 342.
Death, 319, 357.
Delage, Prof. Yves, 43.
Demeter, 20.
Differentiation, 213.
Dixon, C., 287.

381

INDEX

Dornroschen, 23.
Duration of life, 366.
Dust, 229.

Earthworms, 281.
Edwards, Jonathan, 257.
Eel-fare, 41.
Eggs of birds, 170.
Elimination, 321, 322.
Elliot, Scott, 3.
Emotions, 222.
Engrams, 14.

Environment, animate, 207.
Ephemerides, 233.
External periodicities, 4.
Extinction of types, 321.

Fall of leaf, 250.

Fatigue, 360.

Fischel, 6.

Fishing by animals, 129.

Flat fish, 206.

Flight, contrast between Spring

and Autumn, 81.
Flowers, 93, 112.
Forel, A., 337.

Galapagos Islands, 121.

Games, 228.

Gaskell, 5.

Gatke, 69, 75, 76, 77, 295.

Germination, 61.

Gesner, 3.

Gill, Dr. Theodore, 43.

Gnats, life-history of, 27.

Goeldi, Dr. Emil, 128.

Gossamer, 243, 255.

Grassi, 42.

Green, Prof. J. Reynolds, 64.

Grey hair, 373.

Grilse, 301.

Groos, Prof., 154, 214, 218.

Growth, 212.

Hacker, Prof. V., 151.
Hamerton, 224.

Harvey, 181*

Heat, influence of, 205.

Hering, Prof., 5.

Hertwig, Prof., 362.

Hibernation, 315, 332.

Hickson, Prof., 3, 261.

Hilton, 328.

Hodge, Prof., 360.

Hornbill, nest of, 162.

Huber, 226.

Hudson, 3, 223.

Humble-bees, life-story of, 86;

inter-relations with other living

creatures, 89.
Humboldt, 3.
Humphrey, Prof., 370.
Huxley, 12, 197.

Ice ages, 289, 313, 320.

" Immortality " of the Protozoa,

357-

Instinctive activities, 125.
Integration, 213.
Intelligent activities, 125.

Jacobi, 42, f.
Jacobson, Edward, 122.
Jetsam, 346.
Juan Fernandez, 121.

Kearton, 219.

Kerner von Marilaun, 120.

Kirby, W. E., 54.

Klebs, experiments on Algae, 60.

Kofoid, 8.

Kropotkin, 65, 120.

Lemmings, 287.
Leptocephalus, 43.
Light, influence of, 206.
Lingula, 199.

Living and not living, 325.
Living creature and its surround-
ings, ii.
Loeb, 206.
Lyonnet, 51.

INDEX

383

Macgillivray, Prof., 163, 340.

M'Cook, H. C., 131, 257.

M'Intosh, Prof., 262.

Mallock, P. D., 301.

Mammals in winter, 332.

Maupas, 205.

Mayer, A. G., 262.

Mayflies, 233.

Meijere, de, 122.

Metabolism, 5.

Metchnikoff, 342, 358, 373.

Miall, Prof., 257.

Migration, 69, 244, 285.

Millson, A., 283.

Minot, C. S., 212, 361.

Minute organisms, multiplication

of, 26.

Mneme, Semon's theory of, 14.
Modifications, 208 ; denned, 209 ;

indirect importance of, 209.
Moggridge, 131.
Moleschott, 204.
Monkeys, play of, 224.
Morgan, Prof. Lloyd, 125, 147,

169, 210.
Moseley, 3.

Mosquitoes and ants, 122.
Mould growing among termites,

132.

Movements of animals, 222.
Mutation, 291.

Natural selection, 320, 353.

Naturalist travellers, 3.

Nature and nurture, 12.

Nectar production, 114.

Neger, F. W., 132.

Nelson, E. W., 140.

Nervous system, 329.

Nests, natural history of, 157 ;

specific nature of, 164, 165 ;

series of, 159.
Newton, Prof . Alfred, 149, 160, 170,

298.

Northern animals, 338.
Nutrition and reproduction, 7.

Old Age, 356.
Oliphant, James, 216.
Organic diversity, 30.
Organic inertia, 30.
Osborn, H. F., 210.
Ovenbirds, 163.

Pain, 330.

Pallas, 3.

Palolo, 261.

Periodic growth, 6, 7. "

Petersen, 42.

Pfeffer, Prof., 60.

Phagocytes, 342, 375.

Plant-life, rhythms in, 60.

Plasticity of young things, 29 ; of

life, 196.
Plateau, 119.
Play, 154, 214, 218.
Poulton, 58, 206.
Preferential mating, 144.
Procession caterpillars, 53.
Protective coloration, 342.
Protopterus, 9.
Pycraft, W. P., 158, 162, 168, 292.

Rational activity, 126.
Reawakenings, 86.
Recapitulation theory, 30.
Reflex actions, 124.
Rest, 249, 323.
Rhythms in plant life, 60.
Rod way, 3.
Romanes, 223.
Ruskin, 105, 113.

Sacculina, 207.
St. Kilda, 219.
Salmon, 299, 304.
Salmon ladder, 305.
Sand of the shore, 355.
Sanders, Miss, 58.
Schiller, 220.
Schmankewitsch, 203.
Schmidt, Dr. J., 42.
Schwalbe, Prof., 340.

3^4

INDEX

Sea-shore, 346.

Sea swift, edible nest of, 164.

Seebohm, 292.

Seeds, 318.

Seed-scattering, 241, 274.

Selection, sexual and natural, 145.

Semon, 9, 14.

Semper, Prof., 22, 333, 336.

Senescence, 365.

Senility, 365.

Sense of direction, 298.

Sequoia, n.

Sex, 215.

Sex dimorphism, 136.

Sharp, Dr. David, 87.

Shepherding among animals, 130.

Sleeping Beauty, 312.

Snowy owl, 343.

Song of birds, 149.

Sorby, H. C., 175.

Spencer, 154, 220.

Spiders, 255.

Spring flowers, 93.

Squirrel, 344.

Stahl, Prof., 252.

Storing, 247, 344.

Strasburger, 277.

Struggle for existence, 353.

Summer, Biology of, 103.

„ Flowers, 112.

„ Industries, 123.

Tadpoles, 32, 207.
Tailor ant, 133.
Tegetmeier, 81.

Thienemann, Dr., on migration
routes, 78.

Thompson, D'Arcy W., 173.
Thorndike, 195.
Tower, Prof., 208.
Treviranus, 357.

Variational stimuli, 209.
Variations, 214, 221.
Verworn, 5.
Vestiges of Creation, 62.
Vines, Prof., 64, 116, 117.
Vital rhythms, 5.
Voracity of caterpillars, 55.

Wallace, A. R., 3, 57, 83, 121, 145,
154, 158, 160, 167, 200, 280, 291,
292, 293.

Warm-blooded animals, 335.

" Water-babies," 26.

Water plants, multiplication of
minute, 67.

Web of life, 161, 218, 260.

Weismann, 146, 182, 357, 367.

Whelk, capsules of, 29.

Whirlpool, living matter as a, 12.

White, Gilbert, 3, 255, 281, 344.

White colour, 339.

Whitman, 328.

Winter, 311.

Witchell, 152.

Withering leaves, 242, 250.

Yarrell, 80.
Young things, 26.
Youthfulness, note of, in spring, 26
Yung, Prof. E., 39, 202.

Zacharias, 67.

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