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FE.

\L LI

A SWARM OF MAY-FLIES

From ‘ Riverside Natural History’

By permission of Messrs. Houghton, Mifflin & Co., Boston, U.S.A.

Zool

G
ANIMAL LIFE '

BY

E, WisGAMBLE. DSc. FLR.S.

EDITOR OF
‘A JUNIOR COURSE OF PRACTICAL ZOOLOGY’

WITH 63 ILLUSTRATIONS

LONDON
SMITH, ELDER, & CO., 15 WATERLOO PLACE, S.W.
1908

All rights reserved

PREPACE

THE want of a small work dealing with the adaptations
and factors of animal life in a broad and connected
manner is my excuse for writing this book. In the
simplest form and with the least amount of descriptive
structural detail that I can compass, I have attempted
to describe the moving spectacle: its abundance and
variety, its modes of maintenance and of development,
the safeguards of its individual and racial welfare.
The evolutionary standpoint is adopted throughout,
and in developing the subject I have proceeded by
the use of three leading motives that differentiate
animals. from plants—movement, the acquisition of
solid food, and the nervous control of response to
changing order. To have included the factors of
animal evolution, so far as they are known, would
have unduly swollen the volume, and partly on that
account, partly also because of such excellent recent
accounts as those by J. A. Thomson (‘ Heredity,’
Progressive Sci. Series: Murray) and by R. H. Lock
(‘ Heredity, Variation, and Evolution’: Murray), I
have omitted consideration of them.

vill ANIMAL LIFE

The work is written in the first instance for those
who wish to learn or teach such a survey of the animal
pageant as can ally itself with observation and experi-
ment ; and in the second place for those who wish to
organise their knowledge of animal life. References
to fuller treatment of many topics are given at the
close of the chapters.

I am indebted to Mr. Gordon Hewitt for the loan
of the two figures illustrating the house-fly and for
revising the proofs; to the Director and staff of the
Manchester Museum and to Mr. Greenwood for aid
in obtaining the half-tone photographs ; and to the
publishers and authors specified under the respective
illustrations. Miss Emily Dust (Manchester School of
Art) has executed the design for the cover. My textual
indebtedness to the work of others cannot be clearly
indicated, but I may mention that the chapter of
insect life-histories owes much to the writings of Fabre,
Peckham, Miall, and Wasmann, and that the latter
part of the chapter on colour (especially as regards
‘ effacing gradation ’) owes much to the writings of the
American artist Thayer.

F. W. GAMBLE,

MANCHESTER UNIVERSITY:
March 12, 1908,

ONTENTS

CHAPTER I

THE INTEREST OF ANIMAL LIFE
- : PAGE
The contrast between animal and plant life—The value of
the study of animal life. , ‘ : : , , ; I

CHAPTER II

THE ‘FULNESS OF THE EARTH

Its appeal to hunting and pastoral races—The discovery of
animals—The richness of the sea—The sea as the mother
of life—The abundance of life as revealed by travellers
and naturalists—Examples of the prevalence of animal
life—Scale insects—Green-fly—The hidden life of winter—
Animals as rock-formers . ; ; : . ‘ i . 7

CHAPTER III

THE ORGANISATION OF ANIMAL LIFE

Individuality—Classification into groups subordinate to
groups—The classes of vertebrate and invertebrate
animals—Evolution of animal life—The rise of fish,
amphibia, reptiles, and mammals—The three main pro-
blems of animal life—The maintenance of self—The
development of self—The progress of the race. . s "SG

>

eo)

ANIMAL LIFE

CHAPTER IV
MOVEMENT

. The Ae of movement .
. Increasing finish of movement is s accompanied by
siovadticih in the scale of being—Insects—Fish
2. The finish and unweariedness of movement
3. Its highest manifestation—The migration of animals
The modes of animal motion—The analogy of a boat—
Leverage in swimming, walking, and flight—Other forms of
locomotion .

. The movements of antinalenies=Citiacy movement—The

value of cilia—Movement essentially innate
1. The movement of worms and crustacea .
2. Swimming, walking, and flight of insects .

. The locomotion of vertebrates :

1. Fish—Their methods of swimming—The use of the
tail and fins—Free swimming and ground es
at walking and flight ‘

2. Movement on land— Support “and: propulsioa==
Movement and rest in an erect position—The changes
which have converted aquatic locomotor organs into ter-
restrial ones.

3. Amphibia and Reptiles—Mammals—Running, climb-
ing and aquatic mammals—Whales and seals—Flying
mammals—Bats

4. Birds—Their flight—Adaptation of the body—
Wings—Feathers—Methods of gliding and active flight—
Their adaptation for perching, running, and swimming—
The structure of the legs and feet

CHAPTER V
THE QUEST FOR FOOD

A. ges: source of animal food : the quest for plants :

. The need for food—Dependence of animal on plant
life—The feeding of fixed animals—The value of agit
plants to animals—Windfalls—Leaf mould.

2. The feeding of crustacea and insects—Their jaws,
lips, and tongues—The services of insects to plants .

PAGE

43

48

50

65

68

CONTENTS |

3. The methods of snails and slugs—The sees of
plants against their attacks :

4. Vegetarian mammals—The need for thorough mas-
tication °

5. Fruit-eating birds ‘

6. Evolution of plants sccoinpanied by ackensed com-
plexity of animal life that depends upon them

B. The quest for prey : the supply of food in the sea:

1. The origin of the carnivorous diet—Scarcity of plant
life in the open sea—At the poles and in deserts—Fixed
animals not consistent vegetarians—Hydroids, Meduse,
and anemones are carnivorous—The food of star-fish

2. The demands of active swimming life—The food of
fish—Pre-occupation of the mouth with breathing—
Rarity of grinders—Choice of shrimp and oily food—
The food of ground fish—Dab—John Dory—Dog-fish

3. Cuttle-fish—Their activity and mode of overcoming
prey—tTheir enemy the sperm-whale .

4. The food of sea-birds

C. The quest for prey : adaptations of land anitiiats :

1. The stress of land life—Land plants abundant but
protected against the attacks of animals—The chief
causes that favour a carnivorous diet . ‘

2. The food of carnivora—Voracious indeets—-Spider
and their allies—How the web is made

CHAPTER VI

THE BREATH OF LIFE

Life as a combustion—The need for oxygen—Our unconscious- »

ness of daily waste and <n meats of the
metaphor of flame

The relative abundance of oxypen in water ‘aad air at différent
depths—Evolution following the quest for oxygen

Modes of breathing among animals—Protozoa, fixed animals,
sponges, corals ; the irrigation of. their bodies with water,
and the power of pigment in combining with oxygen
—tThe respiration in higher animals is carried out by an
internal fluid, the blood, which is aerated in the skin cover-
ing the gills—The adaptation to secure thorough aeration
(shells), and greater oxygen-holding capacity of the blood,

78

87

89

99

103

xii ANIMAL LIFE

PAGE
blood pigments—The respiration of free-living and burrow-

ing crustacea ; of bivalve and univalve molluscs ; of cuttle-
fish—Air-breathing worms, crabs, and molluscs—The
respiration of fish; their gills and muscle-pigments—
Adaptations to avoid the suffocating influences of drought
on fish-life—The air-bladder and its gases; its varying
uses, leading to the formation of lungs—The respiration of
amphibia and the conquest of the land—The breathing of
reptiles—The evolution of more perfect lungs in birds and
mammals associated with the development of the voice and
of a higher organisation—The maintenance of the heat
produced by breathing and the production of a constant
temperature ER Ce er

CHAPTER VII
THE SENSES OF ANIMALS

The orderliness of animal organisation implies controlled
adaptation—The nervous system a visible sign of this
harmonic grace—It mediates between the stimuli that fall
upon an animal and the resulting responses—It is the
seat of traditional and individual memory, and sets going
periodic as well as immediate actions—The nature of
periodic nervous action—Organic memory—The light it
throws on animal development—The nervous system the
earliest and most important organ to appear—The influence
of glands in stimulating the development of the body . 127

The senses considered as the necessary means of maintaining
a station in life, gaining food, and avoiding danger—These
senses bound up with essential adjustments to meet the
exigencies of life—The contrast between the few essential
sensations common to all living things and the vast array of
organised form in which they find expression—The habits
of a shrimp or prawn taken as an example of the way in
which the conduct of these animals is built up out of
responses to light, pressure, taste . ; “ ° ‘ :

The double nature of stimuli that affect animals—Stimuli
from without that affect the skin, and others, from within,
that affect the internal organs—The correlation between
the two effected by the nervous system—The skin as the
seat of origin of sense-organs for interpreting external con-

133

CONTENTS

ditions—The origin of the eye and ear from the skin—The
origin of the central nervous system in the skin—The origin
of the nerves in (a) a primitive connection between the
central system and muscle ; and (0) an equally primitive con-
nection between the internal movements and the governing
central system ; and (c) a correlation between (a) and (0) .
The stiffening of these inward and outward responses into habit
and tradition—The evolution of more complex responses
based upon a groundwork of muscular and sensitive re-
sponse—The greater strenuousness of life on land and in
air has led to the evolution of complex instincts—The
power of profiting by experience—The domestication of
animals, and its far-reaching effects on man’s social life

CHAPTER VIII

THE COLOURS OF ANIMALS

1. The primary meanings of animal colours:

Colours the outcome of inward processes—The relation
of animal pigments to light—Exposed surfaces of the
body more deeply coloured than shaded ones—Experi-
mental evidence on the colouring action of light—The
bleaching effect of darkness—Agreement between plant
foliage and animals in colour distribution—The green
pigment of plants concerned in nourishment—The red pig-
ment of blood and muscle a respiratory substance, and only
secondarily a decorative one—The relation between the
two in chemical composition—Loss of green pigment in
parasitic plants; temporary loss in minute flagellate
organisms when supplied with organic food, reacquire-
ment of the green colour under inorganic nourishment—
Nature of these Flagellata: a connecting-link between
animals and plants—The adoption of solid food and the
origin of muscle gave the animal branch of this family
greater facilities for distribution and involved more efficient
oxidation—Evolution of the blood pigments

The evolution of red and yellow fatty pigments — Wide
distribution of these in animals and plants—Association of
these pigments with stores of reserve food—Association
of fat with these pigments in the skin and other tissues
of the Aisop prawn—Evidence for the formation of this

Xili
PAGE

140

144

149

xiv ANIMAL LIFE

fat independently of the food—The original mode of
nutrition in animals a double one (a) by photosynthesis ;
(b) by elaboration of solid organic food—The fatty pig-
ments in animals are a vestige of the first mechanism
which has been supplanted by the second and more
efficient one—Pigments arising through elimination of
waste substances from the tissues and their deposition in
the skin—The white colour of butterflies, Summary :
pigments originally nutritive or respiratory ; excretory
pigments a by-product of vital activity—The original
function may be lost and a decorative meaning and use
gained secondarily
2. The secondary meanings of animal celouss

Harmony between animals and their surroundings the
note of animal life—Sympathetic colouration a case of
such harmonious adaptation—Instances of colour-sym-
pathy ; the sop prawn—The development of colour-
sympathy in the life of the prawn—Critical period in its
career—The abundance of similar sympathetic colouration
in other marine animals—Scarcity of such in fresh-water
—Colour sympathy in land-animals—Arctic and desert
colouration—Forest and field renderings of background
and foliage on the skins of animals—Effacive gradation
in the shading of the skin—Cryptic colouring, form, and
posture amongst stick-caterpillars, moths, and butterflies
—The leaf-butterfly and Mantis of India—Spiders—
Mimetic resemblance of certain unrelated butterflies—
Seasonal differences of colouration and habit—Protective
meaning of cryptic colouring—Experiments on cater-
pillars and mantises—Warning colouring associated with
distastefulness—The pigments of animals older than the
effect they produce . eS Ys

CHAPTER IX

THE WELFARE OF THE RACE

Racial welfare a stimulus to which all beings respond—Personal
acquisitions of racial value—The heritage of animals and of
man—The response of animals to the stimulus of racial
welfare—The stringency of the test by which the value
of this response is measured—The ornaments of sex

PAGE

160

167

CONTENTS

among mating animals—Battles to ensure the healthiest
mating among spiders, fish, birds, and mammals—Testing
of the powers in drones of the bee and males of other
insects—Unequal severity of the test for survival among
young males in contrast to the young females of many
animals

Eggs and young—Mipratiin—The sea aS a “nursery—Phee
advantages of pelagic larval life—Modes of defending the
eggs and young of aquatic animals by fixing them to some
holdfast and by the guardianship of the parents—The nests
and nurses of fish—The protection of the eggs by frogs and
reptiles—The secretiveness of birds and insects in their
choice of nesting sites—Brief review of the nests of birds—
Small birds construct the most carefully woven nests—The
significance of the relation between size and incubating
heat—The varied methods employed by insects—The
elaboration of nurseries by social insects ‘ ,

CHAPTER X

THE LIFE-HISTORIES OF INSECTS

The influence of climate in stimulating the development of
insect life—The cyclic changes of its abundance—The
insects of early spring—Selection of nesting sites—Differ-
ences between families of great and of lesser antiquity in the
food of the young

The life-histories of primitive iaseou this epiangtails aad their
allies—The straight-winged insects—Grasshoppers, locusts
—The difficulty of shedding the old skin—The development
a gradual one—The life-history of the pa
and their larve . . ;

More complex life- shistories—Metamerphosis—The ‘introduc-
tion of the pupal stage—Caddis-flies and caddis-larve—
The development of the pupal stage and the emergence of
the fly—Beetles—The life-history of the oil-beetle ..

The life-histories of more modern insects—Butterflies and
their adaptations to aerial life—The development of the
cabbage-white butterfly — Complex structural changes
during the pupal stage—The Diptera or two-winged flies—
Their economic importance—The mosquito and midge

XV

PAGE

190

201

217

222

234

xvi ANIMAL LIFE

PAGE

family—The life-history of the common gnat—The breath-
ing pores of the larva and of the active pupa—The emer-
gence of the fly—The development of the mosquito and its
relation to malarial fever—The life-history of the harlequin-
fly (Chivonomus)—Its larva the ‘ bloodworm ’—Variation
in its colour related to the nature of the water—The
phantom-larva of Corethra—The life-history of Midges : the ~
owl-midge (Cevatopogon)—The black-fly (Simulium)—The
adaptations of its larva and pupa to life in running water—
The drone-fly (Eristalis)—Adaptations to larval life in stag-
nant water—General conclusions on the life-histories of
Diptera : : : ‘ ‘ ‘ : ‘ - 240
The Hymenoptera:
Efficiency of their care for their youig=-Conipiaiey of
their communal life—The less highly organised families of
this order—The saw-flies, gall-flies and ichneumons—The
nature of gallsand their mode of origin—The two generations
of gall-flies—The solitary wasps—The key-hole wasp—The
nest and its stores of food—The sand wasp (A mmophila)—
Mode of construction of its nest—Mode of capturing prey
and storing the nest—The social wasps—Their nests and
workers—Solitary bees—Prosopis a primitive type—The
burrowing and carder bees—Cuckoo bees . ‘ 263
Evolution of the hive-bee—The first indications of
association in burrowing bees—The first attempts at comb-
construction—The appearance of workers at first casual in
Halictus, becoming a settled habit in bumble-bees—The
construction and ventilation of bumble nests foreshadowing
the perfect comb of the honey bee—The importance of good
seasons in assisting the evolution of the higher bees—
Behaviour of Arctic and Mediterranean bumble-bees—The
tropical Meliponas—The high degree of perfection attained
in the colonies of the hive-bee. ; 284
The nests of ants—The care of ants for their younie— The
swarming of ants—Longevity of ant-queens—Foundation
of an ant-colony—Conditions that produce queens, drones,
or workers—Aberration of the nursing instinct . : - 204

LIST OF ILLUSTRATIONS

FIGURE PAGE
A SWARM OF MAY-FLIES . : A . . Frontisptece
1. EGGs oF THE SguIpD (Loligo) . ; A ; ‘ <a II
2. SHOAL OF JELLY-FISH . : ; : ; : ‘ . 13
3. COMMON BROWN LIZARD . : 5 ‘ : ae 18
4. THE SLOW-worRM (Anguts farsa yic : : : ; 18
5. NEwTs ‘ : ; A : F : ; sed
6. THE RELATION BETWEEN CENTIPEDES AND Insects SO
7. SWALLOW ON THE WING . : F : . ‘ nym Wee
8. GREATER HORSESHOE Bat en as , : . . ee poke
9. WHITE SEAL ; $ : ; j ; P P 54
10. DISSECTION OF BIRD (P1cEon) : : : ; : % ~§9
31. SAND-HOPPER (Gammarus) ‘ F : ; : ae 68
12. TUBE-BUILDING SAND-HOPPERS : : : , & “GD
13. GRouP OF BURYING BEETLES , ‘ : : ss gr zo
14. ORCHESELLA: A PRIMITIVE INSECT . ee ‘ ely
15. MUSSELS AND PEA-CRABS . : ‘ : “a> BE
16. How A STAR-FISH OPENS AND EATS AN OYSTER? . o 18g
17. BLACK-HEADED GULL, NEST AND YOUNG . : : 86
; 18. TONGUE OF HOUSE-FLY . , : i! ans : - igs
‘ 19. WHEEL-WEB OF GARDEN SPIDER . . . . .. 3
20. WEB OF Agelena ON GRASS ; ‘ : ; : .* 508
21. NEST OF YOUNG Agelena ON FURZE . ; é pa: 00
22. NEST OF CAVE SPIDER - ‘ P ‘ é : y) GF
23. BRINE-SHRIMP (Branchipus) . : : ; ; iy TOS
24. DAPHNIA, THE WATER FLEA... ‘ ‘ - EI
25. HEAD AND THORAX OF CRAYFISH, SHOWING GILLS . . II2
26. A Group OF SAND-BURROWING ANIMALS (HEART-
URCHIN, LUGWoORM, COCKLE, MUD-CLAM, AND MASKED
CRAB) . ; : ; ‘ ‘ : ; ; ‘ oo
27. THE DORMOUSE . a ae ee ee a er ee 124

xVill ANIMAL LIFE

FIGURE

28.
29.

. Lire-History oF CABBAGE-WHITE BUTTERFLY
. THE HovusE-FLy ; s ; :

. LARVA OF GNAT

. PupaA OF GNAT . ; ; P

. NEstT OF COMMON WASP _. ; 4

. BuRROW OF LEAF-CUTTER BEE .
. Burrow OF SOLITARY BEE (Andrena)
. NEst OF BUMBLE BEE . =

Tue Cave Newt (Proteus anguineus) ; 3 ta
THe DEVELOPMENT OF CoLOUR-PATTERN IN Hippolyte .
FEMALE ORANGE-TIP BUTTERFLY, SHOWING SYMPA-

THETIC COLOURATION : ‘ H f : 5 F

. HEN PARTRIDGE AND YOUNG ; : ape:
. CocK ARGUS PHEASANT DISPLAYING HIS Puouier E
. THe Rurr in MATING PLUMAGE . ; - ; ‘=
. Brack CocK DISPLAYING BEFORE THE GREY-HEN. "i
. TRANSFORMATION OF A SEA-WoRM (Nereis) . If
. THE PALOLO-WORM OF SAMOA . F f H .

. Eacs OF HERRING . - : r :

. Eocs oF CUTTLE-FISH (Sepia) ; ee ; ‘

SAND-MARTIN AND YOUNG ; F : : : Z

. SWALLOow, NEST AND YOUNG . ; 3 : r
. Nest oF LITTLE TERN . ¢ : ; : 3

NEST OF SKYLARK i . :

. Nest oF LONG-TAILED TIT-MOUSE. .

. Cuckoo In NEsT OF TITLARK . ; : ‘

. HarveEst-MOUSE AND NEST . 3 : ,

. SOME PRIMITIVE INSECTS . ~ : - ‘

. THE DEVELOPMENT OF THE GRASSHOPPER . -
. Lire-HIstorRY OF THE DRAGON-FLY ; ‘ :

SKIPJACK BEETLES AND LARVA (WIREWORM) . ;

LEAF-CUTTER BEE . : : P
EVOLUTION OF THE Torta) oF BEES . ‘

. ADAPTIVE STRUCTURES OF THE LEGS OF THE HIVE-

BEE . ‘ ~ . “
HIND-LEGS OF SOLITARY BEES .

. . . . . .
. . . . .

WORKER-CELLS FROM BEE-COMB ‘

PAGE
152
172

179
182
194
195
196
200
202
203
204
207
208
209
211
213
214
215
223
225
229
239
243
247
250
251
277
278
280

281
282
283
284
287
295

ANIMAL ~ LIBRE

CHAPTER I

THE INTEREST OF ANIMAL LIFE

THE contrast in impressiveness between plant life and
animal life is a reflection that every countryside
arouses. By the plants we may know the wetness or
dryness of a district, its cultivation or wildness, the
run of the watercourses, the season of the year, and
even the time of day. In civilised countries, where
the scenery has been largely determined by man, the
national character finds expression, and shows in our
own country a generous capacity for half measures,
a toleration of opposites, a compromise between
formality and freedom, and controls in a _ charac-
teristic manner the growth of native plants and the
cultivation of alien ones.

With the fields and heaths, the woodlands and
uplands, in all their varying expressions, genera-
tions of countryfolk have had close alliance. Be-
tween them and this ‘furniture of the earth’ there
has grown a tie, the strength of which is not realised

B

2 ANIMAL LIFE

until it is broken, and the Devonshire combe or West-
morland fell are images in exile.

To this the animal life of a countryside offers a
sharp contrast. Its bulk, in a bird’s-eye view, is in-
significant, its tenure of the ground is short. It is
evasive, and offers no large characters distinctive of
the highlands and lowlands, or of the cultivated and
open country. It is remote, and for the discovery of
its genius a closer attention and a minuter acquaint-
ance than the farmer’s or gamekeeper’s is requisite.
Its individuality is never wholly subdued by the
country around it or the breeder who cultivates it.
Alone among animals the horse and dog have been
trained to a willing understanding of man’s wishes.

Mass, stationariness, and pliability—the notes of
plant life—are replaced in animals by purposeful
evasion, activity, and intractability. The abundance
of animals, far from always giving the pleasure
wakened by the advent, growth, and even the decay
of rich masses of plant life, raises feelings of dis-
gust and alarm as often as those of satisfaction or
enjoyment. The evolutions of shoals of fish, the
concerted flight of birds, the winding homeward of a
herd of cattle, give but an evanescent sense of beauty
in comparison with the intimate sense of relief aroused
by the sight of a woodland after traversing stretches
of bare country. The sense of animal intractability is
enhanced when we discover in them no merely passive

feature of the scene, but independent and even hostile
beings.

INTEREST OF ANIMAL LIFE 3

A slight acquaintance, however, with the enthralling
mysteries of animal behaviour awakens the latent
sympathy between animals and ourselves that is
one mark of our community of origin. Many of us
begin that acquaintance through the sheer pleasure
we find in observing and collecting animals, and in
watching their habits. To such field-work the most
experienced naturalist returns with increasing wonder
at the infinite significance of what he sees, at the
unexpected number of fresh problems that lie in every
shell and feather, in each insignificant worm or insect,
in the colours of organisms, in the very games of chil-
dren, and even in social customs. The shell brings
up in his mind the image of an organism with brain,
muscles, and glands woven into a fabric that has no
Caprice in its most delicate folds, whose care for itself
and its offspring implies ceaseless evasion of fish and
shrimp and cunning defence against the destructive
power of the waves. The feather, with its perfect
system of hooks and eyes, by which its plumes form
a firm, airtight membrane for flight or for retaining
warmth, is another casual object of beauty and sig-
nificance. The meaning of its colours, its position
on the bird’s body, its replacement at the moult-
ing time, are but the first of many problems that
a feather suggests. The worm remains no longer a
degraded creature or one remote from human interest,
for the study of worms has suggested the most
effective of modern treatments of that most terrible

of skin diseases—lupus. It was by the behaviour of
B2

4 ANIMAL LIFE

earthworms under the influence of. special rays of
light that the treatment known by Finsen’s name
owes its origin.

Finsen noticed that when the prismatic colours
of sunlight are successively cast on the worm, the
blue and violet rays—and they alone—cause irritation
and distress. Accordingly, he began a systematic
work on the different effects which coloured light
exerted in virtue of its properties on healthy and
diseased skin, and the beneficial effects of his dis-
covery are now restoring to health and activity every
year hundreds who but for this work on worms would
have received no effective assistance. But the earth-
worm is far more than the corpus vile of a successful
experiment. It is the unseen agriculturist, bringing
the subsoil to the surface for light, air, and rain to
vivify and replenish. It is the preserver of ancient
monuments, protecting them by an encasement of earth
from destruction. More significant still, it is one of
a tribe whose ancestors have had a great share in the
origin of higher forms of life. The links that bind
together the crab and lobster—the Crustacea—the
insects, and probably even the vertebrate animals,
find their common starting-point in the lowly worm,
and as we trace back some natural characteristics of
our race to an obscure tribe, such as the Frisian, so does
the naturalist trace the hidden peculiarities of the
structure of the higher animals to the worm, in which
those features are more manifest.

Perhaps the most unexpected results of this historic

INFLUENCE OF ANIMAL LIFE > 5

and genealogical treatment of Nature have been
obtained in the games and customs of mankind.
What seems more irresponsible than the behaviour
of village children who come every evening to a
chosen spot and sing and dance? What further
meaning can there be in a harvest supper than a
thanksgiving for the ingathering of the crop? Yet
the words children sing are often charms said before
hunting, over water, or at burial, altered almost be-
yond recognition from the invocation they represent ;
and the harvest supper, like our birthdays, Christmas
Day, and Midsummer Day, links us with pagan man
and the worship of the spirit of vegetation.

As there is no known limit to the significance of
animal life and behaviour,so we cannot set bounds to
the influence of such knowledge on human life.

Whether we consider its effect on our physical,
esthetic, or scientific faculties, we find that a biological
education offers an unrivalled field for observation,
to which even children turn with an enthusiasm that
needs rather restraining than encouraging.

The magic of life in the hidden ways and half-
lights that field-observation discovers, stimulates the
sensitive and artistic nature to a new sense of wonder.
‘The cry of the curlew is one of the three oldest cries
of the world.’ The elevating effect of the quest of
significance, the practical advances that biological
research has made and will make in hygienic and
agricultural practice, and a more vivid and intelligent

1 W. B. Yeats. |

ae gee

6 ANIMAL LIFE

sense of our community with living nature, are but
some of the influences which the study of animal life —
confers, and will confer beyond any limits we can at
present assign.

REFERENCES

Finsen, N. R. (Light Treatment of Disease). ‘ Photo- 4 ae

therapy.” Edward Arnold, 1901. A most useful summary

will be found in the ‘Quarterly Review,’ January 1906, a

pp. 138-62. -
Haddon, A. C. ‘The Study of Man.’ The Progressive ©
Science Series. John Murray.
Darwin, C. ‘Formation of Mould through the Action
of Worms.’ John Murray.

CHAPTER II

THE FULNESS OF THE EARTH

THE greatness of living nature lies in its bounty. To
the earlier races of mankind this fulness was brought
home by the increase of herds and crops, on which
their sustenance depended. ‘The cattle upon a
thousand hills,’ ‘ The valleys also are covered over
with corn ’—such were the images that conveyed a |
joyful sense of the full measure of earth’s ungrudging-
ness. From time immemorial, men have acknowledged
their dependence on the fertility of nature by appeals
to the spirit of vegetation and by charms: against
malevolent influences. They realised that success
in raising foodstuffs and stocks was only possible by
opposing the inroads of weeds and beasts of prey. In
the abundance of locusts or lions, of weeds or rust,
they saw that the fertility of nature was not directed
to the good of man only, and also that through the
powers of increase which man shares with animals and
plants, arises the keenest of all forms of the struggle
for existence. Small wonder the early shepherds cele-
brated successful harvests or increasing herds.

In later times the wonderful diversity and rich-
ness of human and animal life became more widely

8 ANIMAL LIFE

recognised. The voyages of the Spaniards and Por-
tuguese, of Cook and his successors, revealed the
presence of new races of men in many parts of the
globe, while only sixteen years ago Stanley discovered
a race of pigmies living in the equatorial forests of
Africa. Strange stories of manlike apes were brought
from Africa and Asia by travellers who described the
ferocity and strength of these gorillas-and orang-utans.
From American settlers came news of the herds of bison
that roamed the prairies, travelling from grazing-
ground to salt-lick with the same mysterious and
unfaltering precision that the camel of Eastern deserts
shows in adopting its line of march. Hunters told
of the life of the jungle, with its strange midday silence,
that each night and morning wakens into a roar of
activity ; and sailors brought back from their voyages
parrots and monkeys, pearl-shells and coral, mementos
of their travels that added emphasis to the recital
of their beach-combing adventures and opened vistas
of new worlds to their enthralled hearers. And still
there return, from the exploration of lands untrodden
before by white men, travellers laden with tidings of
new animals. The tale of earth’s fulness is not yet
complete.

Life in water as well as on land has become known
to us in similar ways.

The craft of fishing and the need for water-transport
brought the abundance of aquatic life early to the
notice of men. In pursuit of their livelihood, fishermen _
could not fail to notice the birds of the marshes, the”

ABUNDANCE OF SHORE LIFE 9

frogs of the swamp, the watering-places of deer, the
footprints and bruised reeds where wild pigs had
wallowed or cattle had come down to drink. To the
coast fishers the flocking of gulls indicated the shoals
of fry ; anda school of dolphins or porpoises in pur-
suit of mackerel or bigger game pointed out to them
those waves of migration that set in towards the shore,
and after an interval as mysteriously recoil to other
coasts or into deep water, carrying their pursuers along
in the chase.

Floating helplessly off the shore or cast up on the
beach even of our own coasts, there have been found
from time to time strange creatures that justify the
widespread feeling of the unplumbed possibilities of
the ocean: ribbon-like fish twenty feet long, huge
turtles with leathery skins, grotesque sun-fish, and
eagle-rays of gigantic size. When searching for
bait among rocks encrusted with animals, men found,
even as we find to-day, cuttlefish and conger-eels
sheltering in their crevices, strange worms of unusual
size and agility that broke into pieces which crept
and wriggled along as though the severance had
endowed them with fresh life.

With the coming of spring the longshoreman would
notice a change in the beach. Over the sands, under
the stones, and round the weeds he would find pears,
grapes, purses, and strings of jelly hardly firmer than
the stinging medusz or the fleshy polyps and anemones
that meet him the year round. He knows that, like
--the-foam, the meduse soon dry to a film, and is

10 ANIMAL LIFE

therefore led to conclude that the sea-jellies are sprung
from the foam, and that even the more substantial
creatures of the summer are also of halcyon birth.

The very names of the animal jetsam that we
pick up on the beach keep this Greek idea—that the
sea is the mother of life—fresh in our minds: the common
fleshy pink polyp, our ‘dead men’s fingers,’ is named
Alcyonium ; the jelly-like, shapeless, brownish polyp —
thrown up in ribands is Alcyonidium ; the kingfisher
that flies arrowy as foam before the wind is Halcyon ;
the days most children recall with greatest glee—the
days spent on the sands—are the halcyon ones.

That the sea-jellies are the egg-cases of fish, worms,
snails, and cuttlefish (fig. 1) is a discovery of recent
times. And yet so unwilling is the mind of seamen
to accept such a reasonable origin, that these Greek

traditions of the rise of creatures from inanimate

nature, and of the transformation of the egg-cases of
worms into young fish, survive as lustily as ever the
spread of modern education.

This acquaintance with the larger forms of animal |
life, begun by the shepherd and hunter, the fisherman
and explorer, has been continued by naturalists, with
the result that an altogether fresh idea of the fulness
of the earth has been obtained. By the use of magni-
fying-glasses it was found that creatures far smaller
than insects abounded in sea and fresh water, even
as the midges in the air or ants and greenfly on the
ground.

The furry coating of weeds, the scum round farm-

ABUNDANCE OF ANIMAL LIFE II

yards and decaying plants, the very dust of the air
and the depths of the sea, contain an abundance of

Fic. 1.—Group of Egg-capsules of a Squid (Zo/zgo), one of the Cuttlefish.
The dark spots indicate the eggs. Natural size.—(/7rom a specimen in
the Manchester Museum.)

animal life. In the far north and south, as explorers
sought the Poles, they found birds and seals in plenty ;

12 ANIMAL LIFE

whilst, under the ice, so numerous were the shrimps
that a seal’s head let down amongst them at night
was a clean skull next morning. As ships sailed
through the ice-packs the patches of discoloured water
showed the whales’ food—myriads of small organisms
drifting south with the cold Labrador current. Voy-
agers to the southward saw the water aflame with
phosphorescent light, each glowing point a living
animal. From the surface downwards, for some
twelve hundred feet, tow-nets showed the sea teeming
with animals, and, at greater depths, a peculiar but
less abundant deep-sea life flourishing amid intense
cold and darkness.

The bountifulness of nature lies on every hand if
we have but the second sight to discover it. The little
brown scales on an orange, for instance, are sedentary
female insects, other kinds of which attack the apple
and hawthorn, the larch and birch. These the tomtits
know better than we, and take for their winter food.
Greenfly, unseen in winter, becomes a plague in
summer, covering our flowers and shrubs, crops and
trees ; blown from overhanging boughs on to the corn
beneath; eating the roots at one stage, the leaf at
another; and finally, some close, warm day, drifting
in a winged swarm over the countryside. The hum
of life, now faint, now clear, is the sign of summer’s
abundance. But even winter is not lifeless to those
who know how to seek. Where leaves have drifted out
of the wind into shelter, under the warm covering of
moss, among clods of hedge-banks, in the earth under

- we SS eee

— = = SS et
Fic. 2.—A shoal of Jelly-fish, about one of which (R%zz0stoma) a group
of young Horse-mackerel are finding shelter. A Chrysaora in the
foreground, <Azrelia in the background.—(After Haeckel and

_ Kuckuck, by permission of J. B. Baillizre et Fils.)

14 ANIMAL LIFE

stones, in the mud under water, animals and their eggs
abound.

When brought into a warm room a bag of leaves
and moss, searched on a white surface, breaks out into
unexpected life—a solitary bumble-bee stirs, a newt
stretches its body, beetles uncurl their limbs and creep
about, caterpillars wake, spiders lie entranced, ants that
lay sleeping wake in agitation.

Clods broken up under warm water show as clear.

evidence of the hidden life within them. Dried
mud from distant countries will then develop the
eggs of shrimps, weeds, and Infusoria from those
lands. In this manner cultures of many kinds mav
be made.

Boundless as is the profusion of animal life, we
know that in the near and remote past its abundance
was no less. If the Pyramids of Egypt are monu-
ments of human endurance and skill, the animalcules
that compose those buildings have left therein a
record not less impressive than the tale of slaves worn
out in hodman’s service.

In the fells of northern England, in the cliffs and
downs of the south, the very rock represents the
labour of innumerable hosts of animals that have
secreted salts from the ocean and deposited them
as coral and shell, sea-lily and sea-mat. Limestone
and chalk, with all the buildings and walls made
from them, are due—and exclusively due—to living
organisms, though trace of their presence may have

SS =

REFERENCES 15

disappeared on account of the heat and pressure to
which the rock has been subjected.

REFERENCES

The discovery of man-like apes: Huzley’s ‘Man’s Place
in Nature.’ Collected Essays, vol. vii.

Greek views on evolution: H. F. Osborn, ‘From the
Greeks to Darwin.’ Macmillan & Co.

The nature of chalk: Huszley’s Collected Essays, vol. viii.

pp. 1-36.

16 ANIMAL LIFE

CHAPTER III

THE ORGANISATION OF ANIMAL LIFE

Tue thought of this abounding animal life brings
to mind its multitudinous variety ; the individuality
of man; the personal distinctness of animals, more
evident as we grow more familiar with them; the
separation of creatures into kinds or species, marked
off one from another by intangible and yet seemingly
impassable boundaries; the mighty gamut of the
scale of being. In variety, as in number, animal
life witnesses to ungrudgingness.

Yet this prolific variety is limited by orderly
control. Life everywhere displays organisation. In
plan, as in execution, this is true of the relationships
and also of the bodies of animals. That original
‘we’ is no unattached, new thing. We are body
and soul of our ancestors. In features, behaviour,
and constitution we acknowledge their gifts. Nor
does our indebtedness stop there. Brought face to face
with our poor relations, the apes and monkeys, we
see, but do not acknowledge, remoter ties. The
plan and construction of our bodies and of theirs is
the same, but we are unwilling to accept this because
we are possessed by the idea that they have too little

CLASSIFICATION 17

intelligence to be likened to man, and we forget that
it is their having intelligence at all which justifies us
in regarding them as fundamentally related to him.

From the apes we may pass to all the remaining
animals that suckle their young and are coated with
hair. These—the Mammalia—are interconnected by
ties of structural agreement which investigation dis-
covers in almost every bone and tissue, and even in
the very blooditself. As proof of relationship, blood has
lately vindicated its claim to pre-eminence. There is a
test to which the blood of each mammal responds, and
the nature of this response given by one species,
compared with that of any other species, shows the
_ close or remote connection between the two animals.

Ranking below the hairy animals, those of feather
and scale flock together. Unlike as birds and reptiles
seem, the connection between them is closer than
that between either and any known third group of
animals. It is seen in the construction of the bony
framework, of the muscles and tendons, in the
blood and in the eye, in the brain and in the egg.
All the differences which exalt the bird—warmth and
sustained activity, voice and exuberance—are the
outcome of reptilian characters.

After the reptiles come the sluggish Amphibia,
creatures of the swamps—the newts, salamanders,
frogs, and toads. Breathing both through the skin
and by the lungs, these animals are only partially
emancipated from aquatic life. In this and other .
respects they stand halfway between reptiles and fish.

Cc

18

ANIMAL LIFE

Fic. 3.—Lacerla vivipara,
the Common Brown
Lizard.—(From a speci-
men in the Manchester
Museum.)

Fic. 4.—The Common Slow-worm, a
footless Lizard (Anguts fragilis).
The thin, small specimens are ten
days old; the larger one above is
three weeks old ; the largest, below,
is five weeks old..—( rom specimens
in the Manchester Museum.)

VERTEBRATE ORGANISATION 1g

Fish alone have true median fins, and usually also
the two pairs of fins that correspond to our arms
and legs. The gills, reduced in ourselves to the
framework of the larynx and parts of the middle
ear, are seen in their full development as tufts with
elaborate bars for their support, and with muscles for
conducting gulps of water in at the mouth, over the
tufts, and out through the gill-slits. Movements of
the body are carried out mainly by the muscles of
the back and tail, which are flattened either laterally
or from above downwards; and to steady the unstable
fish and increase its propelling force the surface of
its trunk and tail is expanded into median fins. The
paired fins, so essential to higher animals for locomo-
tion, are mere steering-organs for fish, and in the
lowest fish of all—the lamprey and its allies—are
entirely dispensed with.

Between these four divisions: mammals, reptiles
and birds, amphibia, and fish, there is a deep-seated
fundamental likeness. Differing as they do in the
execution of the design, these groups agree in the plan
of their bodily structure, and for this reason they can
be classed together as vertebrate animals.

In a similar way, the bewildering variety of in-
vertebrate life can be reduced to groups subordinate
to these six larger groups: the Protozoa (simplest
and most primitive of animals); the Ccelenterates
(zoophytes, anemones and corals) ; the Molluscs ; the
Arthropods (insects, centipedes, and Crustacea) ; the

Echinoderms (sea-urchins, sea-lilies and starfish) ; the
C2

Fic. 5.—Group of Newts (7riton cristatus), showing the differences
between the Crested Male (right hand and top figures) and the
smoother Females (left and central figures). # natural size.—(/7vom
pecimens in the Manchester Museum.)

RISE AND FALL OF BYGONE RACES ar

earth and water worms. Through each of these six
divisions there runs an air or theme, of which the
animals themselves are the innumerable variations
or fugal developments.

Amongst the members of each of these principal
groups we find one dominant tendency—to possess
the earth. Having realised this, they are in turn
replaced by others, so that if by the aid of fossils we
look at the history of vertebrate life, we find as we
recede further and further from the present that in
the order of their supremacy animal groups suffer
eclipse. First, all traces of man disappear; then at a
still greater distance of time the mammals and birds
vanish; another stage further back and the reptiles,
hitherto so abundant, are no longer found; whilst
in a still more ancient time the newts die away,
leaving only fish of a few kinds analogous to our
sharks and to the garpike of American lakes. At
the most remote epoch of which we have any recog-
nisable animal records, no vertebrates are found
amongst them.

From invertebrate beginnings we find fish de-
veloping into a multitude of forms, peopling the rivers
and lakes by immigration from the sea, to which
many return, as to their true home, when their life
is ending. From the ancient armoured types to
lamprey and shark and bony fish, each division becomes
more and more complex and highly organised as
its dominion increases and its circumstances improve,
and remains simple if its life remains uniform.

22 ANIMAL LIFE

In the rivers and swamps armoured newts arose
and wandered over the damp coal-forests and lake
shores as the alligators do to-day, whilst their descend-
ants, the multitudinous frogs and toads, have still
only partially emancipated themselves from aquatic
life in order to gain that life on land which favours the
height of animal development and gives it new impetus
and variety.

The history of reptiles is a chronicle of more
stirring events. From a remote epoch, and dim as
all such origins are, the first reptiles appear, almost
indistinguishable from the armoured newts, their
contemporaries. They were the colonists of those
days, and, with an adaptive power of meeting new
circumstances that the newts had never shown,
became masters not only of the swamps but of the
sea and land. Some grew to the size and acquired
the habits and shape of whales. On land they stood
upright, high as houses, and with their hands reached
to the greener boughs of lofty trees. That most
difficult of all such conquests, the dominion of the
air, they effected, and in their own way solved the
problem of flight. Success such as this opened up
still other paths of life, for which further variety of
form was needed. Small as well as great could find
places in these newly acquired kingdoms. The
development of vertebrate life seemed a lasting work,
finished in its main outlines.

Yet in this heyday of reptilian life another group,

SUCCESSION OF ANIMAL LIFE 23

destined for supremacy on land and sea, was beginning
its career. From small rat-like creatures the earliest
mammals soon rose to manifestations of size, strength,
and pliability which only reptiles had hitherto shown ;
and as the medieval periods of the earth’s history were
ages of reptiles, so the prehistoric and historic periods
form the ages of mammals. Wave after wave of life
has risen from the inexhaustible depths of nature,
towered to a great height, and has then fallen; yet
undelayed the onward movement continues. In
variety of life the period of mammals is the richest of
all. As heir of the ages, it has the offshoots of verte:
brates and invertebrates whose first exuberance is
past. Holding the promise of the future, it contains
the seed of the coming dominant races: and to those
at their prime, those which have overcome and taken
possession, the earth yields her heaped measure of
variety and abundance.

It is therefore clear that an animal does not enter
upon its life unrelated in structure or habits either with
those about it or unadapted to the station in which
its lot is cast. Its body displays to the practised eye
unmistakable marks of its place in the organised
system of life ; and its structure bears witness to the
precise place or specific niche which it occupies in
that system. If a member of a dominant race, it
may soon step into a position which less specialised
animals of more lowly birth never attain. The land-
owner’s son has the start over the labourer’s.

24 ANIMAL LIFE

The problems by which animals.and ourselves are
confronted can be resolved into three :—

1. The maintenance of self.

2. The development of self.

3. The welfare of the race.

To the maintenance of self a station in life is
necessary, power to acquire food and to repel enemies,
ability to build up the food into that frame which is
the outcome of past history bequeathed to its possessor
by its parents. In this activity an animal is guided
by a faculty for orderly response that shapes its
behaviour. Through these responses it gains a sense
of the world around, and the habits so formed are
as original, and yet as much the outcome of latent
inherited capacity, as the body which they direct.

But an animal is not born fully formed or com-
pletely endued with all the psychic experience that it
needs. Not merely to maintain itself, but to develop,
is its task, to which every impulse awakened by the
outer world of light, water, and air, or the inner
stimulus of hunger, activity, and desire, impels it.
Impressions keener than any subsequent ones teach
a newborn creature the unexpectedness of events. . If
a marine animal, it learns the difficulties of balance,
the rise and fall of the tide, the brightness of day and

darkness of night, the qualities of surface and of deep .

water. If a land animal, it encounters the varying
heat and cold of air and earth, discovers the weight
of its body, and the difficulty of sustaining and
propelling it. If sufficient food is obtained, it grows

———E——

— a oY

DEVELOPMENT AND THE RACE 25

both in size and complexity ; and so imperious is this
demand for development that, to satisfy it and give
material for elaboration, the very tissues of an animal
may be sacrificed, and remoulded by a process to
which it passively submits.

Fresh impulses fit to guide this altered self are
developed in it, and are evoked perfectly at the first
trial, or afterafew failures. If this experience leads to
a wider range of activity, the animal rises in the scale
of being ; if it leads to a narrow range or fixed habit,
development becomes retrograde. As the responses
govern the behaviour of an animal and give it character,
so this advance or retreat of the individual is governed
by the supreme factor of racial welfare.

The welfare of the race is the end to which indi-
vidual well-being is subjected and often sacrificed.
It is rather a motive that possesses animals than is
possessed by them. It determines the formation and
policy of hives, the building of nests, the colours of
eggs, the care of the young. It transmutes inactive
fish and beasts into vigilant and ferocious defenders
of their young. It is the highest motive that governs
individual and national conduct, and has produced
-that heritage of freedom and social stability which we
enjoy as we inherit the physical and psychical organi-
sation that constitutes our being.

REFERENCES >
Past history of animals: Siv Ray Lankester, ‘ Extinct

Animals.’ .
Blood-relationship : Nuttal/, ‘ Blood-immunity and Blood-
relationship ’

26 ANIMAL LIFE

CHAPTER IV

MOVEMENT

MovEMENT, more than any other feature of animals,
brings to us the meaning and working of their life.
Activity is the sign of life, and as its manifestations
exhibit control and adaptation, so does the organism
that displays them rise in the scale of being. Begin-
ning with the animalcules and jelly-fish, which have
at best but feeble swimming movements, we pass to
the creeping things that cling to the ground or dart
spasmodically from one resting-place to another, and
then to the Crustacea and insects, in which the prob-
lems of walking on land and of flight through air are
first solved.

The flight of insects is not only the most perfect
movement known, but it has also raised these animals
to the highest place amongst invertebrates. Their
flight may be only temporary, but it is upon the
superiority so gained that their life exhibits organisa-
tion, and even civilisation of the most complex kind.

The movements of vertebrates in water, on land,
and through the air, bring home the same con-
clusion. Fish born and bred in the water are the ~
lowest members of the group ; and the most specialised

THE STUDY OF MOVEMENT 27

families of fish are those in which, as in mackerel or
tunny, the art of swimming is most masterly. Am-
phibia, that lie motionless for long intervals, have
remained stationary in the scale of being, whilst
reptiles, though capable of the most rapid running,
gliding, and striking movements, are, owing to their fre-
quent lethargy, only mediocre vertebrates, surpassed
by both mammals and birds, which in virtue of their
more sustained activity have attained the premier
position.

There is an esthetic side to the movements of
animals that makes us never tire of the spectacle.
The ease with which fish and porpoises advance, turn,
and press onwards under a sudden impulse, the sense
of restrained strength in the taut muscles of a horse
or dog, the freedom and masterliness of flight, the
graceful form and manifold rich colouring of birds,
lend inexhaustible attraction to the study of motion.

The energy of many animals has something of that
enduring and periodically varying quality that belongs
to river, wind, and sea. Gulls and albatross follow
in the wake of vessels for days, and even weeks, with
no sign of weariness, sleeping on the water and only
stooping to feed. Fish when not in active move-
ment are untiringly adjusting their balance by small
muscular contractions. The beating of the heart, on
which all other motion depends, endures night and
day, and exhibits a rhythm of diurnal quickening and
nocturnal slackening which is symbolic of the flow
and ebb that rules living and inanimate nature.

28 ANIMAL LIFE

The full epiphany of animal movement is seen
in the behaviour of migratory flocks. Migration is
essentially an oscillation between breeding-ground and
feeding-ground. On the first, nests are made and the

young reared and educated ; on the second, parents and ~

young have no connection. Each lives to himself
and the young grow to maturity.

When the nesting season approaches, an impulse,
the most powerful and selective in animal life, draws

mate to mate and fills unmated migrants with a longing.

that cannot be satisfied save in a far river, or sea, or
country. Mated couples of birds desire the particular
cottage eaves or hollow on a moorland that has served
them for nesting so long ; the pride of the hook-jawed
salmon is only satisfied by the river that he left last
year for the sea; while the upstream eels that leap
with the first autumn spate, congregate in a thick
mass on their start for the sea.

In this rush for the breeding-ground a new appear-
ance envisages the migrants, a new strength possesses
them; instincts that lay dormant rise up and direct
their way, notes unknown save at this time of dangerous
travel are heard.

Then all our migrant birds make for the north. ©

The ducks, geese and waders, the fieldfares and
redwings, leave us for the Arctic, for Norway and
Siberia. From the south come our swallows, warblers,
cuckoos. Wave after wave, starting from Algiers, Tunis,
Syria, and even the coasts of the far south, send north-
ward their migrants seeking homes. Rarely do they

EE

THE MIGRATIONS OF BIRDS 29

rest. In one or at most two flights at night is the
journey done. Flying low down over the earth and
sea if the night be dark, filling the air with their strange
migratory cries, they are carried on through all weathers
by an instinct that only errs, moth-like, at light in the
gloom ; or if the night be clear, high up, often out of
sight, where the cold and lightness of the air would
numb and overcome us, they take their way and
arrive at the haven where they would be.

But even before summer is over the return move-
ment southward begins. First the unmated birds
slip away. Then the birds of the year, perhaps under
pressure of circumstances, yield to this new migratory
impulse, that leads them to forswear the county and
country of their birth and to find their way unaided
across water to lands not their own. Lastly come the
parents, flock by flock, not in the solid phalanx that
they presented as a northward-going host, but silently
and in detachments, with the dress of spring worn out
by the summer’s housekeeping or replaced by a new
but duller garb. More leisurely now and by less direct
routes they make their way to the Mediterranean, to
the Egean, and to southward-lying lands.

Modes of Animal Movement.—If we imagine a man
in a boat provided with oars and boathook we can
think of four different ways in which he may effect
movement: by punting with one of the oars against
the bottom of the water; by hauling against brush-
wood or other obstacles on the banks ; by sculling from
the stern with a single oar, or by rowing with a pair

30 ANIMAL LIFE

of oars. The effort necessary to move the boat slowly
through calm water is but slight in comparison with
the shove and lift which we have to give in order to
bring the boat down to the water. On the water the
boat is relieved of its weight and becomes buoyant ;
on land the weight tells; never, even in our dreams, do
we imagine a boat drifting along the land.

The movements of animals are of these kinds. The
body is the boat, its muscles represent the man, and
its limbs replace the oars and boathook. Those animals
which creep over the ground use their legs as the boat-
man uses his punt-oar, pressed against the rock, sand,
or mud. Many animalcules, most worms, Crustacea,
insects, and the vertebrates except fishes, press off in
this way against some resistant medium. Burrowing.
animals lay hold of the sides of their retreat with
hooks and claws as a boathook can be used to draw
craft along river banks—of such are worms, many
Crustacea, and insects. Swimming animals undulate
the muscles of their back and tail as an oarsman
twists a scull in the stern of a boat and lays hold of
new columns of water with the blade first in one
direction and then in another. In this way, bending
the body from side to side into S and @ shaped curves,
the tail of the fish, the body of water-worms and of
aquatic larve, grip a mass of water, and, using this
as a resistant mass, bring the power of their muscles
to bear upon it momentarily, then, instantly twisting
into an inverse curve, grip a new mass, and so gain a
new forward impetus. In a somewhat different way

FLIGHT 31

the broad tail of a dog may be seen lashing wildly
from side to side in the effort of steering round a turn
when under full speed.

The act of rowing with a pair of oars leads us to
a partial understanding of that perfect and difficult
mode of movement—flight. The weight is brought to
bear on the oar at the rowlock; the fulcrum is the
advancing blade, and the power is applied at the
handle. But, though far more clumsily, we can also
row by facing forwards, grasping the oar outside the
rowlock, and paddling. It is in that position that
birds exert their muscular force; whilst in insects
there is a muscle pulling on the inside of the rowlock
for the forward stroke, as in ordinary rowing, and
another on the outside for the backward stroke. In
both cases the weight and inertia of the animal have
to be supported by the attachment of the wings to the
body ; the muscular force is applied near that inner
end, whilst the fulcrum, or point of support, is near the
tip of the wing, which lays hold of the elusive columns
of air, lifts the body, and, twisting like the sculling
oar to avoid the eddy, falls slightly, grips a new column,
and presses off against it. The faster the wing beats
the better grip of the air does it obtain ; for, as we
know by motor travelling, air becomes almost a solid
medium to cut a way through when our speed raises
its resistance to a great amount. ‘Feathering’ the
wing, therefore, even more than the similar trick
with an oar, becomes a necessity if a bird is to get
its wing up and to the front for another of those

32 ANIMAL LIFE

powerful down strokes that give effectiveness to its
flight.

But whilst we may in this way gain some acquaint-
ance with animal movement by the analogy of a
boat, there are features in the build and movements
of animals not easily paralleled. A boat is a stiff
unyielding structure, whilst an animal is provided with
mobile muscular walls, which elongate and become
thinner, or contract and thicken. Thus we may see
worms, leeches, and caterpillars extend their bodies
and, laying hold of some projection, draw themselves
up to it, measuring in this way by looping movements
the ground over which they travel, and so earning the
sobriquet geometers ; or, by more rapidly repeating
the movement, the separate events of tension and
extension become merged into a continuous gliding.
Thus the snake uses the special scales arranged down
its belly as projections for performing those rippling
movements by which it almost swims over the ground,
and in so doing helps the forward movement by
lateral undulations of the tail.

A method commonly employed amongst lower
animals, and one that has no analogy in the working
of a boat, consists in the expulsion of water from their —
bodies, and of a consequent rebound in the opposite
direction. By this means jelly-fish swim in a series
of jerks, which are due to the hollow bell or bell-clapper
alternately expanding and taking a draught of water,
then contracting and expelling it.

In a similar manner cuttlefish, octopus, and the

MOVEMENTS OF AQUATIC ANIMALS) 33

8

nautilus inhale deep draughts of water under their
gill-covers and expel them through a funnel, strongly
when at rest, violently when they wish to make
a great backward leap. Many aquatic insect-larve,
for instance those of dragon-flies, continually inhale
draughts of water, and merely increase the force with
which they expel the draught when they wish to make
a darting movement. Prawns and lobsters leap back-
wards by a somewhat different artifice, laying hold
of the water by the broad, concave under-surface of
the tail, and then bending this smartly beneath the
body.

Another mode of motion is that adopted by star-
fish and sea-urchins. The five arms or five hoops
that surround the bodies of these creatures are provided
with serried ranks of hollow tentacles ending in suckers.
When the starfish wishes to move it advances one arm,
stretches out the suckers belonging to it, and draws the
body up behind. In the same way a sea-urchin emits
long slender tentacles from its shell, and, advancing
these, draws the body in tow. The brittle’stars which
have such tentacles but no suckers at their tips,
stretch out one arm in the direction they wish to
follow, and, using the others as fins, strike the ground
with a backward sweep, and shuffle over it in an un-
gainly fashion.

The movements of animalcules : Cutliary. move-
ment.—The movement of most animalcules is due
to minute elastic hairs, which act as so many oars
projecting from the body. Unlike oars, however, these

D

34 ANIMAL LIFE

hairs derive their force not from a muscle connecting
them with the body, but from an inherent flexibility,
conferring on them the power of beating more rapidly
in one direction than in the reverse; and as they
maintain this vibratory movement with almost perfect
constancy, rarely stopping to rest, still more rarely
reversing their action, the body of the animalcule
is carried through the water in a direction opposite
to that of the more forceful stroke. If we imagine
the body provided with a membrane which bends
rapidly into a curve, straightens backwards, and
again bends forwards, we should have in this membrane
an organ acting not unlike the tail of a prawn or the
effective bend of a fish-tail. Now let us imagine the
membrane to be composed of hairs which flex and
straighten of their own accord ; then, if close set and
synchronous in their stroke, their effectiveness in
propelling the animal would hardly be less than that
of a continuous membrane, and as the animalcules are
excessively minute aquatic creatures, very small hairs,
exerting a comparatively weak force, are sufficient to
move them.

These hairs, or ‘cilia,’ as they are called, from a
supposed likeness to eyelashes, are not confined to
animalcules. They are found on the bodies of flat,
gliding worms of our streams and ponds and on the
foot of snails. They are the means whereby the
minute young of all sorts of marine animals, which
crawl or walk when older, swim about. The sea-
jellies, eggs of worms and snails, hatch out as micro-

THE NATURE OF CILIA 35

scopically small creatures, which even before birth
spin round inside their egg-capsules by the aid of
these cilia, and when out in the water glide through
it by their aid ; and the bodies of zoophytes and corals,
sea-mats and sea-mosses, of oysters, scallops, and
cockles, which appear so hard and motionless when old,
are rippled when young by the constant play of the
waving bands of cilia that, aided by the currents,
enable them to swim from the depths to the surface
and from the open sea to the shore.

Cilia such as these are not confined to the surface
of animals, nor is their only use that of locomotion.
If we buy a pennyworth of mussels from a fishmonger,
and place them in a dish of sea-water, the shellfish
will soon open their valves and protrude their yellow

skin fringed with tentacles. If a little Indian ink is -

added by a pipette, a movement in the water previously
invisible will be rendered clear. The ink will be
drawn between the tentacles into the valves ; some-
thing is at work inhaling a current of water. If now
we open one of the mussels and cut off a piece of one
of the yellow gills and place it in the water, the reason
of the current will be made clear. The morsel of
gill begins to move steadily along the bottom of the
dish, as though endowed with independent life, and,
if held up to the light in a glass dish and examined
with a magnifying-glass, the filmy margin due to
innumerable cilia can be seen. These vibrating rods,
which when held by the weight of the intact gill
sucked in a current of water, now, when attached to

D2

36 ANIMAL LIFE

a small fragment, cause this to move. Mahomet, as
it were, comes to the mountain.

But the gill of shellfish is not the only place where
cilia are found inside the bodies of complex animals.

Right up through the invertebrates and vertebrates,
with the curious exception of the insect, spider,
shrimps, and millepedes, cilia occur in some part or
other of the internal organs. Even in ourselves the
cavities of the nose and windpipe, of the brain and
spinal cord, are lined with these vibrating rods, which
bear witness to a community of substance which links
us with the animalcules themselves.

As the organs of movement, whether displacing
a minute creature or sluicing a fluid inside a large
one, these cilia bear witness to the deep-seated cause
of movement. Their activity is innate. So long
as they are bathed by water or their natural medium,
their movement is only indirectly controlled by the
action of the body, or even by its presence. If de-
tached, as they frequently are, from the dying body
of spherical jelly-fish (fig. 2) that come drifting to our
shores in summer, their movement continues for a
time unchanged in strength or pace; and while able
to survive severance from the body temporarily, they
are equally their own masters in the starting as in
the maintenance of that unresting beat. Small
wonder that organs so self-contained have been
treasured, and that scope for their energy is found
in highest and lowliest alike.

Yet all movement partakes of this mysterious,

ee

INNATE CAUSE OF MOVEMENT 37

innate character, self-caused and __ self-sustained.
Undisguised as is the control that the nervous
system exerts on our hearts, there is a cause of the
heart-beat that lies in the organ itself, and not in
any governance, however subtle and effective it
may be. The fundamental spontaneity of movement
is disguised, controlled, and rendered effectual in a
hundred ways, from the obvious exercise of our will
upon voluntary movement to the drilled soldier’s
unthinking response to the word of command, the
unconscious acts of sleep and the automatic actions
of animals. But underlying that controlled muscular
force is the older, innate contractility perfected in
one special form—ciliary movement.

Evolution of locomotor organs in animals.—In a
lowly organism, such as an earth- or water-worm,
the body consists of a muscular tube capable of
elongation and contraction, and of lateral undulating
wriggling movements. It is divided into rings, each
of which bears a number of hooks for the purpose
of creeping over the ground. In the more complex
annelids, as these creatures are called from their
segmented bodies, each ring grows out into two pairs
of leg-like processes, whereby the efficiency of pro-
gression over ground is increased. Special muscles
to move these limbs are formed, and the limbs them-
selves, in addition to bearing hooks, possess a leaf-
like outgrowth. Pairs of appendages occur on each
segment, and by their rhythmical action perform the
part of oars, sculling the body through the water, as

38 ANIMAL LIFE

well as enabling it to punt over the sea-bottom or to
climb up burrows of earth (fig. 35, p. 200).

Among Crustacea we encounter precisely the same
arrangement. Paired appendages are found on each
segment, but now, being placed nearer together on
the under-side of the body, their action is stronger and
more precise. Moreover, the appendage is divided
into inner and outer divisions, the outer one bearing
the leaf-like structures and the inner branch becoming
jointed and lobed. Such animals swim either on
their backs by strong sculling movements inwards and
backwards, or (Daphnia, fig. 24), standing vertically,
they tread the water, rising at each stroke and falling
slightly between the strokes. In higher Crustacea
the outer division disappears from the limbs of most
segments, and the inner one is converted, in the
middle of the body, into a substantial jointed leg,
capable both of clinging to holdfasts against currents
and of supporting the weight of the body in walking ;
but the original character of the limb is seen in the
swimmerets found under the tail of prawns and
lobsters. These still beat from before backwards
and ensure the forward swimming of the animal.
Thus the body becomes divided into three portions—
a head provided with jaws and antenne, a firmer middle
part for walking, and a flexible tail for swimming.
The highest Crustacea, crabs, depend altogether on
the mobility and strength of their legs for walking
or swimming. In these animals the swimmerets
are turned to other accounts, and are chiefly used for

CENTIPEDE AND INSECT 39

the carriage and protection of the eggs, or, in hermit
crabs, for grasping shells. 3

In insects we find a great variety of modes of
motion. Their larve, terrestrial or aquatic, recall

Fic. 6.—Illustrating the common starting-point of both Centipedes, or
many-legged air-breathing animals, and of the insects with six legs.
A. A Common Garden Centipede (Zzthodzus: from Koch’s ‘ Myria-
poden’). B. Scolopendrelia, the connecting link between A and C.—
(Ajter Lang.) c. A primitive Insect (A/achz/és) found under stones and
on the seashore. It shows the typical six-legged condition, but traces of
the abdominal feet are shown by the minute spines. -- (After Oudemans.)

40 ANIMAL LIFE

the less complex worms in their simple muscular
bodies, in their wriggling movements that serve for
swimming, and the looping or stretching evolutions
by which they creep. Their bodies, too, are sub-
divided into rings or segments, which bear a certain
number of appendages arranged segmentally. These
limbs, as we pass from the lower forms, such as Scolo-
pendrella, to the higher insects (fig. 5), become de-
finitely limited to three pairs for progression, and thus
entail a correspondingly greater nicety of balance.
The body becomes divided into three portions and is
balanced about the middle one of these; carrying,
in fact, to a further degree the division of the body into
head, thorax, and abdomen, already seen in Crustacea.
It is from this middle section of the body that the
wings arise. Vertically over the second and third legs,
pouch-like outgrowths of the body-wall form two
pairs of flattened lamelle, strengthened by ribs and
veinings like leaves. The arrangement of the muscles
that raise and depress the wings is a most complex
one, but consists essentially of a double lever, both
elevator and depressor acting vertically but on

opposite sides of the fulcrum. These muscles are of ©

great size and power, and where the wing meets most
resistance and does most work, namely, at its front
edge, it is stiffened by a selvage of veins.

To solve the problem of flight the economy and
distribution of weight, the intensity and application of
the muscular power have to be completely studied.

The body requires to balance about the middle,

4I

PROBLEMS OF FLIGHT

and the wings to strike so that not only an upward
but a forward or turning movement may be produced.

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This is done by the wing-muscles not only producing

an up-and-down stroke, but rotating the wing so

42 ANIMAL LIFE

that its tip describes a figure of eight between every
two up or down strokes; and in so doing uses the
effective stroke for forward movement, just as a
boat’s sail, set at any angle with the wind, plays off
the greater part of its breeze into a propelling force
brought to bear on the front edge of the sail. For
turning, the two sides of the body require to act inde-
pendently, and to lower the wing on that side towards
which it is desired to turn. The intensity and rapidity
of muscular vibration during flight are extreme;
indeed, the efficiency of insect muscle is quite extra-
ordinary, both for strength, mobility, and persistence,
and the wing-muscles are the most perfectly qualified
oi any in the body for sustained control and strong
action.

We have only to watch a hovering fly in still air, or
attempt to see a humming-bird hawk-moth flash, hover,
and dart as it passes over flowers like a sunbeam, to
realise that such insects have brought flight to a
degree of perfection that seems astounding, unnatural, —
and unnecessary. So far are we behind the meanest
fly in agility that we marvel, if at all, very much as
a savage at machinery.

The problem of effectively using two pairs of
wings simultaneously is, however, too difficult for
most insects, and we find a tendency in many groups
for the reduction of one of them. Like a boat sailing
just astern another, the back-wash and eddies in the
air caused by the front wings render the effective
working of the hind wings a great problem. Never-

FLIGHT AND SWIMMING 43

theless, the supreme exemplars of flight—dragon-
flies and hawk-moths—are amongst four-winged
insects, though even in these the hind wings tend to
become smaller than the front ones. In most moths a
hook links front and hind wings together, and the
absence of this hook serves to distinguish butterflies
from them.

In beetles the fore-wings are converted into shards
or covers, held stiffly in flight, whilst the movement
itself is entirely due to the hind-wings, which are
curiously bent near the tip, so that we do not wonder
that few shard-bearers are good fliers.

In bees and wasps the fore-wings are strongly
developed and securely hooked on the front edge of the
other pair, which in flies become reduced to balancers.
They take no part in flight, but are converted into
highly sensitive, nervous organs.

Movements of vertebrates: I. The adaptations o7
4ish.—In vertebrates, the problem of movement in
water, on land, and in air has been solved time after
time. There are walking and flying fish, swimming
and darting lizards, gliding and swimming snakes; and
winged reptiles, though now extinct, were once abun-
dant. Birds fly both in water and air, whilst bats,
amongst mammals, are almost as exclusively animals
of flight as whales and seals are animals of the water.

In the lowest fish, as in worms and insect larve, the
body is essentially a muscular tube, capable of being
thrown into wriggling, eel-like movements, by which
pressure is brought to bear on the water at each

44 ANIMAL LIFE

concavity. The tail is provided with a fin, shaped
like the propeller of a steamer, by which its grip of
the water is increased. In forward movement the
body and tail of the fish are thrown into two or more
curves, and as the body straightens, and before it
takes an opposite ‘curvature, the pressure of the tail
on the water at the hollows, and especially the grip
of the tail-fin, is greater than when the reverse curvature
is obtained. The straightening stroke is more power-
ful than the bending one. Moreover, the tail does
not merely undulate, but twists about its own axis, —
meeting the water first with one of its flat surfaces —
as it straightens, then feathering as it prepares for the
next stroke, and again straightening out with full —
force of the opposite surface and the expanded. fin.
The swirl helps the fish to gain additional purchase,
the eddy helps it to elude the water and eases the
feathering stroke. '

In order to render these undulations more effective
the swimming-muscles that run down the body start
from an elastic spinal rod, which gives them a central
origin, and form not a continuous sheath, but a
segmented mass of bundles, each bundle being bent
into a V or W shape, with the points turned towards
the head. The skin into which these muscle-bundles —
are inserted is elastic and lubricated ; and if scaly,
the points of the scales project backwards, so as
not to impede the forward movement. Moreover, the
amount of muscular tissue is increased by reducing
the space in which the internal organs are packed to

THE ADAPTATIONS OF FISH 45

a small compass, and converting the tail into a solid
mass of muscle—the main driving power of the fish.
And, further, since the animal floats, or is but slightly
heavier than its own bulk of fresh water, the vertical
strain on its body is reduced to a minimum, and there-
fore the vertebre may remain—as in sharks—gristly
or undemarcated.

The provisions for altering the direction of move-
ment are of the nicest adaptation. Since in most
fish the muscular arrangement is employed for hori-
_ zontal progression, and gives no great facility for
change of depth, a special provision is made to meet
this want: an air-bladder under the backbone is
developed, the gaseous contents of which can be
increased or decreased in amount, and so the relative
weight of the fish increased where descent is needed
and reduced where ascent is required. To this end
also the paired fins are employed, as well as for turning
and steering; and as the use of these two pairs of
fins incurs difficulties of the same order as those already
seen in insects, we find in fish, as amongst insects,
a tendency to reduce one pair—the hind fins—and
to give them another office, whilst at the same time
enlarging the fore-fins in accordance with the increased
work of guidance thrown upon them ; to which work
must be added the maintenance of the unstable
equilibrium, over which they keep constant guard.

The vertically compressed shape of a _ well-
built, active fish is such that it can never remain
upright and still. It is ceaselessly making small

46 ANIMAL LIFE

adjustments to overcome the tendency to float upon
its back. As a help towards steadying the body it
has developed fins along the middle line of the back
and tail. These ‘median’ fins act as keels or centre-
boards. They are supported by a series of spines,
which can elevate or depress the membrane they
support. The first of these spines is often stronger
than the rest, and acts as a cut-water. Moreover, to
diminish the resistance of such fins in a turning move-
ment the spines can be lowered, so that the fin collapses,
and raised again when the new tack is begun. Thus
rapidly can a shark unstep the peg that stretches
his dorsal fin and ship it again in the notch at its
base.

If such complex adjustments are needed by active
fish, we do not wonder that a change in the shape
or attitude of the body has been developed in those
which seek their food on the bottom, or wish to
escape the constant exertion of a mid-water life.
Of these, the flat-fish and skates are the most remark-
able. Connected with the dory family by many ties
of structure and mode of occurrence, the sole and
plaice, turbot and dab, agree with their relative,
the John Dory, in being flattened, but differ in resting
on or in the sand instead of hovering over it. It
might be thought that this result was merely due
to a compression of the body parallel to the ground,
but examination shows that both eyes in a flat-fish
appear on the upper coloured side, that the mouth is
awry, and that the skull-orbits are also skew-whiffed.

ee nT i ee

ee

ADAPTATIONS OF FLAT-FISH 47

In fact, a flat-fish, which begins life as a round fish,
balancing vertically, slips on to its right or left side,
which then becomes the colourless under surface,
whilst the other side is converted into a variably
tinted upper surface. The eye belonging to the side
upon the sea-bottom has rotated owing to a twist
of the orbit to the upper surface, upon which both
eyes thus appear to lie, and the animal, though flapping
through the water by vertical instead of horizontal
strokes, is still using its muscles relatively to itself
as they were employed before rotation.

The skates and rays attain their flattened shape
by compression of the more rounded body seen in
sharks and dogfish, and by an enormous extension
of the first pair of fins to form the wings, which, grow-

_ ing and fusing with the body, give rise to that diamond

shape so characteristic of the skates. These fins are
now the chief organs of locomotion, and suitably so,
since they are specially adapted to a vertical move-
ment such as the skate requires, whilst the somewhat
slender tail gives the propulsion necessary for forward
movement.

The attempts that fish have made from time to
time to walk and fly are of great interest. Many
balance themselves on their two pairs of fins and
_ grub or nose about the rocks under water ; but owing
to the unjointed nature of their limbs, this attitud
is extremely difficult to maintain on land. Yet
here and there shore-fish have adapted themselves
_ toa temporary land life. The gobies that swarm on

48 ANIMAL LIFE

our coasts have a relative on Eastern shores that hops
with great vigour on its front fins, keeping its tail
in water. A perch with the same implements manages
to shuffle up overhanging boughs, and the bat-fish
has actually developed an elbow-joint, whereby it
can rest its weight on the flat part of the fin. But
no amount of ingenuity has conferred on any fish we
know the ability to walk freely.

On the other hand, at least two groups of the
most active swimming fish have developed that power
of leaping into the air, often found in the most varied
groups, into a sustained, gliding movement which
resembles flight. For this purpose the flying-fish
employ their powerful breast fins, which they keep
spread out like a parachute. By the aid of this
aéroplane their descent is delayed; and so powerful
is the initial jump from the sea into the air that, with
a favouring breeze, they may rise on to the deck of a
steamer or go clean over a fishing-boat.

II. The adaptations of terrestrial vertebrates.—It is,
however, only when we ascend above fish to the
higher vertebrates that we find the problems of move-
mént on land and in the air completely solved.

On land, weight enters into the problem. Support, —
unneeded in the sustaining water, becomes now a
necessity ; and in order that this weight may be
upborne and moved, all the skeletal parts require to
be denser, both on account of the vertical strain they
* support and the greater muscular tension requisite
for movement. The limbs become props whilst —

ge tS em ial

ADAPTATION FOR LAND-LIFE 49

still organs of locomotion. To combine the advan-
tages of short limbs for support, and of long ones
for speed, is only one of the problems that press for
solution. To relieve the muscles of the body’s weight,
a vertical pillar-like leg is necessary. To gain the
leverage needed for propulsion, a bent leg capable
of straightening out is requisite. Hence we find that
great size in quadrupeds involves columnar limbs, with
the segments placed vertically, as in elephants; but
in smaller animals, such as horses, the fore-limb only
has this linear character, and bears greater weight,
whilst the hind-limb is thrown into a zigzag form
when at rest, and into a straighter line in movement.
Movement and rest in an erect position, as in man,
some apes, and birds, require a still greater change
in the disposition of the weight, muscles, and ligaments.
The mass of the body now falls upon the hind-limbs,
which therefore become straighter than in quadrupeds,
and the spine is sustained by ligaments that relieve
the back muscles of an otherwise constant strain. The
muscles of the shank become more strongly developed,
not only to sustain but also to propel the weight now
thrown altogether upon them. For these purposes
also the foot is not elongated into a slender organ
delicately poised on the toe-tips, as in many active
quadrupeds, but is flattened and the heel brought
down to the ground. Lastly, as an additional prop for
support, the tail may be retained and thickened, as
in the kangaroo.

A survey of the vertebrates shows how the changes

E

50 ANIMAL LIFE

to meet the needs of terrestrial movement have been
brought about from fish. Throughout the Amphibia,
with a few interesting exceptions, two pairs of limbs
corresponding to the paired fins of fishes serve in
various ways. In the newts the body is still fishlike,
but the limbs have acquired that division into upper,
middle, and lower segments (arm, forearm, and hand,
thigh, shank, and foot), that is so strikingly a character
of all the higher vertebrates.

The movements of these animals and their rela-
tives, the salamanders, are exceedingly slow. The legs
are short and bent—good, therefore, neither for bearing
weight nor as levers; and the only powerful stroke
is the fishlike, lateral bending performed by the
tail under water. Frogs and toads, however, show
an advance in their locomotive powers by the leaping
and thrusting power of their long bent hind limbs.

In the reptiles the powerful longitudinal muscles
of the back and tail, so characteristic of fish, are still
employed, and serve to assist the feet, which are short,
bent, and flattened. The movements of these animals
consist of short, violent rushes from point to point.
For sustained, rapid action neither the limbs nor the
disposition of the weight is suitable ; and reptilian life
enjoys extreme speed for short periods, alternating with
immobility for long ones. Their degeneracy is shown
in the disuse of limbs, a distinctively fishlike character,
which we find in snakes and many lizards. As com-
pensation for this loss the scales of the belly become
enlarged, and into them are inserted the ends of the

MOVEMENTS OF LIZARDS 51

very numerous ribs. When the snake desires to move,
the ribs are raised one after another by the lateral
body-muscles, and the scales, pressing against the
ground, serve to propel the body forward. At the
same time, owing to the singular flexibility of the back-
bone, the lateral, eel-like movements bring the lithe
body over the ground with great rapidity.

Although the reptiles of to-day are inferior to
those of the past, which walked erect, ran doglike or
flew, there is at least one group among them—that of
lizards—which is at its prime, and amongst these one
or two may be specially mentioned.

In zoological gardens geckos may sometimes be
seen. They are small, extremely active when roused,
and provided with padded adhesive fingers and toes.
By the aid of these pads geckos are able to perform
the strangest feats. When hunting for flies they run
up and down papered walls, and even glass windows.
So sure is their hold that they can run up a wall, bend
over, and slide along the ceiling. Like other lizards,
geckos often lie motionless for a long time, but evade
capture not by a run that can be seen but in a flash of
gliding. Such geckos are household pets in the East.
But perhaps the most agile of all is a lizard found in
Malay, which is so active as to run securely over the
tops of grass shoots.

In mammals the organs of movement are far more
effective. The tail is reduced and the longitudinal
muscles of the back—heirlooms from fishes—are
employed for the work of the shoulder and hip. The

52 ANIMAL LIFE

body is carried clear of the ground and supported
mainly on the straight fore-limbs, whilst propulsion is
effected by the more bent hind-limbs, which are straight-
ened by very powerful muscles and tendons; and to
provide a sufficiently firm point d’apput for these the
hip-girdle and vertebre of the small of the back are
greatly enlarged. To give them additional leverage
the bones of the shank and foot are elongated. To
ensure elasticity of tread, fleshy pads are developed in
carnivores under the middle joint of the toes, and in
cats the claw-bearing ones are held back in walking
by means of a tendon in a protecting sheath, and only
dart out by the action of prehensile muscles. For
support on slippery ground the heel is raised still
higher than in carnivores, and only the end joint of
the toe converted into a horny hoof. Among these
mammals, the so-called Ungulates, a remarkable reduc-
tion in the number of toes has taken place. Instead
_ of the five which only elephants have retained, rumi-
nants have only two—the third and fourth; pigs
and rhinoceros four, peccaries three, and horses one.
The cloven hoof, characteristic of those that chew the
cud, alone touches the ground, but traces of the
second and fifth toes are seen in the deer, and are of
use in spreading out the animal’s weight when soft
ground is encountered.

Of the many special modes of motion adopted by
mammals only a few can be mentioned. :

In monkeys and apes the habit of climbing and
of sitting nearly erect throws the weight of the body

Fe -

ARBOREAL AND SWIMMING MAMMALS 53

more and more on to the hind-quarters, and the arms,
thus relieved of their primitive supporting function,
are used for prehension; whilst in South American
monkeys the tail is converted into a sensitive fifth
hand for grasping boughs and giving support. In
this way many of the Quadrumana have lost the
power of rapid and effective running on the ground,
and have acquired a wholly new arboreal mode of life
and a new dexterity in the performance of their won-
derful gymnastics. For grasping the twigs monkeys
employ the hand as we do, with the grasp between
the thumb and the palm, and the most arboreal of
all are either thumbless or their fingers partially
adhere, so that their limbs are converted into mere
grasping hooks.

Ill. Adaptations for swimming and fight in
mammals.—The most remarkable adaptations to
aquatic and aérial life are found in a few groups of ©
mammals; amongst the seals and whales for swimming
and the bats for flight.

Mammals are so emphatically land animals, only
swimming by the aid of their limbs to reach new
feeding-grounds, that the existence of two aquatic
groups, one of which passes the whole of its life in the
sea, is a striking fact. So different are whales and
porpoises from ordinary mammals that the idea of
their being fish is still widely prevalent, and, though
erroneous, is intelligible by the many fishlike characters
which these animals possess.

The seal is amphibious, spending the greater part

54 ANIMAL LIFE

of its time in the sea near the coast, and only going
ashore to rest and to bring up its family. The body
is thick in front and flattened behind. The tail has
almost disappeared, and on either side of it the hind
limbs are held rigidly out at full length. Between
the fingers and toes the skin has grown so as to convert
the fore-limbs into paddles and the hind-limbs into a
propeller. On land a seal shuffles awkwardly on its
belly, only using its hands if pressed; but at sea the
flattened hind-limbs, together with the lateral muscles

Fic. 9.— The White Seal (Zododon) of Antarctic shores.—({ rom a
specimen in the Manchester Museum x 3.)

of the body, enable it both to swim with great ease
and to ascend periodically to the surface for air. The
forepaws are used for steering.

The porpoises and dolphins, the baleen and toothed
whales, are as perfect in the art of swimming as any
fish. Their bodies, denuded of hair, are usually of a
build so completely adapted for cleaving the water
that boat-builders could design the lines of their craft
from models of whales. The head is a cone pointed in

ADAPTATIONS OF WHALES 55

front; the neck is not marked; the back rises in a
curve that gives easiest passage through the water,
and finishes off behind in a tail flattened from above
downwards. The general aspect and build resemble
those of a free-swimming fish, but, whilst fish have
a vertically flattened tail for horizontal movement,
whales require a horizontally compressed tail to make
those periodical ascents requisite for breathing air.

Forward movement is maintained slowly or. at
a prodigious speed by the huge longitudinal tail-
muscles swaying the body from side to side and making
effective undulations on the principle of a fish. The
legs are hidden and rudimentary, and their muscles
are added to those of the back: whilst the arms are
converted into steering-paddles as near a return to
fins as is well possible. The fingers, though still five
in number, are composed of more joints than the other-
wise universal number, three. The nails have dis-
appeared. Weight and size, no longer limited by the
supporting power of the limb, may reach colossal
dimensions; whales of eighty feet in length and
weighing eighty tons still abound.

To acquire powers of flight is perhaps an even
greater feat than the conversion of a terrestrial animal
into a whale. Amongst various groups of mammals
the first stage of flight—the arrest of the body in a
gliding descent, instead of in a straight fall, has been
accomplished. Some of the opossums have extended
that fold of skin which allows movement of our arms
at the. armpit, into a membrane that stretches from

56 ANIMAL LIFE

the arm to the toes. By its aid their leap off a branch
takes the form of a rise into the air, then a gentle
downward curve. Amongst the squirrels two forms
of such ‘ aéroplanes ’ have been devised independently,
and by the aid of these, flying leaps can be made from
tree to tree without descending to the ground. But
it is only amongst the bats that true flight has been
attained. Like huge moths, these animals come out
every summer evening from the ivy, hollow tree, or
barns in which they lie hidden by day, hanging down-
wards from some projection, often in great clusters,
with their head enfolded by the wings. _

These wings are folds of skin stretched from the
altered hands and arms to the legs. To increase their
extent the fingers are drawn out to an immense length
and the wing-membrane continued to the very tips,
leaving only the thumb free. The muscles for flight
are strongly developed, and, as in a bird, lead to the
formation of a keel-like breast-bone, from which they
arise (fig. 8, p. 41).

The unerring certainty of a bat’s flying and alighting
movements is a marvel of skill. In a room they
explore the furniture and recesses, sail through pas-
sages a few inches wide without touching anything,
dive under a sofa, and, turning a somersault, alight on
the webbing head downwards, ready for the next
flight. Then they spring clean into the air, even from
a flat surface, and are on the wing at once.

The inclusion of the hind-limbs in the formation
of the wings has the effect of bending the knee out-

i all

ADAPTATIONS OF BIRDS 57

wards and backwards, instead of forwards as in
all other mammals, and this, together with the pre-
occupation of all the hand but the thumb, renders
walking difficult. On a flat surface some bats cannot
walk; but others, such as the long-eared bat, progress
in the usual way—first a hind-foot is advanced, then the
fore-foot of the same side, followed by similar move-
ments of the opposite limbs.

IV. The adaptations of birds for fight and
perching.—But it is amongst birds that we encounter
the greatest freedom and most sustained powers of
movement. To gain the dominion of the air by the
use of wings, whilst yet retaining the power of balancing
on the two legs, is a double problem of the utmost
difficulty, and in the solution every part of a bird’s
body has undergone some adaptive change. What a
feat this is we may judge on considering the imperfect
attempts man has made towards constructing an
efficient flying-machine, though he has tried for a
century. But in a bird, so little cumbrous is the
mechanism that its sails can be folded evenly with the
contour. of the body; so efficient, that flight at express-
train speed and sailing in great winding circles with
outstretched, motionless wings are both performed
with the same easy mastery as perching or hopping ;
so well guided, that migratory birds sweep through
immense tracts of air and reach their destination witha
punctuality so sure that the Persian calendar is based
on their arrival..

The general shape of a bird fits it for rapid flight.

58 ANIMAL LIFE

The pointed head serves to form a passage through
the air, into which the rising slope of the body follows,
whilst the falling slope of the tail allows the air to
glide off rapidly. The weight is taken off all the
peripheral parts and centred in the massive muscles
of the breast and the parts adjoining ; yet so delicately
poised that by extending its mobile neck the bird,
gliding with outstretched wings, descends where it will.
By letting the legs fall the head is thrown upwards,
the point of balance being thus moved slightly for-
wards or backwards without the aid of the wings.
These wings or sails are essentially fore-limbs, similar
to our own, but modified in every feature for the
needs of flight. The arm rises upwards and back-
wards, the forearm forwards and upwards, the hand
backwards and upwards, forming at rest a zigzag,
with the elbow pointing backwards and the wrist
forwards, but in action extending into a straight line,

Fic. 10.—The Pigeon. Dissection of the male from the right side. Half
the liver and the greater part of the intestine have been removed. In
the right wing, the bones and the arrangement of the primary and
secondary feathers are shown.—(/vom Marshall and Hurst, * Practical
Zoology.’)

A, nostril. AD, ad-digital primary feather. B, external audi meatus. BW.
bastard wing. C, esophagus. CA, right carotid artery. D, crop. DA, aorta. E, keel
of the sternum. F, right auricle. G, right ventricle. HV, hepatic vein. Hr, left bile-
duct. Ha, right bile-duct. I, distal end of stomach. iA, right innominate artery.
IV, posterior vena cava. JA, left innominate artery. JV, right jugular vein. K, gizzard.
L, liver. M, proximal limb of duodenum. MD, the two mid-digital primary feathers.
MP the six metacarpal primary feathers. Mz, first metacarpal. Me, second metacarpal.
M3, third metacarpal. N, cloacal aperture. Nx, first digit of manus. O, bursa Fabricii.
Or, proximal phalanx of second digit of manus. Oz, distal phalanx of second digit of
manus. P, pancreas. PA, right pectoral artery. PD, pre-digital b aherge feather.
PV, portal vein. Px, first pancreatic duct. Pe, second pancreatic duct. P3, third
pancreatic duct. Q, pygostyle. R, rectum. KC, radial bone. RX, rectrices or
tail-feathers. Rx, third digit of manus. S, ureter. SA, right subclavian artery. SV,
right anterior vena cava. T, rectal diverticulum. U, kidney. UC, ulnar carpal bone.
V, pelvis. W, lung. X, humerus. Y, radius. Z, ulna. .

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60 ANIMAL LIFE

which, moving freely at the shoulder, sweeps the tip
of the wings in spirals. Length of wing is given in
two ways: by elongation of the arm and hand, as in
storks, or by increase of the feathers in length, as in
swallows ; and as we saw that in the fleetest mammals
length of limb and reduction in the number of fingers
or toes went together, so in birds we find that only
two of the usual five fingers are used for the support
of the greater part of the wing. The skin between
these fingers and at each side of the wing grows into
flaps, which, being covered with feathers, form an
aéroplane triangular in surface-outline, and yet
curved so as to furnish a concavity below and a con-
vexity above. Upon such a membrane, only flying
leaps like those of squirrels could be carried out. To
convert the feathered membrane into a true wing it
must be provided with muscles sufficiently powerful
to lift the bird into the air; and since not only upward
but also forward movement is required, the direction
of the wing has to be so inclined to that of the air-
current as to convert the oblique thrust into a large,
forwardly-acting component and a small, inactive one
at right angles to this, just as a boat’s sail plays off the
force of wind into a propelling and a drifting force,
or as an insect’s wing or fish’s tail solves the same
problem of resolution. Hence the need for the powerful
breast muscles, mainly for depressing the wing not
in one vertical plane but obliquely downwards and
backwards. And since the efficiency of stroke is
guided by the speed of the bird relative to that of the

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ADAPTATIONS OF BIRDS | 61

air, in a calm rapidity, in a breeze slowness, of succes-
sional stroke will characterise the beating of the wing.
Further, since the resistance of the air increases with
great rapidity as the speed freshens, the wing after
one downstroke has to be lifted home edgewise for the
next, so as not to stop the momentum; and this
turning movement brings the wing not full-sail up to
the vertical, but slews the front edge, somewhat flexed,
to the front, and then extends it high above the head
ready for another powerful sweep.

To gain support from the air and to assist flight,
the details of shape and feathering of the wing are
modified. The lower surface grips the air chiefly by
its front edge and tip, and as a jib sail, though narrow
and triangular, must be strengthened on its front edge,
so good fliers need strong edge feathers and narrow,
pointed wings. The feathers are elaborately airtight to
enhance that grip, yet are disposed so as to allow air to
flow edgewise between them and over the convexity of
the upper surface as it comes forward. The difference
in the width of the vane on either side of the feather’s
stem is not without its meaning, for, when a flat body
is falling obliquely through the air, the pressure be-
comes greatest not at the centre but towards the front
edge, which tends to rise. If, therefore, the front webs
of the first eight flight feathers were equal in width
to the hind vanes, the outstretched wings would tilt
up and the bird’s balance would be destroyed. It is
to avoid this disturbance that the outer webbing of
the feathers, upon which the main stress falls, is reduced

62 ANIMAL LIFE

in width (fig. 8). The form, then, not only of the wing,
but of every flight feather—hollow and sustaining below,
rounded and unresistant above, short and rounded
for more laborious flight, long and pointed for easy,
sustained flight—has a definite significance for all
the varied needs of birds and their more elaborate
evolutions, such as sailing and soaring. And in those
cases in which flight is abandoned and the wing,
as in penguins, is converted into a fin, the feathers take
on the form most suitable to the needs of an aquatic
life and form scale-like coverings.

Flight, however, is not the only movement for
which birds are fitted; and if the fore part of the
body is exquisitely adapted to meet the require-
ments of aérial life, the hinder part is mainly a
mechanism for terrestrial and aquatic existence, for
running, perching, or swimming. Such a double
adaptation is a rare thing in animals, and is only
shared by insects. All others that specialise in
movement—fish, whales, bats—have become incap-
able of rapid and sustained travel in an alternative
manner. Birds alone are capable of both flight and
bipedal movement.

The legs of a bird have a double office. They
sustain and propel the body’s weight, which is disposed
so as to fall about the knee-joint.

For sustenance the limbs are pillar-like, and
distribute the pressure over four divergent toes.
For propulsion the joints are elongated, and the hip-
girdle, or ‘back’ of the bird, affords a large area,

ADAPTATIONS FOR PERCHING 63

from which the powerful leg-muscles send down their
tendons, which bend the knee and the toes, and, so
doing, thrust the body forward. The thigh is short
and the knee buried in the body’s side. What appears
to be the backwardly pointing knee is in reality the
ankle-joint, and separates the shank from those bones
which in ourselves lie flat, but which in a bird are
drawn up to form a vertical column extending the
length of the limb, and giving it additional power of
movement. Just as in a horse or antelope great
speed is gained by the larger joints of shank and foot
bone, so in a bird the corresponding bones are
drawn out into an elongated zigzag. In the most
perfect runner amongst birds—the ostrich—the reduc-
tion in the number of toes and the elastic padding
for treading over sand have followed precisely on the
lines adopted by the camel.

The majority of birds possess feet suitable for
perching or swimming, and the ease with which they
securely alight, sleep resting on one leg, or paddle
through water, involves a mechanism as perfect in
; its adaptation to these ends as is that of the wings for
flight. Of the four toes usually present, one corre-

_ sponding to the first of lizards is commonly opposed to

_ the rest,so that the claw of the middle toe in front over-
_ laps that of the hind toe and holds the twig between.
Now by a labour-saving mechanism this hold, appar-
ently so precarious, is rendered automatically secure.
Along the front of the knee there runs a tendon which
_ passes down the leg and ends on the under-side of the

64 ANIMAL LIFE

toes. Any bending of the knee, therefore, tightens the
hold of the feet; and this hold is rendered still more
secure by another tendon which runs at the back of the
leg and divides into three—one for each toe. When
the bird perches, the weight of the body thrusts the
knee out and the ankle back, and simultaneously
tightens both sets of tendons, and through them the
hold of the feet.

In swimming-birds this flexure is the means whereby
the membrane between the toes is opened and brought
to bear on the water; but, in order that the resistance
of the feet may be overcome, when the forward
stroke is to be made, the membrane is rendered
capable of opening and shutting, and the toes are
spread out during the swimming, or back-stroke, and
brought together during the forward one. In a
grebe’s foot the vanes down the toes can be pulled
out flat by the back tendon and turned down vertically
by the front one. The foot of a bird, no less than
any other part of its body, gives evidence of the
most exquisite finish and usefulness.

REFERENCES

Animal locomotion: Pettigrew, J. B., ‘ Inter. Sci. Series,’
vol. vii. Marey, ‘Animal Mechanism.’ Ibid. vol. xi.

Flight: Headley, F., ‘The Structure and Life of Birds.’
Macmillan.

65.

CHAPTER V°

THE QUEST FOR FOOD

THE need for self-maintenance leads an animal to
feed. To whatever end its energy is directed, loss
of substance is incurred by its movement, and even
by its rest. When we are lying down the breast
still rises and falls, the heart beats, the blood flows,
the glands secrete, digest, and store; the brain is not
altogether still, and may plan in sleep works and
compositions beyond the power of our waking selves
to execute. Even the muscles, quiet as they seem,
are doing internal work. By day and night, actively
or restfully, the basis of life is used up and needs
renewal. How to meet this urgent demand for
material we have now to consider. —

The source of animal food : the quest for plants.—
The kindly fruit of the earth is the source of animal
food. Directly or indirectly, animal life is depen-
dent on plants, visible or invisible, and so great
is the supply that a flesh diet becomes anomalous.
The earth is covered with verdure; the sea is fringed
with weeds and teems with minute plants. Soil is
the remains of the vesture that waves in the wind
and water, held in a meshwork of moulds. Diatoms,

F

66 ANIMAL LIFE

minute plants enclosed in flinty cases, surpass sand-
grains in multitude; they encrust the shore, fill the
beds of rivers, and, borne on the air, are showered
down upon sea and land from the tropics to the
poles.

The oldest and simplest way of catching food is
that practised by the lower aquatic animals : sponges,
corals, animalcules, and all encrusting organisms. It
consists in drinking the water and sifting from it the
minute organisms that abound therein. It is carried
out by the aid of those minute, vibratile hairs or
cilia which, originally used for drawing the animal
through the water, now draw water through the
animal. Into the vortex created by the beating of
these organs will be haled from the surrounding
catchment-area all those particles which cannot
resist suction, however gentle; and as animal and
plant spores abound in fresh and salt water during
the spring and summer, the particles inhaled will
consist partially, at least, of minute organisms, and
upon these the sponge or coral is able to live. Ina
similar manner, barnacles throw out and draw in their
casting-nets and collect the fine wreckage of the coast
which constitutes their food.

Most of the animals that feed in this way are
fixed, and when at the approach of winter the supply
of minute organisms falls off, they have no means of
leaving the coast or lake shore for more teeming
water. In order that they shall not starve during
this season, most encrusting animals lay up during

THE QUEST. FOR ‘PLANTS 67

the autumn stores of highly concentrated nourish-
ment, such as starch and oil, within their tissues.
Having done this they hibernate, and such food as
they require until the next spring is supplied out of
these reserves.

The larger plants afford nourishment to larger
or more active animals, and there is hardly a weed
or flower or tree that does not support a varied
assemblage of.adherents. The tangles of submarine
groves of seaweed and pondweed are cropped by fish
and. scoured by snails. Every part of land plants—
the roots and young succulent leaves, the nectar, the
sap, the fruits, wood, and even the galls—furnishes
nourishment to insects and their young. Nor is the
plant merely food to them. Shelter can be found in
the innumerable crevices of bark and leaf. Air is
afforded by the spaces and tubes that traverse the
tissues. The very. sheddings of plants are true wind-
falls for other creatures. The bud-scales of spring,
the leaves and fruits of autumn, all the fine débris
that rain down on to the earth beneath, are gathered
by ants and birds, eaten by slugs, and remoulded by
worms. Weed jetsam is similarly refined. The ebb-
tide, that leaves the seaweed stranded in heaps, exposes
the burrows of innumerable hungry scavengers in the
sand. - Each evening, when the tide serves, the sand-
hoppers creep: out of their hiding-places near high-
water mark and begin their mazy dance in search
of drift-weed ; whilst myriads of- smaller shrimps,
“each ‘enclosed in a minute bivalve shell, career
F2

68 ANIMAL LIFE

unceasingly over their food. Dustman service is the
lot of many. Earth and water are kept clean by their
unwearied efforts (fig. I1).

In order to gather their food-plants, insects and
Crustacea employ a similar series of mouth - part
diversely shaped according to the special needs of
each class. Their mouth is overhung by a mobile
upper lip, and enclosed at the sides by a pair of appen-
dages constructed on the same plan as the swimming
or walking legs, but modified to form jaws, that

Fic. 11.—The Common Sand-Hopper (Gammarus locusta). A similar
form is common in fresh water.—(A/ter Della Valle.) x 4.

work from side to side and chew the food between
them. Behind these a lower lip is formed by a pair
of limbs that still show that division into inner and
outer lobes that betrays their alliance with swimmerets ;
and usually there is added to these yet another pair
of members of similar bifid nature. These parts of the
lower lip were originally sensitive vibrating paddles,
and their accustomed movements had to be but
slightly altered to fit them for chewing and tasting,
instead of paddling. Provided with these, insect and

/

SAND-HOPPERS 69

shrimp can test the weed, cut out parts of their food-
plant, and masticate it.

The large specimen is a Male ; the two

others, partially concealed in their tubes of mud, are Females.—(From Della Valle.)

Fic, 12.—Tube-forming Sand-Hoppers (Corophium).

But ‘as insects became adapted to subsist on
the higher plants, their biting habits led to a great
discovery. Once through the bark or leaf their jaws

70 ANIMAL LIFE

would meet with a sweet, sticky sap; through the hole
made more and more would rise. Such a fragrant
bouquet no water plant possesses. Such a rising
sap no seaweed or pondweed exudes. To be able to

Fic, 13.—A group of Necrophorus and Aphodius Beetles

burying a Bird.—(/ vom a specimen in the Manchester
Museum.)

lick or suck now becomes the insect’s advantage, for
sap is not only more fragrant, but far more easily
digested than almost any other vegetable food, and
all manner of brushes, tubes, and tongues have been

INSECTS IN SEARCH OF HONEY 71

evolved for the purpose. The lower lip is drawn out
spoutwise to catch and then to drink or lap up the
juice, or else becomes hairy to absorb it. Finally,
of its two parts, that forming the tongue becomes

Fic. 14.—A small primitive Insect (Orchesel/a cincta) found under
stones, representative of an early group of insects from which the
sucking forms have since developed.—(A/ter Lubbock. Re-
produced by permission of Lord Avebury from his Monograph,
published by the Ray Society.) x10.

drawn out into a tube of marvellous complexity, up

which the sap is pumped by a piston developed inside
the throat. j .

When gathering honey, insects perform the memor-

72 ANIMAL LIFE

able service of cross-fertilisation to the plants they
visit. In the act of dipping the tongue into the
corolla to tap the nectaries the insect dusts its head and
legs with mealy pollen. Thus powdered, it flies to
the next flower or another plant of the same kind, and
when unfurling its proboscis strikes gently against the
pillared stigma that stands central in the corolla and
cross-fertilises it.

The advantages of cross-breeding over inbreeding
are many and great. In vigour, colour, abundance of
fruit, crossbred plants are superior to inbred ones.
But since plants are fixed organisms, the pollen has
to be borne from flower to flower, or from a male tree
to a female, by one of the three moving agencies,
water, air, or animals. Flowers are in the main
devices to attract the notice of animals and to
ensure pollination. Brilliancy of colour, definiteness of
pattern, attractiveness of odour, serve to draw the
curiosity of animals. The opening of strong-smelling
plants by night entices nocturnal creatures to visit
them. Of the numerous applicants drawn by this
bounty not all are helpful. Sparrows confer no benefit
on crocuses by their ruthless destruction of early
blooms. Slugs are the gardener’s greatest foe. But
the great majority of flying insects are drawn, not to
an indiscriminate destruction of the flower, but to the
nectaries, or honey-sacs, which secrete the odour from —
within it.

The interaction between flowers and the insects
that visit them is one of the most interesting chapters

THE FOOD OF SNAILS . 73

in natural history. So intimately are they dependent
on one another that some plants, such as certain figs
and the Yucca palm, would die out were it not fora
small wasp in the one case and a minute moth in the
other, that serve, and alone serve, to ensure fertilisation.

Another method of obtaining vegetable food is
that practised by snails and slugs. These animals
browse on aquatic and terrestrial plants by rasping
away the surface of the plant between their prickly
tongue and horny upper jaw. This method is, on a
small scale, the one adopted by ruminants, such as cows
and sheep, which grip their food between the tongue
and horny pad of the upper jaw, and in both cases the
lips are used to bring the food to the teeth. But in
the snail the tongue is covered with a ribbon bearing
horny teeth, which as fast as they wear away are
replaced by new ones, and the action of these teeth is
not unlike that of the cutter in a lawn-mower, while
the fixed upper jaw of the snail corresponds to the
bar against which the cutter clips off the grass. By the
aid of this rasping tongue snails and slugs are able
to obtain food in. almost all circumstances. The
covering of slimy alge on the seashore, the green
scum that appears on pools and roadsides, the liver-
worts, mosses, fungi, lichens, and most of the higher
plants, provide an endless store of provender. So
great is the injury done by snails, without any counter-
balancing advantage, such as many insects confer,
that plants have sought to protect themselves against
these attacks by various methods. So general is this

74 ANIMAL LIFE

need for protection that every flowering plant possesses
some means of defence: hardness or prickliness, irri-
tating lime salts, or acrid and oily juices. Against
the attacks of some slugs, however, even such defences
as poison may fail. The great black Avion will eat
almost anything; but all the slugs of our gardens are
not equally to blame for the immense damage to bulbs,
seedlings, and plants that is often set down to them
indiscriminately. The field Limax and the keeled
Limax are the two most culpable destroyers, and it is
to these that the disappearance of bulbs is largely due.
The great Limax, on the other hand, does not appear
to touch green food, but subsists on moulds; the
margined slug on lichens only. They forage night
after night over the same beat, and return by day to
the same hiding-places. Latter’s work (quoted on
p. 300) helps one to identify them.

Forest, moor, and plain support an abundance of
mammals. Herbs are sought after by the largest and
smallest of beasts. All the ‘ ungulates ’—elephants,
horses, cattle, and deer—are herbivorous, and live in
troops led by an old male. Less imposing, but more
numerous than these, are the rabbits, mice, squirrels,
and beavers, great in their powers of destruction,
though individually small, and some, such as harvest-
mice, scarcely bigger than insects. Monkeys, where
protected, as in India, become a pest, and not only
destroy the fruit of the forest, but do immense damage
to gardens.

The different ways in which mammals gather

HERBIVOROUS MAMMALS 75

their food are of interest. The majority use their
teeth, which, in such cases, are chisel-shaped in front.
‘All the ruminants press the grass between their tongue
and upper toothless gums. The horse grasps with his
lips, the tapir with the longer flexible snout which,
in the elephant, is drawn out into a trunk of the utmost
sensitiveness and strength, serving not only to reach
up to lofty boughs for the juicier leaves, but also
to overturn trees whose summits are out of reach.
Squirrels and monkeys, on the contrary, use their hands
for conveying food to the mouth.

The need for thoroughly chewing such food has
entailed great modifications of the teeth and face.
The long face of the horse is due to the lodgment
of.many grinders. The complex form and _ large
size of these teeth enable them to act as a mill,
those of the upper jaw fitting into the hollows and
bosses of the lower teeth ; whereas, since the upper and
lower jaws of the ruminants are not equally wide, the
teeth act intermittently on one side first and then on
the other. To equip themselves for encountering dusty
herbage, the Herbivora have developed an elaborate
arrangement for separating dust and pollen from the
air which enters the nose in order to gain the lungs.
The bones that form the framework and support of
the nasal passages are converted into labyrinths, so
that the air whirls round on its way to the lungs,
and in so doing deposits the heavier particles on the
sticky walls, as a ‘separator’ divides the cream from
themilk. The dust, pollen, and spores are then carried

76 ANIMAL LIFE

outwards by the set of the ciliary current, which, as we
saw, maintains an outgoing flow. The ‘ turbinals,’ as
these labyrinths are called, help in other ways, by
warming and scenting the air, and serve to build up
the long and stout face that distinguishes herbivorous
animals.
Another means of rendering the food easily
digestible is known as chewing the cud. The cud is
not the herbage taken straight from the field, but
consists of a mass of pulpy grass which has undergone
partial digestion, and has been sent back into the
mouth for a thorough mastication. All animals with
a cloven hoof, except pigs, are ruminants, whilst
those which have more than two complete toes or only
one, are not provided with this singular mechanism.
Among the birds, devices of a much less complex
kind are adopted for obtaining a vegetarian diet.
But few birds subsist on leaves, for their innutritious
character makes it necessary to gather large supplies
in order to furnish even a small amount of food, and
then it is only obtained at the expense of much hard
mastication. For a bird such a diet is eminently
unsuitable, since it neither wishes to overweight itself
with a heavy meal nor has it teeth to grind with.
Unlike the ruminants, which graze in safety, most
birds appear perpetually harassed by real or imaginary
fears, and need a light, stimulating diet to replace the
great loss of material and energy which they expend
in active, sustained movement, and many other
ways. For them, therefore, oil, starch, and other

FOOD AND EVOLUTION i |

essences of seeds and fruits are the most suitable
nutriment, and to obtain these the beak is strengthened
and sharpened. The necessary crushing is done by
the action of the gizzard, which is usually aided by
stones or gravel. The hard, conical beak of the finches
serves to crack the seeds and fruits of the garden
and hedgerow ; the still more massive jaws of the
parrots break the hard-shelled fruits of the tropics ;
the twisted beak of the crossbill extracts the seeds of
pine-cones. In the delicate humming-birds of South
America the bill is elongated and the tongue con-
verted into a double tube like that of insects. It is
used for tapping insects and the nectaries of flowers,
which thus give meat and drink to the most exquisite
and airy of known beings.

This brief ‘summary’ of vegetarian dietary sug-
gests the relation of food to evolution. Plants them-
selves have a long history, in which alge and fungi
occupy the earlier pages, lichens, liverworts, and
ferns the medizval sections, whilst gymnosperms and
flowering plants bring us to modern times ; and we can
follow the adoption of simple plants as food by the
more primitive land animals, and the assimilation of
the higher plants by animals which had become more
specialised. That many-limbed animals live amongst
moulds and the few-limbed creatures feed delicately
on fruit or nectar is no casual association, but a fact
that testifies to the antiquity of the one and the novelty
and high place of the other. We shall also find that
as many plants chequer the monotony of their diet

78 ANIMAL LIFE

by a side-dish of fly-juice, so vegetarian animals may
lose their strictness and vary their menu with flesh,
and only after obtaining a commanding station do
their succeeding generations revert to that safe but
laborious habit of grazing from which they set out.

The quest for prey : 1. The supply of food in the sea.
We speak, and rightly speak, of the heaped measure
of plant life and of the dependence of animals upon
the pastures so provided. But there are common-
wealths in which plants shrink to an invisible factor
where yet animal life abounds. The high seas and
the depths of the ocean teem with animals, yet it is
only in the Sargasso Sea that weeds are visible, and
much below the surface they are unable to live. Lakes
and broad rivers, Arctic and Antarctic lands, sandy
coasts and volcanic districts, are only fringed or
powdered, as it were, with plant life. Yet in all these
regions animals are found, and it would only be pos-
sible for them to maintain a strictly vegetarian diet
by an enormous reduction in their numbers. As a
matter of experience we know that many animals
are carnivorous by preference and nature. The mole
would die in the richest garden mould that contained
no worms, and the spider would starve in a well-kept
hothouse. How this carnivorous mode of life has
been attained is the problem before us.

Drifting on the waters and raining down into its
depths is a motley collection of flotsam, part plant,
part animal. Covering the rocks and weeds are the
infusoria, sponges and barnacles, hydroids and coral

CAPTURE OF ANIMAL FOOD 79

polyps, sea-squirts and bivalves, whose irrigation
works are ceaselessly straining the water, filtering off
and digesting the drift life. Between the two con-
stituent kinds of filtrates, plant and animal, they do
not distinguish, but swallow and digest them both.
A plant, however, is more difficult to digest, as around
each element of its tissues. there is a tough covering
such as animals only possess on their outer surface.
Hence an animal once captured and torn is quickly
digested, whereas a marine or aquatic plant is only
dissolved with great. difficulty. We are not surprised,
therefore, to find that plants may live for a consider-
able time in the body of an animal, and, on the other
hand, that animal food, being juicy and stimulating,
would force the growth of those fixed creatures which
attempted the diet. The hydroids, jelly-fish, and
anemones have made both these discoveries, and the
larger they grow the more confirmed becomes their
carnivorous habit. Little by little the power of
holding and then numbing moving prey was deve-
loped. Stickiness was a necessity to prevent the
tissues becoming waterlogged and the cilia from
flagging, and to this slimy covering these resourceful
creatures added the power of poisoning their captives
by the aid of nettle-cells, with which jelly-fish and
anemones sharply annoy us when bathing or wading.
To digest this animal food was no new or great dif-
ficulty, for the lower animals feed upon their own
tissues when other food is lacking, as it often is in
winter, and a jelly-fish the size of a. saucer becomes,

80 ANIMAL LIFE

if starved, microscopic and ultimately dissolves.
Right down at the base of the animal kingdom, there-
fore, we find the body feeding on itself or on some
other animal—in times of famine diminishing, in
times of plenty growing, budding and overflowing
into its children. As the jelly-fish are budded off
they leave the shore, pass into deep water, and find
themselves amongst less and less vegetable food.
Their activity demands nourishment, and a deliberate
choice of prey is made from amongst their fellows.

It is to the sea with its stress of life that we may
look for one explanation of the varied food of animals.
The strand itself, barren and lifeless as it appears,
is full of buried minuscules, plant and animal. On
this supply the larger animals depend, and in it they
bury themselves. The lugworm (fig. 26, E) and heart-
urchin (fig. 26,A) are but two examples out of many
that eat the very strand in order to gain its hidden
nutriment. Mollusc and urchin, though protected by
armour and spines, are the resort of parasitic sea-
worms and crabs that when young have gained a hold
or an entrance into these citadels and grow to maturity
on the secretions and crumbs of their host. The mussel
shelters the pea-crab (fig. 15), the prickly urchin a
sea-worm or a small bivalve.

These feeders on the minuscular life of the shore
are in turn the prey of other animals. Scallop and
oyster, seemingly so well protected by their shells
and strong muscles, are the particular food of the
starfish. Humping itself over the bivalve, the star-

Fic. 15.—A Mussel opened to show the Pea-Crabs (Male ¢ and Female 9 )
within it. The Female is the larger of the two Sexes.—(From
specimens in the Manchester Museum.)

G

82 ANIMAL LIFE

fish plants its suckered feet firmly on the ground, and
then applies two or more ranks of these suckers against’
the valves (fig. 16); straining to separate them. The
oyster claps its shell together at the first touch, but
after the tireless starfish has maintained an even
strain for a time, the oyster from fatigue and want of
oxygen opens its valves. Through the opening the
starfish inserts its acid stomach, and the secretion of
this falling on the oyster’s muscle weakens it. The
valves gape open, and the starfish at its leisure absorbs:
the contents.

Away from the shore great activity is employed.
The maintenance of equilibrium, the pursuit of food,
and the avoidance of powerful agitation imply sus-
tained movement. Jelly-fish, cuttlefish, fish of all
kinds, are in constant muscular tension. Hunger
follows ; the cold open sea and strong aérated water
sharpen the appetite that constant exercise produces.
Around these hungry swimmers is a drifting stream
of wriggling, darting, whirling particles—the offspring
of the shore. These enter into every mouthful of
water that a fish takes to discharge over its gills,
or that a jelly-fish inhales for a fresh spurt, and the
choice of food is soon determined.

Fish rarely masticate their food. Their jaws,
preoccupied with breathing, can only momentarily
hold and bolt it; and since plants above all other
aliments need grinding, they form the least. desirable
choice. Hence it is that the oily rowing-shrimp
becomes the mackerel’s bonne bouche and the favourite

Fic. 16.--The mode in which a Starfish opens and eats an Oyster.
A. The Starfish gathered over its prey. 3B. Section to showj the
position of the sucker-feet on the valves. c. The long stomach of
the Starfish absorbing the Oyster through the open valves.—(<dA/ter
Schemenz. Permission to use granted by Prefessori\fenking, Berlin.)

G2

84 ANIMAL LIFE

titbit of the herring, in pursuit of which these
- migratory fish travel in bands from sea to sea
with an avidity that is never surfeited. In like
manner, though with the help of a vast baleen sieve,
the right-whales thin out the stream of minute animal
life that sets from the Arctic to the temperate zone.
Should the sea fail, as it does in winter, to break out
into this dance of drifting life, the active swimmers
retire to the bottom or deeper water, where they
discover an abundance of food in the vegetarian
Crustacea and molluscs, in the oily eggs of the herring
and the newly hatched fry of the plaice and cod. Let
but a shrimp stir a tentacle and the hungry dab seizes
him. The John Dory stalks the swimming shrimp,
going forward with his flat body edgewise and unseen,
and at last lunging out with his sucking, extensible
jaws. The dogfish, no longer sustained by nourishing
herring, bolts crabs and whelks to satisfy his raging
hunger.

Marine invertebrate life teaches the same con-
clusion. Cuttlefish, masters of marine invertebrates,
are the most active swimmers it produces, and
dart in vast shoals through the water, first in one
direction, and then in a tangential track, forwards
and backwards with equal facility. In shape and
movement they resemble fish. To supply the de-
mands for such energy the scanty alge of the mid-
ocean are inadequate and a richer diet is requisite.
This the squid, as they are called, find in the herring
and mackerel. They follow the migratory shoals

THE FOOD OF CUTTLEFISH 85

with an energy that sometimes sends them leaping
high out of the water. Pouncing upon a fish, the squid
opens a circlet of arms till then kept close like the
ribs of an umbrella, and with these and the two long
tentacles which can be shot out from their cases on
either side of the head, it grasps its prey. Its hold is
rendered secure by the suckers and hooks that stud
the tips of the tentacles and the whole length of the
arms. Then, bringing the fish up to the mouth and
horny beak, it rasps off the flesh by the horny tongue
that is the common heritage of all molluscs. So great
is the strength which these fringe-finned squid obtain
from their food that we have no engines quick enough
to catch the larger kinds, and it is only as storm-
tossed corpses that we know of monsters with arms
as thick as one’s thigh and suckers as big as saucers.
Yet, great as they are, there is one still mightier, the
epitome of the hungry life of the high seas. This
is the sperm-whale, which sculls almost at destroyer
rate, thrashing the water into foam. Of his seventy
feet of length, thirty feet is sheer head and jaws, and
with these he despatches the colossal squid ; and it is
from the interior of sperm-whales that we have found
out what manner of cuttlefish are roaming through
the ocean unseen and unsuspected.

Sea birds also are carnivorous. Their activity, the
maintenance of their bodily warmth, no less than the
feeding of their young, demand more nourishment
than the watery seaweeds can furnish. The year
round gulls haunt the coast for any flesh diet that the

86 ANIMAL LIFE

sea affords. They herald the,shoals of migratory fish
and the advent of their fry ; some decimate the cockle-
beds. From the far north to Australia wading birds
forage along the coast, and find in sand-worms, mol-
luscs, and sand-hoppers a never-failing food-supply.
On our rocky coasts, from April to July, the puffin,

the guillemot, and other spring migrants of the sea

—* ‘di { kun

Fic. 17.—The Black-headed Gull, Nest, and Young.
(From specimens in the Manchester Museuni.)

have made the rocks musical with their chorus,
fishing the day through, and disappearing in late
summer as mysteriously as they came. With autumn
the stream of southward-going shore birds take their
place, and in the hardest winter flocks more dense
than those of spring cover the sand flats, and find
abundant nourishment on the inexhaustible shore.

THE PREY OF LAND-ANIMALS 8

The quest for prey: II. Adaptations of land
antmals.—On land the problem of maintenance is more
complex. The extent of pasture is greatly increased ;
plant sheddings and mould correspondingly denser.
The supply of vegetal life is beyond computation,
and if animals dominate the sea, plants characterise
the land.

On the other hand, there are no fixed encrusting
animals—no barnacles, sponges, zoophytes or bivalves—
whose families can swell the drift life of air. Food
must be sought mainly on the ground, and has to be
actively gathered by movement in which the weight
as well as the resistance of the body has to be overcome.
This added strain increases the need for nourishment
which the pursuit of food seeks to satisfy, and as the
climate is no longer one of great uniformity, such as
that of the sea or large inland waters, the hardships
of heat and cold aggravate those of hunger. More-
over, plant-life also protects itself by thick coatings
against the inclement effects of drought and frost,
of excessive moisture and dryness. The result of this
is to render such food very difficult of mastication.

How widespread this difficulty has been and still
remains we realise but slowly. We think with facility
of plants as food for animals, and we overlook the
fact that whilst such is the rule, exceptions meet us
on every hand. The abundant mosses are scarcely
touched by a single animal, though no form of shelter
is more popular than their crevices. The ferns uncoil
their fronds in undiminished numbers every summer,

88 ANIMAL LIFE

and when autumn comes the roll-call is complete, for
there is no plant more secure from animal interference.
The lycopods, the mare’s tail, and the vast host which
form the vascular cryptogams are passed by and
avoided. But when we come to the primitive seed-
bearing plants—the pines, the cycads—we find primitive
insects, a sawfly, a few wood-borers, squirrels, and a
few birds capable of obtaining nourishment from them.
It is mainly the flowering plants at the top and the
fungi at the bottom of the plant kingdom which
constitute the supplies of vegetable food of which
animals can avail themselves. And neither by birth
nor adaptation have all land animals the taste or
the capacity for the requisite work of getting at
that nourishment and assimilating it. How an
alternative diet—that of flesh—has been maintained or
adopted by so many terrestrial animals we may now
consider.

By three paths land animals have become car-
nivorous. We have seen that the primitive air-breath-
ing animals—e.g., Orchesella (fig. 12)—fed on moulds
and lichens, which are found everywhere. From
moulds, and especially from fungi, it is but a short
step to a flesh diet. In the second place, we saw that
piercing and sucking organs were developed as the
higher insects discovered the sap or honey of flowering
plants, and found that for flight such a diet was emi-
nently suitable. For such creatures the transition
to parasitism on either plant or animal, or to the habit
of sucking the juices of active prey, was an easy one.

THE FOOD OF INSECTS 89

Lastly, in the higher animals the appetite for a flesh
diet acquired in the sea persists after the change to
fresh water, and thence to land, has been accomplished,
and it is only as the result of a happy and complex
combination—good grinders and strong digestion—that
the power of assimilating sufficient vegetable food
has been acquired by the Herbivora. We may now
consider how these habits have conduced to the
welfare of land animals.

Insects show well the strain of life. The most
primitive are feeders on moulds and lichens ; the most
degraded are parasites—fixed sucking animals; the
most highly organised are pre-eminently active sucking
creatures.

As the tiger is a lord among mammals, so is the
tiger-beetle among the huge tribe which his name
heads ; and no more ferocious, active, or bloodthirsty
beetle exists. From his youth up the two curved
jaws that signalise his ferocity are in constant employ
in attack, as he beats up and down hot roads and sandy
commons, quartering the ground in arrowy darts
from fly to fly.

The dragon-fly is an equally dominant member
of its tribe, and in brilliancy, power of flight, and
rapacity is perhaps supreme amongst insects. Sup-
ported throughout life on a flesh diet, it represents to
many another fly the long arm of circumstance. The
dragon-fly attacks its prey with equal celerity on the
ground or in the air, and, as it possesses both excellent
sight and flexible lips and a strong pair of jaws, it is

go ANIMAL LIFE

able to secure the prey by their aid, and then holds it
in the basket formed by its feet. Again, the Emperor
butterfly and hawk-moth are severally at the head of
these two groups, and are fine examples of insects
adapted for sucking flowers; and to satisfy its thirst
the Emperor descends from the tree-top for a puddle
or some dead creature. The mantis is the most
elaborate of the class to which it belongs, and though
maintaining a still attitude, waits but for a fly to alight
near to display the ferocity and blood-sucking in-
stinct that animates it. Even the grasshoppers,
that haunt sandhills and match the colour of their
surroundings so closely, feed upon the flies that perch
unsuspectingly near them. The true flies specialise
in sucking, and for the delicate probe that can pierce
a tough land plant the hide of a beast is no impene-
trable armour. Drawn by the sense of smell from
plants to fungi, from fungi to dead animals, and thence
to living ones, various families of flies have discovered
the stimulant of blood. The mother-fly in particular,
having but a summer to work in, discovers the greater
fertility which such a diet ensures and the greater
number of broods which may be reared when warm-
blooded animals are drawn upon for nourishment.
Ants, bees, and wasps, the highest members of that
vast class, the Hymenoptera, employ the most varied
methods for obtaining nutritive fluids. Plant or
animal juices in a concentrated form are their
favourite nourishment. Ants milk their cows—the
aphides—from whose bodies flows the nectar or honey-

¢

Fig. 18.—Tongue of House-fly. Left side of head removed to show
internal structure. The empty space is filled with air-sacs not shown
in the figure.—(W2zth C. Gordon Hewitl’s permission, The University,
Manchester.)

Pi., eversible ‘ frontal sac’; /c., fat-cells ; C.G., s.0., brain; P.O., portion of brain
supplying nerves to compound eyes ; @v.7., oc.m., nerves to antennz and simple eyes ;
ph.n., lb.m., nerves to suction pump and proboscis; ~4., 4A., 7.7., %/-, muscles for
retraction (or withdrawal) of proboscis ; 7.fu., 7.ds., con.¢., muscles opening mouth and
controlling the flow of fluid along the ‘throat’; af%., £x.h., muscles controlling the
bending and unbending of the proboscis ; af., rod concerned in the same process;
¥F., sheath of ‘suction pump,’ with its processes a.c., ~.c. ; d.fm., muscles working
‘suction pump’; 4, sheath keeping open beginning of ‘throat’; oes., ‘throat’;
Z.ef., upper lip; ¢%., lower lip, also formed by parc of Z2f., d.s., and 7 skeletal
structures of the oral lobes, one of which is shown; /s., channels, and g#., * taste pits,’
of the oral lobe ; 24.s7., one of the two saliva glands of the oral lobes ; sa/.a., duct of
large saliva gland, with ts valve, s.v., and muscles, s.#., controlling the same;
mxp., maxillary palp.

-

92 ANIMAL LIFE

dew which they laboriously secrete. Bees so much
prefer the dew to the trouble of securing honey that
in some years hives are a failure. Wasps both sop
up fruit juice and devour other insects, killing them
with a sting and storing them in their burrows.

The higher Arachnids, the spiders and scorpions,
contrast with their degenerate allies, the mites and
ticks, by their large brain and complex structure, which
bear witness to their high place among invertebrates ;
and this conclusion is borne out by their nourishment
and the means they adopt in obtaining it. If to feed
by sucking the juices of a captured organism is a sign
of superiority, spiders and scorpions are sure of a high
place, for their methods show exquisite adaptation to
secure this end.

So exclusively is the whole class of Arachnids
a race of sucking animals, that it has lost the jaws
which all but the most modified insects retain. In their
place these animals possess a pair of small sharp
nippers, within which lies a poison-bag, so that every
nip injects some venom into the prey. The second
pair of limbs is usually leg-like, but in spiders it so
far differs from the four remaining pairs of legs that
its base is expanded to form a jaw-like process which
helps to hold, though not to chew, the food. In the
scorpion the second limbs form a pair of claws, and
in the mites a sheath, within which the first pair or
piercing organs can be held. The act of sucking is
performed not through a proboscis as in insects; the
tiny mouth is applied direct to a wound in the prey,

SPIDERS 93

and its juices are sucked by the alternate expansion
and contraction of the throat. By this means mites,
red spiders, and ticks devastate our currant-bushes
and hop-plantations, destroy cheese, books, and fur-
niture, become blood-suckers of man and most ter-
restrial animals, and in tropical countries are one of the

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ac

Ke eS \\\

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WD ——_
bs

A\

- ee
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SS

SS

aN,
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RS

= was
ah
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Fic. 19.—Wheel-web of the Garden Spider. —( After Blanchard. )

means whereby such diseases as relapsing fever are
transmitted. Spiders are one of the dominant races
of animals, and in hunting instincts excel all others.
Their power of constructing webs, underground traps,
and even sub-aquatic snares, is well known, but the
variety of traps and the ways in which these snares

94 ANIMAL LIFE

are formed and concealed and managed are scarcely
appreciated. |

The web of the garden spider is essentially the
work of the mother. It is she who constructs it,
she who watches it and feels the pulse of its lines
from her hiding-place. When a mote is blown into
the web it is the mother who sallies forth to remove
it. When a fly is entangled it is she who emerges
and, enveloping the struggling prey with more silk,
retires to enjoy the feast. Her mate is but a casual
incident, whose presence is tolerated for a time, but
soon forgotten in the stress of capture and the care
of young. In times of unusual hunger he may even
be devoured.

The web of spiders is unique. There is but one
other example of a net stretched out to catch prey,
and that is the seine-net of a caddis-fly larva, into
which river-borne flotsam drifts and is devoured by
the watcher (see p. 237).. But spiders are the only
animals which have found a means of intercepting the
humming life of the air.

The silk of which it is spun is the finest and
strongest natural product. In itself it is no new thing.
A gum which, when drawn out to a fine thread forms
silk, is produced by a gland opening into the mouth
of most caterpillars, of which the silkworm is but
one. That which distinguishes a spider’s silk is its
variety. One kind of silk is used for the outer frame-
work and the radial lines, a second for the circular
lines, a third for the enwrapping of prey, and a fourth

SPIDERS’ WEBS 95

for the construction of the cocoon. Each sort of
silk is made by a collection of glands that open near
the end of the body by a little spout called the spin-
neret. The lines of a geometrical web are laid
down in the following way. First an outline is
drawn ; to form this the female shoots out the
requisite thread, fastens it to some support, carries
it in her hind feet, streaming out of the spinneret and

Fic. 20.—Web and Nest of Agelena, spread on : grass.—(‘ Riverside
Natural History,’ by permission of Messrs. Houghton, Mifflin & Co.,
Boston, U.S.A.)

hardening as it emerges. Presently it touches a twig
or leaf, to which the spider fastens it and stretches it
tight with her claws. Then, letting herself straight
down and drawing out the silk behind her, she forms
one of the vertical sides. Afterwards the other sides are
completed in the same fashion. Across this framework
the spider draws a thread, fastens it with her claws,
and tightens it, so as to form the diagonals. From the
centre of this she travels to another point of the

96 ANIMAL LIFE

framework and draws the first radius, up which she
travels to the centre again, and by repetition of the
process the spokes of the wheel-shaped web are run
across from the centre to the circumference. Once

Fic. 21.—Nest of Age/eza made by the young on surface of furze.
(from a specimen in the Manchester Museum.)
more running to the centre, the spider constructs a
temporary spiral, the turns of which are looser as she
travels outwards. Finally the finished spiral lines are
spun of a second store of glands. These are more
sticky than the rest, and serve, of course, to entangle the

SPIDERS’ WEBS 97

prey. The temporary line or scaffolding is then cut
away.

The whole process of making a web takes about half
an hour, and after finishing it the spider retires. Her
object now is to keep in touch with the movements of
the web. This she does through her feet, which are
sensitive to the slightest vibration, and her complex
nervous system probably enables her ‘to interpret
each kind of vibration as
signifying a definite disturb-
ance. In response to the
tug she feels her action takes
several forms. It may be
that a gust of wind will
immediately destroy the web,
or that a large insect may
blunder into it. But in the
event of calm weather and no
accidents the advent of prey
may be, and no doubt is, Fic. 22.—Nest of Cave Spider

eagerly and confidently ex- = (4#eta menardi), to show the
way in which the eggs are
pected. Should a fly become me ashded be uk arid ean

entangled, the spider is at ported by a stalk.—(Fvom a
once aware. and adapts her specimen in the Manchester
‘ : ; P Museum.)

behaviour accordingly. She

evolves her stickiest silk, seizes the fly, and, running
round and round her prey, envelops it somewhat
as she spun the circular web lines. She now plunges
her poison-organs into the fly and proceeds to suck
its juices, thereafter casting out the skin and smoothing

H

98 ANIMAL LIFE

down the web. A butterfly is similarly treated ; but a
wasp is sometimes allowed to escape with the utmost
celerity by biting through the lines that bind it.

The variety of webs is great. There is the funnel-
shaped web, so common under stones and among
old walls, from which at the least touch out rushes
the artificer. This funnel plays upon the weakness
which so many insects have for investigating dark
corners and for seeing where tracks lead to. Other
spiders choose stations over water where gnats and
midges abound. The surface of meadows and heaths
are covered by flat webs, which in the frost of an early
autumn morning form an almost continuous gauzy
covering (fig. 21).

REFERENCES

The relation of insects to flowers : Lubbock, ‘ Nature Series.’
Macmillan.

Spiders: McCook, ‘American Spiders,’ Philadelphia ;
Romanes, ‘ Animal Intelligence,’ Inter. Sci. Series, vol. xli. :
Cambridge Natural History. Macmillan.

99

CHAPTER VI

THE BREATH OF LIFE

It is a faithful saying that we do not live on food alone.
Life is a fire, now slow, now fierce, and therefore needs
air as well as fuel. Changefulness is of the very
essence of being, and all our rest is but hidden activity.
Growth, movement, development—all the expenditure
of force, which are the shows of life—involve trans-
formation of our substance. We burn that others
may have light ; and just as the sparks fly upward
under a fire’s breath, so we and all beings need a fan
if the fires of life are to become active. Food is but
the laid fuel; oxygen, that which fans it. The fire
was lighted long ago. The twinkling flames hidden
in thought, patent in conduct, have come from the
vestal lights of other generations. Every moment
of restful or restless activity they maintain the trans-
formation of our bodies. We are renewed year by
year, and to make way for the new being the old
is slowly burnt away. We breathe out coal-gas, we
radiate warmth, our muscles work by innate explosion.
For every breakdown which is the necessary preface
to this constant renewal, oxygen is essential. We rise

on our dead selves only by their combustion. But so
H 2

100 ANIMAL LIFE

generous and ungrudging is the renewal, so serenely
is the new man made, that we forget that all balance
is complex adjustment and all progress hardly won.
We mark, not the loss that energy entails, but its sus-
tained and transforming activity. Artists by nature,
we rightly overlook the pains of effort. But if we
are to comprehend the working of that mysterious
life the activities of which arrest us, then we must
be possessed by the conception of the downfall which
precedes every uplifting in the transformation of living
tissues. The more thorough the burning, the more
complete will be the reconstruction, and health is as
dependent on the one as on the other. We rise
Phoenix-like out of our own ashes. As we obtain
explosion by confining the area and increasing the
rate of expanding activity, so a muscle gives out in one
convulsive movement a force which at other times is
spent in gentle and repeated efforts. But whether
gentle or explosive, muscular action is only sustained
by oxygen, and the more vigorous the effort, the greater
the demand.

As for muscles, so for other tissues. Our very
bones are constantly being renewed. Where the
seeming waste is greatest, there the new growth is most
active; and should this new growth beno reproduction
of the preceding part, but an addition or new develop-
ment, then it is subjected still more fiercely to the
alternate tides of waste and repair. Breakdown by
oxygenation, reconstruction by feeding, is the rule by
which we live and move and work out our being.

——

VARIETY OF VITAL ACTIVITY IOI

This strange instability, as of a fountain summit
or of a flame, is of the very essence of life and creates
the need for oxygen as well as the need for control.
If the demand or supply is small, the life will be
inactive ; if ample, vivacious ; if greater still; feverish.
At one end of life’s scale we have the latent life of
seeds, the suspended animation of winter sleepers ; at
the other the consummation of a Shelley. Between the
two we have the periodic sleep and growth of plants,
the gradual rise of animal activity in water, on land,
and in the air, and the final achievement of permanent
activity of body and mind.

Life, however, outruns our metaphors. In variety
of working, inwardness, and thrift it transcends our
figure of flame. Biological activity is not exhausted
by combustion. Muscle and nerve are most complex
tissues, and their inward changes are correspondingly
complex. Movement, whether of plant or animal, in-
volves a change of its electric tension which may be
too delicate for perception unless studied by a sensitive
electrometer, or so powerful (as in the torpedo or
electric eel) as to disable us. Nervous activity, again,
is akin to electric action. Even respiration is not
always the slow combustion we have described. A
molecular as well as a mass exchange of gases is known

in plants and animals. Leavening prepares for life.
; The inwardness no less than the variety of biological
action contrasts with our simple figure. A fire is an
affair of surface changes. Living things, on the other
hand, burn from within outwards. Fuel burns only

102 ANIMAL LIFE

in free oxygen. Plants and lowly animals possess a
disruptive faculty, by which they can in the absence of
free oxygen break up their store of carbonic gas and
set it free. From reserves in seed or muscle fresh
energy is obtained by this analytic action. Moreover,
in ordinary muscle-breathing the oxygen in the blood
is not directly used by the tissue, but is first stored,
controlled, and delivered subtly to the muscle, under
the pressure of that inward, invisible governor that
converts the breath of air into the breath of life.

Nor, again, is the contrast of economy in vital
actions with the waste of fuel a less conspicuous
feature of their work than variety or inwardness.
The best coal-motors are wasteful, and give out in the
desired form of work but one-eighth to one-ninth of the
energy imparted, the rest escaping by conduction, in-
complete combustion, and other wasteful outlets.
Beings are rather more productive and less wasteful.
A man given 0°44 kilos of food, representing a million
units of energy, gives out in a day, work estimated at
one-fifth to one-sixth of this. This economy, unequalled
in other carbon-combustions, is due to the central and
peripheral control of the nervous system playing upon
the fitful external supply, and is signalised in our
constant temperature, equable pulse, and regular
breathing.

The quest for oxygen : respiration and evolution.—
Water contains air, as we see by the bubbles that
rise on heating ; but the amount of oxygen is a mere
fraction of that contained in an equal volume of the

THE SUPPLY OF OXYGEN 103

atmosphere. There is at least twenty times as much
oxygen in a bottle of air as in the same quantity
of fresh or salt water. When we consider this, then
the fact that all the higher forms of life, plant and
animal, are aérial and the lower mainly aquatic becomes
more intelligible. The more complex frame of the
advanced classes of life demands more oxygen than
that of the simple, both on account of the speedier
rate at which their tissues disintegrate and re-form,
and also on account of the more rapid and laborious
work that their movements imply. The greater size
as well as complexity to which land plants and animals
attain is another reason for their more active respira-
tion. The spacious air and abounding waters provide
an unlimited store of the requisite oxygen. Unlike
the search for food, which is a quest beset with
difficulty and uncertainty, the breath of life is around
all that live upon the earth and bounteous beyond
computation. At the surface of the earth, or that of
the hills, its richness is greatest, and as we descend to
the waters its bounty diminishes. Above and below
the surface the amount of oxygen varies. If we climb
beyond the snow-line this change causes mountain-
sickness ; if we enter a cave our lights burn low. As
with the surface of the earthso with the surface waters.
The upper strata are rich in oxygen from wave-move-
ment and the imprisoned air of the foam; and this
bounty is reflected in the teeming life and comparatively
high development of its fauna ; below in the stillness
there is poverty of oxygen, only matched by the cave

104 ANIMAL LIFE

region; and yet where oxygen has diffused, the
darkness is peopled by hungry strays and waifs.
Whether in the earth or in the waters the highest forms
of each order come to the surface, the lowest are
submerged ; and emergence or submergence corre-
sponds to plenty or poverty of oxygen.

This air we breathe has only been reached by
epochs of struggle and new departures. The possession
of the earth is hardly won. Before the nimble air
gave strength and impetus to the conquerors they
had to pass the marsh and shore on their landward
way. Plants and animals alike have striven for the
face of the waters, for the beach, for the marshes, and
finally for the air. Man himself carries in his ears
an unmistakable sign of his gill-breathing, watery
past, and of the depths he has left behind him. Evolu-
tion follows the successful quest for oxygen, and there-
fore earth has been peopled by the highest communities.
The ancient stocks are scattered, some keeping to the
beach, some lurking in dens and caves, or, as parasites
and messmates, hiding away, degenerate and prolific ;
some, such as whales, returning to the waters, where
they maintain an unfair supremacy over the uneman-
cipated fish. Refugees from the shore and from the
surface of the water retire to the depths, and there,
at oases in the general desolation, hang out their
phosphorescent signal lights.

Evolution of the respiratory methods of animals.—The
drama needs elaboration. Its climax—the possession
of lungs and of a good circulation—comes last in the

EVOLUTION OF BREATHING HABITS 105

history of every group that has attained supremacy.
The earlier acts are done under water.

The simplest animals, so-called Protozoa, are
all characteristically aquatic. They either live freely
in water, or in a water-bath which some animal or
plant provides for them. Furnished with oars or
‘cilia ’ they pursue and engulf their prey ; or, if station-
ary, draw in liquid instead of being drawn through it.
Thus both inside and outside they are bathed by
constantly changing water; and from one or both
of these sources they extract the minimal quantity
of oxygen which is dissolved in such water, and it
suffices them. By its aid, movement is maintained,
the food broken down, and the living substance, after
rebuilding and replenishing itself out of that food, is
disintegrated as the first step in another cycle of life.
Neither lungs nor gills are distinguishable. There is
no‘ blood to carry oxygen or to remove carbonic acid.
The protozoon is a gill and heart in effect, though
not in fact. It does with its seemingly simple tools
all that taxes the complicated structure of a higher
animal to accomplish in breathing, namely, to abstract
oxygen from the air dissolved in the water, to convey —
that oxygen whither it is needed, to use the store
without exhausting it, and after use to carry away the
ashes and smoke of the fire.

Sponges, corals, and anemones are animals whose
bodies are channelled out for the passage of water.
These creatures irrigate their bodies by a stream that
passes in through one or more openings, then through

106 ANIMAL LIFE

a sieve on which the food is collected, and finally out
again by the same or a different path. This constant
irrigation carries water within the reach of the various
tissues, so that without any blood-vessels they are yet
able to derive oxygen from the stream, and to empty
into it the débris of that slow combustion that water
cannot quench. This removal of the ashes of com-
bustion is largely assisted by the activity of minute
plants that infect and colour the coral and anemone.

But growth, as well as breathing, depends on the
supply of oxygen, and as these inert animals grow
freely instead of moving actively, they utilise the
bounty of the surf for the spread of their colonies.
Sponges cover the rocks of our coasts, and each
of these, if cut into a hundred pieces, will grow
into a hundred sponges as large as the first. Ane-
mones coat our shores and will propagate, as well
as sponges, by cuttings. Corals form barriers and
reefs miles in extent, and build up island and mountain
by the growth of succeeding generations. Nor is their
life a short one. A sea-anemone lives twenty-five
years, and may live to over fifty, and corals are of
equal longevity.

This long-continued growth implies a rich supply
of oxygen; and in two different ways these fixed
animals gain a better supply than that which still
water contains. First they colonise the region of
surf. Sea-water when shaken up with air increases
the amount of its oxygen many fold, and from the sur-
face down to a depth of some twenty feet the amount

BREATHING AND GROWTH _ 107

is considerably greater than in the stiller depths.
The influence of this fact upon the growth of sea-
animals is continually brought home to us. Life and
foam are old associates. The region of greatest
animal growth is just where the water is most sparkling.
So long as the swell is not so heavy as to tear and grind
all that is not solid rock it will foster growth. ‘ Full
fathom five’ is the depth down to which most
corals flourish, sponges cover the rocks, and anemones
afforest the coast. Where the tide runs strongest,
there will be the richest growth, and that not only be-
cause it brings new food with every flood, but because
it carries fresh supplies of oxygen.

The second method that these long-shore encrusting
animals adopt to gain more oxygen is to increase
their capacity for holding it. The red colour of
our blood has exactly that meaning, and as its tone
waxes and wanes so does our energy; and for this
reason, that the red pigment has a strong affinity for
oxygen, binding it to itself, and in so doing deepening
in tone. When richin oxygen its colour is bright
and vitality great; when poor in oxygen the colour
fades and the body grows faint. The sponges and their
allies give us a first hint as to the origin of these
respiratory pigments, for we find them of the most
varied tints, but chiefly red, yellow, and green. These
colours which, if we ever notice, we think of merely
as decorative effects, possess a value to these animals
which decides not life—for these tough primeval
beings hold to life at many points and defy a sudden

108 ANIMAL LIFE

taking off—but, what is of greater significance, their
increased vitality and productiveness. Needing but
little oxygen for their own consumption, they are able
to utilise any small surplus. with great advantage,
as in growth; and it is probably this help that
colour gives them. These reds and yellows, more
than the uncoloured parts, on this view, seize the
passing oxygen, store and then dispense it to the
tissues.

The respiratory adaptations of Crustacea and
Molluscs.—Among higher and more active creatures the
demand for oxygen is more insistent, and the irrigation
system becomes limited to particular regions, over which
a stream of water flows in and out. These regions—
the gills—are thin-walled folds of skin, within which
there flows a fluid which is no longer water, but blood,
thicker than water. Its channels lead to and away
from the gills, and the streams that fill them course
past the gill-walls, as they circulate. The sea-worms
bear a tuft of gill-plumes on every segment, and each
of the simpler sea-shrimps and pond-shrimps carries
a plume on its thigh. The very effort of movement
shakes the gill, brings it to fresh bodies of water,
and stimulates the circulation. The movements of
such creatures help to create the supply of oxygen
which they demand, and if food were easy to come
at and enemies few, there might be no need for
more elaboration than gill-plumes and gill-circulation.
Such, however, is notoriously not the case, and we
find in each kingdom—that of the worm and that of the

ee = _

Fic, 23.—Brine-Shrimp (Branchipus), a primitive Crustacean found in
salterns in the south of England. The gills are fixed on the bases of
the swimming-legs.—(/vom Lang’s ‘ Comparative Anatomy.’) x 20.

@,, first antenne; @,, the large second antenne ; wa, unpaired eye; 4, liver;

mad, mandible; ,sd, kidney; #, heart; of, openings of heart; 4, male organ;
or, gills.

IIo ANIMAL LIFE

shrimp—a variety of breathing devices adequate to
the different demands of its members.

To meet these varied exigencies two methods have
been elaborated with great detail. First, the con-
struction of a channel along which the oxygen-holding
water is made to flow, and, second, an increase in the
oxygen-holding power of the blood.

The first of these methods is the secret of the
greater advance that the shrimp family has made
over that of the worm, and it is also the motive under-
lying the formation of the shells of the molluscs. The
buckler of a shrimp, lobster, or crab, the valves of a
mussel, are tubes confining the respiratory current
to a comparatively narrow area in which the gills lie,
and thereby increasing the rate at which the water
can be drawn over them. The second of these methods
is largely effected by pigment. Our blood we know
needs iron to keep it healthy, and it is a fact that gives
us new affinity with lower animals that in them also
the same ferruginous red blood is found. It occurs
in those which have to live where oxygen is scarce
or in parts of the body where muscular action is most
sustained. Elsewhere we find a copper salt taking the
place of the iron one, giving with oxygen not a red
but a blue tint, and possessing only a quarter of the
oxygen-holding power that belongs to hzmoglobin,
its iron relative. Finally, in the less exigent forms the
blood is hardly more than a stream of watery albumen.

The working of the first method is easily tested.
If some powdered carmine or indian ink is placed

DAPHNIA III

just behind the last leg of a crayfish at rest in a dish
of water, a series of puffs of the colouring matter will

Fic. 24.—Daphnia, an abundant freshwater Crustacean ; the body is
enclosed in a carapace ; the limbs, less numerous than those of the Brine-
shrimp, carry gills.—(7vom Lang’s ‘ Comparative Anatomy.’) x 50.

@,, first antennz ; @,, second (rowing) antennz ; a4, abdomen ; ax, eye ; 47, branchial
sac ; bru, brood cavity ; d, intestine; 7, to _/,, trunk feet ; g, brain; 4, heart ; Z, liver;
sd, shell gland.

issue in a few moments from beneath the eyes of the
creature; and if we seize it and examine the under

112 ANIMAL LIFE

surface of the head, a rapid movement may be observed
at the sides of the mouth, indicating the position of the
bailer ; the gills are, in fact, enclosed in sucha way that
the space around them is converted into a tube, open
in front and behind.

In a burrowing animal, however, such a method
entails the danger of sucking up débris and choking

Fic. 25.—Head and thorax of Crayfish, to show the gills and the bailer, ¢f,.
(From Lang’s ‘ Comparative Anatomy.’)

@,, a, antennz ; aé,, ab,, abdominal segments ; £/d,,, db,., Pdb,, gills ; A/,, first
swimmeret ; 5-13, thoracic appendages.

the gills. Accordingly we find among burrowing
crabs a great variety of devices which, while per-
mitting them to escape their numerous foes—the
larger fish—allows them to maintain an in- and out-
going current without blocking the gills. The common
crab, which sinks up to the eyes in soft sand at the
slightest warning, has a reversible gill-current. In
general, it draws water through an opening at the

BREATHING OF BIVALVES II3

base of the foot-jaws and exhales it beneath the
eyes. When sunk in sand it performs the opposite
movement, and drives the water out at the opening
through which it had previously inhaled it. The
masked crab, which burrows deeply into the sand,
possesses a special breathing tube, through which it
can inhale fresh draughts of water. Its antenne are
brought together by interlocking hairs, so producing
the tube, and the water then passes backward over the
gills and out amongst the feet (fig. 19, F).

The burrowing bivalves—razor-shells, rainbow-
shells, cockles, and the like—provide themselves with
a breathing siphon. To escape their numerous enemies
and to evade the digging action of the sea, that threatens
to evict and pulverise them, they possess a flattened
shell, which easily passes through the sand as the
spade-like foot hauls them into the burrow. But
without some means of breathing surface-water these
animals would be speedily choked, and their delicate
gills lacerated by the flinty particles around them.
Accordingly we find they have developed a long,
bent siphon, the original fringe of their double tube
drawn out to twice the length of the animal. Through
this double tube the bivalves can reach up to the
surface-water and tap a supply unmixed with sand.
The current runs down one tube, bathes the delicate
plate-like gills, and after passing through the body rises
again to the surface, where, toavoid contaminating the
supply, the outlet tube is turned away. When alarmed
the animal withdraws its tubes into the shell, in which

I

II4 ANIMAL LIFE

they lie till the disturbance has passed away. Their
presence has impressed a line inside the shell, so
that in place of a mark running parallel with its

Tn =e ae Tip said, Tua. aad waa Sis a ae cine, a a a ar
‘4 pe %
rae 2 "papi ,*o
] * hd
* 4

’ -
Aa : -
are
% xis

¥

; : : ; = om ; es hae =) a
Fic, 26.—A group of Burrowing Animals from a sandy shore. a. The

Heart-urchin, showing its tube feet gathering food. xB. A Bivalve

(.Scrobicularia), showing the inlet (4) for water and food and the outlet

(a). c. The Cockle, showing inhalent and exhalent tubes. pb. The

Mud-clam (J/ya), showing the same. E. The Lugworm., F. The

Masked Crab, whose antennz form the inhalent tube.—(B-p from

Messrs. Meyer and Mobius ; A, after Graber ; E, ¥, original.)

BREATHING OF SNAILS II5

edge, the border of the contracted siphons forms a
bay, and by it the bivalves with long siphons may
be distinguished when we have only the shell to
guide us.

The univalves, or snails, have more varied breath-
ing organs. The majority of sea-snails carry a tube,
trunk-like, in front of their head, as they creep over
the shallows at low tide, and by this trunk they inhale
water which, after travelling over the gill hid within
the shell, goes out by a slit near the base of the trunk.
To support the trunk the snail-shell has a groove or
spout, and by it the presence of the breathing-tube
may be known even from the shell alone. Other sea-
snails have no such canal, but are, as it were, snub-
nosed, the nostrils being separated into an in-letting
and an out-letting one. A few, such as the ear-shell
and the key-hole limpets, have a slit, a row of holes, or
a single hole, through which the water makes its escape
after bathing the gills.

Cuttlefish, squid, and nautilus have a short funnel,
or escape pipe, for the same purpose, and in them the
effort of breathing is convulsive; the whole body
shakes with the effort and twists its gaping orifices
as it unceasingly sucks in and transmits the gulps of
water that flood its gills. The size, activity, and
growth of these fierce creatures demand larger quan-
tities of oxygen than are needed by other snails, and
as the blood courses through their gills, it changes
from a colourless to a blue fluid, a sign of the presence
of that coppery blood-pigment which holds oxygen

12

116 ANIMAL LIFE

with a capacity only exceeded by the red iron pig-
ment which we possess.

In each of these tribes—those of the: worm and of the
shrimp and snail—we find many air-breathers. There
are earthworms and land leeches, land crabs and
wood lice, land snails and land slugs. That these
are descended from aquatic ancestors is shown in
their dependence upon moisture. A worm shrivels
by heat and is killed by frost. Its delicate netted
skin is a gill that can withstand neither extremity of
climate to which aérial life exposes it. Hence the
tropics with their damp undergrowth, and the deeper
soil with its more tenacious moisture, are the chief
resorts of these adaptive air-breathers, for it is in
such places that perennial damp is secured.

The breathing of vertebrates. Gill-, lung-, and votce-
production.—Fish differ from all animals except the
zoophytes in their mode of breathing. By a succession
of swallowing movements that suffer little interrup-
tion, a fish fills its mouth with water, then closes it
tightly, and by compressing its throat and gullet
drives the water out through its gill-slits. The
margins of the slits are converted into tasselled fringes,
and the muscles used in swallowing are so arranged
as alternately to open and shut these side exits. The
gills of a fish consist of these bundles of red tassels
mounted on hoops. Each thread of the tassel contains
a V-shaped blood-vessel, one limb of which comes
from the heart, whilst the other goes to the body.
The red colour is evidence that only a thin skin inter-

BREATHING OF FISH EL?

venes between the blood in the gills and the water
which bathes them in a series of successive outgoing
spurts. Through this transparent covering the oxygen
of the water diffuses into the blood, which, thus
invigorated, is carried to the various organs of the
body.

Where the activity of the organs is great the
storage of needful oxygen is increased by the develop-
ment of a red pigment capable of forming a reserve
fund, upon which the muscles may draw for the in-
creasing work that is demanded by the ceaseless
adjustment of the body and by the rapid, powerful
strokes required. for pursuit, escape, or migration.
The pink colour of salmon-trout and the red of the
salmon and of the tunny are stores of this kind.

This constant irrigation of the gills has brought
fish into intimate touch with the qualities of water.
The gradual drying of watercourses and ponds in
summer, or the fouling of water by the decay of
vegetation, reduces the amount of available oxygen,
and to avoid the threatening suffocation many fish
have adopted the plan of swallowing not water only,
but air as well. The common loach rises to the surface
to gulp a mouthful of air. The mudfish of Africa
and of America does the same. The advantage of
such a plan is patent. When the water is pure and
abundant, aérial oxygen is a luxury, but when, in
dry weather, the stream becomes a few isolated warm
pools, which decaying weeds are rendering each day
less fit for breathing, then those fish which can

118 ANIMAL LIFE

breathe air are able to hold out longer than their
submerged fellows, and, should the next rain be too
long delayed, they will be first to meet the spate and to
secure the new supplies of food that the flood carries.

In order to store the air which gives them such
advantage the throat of fish is puckered up into
pouches ; some of these are quite shallow pockets,
some are long tubes running down the body. In
virtue of this supply the climbing perch makes ex-
cursions overland before the dew is off the grass, and
. the mudfish, which tenants every sheet of water in
equatorial Africa, passes through the driest season
with impunity, rolled up and sleeping.

The demand for storage of gases is so insistent
that we find it obeyed by almost all fish, even in
those which breathe solely under water. In them the
storing organ is a tube lying under the backbone and
opening into the throat during the first part or the whole
of life. Into this chamber gas is exhaled from the
blood. In marine fish oxygen is chiefly stored; in
freshwater fish nitrogen preponderates. . But these
gas chambers, which originally no doubt served as
reservoirs of respirable gas, have lost their primary
function, as, indeed, the neutral nitrogen implies, and
become transformed in ordinary fish into bladders,
which determine their specific gravity by the alterably
greater or less quantity of their contents. Thus they
have entered into the problem of movement, and,
by tending to lighten the fish’s back and upset its
equilibrium, have led to far-reaching demands upon

ORIGIN OF LUNGS 119

the fins and the muscular control of balance. Finally,
in a few catfish the gas chamber becomes connected
to the ear by a chain of little bones, in virtue of which
the perception of vibrations in the water is notably
enhanced. |

From some such appendages of the pharynx our
lungs are derived. Fish of different orders have
independently converted an outgrowth used at first
for temporary air-storage into a sac, round the walls
of which blood could be re-oxygenated and purified
of its carbon dioxide. The opening of this virtual
lung is even converted, in some fish, into a glottis or
voice-organ analogous to our own larynx ; and in the
so-called salmon (Cevatodus) of Queensland, once wide
spread over the northern hemisphere, the organ may
be spoken of as a pair of lungs, which exist side by side
with the gills ; it occupies the position and plays the
part of the lungs in ourselves, and, whilst useful at
all times, becomes of special respiratory value in foul
water or times of drought.

* The next stage in the evolution of our breathing
organs is traceable in the amphibious newts and frogs.
These have gills when young ; a little older they possess
both gills and lungs; and in their adult stage lose
their gills and breathe mainly by lungs, reverting
at times of stress and subaqueous retirement to the
oldest known method of supplementing respiration,
namely, breathing through the skin. This power of
respiring air directly is associated with the conquest
of the land. As it is done through the nose, we find

120 ANIMAL LIFE

the air passage emancipated from the food passage.
The reptiles exhibit a more complete solution of the
air-breathing problem. In this, as in all their other
faculties, we find amongst them a vast range of medio-
crity. Most reptiles are only partially adapted for life
on land; many at regular periods pass into a trance
during which they respire mainly by the stores of
air which their lungs have previously accumulated.
In the reptiles we find the last traces of that primeval
animal capacity for surface or skin breathing ; of true
gills nothing but the framework remains. But in none
of the known groups of this immense class do we find
other than simple bag-like lungs, or a larynx capable
of modulated sound. In none of them at the present
day is the heat produced in respiration so controlled
as to ensure a continuously periodic high vitality.

From some unknown members of this mediocre
class. two. offshoots have sprung in which the
faculties of breathing amply, of sustained activity,
and of voice production, have been perfected. Among
birds we trace the evolution of the most perfect
lungs that are known ; of the most continuously active
of beings; of the most indefatigable of songsters.
Amongst mammals we can follow the elaboration of
a less aérial type of breathing; but, in accordance
with their closer touch with the ground and the
acquisition of great size, we find in them a means of
inspiring and purifying great tides of air, an immense
store of latent energy, and the most varied powers of
voice and speech.

BREATHING OF BIRDS 121

The working out of these capacities in each group
is a problem of great interest. In birds the lungs are
small, the windpipe long, and the organ of voice
at its end, not in the throat at its commencement.
Birds, therefore, are ventriloquists. From their lungs
spring a number of air-sacs which buoy up the viscera
as on cushions, line the skin, and often penetrate the
very bones and feathers. To inflate this system a
dual mechanism is provided. When stationary, the
bird may raise and lower its ribs; when flying stiff-
breasted, it lifts and depresses its flexible back. In
either case two results follow. Compression involves
not only expulsion of air from the lungs, but from
the air-sacs through the lungs. Expansion entails
an inrush through the lungs into the air-sacs. Thus
the air in the lungs is wholly tidal. The expiration of
combustion gas and the inspiration of fresh air are
thoroughly carried out, in which processes the function
of the air-sacs is not to act as respiratory organs
directly, but to subserve this ventilation of the lungs
by increasing the inward and outward wash of air and
carbonic acid. |

This rapid rushing breathing stirs the blood.
The muscles, fanned as by a draught, precipitate
their activity in a series of superbly adjusted move-
ments. The tissues burn well. Fuel has to be con-
tinuously supplied. Food is imperiously needful,
and the unappeasable, proverbial appetite of a bird
becomes intelligible to us. Heat, too, increases. The
feathers check its radiation and conduction. A nervous

122 ANIMAL LIFE

control governs its uniformity, and there results a
higher temperature than any we can healthily evolve,
and one that for the first time in our résumé of living
beings is unaffected by that of its surroundings. A
hen’s temperature is uniformly 103 degrees Fahrenheit ;
a swallow’s, 106 degrees.

The production of voice is partly voluntary, partly
mechanical. The adjustment of the slit just above
the lungs and the rate of vibrating its edges are modi-
fiable muscular actions. The call note, the migration
note, the mating song, the alarm note, and the mimicry
of parrots and song-birds are controllable responses
to an impulse or an audible voice. But the ordinary
breathing movement, which underlies it all, has become
part of that unreasoning mechanism over whose
starting or finishing birds have no voluntary control.
The combination of superb singing powers with high
vitality and spacious breathing marks the bird.

In the mammals the lungs are capacious; but the
amount of really tidal air is a mere fraction of the
whole, and forms a top layer, from which the great
mass that is stationary gains its oxygen, and into
which it diffuses its carbonic acid. Thus, between
the lungs and the tidal air is a diffusion-chamber.
Every beast and child fills this with its first breath
and never breathes as deeply again.

Movements of the lungs are those of enlargement
and diminution. Both of these are effected by the
chest and by the diaphragm, a device peculiar to
mammals. Both take place through the nose, as in all

BREATHING OF MAMMALS 123

lung-breathing animals save unheeding men ; and to
purify the air, which for ground animals, such as
mammals are wont to be, is too harsh or spore-laden
for immediate diffusion in the lungs, this nose is
elaborated within and without. Its chambers are
subdivided by a scroll-work partition that converts
them into labyrinths. Inspiration through such tubes
now becomes more effective at the outset ; and as the
wash of air whisks round the corners it deposits some
of its impurities on to the soft membrane that lines
them, and from the middle part of the nasal passage
the air, toned, purified, and warmed, goes to the
diffusion-chamber.

The maintenance of activity in mammals, though
less impressive than in birds, comports well with their
needs. More groundlings than these, their quest for
food is more deliberate, their meals heartier and
with temperate intervals. Their reserves of strength
and material are greatly in excess of immediate needs.
The combustion changes of their muscles and glands
furnish abundant heat, whether by the patent or hidden
activity of these organs, which is evidenced by the
_ dark colour of their flesh. Protected by both fat
and hair, this heat is but slowly lost, and the relation
of gain to loss is regulated by a nervous control that
is centred in the capacious brain. So accurate is
this adjustment that man and beast preserve their
several temperatures under hot, cold, and changeable
climates, and thereby ensure that continuance of
activity which is one reason for their dominance.

Fic. 27.—The Common Dormouse.—(Fvom a specimen in the
Manchester Museum.)

WINTER SLEEPERS 125

In this, as in all other excellences, we can trace
a series of steps from the lower and more variable
condition in reptiles ; for the lowest mammals have still
no even temperature, nor do they suffer fever from a
rise of many degrees.

In the development of every child and whelp the
heat-centres and heat-mechanism are only gradually
steadied and rendered independent of cold or heat;
whilst in the winter sleep and spring awakening of the
dormouse, bat, and bear we see strength of constitu-
tion that endures a quick change of 30 degrees without
experiencing any harm. At such moments, which
break a long sequence of still winter days and preface
a still longer period of activity, these hibernators show
a reptilian fluctuation and toughness.

The reserve and rare display of full mammalian
activity is well expressed by the voice. The calls,
chatter, and songs of birds rarely cease ; their notes of
warning, companionship, or exhilaration signal their
presence and arrest us. But with mammals it is
otherwise. The majority only roar, cry, or trumpet
to sound an alarm or in rare moments of combat
and excitement. Even the dog’s bark is a domestic
refinement. The highest group, that of the monkeys,
is the only querulous and chattering one, and this
habit seems to go with active, arboreal, and social life.
But, whether silent or vocal, all mammals possess a
larynx similar to our own, and it is the nervous control
and adjustment of the vocal cords, of the mouth
and of voice-production, that give pre-eminence in

126 ANIMAL LIFE

song rather than any structural difference which the
anatomist can detect. In this, as in all other bodily
excellences, the higher type of brain is the seat of
success. |

Throughout this long series of breathing, heating,
and sounding mechanisms we see the conquest of the
air, and the inward use of oxygen for effecting move-
ment, for maintaining that destructive aspect of the
double process of life in virtue of which existence and
growth are alone possible. But deeper than any
analysis we have yet made are the adaptations of
animal structure to ensure its increasingly efficient
working in passing from water to land, from cold to
warm blooded beings, from a silent to a vocal life.
The heart and blood-vessels, even the blood itself,
share in the advance, and become in birds and mam-
mals divided into two systems, one of which receives
aérated blood from the lungs, whilst the other receives
the waste from the tissues. From this change all
the tissues gain advantage. The muscles become more
thoroughly oxidised, and therefore stronger. Their
tone reacts on the body generally, and on the nervous
system in particular. The heat they exhale becomes
more generous, and the more abundant food they
require as fuel stimulates more strongly the glands
of the body. The trembling balance of life becomes
steadied by a firm central nervous control, and its ©
two emulating processes—the downward pull of oxida-
tion and the upward thrust of nutrition—are intensified
in the maintenance and growth of every part.

127

CHAPTER VII

THE SENSES OF ANIMALS

The action of the Nervous System as a means of
vesponse.—The procession of animal life from simplicity
to complexity of structure, each phalanx fitted to an
existence varying in richness of contact with itself
and its surroundings, is a choric response to calls upon
its nature that ages of trial have evoked.

Every living thing is an old hand. Its choice of
station and movement therein, its choice of food
and mode of breathing, its structure and the relation
of the component parts, are traditional and reflect
the heat and cold, the light and darkness, the hunger
and plenty of many generations. Some mighty
control has guided the steps by which each section of
this complex composition comes orderly into existence,
sustains itself there, develops, founds its family, and
after a day, a year, or a century makes room for its
fellows, leaving traces which cannot be mistaken of
the part it has played. The organisation of each
being, and of the pageant of which it is an assignable
part, exhibits signs of that orderly control and re-
lationship to the course of events within and without

128 ANIMAL LIFE

itself which is one of the most as facts of
natural history.

The visible sign of this harmonic grace is the
nervous system. Placed as a mediator between the
conduct of an animal and the impulses that arise
within it or that fall upon it, the nervous system
determines that life and conduct shall not be a spas-
modic response to every call that circumstances make,
but that the general well-being of the race shall be
consulted, and that in each life-history traditional
answers shall be given at first, until education has
conferred the power of a strong individual line of
conduct.

The nervous system co-ordinates the activities
of different parts of an individual being in order to
produce successful movement, good digestion, and
adequate breathing. It interprets as sensations the
stronger knocks that fall upon it from the outer world,
and to the tapping of light, sound, heat, odours, tastes,
and the like it answers by so many perceptions. It
responds to the calls that arise from within an animal,
and receives every moment of each day messages from
the organs that tell the condition of each one. If all
be well the messages are imperceptible to us; if any
part be weak, its call upon the nervous system becomes
louder, and, if not silenced by adjustment of its need,
we ultimately become aware of that which the nervous
system has known all along, and we call it hunger,
pain, desire.

Besides these faculties the nervous system is the

PERIODICITY 129

seat of traditional and individual memory. Through
the long succession of days and nights that have
lightened and darkened animal history with their
alternate periods of greater activity and less, the
nervous system has attained a rhythm which tones
the activities of the body. This memory of bygone
recurring conditions is preserved for us in the slow
swing of the brain, which controls the impulse of the
moment by the set of its own impetus, gathered
through generations of alternate periods of rhythmic
change into a fundamental beat. We awake and
sleep not only because the sunrise and sun-setting
call us to uprising and downsitting, but because in
our life and that’ of our fathers the rising-sun and
gathering darkness have impressed on our being day
by day and night after night an alternation of activity,
rapid heart-beat, daytime breathing, with relaxation,
slower pulse, and deeper breaths. At our usual hour
for sleep or wakening we tend to either, though dark
blinds or bright lights may delay our response to
habit. So the flowers that close at night will shut
their petals even though we turn their night into
day. Our fundamental action, if not, indeed, our
entire conduct, is thus no immediate response to the
calls that arise within us or that fall upon our senses,
but is determined to a variable extent by the tra-
ditional and by the periodic response of the nervous
system that has been established by habit; and to
this habit it remains true, though for varying terms
in different cases, even if the original stimulus that
K

130 ANIMAL LIFE

called it forth is removed or even opposed. This
faculty of the nervous system has been happily called
organic memory. If the conditions of life were un-
changing, such a faculty would be unimaginable.
But change—secular change—is of the essence of
life, and the fuller the life the more generous in num-
ber and amplitude of swing are the conditions under
which it flourishes. Not only day and night, winter
and summer, seedtime and harvest, set going . the
inward pendulum of animal life, but the life and
death of their associates, the swing of the tides, all
the great secular movements, beat with alternating
force upon the receptive nervous tissue. Upon these
leading motives that create habit others are super-
imposed. We learn to walk because the brain has
learnt to respond without effort along the trodden
paths of nervous life, and is free to learn the new
ways of upright adjustments.

Organic Memory an aid to Developmental lie: --
It is helpful to remember that once the nervous system
has established a periodicity, that then, like a pen-
dulum, it will continue to swing without the repetition
‘of the push that started it. For by such a metaphor
‘we are able to picture the development of an animal
‘in a new light. Nothing is more wonderful, nor
-more familiar, than the moulding of a life in dark-
“ness, and the gradual revelation of its conduct, at
first animal, then racial and traditional, and, lastly,
‘individual. But if we admit that life preserves a
‘memory of that which it has long experienced, and

Js

ORGANIC MEMORY 131

‘needs not always outward objects to assist that inner
eye, then the marvel of animal development becomes
a more rational process to us. The eye, which ages of
experience of light and sight has brought to near
perfection, is moulded without a flaw in darkness ; the
hands, which have developed by grasping, are formed
without a movement; wings are made ready where
no air is and where stillness reigns. The responses
which are to govern conduct are developing there
also. Each unwavering act in this bodily and psychic
drama has a long history of effort and failure and
success behind it, and here it is summarised in a few
weeks of unchanging darkness. But if the eye re-
acts without light, the formation of the eye may not
require the original condition which called it forth.
All we know of development seems to show that
from the commencement of life each being has a
memory, and that each organ plays some part in
starting that memory into life. Each part of us is a
member one of another. ;

The most important of these organs and the
earliest to appear is the nervous system, for that has
the most complex history to recapitulate. But for
its full epiphany its memory has to be stimulated by a
substance that comes from the thyroid gland, passes
into the blood, and, carried to the brain and else-
where, evokes the series of changes that help to build
up a normal child. Should this gland fail to act
efficiently, stunted mental and bodily growth result.
. The child is numbered with the feeble-minded. But

K 2

132 ANIMAL LIFE

now, let that organ be taken from some other animal,
say a sheep, and its extract be given in doses to the
dwarfed being, there will often result a gradual change.
The needful stimulus is taken up by the blood, carried
to the brain and body, and there evokes the hidden
and arrested growth of the stunted parts.

In such a way many organs play their part by
exciting the activity of others, perhaps far away
from them; and to this principle we can attribute the
strange and orderly persistence of organs whose
primary use has disappeared. The gill-slits, for
example, which recur with unfailing regularity in the
development of all vertebrate animals, are only used
in their primitive sense by fish. But in higher animals
their walls give rise to thyroid and other glands that
serve to excite the growth of the neck and larynx, and
without these glands and gill-bars, which in fish have
a totally different function, our development would be
imperfect and retarded. Or, to take perhaps the most
striking case—the change from youth to manhood,
and the corresponding change in animals—a stimulus
affects the whole body, alters the voice, broadens the
chest, beards the face, and intensifies the conduct.
In animals, as we have seen, so great is this change
that the colour and eyes, the limbs and skin, undergo a
complete metamorphosis : their movements and habitat
are exchanged for new ones; the bird, fish, insect, and
even certain worms, become different beings. When
the change is less radical, as in the growth of antlers
and resonance of voice or ferocity of manner, we

SENSE-ORGANS 133

recognise the same mode of response of the animal’s
nature to a stimulus that sets up new development.

The Organs of Sense-—When this view of animal
life and development as an orderly response to inward
and outward stimuli has become familiar we are able
to consider the nature of the senses of animals. The
organs of sense are such as originate a message of a
definite kind destined for the nervous system. Besides
the five senses we have a muscular sense, one of heat,
of cold and of pain. In addition to these, messages
too faint for our brain to interpret are passing to it
from all parts of the body and informing it of their
several conditions; to which messages it is able to
respond by assurances of which we are totally un-
conscious. The good results of rest, fresh air, change
of occupation, are the outcome of such toning effects
of the nervous system on the muscles and organs
generally, of whose needs we are only vaguely conscious,
but to which the nervous system responds with more
than a physician’s skill and promptitude.

In dealing with the senses, therefore, we shall
consider these subconscious senses, as well as those of
sight, hearing, and outer impulses.

The psychical phenomena of animals present a
marked contrast with the physical. In structure
and mode of development animal life presents varia-
tions of endless diversity on several themes. The
complications that adapt creatures for life under
water, on land, and in air are of the most diverse kinds,
whereas the fundamental instincts possessed by this

134 ANIMAL LIFE

organised array are seven or eight only. Indeed, if
we extend our researches to the lowest animalcule,
we find that in it all the essential responses occur
which form the themes of the fugues in higher animals.
Sight, taste, touch, smell, balance, temperature, and
parental instincts, are distinct although there is no eye,
no ear, no tongue, and no specialised organ of any kind.
Even the element of choice is not absent, and in the
lowliest animal the psyche decides what to eat, what
to absorb, when to retire from or advance to light or
some counter-attraction. Indeed, we may go further
than this and say that plants, and even the lowest
plants, possess all the fundamental responses. They
respond to light, they perceive odours, they choose
what to absorb and what to reject. They are sensitive
to shock, and even possess sense-organs of a rudi-
mentary kind. In an organism devoid of a nervous
system and without any organs of a specialised cha-
racter all the responses are present, and they direct
its life. The astounding diversity of animal and plant
life, therefore, only gives expression in a thousand ways
and with added clearness and fulness to the responses
that their most degraded member possesses; and
though writers have ascribed similar ethics to the dust,
it is probable that this fundamental psychical uni-
formity of living things forms one great character
distinguishing them from the not living. Te

The reason of this uniformity does not seem hard
to find. The essential objects and conditions of life
are everywhere the same.. Maintenance, development,

LIFE. AS A RESPONSE 135

and family or racial cares are its chief aims. Light,
vibration or pressure, touch, odours, heat, and dryness
or wetness, are its chief conditions. Each of these
changes with greater or less regularity. The alterna-
tion of day and night, of heat and cold, tell upon all
living things. The prehension of food involves the
sense of contact with bodies of many. kinds; whilst
movement involves changes of pressure. Growth and
development introduce new factors. The. presence of
active enemies or of inimical conditions tests the race.
For the lowest animal, therefore, some perception of
these fundamental conditions, some power of response
to their changing quality, some means of meeting
emergencies, seems essential. The surprising result is
that even the simplest organism gives no hint of any
different life than that pursued by the higher ones.
All the senses, dim though they be and exercised
without organs, are there. The conflict of ages has
totally obscured any primitive life. The simplest
creatures are old hands, and tell us nothing of what life
would be without the power of response. :

But though we are denied insight into the begin-
nings of adaptive response, we can still trace its
development in the many and Se ae forms of
animal life.

In fact, life depends upon these fundamental
responses to living or non-living agencies. To us, in
-whom the enjoyment of the senses is a luxury, there
is always a difficulty in appreciating the close, neces-
sarily responsive touch in which the simpler organisms

136 ANIMAL LIFE

live with light, water, and air. A plant moves towards
the light, its roots track the watercourses, its leaves
respond to the quality of air, because in these acts it
finds the materials for food and new life. In the same
way these old responses form the basis for animal
actions. In them the senses are not emotions or per-
ceptions apart. They are invariably bound up with
a movement or adjustment which has to do with the
preservation of life; and these adjustments are no new
acquisition, but are traceable in the humblest living
thing. The origin of instincts has been needlessly
obscured by overlooking the fact that ‘ sense’ is only
a link in a chain of action, and also by treating organs
of sense as things apart, instead of regarding them as
inseparably linked with essential adjustments.

The Senses of Shrimps.—Instincts are combinations
of these old responses. We may take a shrimp as an
example. By day we see it lying motionless in the
sand or clasping a branch of seaweed. By night we
find it swimming with great vigour at the top of its
prison-water, its heart and breathing organs beating
at a great rate, its colour altered from brown to blue,
and its nervous system extremely highly strung and
sensitive to shock. At the least alarm it will now
leap out, whereas by day no ordinary disturbance
would cause it to forsake its chosen spot. The tone
of its being has been altered, and after persisting
through the night this agility will give place at day-
break to the more sluggish habit of its sleeping hours.
In recording the behaviour of an animal, therefore, we

ae

THE RESPONSES OF SHRIMPS 137

have to consider its nervous condition, which is a
function or outcome of a long succession of days and
nights. By turning its night into day and day into
night we find that for the first day or so of experiment
the change of tone still occurs at the appropriate hour.
Thus at nightfall, in spite of artificial light, the animal’s
colour deepens into red, then to green, and finally to
blue ; its limbs, heart, and breath take on anew rhythm,
which endures for a night and then disappears. In
the same way, if we prevent the morning light from
making itself felt, the shrimp will still, for a day or so,
time its recovery from a nocturnal bout as though
informed of day’s appearing. In fact, the nervous
system is the master, and for a while its innate perio-
dicity determines the rate of the animal’s activity.
This result shows what a supremely important part
light and darkness play in animal economy. Con-
tinued bright light shocks it to stillness; dim light
gives it the necessary suppleness of limb.

But now, suppose this action worn down by the con-
stant effect of continued light or darkness; we have
then the shrimp in a more responsive mood. The
tone of its surroundings now influences its colour in
a more direct fashion. On light backgrounds it
quickly assumes a pale tint. On dark ones its red
and brown pigments produce a dark tone. If we
cover its eyes this faculty of sympathetic colour-
change is abolished. The brown colour persists under
all conditions of illumination, and we thus conclude
that the skin is influenced not so much directly by light

138 ANIMAL LIFE

as indirectly by the stimulus of sight, which is trans-
mitted to the skin by the nervous system. Moreover,
as the colour of the animal is deposited in the muscle-
pigments as much as, or even more than, in those of the
skin, and since the colour-changes of the muscles follow
those of the skin, it is evident that the eyes govern
changes in the muscle as well as those in the skin.
We are led to look upon the eyes, therefore, not only
as organs of sight, but rather as one link in a chain
of response which is evoked by light from the whole
animal. From this point of view the eyes, acting upon
the nervous system, both govern the colour-relations
of the shrimp and give the tone to its muscles and
general activity.

In a somewhat similar way we may look upon the
response to vibration, the sense of pressure and of
equilibrium. The shrimp has two ‘ears,’ placed in
the first pair of horns, or in some shrimps near the
end of the tail. These ears are hollow balls containing
a solid body, either grains of sand or a small block of
lime; and it has been found by experiment that
accurate balance during swimming or walking is de-
pendent upon the healthy condition of these ears.
Like the eyes, they communicate with the muscles
and skin. by means of the nervous system and have
the faculty of compensating any tendency to upset or
overturn. They register every vibration that the
waves cause or that movement induces. These ears
are, in fact, organs of touch with a delicate balance
and intimate connection. with the muscular. system ;

THE RESPONSES OF SHRIMPS 139

and though almost every part of the skin of the shrimp,
and in particular its legs, is provided with sensitive
hairs, and is to some extent sensitive to change of
pressure, such as a wave or a movement implies, yet
the ears by reason of their position near the brain
have a more commanding influence on the whole body
—an influence they practise even in times of peace.
The sense of taste or smell plays such a large part
in animal life that we must consider it as a fundamental
response ; yet in the shrimp, as in all animals, though
so important, this sense has no well-defined organ
through which it works. All we know is that certain
hairs on the upper lip and antennz, like those of a cat,
act as feelers, by which the neighbourhood of food is
recognised. The response of the body to this sense
is a complex one. In a chain of concerted action
muscular events begin that stretch from one end of
the body to the other and engage the activity of many
limbs. The food of the shrimp consists of small
bivalves, which it finds amongst the sand in which
it burrows. The little shell is picked up by the big
claws and transferred to the mouth. Here the excite-
ment: of the upper lip and jaws spreads to the lower
lip, and to limbs further back, as well as to parts
further inward. The mouth begins to water, that
is, the digestive juices are prepared; and so the whole
series of digestive processes—the dissolution of the food
and its absorption—are linked up as a composite re-
sponse to the smell roused by the discovery of food. Yet
this response is ultimately referable to the property of

140 ANIMAL LIFE

distinguishing and preferring chemical substances,
which enables all living things to absorb nutritive
substances when surrounded by a mixture of hetero-
geneous bodies.

It is only in some of the higher animals that the
organs of sense become so highly developed and the
perceptions arising through them so well defined
that sensations become phenomena apart from those of
motion, digestion, or of others immediately concerned in
the welfare of the body, so that we cannot yet resolve
their complex actions into the simpler responses from
which they have sprung. .

The Origin of Sense-organs from the Skin.—The skin,
upon which the outer world impinges, contains the
sense-organs which receive and transmit its messages,
and the deeper parts of the skin develop points from
which their needs emerge. Thus, upon any organism
a double set of impulses falls, one from without,
another from within. Each of these is at first
intimately connected with the fundamental acts of
life, and in order to correlate the supply indicated
from without with the demand indicated from within
a nervous system has been gradually elaborated. In
the first instance it appears to be related rather to the
efficient response of the body to the external messages
—pressure, food, light, and so on—and in particular
to movement. But it is clear that, since these
responses are of vital importance, they must be cor-
related with the inrfer needs of the body ; and so there
come to be not only a nervous regulation of move-

—

ORIGIN OF THE NERVOUS SYSTEM 141

ment, a response to vibration or to food, but also
an inner mechanism by which the food-canal, the
breathing-apparatus, and the other internal organs
are brought into nervous connection with the outer
mechanism of skin and muscle. In other words, we
see the outline of that control and perception of the
outer world by movement, prehension, and touch,
and the satisfaction of the needs of the inner world of
hunger, growth, and racial cares, that is roughly in-
dicated by the terms central nervous system and
visceral nervous system.

The question may perhaps be asked, Why have
animals developed a nervous system? The answer,
so far as we can give it, bears upon the last discussion.
Animals move freely and eat solidly. These two facts
go together, and have led to an inevitable distinction
between the outer locomotor and inner nutritive
regions. Now it is clear that, even if no formal nervous
system exists, animal movement demands and pos-
sesses a directive and controlling influence. Further,
as we know, this regulated locomotor mechanism is
able to transmit food to the mouth and to inhale water
or air, and the body is able to move the food from
place to place in satisfaction of its needs. In other
words, animals, even the simple, such as polyps, have
a virtual nervous control of their organs of movement
and of their visceral organs, and a correlation between
the two. Movement, then, and solid food have, so far
as we can see, been the two factors responsible for
creating the need for that control which is simply

142 ANIMAL LIFE

emphasised in the primitive nervous systems, such as
those which jellyfish and starfish possess. In fact, the
development of these animals shows that the muscle
and skin are at first continuous, and the strained
threads that connect the two, as they separate for
their respective functions, become the nerves for em-
phasising movement. In a similar way the food-tube
is at first a part of the skin, which becomes pitted in
and grows inwardly, and the connection between its
layers and the muscles and skin of the wall of the body
furnishes the basis for its visceral nerves, and for the
correlation between their demands and the exertions of
the locomotor organs in the prehension and supply of
food. Thus the nervous system of animals is inti-
mately related to the primary conditions and needs
of life, and is organically descended from the neuro-
muscular skin and the neuro-muscular food-tube.

The development of animals, even of ourselves,
shows how close is the relation of the nervous
system to this primitive plan just sketched, and how
intimately the sense-organs are connected with the
skin. The skin in all animals is an organ of one or
more senses, and from it arise the essential sensitive
parts of those sense-organs, such as the eye, the ear,
and nose, which seem to be unrelated to it. It would
appear incredible that the retina of the eye, the equally
delicate and more complicated lining of the ear, should
be a modified patch of skin; yet such is the case, not
only in one group, but in all; and, indeed, in some
groups it is possible to pointjout a series of stages in

ORIGIN OF THE NERVOUS SYSTEM 143

‘which the eye commences as a mere open pit, then
develops into a closed vesicle, and passes by degrees
into an organ whose complexity approaches, if it does
not attain, that of our own ; whilst with regard to the
ear, the skates and certain other fish still retain an
open tube by which their ear is placed in communica-
tion with the skin.

In the early life of animals the nervous system
itself is at first in close contact with the embryonic
‘skin, and only gradually sinks down to take up its
position in the enclosing bony or gristly tube that is
to form the vertebral column ; whilst in many primitive
forms its connection with the skin is retained through-
out life. The nerves which direct movement are
actually developed in connection with the muscles
and skin, much as in the case of a jellyfish or sea-
urchin; whilst those nerves that announce hunger,
desire, and generally the condition and needs of the
inner organs, are derived ultimately from ingrowths
-of the surface layer. The two sets of organs—the outer
-or directive and inner or visceral—become inter-con-
nected by nervous ties that provide pathways whereby
the need for food or breath, for example, is able to set
in motion a movement of the body that tends to supply
that need. So we see a full animal is quiescent,
a hungry one is active. In the reverse way, the sight
or taste of food sets going the nerves that connect
the prehensile organs with the digestive ones, and so
“prepare the way for the reception of food. So short-
ness of breath induces more rapid breathing, as we see

144 ANIMAL LIFE

in fish when the water of their aquarium has become
partly exhausted. In short, whilst the movements
of an animal are stimulated by light, heat, and outer
agencies, they are controlled by a nervous mechanism
that is not only related to that control, but is also
concerned in satisfying the inner desires by those
movements. |

Gradually these adjustments become not only
automatic in their working, but by their repetition
induce a second self, a periodic heightening and lowering
of the central governing control, through which the
rate of automatic working is rendered steady for long
intervals and is protected from becoming spasmodic
and from changing with each change of scene. Thus
we find choice becoming obedience and obedience
becoming tradition, giving, as it were, a direction
which the answer may take, though not determining
the intensity of its response.

The warm blood of the higher animals creates a
further buffer between them and the changing con-
ditions around their bodies; it wards off from them
those changes of temperature which sink their less
fortunate relations into stupor or death.

The value of this mechanical and traditional tend-
ency is easily misunderstood.. We need not look upon
it as necessarily converting the whole life of an animal
into a series of purely automatic actions. For if we
steadily keep our outlook on the gradual evolution
of self-consciousness, we shall see in this stiffening
of action the necessary prelude to advance in the

FROM CHOICE TO HABIT 145

higher responses. It is not merely because we are
relieved of decision about manipulation that would
otherwise check our advance, that as speech, draughts-
manship, or reckoning become easily performed, that
therefore language, art, and astronomy have become
a more perfect expression of the universe. The un-
burdening transfer from act of choice to act of drill
and from the strain of memory to the habit of tradition
allows not only further advance to be made, but
preserves the past and forms when complexity has
been gained a point of departure for responses to
messages which before were too high for us to in-
terpret or hear. These messages, coming either from
within or from without, are no new things, but, like
the pulses that beat upon us all day long, were un-
perceived till the insistent voices of needs were stilled
and we became attuned to a more receptive pitch -of
nervous strain. Thus upon the solid groundwork of
embodied and self-contained, self-regulating tradition
the needs of maintenance are satisfied, leaving us free,
not to sink into the torpor of automatism, but to
respond to finer impulses which the cares of main-
tenance had hidden. The needy artist must first
make his bread and then practise his art; and the
making of bread creates the necessary organic pre-
paration for esthetic perception and work. Even
so the classes of animals richest in manual work
and tradition are alone they which have esthetic
preceptions.
‘For to him that hath shall be given.’

146 ANIMAL LIFE

The performance of work done out in the open
leads in each class to a capacity for new response,
and therefore to greater variety of handiwork.

Amongst the Protozoa, those are the most
complicated and the highest which have left shelter
to inherit the fuller traditions of the open sea.
Amongst the zoophytes there is one family—the
siphon-bearers—that has surpassed all others in
gracefulness and variety of shape, in intensity of
colouring and virulence of poison, and it is this family
of the blue velella and the violet ‘ Portuguese man-of-
war’ that has had no rest, that has felt the unceasing
beat of the sea, and without intermission has been
stimulated to action. A more familiar example is
the hydroid-polyp of the shore, with its simple struc-
ture and plant-like responses, and: the jellyfish that
arises from it but strikes out to sea, where its. eyes
and ears, its muscles and poison-organs become elabo-
rated through its constant adjustment, varying to
meet the changing action of light and waves and
the choice of food.

But it is on land and in air that adjustment be-
comes more arduous, oxygen more plentiful, and
advance,. though difficult, more pronounced. The
play of light, heat, and vibration, the influence of
weight, the sources of friction, the steepness of hills,
all tell with greater force on land than under water.
To those animals that can make the adjustments and
endure even for a few months the rigour of a changing
climate a higher place is assured than to their brethren

INTELLIGENCE 147

of the sea; whilst the old, the irresponsive, adopt her-
mitage in the soil away from the stress of life. So it
is not till the physical adjustments become varied,
sound, and performed with ease and without thought,
that we find the dawn of intelligent response to the
living factors of the situation; the response to an
impulse, not themselves, that has been at work all along,
but is hidden from animal life until a certain stage
of responsiveness has been attained. Then as racial
instinct, the spirit of the hive, or by whatever name
we call it, sometimes in solitude, more often in com-
panies, the finer issues of life are felt and responded
to by those that generations of manual work, delicacy
of touch, and observance of open-air changes have
cultivated. Birds and insects rule the air by un-
thinking adjustment. -Man rules the earth by
thoughtful adjustment. His success is due to his
power for profiting by experience, both in his in-
dividual and corporate life, and thereby rising in
capacity for response to more and more complex
motives, whether for good or for evil.

The domestication of animals may illustrate what
far-reaching results flow from a simple act when that
act can be repeated and modified in the light of
experience.

In common with other carnivorous animals man
kills for food, and in general with as little foresight
as they. Nevertheless, here and there a genius will
have noticed that, after a successful chase, to keep

alive that which is not required will give power. And
ve

148 ANIMAL LIFE

these more far-seeing warriors, having begun to capture
as well as to kill, acquire wealth and fame. To the
consequences of this simple act more than to any
other, civilisation is indebted for its development from
the ‘ pack,’ through the pastoral to the political state.
The Australian remains for us the nearest of all living
races to that primitive hunting state ; and the nomad
shepherds of the East illustrate the art which has
given rise to ‘capital’ and to ‘ pecuniary’ advantage
amongst the more advanced races.

REFERENCES

‘ Animal Behaviour’: Lloyd Morgan.

‘The Senses of Animals’: Siy J. Lubbock (Lord Avebury).
‘Internat. Sci, Series,’ vol. xv.

Influence of domestic animals on civil history: Maine,
‘ Ancient Law’ ; Jenks, ‘ History of Politics ’ (Temple Primers).

eeEE—————eE—

149

CHAPTER VIII

THE COLOURS OF ANIMALS

The Primary Meanings of Animal Pigments.—In
man and creature colour is sacramental. Complexion
in man is a sign of racial constitution and tempera-
ment, and colour in animals is the expression of that
hidden working which controls, and is controlled by,
their life. |

We regard, and rightly regard, the body as fuel for
fire; its activity as the outcome of a combustion
which is fed by food and fanned by air, the engendered
heat being carried by those hot-water pipes, the
arteries, to the remotest outworks of skin and muscle,
of bone and nerve, there to replenish the loss which
secretion, movement, and nervous activity involve.
And as from coal we can obtain not only heat, but
tarry matters and aniline dyes, so from the slow —
combustion of the tissues does the body deposit
those grains of matter which, when exposed to the
light and air, become pigment, as a cut apple goes
brown or a chipped toadstool blue. Colour is thus
distilled, as it were, from the whole body, and resumes
its essence in a seemingly surface finish, |

If we now review the colours of animals, we are

150 ANIMAL LIFE

struck by this influence of light on their distribution.
A dark back and a pale under-surface form the most
general of all schemes of colouring. Insects and
worms, shells and starfish, fish and frogs, birds and
most beasts, through a vast category of marine and
terrestrial forms, display the white breast. Squirrels,
the most vividly coloured of mammals, still keep the
tule ; whales and fish agree in the contrast of their
dark upper sides with their white nether surfaces.
Blue and brown butterflies are only so when seen from
above ; and if we turn up the palms of our sunburnt
hands, we find that there too pallor is more evident
than on the upper side. Colour and light-exposure,
pallor and light-starvation, are correlative terms. As
the green colour of plants fades in darkness and shade-
leaves, so the nether parts of animals are bleached by
the lack of light.

To confirm this and give the mind living. hold
upon its significance we must apply the test of experi-
ment. If light induces colour, and darkness prevents
its appearance, then we should, by inverting a young
animal, obtain some evidence as to the present-day
applicability of this principle. This has been done
both artificially and by that age-long trial that natural
experiments involve. Young plaice have been grown in
a tank, lighted from below and darkened above, so that
the under-surface of the fish, which is normally turned
away from the light, was exposed during the hours of
daylight to the light reflected from a mirror. After
an interval of a few weeks several of the batch so

LIGHT AND COLOUR I51I

treated were found to have developed spots of colour
on their under-surface, and thus to present an ambi-
colourate appearance. Ultimately one of the fish
became almost totally embrowned, and lost all but
mere traces of its usual silvery whiteness.

More convincing even than this experiment is the
one which Nature herself has carried out on the sucker-
fish. The sucker-fish is a parasite hanging on to the
bodies of larger tropical fish for the sake of the crumbs
that fall at meal-times. To ensure its hold the fish
has converted its dorsal fin into a strong, transversely
ridged sucker, which it applies to the upper side of its
host, and thus views the world standing on its head.

Its back is in shade, its belly in light, with the
result that the usual colouration of animals is here
reversed—its back is white and the belly dark, almost
the only exception to the otherwise universal rule ; and
so accustomed are we to it, that when we first handle
a sucker-fish we involuntarily turn it upside down and
unconsciously acknowledge the strength of that asso-
ciation that leads us to regard the dark surface of an
animal as the upper one.

Whilst we can thus conclude that the shaded parts
of the body become pale and the exposed parts dark,
there are some natural experiments upon the total
bleaching of the body by generations of cave life.
The cave newts of Carniola, in Hungary (fig. 28), have
become famous. They are milky white blind newts,
a foot or so in length, and live in the darkness and
cold of subterranean waters. Unlike their allies, the

152 ANIMAL LIFE

askers, which are coloured on the back, these cave
newts are without any trace of pigment. That they
have lost their original colouring subsequently to
adopting cave life is a conclusion rendered highly
probable owing to the discovery of still another
colourless species in South America which is related
to quite a distinct family of darkly coloured newts,
and is borne out by the occurrence in the same caves

Fic. 28.—The Cave Newt of Europe (Proteus anguineus).
(From specimens in the Manchester Museum.)

of white shrimps and bleached insects, whose relatives
lead a free life and possess a coloured skin. But this
bleaching is only permanent so long as light is excluded,
and if these cave newts are brought into daylight they
develop in the course of time a dark skin, and after
a few months become almost black, the change being
most marked on the back of the animal. Experiment
thus confirms the power of light rapidly to excite
the formation of colour or pigment, and the power of

LIGHT AND COLOUR 153

darkness to prevent the appearance of colour or to
destroy a pre-established colour in the course of
generations. |

With this thought we may look out on the colours
of the animal world and observe the broad general
agreement between the arrangement of these tints
and the green colour of plants. The two sides of an
animal differ as do the two surfaces of a leaf ; the upper
one, being the more exposed to the sun, is the darker ;
the lower, more shaded surface, is the lighter one.
Animals, such as worms, that keep one end of their
body root-like buried in the ground become at that
extremity bleached, and those that are altogether
excluded from the light, like a tuber, are totally
colourless. A plant grown in the dark becomes pale
and chlorotic ; an animal, though more slowly, becomes
no less drastically etiolated. Transported from dark- .
ness to light, the leaves of a cellar-grown or shaded
shrub reassume their green colour, and with no less
certainty the colourless troglodyte becomes dusky
when illuminated. Nor is the full light of the sun
necessary for the development and preservation of the
colours of animals and plants. In a dim light vast
numbers of jungle plants, forests of brown and red
seaweeds, multitudes of crepuscular, creeping things,
and deep-sea fish work out their life with as full a
colour as their relatives and brethren of the sun.
The mole and bat are no less deeply coloured than the
sparrow or skylark ; the pygmies of the dark Congo
forest are brown as the tribes of open country ; the moss

154 ANIMAL LIFE

of a waterfall on which no light shines is as full a
glossy green as the velvety covering on a south wall,
and shows us that though light and colour, darkness
and pallor, are causally related, yet the intensity of
the necessary light and the need for its continuous
employment and the mode of its working have to be
considered before we can unravel the tangled problem
of animal colouration.

In a plant these factors are comparatively easy to
determine. The green colour we know is associated
with the production of the plant’s food. In the leaf,
starch or sugar is formed as a preliminary step towards
building up the plant-substance by union with juices
that rise as sap from the roots. For the efficiency of
the leaf light is requisite. Cut off all light, and the
leaf is starved in a day, and dies. Expose the leaf to
a continuous direct light, and it is no less infallibly
killed, though replete with starch. In the moss and
fern tribe darkness and starvation may long be endured
with impunity ; in the cactus group intense light and
plenty are equally well borne. But, however varied
their powers of adaptiveness may be, plants require
the green colour for a definite object—namely, to lift
the carbon dioxide of the air to a higher power, which
in one form we call starch, in another sugar ; that is, the
green colour of plants subserves nutrition, and to do
this light is required.

In this process of modifying the carbonic acid of
the air its oxygen is set free and made available for
the needs of aquatic plants, so that by day starch

and

EEE See ee

COLOUR DUE TO PLANTS 155

is formed and oxygen provided. The green colouring
matter of plants is, consequently, concerned in the
processes of replacing the matter of living substance.
Its fundamental importance and its simple require-
ments explain the ubiquity and abundance of green
colouring in plant-life.

Amongst animals there is no such fundamental,
widespread, and nutritious pigment. That mysterious
and seemingly simple hold upon earth, air, and water
by which plants make their living, if it exists in animals,
is no prominent feature of their life. Their food is no
cunning mixture of gas and water. In spite of fable,
the chameleon does not live on air, but on flies; nor
does the possession of a green colour by many frogs,
snakes, birds, insects, or worms confer upon these
animals (with one remarkable exception) the ability to
subsist without solid food, even where the green matter
has proved to be identical with that of plants.

A plant living in an animal, as plants (Flagellates)
do (p. 106) in Protozoa, anemones, and some worms,
is only capable of keeping its host from starvation by
submitting to be eaten up piecemeal, and should
further solid food be lacking the menagerie dissolves
partnership. Whatever value we can attribute to
animal colouration, a nutritive one would seem to be
the least probable, and we turn to the other side of
life’s balance-sheet, the income of energy, to see if
there is any animal pigment which has the property
of allying itself with the oxygen of air and of purveying
that oxygen to the tissues of the body.

156 ANIMAL LIFE

In this quest we soon meet with success. The
red colouring matter of blood is such a vivifying
substance. The aérating virtue of the blood lies in
that colour, and should it fade we become weak and
anemic ; should it disappear, we succumb ; our fires
burn out from need of the oxygen which the red
pigment, and it alone, can dispense.

To most animals, as to ourselves, this pigment is
essential. All the members of the vertebrate class,
cold- as well as warm-blooded, possess it. It gives not
only the colour to the blood, but the dark tint to the
muscles. Below this class it occurs sporadically in
snail, starfish, and worm, conferring upon their blood
and muscles a greater efficiency than is possessed by
their colourless relatives, and the ability to thrive in
stagnant water or amid ill-ventilated surroundings.

In producing the gross colour of the animal this
pigment takes but a small share, and it is only when
a given supply has done its work and steps aside to
make room for the new flow that comes from the
marrow of the bones that it is apparently removed
from the “blood-vessels, transported to the skin, con-
verted into a black pigment, and stored in hair and
feathers, there to give rise to the colour of the body.

But the interest of the red blood-pigment is not
confined to its wide distribution, its life-giving property,
or its usefulness as a source of surface colouring. In
its chemical nature this pigment shows a family con-
nection with the green colouring matter of plants.
In their purest known state each of these bodies,

ee

pa eS ee

LOSS OF COLOUR 157

the one red, the other green, appear as cousins, related
through some as yet undiscovered stock. Each has
diverged at some remote epoch along a line“Sf its own,
and in course of time produced the substance that
we know as the green colouring matter of plants and
the red pigment of the blood of animals.

Yet, in spite of this divergence and seeming dis-
parity, we can detect points not only of resemblance,
but of affinity. Both have a like, though hidden,
family constitution, indicative of a common but
remote genetic connection.- They occur with un-
failing regularity in the higher divisions of the two
kingdoms of living nature, and become less constant
in the lower members of animal and plant life. In
those plants which live parasitically upon the tissues
of other organisms the green colouring matter is absent.
Its nutritive power of making and purveying sugar,
starch, or oil is not required.

In the vast class of moulds, mushrooms, and toad- —
stools there is not one that has the requisite green
pigment. Amongst typically green plants there are
still more striking examples of the loss of colour
following upon the adoption of parasitic habits.

The dodder that infests vetches and clover sucks
the juices of its host and loses its livery. The minute
colourless Flagellata which abound in organic infusions
are cousins to those Euglene that fill the roadside
hollows with a green scum, and if only water and light
are supplied to them their colourless bodies reassume
the green tint and create a food store from such

158 ANIMAL LIFE

inorganic sources. Itisjust among such plastic, chame-
leonic Flagellates that we can trace that remote con-
nection between animals and plants to which biology
points from whatever side we study it—in infusions
an animal, in water a plant; producing starch like
a leaf, and yet such starch as only the muscles of
animals evolve. Still for long intervals like an alga,
and anon swarming in a dense throng like a shoal
of microscopic fish ; abandoned in turn by the botanists
to zoologists, and by zoologists to the botanists, this
group of Januses is ever enticing the naturalist to its
study, and yet refusing to fit into the categories he has
made. From such Flagellates all the families of sea-
weeds trace their descent, as to the founder of
dynasties, and to them also many of the lowest animals
and the sponges owe their genesis.

The loss of green pigment amongst animals would
thus seem to be due to their mode of feeding upon
organic food, which was not only a richer diet, but,
unlike the primitive plant food, could be obtained in
dark as well as in light places. e)

When the activity of these dual organisms increased,
as it necessarily did in pursuit of fresh stores of
organic débris, the need for nourishment increased
also. The new and characteristic animal tissue—
muscle—demanded both oxygen for contraction and
also nourishment by appropriate food, and im-
pressed into its service that faculty for vivifying the
body with oxygen which in its green youth was
associated with the body colour; and in the lower

RESPIRATORY PIGMENTS 159

animals we see, following the gradual insistence of this
respiratory demand, the gradual evolution of a more
and more efficient oxygen-carrier. In the shellfish
the blood has only a quarter of that oxygen-holding
capacity which we possess. In the worms which live
where little air is available, the blood is richer, and
either green or red. In the vertebrates the blood is
always red, richer in oxygen-holding power, and meets
the demands created by the growth, bulk, and activity
of the body for a continuous supply of oxygen to all
the tissues. Of these demands some are more pressing
than others, and we can assign the deeper colour of
the more active muscles to the great stores of blood-
pigment heaped up for their use. Hence the darker
legs of a hen contrast with its breast, or the dark flesh
of game with the white flesh of poultry, And further,
if the generally accepted opinion is correct, that the
yellow, brown, and black pigments of hair and skin,
to which all the higher animals owe their colouring,
are kinds of effete blood-pigment removed from
the circulation and dumped down out of the way,
then we may look upon the blood as furnishing the
pigments which are worked up upon the canvas of
skin into such superb embroideries.

We can thus broadly trace the rise of the red colour
of the blood to its source in some distant connection
between plants and animals, of which its chemical
affinity with plant-green is confirmatory evidence.

Evolution of red and yellow fatty pigments—A no
Jess complex and vet fascinating quest than this of

160 ANIMAL LIFE

the history of blood-pigment is that of the yellow
and red colouring matters of the lower animals. We
all know the red colour of boiled shrimps, lobsters,
and crabs, and the change from blue to red which
these Crustacea suffer in the process is but an instance
of the breaking down by heat of a delicately poised
and unstable substance, and of its return to the basal
red pigment which we see in the change of phosphorus
from red to yellow on heating.

But we are not familiar with the fact that such
red and yellow forms of a definite chemical substance
run like a thread through animal and plant organisms,
giving evidence of a similarity of constitution that
appears more and more strongly to the mind as we
grow acquainted with these unexpected relationships.
The yellow yolk of an egg, the red shell of a lobster
and yellow substance of a carrot contain a colouring
matter of the same chemical nature. The same
material colours the wax of our ears and the visual
purple of our eyes. The eyes of birds and reptiles
possess yellow globules, scattered amongst the part
most sensitive to light; the eye of man and of ape
has its yellow spot or centre of acutest sight; and in
the eyes of nearly all vertebrates there is a reddish
pigment which belongs to the same class of coloured
substances. In the skin of fish and that of frogs,
which are so highly nervous as to be hardly less
susceptible to changes in their neighbourhood than the
eye itself, the same yellow and red pigment is abun-
dantly found, and there assumes the form of minute

FATTY PIGMENTS 161

star-shaped masses (chromatophores), which can con-
tract to a mere dot, leaving clear interspaces between
one mass of pigment and another, or, again, can expand
to a radiate form, branching out and filling the skin
with a tracery of colouring. In the same way the
skins of shrimps and prawns are dotted’ over with
little mobile bags of pigment, now expanded into star-
like forms and rendering the animal of a deep brown
colour, and anon contracting to as many microscopic
black-looking dots, separated by clear interspaces,
and the effect of which is to give the shrimp or prawn
a transparent and colourless appearance.

_ As we go further down in the scale these pigments
become still more abundant. They suffuse the skins
of most starfish, sea-urchins, sea-cucumbers, and brittle-
stars. |

This substance, which in its yellow or red form has
such an extraordinarily wide distribution amongst
animals, is no less common amongst plants. The
green substance of ordinary leaves contains it. In all
underground stems, roots, and tubers it is present,
though often only in small quantities, as in the turnip, |
or in a concentrated form as in the carrot. In the
fungi it produces most of the brilliant orange, yellow,
and red effects that so strikingly catch the eye on
leaves, palings, and tree-trunks which are infested by
moulds. Even amongst the simplest of all forms of
life—the bacteria—the same pigment is still to be
found. From the lowest to the highest forms of plants,
from the simplest Protozoon up to man himself, there

M

162 ANIMAL LIFE

is no large class in which the yellow and red pigments
are not to be found, though we may have to search
in the remotest and most delicate organs before we
find them ; they may confer the most brilliant colour,
or be hidden and valueless as regards it.

The meaning of this widespread colouring is not
yet fully understood. It may well be an apparatus
of extreme antiquity, which has been to some extent
supplemented by newer methods. These pigments
are occasionally capable of producing starch in the
presence of light, but neither so effectively nor so
rapidly as the green colouring matter; and it is not
unlikely that the green pigment, which is perhaps the
most economic machine that life has evolved, was
only perfected after the simpler yellow tools had long
been tried for the production of food from inorganic
sources in air and water.

In the lower plants the red and yellow colouring
matter is related to the accumulation of fat and oils,
which are stored in the seeds or spores. Similarly, in
the carrot, the huge reserves of fatty materials col-
lected in the roots are accompanied by a dense forma-
tion of yellow pigment, and in the eggs of animals the
same relation between yolk and pigment is clear.

So constant is this association that these pigments
have been called fatty pigments, and stand in some
sort of relation to the nourishment of the young,
whether plant or animal. But until recently the
nature of this relation was entirely unknown. The
results of some researches on the pigments of prawns

FUNCTION OF FATTY PIGMENTS 163

have, however, suggested that they possess a definite
nutritive meaning.

In these animals the colour of the skin is due,
as we have seen, to minute stellate masses of such
substances. These mobile pigment-stars form the
‘chromatophores.’ But not only is the skin thus inter-
spersed, as it were, with pores, from which the pig-
ments overflow into channels or into which they retire,
leaving the channels clear and colourless, but a similar
system of pigmented holes and crannies traverses the
muscles, the digestive system, the nerves, and the
eyes. The whole prawn, in fact, is bathed within by
pigment veinings. Along the courses of these channels
lies a second series of tubes that contain, in green
specimens, minute grains of colourless fat, and if the
prawn be starved and kept in the light the fat does
not disappear. ,

If, on the other hand, both food and light are
excluded, the prawns, having exhausted what food
they had to start with, absorb pigment and fat also ; and
if such lean specimens are taken out again into the
light at the end of a fortnight, they will in the course
of a single day show not only a fatty skin, but a far
denser accumulation of fat than is to be seen in a
fresh-caught prawn. This result points very strongly
‘to the conclusion that the red and yellow colouring
matters, even of such highly organised animals as
prawns, are, as in some plants, able to form fat out of
its simple elements, and are, therefore, no mere deco-
ration, but factories, under the shade of which the

M 2

164 ANIMAL LIFE

demands of the body for nourishment and of the eggs
for yolk, which cannot be completely met by the usual
food, are satisfied.

The colour of the prawn may thus have nutritive
value, though naturally of a lower order than that
of the food taken in by the mouth and elaborated
in the passage through the tissues.

The multitudinous minute collections of pigment
or chromatophores that star the skin and the interior
of the body form so many rudimentary elaborating
machines, independent of the digestive system, and
differing from it in being able to construct and distri-
bute a fatty substance under’the influence of coloured
light.

Whether this double mode of nourishment is
widely spread amongst animals is not as yet ascer-
tained ; but we know that it is extremely difficult to
prove, and for this reason—skin-nutrition is a mere
vestige of an old process that has been supplanted by
the more modern and efficient one of nutrition by the
digestive system. The collections of pigment, under
whose egis it operates, are somewhat like the buttons
on our coat-sleeves, the silent letters in words, or the
muscles of our ears—relics of a time when ruffles were
worn, when those silent historians were vocable, and
ears, hairy and pointed, twitched.

Nature throws nothing away, and in many a secret
drawer preserves documents, yellow with age, that
hold her past history. Here and there she still uses
the old parchment, an ancient recipe to guide the cook,

COLOURS OF FATTY PIGMENTS 165

but for the most part employs a newer and more
elaborate method.

But if the plant-like method of elaborating food
from air and water has fallen with animals into disuse,
the connection between these old yellow and red pig-
ments and nutrition is still an intimate one. We have
seen that where fat is formed such pigment is fre-
quently, in prawns always, present, and we can now see
more significance in the alliance of pigment with fat
formed out of food on the newer plan of the digestive
system, and accumulated in the skin, muscles, liver,
and eggs. :

Nothing is more common than for oil to assume a
yellow colour, or for the seed-coats of some plants or
the tubers of others to become yellow or red. In the
majority of such cases the colour is unessential, and
neither concerned in the formation nor accumulation
of the stores.

But as a hint of the part which these ochreous and
rufous pigments played in these processes ages ago we
have a suggestion of the utmost value, of a former
utility, of the need for an historical grip on the facts of
nature before their significance can be even imperfectly
appreciated.

From such a broad survey of the green, yellow, and
red pigments of plant and animal we acquire a stand-
point from which we may view the colours of animals
in a new light; not sufficiently high to enable us to
see to the boundaries of knowledge nor to determine
with equal clearness foreground and background, but

166 ANIMAL LIFE

at least better than standing on level ground and view-
ing the occurrence of colour as a miscellaneous and
unrelated display.

We see that yellow is a sort of ground colour, from
which the red blood-pigment emerges as a later wash.
To the former we attribute a nutritive value; it is
the harvest colour. To the latter a fiery touch ; it is
the carrier of oxygen and the seat of life.

~Movement, that significant attribute of animals,
has obscured the meaning of the one and increased
the value of the other. By creating appetite and
capacity, activity has demanded more nourishment
than the yellow pigment could produce, and move-
ment has annulled that stationariness and exposed
habits that favour its synthetic power in the presence
of light, and in general we only see such yellow pigment
in the inward parts of animals.

The red colour of blood has likewise fled the surface
and become an internal pigment, bringing the air from
the skin, lungs, and gills to the tissues of the whole
body.

On the bare surface so created painting has been
done by a later hand, and with old pigments worked
up into new combinations.

The blood, for instance, is worked up into reds
and browns; from the liver come the green pigments
that we recognise as biliary accomplishments ; and
even from remoter and baser organs colouring matters
are formed. ;

We know that the skin possesses an eliminating

C—O ee eee eee, ee

EXCRETORY PIGMENTS 167

power, that arsenic, sulphur, and gouty phosphates
are transferred from the deeper to the more super-
ficial parts of the body; and the more insight we gain
into the colouring of the skin, the more clearly do we
_ see that it is the seat of purification, in consequence
of the complexity and bulk of the animal body.

White butterflies owe their white and yellow colours
to one of these ‘excretory’ poisonous substances,
and the silvery whiteness of fish is due to a similar
though harmless substance. Thus it comes about that
similarly coloured pigments are not necessarily of
similar nature. The yellow butterfly, the tiger, and
the frog contain three different substances, and we
have to apply tests before we can separate the old
historical yellow of the frog from the later and
derived pigment of the tiger and fly.

It is to these three functions—nutrition, respira-
tion, and excretion—and to nutrition first and fore-
most, that the pigments of animals owe their origin.

_In each case the original significance of the pig-
ment may be lost, and a later and apparently merely
decorative one be attained. To the study of skin-
painting and surface-colouring much has yet to be
contributed before we can, as it were, restore the
colouring and realise the design. But in such a quest
nothing is insignificant, and he who can explain freckles
will solve one of the most baffling problems of human
or bestial colouration. |

The Secondary Meanings of Animal Colouration.—
Having thus obtained a grasp upon the meanings

168 ANIMAL LIFE

and physiological significance of colour, we may
consider its modifications. Harmony with the varied
conditions of existence is the note of animal life.
The adaptations of colour to serve ends beyond
those of nutrition and respiration form part of that
general harmonious relationship between animals
and their environment. |

Amongst these adaptations none are more striking
than the sympathetic colourations of animals. With
but few exceptions, amongst gregarious species, the
attitude and colouring of animals renders them in-
conspicuous.

Those which rest for long intervals reflect, as it
were, the light and shade, as well as the colouration
of their habitual surroundings. The tiger’s stripes
sympathetically render the lights and shadows of
jungle grass, amid which it lies concealed a whole
day. The giraffe’s dappling and the deer’s spots give
back the sun-images and leaf-shadows that filter
through the foliage. The skate and turbot, sole and
shrimp, are speckled like the ground on which they long
rest, motionless. The skin becomes to all appearance
a sensitive plate, upon which, as by a process of colour-
photography, is imprinted the general tone and tinting
of the surroundings. So sensitive do prawns and
other sympathetically coloured animals become that,
if given a choice of station, they do not rest until they
have adjusted their dark areas to the shadows and
their bright spots to the shafts of light. But once
having accomplished this, they remain still for a long

_ —— a —_

COLOUR-VARIETIES OF HIPPOLYTE 169

interval. The sop prawn (fig. 29) of our coasts
makes this adjustment with the greatest nicety,
and for this reason is not so easily seen nor so widely
known as the restless edible prawn. Its pigmenta-
tion recapitulates the descending colour-scale of the
seashore. Green, brown, and red, the notes of the
upper shore, of the lower shore, and of deep water are
struck by this Hzppolyte as we find it on sea-grass,,
tangle, or ruddy weed. Seated motionless, and almost
invisible, it reproduces not only the colour, but also
the pattern of its background, and, according as the
light is more or less broken up by the bushy or leaf-
like form of these sea-forests, so does the colouring
of the prawn exhibit marbling or uniformity; and
as there is an infinite variety of colour gradation
in this water-foliage, of which green, brown, and
red are but the most salient tints, so does the
livery of the prawn vary through the whole gamut
of the spectrum from red to violet.. If a collection
of such motley be gathered together and supplied
_ with a choice of varied weeds, each after its coat
will select its colour harmony and vanish as if by
magic.

With a renewed sense of the fitness of things the
eyes and the mind of the observer rest contented
upon this sympathy of colour between animals and
their surroundings. Such orderliness has a special
power to arrest the attention. The policy of bees or
the flight of birds is scarcely a more finished perform-
ance. But the spectacle of such harmony has not

170 ANIMAL LIFE

produced its full effect if it permanently arrests the
mind and holds it at gaze.

The prawn in its motley is but one of a thousand
instances of colour sympathy, and leads us to inquire
and experiment upon the mode and material that
effect such adaptation, and to judge of its value as
a contribution to the enjoyment or more material
needs of the animal’s life.

It is not only as a symphony which can transport
us, without our distinguishing the orchestral elements
or the art ruling the composition, that we can view
the triumphs of animal life. An artistic mind is,
indeed, essential to receive the effect, distinguish its
causes, or perceive its relations to other and humbler
displays. But biology is essentially human. Of its
stuff we are made. That which has gone to make its
triumphs—both soldiers and generalship—has gone to
make ours. To view them is to see no merely pleasur-
able spectacle, on which the mind can rest without
moving to its analysis. Our curiosity, once set work-
ing, discovers that what we at first see is but one view
of a kaleidoscopic drama, and finds a new sense of
camaraderie in similarity of forces and tactics that
have won positions for animals and for us.

Viewed in this light, the manner and meaning of
harmonious motley possess a wider significance than
we at first attribute to it.

All the colours of which the sop prawn is capable
are due to three pigments—red, yellow, and blue.
By mixture or suppression of these three the varied

ORIGIN OF COLOUR-VARIETIES 171

compound or simple colours are produced, and, as we
have seen, the basal pigments—red and yellow—are
related to a colouring that, either external or internal,
is a thread binding all classes of animals and plants
together, and leading the mind to that ancient nutritive
significance which such pigments possess. In the
case of this prawn that nutritive value is especially
clear. As we can assign to the colouring matter
and the light-position of the seaweed their several
parts in the production of plant food, so to the similar
colour and equal immobility of the prawn we can
attribute a corresponding though lower economic im-
portance ; and the causes that have favoured the green
colour of sea-grass have been also active in producing
the green colour of the prawn that rests thereon.

Yet with such sapient conclusions we are not
content. Animals are by nature active creatures, and
the spectacle of a prawn thus vegetating and growing
into its surroundings pricks the mind to ask how the
process works. Does a green prawn give rise to green
young, and a red prawn to red young, or is there no
hereditary bias in favour of any one colour, and the
matter left to the choice of the children? And how
comes that banding and dappling which fits the prawn
to its weed ? The answers to such questions are slow
in coming to a satisfactory fulness, though already
much is known. Azppolyte issues upon life not in the
image of its mother, but as a minute colourless creature,
with none of the walking legs it will afterwards possess,
and provided with swimming limbs and a flexible tail

172 ANIMAL LIFE

a
d
j
{
D
:
,

|
;

that fit it rather for drifting upon the open sea than
for arboreal life. Upon close examination the absence
of colour is seen to result not from absence of pigment,

Da NG

ue
ave /

Fic. 29.—TIllustrating the Development of Colour-pattern in AWzpfolyte.
The uppermost figure represents the free-swimming larva. The
middle figure the adolescent stage, when it settles on its weed. The
bottom figure represents one of the many colour-varieties. The black
spots represent the chromatophores (caudal, visceral, and neural).

but from its poverty; and if a sufficiently strong
magnifying power be used, a whitish or greenish tint
will be observed. In this respect all families of this

DEVELOPMENT OF COLOUR-PATTERN 173

prawn agree, however different may be the colour of
their parents. At birth, therefore, Hzppfolyte has no
hereditary bias towards this colour or that.

After a life of some days spent offshore among
the flotsam of the sea, the young Hippolyte, still
transparent and almost colourless, is carried inshore,
and attaches itself to the first thing that comes handy.
If in deep water, the holdfast will be a red weed; if
within the tidal zone, it will chance upon one of the
many variegated bushes that clothe the rocks; if
among the tangles and dense Fucus, a brown weed will
be the likeliest anchorage.

On whatever hold it chances the young animal
will stay, partly to feed, partly to avoid dislodgment and
death by the surf. At this stage its skin is of a great
sensitiveness. Experiment shows that if two com-
panies of such colourless young Hzpfolyte are supplied
respectively with contrasting weeds, each will assume
the corresponding tint in a day, and the colour so
formed will increase in intensity until the match is
complete. |

So on the beach, as the light filters down to where
the young Hippolyte cling like stranded mariners
to the slippery rocks, the prawns respond to the
colour of their environment, and before a week is
over the resemblance is complete; and should a gale
or a low spring-tide set them moving, they will not
be long before selecting cover that corresponds with
their coat. All have the colour-scale before them,
and their choice is made at the start of their career.

174 ANIMAL LIFE

Their youth, like that of higher animals, is shaped
by early impressions, which come with a force and are
responded to with an alacrity that diminish in later
life.

Across their sensitive, transparent skin a shadow
falls. Scattered over the body, some pigment, in-
significant save under a microscope, is present, and
in the shadow’s path this pigment undergoes a change.
By a rule of behaviour that governs the expansion
of pigment into interwoven skin-channels, or its
contraction into pores, the shaded pigment will
expand and darken that area of the body. Further,
as exercise favours growth, so does this expansion
of pigment seem to induce increase in its amount.
Between the existing dots of colour new ones arise,
the bar thickens and in a few days reproduces the
shadow in tone.

Thus we can trace the influence of light and shade
in preventing or favouring the development and
expansion of skin-pigment in HAzppolyte, and in
thereby producing that sympathy between the prawn
and its surroundings that afford it such wonderful
concealment.

The development of the colouring, as well as of
the light and shadows, at this critical phase is less
well understood. We know that the red and yellow
pigments are older than the cryptic colouring they
produce; that their value as nourishing, if not also
as respiratory, mechanisms explains their presence
and antedates this merely decorative effect. But by

ORIGIN OF COLOUR-PATTERNS 175

what process they are so laid on, toned, and mixed it
it difficult to understand, save on the analogy of a
natural photographic process of colour. There is
known to physicists a mixture of silver-salts so sensi-
tive to light that it is decomposed thereby, and acquires
the colour of the rays that fall upon it. By its aid,
though at an expense prohibitive to commercial
success, a geranium can be reproduced in natural
colours, and it may be that some similar composition
underlies the skin of these prawns, and undergoes an
orderly disarrangement when scattered or evenly
diffused and coloured light falls upon it.

But the skin of the prawn is no mere chemical
mixture, nor does light act upon it only as on a sensi-
tive plate. It is a highly nervous structure, which is
affected both by the sight of the eyes and by the rays
that impinge directly upon its surface. The processes
of pigment formation and pigment distribution are
regulated by the nervous system, acting mainly through
the eyes. Permission, as it were, is given or withheld
for the development and amount of the several pig-
ments, their close-set or more open texture, and for
the pattern which they must follow. As a skilled
painter almost unconsciously lays down the ground-
work of his sketch, manipulating the purity and
mixture of his colours, controlling them by eye, and
painting in the high lights against a body colour, so does
the eye of the prawn unconsciously supervise the
painting of the surrounding scene that unseen hands
are rendering, both in relief and colour, upon its own

176 ANIMAL LIFE

skin. As there are certain rules of composition in
painting, certain old proprieties to be observed, which
taste has evolved and custom obeys, so there are
certain lines along which the skin-painting of the
prawn begins; certain areas along the back and
breast and across the body along which the invisible
hand first works before filling up the canvas.

In such a fashion the resemblance between the
prawn, Hippolyte, and its surroundings is produced.
Its pigments, primarily organs of nutrition, and still
subserving this function, are controlled both from
within by the nervous system and from without
by the light. So long as the larval Hippolyte drifts
from place to place through the offshore waters there
is no contrast of light and shade that can effect any
continuous action; when the tide carries it to the
shore it is as a still, colourless, week-old, tiny prawn
that it clings to the first holdfast. But once it comes
to rest in the submarine forest the contrast of light and
shade begins to work a sea change. Its pigments
develop, watched over by the eye, encouraged by
shade, discouraged by brightness. First along certain
tracts that form the easily followed lines of composi-
tion, and then filling up the shadows, leaving the high
lights to render themselves by untouched canvas,
or at most by a sparing use of yellow and white, Hippo-
lyte is all unconsciously following the best traditions,
and unwittingly, Ulysses-like, making itself a part
of all it encounters.

Beyond the power to follow a helpful traditionary

SYMPATHETIC COLOURATION 177

outline by a meagre supply of red pigments, each larva
Hippolyte issues on the world unaided. It is a born
artist, but without any bias that leads it to adopt any
style of painting, save that which its first and succeed-
ing stranding-places suggest. Such struggling genius
has met with success. Our coast forests are thronged
by invisible prawns, seated on bole or branch, and
coloured in sympathy therewith. Restfulness is their
mark, that receptive attitude in which the cryptic
artist receives and embodies the messages of light
and shade that fall around him.

Nor is Hippolyte the only nor even the best
known case of sympathetic colouration.

Among some sea-forests live a multitude of other
creatures hardly less harmoniously tinted. There are
sea-spiders whose colour varies with the weed upon
which they rest ; the cousins of the jumping beach-
flea, whose bodies reflect their roosting-places down
to the minutest detail; the pipe-fish, whose shape,
colour and swaying movements make him a part of
the sea-grass: the male of which carries the eggs
under his body, as though to mimic the flower of the
grass. Under the broken lights of sea-tangle young
cod, pollack, and a hundred other varieties may be
passed unnoticed, so well does their chequered skin
harmonise with the light and shadow.

On the sandy shore, away from the rocks, we find
a similar avoidance of contrast, a colour sympathy
between the sand-dwellers and their resting-place.
The dabs and shrimps, the dragonet and goby, the

N

178 ANIMAL LIFE

skate and turbot, the predaceous and the preyed upon,
have adopted the livery and tone of the sand. Nor
when we leave the sea and follow the rivers do we fail
to discover some instances of a similar agreement
between the colour of fresh-water animals and their
surroundings. In particular the trout, like all fish
of sedentary habits, exhibits this sympathetic relation,
and becomes light in chalky streams or limestone rivers
and dark on a peat bottom or in deep holes.

But that abundance of invisible, and yet boldly
coloured animals which the sea possesses is notably
absent from fresh water, and if we pass from fresh
water to the land we find but few instances, except
amongst birds and insects, of that intense colour
sympathy which characterises the shore.

Of general unobtrusiveness there is plenty, for
shade subdues all colour to itself, and the motley of the
ground makes any small object inconspicuous, as a
variegated carpet makes a better hiding-place than a
self-coloured one. But of that careful rendering of
the habitual resting-place which Hzppolyte has per-
fected there are far fewer instances as we pass from
the sea to the land, and it is only where conditions of
a very decisive colour dominate a countryside that we
find anything comparable with the clear mark of
sandy ground or the bold yet cryptic motley of the
rocky coast.

In our own country this can hardly be said to occur,
and we turn to the white Arctic regions, the brown
deserts, and green tropics to inquire whether bold

ARCTIC COLOURING 179

deception rules there as in the sea. The white colour-
ing of the polar bear, Arctic fox, of the gulls and terns,
seems at first sight an admirable case of sympathy
between scenic and animal colouring. But, strictly
speaking, white is not a.colour so much as the sum

Fic. 30.—Female Orange-tip Butterfly (Anthocaris cardamines) on the
wing (A) and at rest (B), to show the sympathetic colouring of the
under-surface.- -(Copyright, C. D. Head, Dublin.)

of colours; it is due not to a pigment, but to the
covering of the body with a coating of air-bubbles—
a froth in the pelage or plumage—that reflects the light
and confers additional warmth by acting as a non-

conductor. The resemblance, therefore, of many Arctic
N 2

180 ANIMAL LIFE

animals to the snow and ice may not. prove to be one
of sympathetic colouration, but to be a part of that
more embracing harmony between animals and their
surroundings of which the cryptic colour resemblance
is a subsidiary and often a negligible factor. The
Arctic raven, which is black all the year round, is as
sufficiently adapted to its mode of life as the fox
or bear, that more habitually live amongst the snow
and are so well screened from observation by their
white colour.

With the desert it is otherwise. The prevalence
of tawny colouring among its beasts and birds, reptiles
and insects is a parallel to the speckling of sand-
dwelling fish in shallow seas. The lion, no less than
the sand-grouse or sand-fly, bears the Ishmaelitish
mark—a dun colour, relieved, if at all, by a speckling
or shading that melts into the body colour.

Enforced stillness during the heat of fhe day has
given ample opportunity for the working of the soil
upon the eyes and skin of desert creatures. The
dominant pigment, yellow, of such hoary antiquity
and unexpected usefulness, has received a new impetus
to its development from the match which it affords
to the tone of the ground.

In the forest and field, animal colouration is largely
‘pictures of shadow under foliage, with delicate
patterns of vegetation and flowers drawn across it.’!
The partridge, grouse, woodcock, thrush, and snipe
show this. Still more strikingly does it appear in

. Thayer.

ae ce

‘PICTURES OF SHADOW UNDER FOLIAGE’ 181

the striping of zebras and forest antelopes, of tigers,
the sun-spots of fallow deer, the mottling and striping
of squirrels. But such a generalisation can only be
grasped by analysis and observation. In the field, as
by the sea, two types of sympathetic colouration occur.
One, sympathetic par excellence, reproduces the adjacent
background of those animals that crouch, as moths,
caterpillars, goat-suckers, woodcock, partridges (fig. 31).
The other, conventional, represents in a bolder manner
the more prominent features of their habitual sur-
roundings; to this class belongs the tiger, the zebra,
and, in a special manner, the butterflies.

The effectiveness of this animated painting in either
class is increased by a mode of shading from top dark
to under light, known to artists as effacing gradation ;
the white breast gives the finishing touch to this result.

The American artist, Mr. Thayer, has pointed
out the significance of this gradational colouring.
A monochrome, especially a dull monochrome, is
the only revealing colouration, and we find few
animals (ravens and the rook family; gregarious
animals, as sheep, oxen, horses) of this type. If we
break up the mass, say by tying white ribbons around
a dun pony, a partial effacement is produced, and in
rapid movement or in moonlight the broken mass
melts into grey as the succession of contrasted belts
of colour neutralises their individual effect in crossing
the field of vision. .

But in a good light such strong, ungraded lines
increase the rotundity. The shadow deepens round the

(*wanasnyy sajseyouvpy ay ue sures mo4y)—'sSuIpunoxMs [emyeu
sSuouly usas Udy UONvINO[OO ONayiedurs jo asvo poos W “Sunoy pur aspuyavg uszy—'if ‘org

EFFACING COLORATION 183

projecting ridges, the flanks, the belly, and the face,
and throws up the animal against the background.
A rough clay-bird model is, owing to these lines of
rotundity, clearly visible a long way off. But if we
balance the shadow by painting those parts white
in proportion to the depth of shadow, the result is
an effacing gradation, z.e. the white breast melting
gradually into the flanks. Such a bird is invisible at
a few yards.

The same principle that applies to the mass
applies also to the shading of separate patches of
colour. A striped creature is thus rendered trans-
parent, as it were, when at rest, and a_grey, evasive
patch when in motion.

But there is no need to search beyond our own
country for examples of sympathetic colouration
among land animals. Insects carry all their under-
takings to a high degree of perfection, and there are
no closer resemblances between animals and _ their
surroundings than are to be met with amongst cater-
pillars. The stick-caterpillars, for example, in form,
posture, and colouring resemble so closely the branches
or thorns of their food-plant that they can only be
distinguished with great difficulty. Clasping a twig
with the strong hand, into which the tail is modified,
and supporting the head by a transparent girdle,
they extend the body at the proper angle, stiff and
straight.

Their skin, dark and gnarled, resembles to a nicety
the bark of the surrounding twigs ; and the resemblance

184 ANIMAL LIFE

is further heightened by the stumpy legs of the cater-
pillar, which recall the irregularities of the twigs. In
some cases the colour varies, so that, as in Hippolyte,
light and dark, plain and variegated forms of the
same caterpillar are found, in each case agreeing
with the colour of the foliage and the markings that
occur upon it. In such sensitive larve the same
influences are at work in producing the sympathetic
colouration as are active in calling forth the agreement
between the colour-varieties of the prawn and its
weed. In both cases a dim light encourages the
development of pigment and the formation of a dark
variety ; a bright light has the reverse effect; but in
the caterpillar the change takes place more slowly,
and is less controlled by the influence of sight than
in the prawn. In both it is the early stages of develop-
ment that are chiefly and most rapidly susceptible
of modification by the light reflected from their sur-
roundings, but whereas this power persists throughout
the life of the prawn, it is lost and the colouration
rendered permanent before the caterpillar has attained
its full size.

Amongst butterflies and moths there are many
instances of the same sympathetic or cryptic coloura-
tion. Obvious as these animals are upon the wing,
they often disappear as if by magic when they come
to rest. The buff-tip moth rests motionless by day
upon tree-trunks, and the yellow patch at the tips of
its forewings looks precisely like the coloured end of
a broken twig. The hair-streaks, which often hover

ES an

LEAF-BUTTERFLIES 185

in a cloud round some ash-tree in May, cannot be
distinguished from the leaves when they settle, and
fold up their brown wings so as to display the green
under-surface.

More impressive still is the resemblance between
the leaf-butterflies of India and the dead foliage
amidst which they habitually rest. Seen in flight,
nothing could be more obvious than the purplish
brown wings flapping slowly and uncertainly in the
clearings. Seen at rest, nothing distinguishes the
insect from the leaves around it. The wings, folded
vertically, form a lanceolate area, produced by little
tails into an apparent stalk. Down the centre runs
a midrib with branches and veinings. In colour
the rusty brown of a dead leaf is exactly reproduced,
and, as if to carry the resemblance to perfection, the
holes and even the worm-eaten appearance of a leaf
is given in the butterfly’s wings by clear spots and
irregular markings. No single detail of form, posture,
or marking is lacking to make the agreement com-
plete. The stick and leaf insects of the tropics carry
out faithful representations of twigs and green foliage.
So close is the resemblance, so motionless the insect,
that the very elect of ants are deceived, and fail to
discover in the insect actually underfoot any signs
of that nourishment they so eagerly search for and so
rapidly devour. The mantis, or praying insect, goes
beyond all others in its elaboration of floral designs.
Its head and three joints are decorated with flat
leafy appendages of some bright colour, white or pink,

186 ANIMAL LIFE

whilst the rest of the body is dark green. Taking up
their position in the full glare of the sun upon some
similarly green bush, they draw up the legs so as to
produce the illusion of a flower. There they remain
motionless for hours, and may be seen week after
week in the same position. As the time arrives at
which the natural flowers around them fade, the
mantis, too, slowly fades in colour, descends the bush,
and, like a discoloured bloom, lies to all appearance
helpless and fallen.

Spiders are not behind insects in their power of
sympathetic colouration. Immobility is emphatically
characteristic of them, and has played a considerable
part in the production and rendering of the cryptic
resemblance.

We may now ask what purpose is served by this
widespread sympathy of colouration between the
animals of land and sea, and the texture and tinting of
their resting-place, or of their associates. The answer
that has become almost an unthinking response—
protection—is one that came to Darwin as a flash of
light, illuminating the meaning of all those devices
which seemed otherwise mere freaks. The great
naturalist, handling these unrelated facts of nature,
saw in the struggle for existence, the search for food,
the evasion of enemies, the maintenance of self and of
one’s family, a strain that tasked the resources of
living things and gave a tragic significance to all
their life. Unconsciously and intermittently the best
adapted, the more flexibly organised were rewarded

mest

PROTECTIVE VALUE OF COLOUR 187

by the possession of the earth. By their very enter-
prise they created competition, as in commerce to-day.
By the tendency of all living things to increase in
number beyond the means of subsistence the weaker
were ousted by the stronger. Those better fitted to
endure hunger or lack of air, cold, or heat, those
that could escape at such hard times to more genial
surroundings and hold their own against its occupants,
were favoured, and their offspring again selected by the
same process.

Sympathetic colouration, viewed from this stand-
point, became a means of concealment from prowling
foes, or of lying in wait to surprise and capture unsus-
pecting prey. The stick-caterpillar, from being a
mere freak of nature, became a test-object for a
definite experiment ; and Darwin, never satisfied until
he had raised a point of view to an assured conclusion,
tested the value of his hypothesis by bringing such
caterpillars, both singly and on their food-plants,
into an aviary. The result was encouraging. The
birds greedily devoured the isolated caterpillars and
failed to find those on the plants.

More recently the same experiment has _ been
carried out with mantis. Two varieties, brown and
green, were chosen, and forty of each variety attached
in open ground by a similarly coloured thread to
plants of sympathetic and contrasting tints. At
the end of a fortnight all those which had been tied
to plants of a colour similar to their own were well
and vigorous, while those contrasting with their

188 ANIMAL LIFE

surroundings had been eaten, chiefly by birds. Again,
it was found that where an animal, such as a wasp
or white butterfly, was boldly and aggressively coloured
it was often rendered comparatively immune to
attacks by some odour, taste, or sting. The gooseberry-
moth, caterpillar and chrysalis are barred with
black and yellow, and display their colours with as
much zeal as the wasp, and like it are distasteful.
The dominant Danaid butterflies of America and Africa
have an acrid taste, that is their defence, and they
display by bold, unmistakable colouration the warn-
ing of nauseousness, Further, it is by sailing under such
colours that a harmless and edible butterfly might gain
security. Such is the case. The marvellous instances
referred to in Poulton’s work (p. 189), of similarity in
habit and colour between dominant butterflies and
their masquerading associates, are explicable when we
realise how instinctive the avoidance of such warning
colours has become. Yellow and black, black and
white, are danger signals, and give notice of con-
cealed poison. Such new significance thrown upon
the warning colouring of animals served to heighten
the protective value of sympathetic colouration.

Such results have led observers to seek in protec-
tion the entire significance of cryptic colouring: to
regard the avoidance of enemies or the near approach
of prey as the reason for its existence; whilst to
those who are not close observers the general vague
. resemblance between animals and their surroundings
is illogically regarded as explicable for the same

SECONDARY VALUES OF COLOURS 189

reason. But if we look back on the history of animal
colouration as we have attempted to sketch it in
the preceding pages, we realise that the pigments
of animals are older than the effect they produce, and
that the old nutritive, purifying, and respiratory uses
of colour are the basis for the more recently evolved
protective, warning, or mimetic values of colouration.

Impressive and important as those values are, they
could not have been achieved unless there had been
a sound constitutional basis to underlie their working.
Like some youthful prodigy who startles the world by
his violin-playing or reviews, the facts of protection
seem created to produce the results that so impress
us. But as the artist works through the aid of a
constitution that ages of unregarded, serene toil have
bequeathed to him, so the mimetic butterfly or prawn
has produced its effect through the aid of processes and
by the use of materials that its ancestors utilised for
their more ancient ways of life.

REFERENCES

Newbigin, M. ‘Colour in Nature.’ Murray.

Poulton, E. B. ‘Colours of Animals.’ Inter. Sci. Series,
vol. 68.

Darwin, C. ‘Descent of Man.’ Murray.

Thayer, A. H. ‘Protective Coloration.’ Trans. En-
tomolog. Society of London. 1903. P. 553.

190 ANIMAL LIFE

CHAPTER IX

THE WELFARE OF THE RACE

Tue life-history of an animal or of a plant is not
only the record of its maintenance, growth, and de-
velopment, but also furnishes the seed of the future.
The welfare of the race is an inward stimulus to which
all beings respond. The endowments of the individual,
which have at first sight such an appearance of being
purely personal acquisitions and advantages, are
in reality of racial value. In animal life the heritage
is one of bodily structure and instinctive habit.
Man, beyond these, ensues an estate of social and
ethical qualities ; the maintenance and extension of
this kingdom constitutes his most absorbing task and
awakens him to the highest influences.

This true affiance is the supreme example of an
election between a being and its choice that runs
through animal and plant life. It is personified in
the higher animals by the love of mates, in which
they gather all their gifts to pour them into the lap
of the future.

From the lowest to the highest this debt is paid
with unwavering response, and is the crowning act of
their life. The individual Protozoon literally loses

ee

SELECTION OF MATES IgI

itself in its offspring, and many of them thereby have
never lost an ancestor by death. All their lifetime,
until this unique response is made, the immortal
animalcule has safeguarded its balance. It has
never worked up to its breaking-strain. Like all
living things, where their own maintenance and
_ growth are concerned, it has practised reserve. But
now, when they are to be reincarnated in their _ off-
spring, every consideration is abandoned that should
prevent the full inheritance falling to their children.

This bountiful provision for the future is rendered
still stronger and healthier by the difficulties that
are placed in the way of a suitor gaining the hand of
his desired mate.

The difference between mates is apparent, and
even striking, in nearly all animals. Agility, beauty,
and strength are usually the prerogative of the
male. Intent on these possessions, he is the type of
the egoist, of the luxurious drone; and it would
seem as though, for thousands of such spoilt children,
these gifts were sheer vanities, satisfying only the
insatiable hunger of their possessor. The splendour
of the birds of Paradise are the love-locks of the cock
bird. The finest plumes of birds are invariably the
ornaments of the male sex, and in most winged and
active animals the male appears rather an ornamental
than a useful member of society. In many cases
his life is one of the airiest and shortest. Though
exquisitely formed and sensitive, and with powers of
flight that his mate cannot equal, he rarely takes

192 ANIMAL LIFE

food, but dances with his fellows, shaking a loose leg
over the ground where his partner is hard at work. In
such style the male gnats drift over the countryside
in short outbursts of marvellous activity, whilst the
females alone seek to bite us, haunt our water-butts,
and roost in the outhouse. So the male ant and
bee drone is but an annual incident in the life of the
queen, and almost the whole life of wasps is one of
joyful widowhood. Why should such bounty be
showered on the drone if it is only to endure for an
instant in his mate’s sight ? Why should he be spared
the duty of finding food when her whole life is given
to dispensing it ?

The answer we can now give is a strange one.

The foolishness of the male is the wisdom of the
race, and his ardours, seemingly so self-centred, are
an assurance of a test survived and of promised pre-
eminence. Disguise the fact as he may, he still is
responding to the utmost of his powers to secure the
fittest offspring, though with the momentum that
is put into the decisive acts of life he is carried past
the point of utilitarian necessity in a short outburst
of exuberance, as if to conceal the test he has passed.

The most general ordeal is the old courtly tourney ;
that is, the males do battle in view of those whose
favour they strive to win.

With spiders, for instance, the court is held in
summer, when the suitors are in their brightest and
most vigorous mood. The rivals, after eyeing each
other, and then closing in what appears a mortal

SELECTION OF MATES * 193

combat, ultimately separate, not a limb the worse,
though with an understanding, no doubt the original
conviction, that one is superior to the other. The
victor now performs the most striking advance in
order to impress yet more fully his desired mate with
a sense of his beauty and prowess. With his forelegs
extended upwards and his tail elevated he advances,
and then in front of the mate he seeks, performs
a frog-dance alternately with his right and left foot,
displaying most fully thereby any striking marks or
peculiarities that he possesses.

But the lady’s choice is not at once made. Usually
a second suitor is allowed to perform his approach
and love-dance, and only then is the match made.

In such cases the chosen mate is, even to our
eyes, the more glorious, and by virtue of such choice
the spider obtains a peculiar advantage by at once
setting up house. She gains not only the most
vigorous mate, but the first choice of site and an
early supply of the juiciest flies. The male spider,
meantime, having accomplished his fascination, dies
in the course of a few days, or falls a victim to the
ravenous hunger of his larger mate.

Some such test of beauty, strength, or agility
most suitors have to pass. The stag does battle with
his fellows through the October nights, and when the
strife is over the victor is acknowledged as lord, both
by his disappointed rivals and by his herd. The bulls
of many animals test their strength by battle. In
such fashion many seals are maimed before the strongest

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MATING DANCES 195

is awarded leadership and wins his mates. The cock
birds of our fowls and pheasants choose remote
places in the jungle for their contests. The ruffs
assemble on the Dutch marshes each spring to perform
complex dances and flights before their rivals, and in

Pa 33. _7 he Ruff i in panne plumage.
(From a specimen in the Manchester Museum.)

view of the reeves or hen birds. Only after the
fullest display of their plumage, powers of flight and
of song is the choice made among them. Indeed,
we may say that where the cock bird differs from the
hen in plumage, such contrast is an indication of the

O02

196 ANIMAL LIFE

fierce competition which the male birds have to engage
in before they can claim their mate, or even advance
their suit with success.

Among fish the test by battle is, so far as we know,
less common ; but in such cases it seems probable that
either we are not sufficiently familiar with these

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Fic. 34. —Black Cock showing off his attractions before the Grey Hen.
(From specimens in the Manchester Museum.)

creatures to detect the withdrawn and passionate
episodes of their lives, or we find reason for believing
that another test, not less rigorous, is interposed.
There are, however, certain cases amongst fish where
a display similar to that of cock birds is executed by
the male fish before the females. The dragonet
affords a good example. In this common but

SELECTION AMONGST DRONES 107

inedible fish the male is striped and spotted with
blue on a yellow ground, whilst the female is of a
mottled, sandy colour. The male’s livery, however, is
made far more conspicuous by the erection of a large,
brightly coloured dorsal fin, and by the rapid move-
ments that display this attire from every point of
view. There is no actual battle, but the hen fish
delays her choice of mate until the display has been
repeated many times.

Amongst insects the powers of the drones are
severely tested before their suit is accepted. Types
as they are of luxurious living, they act at least once
with a strenuousness and passion that no other animal
surpasses. Before the queen bee accepts her mate
he is but one of a crowd, compelled to make a flight
with her and a swarm of attendant workers far up
into the sky, and in that ascent one, and one alone, is
victorious. What tests he has stood that others failed
in we know not; we do know that success means
death to him and the massacre of the remaining
drones by the workers.

A similar mystery envelops the habits of ants.
In their nests few drones are found, and only for a
short season. Some warm day in August the entire
country is filled with the nuptial swarms that, acting
under some influence to which they concertedly
respond, rise up in streams from the ground and drift
over the countryside, descending on mountains and
down chimneys, on house roofs and rivers. On that
day the drones pass or fail in their ordeal, and, having

198 ANIMAL LIFE

accomplished their descent, victors and vanquished clip
off their wings and die. |

Butterflies exhibit a similar, though apparently less
severe, selection of their mates. Entomologists well
know the attractive influence that a single insect will
exert over a whole district. By confining a female
moth in a wire cage they find that in some strange
manner males of that species, even if uncommon or
rare in that district, will discover the captive, assemble
round her, eagerly vie with one another in striving
to win her favour, and, whether by sheer push and
vigour, or by some esthetic consideration, or perhaps
by some choice of which we have no conception, one of
the competitors is ultimately successful.

It may be urged that such methods are the excep-
tion, and that in the majority of cases there is no
evidence of such tourneys or of such toilsome routes
being performed before the favour of the mate is
won. It might be thought that a large number of
animals, such as snails and crabs, are incapable of
such ardour, and that in any case such a meticulous
care for the colour, agility, or strength of the mate
would be misdirected energy, since in point of fact any
weaklings would be destroyed by natural causes before
the mating season. Recent observations have tended,
however, to emphasise the severity of the test that
most, if not all, male animals undergo; and even if
we admit that there are many cases: where tourneys
are not fought before assent is won, yet that it is not
by ‘ natural causes’ that weaklings are weeded out is

a a a

SELECTION OF MATES 199

evident. There are many groups of animals in which
males are scarcer than females. In such cases direct
personal competition would be unlikely, and in fact
does not, so far as we know, regularly occur. But,
nevertheless, a severe though unseen test is applied.
Each family at first contains on the average an equal
number of the two sexes, and therefore for every
male that grows to maturity at least two must perish ;
that is, the action of natural causes is not the same
for both sexes, but falls with unequal emphasis upon
the young males. For such diverse creatures as cats,
plaice, and hermit-crabs this conclusion has been found
to hold good.

The life of animals and of working men agree in
this, that, consciously or unconsciously, it is a strife
to give their children the best chance. Their response
to this spirit takes varied forms, but ultimately it is
an answer to the samestimulus, and though it seems to
arise within us, it is the spirit of a hive whose boundaries
are not limited by the seen or tangible. But the case
of animals is heightened by the strenuous selection of
mates by whom the welfare of the race can be best
advanced. And in this, animals and the lower races
of mankind exhibit meticulous care for physical
prowess, for on that alone is advance possible.

If we think such considerations below us, the
whirligig of time brings in its revenges with cries of
deterioration ; and we revert to the study of animal
life with wonder at the severity of the test and the
richness of the reward that such competition exhibits,

200 ANIMAL LIFE

as we review each group in its response to the welfare |
of the race. | |
The most majestic of these responses is that of

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FIG. 35.—Transformation of a groundling Sea-worm (Verezs), A, into a
migrant of pelagic waters. B, The eyes are enlarged, the paddles more
complex and effective.—(A/fter Quatrefages. )

migration. Under the stress of a-cause not their

own, birds and fish assume a new aspect and travel

with their mates to far-off, traditional nesting-places.

On this journey they behave as creatures possessed.

THE WELFARE OF THE RACE 201

They endure the extremes of climate on their passage
from the rivers to the sea, from the sea to the water-
heads. An old memory of the road seems to revive
within them, and in following it out they are hardly to
be delayed or turned aside. Even the sea-worm leaves
its burrow, and, transformed within and without, it
then launches itself upon a journey from which it will
not return (fig. 35.)

The strange Palolo (fig. 36) of the South Seas, that
fills the reefs with its slimy burrows, assumes a new
guise at the October and November full moons. Its
tail acquires eyes, becomes blue and full of eggs.
At the appointed night-time myriads of these fruitful
tails separate from their heads, leave the reef, and
swim out tosea, where, after discharging their burden,
they die or are caught by the natives assembled for the
Palolo rising.

The most general method that animals follow in
providing for their young is to cast their eggs upon the
waters. Heartless and improvident as the act may
appear, it is a wiser instinct than we deem.

They seem to realise that the sea is their mother,
and that what they cast upon her care shall return as
offspring in no long time. Their trust is justified.
Movement, oxygen, and ultimately a feeding-ground,
are the requirements of the young. They need rocking
in order to stimulate their weakly glands, muscles,
and nervous control; they need. oxygen to maintain
their vitality and promote development ; and when
they are hatched their demand for food is incessant.

202 ANIMAL LIFE

These and other needed gifts the waters possess.
The open sea rocks them day and night; its even
temperature shields them; its foam invigorates and _
aérates them. Nor has their mother left them without

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Fic. 36.—The Palolo-worm (Zumice viridis) from Samoa. This sea-worm
consists of two obvious regions, a head-end bearing tentacles, and a far
longer tail-end bearing eye-spots. These two portions part company
on the nights of a certain tide in October and November, the tail-end
going out to sea, the head-end remaining on the reef and in time
regenerating a new tail.—(After Woodworth.)

some safeguards. She liberates them in myriads
of glassy, invisible droplets from a spot whence the
current sets for the shore ; she provides them with a
float to keep them near the surface; so that when

THE WELFARE OF THE RACE 203

the young hatch they find themselves drifting into a
populous shore-water from which they may gather food
without stint; and if on the journey haddock and
wolf-fish have fallen upon them, their vast array will
endure many such attacks without serious loss. These
losses are, indeed, foreseen. At the outset a single

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Fic. 37.—Eggs of the Herring fixed to seaweed.
(From a specimen in the Manchester Museum.)

family would number perhaps half a million, and if
all were to survive the sea would in a few years be a
quivering host of one prolific fish. But the chances of
the road remove battalions silently, and still leave
enough for there to be not only as good, but, fishing
apart, as many fish in the sea as ever our histories

204 ANIMAL LIFE

record. A second method in which the mother lays her
young is that of fixing the eggs to weeds, stones, or
the like. The herring dusts them over every object on
spawning-ground ; the goby glues them to the inside
of an old shell; the snail lays her jellied eggs in
plates, bands, and coils on any support, and the cuttle-

Fic. 38.—Eggs of the Cuttlefish (Sefza).
(From a specimen in the Manchester Museum.)

fish fastens her grape-like clusters to the seaweed
(figs. 37, 38).

Some gnats form egg-rafts that float on water,
others twist ropes that moor the eggs to some fasten-
ing. The dogfish hangs its barrow by tendrils to an
anchorage ; the skate drives her egg-case into moist
sand. The perch spins a beadwork of her eggs and
spreads it in the reed bed. The frog heaps her

THE WELFARE OF THE RACE 205

glutinous spawn in the ditch water. With the coming
of spring, sea and river appear to break into life. Sea-
shore and lake-bank are fringed by these jelly-like
nurseries, which seem to spring from the ground or
to solidify from the foam. Rarely does any watcher
guard this seed. The tide breaks over it, stirs and
quickens the latent life. The fitful spring passes over
the marshes, now retarding, now hastening, the pro-
gress of their future race.

Here and there the mother or her mate jealously
guard their treasure from the sight and attacks of
intruders. The male goby overturns the sea-shell
that his mate has covered with her clutch of eggs
and tilts it slightly by burying one end in the sand.
Stationing himself at the opening he mounts guard,
keeping a look-out, and ceaselessly stirring the water
with his tail so as to renew the stream of oxygen
which the eggs require. At this season his coat is
at its brightest, and responds to the colour of his
mood. If excited, the blue spots become more intense
and the red shades more vivid. At the approach of an
intruder he at once darts out, full of fight. So, too,
other fish defend their offspring with a spirit and dash
that are unlooked for until we learn what devasta-
tion of this spring-laying is wrought by storms, rats,
fish, and birds.

Against these destroyers of their broods animals
strive to set up defences. Instead of merely fastening
their eggs by a slippery jelly, they embed them in a
hollow, or even carry them on their own persons. The

206 ANIMAL LIFE

lamprey lifts stones with his sucker till a hole has been
made in the river-bed, and then the eggs are laid in a
sort of nest. The stickleback weaves a neater nest,
made of fibres cemented with glue, over which
the male hovers. The female pipe-fish makes a nurse
of the male. He carries the eggs in a special pocket
until they are hatched, and for some days afterwards
performs the part of an animated perambulator.

In their efforts to guard their young, animals
adopt strange devices. Some frogs wind a string of
eggs round their bodies and hind feet ; others embed
them in a pouch carried between the shoulders ; the
male of one frog swallows the eggs, and stores them
in his cheek pouches, or croaking sacks, until Bn,
swim out as tiny tadpoles.

The reptiles bury their eggs deep, and leave them
to be hatched by the heat of decomposing vegetation
or by the heat of the sun.

Many tropical birds make mounds of rotting
leaves over their buried eggs, as though to remind
us of their reptilian ancestry. But in the majority
of cases birds and insects, true to their high traditions,
show the most varied and complicated devices for the
safety and benefit of their offspring.

Perhaps the best test of this statement is the record
of nests of known birds and insects found by any one
observer. Although all the nests of British birds ~
are known, few naturalists, after a lifetime of search,
are personally familiar with more than two-thirds of
those that occur in this country ; and, to take but one

PROTECTION OF THE YOUNG 207

instance showing how easily nests are overlooked,
one may quote that of the plover. These birds are
systematically robbed of their eggs on many a country-
side, and yet the number of. green plovers has only
lately sensibly diminished. But in countries where the

Fic. 39.—Sand-Martin and Young.
(From specimens tn the Manchester Museum.)

enemies of birds are more numerous and cunning than
in Great Britain, the nesting habits of but a small
percentage are known. In tropical America, where
the humming-birds are as common as bees on a
patch of clover, a naturalist may spend years without

208 ANIMAL LIFE :

discovering more than one or two kinds of humming-
birds’ eggs.

If this is true of birds, much more does it hold
for insects. The most experienced entomologist,
after years of search in a district, will look with some
regret on the flies that alight on him, or hover near
him, for he knows that he is totally ignorant of the life

Fic. 40.—Nest of Swallow.
(From a specimen in the Manchester Museum.)

history of nine out of every ten kinds of the humming
life of summer. We must admit, then, that insects
and birds place their nests in positions which are
usually hard for us to discover. The real extent of
their care, however, is only disclosed by intimate
study. A few cases only can be briefly considered.
The nests of birds are of the most varied construc-

= ft vr

a

FIG. 41.—Nest of the Little Tern on the shingle just above high-water mark.
(From specimens in the Manchester Museum.)

P

210 ANIMAL LIFE

tion—from the merest depression in the shingle to the
elaborate felt-work of the chaffinch or the pendent
house of the ortolan.

Sea-birds make no proper nest. They assemble in
vast numbers at a few isolated rocks, grassy cliff
slopes, or solitary sand-flats. These they revisit in
spring with great punctuality; coming often from
great distances, and disappearing when their young
have grown capable.

The terns and oyster-catchers lay their eggs
only just above high-water mark in little depressions
of the shingle or sand. The resemblance of the eggs
to pebbles is astonishingly close, both as to shape and
colouring (fig. 41).

Gulls assemble on grassy slopes or marshes and lay
their eggs in depressions lined with weeds, grass,
or leaves. Guillemots lay right on the rock ledges.
Puffins utilise rabbit-burrows, and petrels the crannies
of rocks.

Wading-birds that spend part of the year at the
shore, but nest inland, show little more skill than
their purely long-shore relatives in the construction
of nurseries. The curlew lays in depressions of the
moorland, the sandpipers on the shingle of rivers.
Herons make rough nests in trees. Swans collect
vast piles of débris without much artifice ; ducks and
geese are exceptional in lining their nurseries with down.

Powerful and gregarious birds as a rule build
clumsy nests. Immunity from enemies seems to
render fine weaving unnecessary. MRaptorial birds

——— veo

—— ="

ae

Fic. 42.—Nest of Skylark.
(From a specimen in the Manchester Museum.)

212 ANIMAL LIFE

make their eyries on cliffs, crags, or trees, constructing
them chiefly of branches and sticks. Pigeons make
but a slight foundation of twigs. Rooks adopt a rough
lining of roots, and jackdaws improve on this by lining
their large nest, hidden in some hole, with fur.

With small birds, whether solitary or colonial, the
case is different. Their choice of site is wide, and
the degree of secrecy and skill employed in the making
is most varied. The nest is usually of the open-topped
type, and generally consists of an outer layer of
coarse material lined with moss, feathers, or some
fine and non-conducting material. Both sexes assist
in its construction, and employ their bills and feet in
doing so with a skill and assiduity that reach their
maximum in the exquisitely finished handiwork of the
titmouse (fig. 43) and the chaffinch.

The need for this greater skill in constructing and
concealing the nests of small birds seems to lie not
only in the defencelessness of the artificers, but in
a consideration that affects their young. Nests are
formed, not merely to surround and screen the nestlings,
but to enable the incubating heat of the sitting bird to
be concentrated on the eggs. Now the size of an animal
is directly related to its power of retaining heat ; for
with two creatures, one double the weight of the other
but of equal proportionate powers of heat production,
the heat produced will be as eight to one, whereas the
loss of heat in proportion to weight, that is, roughly, in
proportion to production, will be determined by the
amount of body surface from which heat is lost, that

Fic. 43.—Nest of Long-tailed Tit-mouse.
(From specimens in the Manchester Museum.)

214 ANIMAL LIFE

is, as four to one. In other words, a small bird tends
to lose its heat at a higher rate than a large one, and
in order to maintain the same degree of heat, either

F1G. 44.— Young Cuckoo in Nest of Titlark.
(From specimens in the Manchester Museum.)

INCUBATING HEAT 215

.its productiveness has to be increased or loss of heat
checked. The great voracity of small birds con-
tributes to maintain
the production of heat,
and in order to con-
centrate this upon the
eggs a non-conducting
lining and hollow shape
is given to the nest.
By this means the de-
velopment of the egg
is ensured, and the
nestlings are protected
until they have de-
veloped a heat mechan-
ism sufficiently strong
and pliable to enable
them to lead a free life,
at least during the
warmth of the day.
A similar _ principle
underlies the nests of
mammals, of which
that of the harvest
mouse is perhaps the t
best example (fig. 45). TA a

That vast collection Fre. 45.—Harvest Mouse and Nest.
of artificers which we (From a specimen in the Man-
name insect, exhibits chest ae)
in the care of its young, as in every other pursuit,

216 ANIMAL LIFE

the most varied methods; but in their response
to the stimulus of race-maintenance, more than in
any other performances, insects of the higher classes
exhibit a dominant interest. They have brought their
several works to high degree of finish, and exercise in
doing it such unwearied devotion and skilled instinct
as to furnish us with a theme that exhausts our
astonishment as it stimulates our wonder. In the
choice of nesting site, and the construction of the
building, in the storage of suitable food and its re-
plenishment, in the division of labour and response to
a communal spirit, the social insects have undoubtedly
worked out a full and successful scheme of life. There
is perhaps no other society where individual interests
are so subordinated—now in one direction, now in
another—at the command of a genius that seems to
dominate the whole and to declare how the welfare
of the race is to be served.

REFERENCES

Selection of Mates: Darwin, ‘ Descent of Man.’ Poulton,
E. B., ‘ Colours of Animals’ (Internat. Sci. Series, vol. Ixviii.).

Peckham, G. W. and E. G., ‘ Occasional Papers’ (Natural
History Society, Wisconsin). Vol.i. 1889. (Spiders.)

——

~ Ade

217

CHAPTER X

THE LIFE-HISTORIES OF INSECTS

OF all the impressive actions that insect life presents,
those connected with the welfare of their young and
with their life-history are the most important, and
in fact it is largely by their other-worldliness that the
group has risen from its obscure beginnings and poor
relations—the spring-tails, silver-fish, and centipedes—
to range after range of dominance in the kingdoms of
the air. Beyond the usual demands for racial welfare,
such as we meet with in many other highly organised
and aerial creatures—spiders and birds, for example,
there has evidently been, in the case of insects, some
factor at work which has led to this elaboration of
nurseries, this preparation of special foods, this
sunlit, devotion to the needs of a progeny that its
mother may never see.

Such a factor we may see in the influence of climate.
Insects are border folk. They are the offspring of
earth and air. Great as are their powers of adaptation,
they have failed to adjust and maintain the tempera-
ture of the body without direct reference to that of
their surroundings. Hence their vitality rises and
falls with the thermometer, and the more exaltedly

218 ANIMAL LIFE

they rise in the scale of insect-life the more, rather
than less, sensitive do they become. A frost that
kills bees like flies passes lightly over the spring-
tail, safe in the close embrace of his warm, ancient
earth. Against the onset and rigour of the cold
insects have no protection, save to bury themselves
in the ground. From the parching influence of con-
tinued dry heat they have also few means of escape,
so that in tropical and temperate climates there is a
period when insect life is partially exterminated.
But with the next rains or the coming of spring the
hospitable period ensues when sap, pollen, honey,
and juicy leaves provide a feast. Hence for insects
to pass, even in a winter sleep, through the lean period
so as to reach the fat season, is a consideration of
supreme importance ; and to utilise the new growth
for the development of as many fresh broods as the
summer permits, is of hardly less pressing import-
ance. It is this oscillation from plenty to poverty
which drives insects to such multitudinous devices,
and maintains in their advanced sections of society
such a high degree and standard of activity devoted
to racial ends.

We may commence the cycle at the season of spring.
’ From crannies and underground hiding-places there
emerges a remnant of the summer’s host; a few
butterflies have survived the winter in barns and
lofts; caterpillars have hibernated in moss, that
resort of the frost-hunted; many beetles and ants
have slept in the ground, a queen bee and queen

a |

SEASONAL ABUNDANCE OF INSECTS aig

wasp have here and there lain moribund under clods
of earth. From caves and hollow trees the few
surviving flies of the huge summer legion creep into
the outer air. Ensconced between bark and trunk,
among bud scales and in the ground itself, are the
imperishable eggs of green-fly and scale-insect, which
no frost can kill and no mould injure. These hatch
at the coming of spring and provide a new generation
of aphides and coccide which fatten on the opening
buds, and from imperceptible beginnings increase
their coming with an acceleration that is ultimately to
raise the rate of increase to one that the vibration of
light alone can parallel. In the water there are few
signs of summer’s abundance. As on land, a last
stand has been made by a few water-beetles, with
perhaps may-fly, dragon-fly, or caddis-fly larve here
and there; but the seed that is to flower out into
wriggling plenty is at present an inert, encased egg
left by dragon-fly, alder-fly, or stone-fly in the un-
stirring mud or on the water weeds.

With the onset of warmth these scattered centres
of suspended animation resume or commence their
activity. The hive-bees that have clung together
for warmth make their cleansing flight ; the solitary
burrowers drill, with teeth and claws, holes in the sandy
bank ; wasps select their sites and begin to work up
wood-chippings for the nest; ants creep from the
~ deeper earth to the surface and under cover reconstruct
their city ; beetles scavenge the roads and meadows,
rifle the early blossoms and leaf buds, or scour the

220 ANIMAL LIFE

pond-weeds ; flies gain strength to travel where the
rising sap and filling nectaries, the warm blood of some
livestock or some less attractive nutriment, may give
them site and substance for their own needs and those
of their offspring.

Week by week the life of the pond increases as the
dormant eggs therein hatch into the larve of hover-
ing flies, and as the few hibernating aquatic larve
become transformed into the first dragon-flies of the
year. Then, as the fluttering, humming, and creeping
life is resumed, its first impulse is to provide, not for
itself, but for that which is to come, to find a place
where the young may be laid so as to reap the first-
fruits of the spring ; for now there is a new market
and but few competitors, and presently the blooms
will be gone, the enemies many, and the strife fierce.

Thus the first spring brood makes its several
election of nesting-places. By some sense of smell,
and yet unexplained instinct, the butterflies and
moths, winter-worn or spring-fresh from their pupal
cases, deposit their eggs in little batches on or near
the food plant that the caterpillar needs. Each egg
is a minute, impermeable, sculptured vase, completely
enclosed in which is the germ of the future caterpillar.
In a week it will emerge gifted with as great a preference
for one plant rather than another, as though it had
a large experience and a matured decisiveness. Such
narrow taste in a new-born creature is, however, the
rule. As miuk is the best and most acceptable first
food for our race, so, from the simplest worm up-

THE FOOD OF YOUNG INSECTS 221

wards, there is one diet on which the development
of each creature is dependent, and the higher in the
scale we ascend the: more specialised as a rule does
that nutriment become. When we add to this exigent
taste the delicacy of new-born animals, and the
penetration of enemies, we see that the choice of
nursery is ruled by conditions that confine success in
promoting the existence and welfare of each race to
a comparatively narrow line of conduct.

This stringency is, however, a penalty paid for a
high and modern place in the insect world. -The
lower insects, and those of very ancient origin, have
more latitude. Nearer than recent conquerors to
their ancient home, the soil, the straight-winged
insects, field cockroaches, grasshoppers, and crickets
lay their eggs in the ground.

When the young emerge, not as grub-like cater-
pillars, which is rather a sign of a recent than of an
old family, but ‘as little six-legged miniatures of their
parents, these young aristocrats exercise their taste
for almost any destructive work, under cover of dark-
ness—wood-carving, root-cropping, or mould-eating.
Thus, between the old and the new insects, there is a
difference from the commencement of life. The old
families have to work for their living on coarse fare,
the new are provided for and live delicately.

It is, however, only by the advantages which such
forcing gives that the newer families of insects have
gained the command of new stations. If they have
not the strength, adaptability, and ordered tradition

222 ANIMAL LIFE

of the locust, the dragon-fly, the clothes-moth, and
certain beetles which represent the jim fleur of insect
peerage, then new-comers must command success by
other means, and these they employ from the first
moment of their children’s lives. By giving their
young a start in instinct, in position, in surroundings,
they do much. But initial advantages such as these
are not enough to maintain the struggle, limited as
it is to a few months each year. The spurt must
be followed up by rapid growth to maturity, and by
a succession of broods with powers of securing new
stations, and so immolating themselves in the aggrand-
isement of the race.

It is with this hurly-burly in mind that we appreciate
the contrast of the fly, which grows up in ten days,
with the locust, which leisurely pursues its childhood
for a year or more. It is this competition for the
success of the family within the limits and by the gifts
of summer, that has raised bread-winning to such a
high art, so diversely followed, according to the age
traditions and genius of the different orders of insects.

The earliest traditions of insect history, unlike
those of most groups of the lower animals, point to a
terrestrial, air-breathing, mould-nourished way of life.
Between the infantile and adult habits there was
no great difference. Lovers of dimness, their favourite
resting-place was in the rich earth, where young and
old found nourishment in abundance, shelter, and
means of escape from animate and inanimate ravages.
Their movements consisted in only short runs or sudden

ns

Fic. 46.—Some Primitive Insects.

A, ‘Silver-Fish,’Zepzsma, found in kitchens.—(A/ter Buffon.) B, Campodea,
a small white antique insect found under stones. C, Smdinthurus, a
member of the order Co//emdbola, provided with a spring (a) and a
curious ventral gland (4). Itoccurs on grass, the surface of water, and
sometimes on tomato-houses.

224 ANIMAL LIFE

leaps, executed by the six legs or spring-joint of the
tail (fig. 46, c, a), for flight is not yet known, and
their shoulders are destitute of wings. Such creatures
are everywhere abundant, but, like all old families,
their influence is less seen than felt. They live in
retirement—every stone and log conceals them ; leaf-
strewn hollows, banks of moss, kitchen hearths, and
gardens are equally their resort. From Europe to
Tasmania, on lowlands and highlands, on snow slopes
and in glacier water, there is hardly a station where
they may not be found. Their colours are for the
most part sombre ; dark blue and brown chiefly prevail.
The silver-fish of our hearth-stones is of exceptional
brilliance, and contrasts with its dun-coloured relative
of the coast and uplands. Their eggs are laid in the
earth, and out of them issue miniatures of the parent,
which grow to greater likeness by insensible grada-
tions and increments of strength.

The straight-winged insects are of immense an-
tiquity. They have retained their dominant position
by their hold on the earth and grasp of the air. In
every respect the tribe of grasshoppers, locusts, and
cockroaches shows an immense advance on their
predecessors in their two pairs of wings and powers
of flight, in the strength of their legs and jaws. They
have come out into the air and sunshine, and scrape
their fiddles and leap and fly in the exuberance of their
energy. Nor is their colour unsuited to the mood.
Grasshoppers catch from the grass something of its
green; from the leaves some touch of their red;

LIFE-HISTORY OF GRASSHOPPER = 225

whilst the burgling, nocturnal crickets and cock-
roaches are appropriately dusky.

The provisions of these Orthoptera for the welfare
of their children are of the simplest. Their eggs are
laid in the soil or in dark corners, and are provided
with yolk and a tough covering. In from fifty to a
hundred days the young emerge. By the aid of a
special swelling in their neck they break the wall of their

Fic. 47.—The development of a Grasshopper, showing the gradual
evolution of the wings.—( From Packard’s ‘ Text-Book of Entomology.’
By permission of the Macmillan Co., New York.)

prison, and once set free in the soil they commence to
nibble the roots and moulds that surround them. In
appearance, as we have said, they are miniatures of
their parents, except in colour and _ winglessness.
Developed in the dark, these little grasshoppers or
crickets emerge as pale, minute creatures, which for two
or more months will slowly grow, bud out wings from
their shoulders, and fly at intervals in the warmth

Q

226 ANIMAL LIFE

and sunshine, to harden and exercise their limbs. At
regular periods their inflexible skin has to be removed
to allow of growth, and a covering one size larger
replaces the old coat. As the rate of growth in insects,
as in all animals, is fastest at the beginning of life and
slows down later on, the skin has to be frequently
changed at first, and at longer periods subsequently.
We rarely appreciate with what difficulty and danger
the process is accompanied. The outer skin is a con-
tinuous envelope, softened only at the joints of the
body and limbs. Not only are all the visible parts
encased by this covering, but the lining of the mouth
and many internal parts are formed by infoldings of
this skin. Hence an insect has to sever this intimate
union as well as to slip out of its external casing. It
must strip its inside and its outside of their protecting
envelopes, and the wrench tests all its strength.

The first act is a rent in the outer garment between
the thorax and head, made by forcibly filling the
vesicle in the neck until it breaks. Humped up
thus, the struggle goes on till the head and neck, with
all their appendages, are free. To pull off a jersey is
simple compared with the act of pulling away the
eyes, the antennz, the jaws, the legs, the mouth, and
stomach from their encasing skin. Any holdfast to
which the old skin can be hooked and then pulled off
is made use of, and at this time the use of many
projections on the body is first discovered. The legs
gratefully cling to the tail if thereby they may pull
themselves out of their casing; and so with much

— = ~~

LIFE-HISTORY OF GRASSHOPPER 227

effort the forepart of the body is drawn out of its old
envelope. Then follows the disclosure of the abdomen,
and the old skin is wholly discarded. The young
grasshopper is now soft and helpless. Its new skin,
more brilliant than the old one, is wet ; its muscles
fatigued. Fora while, therefore, it lies waiting for its
heart-beat to become steady, its skin to harden, and
its muscles to resume their tone.

A comparison of the old skin with the new one
reveals certain differences between the two. Not only
are the colours brighter than before, but rudiments
of wings are now disclosed. At each successive moult
of the grasshopper both the size of the animal and
of the wings increase, until, at the final change, the
spread of wing can sustain the body for short flights.
The development is therefore a gradual one. Each
stage has been gradually accumulating under the
covering of the previous one. As there is no violent
break in structural development, so there is no change
of habits till the first flight is made. Old and young
live under similar conditions, and probably upon the
same vegetarian diet. The wings are chiefly used to
carry the grasshoppers into new districts where they
may found fresh colonies.

The life-history of the grasshopper is one typical of
the vast and ancient order to which it belongs. This
order—the Orthoptera—is to other insects what the
rodents are to other mammals. They share our dark
corners and produce with mice and rats; they gnaw

the herbage with the field mice and voles. They
Q2

228 ANIMAL LIFE

burrow in the ground like rabbits to bring forth their
young, and share the desert and veldt with the jerboa
and the Cape hare. Their development is a gradual
one, with no long period of exposed unprotected state
of helplessness. They begin life as relatively large
heavily yolked eggs hidden in the ground. They
hatch as strong insects capable of biting and assimi-
lating the leafy food that surrounds them. They
grow from strength to strength without the internal
strain of adolescent change or the outer stress of meta-
morphosis. They emerge upon the sunlit or moonlit
meadow which has fattened them, and either in its
soil or in the ground of some distant country they
provide for the welfare of the race.

The Dragon-fly.—If the ancient orthopterous in- —

sects form the type of dominant herbivorous ground-
lings that grow by increments and only momentarily
fly from blade to blade, the dragon-fly is equally the
example of the ancient carnivore that grows in the
water and then lives on the wing. Flight, which toa
grasshopper is a temporary exertion or a colonising
movement, is the natural habit of the dragon-fly and
is carried to a degree of perfection that is reached
by few other animals. So aerial has the dragon-fly
become that it can no longer walk, and only uses its
legs for holding prey or for perching. This hawk-like
flight involves the renewal of a light food at frequent
intervals, and the structure of the dragon-fly is a
superb example of the means of obtaining the juices
of insects. Its whole aspect is that of a dominant

7 le ie

t at

Fic. 48.—The life-history of a Dragon-fly (Leucorhinia glacialis). The
aquatic larva is resting on a submerged stem. The last larval stage is
creeping up out of the water.—(A/fter Needham. From New York
State Museum Bulletin, 1901.)

230 ANIMAL LIFE

race. Its large size and powerful wings give it the
command of a wide range of country, and the capacity to
migrate across narrow seas. Its colouring is vivid and
metallic. The mobility of its head and the huge eyes
that almost enclose the head enable the dragon-fly to
take note of objects on all sides, and to seize its prey
from any position. The six legs enclose the prey.
The jaws rapidly dismember a stricken fly, the juices
of which are sucked through the minute mouth. The
dragon-fly is one of the few old groups of animals that
are conspicuous. Its ancestry reaches back to remote
ages, and there is reason to believe that the swamps
of the coal-measures were haunted by raptorial dragon-
flies similar to those that to-day quarter the river-
courses in most parts of the world. This long descent
is evinced by its vitality, for the head severed from the
tail will continue to eat as heartily as before.

The prelude to this sunlit active life is passed
quietly and inconspicuously under water. The oval
eggs are dropped casually into a pond or marsh, or
even a water-holding leaf, and give rise in the course of
weeks to a grotesque creature about a tenth of an inch
long. . It is just visible to the eye as a brown wingless
animal. The head is flat and furnished with minute
eyes. The six legs are used for slowly exploring the
muddy bottom, and the tail has the curious faculty of
inhaling and expelling draughts of water for the double
purpose of supplying oxygen to the tissues and of
making sudden springing jumps.

Almost the first act of this ‘nymph’ is to cast its

LIFE-HISTORY OF DRAGON-FLY — 231

first larval skin, and when that difficulty is overcome
the special instincts of its kind manifest themselves.
From first to last all are carnivorous, but adopt various
ways of overcoming their prey. The nymphs of some
dragon-flies conceal their body in the mud, under the
surface of which they make their way by slow puffs
of the tail, and then dart out upon some passing
beetle, larva, or worm. Others lie motionless among
the weeds, with the colouring of which their own
agrees, and spring out from cover upon their prey.
A few bolder forms make no concealment, but pace
up and down seeking for provender.

These nymphs are provided with a singular weapon
for catching prey. This is the ‘mask’ or under-lip,
which is greatly elongated and doubled back by a
hinge-joint until it almost touches the forelegs. To
its free end is hinged a pair of curved opposable teeth,
and when the desired prey is yet an arm’s length off,
this long arm is smartly extended with a sudden jerk,
the prey is seized by the teeth, and whipped back
into the safe grip of the other jaws.

After the third or fourth moult, buds of the two pairs
of wings appear on the thorax, and grow steadily larger
at each stage, the eyes increase in size, and the nymph
prepares for its final change. It climbs upa support,
fills its tracheze with atmospheric air, and shovels off its
investment. The brilliant fly emerges, and in amoment
develops all the power of flight it will ever display.

May-flies—Among the mazy dancing insects that
haunt rivers, some relatives of the dragon-fly are well

232 ANIMAL LIFE

known to the angler. The ephemeral may-flies hover
thick as snowflakes for the short afternoon that rounds
their winged life. The stone-fly flutters to a warm
resting-place, whisking its long tails. The alder-fly
rouses the fish to feast on the windfalls that every
puff provides. These gauzy hoverers are rising from
the water. The fringing weeds are hung with their dis-
carded suits. The river-bed has been crowded for the
past year with their creeping nymphs. (Frontispiece.)

The life-history of may-flies or ephemeridz lasts
from one to three years. The oval eggs are laid on the
surface of the water by the swarms of flies that hover
over ariver fora day ortwo. They sink to the bottom
and become attached by anchoring threads to some
holdfast. After an interval these eggs give rise to
shrimp-like larve, with two or three tail-filaments,
and just as there are many kinds of ephemere, so the
larve are of different form and varying habits. All,
however, undergo many moults, acquire several pairs
of leaf-like gills, and pass by gentle gradations into the
winged state. Their adaptations to different modes
of life are of much interest. Some are burrowers, and
feed upon finely divided organic matter. These pos-
sess a long body, a small head, and dig with their
forelegs. The six pairs of feathery gills are kept
incessantly moving, and each contains a branched
air-tube as well as filamentous blood-vessels. The air
in these breathing-tubes is, however, not drawn into
them from the atmosphere, since there are no inhalant
openings from the surface, and it must therefore

——— ss) «

LIFE-HISTORY OF MAY-FLIES 233

accumulate by diffusion. Such larve are very common
in ponds and slowly moving streams. A second kind
of larva is one adapted to live in the rapid streams of
upland districts. The body and its appendages are
broad and flattened, enabling these species to with-
stand or evade the current by clinging to stones
whilst utilising it for respiration. These larve are
carnivorous and. make no burrows. A third larval
form is the swimming one, such as that of the common
Chloeon, found in pools and small streams. The tail-
filaments are fringed with hairs, and form an effective
tail-fin. The gill-plates have no filaments. Lastly,
there are creeping forms of may-fly larve which live
in running water on muddy ground and cover their
gills by large leaflets. Their body is encased in a
layer of mud imbedded in the hairy skin, and under
cover of this disguise these larve strike down their
prey.

When the larve are full grown they quit their
burrows or the river-bed, and make their way to the
surface of the water. Here a rapid metamorphosis
occurs, and from each larva a winged fly suddenly
darts away. The gills are shed, the jaws, feet, and
tail-filaments are modified, and the eye exchanged for
a many-faceted compound eye, and the single or double
pair of wings is suddenly expanded. The may-fly,
however, settles immediately after emergence, and
again, in a twinkling, casts a second transparent skin
which covers the whole body. This epiphany comes
upon thousands of ephemere simultaneously, and in

234 ANIMAL LIFE

many districts the whole local population of one or
two year old may-fly larve undergoes its transforma-
tion in two or three successive afternoons,

The More Complex Life-histories—Metamorphosis

A distinctive feature of the life-histories we have
described is the gradual evolution of the fly. The
assumption of the last phase coincides with the
completed formation of wings and the display of
flight. Only in its last phase is the organism some-
times transformed in outward appearance for aerial
life. This gradational life-history is one of great
antiquity, and the insects that exhibit it.come of an
old stock. Young and old are in close touch with the
primitive life of earth and water, feeding on moulds
and herbage, devouring the flesh of simple organisms
or the mingled decay of organic life. The most
primitive of all modern insects remain groundlings ;
but the necessity for disseminating their eggs and
colonising new districts has acted as a spur which has
driven the adult insect of other orders to become
a fly. In its simpler forms this power does not involve
any great change of habit, but for its perfection flight
requires the nicest adaptation. The changes needful
to this end are therefore worked out towards the close
of the earlier and more sedentary phase of life, and
involve a less or more complete transformation of the
organism—less as the time is long and the preparation
gradual, more complete as the life is shortened and the

METAMORPHOSIS—CADDIS-FLIES — 235

broods are hurried on to enjoy the summer, to spread
and increase its abounding life. In this way the life-
history of the modern insects become divided into
periods characterised by adaptive structural features.
The earlier period is one of growth, the last is one of
active colonisation, and as these functions become
mutually incompatible, a gradual change from the
earlier nymph to the later fly has been abandoned.
An intermediate period is introduced during which
the transition is effected. Aided by this, the earlier
or nymph stage can now more freely adapt itself to
circumstances that favour growth, the fly can acquire
new combinations of structure and instinct that will
aid the spread and welfare of its race, whilst the
transition state itself becomes adapted to that pro-
tection which it increasingly needs as it becomes the
seat of that complex remculding of the old traditional
life to meet fully the new activity. To the insect
in this transitional period the term fufa is applied.
Caddis-flies —The caddis (or hairy-winged) flies
offer a convenient example of this more complex life-
history. These insects abound near rivers and ponds,
and are not widely different from certain small moths,
though their four wings are provided with hairs
instead of with scales. The eggs are laid in or near
water, though occasionally far from any stream or
pond. The larve, well known as caddis-worms, have
‘something of that versatility which characterises
the whole class of insects.’ The great majority of

1 Miall, Natural History of Aquatic Insects, p. 255.

236 ANIMAL LIFE

species form movable cases of the most varied materials.
Others bind portions of the river-bed together into a
burrow or fixed case, which they quit at pleasure.
Some are adapted to still water, others to rapids.
A few inhabit brackish water or are marine, and at least
one is terrestrial and lives in moss at the base of trees.

The caddis-worm or larva may be easily exposed
by passing a pin through the harder end of its case,
and it is then seen to be a fleshy creature provided
with a head, a thorax bearing six legs and four tufts
of bristles, and an abdomen of nine segments, the first
and last of which carry peculiar processes, whilst the
intermediate segments bear filamentous gills. The
last pair of processes are hooked, and grip the sheath
or case so firmly as to remind one of the hermit crab
which clings to its shell by the hooked tip of its tail.
The first abdominal processes are three in number,
though not all alike, since the middle one can be
protruded or withdrawn whilst the others are fixed
by minute hooks into the sides of the case. The use
of these processes has been determined by extracting
larve and giving them a transparent substance (mica)
out of which to form a new case. When this is done
the abdomen is seen to be fixed in front and to un-
dulate gently for the greater part of its length. It is,
in fact, drawing in a current of water that flows over
its body and through the case, thus aerating the gills.

The manufacture of the case is a process full of
interest and of possibilities of experiment. In its
shape, materials, and construction the different species

LIFE-HISTORY OF CADDIS-FLIES = 237

of caddis-flies exhibit distinctive workmanship. Leaves
and sticks, stones and shells, or sand alone, are worked
up into cylindrical or curved tubes. The binding
material is silk spun from the silk-glands and worked
up by the lower lip of the animal. Some larve that
live in running water spin a roomy case of silk open
at each end and moored to surrounding objects by
threads. These threads form a snare in which other
larve become entangled. The caddis, aroused by the
increased agitation, emerges from its retreats and kills
its prey.

When the time of pupation arrives, the caddis
larva proceeds to add further protective measures.
It remains in the case, but closes up the two ends with
plates of silk; or it may block up the openings with
stones, or construct a shorter case of stones to replace
a leafy one, or other more complex contrivances.
Within this shelter the larval skin is shed by the
following day, and the pupa appears. In this stage
the wings, legs, antenne, eyes, and other organs of the
fly are visible, since they lie free and are not glued
down, as in the pupz of most moths. But the body
is not at rest. It still carries out the undulating
breathing movement that we have seen in the larva,
and it still possesses the gills. In addition to these
processes the pupa has a pair of strong-toothed hooks,
or mandibles, quite different from those of the larva.
With these hooks the pupa works its way out of the
stony case that has protected it and either floats,
swims, or crawls to the surface of the water, out of

238 ANIMAL LIFE

which it creeps over stones or plants. The pupal —

skin now splits, and the fly emerges.

Beetles.—The life-histories of beetles offer another
simple example of metamorphosis. They fall into the
three epochs of larval, pupal, and adult existence. It
is with some surprise that we find in this order the

gradational mode of evolution superseded by this —

abrupter succession of events; for beetles bear the
marks of antiquity. They are in close touch with
the soil, their food consists largely of moulds and of
the organic substances, animal and vegetal, on which
fungi are flourishing. The majority are cryptic or
crepuscular, and only the more modified forms feed
on sap, pollen, or nectar between their flights in the
sun, But though the life-history of beetles has a
pupal stage of preparation for the life of maturity, it
is marked by a leisureliness that recalls the long
immaturity of the grasshopper and the dragon-fly.
The cockchafer is three years old when it emerges in
summer, some ground-beetles have an equally long
larval life, and stag-beetles six years. Moreover, the
larve show few of those special adaptations that make
the caterpillars so attractive. They are usually six-
legged, spindle-shaped organisms, with powerful jaws,
but with no gracefulness of form or movement. Their
obscure life is reflected in their dull or fleshy tints.
They live for the most part on roots, fungi, wood, or
on other animals, and are among the scavengers of
the earth. The dor-beetles and the related scarabs
dig holes and provision the burrow for their young.

—

LIFE-HISTORIES OF BEETLES 239

The burying beetles are no disinterested workers,
but inter animals to serve as food for their larve.
Others again are root-croppers, such as the skip-jacks,
whose larve—the wireworms—devastate grassland ;
and again other families of beetles, such as the weevils,
destroy grain, root-crops, and vegetables. But even
this sombre order has its more adventurous careers.
The oil-beetles (Meloe), whose stout blue form may
often be seen sunning itself on grassy banks in early
spring, has passed through a life-history of unusually

el Fan Mai ae wT a aD
- ao Oe ,

on
at
é

?

+ ili _ 2 “ _—

Fic. 49.—Elaters or Skipjack Beetles (6 male, ¢ female) and their larva the
Wireworm (a).—(From specimens in the Manchester Museum.)

full incident, It proceeds from one of a large batch
of eggs laid in a flowery dry bank. Out of these eggs
there hatch a multitude of minute active yellow
six-legged larve. This immense family climb the
grass and flower stalks, covering them as with a yellow
down. Presently a bee—one of the many early spring
burrowers, Anthophora—will chance to settle near
them, and with a concerted spring a detachment of
the Meloe-larve will catch hold of its hairs and ride
on till the Anthophora visits its burrow. Once inside,

240 ANIMAL LIFE

they are carried down the dark shaft and into the
chambers where the bee’s eggs are laid and the pollen
stored. Here they alight, wait until an egg is laid,
and then fight for its possession. One obtains a hold,
a second attacks the.first and kills him, only to find
that a third is at work. Finally one alone survives,
and then the real tragedy begins. These Meloe
larve require the entire yolk of a bee egg in order to
reach the next phase of their life-history. No substi-
tute, nothing less than this, gives the needful stimulus
for further development. The survivor, successful up
to this point, now finds only a partial egg. This he

devours, but the amount of yolk is just too little. He

fails to achieve transformation, and joins that crowd
of failures to which he has despatched so many of his
fellows. Few indeed of the yellow ‘ triungulins’
that ride as so many Pucks on the bee’s back survive
the family quarrel. But to those that do, a strange
experience is allotted. They become transformed
into larve of another type, no longer active and restless,
but swollen and buoyant. Their diet changes, and
for forty days they swim in the stores of honey which
Anthophora laid up for her larve. Having devoured
this, the Meloe-grub pupates and in from one to
several months issues as a perfect beetle.
Butterflies.—The life-histories of moths and butter-
flies are to those of beetles as modern events to those
of ancient times. They are passed under conditions
more familiar to us than those of beetle life, often,
indeed, in the full light of the sun, and amidst the most

Se

LIFE-HISTORIES OF BUTTERFLIES 241

complex and recent of plants. The full-grown animals
are familiar to us,.their caterpillars and chrysalids are
common objects. Such intercourse argues a successful
and complex career. Butterflies are nicely adapted for
their sunny life. They are emancipated from touch
with the soil, the old coarse diet, and the primitive
conditions of life. Their structure is one of the most
complex organisation, and is sustained by a delicate
light nutritious drink. Their colours and form bear
witness to a complexity of life far removed from that
of the insects we have so far reviewed.

If the butterfly and hawk-moth are specialised
in structure and habits, their larval stage has in its
way adopted a far more complex life than is led by
the young of primitive insects. They feed no
longer on the fungi and mould-haunted provender,
the tough wood or fibre that nourished their cryptic
and simpler forerunners, but devour the juicy leaf of
the more recently evolved herbs and vegetables.
They have acquired decoration of form and colour,
activity of movement, measures of protection, and a
nicety of adjustment between their needs and the
good or evil chances of their surroundings that finds
expression in their choice of food plant, powers of.
hibernation, and capacity for social life.

The transition from this caterpillar life organised
for rapid growth to the state of flight has itself become
subjected to profounder changes than those that
affect the pupe of the caddis or the beetle. The
chrysalis is no longer always buried in the earth, but

R

242 ANIMAL LIFE

slung up by a silken hammock to a wall or a bent.
The play of light and shadow is reflected in its colours,
and the play of more profound and active agencies
than these is remoulding within it the body of the
caterpillar into that delicately poised organism the
butterfly. .

The life-history of the common cabbage-white
butterfly will give point and example to these state-
ments. The minute, vase-like, exquisitely sculptured
eggs are laid by the female on the cabbage leaves or
other cruciferous plants. In the course of a week
the young caterpillar emerges. Its worm-like body
is composed of a head, thorax, and abdomen. The
head carries powerful jaws inserted between the upper
and nether lips, rudiments of antennz, and a few simple
eyes. The thorax consists of three segments, each of
which carries a pair of stumpy legs? The abdomen,
divided into nine segments, possesses clasping feet on
the last four of them. The colour is a whitish tinge
speckled with grey, and from the third thoracic seg-
ment to the last abdominal one, paired black marks
indicate the breathing holes or spiracles. Movement
consists of a series of muscular waves passing from
behind forwards, aided by strides of the fore- and
hind-feet.

The first decisive act of the young larva is to cast
its skin. A crack appears along its back, and the
moult is done by peeling off the skin inside out. There
is now room for expansion, and this the caterpillar
seeks to fill first with its own husk and then with the

et

dl

a
3
q

E F ~ —¢

Fic. 50.—-Development and Parasites of the large Cabbage-white Butterfly :
A, a pill-box, the white specks within which are the eggs; B, the full-
grown larva; C, the male insect ; D, the female; E, the pupz show-
ing the wings and appendages; F and G, Ichneumon parasites of the
caterpillar. |— (From sfecimens in the Manchester Museum.)

244 ANIMAL LIFE

surface-layers of the leaf on which it rests. On the
chlorophyll, starch, and other elements of this diet,
it rapidly grows and adds reserves of fat to accumulate
beyond its present needs. Moult follows moult with
increasing size, and the spines that project from its
surface find their office is assisting the process by
preventing the old skin from slipping back as it is
peeled off the new one. At the sixth moult a change
of form occurs. Knobs and ridges that had been
moulded under the skin now appear glued down on
to the head and thorax. In these projections we can
recognise the eyes, antennz, proboscis, legs, and wings
of the butterfly. When these appear the caterpillar
is full fed. Bearing the marks of the perfect insect,
it now assumes the shelter of a wall-coping or other
crevice, to the sides of which it proceeds to attach
itself by means of a silken hammock. To spin this
support, the larva emits a drop of liquid silk from its
mouth, bends its head back under its body, and works
from side to side fastening the thread at two points
opposite the middle of the body which thus lies in the
loop. The next process is the shedding of the last
larval skin, which is rolled off and forms the un-
sightly débris that we often find near a chrysalis.
The pupal skin is now exposed, and the ridges that
outline the appendages of the butterfly are conspicuous.
They are, however, but the outlines for which the
necessary detail of muscle, nerve, and blood-vessel
is yet wanting. On the surface all appears quiet
and rigid ; a wag of the tail is the limit of response.

LIFE-HISTORY OF BUTTERFLIES = 245

Within all is stir and change. The larval body is
being dissolved and remoulded to fit the new existence.
The creeping muscles of the caterpillar are broken
down and rebuilt to form the flight muscles of the
butterfly. The jaws are abandoned, and the lips
transformed into an elaborate sucking-tube. The
digestive tube is altered to assimilate fluid instead of
solid food. The compound eyes undergo their intricate
development, and the nervous system which is to
control the new and complex organisation is itself
undergoing rapid concentration. In dimness and
stillness, without any perceptible controlling mecha-
nism, the tissues of the caterpillar are reformed and
the basis of the future responses is laid down. The
specific characters of structure and of colouring are
being added. When these changes are in process
the use of certain ridges and spines becomes clearer.
The delicacy of the internal organs is extreme, and
any pressure would deform them ; hence one reason for
the presence of projecting spines upon which the stress
may fall, and so be diverted from the inner yielding
skin.

When the metamorphosis is complete the pupal
skin cracks, and the butterfly, still with intricately
convolved appendages, steps out. Its surface is wet,
but as the air fills its breathing tubes, the limbs
and wings dry and strengthen. It clings tenaciously
to its surrounding holdfasts, whilst its muscles gain
tone, and the nervous system begins to control the
new mechanism. Finally the response to the new order,

246 ANIMAL LIFE

within and without itself, issues in a concerted move-
ment, and the butterfly flies away. —

The Diptera or Two-winged fues.—The most im-
portant groups of insects are those whose life-histories
are more rapidly traversed, or exhibit more profound
adaptations for the welfare of the species, than those
we have so far reviewed. These are the Diptera or
two-winged flies, and the Hymenoptera.

Flies are one of the scourges of the earth. They
have no fear. To them the persons and dwellings of
animals and men, and all that comes from them,
afford nourishment and shelter. They pierce and
suck with the finest and most elaborate of instruments.
They transmit typhoid, malaria, cattle-disease, and
sleeping sickness. They devastate prairies, and what
they do not kill they spoil. Wherever man goes they
dog his steps, and where he lives there the house-fly
follows. Beelzebub was the appropriate symbol for
such a scourge. Each winter of our climate promises
to end the plague, and clears the air and earth of flies.
But that avid life escapes all checks. In every mild
break small gnats emerge, and some fly shakes a loose
leg in mockery at the season’s persecution, and with
the approach of spring detachments of the vast bat-
talions issue from cover. Even in the cold of northern
Siberia, where spring and summer form but two
months of the year, the mosquito then hangs as a veil
over the rivers. In the fly’s sight earth and its waters
form a vast nursery ; its covering of verdure a sus-
taining drink ; its inhabitants a still more stimulating

a

(4azsayounpy SAprsaaawup ay “piimazy uop10y *9 fo uorssimasag Ag)

‘OUI[INO Ul WS SI sTVUL dy} JO pvoYy sy,

*(vougsauop vosnpy) Ay-asnoy] spewmsy oy .— "1S “1

248 ANIMAL LIFE

nourishment, forcing into rapidly recurring broods the
development of their young. |

Our common flies are highly organised. Though
the house-fly is the first animal we meet, it is the last
we know. Concerning it, as of most familiar animals,
Aristotle’s apophthegm holds good, that what is first
in nature is last in genesis. The fly, like all beings, is
an old hand, yet historically it, is a new-comer, and
proclaims the fact in its structure, habits, and life-
history.. We may therefore lead up to it by some less
specialised forms—namely, the mosquitoes.

Of this large family the gnats, mosquitoes proper,
and the harlequin flies may be taken as examples.
The first may be roughly distinguished by its habit
of resting on its fore and middle legs, holding the last
pair in a raised position ; the second, by its yellow and
black colouring; and the last by its habit of raising
the fore-legs when at rest.

The Gnat.—The two sexes of the common gnat are
easily distinguished. The male has bushy antenne,
the female has slender antenne with inconspicuous
hairs inserted at each joint. The males associate in
large companies that dance over the country-side,
whilst the female is more solitary and rests often in
outhouses and near or in dwellings. Lastly, the blood-
sucking habit is peculiar to the female.

In early summer the female lays her eggs in little
boat-shaped floats, on the surface of water standing
in butts or on marshy ground. The float is rather
less than a quarter of an inch long, and contains

LIFE-HISTORY OF THE GNAT 249

250 to 300 eggs. Each egg is cigar-shaped, with the
narrow end turned upwards, floating with the tip
projecting through the surface-film into the air. By
this means the float is made self-righting, for if sub-
merged it carries down between the pointed egg-tips
a bubble of air and almost instantly rises again to
the surface perfectly dry. The ‘surface-film’ is an ex-
pression of the elastic property of the surface particles
of water. The tenseness of this film is readily seen
in soap-bubbles, and the use of it by insects has led
to many biological adaptations. In the present case
the hold which the eggs gain on the film provides
them with a constant supply of air.

The next day the larve hatch out. They differ
from the early stages of the insects so far considered
in havingnolimbs. Each larva is a minute, colourless,
worm-like organism, consisting of a small head pro-
vided with biting mouth-parts, a swollen thorax of
three segments, and a segmented abdomen, at the
tip of which are some peculiar processes. The be-
haviour of the gnat-larva is characteristic. When at
rest it hangs head downwards from the surface-film.
From time to time it releases its hold and descends
passively, then wriggles again to the surface. This
swimming movement is performed by bending the
body into double and reversed curves, and progresses
tail foremost (fig. 52).

The larva gains a hold on the surface-film by
means of a peculiar projection—the siphon—attached
to its tail. This siphon is a tube opening by fine flaps

250 ANIMAL LIFE

which may converge to a point and close, or may

diverge and open.

Fic. 52.—The larva of the
common gnat (Culex
pipiens) inits characteristic
attitude. It is attached
to the surface-film of the
water by its breathing
siphon, and hangs head
downwards. (/rom Miall’s
‘Natural History of
Aquatic Insects.’ By
permission of Messrs.
Macmillan & Co.)

Connected with the siphon are

breathing tubes or tracheze
that supply all parts of the
body with air, and in particular
a little group of tracheal gills
placed near the siphon. Ac-

cordingly, when the larva rises

to the surface it closes the valves
and so pierces the surface-
film. It now opens them, and
they rest upon the elastic film-
membrane without breaking it,
just as muslin or gauze remains
unwetted. The pull of the film
on the five-lobed plate suspends
thelarva. To descend, it closes
the valves, thus reducing the
tension, and is drawn down-
wards by its own weight. The
food of the larva consists of
minute organisms which it
sweeps into its mouth by the
tireless action of its jaws.
After three or four moults,
being a week old, the larva
passes into the pupal state for
two days, but, unlike the pupe
we have so far considered, that

of the gnat isan activeorganism. It consists of a large

LIFE-HISTORY OF THE GNAT 251

globular anterior mass (the head and thorax), and of
a flexible abdomen. Unlike the larva, however, it
now comes to rest at the surface-film with the globular
head upwards and the tail downwards. This change
in position is significant, and is effected by two hairy
horns or minute trumpets that project from the back

Fic. 53.—The pupa of the common gnat in its characteristic attitude. The
respiratory trumpets (S) maintain a hold on the surface-film of the
water. The wings (W), legs, antennz, and mouth-parts can be seen.
Of the mouth-parts Zzé is the large upper lip, M7x and Jaf the lower
lip. 7724, refers to the first leg ; 776,, to the second legs, the third
is seen under the wing.—(4/ter Hurst.)

of the thorax. These are now the outlet and inlet
of. the tracheal system. The hairs lining them
suspend the body by the tension of the surface-film,
whilst a stroke or two of the tail, aided by the tail-fin,
severs this hold and carries the pupa downwards,

252 ANIMAL LIFE

ascent being a passive movement. The significance
of this change in posture is seen when the fly emerges.
The crack through which this occurs lies on the
thorax, and if this were submerged the gnat would
drown. Hence the advantage of carrying the arched
thorax uppermost. The gnat at once gains the air,
straightens and dries its lancets, antenne, legs, and
wings, fills its air-tubes, and flies away.

The Mosquito.—The mosquito (Anopheles) passes
through a life-history similar in all essentials to that
of the common gnat. Its larva may, however, be
recognised by certain peculiarities, of which its habit
of lying horizontally instead of vertically is one of the
most obvious. The mature insect is found in most
English counties, but is most abundant along the
chief river-valleys and over the Fen district. This
distribution agrees closely with the occurrence of ague
in former times, and the spread of this fever is now
generally recognised as the work of the female mos-
quito. Allied forms are even more noxious in this
respect, and it is certain that malaria is caused by the
infection of germs of the disease introduced into the
blood during the act of sucking.

The Harlequin Fily.—Of the vast number and
variety of midges and of gnat-like insects that succeed
one another with the course of the seasons, but few
are adequately known. In a casual view they are
lumped together by their general superficial likeness,
and their assumed uniform taste for blood. The
professional naturalist splits them into a vast array

=

LIFE-HISTORY OF CHIRONOMUS 253

of species, on the assumption that they all breed true,
and it may be that he is right. But until we know
the life-histories of the spring and autumn broods of
the same gnat races, there is a possibility that seasonal
forms of the same species may occur, and that these
may have been regarded as of specific instead of
varietal] value.

The harlequin fly (Chironomus) is one of the
commonest insects that are mistaken for true gnats.
It possesses a form similar to that of Culex, and is
found in like places under similar conditions, but it
can be recognised by the entire absence of a proboscis.
It can neither pierce nor suck, and in all probability
does not feed.

The eggs of Chironomus are laid in gelatinous
strings about an inch long, moored to the banks of
streams and the margins of troughs. The jelly is
traversed by twisted fibres about which the hundreds
of eggs are arranged spirally. These egg-ropes are
an interesting adaptation to aquatic conditions. The
strings moor them elastically. The mucilage protects
the eggs from predaceous and insidious foes. It raises
them to the influence of light, heat, and air, and it
enables the eggs to be spaced out without over-
‘crowding. Incidentally this transparent envelope
permits direct observation of the development, as
Professor Miall’s books have so fully shown.

In a few days—three to six, according to the
higher or lower temperature—the larve hatch out of
these eggs. They are colourless vermiform organisms,

254 ANIMAL LIFE

and move actively by reversed figure-of-eight twists
of the whole body. The head is small and differs from
that of a Culex-larva in having rasping teeth instead of
a sifting arrangement. The tail-end is marked by a
pair of hooked feet, and between these lies a minute
coronal of four gill-plumes. The larva has no opening
to its tracheal system, and does not attach itself to the
surface-film. On the contrary, it buries itself head
downwards in a burrow or case formed by particles
of mud glued with saliva, and if the water contains
sufficient air the larva respires by gentle undulations
of the tail, causing a current that. flows over the
skin and tail-filaments. It only leaves the burrow
at night. If the larve live on a hard bottom they
form a portable case of débris. Larvze which inhabit
stagnant or sewage-water acquire a red colour (hence
their name, blood-worms), whereas those of aerated
water are greenish. This difference of tint is due
to the presence of red blood in the one case, and of
colourless blood in the other. The red colouring
matter is identical with hemoglobin, and its presence
confers increased respiratory efficiency on the blood,
in virtue of which the harlequin fly can pursue its
larval life in foul water and at considerable depths.
This is not the only adaptation enabling these larve
to utilise very small quantities of oxygen. The
surface-forms which can utilise the dissolved oxygen
have no tubules at the hinder end of the body, whilst
those which inhabit deeper water have two pairs of
vascular tubes on the last segment, and these in all

LIFE-HISTORY OF CHIRONOMUS — 255

probability help to increase the respiratory surface
of the skin.

The length of the larval life of Chivonomus varies
with the seasons. Spring larve grow rapidly, and in
a few weeks pass into the pupal stage, whereas the
autumn broods grow more slowly and do not pupate
till the winter is over. Before this stage is reached
the rudiments of the future wings and legs can be
detected as coiled tubules lying in the thoracic seg-
ments. When the last larval skin has been cast,
these and other organs of the fly can be seen more
clearly. They form a large mass occupying the
anterior end of the pupa, from the thorax of which
a pair of tufted filaments projects freely. This portion
of the body sways above the mud, below which the
rest is concealed. The tail-tubules have disappeared,
and a broad fin has formed which is used for move-
ment through the water. In two or three days the
thoracic filaments have extracted sufficient oxygen
from the surrounding water to render the pupa buoyant.
The oxygen is stored in the tracheal system, which
rapidly becomes fully developed. The pupa now
floats at the surface, and on the last day or so inhales
air directly from the atmosphere through the spiracles
or breathing holes. At length the pupal skin splits
along the thorax, the fly creeps out, dries its wings,
and in less than a minute flies away.

The life-history of Corethra,-a close ally of Chiro-
nomus, is almost equally easy to follow. In still pools
the early stages of this gnat-like insect are developed

256 ANIMAL LIFE

from eggs arranged in spiral lines on a flat gelatinous
sheet. The larva is of a glassy transparency, and lies
still and horizontal below the surface of the water,
only changing its: position by an instantaneous jerk,
and again floating motionless. The momentary
gleam as it turns reveal its presence, and has gained ©
for it the name phantom-larva. Upon: closer ex-
amination these organisms are found to resemble
fig. 52. The head bears antenne, two complex eyes,
and a peculiarly constructed mouth enclosed between
the two lips and the jaws. At the back of the throat ©
is a fringe of stout bristles arranged like the bristles
of a lobster-pot, so as to strain the food, the result
being that no opaque substances collect in the body
and break the transparency of the larve. The food
itself consists, according to some authorities, of small
creatures which are caught by the antenne and
chewed up in the mouth; according to others, Core-
thra-larve feed on the fine microscopic life of ponds.
The horizontal attitude of the larva in the water is
aided by two pairs of vesicles filled with air or gas.
These air-sacs are special expansions of the reduced
tracheal system which runs as a closed pair of tubes
down the body, and is filled by diffusion.

The further history of Corethra resembles that of
the gnat. The organs of the fly appear as convolved
protuberances. A pair of air-trumpets sprout from
the thorax and lead into a new system of tracheal
vessels. The old tubes break down, and the contained
gas collects into a bubble beneath the thorax. The

LIFE-HISTORY OF MIDGES 257

pupa appears and floats vertically at the surface of
the water. It emits the fly directly to the surround-
ing air. . : |
Owl-Midges.—Allied to the gnat-family is that to
which the midges belong. Of these numerous and
varied forms, the minute Ceratopogon, or owl-midges,
are amongst the most familiar insects. They form the
clouds of minute hairy-winged insects that emerge at
sunset from cover, and sting with the virulence of a
mosquito. Allied to these owl-midges are other species
with smooth wings. The larve of these insects have
a simple worm-like shape, Those of the hairy-winged
midges live on the sap of. wounded trees, and under
the damp bark of dead timber, creeping, and even
swimming about with great activity. The larve
of the smooth-winged midges are commonly met
with among the conferve at the surface of ponds,
and are also active swimmers. In this stage the
midges pass the autumn, winter, and early spring.
About May the pupal stage is assumed, which is
characterised in the midges, as in certain other insects,
by its retention of the shrivelled larval skin attached
to its tail. Towards the end of this month, or a little
later, the winged form appears, only too abundantly in
enclosed gardens and the neighbourhood of water.
The Black-fly (Simulium).—The varied adaptations
of dipterous larve to life in running and stagnant
water are of considerable interest, and from the acces-
sible, though still imperfectly known life-histories, we
may quote two that illustrate these modifications.
S

258 ANIMAL LIFE

The black-fly (Simulium) illustrates. the first; the
hovering fly (Evistalis) the second.

Simulium is aminute insect about one-seventh of
an inch in length, and appears to be a relative of
Ceratopogon if not closely allied to it. It is found in
marshy places, flying about in great swarms in a slow
and heavy manner, the fore-feet being kept in continual
movement, and evidently employed as feelers. Though
perfectly innocuous in this country, Simulium is one
of the greatest scourges to which man or beast is
exposed in Lapland, Hungary, the United States, and
Australia. Horses, cattle, and buffalo are especially
affected by this midge. A characteristic difference
separates the sexes. In the male the head is much
enlarged in consequence of the much greater develop-
ment of the eyes, the upper facets of which are larger
than the lower ones. The eyes of the female remain
small and undifferentiated into dimorphic facets. The
males swarm high in the air, whilst the females remain
at lower levels. Both sexes occur in the late spring,
and again in August.

Simulium lays its eggs in gelatinous masses on
water plants that border rapid streams. The larve
occur in clusters on leaves and stones, and are of such
curious form and habit as not readily to be taken for
insects. In appearance they resemble minute black
leeches. The cylindrical body is fixed by a terminal
sucker, in order to resist the current, and is provided
at its free or head-end with a second sucker and a pair
of revolving fans. When alarmed, the two suckers

LIFE-HISTORY OF SIMULIUM 259

are employed exactly like those of a leech, and in a
few moments the larva creeps back to its first hold-
fast, even if it has to work against the stream. How
this is done can be understood by placing a white
disc under the leaves. Against this background a
web of dirty threads can be seen, and, as the larve
drop, they spin a fresh line; along this they climb
with theirsuckers. It is on these lines that their safety
largely depends, and with their huge spit-glands they
are constantly extending them as they move to fresh
quarters.

These glands are also used for another purpose.
Before pupation the black-fly larva makes a conical
nest against a weed-stalk, and in this nest the pupal
stage is passed. The larva, head downstream, con-
structs its chrysalis case of the hardened secretion of
its glands, and then proceeds to undergo its trans-
formation. At first the nest is closed, and only
after the last larval skin is cast does the broad pro-
jecting end open, and then out there come the pupal
head and the thorax, with two sets of breathing fila-
ments, like those of the pupa of the harlequin fly.
The pupa, fixed within the nest by hooks along its
abdomen, is swayed with every movement of the weed.
In moorland streams the vegetation is often thickly
covered with these strange inanimate-looking tufted
excrescences, within which all the organs for aerial
life are developing or completed:

How, from this submerged fixed pupa, the fly

could safely emerge was long a problem. Unlike ~
$2

260 ANIMAL LIFE

those of the other gnats and midges, this black-fly pupa
does not float and cannot leave its nest, yet the flies
pass the gauntlet of the stream. They emerge safely
in thousands, and may be seen clinging to weeds on
the borders of the stream. The method of hatching is
singular. The pupa not only stores air in its breath-
ing tubes by diffusion, but actually distends its skin
therewith, and so separates it from that of the fly.
Ultimately the pupal envelope bursts and the fly
emerges, still with intricately contorted appendages,
and surrounded by a bubble that clings to its hairy
covering. Inamoment it rises glistening to the surface,
where the bubble bursts. Its legs spread out with
almost explosive suddenness ; with these it easily runs
on the surface-film, climbs up the nearest support, and
then expands and dries its wings.

The Drone-fly (Eristalis).—In great contrast with
these remarkable adaptations of midge-larve and
pup to life in flowing. water, are those shown by
the drone-flies, and some daddy-longlegs in their
earlier stage of development. The larve of these
flies are elongate, whitish, worm-like maggots, with a
long rat-like tail. Their breathing tubes are well
developed, and open to the surface at the tip of the
tail. By the aid of a telescopic arrangement this tail
can be protruded to a length of some inches, so that
while the larva is buried deep in mud, its breathing
tubes can reach up to the surface of the water, break
the film by the point or hooks of the tail and acquire
a supply of fresh air. This arrangement is most-highly

Lf

”

LIFE-HISTORY OF THE DRONE-FLY 261

developed in the drone-fly (Evistalis) larva, a scavenging
creature that does immensely valuable service in render-
ing stagnant water and decaying substances innocuous.
This larva, the ‘ rat-tailed maggot,’ though only two-
thirds of an inch in body-length, can extend its tail from
half-an-inch to four inches in length, drawing it out to
a mere colourless thread, and at the least alarm
shutting it up in a flash. The mode of feeding no less
than the breathing of this animal shows a most complex
form of adaptation. The organic débris on which it
lives is highly innutritious, and a special collecting
apparatus has arisen to enable the bee-fly larva to
make good the lack of quality in its nutriment. This
apparatus is a strainer opening inwards, placed between
the mouth. and the gullet, and dividing the gullet
into upper and lower chambers. The larva roots
about with its flexible muzzle, and, having loosened
a quantity of débris, gulps down a mouthful. This
passes easily through the strainer and is sucked
into the upper chamber. Then the water is forced
back, filtered through the fringes, and discharged
through the mouth, whilst the food is left stranded on
the strainer. The process is repeated again and again.
When a sufficient quantity has accumulated it is
converted into a bolus and swallowed. The action of
the fringes is curiously like that of the baleen-plates
of a whale.

When this rat-tailed larva is about to pupate,
it leaves the water, enters damp earth, and conceals
itself beneath a cocoon made of the larval skin, dis-

262 ANIMAL LIFE

coloured and hardened. Within this, its organs undergo
profound changes, and new ones appear. Two pairs of
horns project at the head-end and form the respiratory
openings of the pupa. The tail severs its connection
with the body. The wings, legs, and elaborate pro-
boscis appear, and in favourable seasons the fly is
ready to emerge in eight to ten days from the com-
mencement of pupation.

If we now turn to the terrestrial larve of the
two-winged flies we find that they affect such a great
variety of habitat and food, and undergo their develop-
ment at such varying rates, that a whole volume
would not exhaust the subject. |

There is every transition, from the terrestrial to
the aquatic habit, from the free-living to.the purely
parasitic mode of life. The possibilities of nature
seem to have been almost exhausted by these insects
in their efforts to fill every available niche that shall
afford nourishment for the growing period, retirement
for the development of the pupa, and exercise for the
instincts of the imago. In particular the value of
heat has been utilised to the utmost as a means of
assisting growth and development, and so producing
swarm after swarm in a single summer.

The many tribes of blood-suckers use this stimulating
nourishment to force their progeny. The parasitic
larve hasten their development in the warm hides
of flocks. When these hot-houses fail, cold-blooded
animals, vegetable juices, fungi, pools in hollow trees,
serve as substitutes. Only one advance seems possible

LIFE-HISTORIES OF FLIES 263

in perfecting the adaptations of Diptera; that is the
step taken by the next group. Were division of
labour adopted by flies as by bees, it is doubt-
ful whether domesticated animals would survive
or vegetation flourish. But in all the unequalled
variety of dipterous habit, there is no indication of
the adoption of communal life. The common house-
hold flies and the horse-flies are individualists of the
highest order. In no other animals are the two diverse
ends of life so strongly emphasised. In none are they
embodied in more glaring contrasts than in the inactive
maggot and the brilliant hovering fly, the one a —
nutritive centre, the other with only the need of
drink to ally it to earth. In no other life-history is
the transition so rapid and abrupt. The chief larval
tissues are resolved to a cream, and are rebuilt ina
week to form a far more complex and active being.

There is no comparable adaptability elsewhere to
ensure as these flies do, the forcing influence of heat
and stimulating food, or to utilise borrowed animal
heat and nourishment in order to produce, not eggs,
nor even young larve, but a full-grown larva, or even
pupa, which needs but a few hours to complete the
issue of the fly. And the genius of the Diptera lies
in this, that without forsaking their hold on the old
inexhaustible vegetarian diet, they have been drawn
by the attraction of smell to the new kingdoms of
mammals and birds, with all that goes in their train.

The Hymenoptera.—The care of the young is most
efficiently performed by the Hymenoptera.

264 ANIMAL LIFE

Although many other orders of insects lay their
eggs on food suitable for the young, it is only among
ants, bees, and wasps that nests are constructed and
stored with specially prepared food by mothers that
never see their young, or by workers that have no
children. In this, the highest group of insects, indi-
vidualism and collectivism are worked out in the most
bewildering variety of detail. In no other group of
animals is the community and communal action
more fully realised than by bees and ants. The very
existence of castes,.queens, workers, and drones is
controlled by the future of the race. Their numbers
and activity are decided by, and devoted to, the
welfare of the community. The construction of the
nest and cells or comb, the laying of eggs, and storage
of special food in the egg-cell, and in reservoirs against
bad weather, the heating of the nest, the provision of
suitable moisture and the succession of swarms—all the
characteristic activities of these Hymenoptera have
no relation to the workers’ individual needs but are
directed to the colonial interest. So dependent on
society do the members become that, in the case of
ants, no isolated worker can live more than a short
time, though normally a long-lived creature, and there
is not a single species of ant which is solitary. So
altruistic are some ants, so specialised for the further-
ance of interests not their own, that they may lose the
power of feeding and cleaning themselves, and depend
for these offices on the service of slaves, whilst their
own activity is devoted to the defence of the colony.

LIFE-HISTORIES OF HYMENOPTERA 265

The more these social creatures are studied the more
clearly does it appear that their behaviour is regulated
far more by future contingencies than by present needs,
and that they present in the organisation of their
communal life and in their adaptation of plants and
animals to their needs and those of their offspring,
a civilisation which though many ways similar to the
early stages of human civilisation, shows a still more
striking resemblance thereto in the plasticity whereby
advantageous seasonal or local peculiarities are made
use of and destructive agencies avoided or overcome.
If we meet with instances of stupidity and inflexibility,
these exceptions do but emphasise a frequent parallel
in human frailty. There is an American saying
that the ant is King of Brazil, and only want of sub-
limity of form prevents: us from confessing the ant as
king of animals, for in it intelligence rules as well as
instinct, and has controlled a civilisation of caste that
is devoted beyond human parallel to the welfare of
the state.

The common ants, bees, and wasps are, however,
only a fraction of the order Hymenoptera. In addition
to the more familiar social members of these groups
there are large numbers of solitary bees and wasps
whose care for their young is no less wonderful. Just
as we study the smaller races of mankind, or the in-
significant early traces of dominant nations, in order
to understand the complex forms of western or eastern
civilisation, so the dominant familiar insects only
become tolerably intelligible when the less highly

266 ANIMAL LIFE

organised economy of their simpler allies is made
known. | 7

Amongst these less impressive forms are the
saw-flies, gall-flies, and ichneumon-flies. The saw-flies
are easily distinguished by the absence of a ‘ waist,’
and the possession, in the case of the abundant female,
of a sting-like organ consisting of two remarkable saws
and their supports. By the aid of this apparatus the
mother fly is able to cut passages into the leaves, stems,
or trunks of plants before depositing her eggs therein.
The gall-flies are minute, pitchy-black, thin-waisted
insects which may be identified by their straight
antenne. The ichneumons are thin-waisted and often
brilliantly coloured insects, the mothers bearing a
usually long sting-like weapon for depositing their eggs
in or upon the bodies of caterpillars.

Saw-flies—The saw-flies of the rose, gooseberry,
currant, and turnip do an immense amount of mischief
in this country, and abroad, where the conditions are
more favourable, their ravages are correspondingly
severer. The gooseberry fly lays its greenish eggs
along the mid-rib of the leaves, and from them there
issue in a week minute white larve with twenty legs
and sucker-like feet. At the first moult they assume
a green colour spotted with black, and in many ways

resemble true caterpillars, as, for instance, in colouring _

and attitude and in the possession of prolegs. After
feeding for a month they become yellow in tint, creep
down to earth and pupate, or may hibernate and
pupate in the following spring.

LIFE-HISTORIES OF GALL-FLIES — 267

Gall-fies—In contrast to the free-living larve
of saw-flies, the gall-fly’s young spend their whole
life within excrescences on oaks, willows, and roses.
How these galls are made has long been a moot problem.
That some great advantage is gained from these local
inflammations of plant-tissues is clear, both from
the great variety of gall-forming creatures and the
close association in one and the same gall of diverse
insects, some of which have entered it after the
inflammation had begun ; and it seems probable that
the attraction is due to a very concentrated form
of easily digestible, nutritious, and inflamed tissue.
Each plant responds in a characteristic fashion. The
bedeguar or rose gall, and witches-brooms on birches,
are modified shoots ; the oak-apple is an aborted leaf ;
the willow-spot is merely an inflamed part of a leaf ;
and it was long thought that the plant parasite, be it
fly, scale, or mite, inserted an irritant fluid with its
egg into the bud or leaf to which each plant responded
by these several wonderfully specific outgrowths,
thereby concentrating tender rich juicy tissue into a
compact space about the egg, and so furnishing a
supply of stimulating food to the larva. In the case
of the gall-flies, however, irritation does not usually
follow the insertion of the egg until the larva hatches
out, and there sometimes follows an interval of ten
months before the gall begins to grow. From such
observations it has been concluded that the gall is
due, not to an irritant fluid injected by the parent,
but to something secreted by the larva ; and the cases

268 ANIMAL LIFE

where gall-formation has undoubtedly begun before
the time of hatching are probably to be explained as
due to the influence of the larva making itself felt
through the egg-membrane.

The larva of the gall-fly having no cause to wander
in search of food, and being shut off from most of the
changeable conditions of free life, possesses a simpler
structure than that of the saw-fly. Its colour, like
that of most hidden animals, is white. No limbs
are present and the bent body merely turns about
from side to side, as it slowly drains the wall of sappy
or pulpy material that: has grown around it. This
supply lasts it for several months, after which it pupates
and issues as a fly in the next spring. In many cases
it has been found that the gall formed by it in turn is
different from that which produced it, and whilst the
first generation is entirely composed of females, the
galls, stimulated by their larve, produce in the next
season both sexes ; and this generation is so different
in appearance that it was for some time considered to be
a totally distinct form. - To what cause we can attri-
bute this difference in the two successive generations
is not yet thoroughly clear, but the fact that the two
galls are unliké, points to a slight difference in the
food. The-influence of change of diet upon young
insects is known to be a far-reaching one, and as any
check in the flow of sap is sufficient to convert an
aphis of one kind into an aphis of a different category,
and as a stimulating food will produce a queen bee
from a worker egg, so it may be in this case, that a

i

SOLITARY WASPS 269

difference in the position of the two galls or a variation
in the quality of the sap at different seasons will lead
to an explanation of the fact that the gall-fly has
two differing generations. |

The act of piercing the skin of plants, and of then
laying eggs in the puncture so produced, is performed
independently in many groups of insects by the same
complex surgical instrument. It is, however, only in
the higher Hymenoptera that the organ becomes, by the
addition of a poison-bag, a sting. The value of this
office is best seen in the solitary wasps.

Solitary Wasps.—The social wasps are so familiar
that the term wasp has become almost synonymous
with the species that form communities ; and to many
the less impressive solitary wasps are quite unknown.
Yet they are common enough in this country, and their
habits excited the admiration of observers before the
beginning of our era. Few of those who have lived
in the country will have failed to notice the absorption
and persistence with which a ‘ fly’ will have estab-
lished its quarters in a keyhole, dressing-table, or some
other part of the furniture which may be reached
from an open window or door. The movement and
the life of the house makes no difference to the constant
visits paid by this insect when its mind is once made
up to fix its abode there. With unerring certainty
it flies in by a straight course, executes its business,
and flies away by an undeviating line. Should the
spot be examined the insect will return and hover
impatiently until its task can be resumed. The work

270 ANIMAL LIFE

itself is a mass of clay worked, sometimes with stones,
into a vase-like or irregular shape. When broken
open the nest is found to contain a surprise, for instead
of the white wasps’ comb, or the grubs that we should
perhaps expect to see, a mass of caterpillars is revealed.
The caterpillars are all of one kind, and usually to all
appearance dead. But if dead they have none of
the shrivelled appearance that in a few hours over-
takes a caterpillar killed by ordinary methods of
starvation. These larve are still pliable and fresh in
colour. They have no trace of the rank smell that
issues from a naturally dead larva, and, if we keep
them, they will long remain as fresh and healthy-looking
as in life. But not one will come to life again. Ina
few days the wasp disappears, and may not return.
It is clear that the extraordinary store of preserved
caterpillars is not touched by the wasp. If the nest
is not hopelessly destroyed by examination, it will in
the course of a month produce one or more wasps
of a like kind; but at the expense of the caterpillars.
Either, therefore, the caterpillars become wasps or
are in some indirect way transformed into wasp-bodies.
The Chinese, from the time of Confucius at least, have
noticed this strange transformation, and suppose that
the wasp addresses to the caterpillar a message or
spell “to mimic me.’ This the resigned caterpillar
to all appearance does, and to this day the word ‘ Jiga,’
or “mimic me,’ is the name by which the wasp is
known in China.

The disappearance of the caterpillars is rendered

LIFE-HISTORIES OF SOLITARY WASPS 271

less mysterious if we open the nest at an earlier period,
for then one or more white grubs will be found
devouring the fresh food by which they are sur-
rounded. The supply is, however, usually sufficient
to enable the young to attain their full growth, and
to pupate successfully. Careful examination of the
earliest stage will reveal one or more eggs prone or
pendent, which are laid by the wasp among the store
of moribund caterpillars in the still earlier formed
clay nest.

There is no’doubt that the wasp makes the clay
with its saliva, builds the nest, stores it with a par-
ticular insect, and then, after laying an egg or two,
leaves the warmth of the situation to complete the
development of its young. The entire work falls upon
the female. :

Sand Wasps.—These solitary wasps are of diverse
kinds, and many dig burrows in the ground, construct
cells of pottery, or tunnel into wood. In all cases it
is the female wasp exclusively that does the work.
The males usually live for a short time, and take no
part in the construction of the nest or the care of the
young. Ammopiila of sandy districts is well known
(Peckham, Fabre, p. 300).

For digging its burrow this wasp uses mainly the
same instrument that others employ to collect earth
for pottery work—namely, its strong jaws, aided
by the first pair of legs. Having selected a spot on
suitable ground, and on a hot day, the red-banded black
Ammophila picks away thé earth until she is partly

272 ANIMAL LIFE

hidden ; she then carries it away, backing out of the
hole with a pellet in her mouth, flying a short distance
and ‘ flirting’ the load away from her, repeating the
journey until the ground is clear for further excavation.

The burrow is now deepened, and a storage chamber
of much larger diameter is formed. When this is
finally accomplished and the soil and stones removed,
the wasp proceeds to cover up all traces that might
lead to the detection of its burrow. She selects a
stone or large lump of earth, and tries the effect of it
as a stopper. - Sometimes, as if satisfied, she proceeds
to kick loose soil over the top to disguise all traces
of her activity, more frequently the first, and many
succeeding stoppers are rejected and more excavation
must be done before the critical worker is satisfied,
and finally, perhaps, a big lump is firmly wedged in
with smaller stones and earth. |

The next process after the construction of the nest
is its storage with suitable food. For this purpose
each wasp has its special and invariablechoice. Though
ripe fruit or nectar form their own food, that of the
larva must be of animal nature and perfectly fresh.
The wasp therefore now devotes herself to a hunt
in which her own choice takes no part. It is the tra-
dition of some to take flies, of others to select beetles,
grasshoppers, spiders, caterpillars, or bugs. More-
over the selection when so narrowed is not indiscri-
minate, and usually one, or at most a few, of the
selected class are captured for this purpose. The
work, therefore, is rendered most arduous. Ammo-

HUNTING METHODS OF AMMOPHILA 273

phila quarters the ground and thick forests of herbage
for caterpillars. Having found one she attacks at
once, and tries to bite and to sting it. The caterpillar,
however, flings itself about, strives to gain cover and
repulse its foe, not infrequently, it would seem, with
success. But on occasion the wasp succeeds in
gripping the larva, and then standing high on her
legs, and disregarding the struggles of her victim,
she curves her abdomen under it and _ plunges
her sting. The caterpillar instantly collapses. For
some moments the wasp remains still. Then with-
drawing her sting she plunges it into two more inter-
segmental grooves, each time nearer to the head, then
she circles above it, and again descends and repeats
the assault nearer the tail of the larva, stabbing it
four times more. The attack over she pauses, cocks
up her tail, washes and rubs her face thoroughly and
completes her toilet. Her next task is to drag the
heavy prey to thenest. Holding it with her teeth and
forelegs she passes rigidly over rough ground, standing
corn, or garden plot, where there is nothing to suggest
the right direction. Yet over all this, for sixty
feet or more, she travels without hesitation, pauses,
lays her burden down, and presently removes a stone
or two and reveals the nest ; then hurriedly returning
to the caterpillar she picks it up and takes it to the
burrow. There she drops it and, backing in, catches
it with her mandibles and disappears. When the
caterpillar is secured a single egg is attached to its
skin, and then the Ammophila goes out again hunting
a

274 ANIMAL LIFE

for another. On the average she finds one a day,
and when the second is found it is sometimes only
slightly stung and then softened and rendered pliable
by forcible pinching. This done the wasp carries
it off and deposits it as before, guided by the same
inscrutable, intimate sense of locality back to its
hidden nest.

The store is now complete, and the Ammophila
proceeds to fill up the burrow. In this finishing
process, as in the initial one, she shows remarkable
individuality of behaviour. Some wasps carefully fill
the hollow, smoothing the surface, sweeping every
particle away, and trying the effect of a leaf, or twig,
as a finishing touch. Others merely scratch a little
loose earth into a perfunctory burrow. Others again
give an extra finish by using a selected stone in their
mandibles to beat the surface hard and smooth.
The site is then deserted, another is chosen and the
work of learning a new locality thoroughly, of making
and stocking a new burrow are gone through afresh.

The incessant ardour which these attractive solitary
wasps exhibit in nest building and storing is a won-
derful feature. As a rule they work without ceasing
from dawn to dark, retire to roost in long grass or under
clover about seven or eight o’clock, and after shifting
from one posture to another, sleep soundly until
about five, though some do not get up till eight.

Their strenuous encounter with poisonous spiders,
or powerful crickets and grasshoppers ; their ways of
carrying or concealing the prey until the burrow is

SOCIAL WASPS 276

enlarged to allow it to pass in, the construction of mud
cells by some, of earthy hollows by others, are fixed
habits of the several kinds of wasps.

Nevertheless, a certain improvement in their
habits, due to experience, is undoubtedly exhibited
by many. The adoption of chimneys or eaves of
buildings is an improvement on the older method of
using hollow trees or shelving rocks. Again, the
spider-hunter has found that to hang up its prey
in a fork while finishing the burrow, instead of leaving
it on the ground, is a safeguard against ants. She
has also found that by cutting off the spider’s legs
more booty may be stored in a given space, and
though exceedingly conservative in going through the
operation by putting it down at the burrow’s edge,
investigating the nest and then pulling the spider down
into it, yet she is not such a slave of custom as to be
unable to adapt her action to changed circumstances,
and if the spider is repeatedly removed while the
wasp is in her burrow she will ultimately abandon the
preliminary survey and drag her prey straight down,
going backwards.

Social Wasps.—The chief advance made by these
more familiar wasps over the solitary species lies
in the evolution of the worker. The care of the young
in the solitary wasps is entirely the work of the mother,
who is both queen and worker. For the first few weeks
of spring the same is true of colonial species, but, later
on, the construction, protection, and provisioning of the

nest is taken over by the workers, whilst the queen,
¥.2

276 ANIMAL LIFE

relieved of these duties, confines her labours to stocking
the cells with eggs. |

With the first warm days of the year, the queen
wasps issue from their several hibernating places and
quarter the ground in search of suitable sites in which
to found the colonies. A hollow tree, a shelving bank,
or an earthen crevice provide the necessary protection,
and having selected the site the queen proceeds to
build her nest. The substance employed for this
purpose consists of wood-fibre, chewed to a pulp and
thoroughly mixed with saliva till it forms a paper-like
substance. With this wood-pulp the queen constructs
the foundation, central support, and covering dome.
To the underside of the dome she next affixes a few
hexagonal cells. In each of these she places an egg,
adds honey, and closes the aperture. In this way
the first comb or tier of cells is prepared. The develop-
ment of the brood is rapid, and issues in a small
swarm of workers, which remain in the nest, as they are
incapable of founding a new colony. They enlarge
the existing cells and add comb after comb of new
ones, stocking each cell, when the queen has laid in it,
with honey and pollen. They extend and strengthen
the dome and narrow its entrance, so as to form a
small circular opening, such as is shown in fig. 54.
Throughout the summer, brood after brood of workers
issues from these combs, so that in September they
form a plague in the neighbourhood of the colony.
Finally a few queens and drones are born, probably
by reason of a highly nutritious nitrogenous diet.

SOLITARY BEES 277

The appearance of these royal members marks the
decline of the colony. The workers and the old queen
perish, the nest is forsaken, and is soon demolished
by shrews and other animals, and of the rest only one
or two queens persist to carry on the laborious work
after a long sleep in winter quarters.

Solitary Bees.—The care of the young is a no less
fascinating study in the solitary bees. In early spring

Fic. 54.— Nest of Common Wasp.
(From a specimen in the Manchester Museum.)

one may see these little burrowers preparing their
nests on sandy banks, selecting bramble stalks and
other hollow stems, or reconnoitring shells and
crumbling walls. As the solitary wasps are to the
social ones as cave-dwellers to fortunate citizens, so are
these bees to the hive bees.. They work incessantly
during the summer, and then, with few exceptions,
both dwellings and dwellers perish. The males are often

278 ANIMAL LIFE

very unlike the females, and there are no workers to
divide the labour of cell-making and honey gathering
from the work of the queen bee in founding of the
race. Unlike the solitary wasps, none of them use
animal food for the nourishment of their young.
Honey and pollen have to be stored in increasing
quantity as the larve become more voracious and
insistent in their demands.

Fic. 55.—-The Leaf-cutter Bee (A/egachi/e) that drills its burrows in coastal
pathways. The upper figure with expanded tufted legs is the male.—-
(From a specimen in the Manchester Museum.)

Of these solitary bees the dark-coloured garden
Prosopis is perhaps the most interesting. Not that
she is impressive in appearance, or especially attrac-
tive in behaviour. She has hardly a hair to hide
her nakedness. Her black and white body bears no
baskets to carry pollen. .She cannot produce wax
nor dig dark earth, nor bore wood ; her jaws and limbs
are too feeble, and her tongue too short. Poverty-

PRIMITIVE BEES 279

stricken and solitary she selects a hollow stem, a
mortar or an earthen crevice, and there lines the hollow
with a few irregular cells, enveloped in silk spun from
her mouth. These she stores with a little wet honey
and with pollen, which she scrapes into her mouth
with her feet and then carries in her stomach, and
soon after perishes.

The reason why Prosopis is interesting lies in that
significance which gives to all antiquities their real value.
Dominance, vigour, high and complex organisation
appeal to us at once, for of such qualities our own
civilisations partake. But it is not in these manifesta-
tions that we gain insight into the history of the race.
We may realise the qualities that have determined its
distinguishing character, and the complex factors that
have modelled its political life, but the source from
which it sprung is hidden from us by a thousand years
of interwoven crossings of clan and clan, the battles of
kites and crows, the dominance of one line of policy
after another, the gradual disentanglement of the
stablest form of government to suit, now one period,
now another. To understand fully the genius of the
people we have to go back to its origins, to the rude
forefathers with their primitive strength, grace, or
enterprise, and so ultimately to the cave-dwellers, the
early hunters and artists. The neglected troglodytes,
unimpressive, too often extinct and unavailable, are
those races which would help us most. But these we
have exterminated or decimated, and such truly original
knowledge as they alone possess is too often lost to us

280 ANIMAL LIFE

for ever. Pyvosopis is one of these antique races.
Her poverty, isolation, and simplicity are no marks

Fic, 56.—Evolution of the tongues of bees: A, trowel-like short tongue
() of Prosopis, with the mandibles (Mn) at its base ; B, jaws of Rose-
cutter Bee (the tongue being turned back); C, elongate honey-sucking
tongue of Humble or Hive Bee. The mandibles (wd) are short, but the
tongue and its adjacent parts (7, f/) are greatly produced.—(A, B from
H. Miller, C from Lang.)

a, antennae ; az, eyes ; ef, dorsal groove foripharyns); lér, upper lip ;
MX,, mm, maxilla

of distress or degradation. Her short tongue and
slender legs are signs of an antique habit that sufficed
the needs of early bee-life, and in the eyes of the

a ee ee! ee

BEES AND FLOWERS 281

naturalist give her a more profound significance than
all the high organisation of the honey-bee. Thegarden
in which she lives is in large measure her own work,
for its flowers and fruits are responses to the stimuli
that countless generations of her descendants have

LAMY) xe /
YUU Nis
RSW T

Fic. 57.—Adaptive structures of the Hive Bee for comparison with fig. 58.
A, Feathered hair for collecting pollen. B, Hind-leg of worker. C,
Inner surface of the part marked x in B to show the stiff hairs for
gathering pollen and the wax-pincers. D, Spur on the middle leg for
removing pollen. E, Comb on the fore-leg for cleaning hairs.— (A//er
Folsom. ‘ Entomology.’ London: Messrs. Rebman, Ltd.)

successively applied to corolla, stamens, and stigma,
as their tongue grew longer, their legs more capacious,
their wax plates more generous. The history of
flowers would almost be a blank, but for the Prosopis
and her vast following ; a hundred thousand varieties
would disappear if the bees did not visit them ;;and

282 ANIMAL LIFE

if we reflect how much human civilisation in its critical
pastoral and tribal stages has depended on agriculture
we realise how greatly we are indebted to these honey-
suckers and pollen gatherers. |

Not all the solitary bees are so destitute as
Prosopis. The majority are well clad, hairy-legged

Fic. 58.— Hind-legs of three Solitary Bees : A, the smooth leg of Prosopis
with no pollen-gathering apparatus ; B, leg of Ha/ic/us with short hairs ;
C, leg of Dasypfoda with great tufts of pollen-bearing hairs.—(A/fter
Miller.) Figures of these bees are given by Sharp (see p. 300).

burrowers. Some carry pollen on their furry breasts,
others on their thighs. Some dig in the ground,
shovelling with their legs, and excavating first a gallery
and then brood chambers which are. stocked with
balls of honeyed pollen. Others construct a tunnel in
a bramble stalk, and beginning at the lower end store
ball after ball and egg after egg, in single file, until

THE BURROWS OF BEES 283

the tube is full. The leaf-cutting bees line their
earthen nests with a layer of leaf-discs and construct
thimble-shaped leafy cells in which to store their
pollen and lay their eggs. The carder-bees drape
some ready chink with wool or cotton which they gather
from plants near by. In these various ways they
lay and feed their young, and defend them against
mould—that most insidious and deadly of their
enemies.

Mouldiness is, however, not the only foe the bees

Fic. 59.—Burrow of the Leaf-cutter Bee (MWegachzle centuncularis).
(From a specimen in the Manchester Museum.)

have to fear. Another and more widespread enemy
is ever ready to annex their ingatherings. The ten-
dency to take what others have gathered and to divert
the store for their own ends exists in all capable
organisms, and amongst bees there is a whole tribe of
cuckoos who plant their eggs in others’ nests. Even
those steady workers, the mason-bees, will, if inter-
rupted, carry their provisions to a neighbouring,
completed cell, and there strive to gain a footing,
and many other solitary bees, if delayed or unable to
finish: their tale of cells, will tear what they have done

Ce al

284 ANIMAL LIFE

to pieces, devour the eggs, scatter the contents, and
start provisioning and stocking afresh.

tw wie 2.

Wi

Le | pi rie >. .

SS Aaleh
ae)
”
Wieens
MO NN

ws aK
qn
fc

Fic, 60.—Section of the burrow of Axdrena, one of the Solitary Bees.
The main-shaft communicates with the lateral chambers in which from
below upwards the stages in development may be seen progressing. —
(From ‘ Riverside Natural History,’ by kind permission of Messrs.
Houghton, Mifflin & Co., U.S.A.)

Evolution of the Hive-bee.—Among these solitary bees
we find the first traces of that fraternal spirit which is
such a dominant impulse in the social ones. The early

EVOLUTION OF HIVE-BEE 285

burrowers in sandy gardens, Halictus and Andrena,
form associations, either by several bees using one
gallery for entering and leaving their private nests;
or by tunnelling close together and issuing in anger
at the disturbance of an intruder whose presence a
solitary bee would overlook ; or, again, by hibernating
in a little buried cluster, perhaps for the sake of
warmth. But whatever advantage is thus gained
is but small. The female bee is maid-of-all-work ;
she is still queen and worker; she lives only for
a few weeks of spring, and dies before her young are
fledged. Her architectural instinct is as yet rudi-
mentary. The rude cells in which she lays her young
are lined with leaves or thistle-down, or stored in an
empty snail-shell, over which she piles a vast mass of
débris.

The first indications of comb-construction are
found in the nest of the four-banded Halicius. This
little bee sinks a shaft into the earth, and at one side
enlarges the burrow so as to form a vault. In this
vault it constructs a row of from twelve to twenty-
four clay cells, arranged in tiers and only loosely
attached to the walls of the vault. The advantage
of this arrangement is that air can circulate more freely
around the cells, and drainage moisture from the
ground does not flow so directly on to them, a protec-
tion from mould that is enhanced by a prolongation of
the shaft below the level of the vault. In spite of
this improvement however, ‘ rot’ kills many of the
larve.

286 ANIMAL LIFE

Origin of workers.—If the efforts of these four-
and six-banded Halictus to combat their most deadly
foe—mouldiness—are not altogether successful, they
have succeeded in another direction. The mother
lives to see her children emerge, and in exceptionally
favourable localities receives help from them in pro-
tecting and extending the colony.

The first to hatch sometimes stay, one to guard
the entrance of the shaft, others to quest for honey
and pollen, or to build and stock more cells. Thus
we have queen and workers for the first time ; but these
workers are potential queens, and only in the richest
districts do they remain to form a temporary colony.
They in turn lay eggs, and from these drones arise
in the late autumn. One of the workers mates with a
drone, becomes a queen and hibernates in the deserted
nest until the next spring.

‘The casual association of the first-born Halictus
with their mother and home becomes a settled habit
in the case of bumble-bees. The yellow and red-tipped
varieties still build underground. The first warm
spring day wakes the isolated queens that have sur-
vived the winter. From their retirement they take a
first flight in search of summer quarters. Each queen
works by herself. The common Bombus sinks a shaft
which she expands to formacavern. Hither she brings
wood, moss, and leaves, then goes out again and fetches
some honey and pollen, and now her behaviour differs
in a marked way from that of the solitary bees. Unlike
them she has the advantage of possessing wax-plates

Pe” * See

he . i. Te

— oe

a at ie ie ie

.

ECONOMY OF BUMBLE-BEES 287

on her tail, and her first step, under cover of the moss,
is to surround with wax a mass of pollen saturated
with honey, construct a cell, in which she lays several

Fic. 61.—Nest of- Bumble-bee showing the barrel-shaped cells hidden
underground in a hollow which leads to the surface by a curved shaft.
—(After J. G. Wood. From Wood's ‘Strange Dwellings” By
permission of Messrs. Longmans, Green & Co.)

eggs, then closes it and rests awhile. A few more
cells are then built, stored with honey mixed with

‘pollen, and closed. By this time, however, the first

larve have hatched, and only being provided with

288 ANIMAL LIFE

little food they soon require further supplies. To
meet this demand-the queen adopts a new method ;
she opens the cells, discharges from her mouth a
little nourishment into them, and then closes up ‘the
openings. A little later when the larve are pupating,
the queen adds to her labours by scraping away the
waxen wall of the cocoon, and thus helps the first
batch to hatch out. This batch is composed of bees
similar in most respects to the queen, except in
point of their smaller size. They are, in fact, fertile
workers, and take part in the extension and nutrition
of the colony. Lightened of her garnering labours,
the queen leaves the nest but little, and devotes herself
almost entirely to the task of laying as the workers
produce fresh cells of wax and pollen. Thus, as the
summer advances, the bumble-bee’s nest, in a bank
or under a stone-heap, is composed of active workers
(the race most familiar to us) and the queen mother,
who rarely leaves the nest.

In the height of summer, however, a change
ensues. By this time the nest presents an irregular
appearance. The old cells are never used again as
brood-cells, but simply form the foundation for new
ones, and are at most stored with pollen and honey,
and altered in size and shape to make honey tubs.
Moreover, the brood-cells are not of a uniform size.
The majority, those that have furnished workers, are
the smallest, but they are all empty; a few excep-
tionally large are to produce queens, and between
the two extremes are a few of intermediate size, in

NEST OF BUMBLE-BEES 289

which drones will be born. Between the queen and
_ drone cells and the worker cells there is thus this
curious difference, that neither of the former contain
any honey or pollen. The eggs are laid in empty
cells, and the larve are fed exclusively on the special
nutriment secreted by the workers ; and the workers
having laid the drone-eggs and finished their building
construction, are now concentrating their attention
upon the feeding of the unborn queens and drones.
To this, as to their earlier labours, it would seem that
they are summoned each morning by a trumpeter,
who acts as ‘ knocker-up’ at three or four o’clock.
This almost incredible statement was made over 200
years ago, and apparently, owing to the lack of a
similar institution among naturalists, has only recently
been thoroughly confirmed. There is, however, now
no doubt that each morning a large worker climbs
on the roof of the nest about quarter to four, and then
for half an hour, or an hour, buzzes loudly while she
also continuously flaps her wings.

The performance is not known to be repeated at any
other hour, and at first one is inclined to regard the
sound as awarning note. However likely this may be,
the beating of the wings would seem to indicate that
the trumpeter ventilates the nest, and that this is the
real object of the performance. If so, the bumble-
bees in this, as in many other ways, foreshadow the
more complete polity of the hive-bees, many of whose
workers take a spell at ventilation exercise during the
midday or evening hours.

U

290 ANIMAL LIFE

Towards the end of summer the colony, which at
its richest and most prosperous phase contained
from 300 to 400 individuals, shrinks to a third of
that population. In autumn the drones and workers
completely die out, and of the queens, a few hidden
in crevices are all that are left of summer’s host.
Boys, mice, shrews, and a host of parasites ravish the
nests, and the moulds complete the work of destruction.
The bumble-bees, therefore, have not solved the crucial
problem of insect life, namely, how to extend longevity
and lessen the ravages of winter. But in the care
of their young they have made immense advance
over the solitary bees. The conversion of the first
brood into workers that systematically remain attached
to their birthplace or move together to a new site,
is the foundation of the caste system. Wax is made
use of for the first time, though carelessly and in
a more or less irregular pot-shape. Jeservoirs for
honey are constructed. Ventilation is improved, and
a distinction made between the nutrition of the first-
formed workers and of the later drones and queens.

In all these methods the social bumble-bees have
improved on the solitary, banded Halictus, as did this
on the simple Andrena and short-lived Prosopis ;
and the line of improvement is for the most part just
that which the hive-bee has brought to such a high
degree.

In this evolution we have referred more than once
to the impetus given by exceptionally good seasons
or surroundings, and have pointed out that it was in

INFLUENCE OF TEMPERATURE 291

connection with such fortunately placed colonies that
the critical advances in organisation were probably
made. It is, therefore, interesting to observe what
result adverse conditions exert on a bee raised to the
middle social condition of the Bombus-class, and the
increased amount of attention to Arctic animals allows
us to do this. We now know, thanks to the twenty
years’ observation of Dr. Schneider, that in some
species of Arctic bumble-bees workers do not occur,
in others they are very rare. These bees, therefore,
have returned to the solitary mode of life, and in
order to utilise the short summer they work by the
midnight as well as by the midday sun. Conversely
it is found that in Corsica there are indications of the
favouring influence of the milder winter. For there,
even in spring, some of the bumble-bees are males
and some females, and the colonies are not so nearly
decimated as in our own climate.

How this last enemy, death, has been prevented
from devastating bee-colonies is the problem, the
solution of which has given the hive-bee its high place
and importance above all other bees. We do not
know with certainty how this critical improvement
was effected, since, in its several forms, the hive-bee
is now domesticated or semi-domesticated all the
world over, and, as is so frequently the case in the
past history of cultivated creatures and plants, we
have lost the wild stock, or stock from which it sprang.
Nevertheless, some indications remain, and these, as we
should expect, are for the most part exhibited by bees

U2

292 ANIMAL LIFE

of warm countries, therefore less familiar and less
accurately known bees than the cosmopolitan Apis
mellifica or honey-bee.

The tropical bees, or Meliponas, that to some extent
bridge over the gap between the bumble-bee and the
honey-bee, are amongst the smallest of their kind, and
hence are called mosquito-bees. They associate in vast
colonies, and build nests in hollow trees, in the soil, in
walls, or among branches. The structure of the nestis
a considerable advance on that of bumble-bees. The
cells are cylindrical, sometimes irregularly, sometimes
regularly arranged, oppositely or spirally in tiers, one
above the other. The special pots for honey, and
jars for pollen, are still more striking than in the
bumble-bees ; and in order to guard them a special
conical cap of resinous wax or propolis is constructed,
open by day but closed at night, and under cover of
this cap a guard is steadily maintained. In some of
these nests the cells are all alike, in others the royal
cells are easily distinguishable ; but by what cunning
nutrition the queens are fed we are not as yet aware.

The caste organisation of these colonies is largely
that of the honey-bee. There is only one reigning
queen to each colony. The workers are now no
longer potential queens, as in the bumble-bees, but
are devoted exclusively to building, storing, nourishing
and ventilating services, whilst the queen has entirely
renounced active life and merely fills the prepared cells
with eggs. The drones, however, are not such wasteful
parasites as those of the honey-bee, but secrete wax

i ii es; be aan

THE HIVE-BEE 293

and assist in the construction of cells. Whether these
Meliponas swarm after the fashion of hive-bees is
uncertain, and has not yet been confirmed.

All those characters that make for efficiency and
permanence are enhanced in the hive-bee. The
colonies are permanent. From each, at the height
of its prosperity, a swarm of workers issues which
is led by the old queen and forms the nucleus of
a new settlement, whilst the workers left in the old
colony rear, by a special food, a new queen from one
of the royal cells, and she, after the destruction of her
royal sisters, assumes the command. The old colony is
thus gradually re-established. The structure of the
hiveis such as to economise space and to accommodate
the largest amount of breeding and storage cells.
The royal cells are few and somewhat acorn-shaped.
The large drone-cells, and those for storing extra honey,
are linked up with the great mass of worker and storage
cells by a series of transition cells. Each cell is a
hexagonal tube, and it has been shown that by adopting
this form for their cells the bees have solved with
mathematical nicety the problem of how most closely
and strongly to fit cells together. But not only have
bees combined these advantages with the greatest
thrift in material, they have also bound the cells
together into a comb, and attached it to the hive-
walls in a way that combines symmetry and strength,
whilst yet permitting of traffic, incomings and out-
goings, and ventilation without mutual interference.

The diverse kinds of cells are evolved from one

204 ANIMAL LIFE

another so as to exclude waste of room, and the different
castes are not due to any variation in the shape of
the cell in which they are reared so much as to the
food with which they are supplied. Both workers
and queens receive at first a kind of jellied milk (pro-
duced either by the salivary glands or by the stomach
of the worker nurse, and possibly, when supplied to the
queen larve is not identical in constitution with that
given to the young workers) ; but whilst this diet is
continued for the queen, it is cut off from the young
worker after a few days, and for the rest of its larval
life the worker is given a coarser diet of honey, pollen,
and water. The drones usually arise from a some-
what different egg, but it is not certain whether in this
sex, too, the larval food may not have some influence,
since it is thought that drones receive more royal
jelly than do workers.

The Nests of Ants.—In the care of their young,
ants show more simplicity and flexibility of instinc-
tive nursing capacity than are exhibited by any other
animal. The nest is adapted to the nature of the
surroundings, and is sufficiently large to enable the
ants to adapt their charges to variations of climate.
The eggs, instead of being laid in cells, are deposited
loosely in the nest, and are carried, watched, and
cleaned by workers. When the colony is prosperous
a vast flight of males and females takes place from
a large tract of country, under heavy, thundery, hot
conditions. From the turf there spring fountains of
these winged creatures, and for miles on the same or

Fic. 62.—Worker-cells from Bee-comb.
(From a specimen in the Manchester Museum.)

296 ANIMAL LIFE

successive days this wonderful exodus or swarming
will proceed. In loose order this cloud will drift over
the countryside, harassed in the air by swallows and
other birds, and by larger ants on the ground. What
the fate of these swarms may be is imperfectly
ascertained. The males probably die immediately,
but those females that escape the ravages of foes and
of accidents are probably either annexed by some
wandering workers of the same species or set up
new colonies without aid. Some appear to do this
at once, and others not until the following spring.

After the swarming of the males and females from
each nest the workers are left with a small store of
pupe, and it is probable that from these the new queens
are developed, somewhat as in hives after the departure
of a swarm with the old queen. But among ants, as
several queens are allowed to reign simultaneously,
there is no combat between the first new queen and
her rivals. Moreover, in some cases a queen will
remain for many years in the same nest, active to the
last. The best established instance of this longevity
was that of a queen kept by Lord Avebury, which
lived to be fifteen years old. That is as long as a
dog, and three times as-long as the oldest known bee
queen.

The long life of the queen would not, however, prove
that the colony persisted. The workers of a beehive
rarely survive more than one summer,: but the colony
survives the winter by replacement of moribund by
new workers, by the elaborate and largely artificial

THE NESTS OF ANTS 207

precautions adopted by bee-keepers for retaining
sufficient heat. All other communities of bees and
wasps are in temperate climates destroyed each winter
and built up anew each spring and summer. Of our
native insects only the ant is able to survive the
winter, both as an isolated queen and as a colony
of queens and workers. This power of survival is
rendered possible by the longevity of the workers,
which, in some cases, extends for five years; but it
is determined far more by the precautions taken by
ants to evade the deadly influences of autumn and
winter. They retire to the deepest layers of their
nest, sometimes to a depth of nine feet, and so escape
the effect of frost. Ultimately, however, the persist-
ence of the colony can only be explained by attributing
to ants a power of resistance to adverse circumstances
which other insects, with few exceptions, do not
possess. However that toughness may be explained,
its influence on the dominance of ant-life has pro-
bably been decisive, for the resurrection and resump-
tion of work by the old colonies, supplemented by the
growth of new ones from the isolated autumnal queens,
enables the work of the previous year to be continued
and extended. The longevity of workers gives them an
opportunity of improving by practice those instinc-
tive traits which they first exhibit when young ;
and since the workers for good or ill control the growth
of the colony, most of its distinctive features must be
attributed to them.

Amongst the various offices they perform the

298 ANIMAL LIFE

most important is the care of the young. In a new
colony begun by a solitary queen no workers are
present. This queen forms a small burrow, lays some
eggs, and when these hatch she feeds, cleans, and
tends the larve and pupe. These emerge as workers
of different sizes, and they at once relieve the queen of
most duties. They extend the colony, make roads,
hew wood, draw water, and, above all, tend the young,
not only cleansing them of every speck and germ,
taking them upstairs for warmth and downstairs for
safety, but supplying with their own lips and con-
veying to those of the larve all the nourishment
that the young require. The quality of this nourish-
ment is probably the decisive factor in the sex and
character of the offspring. By increasing the amount
of fatty saliva, comparable to the royal jelly of bee-
workers, which the nurse suppiies, she can produce
a queen instead of a worker, and probably some slighter
difference in the quality or quantity of the food she
affords, decides the size and character of the worker.
Possibly the nurse determines certain features of the
short-lived male brood, for as in bee-drones so among
ants it is probable that the males arise from eggs
different in composition from those which produce
workers, soldiers, or queens. ‘ This passion for nursing
has led to very curious results, for the workers in
many colonies are, as it were, not satisfied to rear only
their own kind, but extend their brooding care to
the young of other insects, even to the detriment of
their proper charges. The influence of this fostering

NURSING HABITS OF ANTS 299

habit has been discovered quite recently, but since
it throws an unexpected light on the origin of the
intermediate castes that link worker and queen or
fertile and infertile workers together, and further
suggests how the relative numbers of these annectant
forms may be explained, we may refer shortly to this
aberrant habit.

In most colonies of an ant (Formica sanguinea),
somewhat rare in this country, the extraordinary
spectacle may be seen of one or more foreign ant
species acting as slave-nurses more efficiently than
the indigenous workers with whom they either share
the household work or assume the nursing entirely.
Besides these slave-tenanted colonies there are some
in which a little cock-tail beetle has taken up its
abode. This visitant is not accidentally present,
but is deliberately reared by sanguinea-ants, appar-
ently for the sake of an ethereal drink which distils
from little yellow tufts placed on different points of
its body. This dram is solicited by the workers
applying their antenne to the cock-tail’s body,
stroking it, and lapping the liqueur with their tongue.
The beetle-larve are, however, not content to be
merely fed by the ant-workers, but ravage the colony,
eating up eggs and young, so that not only does the
state become impoverished and the nurses dissipated,
but the young ants receive insufficient nourishment
to convert them either into.workers or queens, and
become stunted and unable to build, nurse, defend,
or extend the colony. Fortunately, however, the

300 ANIMAL LIFE

ants foster the beetle-larve also, and, as they nurse
these adopted children as their own, they inflict upon
them a treatment which is utterly unsuited to their
needs, though appropriate to those of ant-larve.
During the early larval stage all goes well; the young
beetles, fed by the ants and feeding on the ant-eggs
and young, grow rapidly, but when they are about
to reach the pupal stage the ants bury them, then
unearth them, carry them to the surface and again
bury them. This treatment, suitable for ant-pupe,
is the death of the beetle-larve, and the mortality
is more than 98 per cent. This result is the
salvation of the colony, which would be decimated
were the beetle to increase at the rate their foster-
nurses strive to attain. For it is just those nests
most infested by the beetle which produce most
stunted ants, and the perverted nursing instinct of
Formica sanguinea works out the salvation of its
race (Wasmann).

REFERENCES

Sharp, D. ‘Insects.’ Cambridge Natural History.
Macmillan.

Folsom. ‘ Economic Entomology.’ Rebman, Limited.

Miall, L. C. ‘ Aquatic Insects.’ Macmillan.

Peckham. ‘ Wasps, Solitary and Social.’ Constable.

Latter, O. H. (Social Wasps.) ‘ The Natural History of
some Common Animals.’ Cambridge Biological Series.

Fabre. ‘Souvenirs Entomologiques.’ (In part translated
as ‘ Insect-Life.’ Macmillan.)

Wasmann, E. ‘Psychology of Ants.’ Sands & Co. 1905.

INDEX

(References in heavy type refer to illustrations)

ABUNDANCE OF LIFE, 7-15
Adaptations of birds, 57-04
of fish, 43-8
of mammals, 48-57
ZEsop (prawn), 169-77
Agelena, web of, 95, 96
Air bladder, 118-9
Air tubes, 250
Ammophila (sand-wasp), 271-4
Andrena (solitary bee), 284,
285
Anemones, food of, 79
pigments of, 106
respiration of, 105
Angutis (slow-worm), 18
Animalcules (Protozoa), 19, 33,
66, 105
Animals, fixed, 66
food of, 65-98
life histories of, 217—300
movement of, 26
respiration of, 99-126
senses of, 127
Ants, nests of, 294-300
nursing habits of, 299
swarming of, 294-6, 197-8
workers, 297-8
Aphides (green-fly), 12
Arachnids, food of, 92-7
Arctic bees, 291
Arctic colouring, 179-80
Arion (slug), 4
Avebury, Lord, 71, 98, 296

>

BARNACLES, food of, 66, 78
Bats, 41, 53, 56-7
Bee, burrowing, 282-284
evolution of, 284-94
hive (honey), 293-4
leaf-cutter, 278
solitary, 277-85
Beetles, 238
burying, 76
tiger, 89
Birds, flight of, 57-61
food of, 76-7, 85-6
Blood, 108, 110
pigments, 156-9
relationship, 17
Blood-sucking flies, 248-52, 257-
60, 262-3
Bombus (bumble-bee), 286-91
Branchipus (brine-shrimp), 109
Breathing. (See ‘ Respiration ’)
Butterflies, cabbage-white, 243
emperor, 90
leaf, 185
orange-tip, 179

CADDIS-FLIES, 235-8

worms, 236
Campodea (primitive insect), 22:
Carnivores, origin of, 78, 88
Caterpillars, 241-5

’ Centipedes, 39

Changefulness, 99
Chironomus (harlequin fly), 252

302 ANIMAL LIFE

Chromatophores (pigment cells),
161, 163, 172
Chrysaora (jelly-fish), 13
Climate, influence of, 217, 291
Cockles, 113-114
Coelenterates, 19
Colouration, mating, 193-5
mimetic, 188-9
sympathetic, 168-89
Colours of animals, 149-89
relation to excretion, 166-7
relation to light, 149-89.
(See also ‘ Pigment’)
relation to nutrition, 154-71
relation to respiration, 155-9
Colours of plants, 149, 154, 155,
161
Corals, 106-7
Corophium, 69
Crabs, breathing of, 112-3
masked, 114 |
movements of, 38
pea, 81
Crayfish, gills of, 111-112
Crustacea, 19, 81, 109, 110, 111,
112, 114
food of, 67—70
movements of, 38
Cuckoo, young, 215
Cuckoo-bees, 283
Cuttle-fish, 84
food of, 85
movements of, 32-3

DARWIN, on colour, 186
on earthworms, 6
on mating selection, 216
Death, 291-7
Disease, due to animals, 93,
246-52
Domestication of animals, 147-8
Dormouse, 124, 125
Dragon-fly, 33, 89-90
life history of, 228, 229-231
Drones, 197, 292

Economy (efficiency of organ-
isms), 102

Eels, 28

Eggs, cuttle-fish, 204
dog-fish, 11

Eggs, frog, 204
gnat, 204
goby, 204
herring, 203
perch, 204
sea-worm, 202
skate, wage OA
skylark, 2
tern, 209
Elaters (beetles), 239
Energy, 102
Evolution, 21-23, 77

FEATHERS, 3, 61
Finsen, light treatment of, 4
Fish, flat, 46
food of, 82-4
gills of, 116
goby, 47
John Dory, 84
movements of, 30, 43
mud, 117
Flagellates, 157-8
Flies, black, 257
food of, 90
harlequin, 252
house, 247
May, 231
saw, 266
stone, 232
Flight, of birds, 27-9, 57-61
of insects, 31, 40-42
Folsom, 300
Food, of birds, 76-7
of Crustacea, 67-8
of cuttle-fish, 85
of fish, 82-3
of fixed animals, 66
of insects, 89-92
of mammals, 76, 89
of shrimps, 139
of snails, 73
Frogs, care of young, 206
spawn, 204

Gammarus (sand-hopper), 68

Gills, of Crustacea, 108-10
of fish, 116-7
of insect larve, 232, 250
of worms, 108

Gnat, life-history, 248-52

- cer: —

INDEX

Grasshopper, life-history of,
224-28

Grebe, foot of, 64

Gulls, black-headed, 86

nests of, 210

Hasits, choice, becoming, 129
periodic, 129
Haddon, A. C., 6
Hemoglobin, 110
Halictus (burrowing bee), 285
Headley, F. W., 64
Heart, control of, 37
Hibernation, 125
Hippolyte, colouration of, 169-77
Horse, movements of, 49
House-fly, 247
tongue of, 91
rate of growth, 222
Humming birds, 77, 207
Hydroids (zoophytes), 79

IcHNEUMON (fly), life history,
266
Intelligence, 17, 276

JELLY-FISH, 13
food of, 82
movements, 32

Jenks, E., 248

Kallima (leaf-butterfly), coloura-
tion of, 185

LANKESTER, SIR RAy, 25
Latter, O. H., 300
Legs, of bees, 281

of land vertebrates, 48-53
Lepisma (primitive insect), 223
Life-histories, of black-fly, 257-

60

of beetles, 238-240

of butterflies, 240-6

of caddis-flies, 235-8

of corethra, 255-7

of dragon-flies, 228-31

of gall-flies, 267-8

of gnat, 248-250

of harlequin fly, 252-5

of hymenoptera, 263—300

of May-flies, 231-4

393

Life-histories, of owl-midges, 257
of saw-fly, 266

Life, as a response, 127-48
changefulness of, 65, 99
problems of, 24

Limax (slug), 74

Lizards, sand or brown, 18
habits of, 51

Lugworm, 114

McCook, H., 98
Machilis (primitive insect), 33
Maine, Sir Henry, 248
Man, power of adjustment,
147-8
Marey, P., 64
Mates, love of, 190
Mating, colours, 193
combats, 193-6
selection, 193-7
May-flies (frontispiece)
Melipona (bee), 292
Meloe (oil-beetle), life history,
239-40
Memory, organic, 128-31
Metamorphosis, 234
Miall, L. C., 235, 300
Midges, life-history, 257
Migration, of birds, 28-9, 57,
200-1
of fish, 28, 200
Mimicry, 188-9
Mole, 78
Morgan, Lloyd, 248
Mosquito, 248, 252
Moths, gooseberry, 188
hawk, 42, 90
mating of, 198
Movement, ciliary, 33-7
of birds, 27
of Crustacea, 38
of fish, 43-7
of lizards, 51
of quadrupeds, 48-9, 52-4
of seals, 53-4
of vertebrates, 43
of whales, 54-5
of worms, 37
spontaneity of, 37
Muscle, QI-IOI, 159
pigments of, 159

304 ANIMAL LIFE

Mussel, 81
cilia of, 35
messmates in, 81

NEREIs (sea-worm), 200
Nervous system, action of,
128-45
development of, 140-4
Nests, birds, 206-15
fishes, 205-6
mammals, 215
spiders, 96, 97
Newts, armoured, 22
figured, 20
Nuttall, G. H. F., 25

Orchesella (primitive insect), 71
Order, 16
Organic memory, 130-2
Organisation, 16-25
Orthoptera, 224-7 (order of |

insects containing cockroach,

grasshopper, mantis, etc.)
Oxygen, need for, 99

quest for, 102-4

(See also ‘ Respiration ’)

Oyster, enemies of, 82

PARTRIDGE, 181, 182
Peckham, on spiders, 216
on wasps, 300
Pheasant, argus, 194
Pigeon, wing and dissection of,
59 /

Pigments, blood, 110
excretory, 167
fatty, 160-165
muscle, 159
of sponges, 107-8
Pipe-fish, 177, 206
Plants, as food, 65-7
characteristics of, 1, 154
history of, 77
pigments of, 161
Poulton, on mimicry in butter-
flies, 188-9
Prawn, AEsop. (See ‘ Hippolyte’)
Prosopis (solitary bee), 278
Protozoa. (‘See Animalcules’)
breathing of, 105

Pupa (chrysalis), 235

Races, colouration of, 149

welfare of, 24, 190
Reeves, mating of, 195
Respiration, of bivalves, 113

of Crustacea, 108-13

of cuttle-fish, 115

of Protozoa, 105

of univalves, 115

of vertebrates, 116-23
Response, power of, 127—40
Rhizostoma (jelly-fish), 13
Rodents, 74, 227
Romanes, G. J., 98
Ruminants, 76

SCALE-INSECTS (coccide), 12,

219
Scolopendrella, 39
Sea-urchin, 33, 114, 115
Seal, 53, 54
Sense, organs of, 133
Sharp, on insects, 300
Shells, 110, 113, 114, 115
Shrimps, food of, 139
senses of, 136-9
Silver-fish (Lepisma), 223-4
Simulium (black-fly), life-
history of, 257-60
Skylark, nest of, 211
Sleep, 129
Sminthurus (a primitive insect),
223
Snakes, movements of, 50-1
Species, 16
Spiders, 92
mating of, 192-3
webs of, 93-8
Sponges, 105-6
Starfish, 33, 83
Swallows, 208
Sympathetic colouring, 168-89
in prawns, 168-9
in insects, 183-7

TASTE, 139
Teeth (ungulates), 75-6
Tern, little, 210

nest of, 209, 210
Thayer, on colouration, 181, 189
Thyroid (gland), 131, 132
Titmouse, nest of, 213

i ie

a ee eee

ee

INDEX

Tongue, of bees, 280
of fly, 91~
of insects, 70
of snails, 73
Turbinal bones (nasal chamber),
76, 123

UNGULATES, 52, 74
Uric acid, 167

VOICE, mammals, 125

WASMANN (on ants), 300
Wasps, nests, 977

Wasps, social, 275

solitary, 269
Water, air in, 102, 103

surface-film of, 249
Wave-movement, 201
Whales, 53-5

food of, 84-5
Winter sleep, 14
Wireworm, 239
Workers, 286-97
Worms, earth, 4

Palolo, 202

water, 200

ZOOPHYTES, 19, 146

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