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THE WANDERINGS '
OF ANIMALS

BY

HANS GADOW, F.R.S.

Lecturer in Advanced Morphology
in the University of Cambridge

Cambridge :
at the University Press

New York :
G. P. Putnam's Sons

•-V.1

Cambrtflge :

PRINTED BY JOHN CLAY, M.A.
AT THE UNIVERSITY PRESS

With the exception of the coat of arms at
the foot, the design on the title page is a
reproduction of one used by the earliest known
Cambridge printer \ John Siberch, 1521

PREFACE

THESE outlines of the distribution of animals
deal with a rather young branch of science.
An attempt has therefore been made to sketch its
rapid growth from small beginnings until it has become
boundless, because the interpretation of at first seem-
ingly simple facts in the domain of the zoologist,
had soon to enlist the help of well-nigh all the
other branches of Natural Science. The subject of
geographical distribution is the dispersal of life, the
greatest mystery of all, in space and time. The key
to the present lies in the past.

The historical and introductory chapter is followed
by a few sketches of the home, as most intensified
kinds of which have been selected tropical forests,
deserts and high mountains with their various effects
of climate and the interdependence of animal and
plant life. Next come some short chapters on the
modes, means and rates of spreading ; and as one of
its main causes is the natural increase in numbers,
a few tentative remarks on numbers of species and
individuals, on rich and scanty faunas and kindred
questions have been added. Last, not least, given
the creatures, their home requirements and their
need to wander, the majority of them could not have
attained their present distribution, and the various
countries could not have got their present mixed
faunas, unless the map of the world had undergone

vi PREFACE

many and vast changes. Some of these have there-
fore been indicated in a tentative way. Like other
previous hypothetical maps they will be objected to
by the timid, on principle ; critics with more expert
knowledge will amend them. Meanwhile, may the
reader not forget that he has embarked in a frail
craft upon a romantic voyage across unknown seas
in search of undiscovered lands.

Herewith ends the general part, the principles
of distribution. The special part deals with the
distribution of a considerable number of various
groups of animals, mostly terrestrial vertebrates,
selected for their fitness as test cases. Some seem
to tell their story well ; others, owing to remote age,
insufficient data, and want of fossils, have got their
record into a tangle. In a few sample cases, for
instance the marsupials, an attempt has been made
to unravel such a tangle, and to spin a coherent yarn.
Since this cannot be done without recourse to many
technical terms and names, it makes rather stiff read-
ing. Such technicalities are the bane of the general
reader be he never so interested in the subject, but
where homely words and names are wanting, he has
to put up with them. Further, he should know the
geological time-table as well as his geography.

H. dr.

February, 1913.

CONTENTS

CHAP. PAGE

Introduction

I. History of Geographical Distribution ... 3

II. Features of Environment . . . . . 18

Tropical Forests . . 18

Deserts 30

High Mountains and Vertical Distribution . 43

III. Spreading .... ... 61

IV. Numbers and Density of Species ... 69

V. Former Configurations of Land and Water . . 76
VI. Distribution of Selected Groups . . . . 87

Bibliography 143

Index 146

MAPS

1.

Toads ....

refers to p. 97

2.

Snakes ....

„

„

103

3.

Ratite Birds.

11

11

104

4.

Gallinaceous Birds

11

11

110

5.

Bears ....

11

11

128

6.

Elephants

11

11

129

7.

Primates

11

11

140

8.

Lower Trias .

at end

«f

book

9.

Upper Trias .

11

11

11

10.

Lower Jurassic . ;

11

11

11

11.

Lower Cretaceous

11

11

11

12.

Upper Cretaceous

11

11

11

13.

Upper Eocene

11

11

11

14.

Early Oligocene .

11

11

11

15.

Late Oligocene

11

11

11

16.

Late Miocene . i

11

11

11

17.

Early Pleistocene.

11

11

11

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p. 44 4th line bottom

Instead o/ highest mountain read height of mountain

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Zealand and in Australia

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buttalo, none of which occur south of Mexico. He
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and deer live in close proximity to each other. It is
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geologically not so very long ago, there lived in
England, elephants, rhinoceros, hippopotamus, hyaenas,
crocodiles and pelicans, all of which have since with-
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INTRODUCTION

EVERYBODY knows that if he wants to shoot a
lion, he must go to Africa, and to India for a tiger.
The sportsman bent upon making a collection of
antlers, will find some kind of deer or other from
Spain through the whole length and width of Europe
and Asia, he may cross Behring Strait and again he
will meet stags from Alaska through the whole length
of the Americas down to Patagonia. Well may he
conclude that deer are cosmopolitan and yet he
would be mistaken, since with the exception of the
Fallow deer in Algeria there is not a single kind in
the whole of Africa. There on the other hand lives
an abundance of hollow-horned game, antelopes and
buffalo, none of which occur south of Mexico. He
may well ponder over these facts, especially as in the
Northern Hemisphere wild cattle, sheep, antelopes
and deer live in close proximity to each other. It is
common knowledge that before the Glacial epoch,
geologically not so very long ago, there lived in
England, elephants, rhinoceros, hippopotamus, hyaenas,
crocodiles and pelicans, all of which have since with-
drawn further south. To understand this does not

1

2 THE WANDERINGS OF ANIMALS

require a great stretch of imagination. It is another
thing to be told that such an essentially Asiatic beast
as the camel had its origin in North America, where
now there are none, whilst, to balance the account,
the American bison is a rather recent immigrant from
the Old World, where he lingers now in the Caucasus
only. We may well feel bewildered *by such ex-
changes, and are forced to give up the cherished
notion that the original home of a creature is that
country where it is now most abundant. If this
were always the case, zoological geography would
be an easy matter. To trace the animals back to
their original home, to follow their wanderings, suc-
cesses and failures, the changes which they have
undergone by adaptation to new and altered environ-
ment, and to account for the composition of faunas
of the various countries and seas, is the fascinating
study of animal distribution.

This study has itself passed through various
stages. The legend of Noah's flood contains a con-
siderable amount of shrewd sense. It is the first
treatise on geographical distribution. Given the
animals — and in spite of all the advances of modern
science we have to abide by the same premises — the
limited fauna of that part of the world started afresh
on Mount Ararat, the only remaining land, or, as we
put it now in scientific terms, the only continental
remnant which was not atfected by a world-wide

CH. i] HISTORICAL 3

transgression of the sea. Thence the creatures dis-
persed, multiplying, migrating and accommodating
themselves, each according to its kind, in a country
which possessed the greatest variety of physical
features, where snowr-clad mountains arise from a
semi-tropical lowland. That at least some of these
wanderings wrought change in the emigrants is clearly
expressed by the statement that Noah's children,
presumably all Semites, became the founders of the
white and black races of mankind. The environ-
mental conditions in Africa made Ham's descendants
melanistic. It was a crude way of accounting for
things, and yet, if we honestly condense all our up-
to-date knowledge into one sentence, the result
would not be very much superior. At best our
treatise is a Romance of Land and Water.

CHAPTER I

HISTORY OF GEOGRAPHICAL DISTRIBUTION

THE first general ideas about geographical dis-
tribution may be found in some of the numerous
speculations contained in Buffon's Histoire naturelle,
the brilliant style of which greatly enhanced the
interest taken in natural history. The first special
treatise on the subject was, however, written in 1777

1—2

4 THE WANDERINGS OF ANIMALS [OH.

by E. A. W. Zimmermann of Brunswick, whose large
volume Specimen Zoologiae Geographicae Quadru-
pedum deals in a statistical way with the mammals.
In the following year appeared the Philosophia
Entomologica by J. C. Fabricius of Kiel, who was
the first to divide the world into eight regions. In
1803 G. R. Treviranus of Gottingen devoted a long
chapter of his great Biologic to a philosophical and
coherent treatment of the distribution of the whole
animal kingdom. Remarkable progress was made
by F. Tiedemann of Heidelberg, whose Anatomic
und Naturgeschichte der Vocgel, 1810, deals with
some of the most subtle and fundamental causes of
distribution, for instance the influence of environ-
ment, distribution and migration upon the structure
of birds. None of the many subsequent writers seem
to have known of the ingenious way in which
Tiedemann marshalled his statistics in order to arrive
at general conclusions. The entomologist Latreille
of Paris proposed the view that temperature was
the main factor in distribution. This was combated
in 1822 by Desmoulins of Bordeaux, who in a most
suggestive paper introduced the idea of 'analogous
centres of creation,' meaning that similar groups of
creatures may have arisen independently in different
parts of the world. The first book dealing with the
'geography and classification' of the whole animal
kingdom, was written by W. Swainson in 1835, but

i] HISTORICAL 5

it suffered from the mysticism of the author's ' quinary
system.' Ch. Ly ell's Principles of Geology should
have marked a new epoch, since in his Elements he
treats of the past history of the globe and the dis-
tribution of animals in time, and in his Principles
of their distribution in space in connexion with the
actual changes undergone by the surface of the
world. But as he restricted himself to the com-
paratively minor modern changes, and believed in
the permanency of the great oceans, he did after all
advance our problems but little. Meanwhile E. Forbes
of Edinburgh devoted himself to the marine fauna,
especially the Mollusca. He established nine ' homo-
zoic zones/ subdivided into 25 'provinces' based
chiefly on the isotherms or belts of equal temperature.
J. D. Dana of JS^ew Haven taking mainly the Crus-
tacea as a basis, and as leading factors the mean
temperatures of the coldest and of the warmest
months, arrived at five latitudinal zones, with many
provinces. In 1853 L. K. Schmarda of Vienna pub-
lished his two volumes comprising the distribution
of the whole animal kingdom. After devoting many
chapters to the possible physical causes and modes
of dispersal from original centres of creation, he
divided the land into 25 'realms,' some of which
were well selected, but they were obviously too
numerous for general purposes. This drawback was
overcome in 1857 by P. L. Sclater with the now

6 THE WANDERINGS OF ANIMALS [CH.

classical six ' regions,' which he named Palaearctic,
Ethiopian, Indian, Australian, Nearctic and Neo-
tropical. Those of the Old World were brigaded
as Palaeogaea and the two Americas as Neogaea,
a fundamental mistake. Broadly speaking these six
regions are equivalent to the great masses of land ;
they are convenient terms for geographical facts,
especially since palaearctic expresses the unity of
Europe with the bulk of non-tropical Asia. Un-
fortunately these regions are not of equal value.
Therefore, instead of keeping up the popular dis-
tinction between the Old and the New World,
Huxley in 1868 gave reasons (cf. Gallinaceous birds)
for dividing the world transversely, into an Arcto-
gaea or North World in a wider sense, comprising
N. America, Asia, with Europe and Africa ; and
Notogaea or South World, which he divided into
New Zealand, Australasia and Austro-Columbia,
the latter an unfortunate substitute for Neotropical.
Although applicable to various groups of animals,
the combination of S. America with Australia in
opposition to the rest of the world was gradually
found to be too sweeping a measure. The satis-
factory solution was provided by W. T. Blanford,
who in 1890 recognised three main divisions, namely
Australian, South American and the rest, for which
the already existing terms Notogaea, Neogea and
Arctogaea have come into general use.

i] HISTORICAL 7

Meanwhile in 1859 Darwin's Origin of Species
had given a great impetus to the study of geographi-
cal distribution and caused a parting of the ways in
its treatment, especially in the mapping of the world
into regions or other divisions. Whilst some writers
were, and are, satisfied to express by their realms,
regions, or zones the recent, actually existing, sta-
tistic similarities and differences of the faunas of the
various countries, other workers, more appreciative
of evolution, tried to apply genetic principles to the
selection of their divisions, which they rightly con-
sidered as original centres of creation and subsequent
dispersal.

Haeckel, the foremost apostle of ' Darwinism ' in
Germany, has given us in his Generelle Morphologie,
1866, the terms Oecology, the relation of organisms
to their environment, and Chorology, their distri-
bution in space. The 14th chapter of his History
of Creation, 1868, is devoted to the distribution of
organisms, with the emphatic assertion that ' not
until Darwin can chorology be spoken of as a
separate science, since he supplied the acting causes
for the elucidation of the hitherto accumulated mass
of facts.'

One of the earliest writers to grasp the new
situation was Pucheran1 in France. He pleaded that

1 Pucheran had already, in 1865, insisted upon the essential unity
of the faunas of Europe, Asia and Africa, and on the necessity of

8 THE WANDERINGS OF ANIMALS [CH.

the Sahara, formerly a marine basin, was peopled by
immigrants from the neighbouring countries, and
these became new animals by adapting themselves
to the new environment ; the agreement in coloration
between the desert and its fauna is 'une harmonic
post-etablieV They did not survive because they
happened to be of desert-colour, but assumed that
colour because they found themselves in a desert.
He also discussed, besides similar questions, the
Isthmus of Panama with regard to its having once
been a strait. A strong proof of the new influence
upon this French scientist is the following sentence :
1 As the various parts of the world successively were
formed and became habitable their respective con-
temporaneous faunas spread by radiation, each from
its centre, and became modified according to the
local physical conditions.'

In 1866 appeared Andrew Murray's Geographical
Distribution of Mammals, an important work, illus-
trated with 101 coloured maps, the first of its kind1.
Like Forbes he did not shrink from assuming

separating S. America as well as Australia from the rest of the world.
Of far reaching influence was also the excellent Zoo-geographical
sketch Ueber die Herkunft unserer Thierwelt by the Swiss Palaeonto-
logist L. Riitimeyer, published at Basel in 1867.

1 The earliest maps dealing with our subject seem to be those in
H. Berghaus' Physikalischer Atlas: Thiergeograpkie, Gotha, 1852.
In the third edition, 1887, this has been enlarged into an Atlas der
Tierverbreitung , by W. Marshall.

I] HISTORICAL 9

enormous changes in the configuration of the con-
tinents and oceans because the theory of descent, with
its necessary postulate of great migrations, required
them.

In the same year Moritz Wagner showed that
migration implies not only new environmental con-
ditions but also secures separation from the original
stock and thus eliminates or lessens the reactionary
dangers of panmixia or promiscuous interbreeding.
This idea had been discovered before and it has been
rediscovered several times after Wagner. Through
the heated discussions of the more ardent selection-
ists, Wagner's theory came to grow into an alternative
instead of a great help to the theory of selectional
evolution. Separation is now rightly considered a
most important factor in the making of new species.
C. Semper could well say in his suggestive work
Existenz-Bedingungeti der Thiere, also published in
the fertile year 1868, that ' our whole Zoogeography
is indeed nothing but a big heap of bricks, piled up
without sense,' and he was one of the first to eluci-
date the distribution of a group — Holothuria or Sea
Cucumbers — by tracing the relationship of its genera
and species, whilst distinguishing between their
centres of origin and their subsequent migrations,
and not losing sight of former geological conditions.

In 1872 Alexander Agassiz of Harvard followed
with a morphological systematic revision of the Sea

10 THE WANDERINGS OF ANIMALS [CH.

Urchins, which led him to establish four realms of
the oceans, justified also by climatic and other physical
conditions.

In an anniversary address to the Geological
Society, 1870, Huxley pleaded for various former
land connexions and considerable marine changes.

Whilst English, American, German and French
scientists were thus hard at work at reconstructing
the history of the world — it having become thoroughly
understood that the key to the present distribution of
any group of animals or plants lies in the past— the
year 1876 marks a new period with the appearance
of A. R. Wallace's great work. These volumes, sup-
plemented by the fascinating Island Life, have
indeed popularised the study of geographical dis-
tribution, and there is now an ever widening circle
of enthusiasts far beyond the professional brother-
hood. His works have become the classics of our
science and they will remain so, but they have also
had some influence not altogether advantageous.

He accepted Sclater's six regions with slight modi-
fications and divided each into four subregions, but
did not follow Huxley's courageous changes and
logical subordinations. Holding the view of the per-
manence of the oceans and therefore comparatively
small changes of land, he accounts for the coloni-
sation of outlying islands (especially his ' oceanic
islands') by further elaborating the views of Lyell

ij HISTORICAL 11

and Darwin. The subsequent literature is full of
devices for the mechanical dispersal of animals, as
marine currents, floating logs and icebergs, storms
and waterspouts.

Wallace's method of arriving at the degree of
relationship of the faunas of the various regions
is eminently statistical. Long lists of genera deter-
mine by their numbers the affinity and hence the
source of colonisation. This statistical method has
found many followers, who, relying more upon quantity
than quality, have obscured the problem.

An extensive literature has since grown up, almost
bewildering in its range, diversity of aims, and style
of procedure. So prominent, as to almost constitute
a characteristic period, has become the search by
specialists for either the justification or the amend-
ing of the Sclater- Wallace regions. As class after
class of animals was brought up to reveal the secret
of the true regions, some authors saw in their
different results nothing but the faultiness of the
regions established by their predecessors ; others
looked upon eventual agreements as their final cor-
roboration, especially when such diverse groups as,
e.g. mammals and scorpions, could, with some in-
genuity, be made to harmonise. But the undeniable
result of all these efforts was the growing knowledge
that almost every class, nay many an order or even
family, seemed to follow principles of its own. The

12 THE WANDERINGS OF ANIMALS [OH.

resulting regions tallied neither in extent nor in
numbers, although most of them gravitated more and
more towards three centres, namely Australia, South
America and the rest of the world.

Let us take up the account with the establishment
of the Noto- Neo- and Arctogaea in the year 1890, when
Trouessart of Paris, by adding an arctic and an ant-
arctic region to those of Wallace, increased them to
eight, but he also suggested that these might be recom-
bined into three 'zones,' namely an Arctic (=Heilprin's
and Newton's Holarctic), an Antarctic (South America
and Australia) and an Old- World tropical zone. The
latter idea was taken up in 1892 by Allen of New
York who, after a study of the Mammalia, joined the
Old Oriental and Ethiopian regions into one Indo-
African. Meanwhile A. Heilprin of Philadelphia in
1887 accepted the Neotropical, Australian, Oriental
and Ethiopian regions, but at the suggestion of
A. Newton combined the Nearctic and Palaearctic
as Holarctic ; further, he carved out two new
regions, one Mediterranean, the other Sonoran ; for
the Nearctic, now reduced to Canada and Alaska,
together with the Palaearctic Blanford suggested the
name Aquilonian, whilst for the Sonoran he revived
Cope's term Medi-Columbian. We have only to add
that some Zoo-geographers treat as principal regions
what others consider as subregions, that some speak
of eight realms and others of only three regions, and

i] HISTORICAL 13

still another of as many as nine ' Gaeans ' as chief
units, and others prefer six zones, to indicate that
chaos reigns instead of order.

Although with this wild search for the true regions
the value of the fossil animals became fully recognised
as the only absolute evidence of distribution in the
past, it was frequently ignored that the various groups
of animals have appeared in successive geological
epochs and also at many places remote from each
other. The key to the distribution of any group lies
in the geographical configuration of that epoch in
which it made its first appearance ! If, for argu-
ment's sake, some group of land animals had come
into existence in Africa, when this was still con-
tinuous with Madagascar, the present descendants
of these animals may well be found in both countries,
but this could not be the case with another group
which was evolved after Madagascar had become an
island. This is so obvious as to sound like a platitude.

If all the various groups of creatures had come
into existence at the same epoch and at the same
place, then it would be possible, given sufficient data
as to present and past distribution, to construct a
map showing the generalised results applicable to
the whole animal kingdom. But the premises are
wrong. Whatever regions or primary centres we may
seek to establish as applicable to all classes, we are
necessarily mixing up several principles, namely time

14 THE WANDERINGS OF ANIMALS [OH.

and space, occasionally the past of North and South
with the present East and West.

In short, there are no generally applicable zoo-
logical regions, not even for each class taken separately,
unless the life of this class is confined to a compara-
tively short geological period. Most of the greater
groups have far too long a history and have evolved
many successive divisions. Let us take the mammals.
Marsupials or pouched mammals still live in Australia
and in both Americas because they existed already
in Mesozoic times. But hoofed beasts, Ungulata, ex-
isted at one time or other all over the world, except
in Australia, because they, as a group, are post-
Cretaceous. Deer and bears, as examples of still
more recent northerners in origin, are found on every
continent except Australia and Africa. Each of these
groups teaches a valuable historical lesson, but when
these and others are combined into a few mammalian
realms or regions they mean nothing but statistical
majorities. If there is one at all, Australia is such
a realm backed against the rest of the world, but as
certainly it does not represent an original mammalian
creative centre. So far as mammals are concerned,
New Zealand has none indigenous ; it is a Mesozoic
derelict, and is a ' region ' with a negative character.
Australia became a separate complex after it had
received, not evolved, the stock of its most character-
istic fauna which has since flourished so as to produce

i] HISTORICAL 15

many peculiar forms. Madagascar, also considered
as a region by some authorities, became an island
about mid-Tertiary times. Therefore, concerning
mammals, the world would not have been affected in
the least if neither Madagascar nor Australia had
ever existed. How different is the case of Africa. This
ancient and radiating centre has had an enormous
effect upon the fauna ,of well-nigh the rest of the
world.

There may be regions of birds, others of fishes
and others of beasts, but the search for generally
applicable regions is a mare's nest.

What, then, is the object of the study of Geo-
graphical Distribution? It is nothing less than the
history of life in space and time. The attempt
to account for the present range of any group of
animals (the special scope of Zoo-geography) involves
the aid of every branch of science. Our subject
began in a mild statistical way, restricting itself to
the present faunas and floras, and to the present con-
figuration of land and water. Next came Oceano-
graphy concerned with the depths of the seas, their
currents and temperatures ; then inquiries into
climatic changes, culminating in irreconcilable astro-
nomical hypotheses as to glacial epochs, the causes
of which are still a mystery ; theories about changes
of the level of the seas, from the point of view of the
geologist, the physicist and the astronomer. Then

16 THE WANDERINGS OF ANIMALS [OH.

came to the front the importance of the geological
record, hand in hand with the fossil data and the
search for the natural affinities, the pedigrees of the
organisms. The biologists not only set the problems ;
they alone can check the solutions offered by physicists
and geologists, and rightly so, because they concern
living matter, and life has been continuous ever since
the unfathomable dawn. The mere fact that sub-
tropical plants occur in the Miocene of Spitzbergen,
led to an hypothetical shifting of the axis of the world
rather than to the assumption, by way of explanation,
that the plants themselves might have changed their
nature. As the men of the Dordogne in the south
of France hunted the reindeer, we want explanations
why it was so cold. And since there are plenty of
bones of hippopotamus in the Cambridge gravel,
washed into it out of Pliocene crag, we require an
answer as to why East Anglia enjoyed a mean annual
temperature perhaps 20 degrees higher than now.

One of the most valuable aids, often the only
means for reconstructing the face of the earth in
by-gone periods, is afforded by fossils, but only the
morphologist can pronounce as to their trustworthi-
ness as witnesses, because of the danger of mistaking
analogous for homologous forms. This difficulty ap-
plies equally to living groups and is of the utmost
importance.

The affinity question can be settled only by

i] HISTORICAL 17

the morphologist, whose special business is the study
of the anatomical structure and the weighing of
these characters as to their classifying or taxonomic
value. To see through the resemblances, to see
what is due to blood-relationship or descent and what
is due to adaptation to similar mode of life is the
whole art of the builder of classifying systems, but
many of these pedigree problems are still unsolved.

The study of geographical distribution is now
proceeding in two main directions. I. Chorological.
According to the method employed this is either
zoological geography, proceeding by essays on the
faunas of selected countries, and thence, so to speak,
letting the research radiate in ever widening circles.
An example of this method is Scharff's European
Animals. Or geographical zoology, which takes se-
lected groups of animals and traces their changes of
range in time and space, e.g. Ortmann's Geographical
Distribution of Freshwater Decapods. Both methods
are of great interest, and each has its advantages in
working at the reconstruction of the geography of
former epochs. In short they are both essentially
chorological, a term which, although strictly meaning
distribution in space, must be understood to include
the factor of time. II. Oecological, the study of
animals with regard to their environment. Instead
of searching for pedigrees, or of showing how and
when the animals got to the various countries, it

G. 2

18 THE WANDERINGS OF ANIMALS [OH.

investigates the prevailing local physical conditions
and how these have influenced the faunas. The
cultivation of this field promises fair to throw much
light upon Nature's way of making species, and it is
all the more enchanting because here the animals,
whether recent or extinct, are brought before us as
living fellow creatures. The main purpose of an
organism is to live. If i purpose ' be objected to, let
us say it is its business, that with which it is busy.

But the broadest of land connexions is of no avail
to the dwellers of forests if it is a desert, or even a
prairie. What is attractive to some is repellant to
others. It is the environment, the condition of the
home, the oikos, which decides the tenants, hence the
importance of oecology.

CHAPTER II

FEATURES OF ENVIRONMENT

Tropical Forests.

NECESSARY conditions for the production of a
typical tropical forest are moisture and heat. The
mean temperature is that of the tropics, say 80° F.
rarely sinking below 70° or exceeding 90°. The
moisture must be due to rain with an annual
minimum of at least 60 inches, a fair average being

n] FEATURES OF ENVIRONMENT 19

80 inches for a 'rain-forest/ the more the better.
This rain must be distributed rather evenly, that
is, seasons of drought must not be too prolonged.
The dry period, if there is one at all, must not
amount to more than three months, lest there be a
standstill of the vegetation, causing deciduous leaves
and other great changes in the general aspect.

An annual rainfall of 80 inches is, in itself, not
terrific. For comparison it may be stated that we call
a climate with half this amount decidedly wet. The
North-West of Scotland and the wettest parts of
Ireland enjoy about 60 inches, but in the tropics
the rain makes itself more impressive by frequent
thunderstorms and by falling within a few hours of the
day. A fall of half an inch if spread over the twenty -
four hours, makes with us a very wet day. A fall
of an inch during a few hours' storm is of common
occurrence in the tropics, and the mere mechanical
effect of such a mass of falling water upon animals
and plants is considerable. The electric discharges
which accompany these torrential storms produce a
great amount of nitric acid which is washed out of
the air into the humus, and this process contributes
much to the wonderful exuberance of the vegetation
in every tropical rainy district.

There are three large regions in the world, which
fulfil these conditions.

First : Tropical America, with the huge basin of

2-— 2

20 THE WANDERINGS OF ANIMALS [CH.

the Amazon as its centre. It extends through Central
America into Mexico, mainly on the Atlantic side,
the backbone of the country causing a very striking
division.

Second : Equatorial West and Central Africa,
mainly the Congo basin.

Third : Indo-China with the Malay and Papuan
Islands.

Smaller centres within various other parts of
the world, for instance on the Zambesi, the east
coast of Madagascar, the Seychelle Islands, the south-
west coasts of S. India and Ceylon, the north coast
of Queensland and parts of Papuasia ; several West
Indian islands.

What is the general impression of a rain-forest ?
It does not begin gradually. On its outskirts it
forms an impenetrable wall of luxuriant herbage,
shrubs and creepers. It can be entered only by
slashing a path through the tangle, which closes up
again within a few weeks, except where traffic or
game has produced a meandering track, without a
chance of our deviating either to right or left. Once
inside, we are in a gloomy, stuffy forest of tall
straight trees which branch out high above us, then
interlacing and forming a dense canopy of green,
through which passes but little sunlight. This absence
of direct light prevents the growth of underwood,
and there are no green luxuriant plants, no flowers

u] FEATURES OF ENVIRONMENT 21

and no grass. The ground is dark, covered with
many inches of rotting leaves and twigs, all turning
into a steaming mould. From our standpoint below
the canopy, the leaves, branches and even bright-
coloured birds, look black, and this is still more the
case where, by contrast, these objects are seen through
a rift against the glaring sky. Many of the tree-stems
are entwined by the twisted rope-like stems of lianas,
long strands looking like rusty and frayed out wire-
cables, ugly in shape, without branch or leaf, until
they reach the crowns of the trees, where they inter-
mingle with the other verdure and creep across the
tree-tops, perhaps for hundreds of feet. Many a liana
has strangled its support, which has rotted away,
and the creeper, now anchored in the ground, ascends
straight through mid-air and there vanishes. Many
of them are vines ; where these are not indigenous
one or other of the numerous Bignonias or plants of
some other family undergo the same modification.

Wherever there is a break, where a tree has
crashed down, the other trees are covered with masses
of climbing arums. Philodendrons send down their
wire-like air-roots until these are anchored in the
ground ; the blooms, large scrolls of white, yellow, or
red, are visible from afar ; the supporting stem is
covered with a network of the climbers, which acting
as receptacles for the collection of mould, become
hotbeds for Selaginellas, ferns, lichens and a host of

22 THE WANDERINGS OF ANIMALS [OH.

gorgeous orchids, bromelias and other epiphytes, the
seeds or spores of which have started many feet above
the ground, so that these plants never know the ground
proper. They were born aloft, have grown aloft
generation after generation until they have forgotten
what it was like to grow up from the bottom, and
thus they have become epiphytes or even parasites.
Many of these, though never the primary supporting
trees themselves, have ingenious methods for con-
ducting, collecting and storing the rainwater ; either
all their leaves form a nest-like whorl, as is the
fashion of some Bromelias and Tillandsias ; or, may
be, one leaf is turned into a scroll.

A striking feature of such a tropical forest is that
it is composed of an astonishing number of different
genera and species of trees, forming the greatest
possible mixture, while continuous groves of one
kind are rarely met with. Whilst the temperate
region has extensive oak, beech and pine forests, no
such uniformity exists in the tropical belt unless we
ascend into the mountains. There is a cause for this
variety. The exuberance of life is so great, and
therefore the struggle for individual existence is so
severe that there is little chance for two trees of the
same kind to succeed in growing up side by side.
It is almost by a lucky accident that one grows up at
all where hundreds of other plants want to do the
same.

n] FEATURES OF ENVIRONMENT 23

Such a forest brings home to us what the struggle
for life really means and what it can do. Here it
is the struggle for sunlight and for rainwater and to
get them at first hand. One of the results is the
height of the trees, to which, so to speak, they have
forced each other, tall, often slender, branchless stems,
with an interlaced canopy above. A plant that can-
not grow tall by itself, climbs on to its neighbour's
shoulders. Even a cactus in a forest can climb like
ivy, and many of them have learned the trick so
successfully that they have been transformed into
epiphytes, either remaining still upright, or in the
guise of big, many-tailed pendent bunches.

Such is the forest. Let us now consider the
inhabitants. The observation of animal life is most
disappointing to the novice. He may roam about
in this gloomy forest for hours and hear little and
certainly see less. Where are the two hundred
different kinds of mammals, birds, reptiles, and am-
phibians which we know to exist in a Mexican tropical
forest? Most of them inhabit the top storey, the
roof-garden which is formed by the tree-tops. Tf by
a lucky chance we obtain a bird's-eye view from a
precipice or from a river, we behold a different world.
A dense green carpet overstrewn with mauve, pink,
yellow or white flowers, visited by butterflies which
are preyed upon by lizards and tree-frogs, these being
in turn sought after by tree-snakes. Of bird life also

24 THE WANDERINGS OF ANIMALS [CH.

there is plenty, often gorgeous and beautiful in colour.
Vividly coloured are also many of the other creatures,
frogs, snakes, lizards and butterflies. Colour has to
be laid on vividly, quiet coloration being out of place.
The blooms have begun the race. Red, yellow or
white, self-colours, are very effective against the green.
If a creature intends to be seen, for beauty's sake, it
has to use bright colours, since it is only by contrast
that it can attract attention. Again those which do
not want to be seen must dress as loudlv, and in tints

«/ /

as saturated, as are the prevailing tones of the en-
vironment.

Most of the tree-frogs are green, unless they are
delicate studies in brown with irregular markings
to suit the moss- and lichen-coloured branches upon
which they rest. Some have 'flash colours/ orange,
yellow or red on parts which are quite concealed
when the creature sits still. It trusts to not being-
discovered ; but touch him and there is a flash of
yellow in the air, which vanishes in a moment, the
frog also vanishing. He has dazzled his pursuer by
this sudden and unexpected display of colour, has
then caught hold of a leaf with some of his adhesive
finger disks, vaulted on to it and there sits demurely
indistinguishable from the foliage.

Many tree-snakes are green and so are many
parrots, motmots and other typical tropical forest
birds. Other parrots, pigeons, toucans are loudly

n] FEATURES OF ENVIRONMENT 25

coloured, but these very colours mingle with the
bright surroundings to a marvellous extent. Tropical
light can be so fierce and resplendent, that a whole
flock of bright parrots in a tree will simply vanish.
In a museum we find it hopeless to understand how
such conspicuous objects can ever manage to elude
discovery.

If we now descend in our survey below the tree-
roof there are of course many creatures which live
habitually upon the branches or stems of the trees.
These have sombre tints, brown, speckled or barred.
Lastly, those which live on the ground-floor, or in the
basement, are mostly dark. It would be of no avail
to wear a beautiful dress in a badly lighted place.

Another point concerning the coloration of
dwellers in forests is the pattern. Except when this
is more or less uniform, the ground-colour is broken
up by white or yellowish spots, arranged in several
longitudinal rows. Many snakes and lizards are thus
marked ; the young of many mammals pass through
a stage of this kind, notably those of deer, pigs, the
American tapir and those of the cat-tribe. There
are no striped lights in a forest ; what sunlight there
is, appears in the shape of little round disks, tiny
sun images, and these are — let us put it boldly —
stamped upon the skin. If we follow the same
kind of dark-skinned, white-spotted lizard out of
the forest into the savannah, into the grassland, its

2G THE WANDERINGS OF ANIMALS [OH.

corresponding race or species lias no spots, but longi-
tudinal stripes ; and the species of the same genus
which live in the desert have a pale ground-colour
with dark spots.

Most of the inhabitants of tropical forests lead an
arboreal life. There is no need for hurry, but they
must be able to climb well.

The majority of the Aiiura have acquired arboreal
characters. The hind limbs are long and slender, to
jump distances, and for catching hold of a leaf or twig
the fingers and toes are provided with adhesive disks.
Such arboreal Anura are found in all suitable forests,
and the significant fact is that these climbers by
no means all belong to the family of Hylidae, but
nearly every one of the various families of the Anura
has produced at least some typically arboreal genera
in spite of the considerable internal, structural differ-
ences which distinguish, for instance, toads from frogs.
The majority belong to the family Hylidae, but where,
as in Africa and Madagascar, there are no Hylas,
the 'tree-frogs' are modified Ranidae, since these
happen to be the material available for counterfeit-
ing them. In this respect the forests have succeeded
so well that it is for instance impossible to dis-
tinguish certain green tree-frogs of the African genus
Rappia from a Hyla, unless we cut them open.
If they lived side by side, which they do not, this
close resemblance would be extolled as an example

n] FEATURES OF ENVIRONMENT 27

of mimicry. In reality it is a case of convergence,
brought about by identical environmental conditions.
One might almost say that tropical moist forests must
have tree-frogs, and that these are made out of what-
ever suitable material happens to be available.

The same remark applies to tree-snakes, and it is
immaterial whether the available stock be boas or
pythons, harmless colubrines, cobras, vipers or even
pit-vipers. In India all these groups have con-
tributed. Typical tree-snakes invariably have a very
long, slender body with an excessively long whip-like
tail. Thus they can glide through the foliage from
tree to tree, their long body and tail always finding
some support.

Boas and pythons have short and strong pre-
hensile tails, and the numerous chameleons of Africa
and Madagascar have grasping hands and feet as well.
This principle of prehensile organs is carried to an
extreme in various mammals, of which it is sufficient
to mention monkeys and lemurs, the pangolins and
sloths among edentates, palm-martins among carni-
vores, arboreal porcupines among rodents, and opos-
sums among marsupials. All have either specially
modified climbing hands and feet, or tails, or both.

But the especial home of prehensile-tailed mam-
mals is in the tropical forests of America. There
alone live the prehensile-tailed monkeys. Nearly all
its marsupials are arboreal opossums. Even two

28 THE WANDERINGS OF ANIMALS [OH.

ant-eating edentates, Myrmecophaga tetradactylus,
and Cydothiirus didactylus, as well as the climbing
porcupines, Symtheres ; Cercoleptes caudivolvuliis,
the kinkajou, with its indiarubber-like tail-tip, is a
representative of the carnivores.

Another feature, peculiar to intensely arboreal
animals, is the principle of the parachute, some dis-
tension of the skin to break the fall. Some kinds of
the otherwise widely distributed frog genus Rhaco-
pJionis, in the Malay Islands, have the webs between
their fingers and toes enlarged to an almost absurd
extent, so that these ' flying frogs ' can glide through
the air in a slanting direction.

The little ' flying dragons,' Agamid lizards of India
and Malaya, possess a folding parachute, with stays
furnished by the much lengthened posterior ribs.
In Borneo lives a tree-snake which by spreading its
ribs and thus flattening and broadening the body,
is said to glide from tree to tree.

The parachute is carried to extreme perfection in
the now cosmopolitan bats ; less extensive parachutes
restricted to folds of the skin between the sides of
the body and the limbs, we find in other mammals,
mostly in the Malayan and Australian forests. For
instance Galeopithecus, the flying insectivore ; flying
phalangers among marsupials, the flying rodent Ano-
malurus in West Africa ; and of course flying squirrels
which have attained a wide holarctic range.

ii] FEATURES OF ENVIRONMENT 29

It is a very interesting fact, over which one may
ponder deeply, that where parachuting is such a
fashionable contrivance as it is in the Indo-Aus-
tralian countries, prehensile tails are almost absent.
The reverse is the case in the tropical American
forests in which there does not occur a single instance
of a parachute.

Intensely arboreal life leads to many other, some-
times most unexpected, habits, structural modifica-
tions, and sometimes to limited distribution. The
scroll-like receptacles of leaves, before mentioned,
hold water and some frogs use them as nurseries, or
they glue the leaves together, fill the space with a
foamy lather and deposit their eggs therein, the
development of which is so accelerated that the
babies are hatched as tiny frogs, having dispensed
with the tadpole stage. Or the male glues the few
but large eggs on to the female's back, a trick com-
mon in Africa and on the Seychelles. In some
Brazilian tree-frogs a slight fold of skin is raised
along the sides of the back, to prevent the eggs from
slipping off. In some other kinds these folds enlarge
during the hatching season into a kind of hood, e.g. in
Hyla goeldi. In a few tropical Americans this hood
has become a permanent organ, a pouch on the back.
Nototrema is the generic name of these marsupial
frogs ! It has been suggested, upon weighty reasons,
that even the marsupial mammals owe their survival

30 THE WANDERINGS OF ANIMALS [OH.

to the retention of the pouch in correlation with the
arboreal life which the immediate ancestors of all the
recent marsupials are known to have led. Arborealism
may have been forced upon the primitive, indigenous
fauna as a means of escaping competition against the
coming higher placental mammals.

Tropical forests teach two impressive lessons :
the awe-inspiring competition into which plants and
animals alike are forced in their struggle for life, and
the fact that the fight is so fierce, because the physical
conditions — plenty of warmth, water and food — are
so favourable to all. Every living thing is modelled
by adaptation to the prevailing surroundings, coupled
with the cumulative inheritance of the characters
acquired.

Deserts.

A characteristic essential feature of deserts is the
scarcity of rain. An annual amount of rainfall of less
than eight inches inclines a country towards desert
conditions. Much depends upon the distribution of
the rain, whether the few inches come down in the
shape of halt a dozen or more days of good rain, at
various times of the year in little doses, or whether
there is a drought of twelve months, or even longer,
and the whole scanty allowance pours down in one
dose, most of which is thus squandered since there is
no time for it to soak in. There are in fact various

u] FEATURES OF ENVIRONMENT 31

degrees of deserts, unmitigated deserts, periodical
deserts shading into rather arid stretches, semi-
deserts, and lastly steppes, pampas or prairies which
are subject to prolonged drought, periodical or un-
certain. As a rule bad deserts are surrounded by
a belt of half-deserts, and these pass into fair pasture
land. The French word prairie, the Russian steppe
and the South American pampa practically mean the
same, namely grassy plain.

We mostly associate with the idea of a desert a
boundless extent of sand without any vegetation,
but this is not necessarily the case. There are huge
deserts, which are stony, or rocky tablelands, or full
of chains of mountains, and again there are sandy
deserts with even tree-like growth on them, and
certainly with grass, which however may be so scanty
that one appreciates it only if he lies down upon
the ground and then observes the grey-green shim-
mer.

There are, broadly speaking, five such arid com-
plexes in the world.

1. The largest extends from the coast of North-
West Africa through the Sahara and thence with
many interruptions through Arabia and Persia into
North- West India ; the neighbourhood of Lakes Caspi
and Aral, Turkestan, great portions of Tibet and of
Mongolia, there as the so-called Gobi or Shamo, i.e.
sea of sand.

32 THE WANDERINGS OF ANIMALS [CH.

2. The greater portion of Middle and Western
Australia.

3. South- West Africa, from the coast of Damara-
land inwards, including the so-called Kalahari, which
however seems to be more like a steppe.

4. Parts of the South-West of the United States,
e.g. Salt- Lake desert, Californian desert, Colorado and
Mojave desert of Arizona. This complex stretches far
into Northern Mexico.

5. Parts of Patagonia and Argentina, and a
narrow strip along the west coast of Chile.

As examples of the smallest average annual
amount of rainfall the following places may be men-
tioned : Copiapo in Chile, less than J inch ; Mojave
(Arizona), Suez and Amu Daria (Turkestan) 2^ inches.
For comparison, Cambridge with 23 inches.

It is a common error that such deserts are the
beds of former seas. This is true of some, but by far
the greater part are not of marine origin ; moreover
an old sea-bed need not be barren. The factors
which cause deserts have nothing to do with the sea.
Most of those areas of land which have no river-
drainage into the sea are in time converted into
deserts. Witness the Salt Lake of Utah, the Caspi,
Aral and the Dead Sea ; they all are centres of sandy
deserts, because their rivers cannot carry away the
sand out of the country. Sand is, by the way, nothing
but the comminuted debris of rocks, of mountains.

n] FEATURES OF ENVIRONMENT 33

The disintegration of the rocks goes on quickest when
they are subject to great and frequent variation of
temperature. The sun heats and expands, the cold
of the nights contracts ; cracks are caused, water gets
into them, freezes and bursts them, etc. Every river
carries some sand. The sand of the seashore is
nothing but the ground down mountains of the far
inland, carried to the sea by the rivers. A look at
the map of Central Asia, Central Australia, or the
Sahara shows many river courses which run inland
and never reach the sea ; they either end in a land-
locked lake, or they lose themselves in the sand, all
of which they themselves have helped to carry down.
They are burying themselves. The more sand, the
more dust, and enormous dustclouds sweep over the
country forming shifting dunes, or they deposit
other so-called aeolic formations, for instance the
loess of China, a kind of loam, verv fertile if irri-

W

gated. But the greater the masses of sand, the less
becomes the rainfall and the making oT deserts
becomes intensified. Sometimes existing outlets are
barred by a slow steady upheaval of neighbouring
tracts of country, which are then doomed to become
deserts. The lakes of deserts are almost invariably
alkaline, salty or bitter because the rivers wash the
salt, saltpetre and other soluble mineral matter out
of the mountains, thus rendering the lakes increas-
ingly unfit for life.

G. 3

34 THE WANDERINGS OF ANIMALS [CH.

The making of deserts is still going on in various
parts of the world. It is quite likely that many of
the Central Asian desert regions were more habit-
able even within historic times, and that, when their
conditions changed for the worse great migrations of
the people were the result. (See Sven Hedin's and
Aurel Stein's descriptions of the sand-buried cities
of Tibet.) The same applies to the extensive ruins
in Arizona, New Mexico and North Mexico, affording
incontestable evidence of former thriving populations.

Now, what applies to people, applies also to other
animals. The change of a country from bushland or
a fertile prairie into a semi-desert may sweep off all
the original inhabitants if that change is quick ; but
if it is slow and gradual, many plants and creatures
will have a chance of adapting themselves to the new
conditions.

Such conditions are : (1) scarcity of water,
especially rain. (2) Abundance of sand and dust.
(3) Great variations of temperature, not only with
the seasons, but often daily. For instance in the
Mojave desert it may be insufferably hot in the
daytime, under a broiling clear sky with shade tem-
perature far above 100° F. ; shortly before sunrise,
owing to the unchecked radiation the water freezes
in an open pan. Before sunset you do not know
where to hide from the heat : amidst an ocean of
glaring sand, with sandspouts swirling over the

n] FEATURES OF ENVIRONMENT 35

plateau, hotter rocks, and nowhere a shade-giving
tree. Before sunrise the traveller shivers in his
blankets near the much needed camp fire.

Paradoxical as it may seem, there is often a heavy
dew. This is not so much falling dew, moisture
condensed out of the atmosphere by the cold ; it is
rather the direct evaporation from the subsoil and
this vapour is condensed near the ground before it gets
well into the dry desert air. In many sandy deserts
there is plenty of subsoil water, but the difficulty is
to get at it in drinkable quantities.

Animals and plants must have water. In the
desert they must be economical with it, not to pers-
pire but to have provisions for holding it, or to catch
even the smallest quantities. The roots of trees and
shrubs often go down to astonishing depths ; fre-
quently there is much more of such plants below
than above the ground. Many plants are furnished
with woolly hairs ; others have very narrow, slender
leaves, standing together like bunches of wire ; this
arrangement enhances the radiation, and the re-
sulting coolness causes deposition of the dew upon
them and this is what these plants want. Striking
examples are the Tillandsias, related to the Bromelias,
but instead of making a scroll, or rain-catching nest
of their leaves as they do in tropical forests, these
plants in arid regions grow upon the most exposed
branches of the trees and are transformed into small

3—2

36 THE WANDERINGS OF ANIMALS [CH.

grey branches of wiry tufts. There are no broad-leaved
plants : most of the leaves are lance-shaped, spiky,
thorny, e.g. Yuccas : or the leaves are large, thick,
full of juice, but covered with an air- and water-tight
epidermis, again spiky like the African aloes and the
American agaves ; or the plants have dispensed with
leaves altogether, having turned them into thousands
of hooks and spikes, and the whole, often large, stem
has a green rind. The chlorophyll is spread over the
stem instead of in the leaves ; for instance the cactus-
tribe of America, and exactly the same transformation
occurs in the Euphorbias of Africa where there are
no cacti. A large globular cactus stores water
sufficient to last it for years, or the plants adopt the
principle of the bulb. These produce a short-lived
glorious bloom in the short wet season, and during
the greater part of the year, or occasionally for several
years on end, the bulb sleeps unnoticed underground.
A very peculiar feature, not easily explained, is
that in arid districts the perennial vegetation always
grows in patches, with bare spaces between. This
patchiness is carried even further. Some sprawling
shrub gives, so to speak, shelter to other plants and
thus a little colony is formed, but it remains an
isolated patch and they never join. Sagebush, arte-
misias, hard wiry tussocks of grass, cactus, broom -
shaped leafless euphorbias, here and there a big tree-
like Yucca, are characteristic of desert vegetation.

n] FEATURES OF ENVIRONMENT 37

The general impression is the same in Africa, America
and Australia, often to a surprising extent, so that
it is difficult to believe that the respective plants
have all been evolved out of different and often
not closely related families.

Rain or the seasons produce a marvellous change
in the look of many a semi-desert. Within a few
days after a drought of perhaps 13 months the same
impressively desolate stretch of North Mexico is
transformed into a green prairie with countless
blooming bulbs, and there is plenty of animal life.
In Turkestan spring comes with a rush. The snow
melts rapidly under the warm south wind, a carpet
of tulips delights the eye for a few glorious weeks,
and in the month of May all this vegetation becomes
scorched and shrivelled and vanishes under the hot
blasts, the dust and sands of the desert ; and during
the long, severe winter it is swept by icy storms and
covered with snow.

Life in the desert is fearfully severe. There is
very little competition, a desert fauna is always
scanty, and there is plenty of room. But the struggle
to make a living and the fight against the elements
are so severe, that comparatively few creatures have
succeeded in adapting themselves to such a life.

Let us now consider some of their peculiarities.
The northern half of the Old World is divided by
a belt of enormous extent, from the Canaries to

38 THE WANDERINGS OF ANIMALS [OH.

Mongolia, which is unfavourable to amphibia, especi-
ally newts, a broad barrier which cannot be passed,
and there are none of them, except in China and
Burmah, south of this belt. Since these creatures
practically are restricted to the north of this belt, in
the Old World, we conclude that they had their
origin in the northern regions.

In Australian deserts some of the few kinds of
Cystignathid toads burrow into the clay of the
drying-up water pans ; the clay becomes hard-baked,
and there they sleep until the next rains, when-
ever these may fall. Their whole body-cavity, many
subcutaneous spaces and the bladder are full of
water ; the body is swollen into a shapeless mass,
ugly, without any pretty coloration. When the rain
releases them, they at once spawn, the tadpoles
develop with great rapidity, soon to aestivate as tiny
frogs. The adult gorge themselves with caterpillars
and beetles which are then also swarming, and
thus they fatten themselves preparatory for the next
torpid season, which may be protracted for several
years owing to the uncertainty of the rains. The
Australian desert members of the genera Chiroleptes
and Heleioporus are always ready to spawn ; to miss
the opportunity would be disastrous to the race in
a country where the meteorological conditions are so
uncertain.

Reptiles of the desert, to avoid the cold of the

n] FEATURES OF ENVIRONMENT 39

night, bury themselves in the sand by various con-
trivances. Some have a depressed, somewhat flattened
body, and the scales on the sides form rows of ledges,
so that a shuffling motion heaps the sand upon the
body. The scales are sharply keeled and so arranged
in slanting rows that the sand rolls by itself into
the required position. This also serves admirably for
concealment, and the head, sticking out, is armed or
rather dissembled by spikes, which then look like
seeds, fallen thorns or broken bits of pebbles strewn
over the ground. This is a striking likeness between
the so called horned toads, Phrynosoma of North
America and Mexico, which are Iguanids, and the
Moloch of West Australia and kinds of Phrynoce-
phalus of Turkestan, which belong to the family of
Agamids.

Almost all deserticolous lizards are great bur-
rowers. Some, which inhabit loose sand, for instance
many skinks, are quite smooth, slippery, without any
spikes, and the limbs show a great tendency to being
reduced to tiny stumps or to disappear altogether.
These creatures literally swim wriggling through the
sand. In America, Africa and Asia the numerous
kinds of the families of skinks and of tejus show
stages from fully developed limbs to none, wherever
there is a desert. Illustrations of convergent evo-
lution.

The nostrils of such dwellers in dry sand can be

40 THE WANDERINGS OF ANIMALS [CH.

closed by neat valves. Some have strong ridges over
the eye-brow region, formed by modified scales to
make the sand fall off properly when the creatures
emerge. The ear-opening is protected by a fringe
of scales, or it is very small, even quite abolished.

Most wonderful is the protection of the eyes. In
many desert lizards the lower eyelid has a trans-
parent disk in its middle, so that when this lid is
drawn up, the eye is closed and yet the lizard can
see. Several species of the Lizard genus Eremias in
India and Africa and the Indian Cdbrita possess such
a transparent window. In another Lacertid genus,
Ophiops, this arrangement is carried to the extreme.
The transparent lower lid is permanently drawn up
and fused with the rim of the much reduced upper
lid. Exactly the same modification has been hit
upon by Ablepharus, a genus of skinks widely dis-
tributed in the Old World, and by Xantmia in the
Californian and Mexican deserts.

To enable certain lizards to run over the sand,
they have lateral fringes on the fingers and toes ; for
instance the North American Iguanid Uma, in Turkes-
tan and Persia the Agamid Phrynocephalus ; and what
is more surprising, the same occurs in some desert
geckos, e.g. Ptenopus and Stenodactylus of Africa,
and TeratoscincKs in Turkestan. Reference has been
made to the growth of the vegetation in patches. Con-
nected with this is the astonishing quickness of many

n] FEATURES OF ENVIRONMENT 41

dwellers in deserts. Lizards are fond of disporting
themselves in the open, to feed, to play and to bask.
Their only shelter, if they are not diggers, is afforded
by the tussocks and shrubs, to reach which they have
to run fast. Desert snakes, excepting those which
dig, and have rough oblique rows of scales like Eryx
or Echis, are remarkable for the great number of
ventral shields and these correspond with the number
of vertebrae. To be overtaken in the open, with
places of refuge far and wide between, is detrimental ;
the most alert and quickest is most likely to escape,
or to win if he is the aggressive foe.

The characteristic feature of desert mammals is
their swiftness, and their large ears if they are
nocturnal. Toes short and compact, close together,
limbs elongated and slender. Witness the gazelles,
springboks and other antelopes. Or there is the
tendency to elongate the hind limbs, while the fore
limbs remain short or even are shortened. This
principle leads to the more typical dwellers in plains
and semi-deserts, as illustrated by the jumping kan-
garoos of Australia ; the same modifications, different
in detail, but with precisely the same effect occur
in the jumping hares, Pedeies (a rodent) and in
the Macroscelides or elephant shrew (Insectivore) of
Africa, the little Jerboas Dipus, in South-East Russia
and Asia ; and North America has produced similar
jumping mice of the genus Zap us. All have a rather

42 THE WANDERINGS OF ANIMALS [CH.

long, balancing tail, often with a tassel of long
hair.

Water being scarce in deserts the inhabitants
eke out the deficiency by the dew, or they are forced
to wander far and wide in search of scanty pools.
Various ruminants have developed an astonishing
power of enduring long intervals between drinks. In
Mexico and Arizona, for instance, and around the
Indian desert the cattle can sometimes return to the
drinking places only every other, or even every third
day, because the scanty pasture obliges them to roam
so far afield. We all know of the unique water-
storing arrangement of the camel's stomach which
enables these animals to subsist for well-nigh a week
upon the thorniest and driest of food without a drink.
But the most universal feature of nearly all desert
animals is their coloration, be they birds, beasts or
creeping things. They all are of the colour of the
desert, shades of yellow, light brown, reddish, sandy ;
often very pretty in delicate detail, with wonderful,
small patterns. Black, white, blue and green are
absent. Many of these animals are monochrome ;
stripes are absent. If the ground-lizards are not
monochrome, uniform in colour, the runners among
them have a pale ground-colour with dark spots.
The harmony between deserts and their inhabitants
is striking. Every animal has those colours and that
patteni stamped upon its dress which make up the

ii] FEATURES OF ENVIRONMENT 43

average sum-total of the characteristic colours, lights
and shades of its usual environment. The main
advantage of this harmony is protection. This does
not mean only concealment and protection from
enemies, from other creatures ; to an equally great
extent it means protection from elemental influences,
as temperature and sun rays, also from the colours
reflected by the environment. The prevailing colours
of the desert being shades of brown, reddish and
yellow, only a dress of the same tints can possibly be
in physical equilibrium with the desert ; and there
is no vivid white, black, blue or green, because those
colours are physically impossible in the desert.

High Mountains and Vertical Distribution.

A universal feature of mountains is the decrease
of temperature with increasing height, the result
being a so-called arctic climate if the mountain is
high enough, with preponderance of snow and subse-
quent suspension, or suppression of life.

Since, as a general proposition, temperature de-
creases also from the equator to the poles there is a
fixed correlation in the temperature of a mountain
station between its latitude and its height. This law
of latitudinal equivalent in altitude has been formu-
lated by A. von Humboldt, the father of the study
of vertical or altitudinal distribution.

44 THE WANDERINGS OF ANIMALS [OH.

Broadly speaking the annual mean temperature
decreases towards the poles at an average of 1° F.
for each degree of latitude. With increasing height
the temperature falls nearly a thousand times as
rapidly, namely 0*5° centigrade for every 100 metres;
this is equal to lc F. for every 365 feet, an easy
number to remember. On mountains the rate is
somewhat greater, 1° F. = 300 feet. Given the tem-
perature and height of a lower station and the height
of the mountain its temperature at the summit can
easily be calculated1. In our latitude a mean annual
temperature of 32° F. or 0° centigrade is reached at a
height of about 5000 feet, but under the equator this
'snowline' lies at about 15,000 feet, and near the
arctic circle it approaches the level of the sea.

Atmospheric pressure also decreases, roughly by
1 inch with every 1000 feet of elevation, so that at
a level of 10,000 feet we experience only two-thirds
of the normal pressure at sea-level ; which implies of

d

1 The formula for centigrades and metres is Ut = Lt-

200'

d

For degrees of Fahrenheit and feet the formula is Ut = Lt-

300
[ft = Mean temperature of the upper station.

£/ = Mean temperature of the nearest known lower station.
d = difference in height of the two stations.

Example : Highest mountain 5000 ft.

Temp, at nearest sea-level 50° F.

Temp, on top = 50 - ^ ^=50 - 17 = 33°F.

ouU

n] FEATURES OF ENVIRONMENT 45

course that the same volume of air contains only
two-thirds the amount of oxygen. Animals rapidly
taken up to high levels find it difficult to adjust
themselves to these conditions. The thinness of the
air, combined with the cold, causes absence of vapour ;
radiation, loss of warmth of the ground heated by
the sun's rays, is unchecked. On the other hand
moisture in the air diminishes the loss of heat by
radiation and directly increases the temperature of
the atmosphere, because the warmth given off by the
heated ground is largely absorbed by the aqueous
vapour. Consequently on a brilliant day, on a high
snow field it may be scorching hot in the sun, whilst
the temperature of the air, as measured in your own
shade, shows several degrees of frost.

In the temperate and cold regions the differences
due to latitude and altitude are greatest in the
winter and least in the summer. Under the tropics
the differences due to altitude are greatest within the
24 hours of day and night. It follows that places of
the same mean annual temperature may have widely
different summer temperatures ; and conversely that
places receiving the same amount of summer heat
may have widely different annual means. The sig-
nificance of these facts becomes apparent in the
study of the distribution of animals and plants. The
distribution of the various species is governed in
the main by the temperature of the warm season,

46 THE WANDERINGS OF ANIMALS [cH.

whilst the mean annual temperature is of little
consequence. In many cases the lowest extremes
of temperature are also important. If you want
to cultivate Indian corn at a certain place its mean
annual temperature may be dismissed ; the success
depends upon the number of days sufficiently warm
to ripen the corn, and we are not concerned about
the cold of the winter. The latter may, however, be
of great importance to the growth of perennials,
shrubs and trees.

Temperature and humidity seem to be most
important factors in distribution.

High mountains have a more or less permanent
belt of clouds ; what determines its height above
the neighbouring plain is not known. This belt is
naturally the zone of greatest moisture ; although
it rains more below, the permanence of such a belt
ensures greater effects of the moisture. A mountain
standing on the southern edge of a plateau has a
higher temperature at a given altitude on its north
slope than on its south side, because the sun-warmed
surface of the plateau is nearer to the mountain top
than is the lower, although hotter, southern plain.
This explains why, e.g., in the Himalayas the snow
and timber-line on the north side are about 3000 feet
higher than they are on the south side.

The side of a mountain exposed to the prevailing
sea wind is moist, whilst the lee side may be arid.

ii] FEATURES OF ENVIRONMENT 47

Thus the western coasts of India, exposed to the
monsoon, have a much greater rainfall than the inland
districts on the other side of the coast range. In
Mexico the Pacific side is much drier than the very
wet Atlantic side, this difference being responsible
for remarkably different faunas and floras.

The possible number of floral and faunal zones on
a mountain is greatest in the tropics, since its base
may be in the hot tropical lowlands and its top above
the permanent snow-line. A mountain of the same
height, but situated in the arctic region, may be
entirely within the snow-line. The width of the
zones (not of course their vertical thickness), and the
abruptness of the change from one to another are
proportional to the steepness of the slope.

Every 'complete' mountain arising high within
the tropics shows the following five belts or zones.

1. Tropical belt. Climate hot, according to cir-
cumstances either moist or dry, or both according
to seasons. Vegetation evergreen, but deciduous
when there is a pronounced dry season. The upper
limit of this zone may be put near 3000 feet above
the level of the sea.

2. Warm temperate belt. The difference between
summer and winter begins to get marked, and there
may be cool nights. Vegetation chiefly evergreen,
and if the leaves are deciduous this is due to a pro-
longed dry season.

48 THE WANDERINGS OF ANIMALS [OH.

3. Cool temperate belt, frequently coinciding
with the normal cloud-belt. Those trees which are
deciduous lose their leaves during the winter season,
which is well marked. The upper limit of this belt
coincides with the 'upper tree line.'

4. Cold belt. Characterised by grassy slopes
wjth abundance of flowering annuals. Higher up
the grass gives way to mosses and lichens.

5. Arctic belt, the lower limit of which is near
the permanent snow-line, which within the tropics is
somewhere near 15,000 feet elevation.

Now, since an isolated mountain is like a cone,
it is of the greatest significance that its successive
vertical zones, if projected in Mercator's fashion, are
practically repeated in a grander scale by the zones
on a map of the northern half of the world. We
may compare the mountain cone with the northern
hemisphere of a globe. The agreement is somewhat
distorted by the configuration of the continents, by
the high elevation of Central Asia and by the in-
troduction of deserts. There are in the northern
hemisphere :

1. A tropical belt, either moist, with tropical
forests, as in Central and South America, parts of
Africa, Indo-Malaya and Papuasia ; or dry, ' torrid,'
like the Sahara and Arabia.

2. A warm temperate belt, sub-tropical.

3. A cool temperate belt, with much woodland

n] FEATURES OF ENVIRONMENT 49

and arable land ; abundance of mostly deciduous
trees and shrubs.

4. A cold belt across Canada, Scandinavia,
Northern Russia and Siberia, which belt includes
the northern tree-line, to the south of which are
huge timber forests, composed chiefly of conifers.
Enforced hibernation during the severe winter.

5. The arctic, circumpolar region, with pre-
valence of ice and snow ; the permanent vegetation
represented mainly by mosses on the Siberian
* tundras,' by lichens on the North American * barren
lands.'

Because of this agreement the study of certain
climatic effects upon the ' Biota,' i.e. flora and fauna,
can be made on a complete mountain within a small
compass. We can also investigate the effect of the
change of habitat.

Let us take the simplest case, a mountain with its
whole base in tropical lowland. Its whole Biota may
then be assumed (excepting the few instances of
conveyance by wind, etc.) to have ascended from the
plains, and if the top species are different from those
at the bottom, they probably have been modified by
the conditions prevailing on the mountain.

The case is more complicated if the mountain
has two bases, one in the tropical lowland, the other
a high temperate plateau, which probably has an
endemic Biota of its own, differing from that of the

G. 4

50 THE WANDERINGS OF ANIMALS [OH.

likewise extensive lowlands. The Biota of such a
mountain will be a compound from two perhaps very
different sources.

Or the mountain itself may have an original Biota
of its own, especially if the mountain is due to a
process of folding or other rising of the crust of the
globe, instead of being a piled-up volcano, which
would of .course begin as an absolutely barren terrain.

Lastly, the most complicated conditions prevail
if the mountain forms part of a long range extending
into distant countries. In this case it is an impor-
tant consideration, whether such a range runs from
north to south like the chief systems in America, or
from west to east as they do in the Old World.

Whilst west to east, latitudinal or zonal ranges
often act as powerful barriers, shutting off a southern
from a northern Biota, a north to south, longitudinal
or meridional range more often acts as a conductor
in the exchange of southern members to the north
and for northern migrants into the south. This is
especially the case, when, according to the law of
latitudinal equivalent in altitude, such a range
begins low in the north and increases in height
towards the south. An excellent illustration is the
great central plateau of Mexico which begins at the
northern frontier with a few thousand feet elevation
and steadily rises to 7500 feet near Mexico City and
there forming the northern base of some of the giant

n] FEATURES OF ENVIRONMENT 51

mountains, whilst the other side slopes rapidly down
into the hot lands.

The component species of the faunas and floras of
such mountain zones can be collected and studied as
to their affinities and variations. Some creatures
seem to be quite indifferent to climate, and there-
fore have a long vertical and horizontal range. The
puma, for instance, ranges from Canada to Patagonia ;
it makes raids into the hot lands and ascends to the
upper tree-line. The nine-banded armadillo is equally
at home in the moist hot lands and in the clammy
pine forests of 9000 feet elevation in Mexico. A
certain kind of small lizard, Sceloporus microlepidotm,
of the same country occurs in the lowlands and
ascends to the very tree-line where it is obliged to
hibernate through perhaps half the year, whilst below
it aestivates during the torrid season. Other species,
although scattered widely over the country, have a
very short vertical range, so strictly limited that these
animals and plants indicate the elevation above sea-
level as safely as a barometer. Ultimately most
animals are dependent upon the vegetation, the state
of which depends greatly upon climate and soil. The
jaguar lives on herbivorous game. Rattlesnakes sub-
sist mainly upon rodents, and mice ascend as far as
there are roots and seeds for them to eat. Where the
winter time is severe many animals have either to
migrate into lower, warmer climes, or they are forced

4—2

52 THE WANDERINGS OF ANIMALS [CH.

to hibernate ; even during the cold nights of their
summer the cold-blooded kinds become lethargic. In
conformity herewith we find that specimens of the
same kind, which in the warmer zones live an all-the-
y ear-round life, have learned to hibernate in the upper
levels. High up there under the very tropics, but at
10,000 feet elevation, the summer is so short that

7 /

stationary creatures like lizards and snakes lead only
a kind of one-quarter life. This implies that, for
instance, a four-year-old snake has really lived, that
means to say eaten, grown and loved, only for twelve
months. The result is that many a high -mountain
fauna contains not a few small-sized species in com-
parison with their more favourably placed relations
lower down. Another result seems to be that many
cold-blooded vertebrates have given up the laying
of eggs which might not be hatched on the clammy
ground, and have become viviparous, undoubtedly a
safer mode of looking after the welfare of their kind.

The present writer has made a special study of
altitudinal distribution in Mexico. It remains to be
seen whether the following conclusions apply to other
countries, and therefore are widely applicable general
laws.

1. Hot land species ascending into cooler zones
are liable to lose their specific characters and to
assume others ; that means to say they change into
new species.

n] FEATURES OF ENVIRONMENT 53

2. Temperate species are more powerfully in-
fluenced by ascent into the cold zone, than by descent
into the hot lands.

3. The change into a colder environment is a
more powerful factor than change into a warmer
climate.

The Mexican Biota is composed of (1) endemics,
(2) nearctics, immigrants from the north, (3) neo-
tropical immigrants from the south. Of these the
nearctics are more long-ranged than the tropicals,
i.e. they are more hardy, in the sense of being re-
sistant, dominant, able to accommodate themselves
to new environment without becoming changed. The
short-ranged among the nearctics are mostly those
which have become modified for cold life.

Since the majority of the genera and species of
tropical or southern origin are short-ranged, this
means either that they are softer, more pliable, re-
cessive ; or that they are more influenced by ascent.
Species B at the bottom has changed into B1 in the
middle region, and into B2 towards the top ; hence
three short-ranged species. A hot land or bottom
species can obviously change only into cooler climes,
but an originally temperate species may ascend or
descend.

If the three rules enumerated above hold good,
it seems paradoxical that denizens of the hot lands
transported into a cold place stand this change much

54 THE WANDERINGS OF ANIMALS [CH.

better than specimens taken from a high mountain
down into the tropics. We ourselves experience the
same effects. No doubt more diseases are rife in the
tropics, especially bacterial and parasitic. But this
does not go to the root of the problem. A tropical
creature, or plant, transported into a cold region,
may live, but it will not breed, or ripen its seeds.
A cold country species introduced into the tropics is
much more likely to die from the. shock, but if it lives
it will breed. Many tropical plants can be cultivated
in temperate countries where they have to adapt
their economy to shorter summers, whilst northern
plants, subjected to tropical conditions, are mostly
failures since they exhaust themselves through want
of rest. Annuals seem naturally to have better
chances than perennials. But nature's way of alti-
tudinal spreading is slow and steady, not by sudden
transports.

Cold can be counteracted in many ways by animals,
as by more food, motion, shelter, a warmer coat, etc.
But transference from the changeable temperate to
the hot zone with its much more equable climate
always implies an excess of warmth over that which
the species was accustomed to.

If the third rule allows of general application it
would be of far-reaching importance ; it would allow
the further conclusion that a world-wide lowering of
temperature has been a most powerful factor in the

ii] FEATURES OF ENVIRONMENT 55

production of new forms of life. Let us apply this
principle to geological changes.

Elevation of a whole country, or of a range of
mountains, or a cold epoch following upon a warm
one, would be very productive of new forms. The
same effect would be produced by the spreading of
a glacial epoch from the pole. The tropical creatures,
coming under the cooling influence, would change
readily, and the old species within the polar circle
would be changed into arctic forms, as the glacial
wave passed over them. But those which, for some
reason or other, were driven south, would remain
unchanged because they counteract the new climatic
influence by their migration. Such a glacial epoch
would thus bring about a great faunistic interming-
ling, but it also would actually produce new forms,
namely arctics, and those transformed southerners
which did not, or could not, withdraw.

What would happen with the turn of the tide,
when a spell of warm climate spreads again towards
the pole, as has taken place during the so-called
interglacial epochs? No changes whatever, except
that the arctics will die out or remain occasionally
. as derelicts, while all the rest, both northerners and
southerners alike, will surely reclaim the old ground
so far as it suits them. There will be comparatively
little making of new species, provided our principle is
right, that increase of temperature has a minor effect.

56 THE WANDERINGS OF ANIMALS [OH.

It would be absurd to conclude that cold is a more
favourable factor to life than warmth. It is quite
a different question whether a change from hot to
cold may not have a profoundly stirring influence upon
organisms. The Permian period was one of widely
spread coolness, which has played havoc at least
with the marine fauna, by reducing its numbers of
individuals and species, but it also ushered in, or
prepared, a new and remarkable terrestrial verte-
brate fauna. Our last northern glacial epoch may
have killed out much of the warm Pliocene life, but it
has given us the present arctic fauna, which is very
considerable, and remarkable for being very up-to-
date, singularly free from old-fashioned types. The
place for these are the tropics, because there the
climate has changed least in the equatorial belt,
which seems to have been hot since the Triassic
period.

A statement which has been repeated so often
as to amount almost to a creed, is that the typical
animals and plants of snow mountains in the temper-
ate and even in the tropical regions have their nearest
relations in the arctic regions ; that they are derelicts,
shut off* by the recession of the glacial epoch, instead
of being modifications, suited to a more rigorous
climate, of the lower or basal faunas of the country
in which these mountains are situated. This is a
much overrated statement. These faunas and floras

ii] FEATURES OF ENVIRONMENT 57

have an arctic ' facies ' or look, mostly cases of con-
vergent evolution, and the term arctic, if used for
such high-alpine organisms, must not be confounded
with boreal or polar. In fact true instances of boreal
derelicts on far southern mountains are very rare.
The idea was based upon the supposed similarity
between Scandinavia and the Alps, the favourite
example being the arctic hare. This Lepus varia-
bilis turns white in winter ; its present distribution
is circumpolar, from Scandinavia through Siberia to
Alaska and Greenland and Newfoundland, but also
in Scotland, Ireland, in the Pyrenees, Alps, the
Caucasus and in Japan. But none of the other
typical arctic animals are found in the Alps, neither
reindeer, polar fox, glutton or wolverene, lemming,
or snowy owl. Nor do any of the creatures, typi-
cal of high mountains in temperate countries, like
steinbok, rocky mountain goat, bighorn and argali,
marmot, chinchilla, extend their range into the polar
regions. We agree with those authorities who ex-
plain the occurrence of the comparatively few closely
related species of animals and plants in Scandinavia
and the Alps as due to independent immigration from
some common Central Asiatic centre.

It is always difficult to prove a case of convergent
development. It can so easily be ruled out of court
in the present instance, because we know that during
the height of the glacial epoch the northern ice-sheet

58 THE WANDERINGS OF ANIMALS [CH.

extended southward to a line drawn from London to
Moscow, and the strip of country intervening between
this line and the Alps and Pyrenees was certainly
cold enough to support reindeer in the south of
France and lemmings even in Portugal, so that there
may easily have occurred a shifting of Scandinavians
to the Alps, and the reverse current of spreading
with the recession of the ice-sheet. Such spreading
and contracting with consequent isolation has no
doubt taken place in many parts of the world. We
must resort to it for the present discontinuous dis-
tribution of many similar, even identical, species on
that large system of mountains from the Pyrenees,
the Alps, the Caucasus, right into and beyond Central
Asia.

But this same principle emphatically cannot
be applied to the many alpine districts which exist
within the tropics and are isolated from each other.
Here we have to remember that most of the great
ranges of the world are of comparatively recent date,
chiefly mid-Tertiary ; and as during these epochs the
world seems to have enjoyed a decidedly warm
climate, it follows that the respective faunas and
floras must have assumed their ' arctic facies ' after
the origin of these mountains and independently of
each other.

n] FEATURES OF ENVIRONMENT 59

Summary of the Influence of Environment.

Having reviewed the main features of the faunas
characteristic of forests, deserts and high mountains,
each of which may be taken as intensified samples of
environment, we may draw some conclusions.

Since it is obvious that typical desert specialists
cannot live in forests, and as high mountains also
possess inhabitants of their own, it follows that these
various faunas can have attained their present, often
widely scattered, discontinuous range only under one
of the two following conditions. Either the respective
faunas had a multiple origin, and are instances of
convergent evolution where similar environmental
conditions prevailed ; these cases are of enormous
biological importance. Or, if the respective creatures
are truly blood-related, above all if they belong to
the same genera or species, they must have spread
from a common centre. This would imply continuous
forests for some, uninterrupted deserts for others,
extending perhaps all over the world, not necessarily
at the same time, but forest succeeding desert, and
arid highlands taking the place of lowland swamps.
The mere emergence of a land-bridge would help no
monkey across, unless or until it was covered with
suitable vegetation.

If the specialised features of the dwellers in forests
and deserts had arisen from preformed latent variations,

60 THE WANDERINGS OF ANIMALS [OH.

to be picked out by natural selection, and further
developed by cumulation, it would follow that each
ancestral group possessed a whole arsenal of every
kind of variation, ready to be selected when occasion
required it. Descendants of the same frog, which
found themselves in a forest, drew upon its incipient
finger-disk variations, be these ever so tiny ; others,
in inundated country, improved upon the webbed
propensities, and yet others encouraged those varia-
tions which assured a chance of digging feet. This
is of course, to a certain extent, our idea of a ' general-
ised ancestor,' some kind of anurous Amphibian, for
all the toads, frogs and tree-frogs.

This view implies that by this time the arsenal
of variations has been exhausted, there being in
forests only forest creatures, in deserts only desert
specialists, all of which have of course lost the other
non-fitting characters by the process of weeding out.
Consequently any further change in the environment
would kill the present faunas. What was easy for an
indifferent organism, must have become increasingly
difficult for the specialist, and an all-round speciali-
sation in every direction is impossible. This is covered
to a great extent by Cope's law of the over-specialised,
and by D. Rosa's ' progressive reduction of variability/
We cannot here enter into a discussion of these
important topics. Suffice it to say that variability is
not the same as the incessant cropping up of slight,

in] SPREADING 01

spontaneous variations in every direction ; it is the
plasticity of the individuals, their being able to be
moulded by circumstances. That this plasticity
should react so quickly and to the point, if not
impaired or lost by specialisation, is itself the outcome
of the long training which protoplasm has undergone
since its creation. This very quickness seems to have
initiated our mistaking the variations called forth for
something latent or preformed.

In nature's workshop the successful competitor is
not he who has ready an arsenal of tools for every
conceivable emergency, but he who can make a tool
on the spur of the moment. The ordeal of the
practical test is Darwin's and Wallace's elaborated
conception of natural selection.

CHAPTER 111

SPREADING

SINCE there are now countless species and genera
with a very wide, continuous or scattered distribu-
tion they must have attained this range by spreading
from centres where the respective kinds made their
first appearance. The fundamental impulses to all
spreading, wandering, migrating are hunger and love

62 THE WANDERINGS OF ANIMALS [CH.

and the fact that two creatures require more space
than one.

If cattle require three acres of grazing land per
head to keep themselves during the year, a herd of
one hundred must have 300 acres, and if this herd
increases to 1000 head it must have 3000 acres
of grass land, to find which, however, they may have
to roam over much more than five square miles.
Thus they spread. From a broad point of view
spreading proceeds peripherally, in epicycles, each
pair representing a centre of its own, and since the
middle of the area is already occupied, new land is
available only outside. This spreading may be a very
slow process, but it tends to increase by geometrical
progression, and there is practically unlimited time.
If a couple of earthworms are sufficient to occupy
one square yard per year with their offspring, their
descendants long before 30,000 years (a not im-
probable estimate of the time since the end of our
glaciation) would have choked the whole world1.

1 This time-honoured kind of calculation implies a great fallacy.
It IB, to a certain extent, applicable to animals with practically
unlimited power of locomotion, for instance to a herd of cattle enter-
ing a new, unoccupied country. In the case of earthworms the
actual resulting numbers would soon be infinitely less than the
calculated result, because of the choked, inner parts of the area, the
inhabitants of which could not possibly pass over those living near the
periphery, where alone new land and food is available. In a few years
the centrifugal velocity of spreading, necessary to cope with these

in] SPREADING 63

Supposing a family moved, gipsy fashion, only on
one day every week, and not more than three miles,
then it would cover about 156 miles in one year.
For example, the Mongols, crossing Behring's Strait
might have arrived at this rate at the Straits of
Magellan in about 50 years.

Let us follow the herd of grazing cattle. They
roam about mainly in search of food ; they follow
the grass. Where its growth is seasonal, the beasts
make seasonal ' migrations,' like the American bison,
which moved twice annually between Canada and
Mexico. What we usually understand by periodic
migrations cannot have sprung into existence sud-
denly ; it is more like the cumulative effect of the
doings of countless generations. The faculty of
shifting the abode was of course always there, the
necessity of moving further on was also present, and
those members of a species which went in the wrong
direction came to grief, whilst the others flourished
and could return with their progeny. At first they
did not cover great distances, but just enough to find

conditions, would surpass all reasonable limits. The phenomenon
is comparable with the progress of a ' fairy-ring ' except in so far as
the inside will contain a population of just comfortable density. If
we apply these considerations, the ring of worms will be found to have
made astonishingly little progress in a thousand years, and, except at
the periphery, the whole area will contain at best only a comfortably
dense population, instead of countless millions.

64 THE WANDERINGS OF ANIMALS [CH.

unoccupied ground. The annual repetition became
an established habit, at last an ineradicable instinct.

The prime impulse is want of food. The new
growing grass on the prairie attracts every year those
creatures which live upon pasture. The tropical belt
of the world is so crowded that there is the keenest
competition, whilst in the temperate and cold regions
occurs a long winter unfit for the support of many
kinds, whereupon in the summer these same regions
are covered with new vegetation, with its concomitant
abundance of insects and other invertebrates. The
tables are decked again, and these opportunities are
not wasted.

Hard and fast differences between periodical mi-
grations, sporadic changes of the abode, and other
fluctuations do not exist, they are a question of
degree. The grey plover of America breeds within
the arctic circle and winters in tropical countries ;
many other birds shift their abode only a few hundred
miles. To complicate matters further, it is not neces-
sary that the migration be undertaken periodically,
more than once, by the same individual. The common
eel ascends the rivers as an ' elver,' in its youth ;
years after, it returns to the sea, there to breed and
die, whilst many other fishes come and go, year after
year. Many birds are still immature in their second
year, and yet they migrate like their adult relations.
It seems permissible to take this fact as an indication

in] SPREADING 65

that the breeding as such is not a prime reason for
their wanderings.

The phenomenon of migration, in its most striking-
cases, is now very complicated. Many a bird goes to
the very arctic regions for the shortest of summers,
and it spends most of the year within the tropics or
it may even overshoot the equator and winter in
a south temperate country. On the other hand the
members of many species do not all go so far north,
but stop and breed in the intermediate regions. We
must not take the extremes when trying to unravel
the development of the problem.

It has been argued with some show of reason that
the real home of a bird is that country in which it
was born, where the species breeds, but this is not
in every case a valid conclusion. Although it applies
to most creatures, there are so many exceptions that
we must leave sentiment aside. When it comes to
a question of domicile, the ten weeks' sojourn of the
swift in England are to be set against the nine months
or more which these birds spend in Africa. The
breeding time is the busiest period of a bird's life.
Then the numbers of each species are suddenly
multiplied and so is the stress of providing food, and
the particular kind of food which is best for the
young may not be available in every country.

Speaking broadly, any migratory bird breeds in the
coldest climate which it visits on its migration ; this

y. 5

66 THE WANDERINGS OF ANIMALS [CH.

means that it requires a pronounced spring or early
summer season. The idea that the arctic circle was the
original home of the many kinds of birds which breed
there, whence they are now annually driven away by
stress, has been coupled with the glacial epoch, that
panacea of so many difficulties. One had only to
assume that the progressive glaciation drove the
ancestors away from their circumpolar home, towards
the equator, and that when times improved again,
the birds returned to their old home. This plausible
view implies several monstrous assumptions. The
birds are supposed to have inherited such a loving
reminiscence of their old home that they returned to
it after a banishment of thousands of generations.
The enforced sojourn, and of course the breeding of
all these generations, was not sufficient to naturalise
them, to supplant the love of their prehistoric home !

That the last glacial epoch has driven the limit of
many kinds of animals and plants further south, is as
certain as that many have recovered the lost ground
after the recession of the cold spell, but this must
have been by very slow and steady process of spread-
ing. It probably does account for the present annual
visitations of arctic lands, but as a phenomenon which
has been evolved de novo, which would have come to
pass even if no birds had existed in preglacial times.

The question how birds manage to find their way
thousands of miles across land and water, has been

in] SPREADING 67

extolled as a mystery of mysteries. That they can
cross many hundreds of miles of sea without stopping
is a fact ; it means an amount of endurance which we
do not expect in small birds. The whole question
reduces itself to a sense of direction, a faculty which
is possessed by nearly all animals, e.g. the proverbial
cat which escapes out of the bag and finds its way
home. There is no mystery, except that we, the
most intellectual of mankind, should so well-nigh
have lost this sense, and even this regrettable fact
is simply an instance of the loss of a faculty through
long continued disuse.

In comparison with the periodic, annual migrations
of so many birds, those of other creatures are scarce
and insignificant, excepting fishes.

The most regular and least limited migrations
among mammals seem to be those of the eared seals.
The walrus goes northwards in the summer. The
cetacean Delpkinapterus leucas regularly ascends
the Amoor to a distance of 400 miles, when the ice
breaks. Certain bats are supposed to migrate.
Various kinds of game have been recorded to make
periodic wanderings over the South African veldt.
Such instances are obviously a mere matter of com-
missariat.

The so-called migrations of the lemming are
instructive. They are quite sporadic, stampedes.
When owing to combination of some favourable

5—2

G8 THE WANDERINGS OF ANIMALS [CH.

circumstances these rodents suddenly increase, enor-
mous numbers radiate from the highlands of Norway
into the lowlands. At any given spot they seem to
keep to the same direction, but taken as a whole,
they disperse to anywhere. The overcrowded con-
dition of their homes impels them to leave, and this
impulse they follow blindly, even, it is alleged, into
the sea. But they do not attempt to settle in a new
district. A year or two after such an irruption not
a lemming is to be found, and where, during the
stampede they came across suitable districts, they
found these already occupied by resident lemmings.
The same applies to the countless numbers of sand-
grouse, Syrrhaptes paradvxiis, which in the spring
of 1888 came from somewhere in Central Asia and
spread over the whole of Europe, like a wave reach-
ing from Norway to England and Spain. Many did
breed in suitable places in the same year, few in 1889
when thev were exterminated.

•i

Such and similar irruptions have no doubt taken
place often during the world's history, and yet such
sporadic stampedes into a foreign country hardly
ever lead to regular settlements, especially if such
a country already possesses a kindred fauna of its
own. Almost every year some North American birds
are reported on the west coast of Europe ; but
although such stragglers must have come over to
Europe for thousands of years, the respective species

iv] NUMBERS AND DENSITY OF SPECIES 69

have not established themselves here. Many fishes
make periodical migrations for breeding purposes
and in enormous numbers. The herring and the cod
and their kindred collect on certain breeding grounds.
The tunny, which has a world-wide distribution, passes
through the Straits of Gibraltar into the Mediter-
ranean Sea in the month of May there to breed, and
in the month of July it returns to the ocean.

Many, known as anadromoits, ascending, fishes,
feed and mature in the sea, but ascend the rivers as
the impulse of reproduction grows strong, e.g. the
salmon, sturgeon, the shads and the mayfish of the
Rhine.

Few fishes are katadromous, i.e. their usual
habitat is in rivers and lakes, whence they descend
into the deep sea for breeding purposes. The com-
mon eel is the classical example.

CHAPTER IV

NUMBERS AND DENSITY OF SPECIES

EVERYBODY knows that some kinds of animals
are common and others are rare. Why this should be
so is easy to understand when the rare species has a
very limited distribution, but there are also birds and

70 THE WANDERINGS OF ANIMALS [OH.

beasts and others which have an almost world-wide
range and yet are much more scarce than their
nearest allies. For instance, ravens compared with
crows. Some kinds exist in literally countless mil-
lions, others perhaps only in thousands. About these
numbers of individuals we know nothing ; the only
species of which a rough census has been made is
man. But for some conspicuous animals we can at
least calculate a rough upper limit. It is unlikely
that there exist, or have ever existed, more than
one million lions in the whole of Africa, because we
can construct their annual food-bill, etc. and thus
narrow the probabilities. The existing stock of
orang utans in Borneo has been guessed at 50,000.
Countless species have died out whilst others
have come on, a process which is still at work, but
from a broad point of view (omitting local fluctua-
tions) the general impression of a fauna is that the
relative and actual numbers of the individuals hold
their own, that there is neither an undue increase
nor a marked decrease. How this balance of nature
works is in well-nigh every case an absolute mystery.
This is due to our ignorance of the economics, the
complex correlations, of every animal and plant.
We do not know them of ourselves. Every kind of
animal, living under favourable conditions (and
nearly all live only where they find such), would
in the natural course of events increase its numbers

iv] NUMBERS AND DENSITY OF SPECIES 71

by leaps and bounds and the whole habitable world
would soon be choked. We do not know the factors
which keep down the numbers of such powerful and
sagacious birds as macaws. The osprey is one of
the most cosmopolitan birds of prey ; it is stronger
than most other fish-eating birds, and there are surely
enough fish in the rivers and lakes for more osprey s,
yet they are nowhere common.

We know that over-crowding, over-population of
a district, engenders diseases, or rather let us say
that these diseases are always present somewhere,
comparatively harmless if kept going by a chance
victim, but that they spread in a crowd. If a species
has become so numerous that there is practically
contact between its members throughout its range,
the whole may be carried off. Only those which
happen to live in some isolated district, cut oif by
chance, will be saved and, like the animals disembarking
from the Ark, start afresh. The degree of the density
of population necessary to produce this 'contact' we
do not know. Countries with locusts and Bombycidae
or spinning moths are also inhabited by ichneumon
wasps. They balance each other, but when there
occurs one of the great irruptions into the North
German pine forests by the moth Gastropacha pini,
the caterpillars of which then devastate whole forests,
in the second or third year the ichneumons have also
become so abundant that every caterpillar is attacked

72 THE WANDERINGS OF ANIMALS [OH.

by them and dies. The plague has wrought its own
remedy.

Now let us consider man. With the present rate
of British increase (an annual gain of 14 per 1000)
the population doubles itself in about 50 years. If
we apply this rate, which is not at all excessive, to
the present 1600 million people of the whole world,
there would be, 1000 years hence, a total population
of 1660 million millions ; and the whole land surface
of the globe would not afford sufficient standing
room for this number of people.

If we apply the same rate backwards, we find that
five people, starting 400 Anno Domini, would have
been sufficient to produce the present world's popu-
lation. So far as actual conditions are concerned
this is pure nonsense, but let us consider that :

1. A population cannot hold its own unless every
potential couple is some day supplanted by another.

2. A population cannot increase, unless, on the
average, there are more than two children, not only
born, but brought up to propagate the race.

3. It is absolutely certain that the origin of man,
as such, dates back into the Pliocene, a time of which
300,000 years would be a conservative estimate, and
for argument's sake representing 10,000 generations
of mankind.

p

4. If we assume that the human race started
as the traditional Adam and Eve pair, within the

iv] NUMBERS AND DENSITY OF SPECIES 73

Pliocene, the rate of increase necessary to account for
the present total population would be so small as
to render the calculation quite preposterous. The
necessary gain would be 1000 : 1002 per generation ;
2 per 1000 people every 30 years, instead of 14 per
1000 annually as is now the case in England. This
implies that of all the thousands of children born to
500 couples during 30 years only two survived to add
to the race. This being an unthinkable state of
affairs, it follows that the rate of propagation has
been always as large as it is now all over the world,
but over and over again whole tribes have been well-
nigh wiped out, by each other, by epidemics or by
accidents. Just like the Red Indians of North
America, who, instead of well filling that large con-
tinent, have reasonably been computed never to have
amounted to more than a few hundred thousand
souls.

What constitutes a rich or a poor fauna? The
number of species and the number of the greater
groups, or variety of types, to which the species
belong. For instance, the mammalian fauna of Aus-
tralia cannot be called rich, since it consists mainly of
the variations of one type only, that of marsupials.

The tropical belt of the world is teeming with
a great variety of terrestrial life, while the number
of species decreases to almost nought towards the
poles. The arctic and antarctic regions are so poor

74 THE WANDERINGS OF ANIMALS [CH.

in permanently resident species, and devoid of Am-
phibia, reptiles and freshwater fishes, that they may
be left out of a census of the world's ' terrestrial in-
habitants' if we want to compare the various land
complexes as to the richness of their faunas. To
illustrate shortly the principle involved, we must
further restrict ourselves to the number of species.
The bulk of generally habitable land may be reduced
to the conveniently round number of 40 million square
miles.

The vertebrate fauna, omitting strictly marine
fishes, may be stated in the following conservative
numbers of species : freshwater fishes, 6000 ; Am-
phibia, 1000 ; reptiles, 3500 ; mammals, 2500 ; birds,
12,000. Total, 25,000 species.

This gives on an average one species to every
1600 square miles, and this may be called the areal
density of the world's vertebrates.

The areal density is expressed by the quotient of
the number of species of a country into the area in
square miles. The quotient, therefore, expresses the
specific areal density in an inverse ratio. The richer
the country, or the greater its number of species, the
smaller is the index figure. Examples :

iv] NUMBERS AND DENSITY OF SPECIES 75

In thousands Numb.

of of Areal

square miles, species. density. Group of animals.

Total habitable land 40,000 25,000 1600 All vertebrates

„ ,, ., ,, 4500 8888 Amphibia & reptiles

„ ,, 12,000 3333 Birds

2500 16,000 Mammals

„ ,, ,, ,, 6000 6666 Freshwater fish

British India 1678 1630 1000 Birds

„ „ 666 2520 Amphibia & reptiles

Rich and poor are arbitrary conceptions. More-
over a country may be rich in birds and poor in some
other class. We may, however, fairly assume that,
class for class, an index below the world's average
means a decidedly poor fauna, and an index double
that of the world means a rich fauna. The reptilian
fauna of India is as notoriously rich as that of North
America is poor, and that of Europe is still poorer.
The bird faunas of South America and India are twice
or even three times as rich as those of Europe. Such
calculations yield valuable results, sometimes so start-
ling that the underlying causes have to be inquired
into, which then occasionally reveal unexpected cor-
relations.

76 THE WANDERINGS OF ANIMALS [CH.

CHAPTER V

FORMER CONFIGURATIONS OF LAND AND WATER

IN the majority of cases the present distribution
of animals cannot be accounted for without the as-
sumption of enormous changes in the configuration
of land and water. It is no explanation to say that
most groups had a ' universal or sub-universal range '
and that their now discontinuous occurrence is simply
the result of their members having died out in the
intervening countries owing to unsuitable environ-
mental changes. Of course that has often happened,
but the sub-universalists avoid the question how the
world-wide range had been attained. Further, to
account for the undeniable affinity between the South
American and African faunas, some writers, instead
of admitting a direct land-connexion, rather resort to
a roundabout journey from America by Behring's
Strait through Asia to West Africa, assuming further
that all along this route the respective animals have
since died out. If this is supported by fossils, well
and good. Cases of such a roundabout spreading
are known. We dismiss the many, well-ascertained
instances of occasional dispersal (by the proverbial
floating log, currents, storms and water-spouts) as
insignificant, and quite inapplicable to most creatures.

v] ANCIENT GEOGRAPHY 77

Land tortoises (genus Testudo\ have reached the
Galapagos by land, not astride a log, just as certain
as lemurs in Madagascar and elephant remains in
the Andes are evidence of former land-connexions.
Oceanic islands have at best a scanty terrestrial fauna,
but it is a mistake to refer this entirely to accidental
spreading. It would first have to be shown whether
these islands arose out of the ocean, or whether they
are remnants of sunken continents. If Africa sub-
sided two miles there would remain a few isolated
volcanic peaks, like Cameroon and Kenia, with all
the appearance of oceanic islands, but with a derelict
indigenous fauna. It depends upon the age of such
islands, whether they could have only reptiles, or also
mammals, and even then absence of, say, mammals
on the Galapagos proves but little since so much
depends upon the physical conditions of the land
(cf. p. 59).

Of course enormous subsidences and elevations of
extensive areas are required, although many authori-
ties shrink from their application. The permanence
of the great ocean basins had become a dogma since
it was found that a universal elevation of the land to
the extent of 100 fathoms would produce but little
changes, and when it was shown that even the 1000
fathom-line followed the great masses of land rather
closely, and still leaving the great basins, by general
consent this quite arbitrary unit of about one mile

78 THE WANDERINGS OF ANIMALS [OH.

was allowed as the utmost speculative limit of sub-
sidence. Two or three miles, the average depth of
the oceans, seems enormous, and yet it is as nothing
in comparison with the size of the earth. On a clay
model globe ten feet in diameter the highest moun-
tains would be smaller than the unavoidable grains
in the glazed surface of our model. There are but
few countries which have not been submerged at
some time or other, and most of the great chains of
mountains, Andes, Rockies, Pyrenees, Alps, Himalayas,
are only of Tertiary date.

Many attempts have been made to construct maps
purporting to show the configuration of laud and
water at various epochs. Although the results by no
means tally with each other, owing to the lamentable
deficiencies of geological and fossil data, the hypo-
thetical results are sure to be corrective and supple-
mentary ; the problems will be solved, since they are
not imaginary. The bolder the outlines are drawn, the
better, whilst the insertion of detail and the clinging
to present coasts give such maps a fallacious look
of certainty. Further, when we draw a broad belt of
land across an ocean, this belt need never have
existed in its entirety at any one time. The features
of dispersal intended to be explained by it, would be
accomplished just as well by an unknown number
of islands which have joined here, whilst others have
subsided elsewhere ; like a pontoon-bridge which may

v] ANCIENT GEOGRAPHY 79

be opened anywhere. Lastly, just as it is impossible
to make a political world-map of, say, the 19th century,
it is futile to chart a geological epoch. We might as
well attempt to fit in one picture a series of super-
imposed dissolving views.

The evidence for reconstructions is direct and
circumstantial. Marine fossils indicate sea, terrestrial
fossils land at the respective time. In North America
occurred a void gap of land-vertebrates during the
Jurassic epoch, but towards its close came in a rich
fauna of Dinosaurs, tortoises and mammals of sorts
known to have existed long before in Europe.
Between Alaska and Canada came in the most
specialised Ichthyosaurs and Plesiosaurs, closely re-
lated to those of the European seas, showing that
there must have existed seaway from Europe to the
north of Greenland, whilst Canada-Greenland-Europe
formed a barrier to marines but a bridge to terrestrials.
Then, during the upper Cretaceous North America
was severed into an eastern and a western half, so that
the gulf-fauna could mix with another from the polar
sea.

There is obvious affinity between the faunas of
South America and Africa, besides groups which
probably have got there from a common North
American-European centre. Some of the circum-
stantial evidence for a direct South American- African
connexion is as follows :

80 THE WANDERINGS OF ANIMALS [CH.

Close affinity between fossil corals of the Antilles
and North- West Africa suggests a coast, at least
a shallow Atlantic sea. There is no affinity between
the marine shells of Argentina and those of the
Antilles ; this suggests land between Brazil and Africa
as an effective barrier, which in turn would account
for affinities of the terrestrial faunas. Most authorities
agree as to the existence of such a * bridge ' during
Mesozoic times, the only question is whether it lasted
long enough into the Tertiary to be available for
certain groups which have not yet been traced back
further than the Oligocene. Evidence is, however,
rapidly accumulating that not only families but even
many genera are much older than have been supposed.

Instead of maps the schemes of diagrams intro-
duced on pages 84, 85 may serve to indicate in the
most condensed style the hypothetical configurations
in successive geological epochs.

Straight lines mean continuity of land ; dotted
lines show transient connexion ; parallel lines indicate
separation by sea. The position of the present con-
tinents, etc. is expressed by their initials. Want of
space forbids any attempt to justify these broad
suggestions, but the chapter dealing with the present
and past range of selected groups of animals will
supply a considerable number of test cases.

In its broadest outlines the history of the lands
and seas since the Carboniferous period may be read

v] ANCIENT GEOGRAPHY 81

as follows. There were two huge masses of land, a
high Southland extending from South America across
Ethiopia and India to Australia, and a low North-
land comprising Canada, Greenland, Scandinavia and
Siberia. These two lands were separated by a broad
Mediterranean sea, an east and west extension of the
Pacific basin. Nothing is known about the antarctic
regions. Two new features are indicated in Carbo-
Permian times ; joining of the north- and southland
somewhere between South-East Europe and Africa,
perhaps by emergence of South-West Asia ; isolation
of North America with Greenland from the Europe-
Siberian mass during the whole of the Permian.
With the Trias this connexion is restored, but towards
the close of this epoch Siberia becomes isolated, the
European sea communicating with the Pacific to the
north of India ; another lower Triassic land con-
nexion of Western, Atlantic, Europe, with North- West
Africa is also lost. With the later Jurassic a com-
plete rearrangement has taken place. There are
three separate masses of land : a northern Atlantic
land, namely North America with North Europe ;
a Siberian-East Asia-Australian mass, and a so-called
Gondwanaland proper, namely South America with
Africa-Madagascar and India. The old Southland has
been severed in two. Great changes have been effected
during the Cretaceous, at least they become now
for the first time discernible : connexion of WTestern
G. 6

82 THE WANDERINGS OF ANIMALS [CH.

North America with a Western South America, con-
tinued across the Antarctic to Australia which is still
joined to Eastern Asia and Siberia, the latter con-
tinuous with North America but separated from
Europe. Consequently an enormous ring of land
encircles Gondwanaland which, it must be noted, is
quite separated. During the Upper Cretaceous,
Siberia joins Europe and Canada, but North America
is divided into an east and west. Severance of Chile-
Patagonia from the rest of now consolidated South
America. Severance of Australia from Asia. Conse-
quently there is now a greater antarctic complex,
from Chile to Australia, whilst the rest of the world
forms a huge ring with a gap through North America.
During the earlier half of the Tertiary epoch the
North American, European and Siberian lands sepa-
rate and rejoin variously, continuous perhaps across
the polar sea, sometimes transversely. Antarctica
separates from America and from Australia. Gond-
wanaland breaks up. India becomes for a while an
island. Ethiopia becomes isolated owing to the
Mediterranean joining the Indian Ocean, and on
the other side joining the South Atlantic, thereby
severing Ethiopia from South America, which how-
ever still remains connected with North- West Africa.
Next the African continent is consolidated ; the
North and South Atlantic Oceans become confluent
and South America is isolated. During the Miocene

v] ANCIENT GEOGRAPHY 83

only Australia, New Zealand and Madagascar are
isolated entities of importance. All the rest of the
world is at some time or other in roundabout, or
direct, continuity, chiefly owing to the juncture of
Africa by Arabia with India and the long-since con-
solidated Asia ; the two Americas are joined, for
a time also the Antilles. Since the Pliocene they
remained islands. North America finally separates by
the North Atlantic from Europe, but is variously
connected with Siberia across Behring's Straits.

The most changeable of all regions was Europe,
not because it is geologically the best known, but it
is the newest continent. During Cretaceous and far
into Tertiary times Northern and Western Europe
formed an extension of the Canada-Greenland mass,
quite separate from Asia ; Central and South Europe
consisted mainly of a variable number of much-

*/

changing island complexes. With the Miocene sepa-
ration from Greenland took place and joining of the
growing Europe to Siberia and South- West Asia,
and the central and southern islands became ab-
sorbed into the continent in the Pliocene. During
Pleistocene times Europe seems to have attained its
greatest dimensions, and with the receding ice the
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86 THE WANDERINGS OF ANIMALS [OH.

PROBABLE AGE OF CERTAIN ISLANDS.

Great Britain became an island after the last
glacial epoch. Ireland separated a little earlier ; its
latest connexion was with Scotland, whence it was
re-stocked after the glaciation, with the possible ex-
ception of those few plants and animals which had not
been affected by the ice in the most southern part.

Iceland, Faroer and Greenland date from the
Pliocene. Iceland's fauna was destroyed by Pliocene
lavas. Its separation from Greenland preceded that
from the Shetlands.

Corsica and Sardinia were connected with Northern
Italy well into the Pliocene ; Sicily also with Africa.
The latter was repeatedly in contact with Europe
during the Tertiary period, especially across the
Aegean Sea. Crete for instance is but of Pliocene
date. Communication of the Mediterranean with
the Atlantic has been interrupted more than once,
not always at the present Straits of Gibraltar, which
are of rather recent date.

Newfoundland was last connected with Labrador,
whence it was re-stocked after the glaciation. The
Greater Antilles became severed from Central America
and from each other within the Pliocene, when they
underwent considerable submergence. The Galapagos
date from the same epoch.

vi] DISTRIBUTION OF SELECTED GROUPS 87

During the Jurassic, Cretaceous and early Ter-
tiary Madagascar, together with India, formed a long
island, or complex of islands (practically the much
debated ' Lemuria ' of Sclater and Haeckel). Mada-
gascar was separated from Africa since the Lias,
with a rather problematic restoration of an Oligocene
bridge. The connexion with India lasted well into
the Oligocene.

Sumatra, Java and Borneo were Asiatic continental
until the Pleistocene ; Celebes and the Philippines
until the Pliocene ; whilst New Guinea and Tasmania
were Australian. New Zealand, as a whole, seems
to be the earliest island-complex of importance. Its
final separation, however, need not date back further
than into mid-Cretaceous times.

CHAPTER VI

DISTRIBUTION OF SELECTED GROUPS
EARTHWORMS.

THE terrestrial earthworms have the reputation
of great zoo-geographical importance, and in the
hands of an expert, unbiassed in the interpretation of
the actual facts, they may some day yield valuable
results which are in harmony with those indicated

88 THE WANDERINGS OF ANIMALS [CH.

by other groups of animals. Unfortunately there
are no fossil data. The following points are in favour
of the importance of earthworms : they are in their
welfare and possibility of spreading dependent upon
the existence of vegetable mould ; they cannot stand
sea-water, and their mode of dispersal depends
entirely upon their own powers of locomotion, which
are considerable; accidental, occasional lifts of the
worms, or of their cocoons, are practically excluded,
except by human agency since prehistoric times.
There are for instance in the Sandwich Islands more
than a dozen kinds of earthworms, of genera, which
are not restricted to these islands. On the contrary,
some of them have a very wide distribution. Conse-
quently these worms must have come from elsewhere,
and speaking geologically, not so very long ago.

A very different case is presented by various
Antarctic islands, e.g. Kerguelen and Marion to the
south-east of the Cape. Their characteristic worms
belong to the presumably ancient Acanthodrile group,
and are, according to Beddard and Michaelson, quite
indigenous, since they are all different as species and
found nowhere else. The further contention that these
islands are not truly oceanic but the remnants of
a former much larger mass of land may also be valid,
but it does not follow that this land was part of
a former northern extension of the Antarctic con-
tinent. Like the fish-genus GalcLxias (cf. p. 95)

vi] DISTRIBUTION OF SELECTED GROUPS 89

these worms would prove rather too much, because
other allied species and genera of Acanthodriles live
in Cape Colony.

The present distribution of this important family
reaches from South America, over Africa and Mada-
gascar, to New Caledonia and New Zealand, with
this restriction that in Patagonia, the Falklands, New
Georgia, Kerguelen and Marion Islands, they form
almost the only worm-fauna, whilst they are in the
minority in the more temperate and tropical parts
of the southern continents. Their distribution is
therefore compatible with that of the ancient Gond-
wanaland, and this would not have prevented them
from availing themselves also of the Patagonian-
Antarctic-Australian bridges.

The other main groups of earthworms strongly
indicate a South American + African + Madagascar
complex and an Oriental-Australian community,
Avhilst the Lumbricidae (supposed to be the youngest
family) are with few exceptions the only earthworms
of Eurasia proper whence, however, they have spread
over most of the world. The Pleistocene glaciation
seems to have played sad havoc with the worms of
North America since Canada and the Northern States
possess no indigenous species, all the earthworms
being identical with European species. But those in
the Southern States show a marked influence from
Central America.

90 THE WANDERINGS OF ANIMALS [CH.

PERIPATUS.

Peripatus is the sole surviving genus of the
Protracheata. The group, ancestral to spiders and
insects, must be of enormous age, but this genus need
not date further back than into the Cretaceous to
allow us to account for the scattered distribution of
its species as follows : the occurrence of the same
species in Australia, including Tasmania, suggests this
region as the original centre, whence other species
spread into New Britain and Indo-Malaya. Then ex-
tension across Antarctica by Patagonia to Chile,
whence into the rest of South America (Guiana) as
this became consolidated in Tertiary times. For
getting to the West Indies and into Mexico they
would have had to wait until the Miocene, but long
before that time they could arrive in Africa, there
surviving as a Congolese and a Cape species ; but
they never reached Madagascar.

INSECTS.

The genus Carabus, flightless beetles, lives to the
north of about the 30th parallel in both hemispheres
and reappears in Chile : by no means a solitary in-
stance of such a discontinuity in America, e.g. bears.

vi] DISTRIBUTION OF SELECTED GROUPS 91

MOLLUSCS.

Of bivalves only the Unionidae and Cydadidae
are freshwater families, both with world-wide range.
Of the marine Mytilidae, Dreyssena polymorpha is
the only freshwater species. Its home is the Volga
basin, whence it became accidentally introduced into
Western Europe in the 18th century. It is now in
the interesting stage of spreading through all rivers
and even into land-locked lakes. Those which ascend
the Danube basin are meeting others from the Rhine
which they have reached by Baltic shipping.

The true mother-of-pearl, genus Meleagrina,
ranges from the coast of Persia to Celebes and
Melanesia, reappearing on both coasts of Mexico
and Central America.

FRESHWATER CRABS AND CRAYFISHES.

The freshwater Decapods have been studied
exhaustively by Ortmann, who in a classical paper
has based upon their distribution the most suggestive
reconstructions of Cretaceous and Tertiary geography.

Crayfishes are older than crabs, and they can
inhabit cold regions, whilst the crabs are essentially
tropical. The crabs comprise (1) the Potamoninae
in Africa and Madagascar, India and China, Malay
and Papuasian islands ; with their northern limit
South Japan, Asia Minor, Greece and South Italy ;

92 THE WANDERINGS OF ANIMALS [CH.

(2) the Deckeniae in East Africa and one species on
the Seychelles ; (3) the Potamocarcinae in tropical
America, including Antilles. Thus they occupy the
whole intertropical belt and this divides the cray-
fishes into the northern Potamobiidae and the
southern Parastacidae. Only in a few countries
do crabs and crayfishes slightly overlap, e.g. South
Mexico and Papua. Crabs are destructive to the
crayfishes, so that the latter cannot enter countries
already tenanted by the former. Crayfishes are
assumed to have originated during the Cretaceous
in Southern Asia, where they no longer exist.

Their southern descendants, the Parastacidae,
survive in New Zealand, Fiji, Melanesia, New Guinea,
Australia and Tasmania, whence they crossed by
Antarctica into the southern temperate part of South
America. There is also one solitary form, Astacoides
madagascariensis, in Madagascar.

The northern descendants of the ancient cray-
fishes are the Potamobiidae, comprising only three
genera. Astacus (e.g. the common crayfish, renamed
Potamobius by purists) in Europe and Western
Siberia, and in the North-West United States. The
discontinuous range is mitigated by a few species in
the Amur, Korea and North Japan, where they form
the sub-genus Cambaroides. Lastly Cambarus, to
which Astacus is directly ancestral, in the eastern
half of North America, Mexico and Cuba.

vi] DISTRIBUTION OF SELECTED GROUPS 93

SCORPIONS.

This group is a good illustration of the effect of
great antiquity. Scorpions already existed in the
Silurian, and even some existing species date back
to the Coal-measures ! They have had every chance
of spreading widely. A species of Tityus is preserved
in Miocene amber of the Baltic ; this genus is now
restricted to southern South America. The group
is cosmopolitan, limited only by cold, yet it is absent
from New Zealand. They show scarcely any generic
affinity between the Old World and the New, nor
between South America and Australia. They have
had sufficient time to develop along lines aloof from
each other in these great land complexes.

FISHES.

Eels are cosmopolitan ; those which live in rivers
must descend into deep seas to breed. For some
reason the Black Sea is a closed sea to eels, conse-
quently there are none in that large part of Middle
and Eastern Europe which drains into this sea. Nor
are there any in the Volga basin, although this con-
tains a sturgeon.

Pikes (Esocidae), a small well-defined family of
freshwater fishes, with only two genera. Esox occurs
first in European Oligocene. E. Indus, the common
pike, inhabits Europe, excluding Spain, Siberia and a

94 THE WANDERINGS OF ANIMALS [CH.

broad belt across temperate and cold North America,
with several other species ill the north-east. The
other genus is Umbra, with one species in Hungary,
the other in North-East America.

CiMidae, a numerous family of freshwater fishes,
Avith many kinds in tropical America and the whole
of Africa, with Madagascar, and only three species in
South India and Ceylon.

Characinidae, an ancient freshwater family, with
many species in tropical America, excluding Antilles,
and tropical Africa including the whole Nile, but
excluding Madagascar for which they were too late
in their progress from America through Africa.

Cyprmidae : carp, minnow, tench, bream, barbel,
etc. ; the majority of the freshwater fishes of the
northern hemisphere. The distribution of the family
is most important, namely over the whole of Arcto-
gaea; absent from South America, Madagascar,
Australia, New Guinea and New Zealand. According
to Boulenger the Cyprinids originated from the Chara-
cinids as a northern offshoot in North American
Eocene, whence they spread into Eurasia at least
during the Upper Eocene ; with the Miocene they
reached India and then Africa, checking thereby the
eastward spreading of their older cousins, the Chara-
cinids. This assumed spreading from North America
by Asia to India and Africa is an example which is
applicable also to other orders and classes of animals.

vi] DISTRIBUTION OF SELECTED GROUPS 95

Galaxiidae, a small freshwater family of trout-
and pike-like appearance. Galaxias, the main genus,
has become famous as one of the earliest and chief
supports of the former connexion of Australia with
South America. The same species, G. attemtatns,
inhabits the streams of New Zealand, Tasmania,
South Australia, the Falklands, South Patagonia and
Chile ; others occur at the southern end of America,
in Southern Australia, New Zealand and neighbouring
islands, and one at the Cape. One species (Chatham
islands), is said to be marine. The existence of a
species at the Cape would prove rather too much
for connexion vid Arctica, but, although it is not
impossible that these fishes are the remains of a
family which inhabited the southern shores of the

V

Great Gondwanaland, it is scarcely credible that
a species like G. attenuatns should have survived
since at least the Eocene.

AMPHIBIANS.

Amphibians cannot endure saltwater, nor can
they spread across deserts. Most abundant in the
tropics, they decrease rapidly towards the arctic
circle, their northern limit following roughly the
58th parallel in Eurasia and the 50th in America.

The tailed amphibians, Urodela, are essentially
holarctic, with three main centres, European, Eastern

96 THE WANDERINGS OF ANIMALS [OH.

Asiatic and North American with closest affinity
between the two last. North America contains the
greatest number of diverse forms, including members
of every sub-family, Plethodonts being the most
numerous. Asia is richest in Amblystomatinae ;
Europe is characterised by tritons and salamanders.
Significant is the occurrence of Cryptobrcmchus, the
'Giant Salamander,' in Japan, Manchuria, Eastern
U.S.A. and fossil in European Miocene, and with
close relations in the Oligocene. One kind of Ambly-
stoma lives in China, all the other species of this
genus in North America, e.g. A. tigrimmi, which in
certain Mexican lakes breeds as the famous axolotl.
The Plethodont genus Spelerpes has many species in
America, from Canada to South America, including
Antilles, and one solitary species in the Riviera and
in Corsica ! The nearest relation of the blind Proteus
in caves of Istria is the Necturus of the American
lakes. In the Old World the southern progress of
newts has been barred by the great belt of deserts
and the Mediterranean, there being none in Africa
and India, but many in China, whence at least one
has extended into Siam and Burmah. The oldest
Urodela occur in the Belgian Wealden, related to the
American mud-eel, Amphiuma.

The tailless amphibians, Anura, are quite cosmo-
politan. Their oldest remains are scanty, from the
Upper Jurassic of Wyoming and Spain. With the

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vi] DISTRIBUTION OF SELECTED GROUPS 97

early Miocene most of the chief families seem to
have been already developed. Unfortunately our
knowledge of their pedigrees is still very deficient.
It is for instance at least doubtful whether the
'Firmisternia' (Ranidae + Engystomatidae + Dysco-
phidae) form a natural division. Only the more
significant cases of distribution can be mentioned.
The most archaic but also most specialised are the
Aylossa, namely Pipa, the 'Surinam toad/ mainly
Brazilian, Xenopus in Africa, and Hymenochirus,
intermediate in structure, in the Congo district.

The Discoglossitlae also are ancient, with a very
scattered range, namely the 'fire-bellies/ Bombinaior,
from France to Manchuria, the 'midwife toad,' Alytes,
IHscoglossiis in West Europe, and Ascaphus in North-
West United States. The equally ancient Pelobatidae
or 'spade-foots' and allies range from North America,
Europe and India into Papuasia.

Bufonidae, typical ' toads,1 are cosmopolitan, ex-
cepting Madagascar, New Guinea, Tasmania and New
Zealand. The genus Bufo has the same wide range,
but is also absent from Australia. The centre of the
Hylidae or 'tree-frogs' is South America, whence
they have spread, since the Miocene, to the Antilles
and Central America, and in ever decreasing numbers
into North America, and only two or three closely
allied species occur in Eurasia, from Japan to the
Himalayas and to western Europe, excluding Britain.

G.

98 THE WANDERINGS OF ANIMALS [OH.

No Hylidae exist in Africa and Madagascar nor India
and the Malay Islands, but there are plenty in Aus-
tralia. The same principle, suggestive of a former
antarctic connexion, is followed by the Cystigna-
thidae, which are plentiful in South and Central
America (a few in the U.S.A.) and Australia, and the
solitary Liopelma in New Zealand.

The opposite principle of dispersal applies to the
Ramdae or typical frogs. The greatest number of
their many genera with near 300 species occurs in
Africa and the Indo-Malayan countries. All the
numerous species of the whole of North America
and Eurasia belong to the genus Rana, except the
closely allied arborealised Rhacopliorm which ranges
from Japan through India and Malaya ('flying frog')
to Madagascar. Rana itself, with about 150 species,
has nearly the same range as the family, and, what is
most significant, a few species have reached north-
west South America, but not the Antilles ; it occurs
also in Madagascar, New Guinea, Northern Australia
and the Solomon Islands. Thus the frogs, toads and
tree-frogs still proclaim the fundamental divisions of
the Old South and North World.

CROCODILES.

Crocodiles in a wide sense are known from the
Lower Jurassic epoch and they developed an abun-
dance of marine and freshwater groups all over the

vi] DISTRIBUTION OF SELECTED GROUPS 99

world, of which the present 20 species are the scanty
remainder. Long-snouted gavials occur in the Upper
Cretaceous of New Jersey and Europe, in the Mio-
cene of Europe, now restricted mainly to the Ganges
and Malay Islands. Crocodiles have lived in Europe
since the Upper Chalk, and many kinds flourished
there, and in North America during Tertiary times ;
now in Africa, India to North Australia, and in
tropical America, including the West Indies. Alli-
gators and caimans, formerly also in England, are
now almost entirely American, but one species lives
in the Yang-tse-kiang as a reminder of the probable
Eurasian origin of the whole group.

TORTOISES.

The marine turtles are found in all the warm to
temperate seas. Most of the groups of the land
and freshwater tortoises were evolved before the
Tertiary period, and attained a perhaps world-wide
range, so that the present distribution of the 200
species represents only the remainder of a sub-class
which has had its day.

Pleurodira, or water-tortoises, which tuck away
their long neck sideways, were plentiful in Mesozoic
times in Europe, India and North America ; now re-
stricted to Africa and Madagascar, South America
and Australia. On the latter continent they are the

7—2

100 THE WANDERINGS OF ANIMALS [CH.

only tortoises, family Chelydidae, which flourish
also in South America, e.g. Matamata. The other
family, Pelomedusidae, is Afro- American ; of these
Podocnemis, now in Madagascar and Brazil, occurs
in early Tertiary of Egypt and Angola. The Crypto-
dira, tortoises which draw in the neck straight, are
most developed in North America. The genus Tes-
tudo, the most typical land tortoises, ranges over
the world, excepting the Australian quarter, and is
limited northwards only by the cooler climate. Its
earliest occurrence is in the mid-Eocene of Wyoming,
since the Oligocene in Europe, still later in India,
where in Pliocene times it attained truly gigantic
size (T. atlas). Somewhat smaller kinds lived in
Miocene Europe and North America, now restricted
to some of the islands near Madagascar, and to the
Galapagos, i.e. 'Turtle-islands/ Of course this implies
former land connexions. And so does Miolania, the
most aberrant of all tortoises, known from the
Pleistocene of Queensland, Lord Howe's Island and
Argentina. Trionychidae, river or 'mud-turtles,'
with a much-reduced, leather-covered shell, since the
Cretaceous in North America, in early and mid-
Tertiary of Europe, now in North America, Southern
Asia and the African continent.

vi] DISTRIBUTION OF SELECTED GROUPS 101

*

LIZARDS.

Geckos, probably the oldest family, are found in
all warm countries and islands, even in New Zealand
and the Sandwich Islands, being particularly fit for
accidental transport. Equally cosmopolitan are the
also very ancient Skiuks.

The following families are restricted to the Old
World : (1) Chameleons in Africa and Madagascar,
and a few in Syria and Arabia, South India and
Ceylon ; (2 and 3) Agamas and Varans or * Monitors,'
in the whole of Africa, Asia Minor to China and to
Tasmania ; absent from New Zealand and Mada-
gascar ; (4) Lacertidae or lizards proper, in Africa,
Europe, Asia; absent from Madagascar and Austra-
lasia.

The following occur in both the Old and the New
World : (1) Amphisbaenas, burrowing, worm-shaped;
in the warmer parts of America, including Antilles ;
the whole of continental Africa and Mediterranean
countries, like Spain, Sardinia, Corsica, Cyprus and
Asia Minor, a strong indication of Tertiary Afro-
American connexion. (2) Slow- worms or Anguidae;
centre of dispersal probably middle America, the home
of the limbed genera, now extending to Vancouver
and to Costa Rica and the Antilles. The only kinds
in the Old World are limbless : the slow- worm, Anguis
fragilis, is European ; of the glass-snakes, Ophisanrus,

102 THE WANDERINGS OF ANIMALS [ctt.

one occurs from Marocco to the Caspian, another
from Himalayas to China, the third in the United
States. (3) Iguanidae or iguanas, basiliscs and
' horned toads.' Essentially American, with the re-
markable occurrence of two genera in Madagascar
and one in the Fiji and Friendly Islands. Mada-
gascar presents no difficulty, since iguanas are known
from French and English Eocene, and their total
absence from Africa and India may be accounted for
by the inroad of the fierce carnivorous Varans, which,
too late for Madagascar, exterminated the chiefly
herbivorous iguanas. The Fijian Brachyloplms re-
mains a puzzle, but on the Galapagos, nearly 600
miles from America, live two kinds of antediluvian-
looking Iguanids, one of which, Amblyrhynchus, is
semi-marine, feeding upon algae.

Strictly American are the families of Teijus and
Ameivas.

SNAKES.

The earliest remains date from the Lower Eocene
of Egypt, amongst them gigantic forms allied to
boas or pythons which are still found in all tropical
countries. The majority of the snakes belong to the
cosmopolitan Colubridae, which seem to have given
rise in divergent directions to the poisonous Elapinae
and to the equally poisonous Viperidae ; the latter
are naturally divided into vipers and pit- vipers. The

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vi] DISTRIBUTION OF SELECTED GROUPS 103

poison snakes are of considerable geographical im-
portance.

Australia lias only Elapines, but in abundance.
America has Crotalines and Elaps. Africa has hooded
Elapines and abundance of vipers. Europe has now
only vipers, in former epochs also Elapines and
Crotalineg. The Indian countries alone are cursed
with members of all three groups.

Elapinae, culminating in the hooded cobras, genus
Naja, which ranges all through continental Africa
and the whole of temperate and warm Asia. Other
genera in India and thence in Australasia down to
Tasmania, America has received, or developed, only
the genus Elaps with many species from the States
to Patagonia ; none in the Antilles.

Crotalinae or Pit-vipers in the southern half of
Asia, from Asia Minor to Borneo and Japan and
throughout North and South America. Both the
chief genera Lachesis and Andstrodon exist in the
Old and New World. A further modification of
pit-vipers are the rattlesnakes proper, with present
headquarters in the South- Western States and Mexico,
whilst only one species, Crotalus terrificns, has entered
South America, now ranging from Arizona to Argen-
tina.

Viperinae, vipers without a sensory pit between
nose and eye, all over Eurasia and Africa, respecting
Wallace's line like the hooded cobras. The efficiency

104 THE WANDERINGS OF ANIMALS [OH.

of this line (between Borneo and Celebes, Java and
Lombok), and their absence from North America,
point them out as the most recently evolved group of
poisonous snakes. The original centre of them all
seems to have been Eastern Asia, and the dispersal
had taken place with the Miocene.

BIRDS.

" Ratitae ' are not a natural group ; they are
related to each other only in so far as that they are
the flightless descendants of that stock of terrestrial
birds which has given rise to the Tinamoos, Cranes
and Fowls. Since the early Tertiary, Ratitae have
arisen at different times and in various countries,
independently of each other. Many are now extinct.
Rhea lives in South America. Struthio, the ostrich,
now in Africa and Arabia ; known from Pliocene
of Samos, North -West India and Northern Asia.
Cassowaries chiefly in Papuasia, emus in Australia.
Aepyornis in Madagascar, where extinguished possibly
by man ; the lRuk' of the fable. New Zealand and
Stewart Island have the kiwis (Apteryx), and there
was an abundance of moas (Dinornis), some of them
gigantic, extinguished by the Maoris.

Penguins are essentially antarctic, also on the
south coasts of New Zealand, Australia, the Cape and
South America, on the west coast of which they

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vi] DISTRIBUTION OF SELECTED GROUPS 105

extend northwards with the cold Humboldt current,
which may account for their existence on the Gala-
pagos, right under the equator. Fossil penguins are
known from the Oligoceue of New Zealand and
Miocene of Patagonia.

Divers and Grebes. Divers (Colymbus) and
Grebes (Podicipes) seem to be connected by the
Oligocene French genus Colyniboides. The four kinds
of recent divers are restricted to the northern hemi-
sphere. Grebes.are cosmopolitan, with one interest-
ing flightless kind on Lake Titicaca in Bolivia.

Petrels and Albatrosses are cosmopolitan groups;
albatrosses are, however, more common in the southern
hemisphere.

Gamuts and Cormorants are cosmopolitan,
Pelicans are restricted to the warmer zones. The
largest cormorant happens to be a flightless species
of the Galapagos Islands. Fossil Steganopodes (i.e.
rudder-feet, so called because all these birds have
all the four toes webbed together) are known from
the Oligocene onwards.

Herons are cosmopolitan. The tall Balaeniceps,
whale-headed heron or shoebill of the Upper Nile,
and the small Cancroma or boatbill in tropical

America, are remarkable illustrations of isotelv or

t/

so-called parallel development or convergence.

Storks proper are essentially an Old World family,
namely Indo-African, whence some species migrate

106 THE WANDERINGS OF ANIMALS [OH.

to breed in the northern temperate zone. They are
entirely absent from North America, but South
America possesses one kind of Ciconia, besides the
Jabiru-stork which has its other relations in Africa,
India and Australia. Both marabous and adjutants
are Indo- African.

Flamingoes began to evolve out of stork-like birds
in the Lower Miocene, e.g. Palaelodus of France.
Now they inhabit lagoons and inland lakes of Africa,
Madagascar, India and tropical America, including
the West Indian Islands. The common African species
has summer colonies in Andalusia and near the mouth
of the Rhone.

D-ucks, Swans and Geese are quite cosmopolitan
groups. Spur- winged geese or tree-ducks range from
tropical America, through Africa and Madagascar to
India, but are absent from the Australian countries.

The ancient Palamedeae, crested screamers or
chiijas, are restricted to South America.

Limicolae. Many of the plovers, sandpipers and
so forth, being shore-birds are great migrants and
rather closely allied to each other ; they are more or
less cosmopolitan and do not yield any important
geographical results.

Thick-knees or stone-curlews (Oedicneimis) are
absent from North America, Central Asia and
New Zealand. The ' Painted Snipes ' (Rhynchaea)
range from Africa and Madagascar to Formosa and

vi] DISTRIBUTION OF SELECTED GROUPS 107

Australia and to South America. The Jacanas (Parra,
etc.) have a similar tropical range, excepting Australia.
The ' Seed-snipes ' (Thinocorys] are restricted to
Western South America, from Ecuador to the Falk-
lands. The only other family with a somewhat
restricted range are the Coursers, Pratincoles and
Crab-plovers which inhabit the shores of the whole
Indian ocean, whence they extend far into the Old
World continents.

Gulls and Terns are cosmopolitan families.

Auks and Guillemots are decidedly northern, the
southern limits of these strictly marine shore-birds
being Massachusetts, Brittany, the Baltic, the north
coast of Siberia, North Japan to Lower California.
The famous ' Great Auk/ the only really flightless
member, had been exterminated in Iceland in 1844 ; it
was formerly common on the coasts of Denmark and
Ireland, and on the opposite shores of North America.

Sand-grouse. The genus Pterocles dates from
the early Tertiary of France ; ranging now from Spain
and Cape Colony to Madagascar. Syrrhaptes para-
doxus, Pallas' Sand-grouse, is at home in Central Asia,
whence it has made irruptions in enormous numbers
into Europe ; cf. p. 68.

Pigeons are apparently an Old World group,
dating with certainty from the Lower Miocene ; they
are now quite cosmopolitan. Especially rich in the
production of genera have been tropical islands, above

108 THE WANDERINGS OF ANIMALS [CH.

all Malaya, Papuasia and Polynesia, perhaps, as
Darwin pointed out, owing to the absence of monkeys
and other noxious, egg-stealing mammals. Flightless,
large-sized pigeons were the recently extinguished
Dodo of Mauritius and Bourbon, and the Solitaire
(Pezophaps) of Rodriguez.

Gruiformes or Cranes and Rails are an important
order on account of the distribution of the genera,
some of which are at least of Oligocene date. Taken
as a whole, this order indicates common origin and
descent from an equatorial belt of land when South
America, Africa and India were still more or less
connected ; after this time the development of
entirely Old World families becomes marked.

Rails are cosmopolitan, but interesting because
of the tendency of reduction of their wing power.
Beginning for instance with birds like the Weka
Rails (Ocydromus) of New Zealand, they are liable
to become flightless, with a much-reduced keel of the
breastbone. This has happened, especially on small
islands, e.g. Chatham Island with Diaphorapteryx,
Rodriguez with Erythromachus, Mauritius with
Aphanapteryx, all of which have died out recently.
Although they are structurally so much alike, that
we might unhesitatingly put them into one genus,
if they did occur together, they have each received
a second generic name ; rightly though, because they
must have developed independently of each other

vi] DISTRIBUTION OF SELECTED GROUPS 109

into what they are. It was a great mistake to use
these recent rails, simply because they were flightless,
as a support of the former existence of the great
southern continent. On Tristan da Cunha, in the
middle of the South Atlantic, lives the tiny flightless
Gallimda nesiotis.

Cranes are an Old World group, most numerous
in Africa, less numerous in Eurasia ; only one kind
of crane lives in Western North America and one in
Australasia. Cranes are absent from New Zealand,
the Malay Islands, Madagascar, Central and South
America. This is very remarkable considering
that these birds are some of the best-flying mi-
grants.

Other genera, combining specialised with ancient
characters, have very isolated ranges, an indication of
the great age of the whole group. For instance, the
Cariama and Chuna in South America ; also Psophia,
the Trumpeter, to which is undoubtedly related the
Miocene Patagonian Phororhacus with its gigantic,
monstrous skull. Rhinochetus, the Kagu, is restricted
to New Caledonia. Eurypyga, the Sunbittern, in
tropical America, together with Heliornis, the Fin-
foot, which is scarcely generically distinct from Podica
in Africa and further India.

Bustards are really rails adapted to life on grassy
plains. They form an absolutely Old World family,
inhabiting Europe, Asia, Africa and Australia, but

110 THE WANDERINGS OF ANIMALS [CH.

neither New Zealand, nor the naturally unsuitable
Malay Islands, nor Madagascar.

Birds of Prey. The American vultures or
Cathartae form a separate sub-order ; absolutely
restricted to both Americas. The Old World scaven-
gers, Vulturidae, are chiefly African, whence they
extend in a peculiar manner. They occur regularly
in Mediterranean countries, thence far into India
but stopping short of China, Borneo, Sumatra,
Ceylon and Madagascar. The osprey, Pandion, is
cosmopolitan, with the curious exceptions of Ireland,
Iceland and New Zealand. Accipitres, the diurnal
birds of prey, without the Cathartae, are known
from French Oligocene, e.g. the * secretary-bird '
which is now restricted to Africa. They are an
essentially Old World order, which however has sent
many eagles, hawks and falcons to America.

Gallinaceous Birds. It was upon the present
distribution of the fowl tribe that Huxley to a great
extent founded his division of the globe into a north
and south world. I. Peristeropodous or pigeon-footed
fowls, i.e. with all the toes on the same level, are
(1) the Megapodes or Talegallas or brush turkeys in
Australasia, from Tasmania to the Philippines ; (2) the
American forest fowls, curassows and guans, or
Cracidae from Paraguay to Texas, excluding Antilles.
II. Alectoropodous or cock-footed, with the hind-toe
rooted above the front-toes. To these GalUdae belong

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vi] DISTRIBUTION OF SELECTED GROUPS 111

the following somewhat arbitrary sub-families, each
with a still well-marked radiating centre. Guinea-
fowls restricted to Africa and Madagascar. Pheasants,
'fowls' and peacocks essentially southern Asiatic.
Turkeys are peculiar to North and Central America.
The Tetraoiiinae are essentially holarctic : most
numerous in North America, e.g. prairie fowls, others
in tropical America ; grouse are circumpolar ; caper-
caillie Eurasian, also partridges ; francolins are Indo-
African ; quails have the widest distribution, over
most of the Old World, including Madagascar, and
even New Zealand had one, quite recently extin-
guished, species.

Cuckoos are a cosmopolitan family, even New
Zealand possessing several kinds. Our common
cuckoo ranges over most of the Old World. The
present distribution of the various sub-families yields
no tangible results, since most of them have allied
genera in Asia, Africa and South America, and there
is no convincing ground for assuming that their
original centre was Eastern Asia. The Turacoes or
helmet-cuckoos are an entirely Ethiopian family.

Parrots seem to have originated in the Aus-
tralian region, which alone contains members of all
the sub-families and the more ancient forms, whilst
other continents possess only members of the family
Psittaciae. South America has the structurally most
advanced genera. India and Africa are poor in

112 THE WANDERINGS OF ANIMALS [OH.

parrots. Brush -tongued parrots, Trichoglossidae, are
strictly Australasian (east of Wallace's line to Tahiti),
chiefly ' lories,' with the ancient ' keas,' Nestor, in
New Zealand and Norfolk Island. Psittacidae, com-
prising all the others, have a smooth tongue. String-
ops, the kakapo or owl parrot, with weak flying power
and much reduced keel of the breast-bone, in New
Zealand. Cockatoos are abundant in Australia and
Papuasia.

Coraciiformes. Rollers, bee-eaters, kingfishers,
hoopoes and hornbills represent closely related
families of undoubtedly Old World origin. The
numerous family of kingfishers is cosmopolitan, most
abundant in Papuasia, but only a few species of the
otherwise widely-distributed genus Ceryle are the
sole representatives in America. Hoopoes and horn-
bills are Afro-Indian, but absent from Madagascar ;
on the other hand hornbills extend far beyond
Wallace's line, through New Guinea into the Solomon
Islands. The screech- or barn-owl inhabits almost
every country in the world, Scandinavia, America
north of 45°, and New Zealand being the principal
exceptions. Humming-birds are a highly specialised
and probably recent family of neotropical origin ;
they exend to Tierra del Fuego, to the far outlying
island Juan Fernandez, to the Galapagos and of
course the Antilles ; towards the north they become
scarce, but one kind is a summer visitor of Mount

vi] DISTRIBUTION OF SELECTED GROUPS 113

Elias in Alaska, and the tiny Trochilns colubris
breeds in Canada and Labrador.

Trogons are tropical ; America, Africa, exclud-
ing Madagascar, Indian and Malayan. Most of the
Old World genera retain a colour-pattern which is
juvenile in the American species, which comprise
also the most gorgeous kinds. They point to a direct
Afro- American connexion, and this is quite com-
patible with the occurrence of Trogons in French
Oligocene.

Woodpeckers also seem to have originated in South
America ; now the family is cosmopolitan with the
exception of Madagascar, Australian countries and
Polynesia.

P assert formes. More than half the number of
recent birds belong to this order. The lesson of their
distribution cannot be appreciated without reference
to their systematic affinities.

I. Clamatores, with imperfectly developed sing-
ing apparatus ; the few muscles are attached either
to the middle, or to the dorsal, or to the ventral edge
of each bronchus. Structurally the lowest Passeres
are the broadbills or Ewrylaemidae, restricted to the
Indies and Malaya. Allied are the ant-thrushes or
pittas from New Britain to Madagascar and West
Africa ; Xenicus and a few others in New Zealand.
Lastly, tyrants, manakins, bellbirds, ant-birds, in all
about 1000 kinds in South America, whence many of

G. 8

114 THE WANDERINGS OF ANIMALS [CH.

the tyrants have spread into North America, chiefly
as migrants.

II. Oscines or singing birds ; with the muscles
attached to the dorsal and to the ventral edge on
either side of the syrinx. The lowest of these birds
are the Suboscines, of which the only representatives
are the lyre-bird, Menura, and two small kinds of
scrub-bird, Atrichornis, in Australia. The rest, half
of the species of the whole class, are the Oscines or
singing birds proper, which having probably origin-
ated in the northern half of the Old World have
since attained world-wide distribution.

MAMMALS.

The earliest remains of mammals have been
found in the Triassic of Carolina, Dromatherium
and Microconodon, and of South Africa, Tritylodoti
and Theriodesmus ; others have been described from
Patagonian Eocene. This is practically all we know
of -possible Prototheria or representatives of the
earliest stage of mammals, of which the monotremes
are supposed to be the sole and much -modified
survivals. Of the next stage, the Metatheria, the
marsupials are the modernised survivals, or side
branch, whilst from the main Metatherian stem has
been evolved the last or Eutherian stage, comprising
the placental mammals. As to the place of origin

vi J DISTRIBUTION OF SELECTED GROUPS 115

of earliest mammals it does not matter much where
they are found, because, being of at least Triassic age,
the whole world may have been overrun by them
during the enormous stretch of the Jurassic period.
In any case there was time for them to have reached
Australia, immaterial whether still quite Prototherian
or already recognisable as Monotremes.

The recent Monotremes are the duck-bill, Orni-
thorhynchus, and a few species of spiny ant-eaters,
Echidna, in Tasmania and Australia, and Proechidna
in New Guinea.

Marsupials.

The pouched mammals, comprising about 1/0
recent species, have a very discontinuous distribution.
Their headquarters are now Australia with Tasmania
and the Papuan Islands ; two phalangers have reached
Celebes, and two dozen species, mostly opossums,
survive in America.

It is customary to divide the marsupials into
I. Polyprotodonta, with three or four pairs of lower
incisors, e.g. Didelphidae or opossums, mostly in
Central and South America ; but one, Didelphys
virginiana, the common opossum, ranges from Argen-
tina far into the United States. Chironectes, the
little water opossum, lives in tropical America.
Dasyuridae comprise the 'native devils' and the wolf-
like Thylatinus or Tasmanian ' tiger.' Allied is the

8—2

116 THE WANDERINGS OF ANIMALS [CH.

* ant-eater ' Myfmecobius of West Australia and the
small ' marsupial mole,' Notoryctes typhlops, a blind
digger in the barren centre. II. Diprotodonta, with
only one pair of lower incisors, usually enlarged, e.g.
the numerous kangaroos, Macropodidae, one genus
of which, Dendrolagus, contains the tree-kangaroos.
The phalangers are a very diversified family ; all
are climbers ; some, e.g. Petaurus, look exactly like
flying squirrels, others like mice. The tiny Tarsipes
lives in Western, the koala or l native bear,' Phascol-
arctos, in East Australia. Two phalangers are
restricted to Celebes. Phascolomys, the wombat,
has assumed rodent-like characters. Lastly, two
small species of Caenolestes in Ecuador and Co-
lombia are also diprotodont and possibly more
nearly related to the Australian phalangers than to
the strictly American opossums.

A time-honoured explanation of the present dis-
tribution of marsupials is that they had an almost
world-wide range when Australia was still accessible
from the north. When, after the separation, the
Placental mammals had been evolved in Arctogaea,
the marsupials could no longer hold their own, except
those which were safely shut up in the Australian
region, and except the few opossums in America
which saved themselves by early adopting an arboreal
life. In principle this story is right, but wrong in
detail. It is also awkward for this hypothesis that

vi] DISTRIBUTION OF SELECTED GROUPS 11

hitherto not one single marsupial fossil is known
from India, nor from any other part of Asia.

Many pre-Tertiary mammalian remains are known
from Europe, North and South America, mostly
nothing but teeth and under-jaws. Presumably all
the Jurassic and Lower Cretaceous mammals were
Metatheria, leaving aside the Monotremes, q.v., but
it is often impossible to decide whether the Upper
Cretaceous and even some of the Eocene creatures
were still in the Metatherian stage, whether they were
already Placentals or whether they were typical mar-
supials. We begin to discern three great groups.

1. Archaic Metatheria with Diprotodont ten-
dency. The so-called Multituberculata or Allotheria,
e.g. Microlestes from Upper Trias of Europe ; Plagi-
aulax from Upper Jurassic of Europe and North
America ; Meniscoessus from Upper Cretaceous of
North America; Polymastodon and Neoplagiaidax
from North America and European Palaeocene.
Others, supposed to be related to the Allothema,
have been described from Patagonian Cretaceous
and Eocene deposits. But these Allotheria (i.e.
1 different beasts ') have not much to do with the true
marsupials, certainly not with the Diprotodonta,
although they are diprotodont, a feature which has
been evolved at various times and by various orders.
However, the Allotheria, of which many remnants
are known, mostly from Wyoming and Patagonia,

118 THE WANDERINGS OF ANIMALS [CH.

undoubtedly indicate land connexion of North and
South America during at least part of the Cretaceous
epoch, and a longer intercourse bet ween North America
and Europe.

2. Archaic Metatheria of Jurassic date, some of
which are supposed to be ancestral to the Insectivora,
e.g. Triconodon,Amphitherium, Dryolestes of England
and North America,

3. Archaic or ancestral marsupials.

(a) Polyprotodonta, with a complete set of four
pairs of lower incisors, e.g. Pediomys and Didel-
phops of North American Upper Cretaceous. Bor-
hyaena from South America, Eocene to Miocene,
supposed to be nearly allied to the Australian
Thylacinus. Paratherium from Lower Eocene into
Oligocene in North America where it died out,
but continued in Europe from Upper Eocene into
Lower Miocene, indistinguishable from the recent
Didelphys, which is also known from South Ameri-
can Pleistocene, whence one species, the common
opossum, D. virginiana, now extends far into the
United States.

(b) Diprotodonta. Many species of Epanorthus
and Abderites in Patagonian Tertiary, considered as
allies of the recent Colombian Caenolestes. Their
diprotodont feature may be a case of parallelism with
the Australians, but it is significant that the recently
discovered Wynardia bassiana, described by Spencer

vi] DISTRIBUTION OF SELECTED GROUPS 119

from Tasmanian early Tertiary, is said to be inter-
mediate between Australian Poly- and Diprotodonts.
To sum up. Metatheria existed during the Ju-
rassic period both in England and in North America.
They disappear in Europe, but reappear in North
America with the Upper Cretaceous as undoubted
direct forerunners of marsupials, and they extended
their range during the same epoch into South America.
Opossums appeared in America in the Eocene,
whence they spread into Europe, but neither they,
nor others, flourished in the northern continents,
probably because the Eocene also marks the appear-
ance of the Placentalia, with which the inferiorly
organised marsupials could not compete. But that
marsupial stock which had got into South America
was safe there, because that continent we know to
have been separated from the north from Eocene to
Miocene times. There they produced a considerable
number of forms, until these also vanished before
the inroad of carnivorous Placentals, excepting the
opossums. Further, to the South American mar-
supials the way was open to the antarctic lands,
which in turn were connected with Australia, Ion"'

' O

after the latter, with Papuasia, had been severed
from Asia. The marsupials, after their long wander-
ings over three-quarters of the globe, had found in
the Australian region a wide expanse of country
in which they have developed groups analogous to

120 THE WANDERINGS OF ANIMALS [CH.

many of the Placentals, for instance the rodent-like
wombat, phalangers resembling flying squirrels,
Notoryctes like a blind mole, the ant-eater Mjrme-
cobius, fleet pasturing herds of kangaroos and a fierce
wolf-like Tkyldcinus.

It is of the greatest significance that all the recent
marsupials have feet modified for arboreal life (either
with an opposable hallux, or with the second and
third toes joined together) or at least show unmis-
takeable traces that their immediate ancestors have
passed through such an arboreal modification, even
the large kangaroos and the clumsy monster, Di-
protodon of Central Australian Pleistocene. They all
had been fitted for life in the trees, and when in
Australia this necessity was removed, some of them
again took to living on the ground.

Edentates.

Three dozen species, most of them in tropical
America, a few in Africa, India and Malaya, are
the survivors of an ancient assembly of terrestrial
mammals, which are reasonably supposed to be an
early offshoot of the Placentals.

Scaly ant-eaters or pangolins, Manidae, date from
mid-Oligocene of France ; now mostly prehensile and
arboreal, in tropical Africa and India to Celebes ;
absent from Madagascar.

vi] DISTRIBUTION OF SELECTED GROUPS 121

The Cape ant-eater, Orycteropus, with other
species in West and East Africa ; fossil from Miocene
France, Pliocene Samos and Persia and Pleistocene
Madagascar.

All the other Edentates are American, appearing
suddenly in a great variety of forms in the Upper
Miocene of South America ; extending to North
America with the Pliocene.

Ground-sloths, Megatherium, etc. are now extinct.
Neomylodon (=Grypothermm domesticum), with dried
skin and hair, has been found recently in a Patagonian
cave.

Armadillos with an abundance of Tertiary genera,
are now much reduced in numbers. The nine-banded
armadillo has the widest range, from Argentina to
Texas.

Ant-eaters, Myrmecophaga, and sloths, Bradypus,
are confined to tropical America.

If the Edentates of the Old and New World are
related to each other, they may be the remainder of
an old Afro-Indian fauna of Eocene date. They could
have spread by Asia Minor into Europe ; or some of
the common stock may have found their way to
Brazil where they developed into the ' Xenarthra'
typical of South America, whence by the end of the
Miocene they could extend into North America,
although no longer into the Antilles. If, however,
the Taeniodonts and Ganodonts of the Lowest and

122 THE WANDERINGS OF ANIMALS [CH.

Low Eocene of North America should prove to be
4 primitive Edentates,' and if Metachiromys of North
American Eocene were an armadillo, as has been
asserted and denied, then we might look for the
original home of the order in North America, whence
they spread into the south, leaving a blank in the
north. The north and south connexion became avail-
able in the Miocene, in time enough for the outburst
of the order in South America, but far too late for
Africa and Europe.

Rodents.

This vast order comprises almost 1000 recent
species and is, as an order, quite cosmopolitan ;
some of the families are already recognisable in the
Eocene.

Hares, with the chief genus Lepus, date from
American Oligocene ; earliest occurrence in Eurasia
not until the Pliocene. Now on every continent ;
absent from Australia and all ancient islands. The
variable hare, which turns white in winter, ranges
from Greenland and Canada through Siberia and
Scandinavia, with the outlying centres of Ireland,
Scotland, Pyrenees, Alps, Caucasus and Japan.

Squirrels, etc. are cosmopolitan excepting Aus-
tralasia, Madagascar and Antilles. Flying squirrels
have developed in India, northern Europe and Siberia,
and thence in the pine forests of North America.

vi] DISTRIBUTION OF SELECTED GROUPS 123

A peculiar flying form is Anomaliirus, the palm-
marten of West Africa. Other outlying forms are
the jumping hares, Pedetes, of the South African
veldt.

Beavers of temperate and cool Eurasia came late
into North America.

Rats and mice are absolutely cosmopolitan. Even
Australia has several peculiar genera : the aquatic
Hydromys, the Queensland rat Xeromys and several
'jumpers.' Many genera in Eurasia and North
America, whence steadily decreasing through Central
into South America. Remarkable are the Dipodidae,
known from American Eocene onwards : Zapus in
Canada and China ; alactagas and jerboas from
Eastern Asia to North Africa, the former extending
into interglacial Europe as typical steppe-creatures.
The brown rat is Asiatic, crossed the Volga in 1727,
arrived in Germany in 1770, shipped a few years
later to North America and has since overrun the
whole world.

Porcupines in the wider sense, or Hystrichomorpha,
are important : Afro- Indian and tropical American ;
whilst many fossils are known from European Eocene
and Oligocene, none occur in North America. Chin-
chillas, agutis, guinea-pigs, etc. live in Central and
South America. Porcupines : Hystrix mid-Miocene
in Europe, now Afro-Indian ; prehensile-tailed tree-
porcupines, e.g. Synetheres, from Bolivia to Mexico ;

124 THE WANDERINGS OF ANIMALS [CH.

only one genus, EreMzwi, has reached North
America, now up to Alaska and Labrador. Lastly,
the Octodont family : Aulacodus in North Africa
and Abyssinia; Capromys in the Bahamas and
others in South America, where they existed in the
Miocene. There can be no doubt that the Hystricho-
morphs are of Old World origin. Long before the
mid-Miocene, divers members must have passed from
Africa directly into tropical America, which by the
Lfpper Miocene had already become a new centre
of dispersal. It is certain that this continent did not
receive its supply from the north.

Insectivores.

The order, with 200 recent species, is cosmopolitan
with the exception of the South American continent
and Australasia. There are some in Cuba and Hayti,
many in Madagascar, but none on other outlying or
oceanic islands. Occurring already in the Eocene of
North America and Europe, they died out in the
former continent which has received its present sup-
ply of ' star-nosed' and 'web-footed' moles and shrews
from Eurasia in late Tertiary times.

Centetidae and allies. Beginning in Lower Oligo-
cene of North America with forms allied to Solenodon
of Cuba and Hayti, a most primitive, generalised
Placental. These are related to the Ethiopian

vi] DISTRIBUTION OF SELECTED GROUPS 125

Potamogale and Geogale of Madagascar, which in
turn are allied to the Tenrecs, e.g. Centetes of Mada-
gascar, where this family flourishes in many genera
and species. Centetes and Solenodon, with striking
mutual resemblances, have been a sore puzzle to the
zoo-geographer.

Golden moles (Chrysochloris) inhabit South Africa,
but undoubtedly related to them is Necrolestes of
the mid-Miocene in Patagonia. Considering that the
above-mentioned families are not known from Europe,
these Insectivores with V-shaped molars indicate an
early Tertiary Afro- American land connexion.

Hedgehogs in the wider sense disappeared from
America in the Oligocene ; descendants are the Indian
Gynmura and Erinaceus, the hedgehogs proper, now
in Eurasia and North America.

Moles and shrews are now arctogaean, but with
very few in Africa, and the American immigrants
mentioned above have not reached tropical America.

Tree-shrews, Tupaia, are Oriental ; the elephant
shrew, Hacroscelides, and other jumping shrews are
African.

Bats.

Bats have a world- wide distribution, limited only
by the polar climates. Some of the present genera
are first known from the Eocene of Europe, and
yet, and in spite of their power of flight, bats did

126 THE WANDERINGS OF ANIMALS [CH.

not reach America until the Pleistocene. Moreover
some of the chief families, and still more the smaller
groups, are restricted in their range, which means
that even these well-flying creatures consider not
only oceans, but narrow seas as obstacles.

The Pteropodidae or flying foxes, strict vege-
tarians, inhabit all the warmer countries of the Old
World, from Africa to India, Australia and Tahiti,
but not New Zealand.

The Rhinolophidae or leaf-nosed bats, e.g. our
horse-shoe bats, are also restricted to the Old World.

The Phyllostomidae or vampires are tropical
American, including Antilles. Of them only Desmo-
dm and Diphylla are true blood-suckers, but not the
genus Vampyrus ! North America proper possesses
only members of the quite cosmopolitan family
Vespertilionidae.

Carnivores.

This large order of almost 300 recent kinds is
cosmopolitan, excepting New Zealand, many small
oceanic islands and Australia but for the solitary
Dingo.

The Carnivores are undoubtedly of northern,
holarctic, origin, but their centre of evolution was
soon shifted to Eurasia. During the Pliocene none
persisted in North America but dogs, coons and
skunks. Bears and true cats have entered that

vi] DISTRIBUTION OF SELECTED GROUPS 127

continent later. India possesses representatives of
all the recent families ; Africa proper has all but
bears ; South America is relatively the poorest con-
tinent.

Creodonta or archaic mammals with a carnivorous
dentition have existed, in great numbers, since the
Eocene in North America, whence they spread into
Europe, and later into Africa. Most of these beasts
died out with the Eocene, or rather they were modern-
ised into the typical Carnivora, in various parts of the
world. Some however kept on to almost recent times
as highly specialised Creodonts, e.g. the sabre-toothed
tigers : Nimravm in North American Oligocene ;
Machaerodus from Miocene to Pleistocene in Europe
and Asia, whence in the Pleistocene it appeared as
Smilodon in America which this terrible beast con-
quered to the far south. Meanwhile, with the mid-
Miocene, somewhere in Eurasia were evolved modern
cats of the genus Felis. With the Pliocene these
found their way into North America and later into the
south ; being such late arrivals, they were debarred
from the Antilles. Cats are now cosmopolitan ex-
cepting the Antilles, Madagascar and the countries
to the east of Java and Borneo.

Civet-cats or viverras are an exclusively Old
World family, dating from Eocene Europe. Their
great age explains the existence of the Fossa (Crypto-
procta), and some others peculiar to Madagascar.

128 THE WANDERINGS OF ANIMALS [OH.

Hyaenas, since Miocene in England and Asia, now
in the whole of continental Africa and the south-
west quarter of Asia. Both the striped and the
spotted kind, the latter now only in South Africa,
lived in interglacial England.

The dog- tribe date from late Eocene in North
America and Europe, now cosmopolitan even in the
Falkland Islands, but absent from Antilles, Madagascar
and to East of Wallace's line. Australia is overrun
by the Dingo, a dog of unknown origin.

The genus Canis was not ready until the Pliocene.
Weasels and otters have the same wide range.

Bears appear as various genera in Eurasian
Miocene. The genus Ursus appeared with the Plio-
cene, and with the Pleistocene entered North America,
ranging into Mexico and reappearing on the Andes.
Although inhabiting all Asia and until recent days
all Europe, bears never seem to have found their way
into Africa proper, excepting the Atlas range.

Elephants.

The earliest archaic elephantine beasts have been
discovered in Egyptian Upper Eocene : Moeritherium
and Palaeomastodon, the latter with a pair of upper
tusks pointing downwards, and a pair of lower, spoon-
shaped incisors. With the Miocene appears Tetra-
belodon, with upper and lower tusks, curved upwards,

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vi] DISTRIBUTION OF SELECTED GROUPS 129

in Europe, India and North America. They change
into ' Mastodonts ' proper, characterised by reduction
and loss of the lower tusks and more complicated
molars. Such mastodonts flourished during the
Pliocene and overran not only Eurasia but also
America to the Andes. M. americamis survived far
into Pleistocene. Meanwhile in some of the Asiatic
stock the molars not only had changed the 'lumpy
teeth ' into such with transverse, numerous, lamellae
but into practically evergrowing teeth by delay of
root-formation. Such ' elephants ' proper are the
E. indicus now of India and Sumatra, a close ally of
the E. meridionalis and of E. primigenim, the ' hairy
mammoth' of Pleistocene Europe and Siberia. It-
entered America late. Somewhat earlier arrivals
in North America meeting there the mastodon, were
E. columbi and E. imperator, the largest of all,
extending their range into Southern Mexico. But
this sojourn in the New World was short lived.
Meanwhile somewhere in Asia a side departure was
marked by lozenge-shaped, instead of parallel molar
lamellae, e.g. E. antiquus of the Lower Pleistocene of
Europe and North Africa, which now culminates in the
African elephant, separated as Loxodon on account
of its tooth pattern.

Thus it has come about that these powerful beasts
after having overrun the world so far as it was
accessible to them, have within quite recent times

G. 9

130 THE WANDERINGS OF ANIMALS [CH.

become restricted to the southern countries of the
Old World, India and Africa, whence they originally
started.

Swine and Hippopotamus.

Small swine were plentiful in Upper Eocene
Europe, later in North America, where they have
left only the Peccaries, which now range from Texas
to Argentina. In Eurasia pigs have produced a
number of surviving genera. Sus, dating from
Upper Miocene, has the widest range, from Ireland
(exterminated) and Morocco to' New Guinea and
Japan. The Babirusa, with its four up-curled tusks,
is peculiar to Celebes. Warthogs and riverhogs are
now African, south of the Sahara, with one riverhog
also in Madagascar. This is paralleled by the former
existence of a small hippopotamus in the same island,
allied to the pigmy hippo in Liberia, whilst the hippo,
formerly in India and Europe, lives now in Africa,
south of the Sahara.

Camelidae.

The few surviving members of the Tylopoda,
i.e. pad-footed ruminants, tell a remarkable history of
dispersal. From the Upper Eocene of North America
they can be traced through an unbroken series of
still generalised forms into the Pliocene, when they
split into early camels, e.g. Procamelus, and early

vi] DISTRIBUTION OF SELECTED GROUPS 131

llamas, Pliauchenia. Both groups spread far beyond
North America. During the Pliocene, Auchenia
appeared in South America, where this genus is still
represented by lamas and huanacos on the Andine
tablelands. Pliauchenia had found its way to India,
where it died out. Early camels likewise must have
reached Asia, because in India appears the first true
Camelus, which in Pleistocene times spread into North
Africa, and also into North America, where it met
several other aboriginal camel-like forms. Then they
all died out there, so that now this once flourishing
family of enormous and continuous range, is rent
in two, its members existing in a wild state only on
the Andes and the Central Asian highlands.

Chevrotains.

TheChevrotains comprise a few small-sized animals
which still resemble primitive or ancestral deer-like
ruminants, since they are intermediate in structure
between pigs, camels and deer. Their earliest an-
cestors have been traced to the Upper Eocene of
Europe and North America. The only still existing
genera are first Hyomoschus, the water-chevrotain
of West Africa, also in the Pliocene of Asia and
in the Miocene of Europe, although those fossils
are usually mentioned as Dorcatherium. Secondly,
several species of Tragulm, often called Moose-deer,
in Indo-Malay countries.

9—2

133 THE WANDERINGS OF ANIMALS [OH.

Deer.

Modern deer, ruminants with yearly-shed antlers,
are of exclusively Eurasian origin, and the first
brockets were developed in mid-Miocene times.
They are absent from Australasia, Madagascar, Africa
south of Barbary and the Antilles.

Stags (Cervus) existed, since the Pliocene in
Europe and Asia, whence the wapiti spread into
America with the Pleistocene. Somewhat earlier
immigrants produced there the slightly different
American deer, Cariacw, which now extends from
the States to Patagonia.

Reindeer, elk or moose are circumpolar. The
roebuck, Capreolus, is Eurasian.

The peculiar prongbuck, Antilocapra,of the south-
west States and tableland of Mexico has no deciduous
antlers but sheds the horny sheaths of the bony cores.
In this respect it is intermediate between deer, the
giraffe (now African, with related genera in Pliocene
Greece and India) and the following tribe :

Cattle and Antelopes.

Hollow-horned ruminants with a permanent horny
sheath to the bony core of the horns, appear first in
Eurasian Miocene. Omitting the arctic musk-ox, the
whole tribe of oxen, sheep, goats and antelopes live
in the Old World, with few exceptions : the Rocky

vi] DISTRIBUTION OF SELECTED GROUPS 133

Mountain goat, which is really a modified chamois,
the big-horn sheep, and the bison, all of which are
Pleistocene immigrants to North America. Antelopes
are abundant in continental Africa, few in Central
Asia, whence the steppe-loving saiga-antelope visited
interglacial Europe.

The ' Mountain Antelopes' have now a very dis-
continuous distribution. Rupicapra, the chamois,
ranges from the Cantabrian mountains through the
Pyrenees and Alps to the Caucasus ; with somewhat
distant relations in India and Central Asia ; and
with Haploceras, the ' Rocky Mountain goat.' Sheep
and goats are natives of Asia and of Mediterranean
countries and islands ; one goat lives in Abyssinia
and two big-horn sheep, allied to the Argali, etc. of
Asia occur in Western North America. The bovine
beasts, or cattle proper, are also very limited in
numbers of species. The yak is confined to the
high mountain ranges of Central Asia. The scanty
survivors of the two bisons linger, the one in North
America, the other in the Caucasus and in Poland.
The bantengs are Oriental from Northern India to
Java. Of the buffaloes, one inhabits India, another
is confined to the Philippine Islands, and two others
live in Africa. Celebes has the peculiar rather
ancient anoa. The ancestor of our domestic cattle
is lost in obscurity, although probably allied to the
aurochs (Bos primigenius) of medieval Central Europe.

134 THE WANDERINGS OF ANIMALS [OH.

Rhinoceros.

The whole drama of the evolution of the true
rhinos has been played in Eurasia.

In the Oligocene of Europe and America appear
hornless Aceratheres and pair-horned Diceratheres,
e.g. also Arsinoetherium of Egypt. None of the
right-and-left horned beasts have left descendants;
nor did the hornless forms in America, but in Asia
some introduced the principle of median horns and
such single and tandem-horned rhinos alone have
survived in the Old World, whilst those which reached
America in mid-Miocene times died out.

Two-horned Old World species are : R. suma-
trensis ; R. etrmciis, in Pliocene and early Pleistocene
Europe ; its much larger and very hairy successor
R. megalorhinus of mid-Pleistocene Europe ; R. ticho-
rhinus-antiquitatis, of the steppes and tundras of
interglacial Europe and Siberia, closely related to the
black or long-lipped and the white orsquare lipped
rhinos of Africa. R. indicus has one horn.

Tapirs.

The cradle of the future tapirs stood somewhere
in Northern Asia ; the earliest recognisable genus
Systemodon of the American Lower Eocene being
a blind offshoot. With the Lower Oligocene appears
Protapirm in Europe ; it found its way into North

vi] DISTRIBUTION OF SELECTED GROUPS 135

America where it changed into Tapir avus and con-
tinued well into the Miocene when it died out. But
in Eurasia Protapirus changed into Paratapirm
which in turn produced the Pliocene Tapirus proper.
Formerly also in Europe its only descendant in the
Old World is now the Indo-Malay species, none
having made their way into Africa. Others however
got, in Pleistocene times, into North America, soon to
die out there, except those two or three kinds which
are now in tropical America, including South-East
Mexico.

Thus has come about the striking case of dis-
continuous distribution of a small and very natural
family at two opposite parts of the equator.

Horses.

The story of the horse tribe is based upon such
an abundant material that pedigrees with dozens of
generic names have been constructed, and its very
intricate story has been so often condensed and
popularised that the horse has become the show-
animal of evolution. Yet, although the evolution of
the tribe as such is well understood, often in minute
detail, that of the genus Equus, the horses, asses and
zebras proper, is not known. The main reason is that
since early Tertiary times there existed in America,
Asia and Europe a bewildering mass of odd-toed

136 THE WANDERINGS OF ANIMALS [OH.

creatures which drifted towards that goal of per-
fection which has been reached only by the horse.
Number of toes, length of limbs and neck, shape of
the skull, pattern of teeth, general size, all were in
a flux towards certain improvements, but these many
characters did not all keep step in the same creatures.
The Hyracotheres of Eocene America and Europe
(scarcely larger than a cat, with four front and three
hind toes, e.g. the so-called Eohippos) are still so very
generalised that they lead to horses, rhinos and tapirs,
as well as to other distinct groups. We therefore
disregard them and begin with the Mesohippos of
American mid-Oligocene ; size of a sheep, three-toed,
with somewhat elongated limbs. Later relations,
during the Upper Oligocene, are perhaps Miohippos,
and Anchitherium which soon made its appearance
in Europe, flourishing there during the whole of
the Miocene, when its line became extinct. In any
case Anchitherium was an offshoot. Meanwhile in
American Miocene steady progress is represented
by a line of successive forms (Desmat-Para-Hy$)o-
Merychippus\ and all promised well, when, about
the end of the Miocene, this stock came to an end
in America. Whether members of this same stock
had spread into Asia, or whether there had taken
place a similar parallel evolution out of the ancient
common stock, we do not know. Suffice it to state
that with the Upper Miocene we have to start

vi] DISTRIBUTION OF SELECTED GROUPS 137

again with Protohippos which suddenly appears in
America, together with the Eurasian Hipparion.
The latter persisted in Europe into the Upper
Pliocene (Britain to Africa, Persia, Russia, China
and India) ; with the early Pliocene it also crossed
into America, where its various kinds are dis-
tinguished as Neohippdrion, and some of these
which got right into South America are called
Hippidion. All these Hipparions had admittedly too
specialised a tooth -pattern to serve as the ancestors
of Equus ; their feet were still tridactyle, but the
side -toes were slender and only just touched the
ground. Here is a gap, usually slurred over. Crea-
tures intermediate between these three-toed animals
and the genus Equus (in which the side-toes are
reduced to splints on either side of the middle or
cannon-bone) are unknown.

The genus Equus appears as E. sivalensis in
Pliocene Asia ; other species, e.g. E. stenonis, in
Europe, supposed ally of zebras. E. caballm, the
horse, appears with the Pleistocene in Europe, North
Asia and North-West America from Alaska to
California ; and a whole crowd of other horses,
amongst them the large pony-sized E. scotti, overran
the whole of America, all to die out there with the
Pleistocene epoch. But in Asia and in Mediterranean
countries appear the asses, tar pan and djiggetai and
this dweller of steppes extended in interglacial times

138 THE WANDERINGS OF ANIMALS [OH.

to Germany and Switzerland. Przewalsky's horse
in Central Asia is the only really wild horse still in
existence.

Dugongs and Seals.

The earliest Sirenians are known from the Eocene
of Jamaica and Egypt, others from Oligocene and
Miocene of France and Italy, and from Pliocene
North-West America and Japan. They are a strong
support of the existence of a transatlantic bridge, along
the northern coast of which they lived in early
Tertiary times, and of an Atlantic-Mediterranean-
Indian sea. The present distribution of the few
recent kinds still bears this out. Manatis inhabit
the coasts of the Antilles, Central and South America,
and Africa from the Senegal to Natal, ascending also
the big rivers on either side. Dugongs live along the
coasts of the Indian Ocean, from Mozambique to the
northern coasts of Australia. Rhytina, Steller's sea-
cow, was North Pacific, exterminated in 1768.

Seals, to mention another order of marine mam-
mals. The walrus is polar ; during the glacial epoch it
extended down to the coast of France. Eared seals
are Northern Pacific, from Japan to Mexico, and with
a wide equatorial interval on both coasts of South
America, Southern Australia, New Zealand and Ant-
arctica. The earless seals have a still wider range;
around the antarctic continent and southern islands,

vi] DISTRIBUTION OF SELECTED GROUPS 139

e.g. Kerguelen (sea-elephants, etc.) and in the
Northern Atlantic, Baltic and the whole polar basin.
Of special interest is the occurrence of the two monk
seals, Monachus tropicalis in the Mexican gulf and
M. albiventer from the Canaries into the Eastern
Mediterranean. Further, a land-locked seal in the
Caspian and another in Lake Baikal, the former
identical with our common Phoca vitulina, and the
other with the northern ringed seal, P. foetida.

Lemurs and Monkeys.

Remains of archaic lemur-like creatures have
been found in Patagonian Paleocene, in somewhat
later Eocene of North America and in Europe where
they extend into the Oligocene. Then they vanish
and there is a break between them and the recent
lemurs of tropical Africa and Madagascar, with
another centre in Malacca and the three great Malay
islands ; and with the ancient queer little Tarsius
spectrum in Sumatra, Borneo, Celebes and the Philip-
pines.

There is also a complete gap between lemurs and
monkeys ; and further a still unbridged gulf between
the marmosets and prehensile-tailed monkeys, all of
which are tropical American, and the Old World mon-
keys which inhabit now the whole of Africa (excluding
Madagascar), South Arabia, India to South Japan and

140 THE WANDERINGS OF ANIMALS [OH.

the Malay Islands. Such monkeys are known from
Miocene Europe, even an ape-like Dryopiihecm.
The famous Pithecanthropus erectus of Java is but
of Pleistocene date and would do well enough for
ancestral man, if we did not feel sure that the genus
Homo must date back at least into the Pliocene epoch.
But that is another story.

SUMMARY OF MAMMALIAN DISPERSAL.

Australia as the earliest great mass of land
permanently severed from the rest is in almost un-
disturbed possession of the lowest mammals. It is
the sole refuge of the monotremes, and the marsupials
have narrowly escaped a similar fate. They take us
to the next independent continent, South America.
This had three chances, or epochs, of being stocked
with mammals. Within the Cretaceous period it
seems to have received its marsupial stock from the
north, the progenitors of all modern marsupials.
A second influx, during the early Tertiary brought
edentates and rodents as its first Placentals from
Africa, and those queer Ungulates the Toxodonts
and Pyrotheria, unless we prefer to look upon these
Eocene extinct orders as truly aboriginal to South
America, when this was still continuous with the
ancient Brazil-Afro-Indian Gondwanaland. The third
and last inroad came once more from the north, when

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vi] DISTRIBUTION OF SELECTED GROUPS 141

with the close of the Miocene permanent connexion
with North America was reestablished. This brought
the modern odd-toed and pair-toed Ungulates, with
dogs, cats and bears in their wake, and lastly man.

There remains the huge North World. Eurasia
and North America have always formed a wide
circumpolar ring, which repeatedly broke and joined
again. Whatever group of terrestrial creatures was
developed in the eastern, Asiatic, half, was sure to
turn up in the western, and vice versa.

Lastly, the mysterious African continent. It began
originally as the centre of the ancient equatorial South
World ; it has lost these connexions and has become
joined to the northland, after many vicissitudes. It
is therefore most difficult to apportion its fauna
rightly ; moreover for fossils it is almost a blank,
except Egypt. It must have had some share in the
evolution of mammals, like edentates, rodents, In-
sectivores, hyrax, elephants, sirenians and lemurs,
all groups with an ancient stamp. But what share
it had, against Eurasia, in the development of say
Ungulates, Carnivores, monkeys, we do not know.
Not much is likely to have originated in Europe ; the
elephants, rhinos, hippos, lions and hyaenas were
migrants rather from than to Africa, rarely across
some Mediterranean bridge, usually by Asia Minor.

The more dominant forms of our present fauna
have originated, to use an expression of Darwin's,

142 THE WANDERINGS OF ANIMALS [CH. vi

' in the larger areas and more efficient workshops of
the north/ and the balance is in favour of Asia as the
cradle of modern mammals.

Is it an idle dream to think of the future?
A survey of the past reveals the vanishing of whole
faunas from extensive countries, which were then re-
peopled by other forms from elsewhere. What has
happened before, may happen in times to come.
Countless groups, once flourishing, are no more ;
many others have had their day and are now on the
decline, whilst others are flourishing now, are even on
the increase and seem to have a future before them.
Such favoured assemblies are the toads and frogs,
lizards and snakes, Passerine birds and rodents, mostly
the small-sized members of their tribes ; the days
of giants are past. All this has happened in the
natural course of events, without the influence of
man, who only within most recent times has become
the most potent and destructive factor to the ancient
faunas of the world.

BIBLIOGRAPHY 143

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FORBES, E. The Natural History of the European Seas. Lon-
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DANA, J. D. On the Geographical Distribution of Crustacea.
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SCHMARDA, L. K. Die geographische Verbreitung der Thiere.
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SCLATER, P. L. On the geogr. distr. of the members of the Class
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HUXLEY, T. H. On the classification and distribution of the
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On the progress of Palaeontology. Anniv. address, Geol.

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WAGNER, M. Die Darwinsche Theorie und das Migrationsgesetz

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WALLACE, A. R. The Geographical Distribution of Animals.

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Island Life. London, 1880.

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BLANFOBD, W. T. Anniversary address. Proc. Geolog. Soc.,

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ALLEN, J. A. The geogr. distr. of Mammals. Bull. U.S. Geol.

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HEILPRIN, A. The Geographical and Geological Distribution

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MARSHALL, W. Atlas der Thierverbreitung. Gotha, 1887.
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BEDDARD, F. E. A text-book of Zoogeography. Cambridge, 1895.
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ORTMANN, A. E. Grundziige d. marinen Thier geographic.

Jena, 1896.
The geogr. distr. of Fresh-water Decapods and its bearing

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MERRIAM, C. H. Laws of Temperature Control of the geographical

distribution of Animals and Plants. Nat. Geogr. Mag., iv.

1894, pp. 229-238. [Especially for text pp. 45-47.]
STOLL, 0. Zur Zoogeographie d. landbewohnenden Wirbellosen.

Berlin, 1897.
ROSA, D. La Riduzione progressica della Variabilita. Torino,

1899.
POCOCK, R. J. Geogr. Distr. of Mygalomorphae. Proc. Zool. Soc.,

1903.
SEWARD, A. C. Floras of the Past. Address, Brit. Ass.

(Southport), 1903.
GRABAU, A. W. Phytogeny of Fusus and its allies. Smithson.

Misc. Coll. XLIV. 1904.
BOULENGER, G. A. The distrib. of African Fresh-water Fishes.

Address, Brit. Ass., 1905.
KRAEPELIN, K. Geogr. Yerbreitung der Scorpione ; der Scolo-

pendriden. Zool. Jahrbucher, 1905.

BIBLIOGRAPHY 145

EIGENMANN, C. H. The Fresh-water Fishes of South and Middle

America. Popular Sci. Monthly, LXVIII. 1906.
MATTHEWS, W. D. Hypothetical Outlines of the Continents in

Tertiary times. Bull. Amer. Mus. N. H. New York, 1906.
SCHARFF, R. F. European Animals ; their geological History

and geographical Distribution. London, 1907.
ARLDT, TH. Entwicklung der Kontinente und ihrer Lebewelt.

Leipzig, 1907.
KOSSMAT, F. Paldogeographie* Sammlung Goschen. Leipzig,

1908.
WILLIS, B. Palaeogeographic Maps of North America. Journ.

of Geology, xvu. Chicago, 1909.
WILLISTON, S. W. Faunal relations of early vertebrates. Journ.

of Geology, xvu.
GADOW, H. The effect of Altitude upon the distribution of

Mexican Amphibians and Reptiles. Zoolog. Jahrbiicher,

1910.
Articles 'Birds' and 'Reptiles' in Encyclop. Brit, llth

edition.
SCHUCHERT, CH. Palaeography of North America. Bull. Geol.

Soc. America, xx. 1910. Pis. 46-101.
OSBORN, H. F. The Age of Mammals. London and N. York,

1911.

HAUG, E. Traite de Geologic. Paris, 1907-1911.
BARTHOLOMEW, J. G., CLARKE, W. E., and GRIMSHAW, P. H.,

Atlas of Zoogeography. Edinburgh, 1911.

10

INDEX

Aestivating Frogs 38

Agamas 101

Agassiz, A. 9

Alactagas 123

Albatros 105

Alligators 99

Altitudinal distribution 43

Amphibians 95, 101

Amphisbaenas 101

Antarctic connections 81, 88, 95,

98
Anteaters, Cape, 121 ; climbing

28; scaly 120; spiny 115
Antelopes 132
Antilles 83, 86, 94, 96, 101, 103,

124, 128
Arboreal frogs 26, 97 ; snakes 27 ;

mammals 28, 121
Arctic ' facies ' 57
Arctogaea 6

Areal density of species 74
Argali 133
Armadilloes 121
Asses 137

Atmospheric pressure 44
Auks 107
Aurochs 133
Axolotl 96

Bantengs 133
Barn owl 112
Bats 125
Bears 128

Beavers 123
Bee-eaters 112
Big-horn sheep 133
Biota 49

Birds, migrations 65 ; distribu-
tion 104
Bison 133

Blanford, W. T. 6, 12
Boatbill 105
Broadbills 113
Brush-tongued parrots 112
Buffaloes 133
Buff on, G. L. 3
Bustards 109

Camels 130
Cape anteater 121
Capercailly 111
Cariama 109
Carnivores 126
Carp etc. 94
Cassowaries 104
Cats 127

Celebes 130, 133, 139
Centres, creative 14
Chameleons 101
Chamois 133
Chevrotains 131
Chorology 7, 17
Chufia 109
Civet-cats 127
Climbing edentates 28
Climbing porcupines 28

INDEX

147

Cloudbelt 46

Cobra 103

Cockatoos 112

Coloration, desert creatures 42 ;

in tropical forests 24
Coloration, patterns 24
Convergent development 57
Cope, E. D. 60
Copper-head (Ancistrodon sp.)

103

Cormorants 105
Crab-plovers 107
Crabs 91
Cranes 108, 109
Crayfishes 91
Crocodiles 98
Cuckoos 111

Dana, J. D. 5

Darwin, Ch. 7

Deer 132

Density, areal d. of species 74

Desert frogs 38

Desert lizards 39 ; snakes 41

Desert mammals 41 ; birds 42

Deserts 30

Desmoulins, Ch. 4

Diprotodont marsupials 116, 117,

118

Distribution, vertical 43, 53
Divers 105
Djiggetai 137
Dodo 108
Dogs 128
Duck-bill 115
Ducks 106
Dugongs 138

Eared seals 138
Earthworms 62, 87
Edentates 120 ; arboreal 28
Eels 93

Elephants 128
Elephant shrew 41
Environment, features of 18 ; in-
fluence of 59
Eyelids of lizards 40
Eyes, protection of 40

Fabricius, J. C. 4

Fiji islands 92, 102

Firebellied toad 97

Fishes, migrations 69; distribu-
tion 93

Flamingoes 106

Flash-colours 24

Flying dragon 28

Flying foxes 126

Flying frog 28, 98

Flying insectivore 28

Flying marsupials 116

Flying rodents 28; phalangers
28; squirrels 28

Forbes, E. 5

Forests, tropical 18

Fossa 127

Frogs, marsupial 29

Frogs 98 ; aestivating 38 ; ar-
boreal 26

Frogs, care of young 29

Frog-toads (Cystignathidae) 98

Galapagos 86, 100, 102, 105,

112

Gallinaceous birds 110
Gaunets 105
Geckos 40, 101
Geological geography 76
Giraffe 132
Glacial epoch, effect of 55, 56,

58, 66, 128, 133, 134, 137
Glass-snakes 101
Golden moles 125
Gondwanaland 81, 95

148

INDEX

Grebes 105
Ground-sloths 121
Grouse 111
Guillemots 107
Guinea-fowls 111
Gulls 107

Haeckel, E. H. 7
Hare, variable 57
Hares 122
Hedgehogs 125
Heilprin, A. 12
Herons 105
Hibernation 52
Hipparion 137
Hippopotamus 130
Hoopoes 112
Hornbills 112
Horned toad 39
Horses 135
Horse-shoe bats 126
Huanacos 131
Humming birds 112
Huxley, T. H. 10, 110
Hyaenas 128

Iceland-bridge 86

Iguanas 102

Increase of population 72

Insectivores 124

Insects 90

Interglacial Europe 128,

134, 137
Ireland 86
Islands, age of, 86

Jacanas 107
Jerboas 41, 123
Jumping hares 123
Jumping shrews 125

Kagu 109

133,

Kakapo 112
Kangaroos 116
Kea- parrot 112
Kingfishers 112
Kinkajou 28
Kiwi 104

Lamas 131
Latreille, P. A. 4
Lemming 67
Lemuria 87
Lemurs 139
Limbs, reduction of 39
Lizards 101 ; nostrils 39 ; eye-
lids of 40 ; flying 28
Lories 112
Lyall, Ch. 5
Lyre-bird 114

Madagascar 82, 87, 92, 94, 100,
109, 110, 112, 124, 127, 130

Mammalian dispersal 146

Mammals 114

Mammoth 129

Man, fossil 146

Maps, reconstruction of geological
76, and at end of volume

Maps, diagrammatic 84-85

Marsupial frog 29

Marsupials 29, 115, 119

Matamata 100

Merriam, C. H. 144

Mice 123

Midwife toad 97

Migrations 61

,, of birds 65 ; mammals
67; fishes 69

Moas 104

Moles 125

Moloch 39

Molluscs 91

Monkeys, 27, 139

INDEX

149

Monotremes 115, 119
Moose-deer 131
Mother-of-pearl 91
Mountains, environment 43
Mud-eel 96
Mud-turtles 100
Murray, A. 8
Mussel shells 91

Native bear 116

Native devil 115

Neogea 6

Newton, A. 12

New Zealand, 87, 95, 98, 104,

108, 109, 110, 113
Nostrils of lizards 39
Notogaea 6

Oecology 7, 17
Opossums 115, 118
Ortmann, A. E. 17, 91
Oscines 114
Osprey 110
Ostrich 104
Otters 128
Owl parrot 112

Painted snipes 106
Palm-martens 27
Pampas 31
Pangolins 120
Parachuting creatures 28
Parrots 111
Partridges 111
Peacocks 111
Pelicans 105
Peripatus 90
Petrels 105
Pheasants 111
Philippine Islands 87, 133
Pigeons 107
Pigs 130

Pikes 93

Pithecanthropus 140
Pit-vipers 103
Placentalia 114, 117
Population, natural increase 72
Porcupines 123
Prairies 31
Prehensile tail 27
Prongbuck 132
Protection of eyes 40

,, by coloration 42
Przewalsky's horse 138
Pucheran, J. 7j

Quails 111
Queensland rat 123

Bails 108

Eain-catching contrivances 35

Rainfall 19, 32

Ratitae 104

Rats 123

Rattlesnakes 103

Reconstruction of Maps 79

Regions, zoological 12-15

Reindeer 132

Rhea 104

Rhinoceros 134

Riverhogs 130

Rocky Mountain goat 133

Rodents 122

Roebuck 132

Rollers 112

Rosa, D. 60

Riitimeyer, L. 8

Sabre-toothed tigers 127
Saiga antelope 123
Salamanders 96
Sandgrouse 68, 107
Scaly anteaters 120
Scharff, R. F. 17

150

INDEX

Schmarda, L. K. 5

Sclater, Ph. L. 5

Scorpions 93

Screamers 106

Screetch owl 112

Scrub-bird 114

Sea-elephants 138

Seals 138

Seed-snipes 107

Semper, C. 9

Shoebill 105

Shrews 125; jumping 123

Singing birds 114

Sirenians 138

Sloths 28, 121

Slow-worms 101

Snakes 102 ; arboreal 27

Snowline 44

Solitaire 108

Spadefoot toad 97

Species, areal density of 74 ;

numbers of 69, 75
Spiny anteater 115
Spreading, mode of 61
Squirrels 122
Stags 132

Steller's seacow 138
Steppes 31
Stone-curlew 106
Storks 105
Sunbittern 109
Surinam toad 97
Swainson, W. 4
Swine 130

Tail, prehensile 27

Tapirs 134

Tarpan 137

Tasmanian tiger 115, 118, 120

Tejus 102

Temperature, decreasing with al-
titude 44
Tiedemann, F. 4
Toads (Bufonidae) 97
Tortoises 99
Tree frogs 24, 26, 97
Tree-kangaroos 116
Tree-line 49
Tree-porcupines 123
Tree-shrews 125
Treviranus, G. E. 4
Tristan da Cunha 109
Trogons 113
Trouessart, E. L. 12
Trumpeter 109
Turacoes 111
Tyrant-birds 113

Vampires 126
Varans or Monitors 101
Vipers 103
Vultures 110

Wagner, M. 9
Wallace, A. K. 10
Wallace's line 103, 112, 128
Warthogs 130
Water-chevrotain 131
Water-opossum 115
Weasels 128
Weka rails 108
Whale-headed heron 105
Wombat 116
Woodpeckers 113

Yak 133

Zimrnermann, E. A. W. 4
Zoo-geography 15
Zoological regions 12-15

CAMBRIDGE : FEINTED BY JOHN CLAY, M.A. AT THE UNIVERSITY PRESS.

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THE

CAMBRIDGE MANUALS
OF SCIENCE AND LITERATURE

Published by the Cambridge University Press
GENERAL EDITORS

P. GILES, Litt.D.

Master of Emmanuel College

and
A. C. SEWARD, M.A., F.R.S.

Professor of Botany in the University of Cambridge

70 VOLUMES NOW READY
HISTORY AND ARCHAEOLOGY

Ancient Assyria. By Rev. C. H. W. Johns, Litt.D.

Ancient Babylonia. By Rev. C. H. W. Johns, Litt.D.

A History of Civilization in Palestine. By Prof. R. A. S.

Macalister, M.A., F.S.A.

China and the Manchus. By Prof. H. A. Giles, LL.D.
The Civilization of Ancient Mexico. By Lewis Spence.
The Vikings. By Prof. Allen Mawer, M.A.
New Zealand. By the Hon. Sir Robert Stout, K.C.M.G., LL.D.,

and J. Logan Stout, LL.B. (N.Z.).
The Ground Plan of the English Parish Church. By A.

Hamilton Thompson, M.A., F.S.A.
The Historical Growth of the English Parish Church. By A.

Hamilton Thompson, M.A., F.S.A.

English Monasteries. By A. H. Thompson, M.A., F.S.A.
Brasses. By J. S. M. Ward, B.A., F.R.Hist.S.
Ancient Stained and Painted Glass. By F. S. Eden.

ECONOMICS

Co-partnership in Industry. By C. R. Fay, M.A.

Cash and Credit. By D. A. Barker.

The Theory of Money. By D. A. Barker.

LITERARY HISTORY

The Early Religious Poetry of the Hebrews. By the Rev.

E. G. King, D.D.
The Early Religious Poetry of Persia. By the Rev. Prof. J.

Hope Moulton, D.D., D.Theol. (Berlin).
The History of the English Bible. By John Brown, D.D.
English Dialects from the Eighth Century to the Present Day.

By W. W. Skeat, Litt.D., D.C.L., F.B.A.
King Arthur in History and Legend. By Prof. W. Lewis

Jones, M.A.

The Icelandic Sagas. By W. A. Craigie, LL.D.
Greek Tragedy. By J. T. Sheppard, M.A.
The Ballad in Literature. By T. F. Henderson.
Goethe and the Twentieth Century. By Prof. J. G. Robertson,

M.A., Ph.D.

The Troubadours. By the Rev. H. J. Chaytor, M.A.
Mysticism in English Literature. By Miss C. F. E. Spurgeon.

PHILOSOPHY AND RELIGION

The Idea of God in Early Religions. By Dr F. B. Jevons.

Comparative Religion. By Dr F. B. Jevons.

Plato : Moral and Political Ideals, By Mrs A. M. Adam.

The Moral Life and Moral Worth. By Prof. Sorley, Litt.D.

The English Puritans. By John Brown, D.D.

An Historical Account of the Rise and Development of Presby-

terianism in Scotland. By the Rt Hon. the Lord Balfour

of Burleigh, K.T., G.C.M.G.
Methodism. By Rev. H. B. Workman, D.Lit.

EDUCATION

Life in the Medieval University. By R. S. Rait, M.A.

LAW

The Administration of Justice in Criminal Matters (in England
and Wales). By G. Glover Alexander, M.A., LL.M.

BIOLOGY

.The Coming of Evolution. By Prof. J. W. Judd, C.B., F.R.S.
Heredity in the Light of Recent Research. By L. Doncaster,

M.A.

Primitive Animals. By Geoffrey Smith, M.A.
The Individual in the Animal Kingdom. By J. S. Huxley, B.A.
Life in the Sea. By James Johnstone, B.Sc.
The Migration of Birds. By T. A. Coward.

BIOLOGY (continued)

Spiders. By C. Warburton, M.A.
i Bees and Wasps. By O. H. Latter, M.A.
vxHouse Flies. By C. G. Hewitt, D.Sc.

Earthworms and their Allies. By F. E. Beddard, F.R.S.

The Wanderings of Animals. By H. F. Gadow, F.R.S.

ANTHROPOLOGY

The Wanderings of Peoples. By Dr A. C. Haddon, F.R.S.
Prehistoric Man. By Dr W. L. H. Duckworth.

GEOLOGY

Rocks and their Origins. By Prof. Grenville A. J. Cole.
The Work of Rain and Rivers. By T. G. Bonney, Sc.D.
The Natural History of Coal. By Dr E. A. Newell Arber.
The Natural History of Clay. By Alfred B. Searle.
The Origin of Earthquakes. By C. Davison, Sc.D., F.G.S.
Submerged Forests. By Clement Reid, F.R.S.

BOTANY

^Plant-Animals : a Study in Symbiosis. By Prof. F. W. Keeble.

U Plant-Life on Land. By Prof. F. O. Bower, Sc.D., F.R.S.

>- -Links with the Past in the Plant- World. By Prof. A. C. Seward.

PHYSICS

The Earth. By Prof. J. H. Poynting, F.R.S.
The Atmosphere. By A. J. Berry, M.A.
Beyond the Atom. By John Coy., M.A.
The Physical Basis of Music. By A. Wood, M.A.

PSYCHOLOGY

lx An Introduction to Experimental Psychology. By Dr C. S.

Myers.
The Psychology of Insanity. By Bernard Hart, M.D.

INDUSTRIAL AND MECHANICAL SCIENCE

The Modern Locomotive. By C. Edgar Allen, A.M.I.Mech.E.

The Modern Warship. By E. L. Attwood.

Aerial Locomotion. By E. H. Harper, M.A., and Allan E.

Ferguson, B.Sc.

Electricity in Locomotion. By A. G. Whyte, B.Sc.
Wireless Telegraphy. By Prof. C. L. Fortescue, M.A.
The Story of a Loaf of Bread. By Prof. T. B. Wood, M.A.
Brewing. By A. Chaston Chapman, F.I.C.

SOME VOLUMES IN PREPARATION
HISTORY AND ARCHAEOLOGY

The Aryans. By Prof. M. Winternitz.

Ancient India. By Prof. E. J. Rapson, M.A.

The Peoples of India. By J. D. Anderson, M.A.

The Balkan Peoples. By J. D. Bourchier.

Canada of the present day. By C. G. Hewitt, D.Sc.

The Evolution of Japan. By Prof. J. H. Longford.

The West Indies. By Sir Daniel Morris, K.C.M.G.

The Royal Navy. By John Leyland.

Gypsies. By John Sampson.

A Grammar of Heraldry. By W. H. St John Hope, ;^itt.D.

Celtic Art. By Joseph Anderson, LL.D.

ECONOMICS

Women's Work. By Miss Constance Smith.

LITERARY HISTORY

Early Indian Poetry. By A. A. Macdonell.

The Book. By H. G. Aldis, M.A.

Pantomime. By D. L. Murray.

Folk Song and Dance. By Miss Neal and F. Kidson.

PHYSICS

The Natural Sources of Energy. By Prof. A. H. Gibson, D.Sc.

The Sun. By Prof. R. A. Sampson.

Rdntgen Rays. By Prof. W. H. Bragg, F.R.S.

BIOLOGY

L/The Life-story of Insects. By Prof. G. H. Carpenter.

L>The Flea. By H. Russell.

U Pearls. By Prof. W. J. Dakin.

GEOLOGY

Soil Fertility. By E. J. Russell, D.Sc.
Coast Erosion. By Prof. T. J. Jehu.

INDUSTRIAL AND MECHANICAL SCIENCE

Coal Mining. By T. C. Cantrill.
Leather. By Prof. H. R. Procter.

Cambridge University Press

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