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                   _THE CONTEMPORARY SCIENCE SERIES._

                        Edited by HAVELOCK ELLIS.




                    THE HISTORY OF THE EUROPEAN FAUNA




                           THE HISTORY OF THE
                             EUROPEAN FAUNA


                   R. F. SCHARFF, B.Sc., Ph.D., F.Z.S.

   _Keeper of the Natural History Collections, Science and Art Museum,
        Dublin; Member of the Royal Irish Academy; Corresponding
      Member of the Senckenbergische Naturforschende Gesellschaft._


                           WITH ILLUSTRATIONS.


                                 LONDON
                          WALTER SCOTT, LIMITED
                           PATERNOSTER SQUARE
                                  1899




CONTENTS.


                                    PAGE
  CHAPTER I.
      INTRODUCTION                  1-36

  CHAPTER II.
      PRELIMINARY CONSIDERATIONS   37-88

  CHAPTER III.
      THE FAUNA OF BRITAIN        89-131

  CHAPTER IV.
      THE ARCTIC FAUNA           132-188

  CHAPTER V.
      THE SIBERIAN MIGRATION     189-244

  CHAPTER VI.
      THE ORIENTAL MIGRATION     245-286

  CHAPTER VII.
      THE LUSITANIAN FAUNA       287-308

  CHAPTER VIII.
      THE ALPINE FAUNA           309-350

  BIBLIOGRAPHY                   351-354

  INDEX                          355-364




PREFACE.


Our knowledge of the present and past fauna of Europe is as yet
insufficient to indicate with precision the original homes of its
component elements, but I hope that the lines of research laid down
here, and the method of treatment adopted, will aid zoologists and
geologists in collecting materials for a more comprehensive study of the
history of our animals. I trust also that a fresh impulse will be given
by the publication of this book to the study of the Geographical
Distribution of Species. Collectors of Beetles, Butterflies, Shells, and
Fossils may derive some useful hints by its perusal and thus direct
their studies, so as to add, by accuracy in observation, to our
knowledge of the former geographical revolutions which have moulded our
islands and continents. To geographers, a survey of some of the more
important changes in the distribution of land and water in past
times--based upon the composition of our fauna--will be interesting. The
subject, however, is a complex one. I have ventured to indicate a
suitable method of treatment, and as such this attempt to elucidate the
history of the European fauna should be received.

This work was written as the outcome of a paper published in the
_Proceedings of the Royal Irish Academy_ (3rd series, vol. iv., 1897),
"On the Origin of the European Fauna." A summary of that paper appeared
in _Nature_ (vol. lvi., 1897), and fuller extracts of more important
parts, with some criticisms, in the _Geological Magazine_ (N.S., sec.
iv., vol. iv., 1897). I freely acknowledge the value of these
criticisms, which have largely assisted me to amplify and to improve
upon the ideas laid down in the paper.

I have found that it greatly facilitates comprehension of the arguments
used, to give a few maps indicating in a general way the extent of
former seas and continents. I may in this way, as Mr. Kendall has
pointed out, have submerged many square miles of land which had never
been covered by the sea,--at least not within recent geological
times,--but the maps were intended as illustrations of my views in a
broad spirit only.

Some zoologists may be surprised that, in some cases, I have not
followed the latest views in revised nomenclature. I felt that in a work
of this kind it was of supreme importance to employ names still current
in our leading text-books, such as _Lepus variabilis_ for the Mountain
Hare, instead of _Lepus timidus_. After each chapter I have endeavoured
to give a short summary of contents, while a bibliography of the
principal works and papers consulted will be found at the end. I should
also acknowledge the aid which I have received from such excellent
works of reference as the British Museum Catalogues of Birds, by Dr.
Bowdler Sharpe, and those of Reptiles, Amphibia, and Fishes, by Dr.
Günther and Dr. Boulenger. The valuable works on Mammalia by Sir W.
Flower, Mr. Lydekker, Mr. Grevé, and Dr. Trouessart, were indispensable
to me.

To Sir William Flower, Mr. Lydekker, Professor Sars, and Professor
Smitt, I am especially indebted for allowing me to reproduce drawings
from their works, and to my friend Mr. Welch for some beautiful
photographs. The Council of the Royal Irish Academy also kindly gave me
permission to reprint the maps used in illustration of my paper.
Professor Haddon first suggested my writing this book, and gave me many
useful hints; and great assistance was rendered me by my colleague, Mr.
G. H. Carpenter, in revising the proofs. To both of these kind friends I
desire to acknowledge my deep sense of gratitude.

                                        R. F. SCHARFF.




THE HISTORY OF THE EUROPEAN FAUNA.




CHAPTER I.

INTRODUCTION.


Every student of natural history, whether he be interested in birds,
butterflies, or shells, contributes his share of facts which help to
show how the fauna of his country has originated. The capture of a
Swallow-tail or of a Marbled White Butterfly in England at once
furnishes material for reflection as to the reason of its absence from
Scotland and Ireland. Why should the Nightingale allow its beautiful
song to be heard in England, and never stray across the Channel to the
sister isle or cross the borders of North Britain? Lovers of bird-life
and sportsmen, who have observed the habits of the Ptarmigan in the wild
mountain recesses of Scotland, are aware that nowhere else in the
British Islands do we meet with this interesting member of the grouse
family, and many no doubt have allowed their minds to dwell upon the
causes of its singularly local distribution.

All these animals have a wide range in other parts of the world. In
past times, before man began to make observations on the geographical
distribution of birds and butterflies, or even before the appearance of
man in Northern Europe, they may have lived all over the British
Islands. For some reason or other they are perhaps dying out or
withdrawing towards their original home, which may either be northward,
or to the east or south. If we had some clue as to their former history
from fossil evidence--or, in other words, if their remains had been
preserved to us in geological deposits,--we should have less difficulty
in deciding this problem. But butterflies are scarcely ever preserved in
a fossil state, and birds very rarely. We know little or nothing,
therefore, of their past history from direct evidence, and are obliged
to trust to indirect methods of research which will be indicated later
on.

Mammals and Snails tell us their story more plainly. The bones of the
former and the shells of snails are easily preserved, and thus furnish
us with the necessary data as to their past history, for we find them
abundantly in most of the recent geological deposits. Among the mammals
of the British Islands there are some instances of distribution which
much resemble those I have quoted. Thus the Arctic Hare (_Lepus
variabilis_) is in the British Islands confined to Ireland and to the
mountains of Scotland; and if it were not for the fact that its bones
have been discovered in a cave in the south-west of England, we should
perhaps never have known that, formerly, it must have inhabited that
country as well. Of other mammals we possess fossil and also historical
evidence of their having once lived in these islands. Such are the Wolf
and the Wild Boar, both of which were abundant in Great Britain and
Ireland. The latter is a distinctly southern species. We assume this,
because its remains have never been found in high northern latitudes;
nor does it now occur in Northern Europe or Northern Asia, whilst all
its nearest relatives live in sub-tropical or tropical climates. The
Arctic Hare, on the contrary, has probably come to us from the north.
Its remains are unknown even in Southern Europe, and the more we
approach the Arctic Regions, the more abundant it becomes. Thus we have
here two instances of British mammals, one of which, the Wild Boar, has
died out--as it were in a southerly direction; whilst the other, the
Arctic Hare, is apparently retreating towards the north.

There are also some British mammals of which we have no fossil history,
at least of which no remains have as yet been found in these islands.
Such a one is the Harvest Mouse (_Mus minutus_). It has a somewhat
restricted range in England, and only just crosses the Scottish border
in the east. From the rest of Scotland and from the whole of Ireland it
is absent. To judge from this distribution, in connection with the fact
of its being unknown as a British fossil species, it is probably a late
immigrant to England, and has not had time to spread, throughout
Scotland at any rate. But it is also absent from Scandinavia, from the
Spanish peninsula, from almost the whole of Italy and the Alps, as also
from the Mediterranean Islands, whilst the little mouse occurs
abundantly right across Siberia. We shall learn more about centres of
dispersion later on; meanwhile I should mention that such a distribution
indicates that the Harvest Mouse has most likely originated in the east,
and has spread from there westward in recent geological times.

Conchologists have long ago been acquainted with the fact that many
molluscs, for example the so-called "Stone-cutter" Snail (_Helix
lapicida_) and the "Cheese Snail" (_Helix obvoluta_), have a very
restricted range in the British Islands. Both are entirely absent from
Scotland and Ireland, the Cheese Snail being confined to South-eastern
England. The Stone-cutter has rather a wider range, is even known from a
Welsh locality, and is met with as far north as Yorkshire. Their
distribution would indicate, therefore, that while both are recent
immigrants, the Cheese Snail is probably the last comer. This
supposition is in so far supported by fossil evidence, as the latter is
unknown in the fossil state, whilst the Stone-cutter has been described
by Messrs. Kennard and Woodward (p. 243)[1] as occurring in the cave
deposit known as the Ichtham fissure, and also from several English
pleistocene and holocene deposits. The Stone-cutter can scarcely be
looked upon as a very recent immigrant in the light of this evidence,
though we have no proof of its having ever had a much wider range in the
British Islands than it has to-day.

Among the lichens, which so abundantly cover the rocks and trees in
South-western Ireland, and which impart such a characteristic feature to
the scenery, we find a beautifully spotted slug (_Geomalacus
maculosus_).[2] It is a stranger to the rest of the British Islands, and
indeed occurs nowhere else in Northern Europe. We have to travel as far
as Northern Portugal before we again meet with it, and it is there also
that its nearest relations live.

Many more similar examples might be quoted, but enough, I think, has
been said to show that the British fauna is made up of several elements
whose original homes may lie widely apart and in different directions.
We have fossil evidence that some of the northern species, and also a
few of the southern ones, have become extinct within comparatively
recent times; others are apparently on the verge of extinction, whilst
many not only maintain their position in the constant struggle for
existence, but are even extending their range.

The problem of tracing the origin of the British fauna, or at least that
of some of the more characteristic members of every section or element,
appears at first a somewhat difficult task. Indeed, the means of
dispersal of the various groups of animals are so different that it
occurred to me it might be better to deal with the mammals, the birds,
the reptiles, and so forth, all separately. This idea I have attempted
to follow to some extent, with most satisfactory results. The British
fauna of the present day is no doubt complex, but no more so than the
fauna of the most recent of our geological deposits--the Pleistocene.
However, when we go back still further and look at the earlier Tertiary
remains, we find the fauna becoming less complex. Northern species
disappear, and the strata are entirely filled with the remains of
southern animals and plants. Geologists indeed are quite unanimous in
their belief, that the fauna of the British Islands during the earlier
epochs of the Tertiary Era was a southern one; that it then gradually
became more temperate, until at last, in more recent times, decidedly
northern forms invaded the country. These seem to have driven out--to
some extent at least--the southern species; but more recently again, the
southerners, reinforced by an eastern contingent, appear to have gained
territory and are advancing into the area held by the northerners. The
eastern invasion does not seem to have affected Ireland at all, and we
find the country there divided between the southern and northern
animals. We can thus roughly construct a map as I have done here,
showing, by means of horizontal and sloping lines, the principal areas
inhabited at the present time by the species of northern, southern, and
eastern origin (Fig. 1).

[Illustration: Fig. 1.--Map of the British Islands, indicating
approximately the areas inhabited by the northern, southern, and eastern
animals. The horizontal lines represent the areas of northern species,
the sloping lines those of southern and eastern ones.]

In the problems which are being discussed in this work I have often
found it of advantage, in order to facilitate the comprehension of the
arguments used, to give maps. Some of these represent the geographical
conditions at the particular epoch referred to in the text, but they
merely claim to give a general idea. There was never any intention to
make them correspond with all the data of which we have geological
evidence. They are what I might call "diagrammatic." In comparing them
with reconstructions of former physical geography such as have been
attempted from time to time, I hope geologists will therefore deal
leniently with the faults I may have committed, and remember that the
maps are "impressions," or "diagrams," and not faithful representations
of all the geographical revolutions witnessed by some of our remote
forefathers at any particular period.

The knowledge we gain from a study of the British Tertiary deposits
enables us to affirm positively that both the eastern and the northern
species arrived in these islands comparatively recently, but that the
southern forms must have migrated northward from the Continent long ages
ago. Since the northern and the eastern migrations--that is to say,
those coming from the north and east--were the last to arrive in
Northern Europe, the remains of the animals contained in the most recent
deposits of that portion of our continent will furnish us with a clue as
to the extent of the area inhabited by them. This is not all, however.
It is also possible to discover from these remains the direction which
the animals that they belonged to came from. As we shall learn later
on, a migration on a vast scale entered Europe during the Pleistocene
epoch--the most recent of the geological epochs, during which great
extensions of glaciers occurred in the mountainous regions of Europe.
The latter period is known to us as the Ice Age or Glacial period. This
will be described more fully in Chapter II., meanwhile I may mention
that we presume that this migration came from the east, because no
remains of the members of that particular fauna are known from Spain,
Southern Italy, Scandinavia, Ireland, or from the Balkan peninsula. The
number of species evidently belonging to this same migration, moreover,
become fewer as we proceed westward, and a large proportion of them
still inhabit Northern Asia, though most of them are now extinct in
Europe. After having thoroughly studied such a recent geological
migration, we learn to understand others better, though the more ancient
they are, the fewer are the traces and the more difficult are they to
follow.

Then again we have to take into consideration the fact, that whilst
mammals, particularly the larger herbivores, are forced to migrate
frequently owing to scarcity of food or temporary changes of climate,
many of the invertebrates remain practically unaffected by either. Most
of our land mollusca, for instance, are satisfied with meagre provender,
and stand extremes of climate well, as long as there is sufficient
moisture. As a result of their peculiar disposition, many of them, no
doubt, have survived through several geological epochs, and have
witnessed vast geographical revolutions in their immediate surroundings,
whilst mammals are comparatively short-lived. Being driven from one
country to another, and exposed to innumerable enemies, new types appear
and old ones rapidly vanish; in fact, there are almost constant changes
in the mammalian fauna as we pass from one epoch to another.

I have until now referred more particularly to the British fauna and the
North European in general, because the history of our own animals
interests us all more than those of any other European area. It is,
moreover, preferable to commence our investigations into the origin of
the European fauna by the study of a small district. This should, if
possible, be an island. If we took a slice of the continent like France
or Germany, we should find the problem more complex. Instead of choosing
the British Islands, we might, however, take an island like Corsica or
Sardinia. In either of these we should discover peculiarities in the
composition of their fauna precisely similar to those which I have
indicated to be present in the British fauna. We should find probably a
more striking endemic[3] element, which with us is so meagre that it
can almost be left unnoticed; the main features, however, remain nearly
the same. The fauna of both of these islands is composed of a strong
southern element, of an eastern and a northern one, and in addition we
have here species whose ancestors lived in Western Europe.

Before investigating more minutely the problems suggested by the
composition of the faunas of these insular and also of some continental
areas, it is necessary that we should thoroughly understand all about
the migrations of animals. One of the principal objects of this work is
to show how the autochthonous animals of Europe, _i.e._, those which
have originated there, may be distinguished from the immigrants, and to
trace the latter to the home of their ancestors. But in doing so, it is
necessary to refer to the many important geographical changes which have
occurred in Europe during the latest geological epochs. The study of the
geographical distribution of the European fauna, as expounded in this
work, will in many instances confirm the theories as to geographical
changes based upon geological foundations. But in every case the views
herein advocated are founded upon the geographical distribution of
living and extinct organisms alone.

A terrestrial mammal like the deer can, under ordinary circumstances,
only reach one part of a country from another by walking or running to
it; but a beetle, such as the cockchafer, has two different modes of
progression. It may walk or fly. In both, however, there is a third mode
of transport--an involuntary one. The deer may be suddenly seized by a
flood whilst crossing a river, and carried far away without necessarily
coming to grief. The beetle in a similar manner could be transported to
a distant country, or it might be caught in a whirlwind and blown
hundreds of miles off.

We may thus distinguish between the natural or active and the accidental
or passive means of distribution of animals. The active mode of
dispersal again may be only migratory, as in most animals, or periodic
and migratory, as in some birds and fishes. It is of course the tendency
of every species to spread in all directions from its original home,
provided it does not encounter obstacles, such as want of food,
unsuitability of climate or soil, or barriers such as mountains, rivers,
or the sea. Birds might be thought to be little interfered with by any
of these barriers, but, as Dr. Wallace has shown, they are almost as
much affected by them in their distribution as mammals are.

This then is the ordinary migratory distribution. Periodic distribution
obtains with migratory birds and fishes. The annual flight of swallows
to their northern summer residence comes under the heading of periodic
migration or distribution, but apart from this, the swallow must seek to
extend its range by the ordinary method, like every other animal.
Similarly, the herring migrates periodically into shallow water to
spawn, only to return again to its deeper home, where, as its numbers
increase, there must be a tendency to spread. We have in these cases,
therefore, both a periodic and an ordinary movement of migration.

Now, in studying the composition of a fauna, and especially its origin,
it is of the utmost importance to be able to determine approximately the
percentage of accidental arrivals and of the ordinary migrants--that is
to say, of those which have reached the country owing to accidental
distribution, and of animals which have adopted the usual course of
migration. It is of all the more import to review this subject of
accidental, or, as Darwin called it, "the occasional means" of
distribution, as both he and Dr. Wallace have, I venture to think,
somewhat over-estimated its significance. No one doubts that accidental
transportal takes place, but the question is whether the accidentally
transported animals arrive living and reach a spot where suitable food
is procurable, and whether they are able to propagate their own species
in the new locality. For it must be clear to anybody that the accidental
transportal of a beetle or of a snail to a new country cannot affect its
fauna or add one permanent member to it unless all these conditions are
fulfilled. As a matter of fact, only exceedingly few instances are on
record of man having witnessed, for example, the accidental transportal
across the sea to an island of a live animal.

To mention an example, Colonel Feilden informs us (_Zoologist_, 1888)
that, when living on the island of Barbadoes, an alligator arrived one
day on the shore, and at the same time a tree measuring 40 feet in
length, which was recognised as a Demerara species, was likewise
stranded. He thinks that there can be no doubt that the alligator, which
was alive when it reached Barbadoes, was transported by the tree, thus
covering a distance of 250 miles from the nearest land. Numerous
observations on the accidental transportal of seeds and tree-trunks from
one island to another, and from a continent to an island, have been
recorded, and even on our own shores we may witness the occasional
arrival of such vegetable products from a far distant land. On the west
coast of Ireland it not unfrequently happens that large West Indian
beans are stranded, and in this as well as in many other similar cases
the seeds have often proved none the worse for their prolonged immersion
in sea-water. That locusts are sometimes blown to great distances from
the land is not so surprising, since their power of steering through the
air is very limited. Darwin mentions (p. 327) having caught one 370
miles from the coast of Africa, and that swarms of them sometimes
visited Madeira. Sir Charles Lyell relates that green rafts composed of
canes and brush-wood are occasionally carried down the Parana River in
South America by inundations, bearing on them the tiger, cayman,
squirrels, and other quadrupeds.

But though actual observations of such abnormal instances of the
dispersal of animals are few, many experiments have been made to
demonstrate the possibility of a passive transportal of species over
wide distances. It was especially Darwin who gave a great stimulus by
setting the example to those interested in natural history in the
conduct of such researches. He was struck by the fact that, though
land-shells and their eggs are easily killed by sea-water, almost all
oceanic islands, even the smallest and most isolated, are inhabited by
them, and felt that there must be some unknown but occasionally
efficient means for their transportal (p. 353). To quote his words: "It
occurred to me that land-shells, when hibernating and having a
membranous diaphragm over the mouth of the shell, might be floated in
chinks of drifted timber across moderately wide arms of the sea. And I
find that several species in this state withstand uninjured an immersion
in sea-water during seven days: one shell, the _Helix pomatia_, after
having been thus treated and again hibernating, was put into sea-water
for twenty days, and perfectly recovered. During this length of time the
shell might have been carried by a marine current of average swiftness
to a distance of 660 geographical miles. As this _Helix_ has a thick
calcareous operculum, I removed it, and when it had formed a new
membranous one, I again immersed it for fourteen days in sea-water, and
again it recovered and crawled away. Baron Aucapitaine has since tried
similar experiments: he placed one hundred land-shells, belonging to ten
species, in a box pierced with holes, and immersed it for a fortnight
in the sea. Out of the hundred shells, twenty-seven recovered. The
presence of an operculum seems to have been of importance, as out of
twelve specimens of _Cyclostoma elegans_ which it thus furnished, eleven
revived. It is remarkable, seeing how well the _Helix pomatia_ resisted
with me the salt-water, that not one of fifty-four specimens belonging
to four other species of _Helix_ tried by Aucapitaine, recovered. It is,
however, not at all probable that land-shells have often been thus
transported; the feet of birds offer a more probable method."

We have here positive evidence that such shells as _Helix pomatia_ and
_Cyclostoma elegans_ might easily be transported to an island from the
mainland. The former occurs in France, Holland, and England, and the
latter all along western continental Europe and England. And yet neither
of these species inhabits the Canary Islands, Madeira, or Ireland, none
of which are at too great a distance from Europe to be within easy reach
for a floating object. The fact that _Cyclostoma elegans_ does not live
in Ireland is of particular interest in connection with the
floating-theory just quoted, as on all sides of Ireland dead specimens
have been picked up on the shore, showing that marine currents carry
specimens and have thus transported them for countless centuries.
Nevertheless the species has not established itself in Ireland. If such
a fate meets a land-shell of the type of _Cyclostoma elegans_, it may be
asked, with some justification, what chance slugs or the smaller
non-operculated species would have to reach an island like Ireland
alive from the mainland, and to colonise it successfully.

Both slugs and their eggs are killed by a short immersion in sea-water,
as I have proved experimentally. I have also subjected slugs, in the act
of crawling on twigs, to an artificial spray of sea-water. This seemed
to irritate their tender skins to such an extent that they curled
themselves up, released their hold on the twig and let themselves drop
to the ground. If we supposed, therefore, that a slug had successfully
reached the sea, transported on a tree-trunk, the moisture would tend to
lure it forth from its hiding-place under the bark, whilst the mere
spray would prove fatal to its existence. Those species of snails and
slugs which lead an underground existence, rarely venturing above
ground, such as _Testacella_ and _Coecilianella_, would have even less
chance of being accidentally carried to some distant island.

The suggestion advanced by Darwin (p. 353), that young snails just
hatched might sometimes adhere to the feet of birds roosting on the
ground and thus be transported, appears to me so extremely improbable as
to be scarcely worth serious consideration. Indeed, as Darwin himself
acknowledged later on, it does not help us very much to suggest possible
modes of transport. What we require is direct evidence. How far we are,
however, from obtaining it, may be inferred from Mr. Kew's remark (p.
119), that "we have little or no actual evidence of precise modes of
dispersal even for short distances on land."

A very curious statement was made by a well-known French conchologist,
the late M. Bourguignat, with regard to introductions of mollusca.
Whether he had any actual facts collected in support of it, I cannot
say, but he maintained that species accidentally transported, with the
exception of those under maritime influence, can only be acclimatised
from north to south, and not from south to north--from east to west, but
not from west to east (p. 353).

The whole theory of the accidental or abnormal dispersal of mollusca
appears to have been originated by Darwin, in order to account for their
presence on so-called _Oceanic islands_. His views were strongly
supported by Wallace, who defines these islands (p. 243) as those which
are of volcanic or coralline formation usually far from continents,
entirely without indigenous land mammals or amphibians, but with a fair
number of birds and insects, and usually with some reptiles.

I do not wish it to be understood that I am in any way undervaluing the
great works of these distinguished naturalists. Darwin's views have had
more influence in advancing Zoology than those of any man, and his fame
is unassailable. Nevertheless, I feel that his theories regarding the
origin of the faunas of oceanic islands require revision.

The formerly prevalent belief of the permanence of ocean basins has been
shaken by the utterances of some of the greatest geologists of our day,
whilst many positively assert that what is now deep sea of more than
1000 fathoms was dry land within comparatively recent geological epochs.
Thus the Azores are classed by Darwin and Wallace among the oceanic
islands--that is to say, among such as have received their fauna and
flora by flotsam and jetsam. But Professor Neumayr believes, on
geological grounds, that the Old and New Worlds were connected by a
land-bridge during Tertiary times right across the Atlantic, and that
the Canary Islands, Madeira, and Azores (p. 547) are the last remnants
of this continent. This meets with the entire approbation of Dr. von
Ihering, who has recently re-investigated the subject from a faunistic
point of view (p. 135). Take another instance of one of Wallace's most
typical oceanic islands, the Galapagos Group. Their fauna and flora have
recently been most thoroughly re-explored by an American expedition, the
result of which, according to Dr. Baur, goes to show that these islands
must have formed part of the mainland of South America at no distant
date. The fauna and flora are therefore to be regarded as having reached
them in the normal mode, viz., by migration on land. According to Mr.
Beddard (p. 138), it is difficult to see how earthworms could be
transported across the sea. Floating tree-trunks have been observed far
out at sea, but unless the water remained absolutely calm during the
long period necessary for the drifting by currents so that no splashing
occurred, the worms would probably be killed. Yet earthworms do occur
on oceanic islands. It is indeed quite possible that our views with
regard to the origin of the remainder of the Pacific Islands may change
very materially, and once more revert to what Dr. Gould expressed nearly
fifty years ago in the following words: "From a consideration of the
land-shells on the Pacific Islands, it seems possible to draw some fair
inferences as to the relations of the lands which once occupied the area
of the Pacific Ocean, and whose mountain peaks evidently now indicate or
constitute the islands with which it is now studded." Indeed Dr. von
Ihering goes so far as to positively state that in his opinion the
Polynesian Islands are not volcanic eruptions of the sea floor, which
being without life were successively peopled from Australia and the
neighbouring islands, but the remains of a great Pacific continent,
which was in early mesozoic times connected with other continental land
masses (_a_, p. 425).

Before coming to a decision on the part played by flotsam and jetsam in
the constitution of an island fauna, those who have studied the problem
on the spot should, however, have a voice in the matter. And though,
from my experience in northern latitudes, I feel sure that island faunas
there are but slightly affected by occasional dispersal of species, Mr.
Hedley, who has made the fauna of the Pacific Islands his special study,
assures me that drift migration plays an important _rôle_ in that
region. I hope we may soon have a more detailed account of his
particular observation bearing on this interesting subject.

On the other hand, Mr. Simpson, who has gained considerable experience
of oceanic dispersal in the West Indian region, though he acknowledges
having often noticed bamboo rafts, which would be suitable in the
transportal of invertebrates, nevertheless does not attach much
importance to this means of distribution. "The fact," he remarks, "that
the operculates (operculate land-shells) form so large a proportion of
the Antillean land-snail fauna, that a majority of the genera are found
on two or more of the islands and the mainland, while nearly every
species is absolutely restricted to a single island, appears to me to be
very strong testimony in favour of a former general land connection" (p.
428).

Amphibians are affected in the same manner by sea-water as slugs are.
The accidental transportal of an amphibian from the mainland to an
island is therefore almost inconceivable. And the presence of frogs,
toads, and newts in the British Islands, in Corsica and Sardinia,
indicates, if nothing else did, that all these islands were at no
distant date united with the continent of Europe.

As regards the terrestrial reptiles, the case is somewhat different.
Many of them readily take to the sea, and, as probably all snakes and
some lizards are able to swim, it is possible that sometimes, though
very rarely, they might reach islands if not too far from a continent.
Instances of accidental transportal of land-reptiles to islands have
actually been observed. But the fact of the occurrence of such instances
by no means proves that reptiles thus conveyed are able to establish
themselves permanently in their new home. Sir Charles Lyell records in
his _Principles of Geology_ that a large boa-constrictor was once seen
floating to the island of St. Vincent, twisted round the trunk of a
tree. It appeared so little injured by its long voyage from South
America, that it captured some sheep before it was killed.

Mammals might be accidentally conveyed to islands on such rafts as have
been described by Sir Charles Lyell, and there are instances on record
of their having crossed short distances of sea by swimming. Elephants
and also deer and pigs are good swimmers, the former having been known
to swim for six hours at a stretch. "But," remarks Mr. Lydekker (p. 13),
"it may be assumed that about twenty miles is the utmost limit which
mammals are likely to cross by swimming, even when favoured by currents.
Such passages as these must, however, be of very rare occurrence, for a
terrestrial mammal is not likely to take it into its head to swim
straight out to sea in an unknown direction. Moreover, supposing a
mammal, near to a particular island, to have arrived there by swimming,
unless it happen to be a pregnant female, or unless another individual
of the same species but of the opposite sex should arrive soon after (a
most unlikely event), it would in due course die without being able to
propagate its kind."

All zoologists, indeed, are quite in accord with Dr. Wallace's view as
expressed in _Island Life_ (p. 74). "Whenever we find that a
considerable number of the mammals of two countries exhibit distinct
marks of relationship, we may be sure that an actual land-connection, or
at all events an approach to within a very few miles of each other, has
at one time existed." As all the European islands come under this
category, their mammals exhibiting distinct relationship with those on
the European continent, they all have been connected with it formerly.

Perhaps the most powerful of all agents in the transportal of species by
accidental means is man. But his actions may be accidental as well as
intentional. We have therefore to distinguish between the animals
disseminated all over the world by pure chance, and those which have
been introduced into new countries purposely. Invertebrates, such as
snails, centipedes, woodlice, beetles, and cockroaches, are constantly
being unintentionally carried with vegetables, fruit, trees, and with
timber from one country to another. Earthworms are sometimes transported
in the balls of earth in which the roots of trees are enveloped. As
regards molluscs, Mr. Kew believes (p. 178) that during the last three
centuries at least, human agency has influenced their disposal more than
all other causes taken together. A large number of species of
invertebrates in America are said to owe their existence in that country
to accidental introduction by man. In most cases, however, no
particular reason can be assigned why they should have been thus
introduced, and as a matter of fact there are always individual
differences of opinion as to the precise number of such. Certain it is,
that though the number of supposed introductions from Europe to America
is very large, those which have been carried from America to Europe is
exceedingly small. In fact, I remember only two instances of accidental
animal importations from America which have firmly established
themselves in Europe, viz., a small fresh-water mollusc, _Planorbis
dilatatus_, and the much-dreaded vine-pest, _Phylloxera vastatrix_.

As a rule the animals die out very shortly after their arrival on
foreign soil. Many instances, nevertheless, are on record, especially in
the case of molluscs, where snails thus transported have not only
survived but are apparently in a flourishing condition and spreading.
_Helix aspersa_, for example, our large garden snail, has been
naturalised in many foreign countries by French and Portuguese sailors,
who had taken them on board their ships as food.

It certainly cannot be denied that a number of species among almost all
groups of invertebrates have been unintentionally conveyed by man from
Europe into foreign countries. It has been proposed by Dr. von Ihering
to apply the term "cenocosmic" to those species which have become spread
all over the world through artificial means, and thus to distinguish
them from cosmopolitan ones which have attained a similar range
naturally. The latter he calls "palincosmic" species (_a_, p. 422). Many
so-called cenocosmic ants are believed by Dr. von Ihering to be
palincosmic. We are altogether too apt to regard cosmopolitan as
synonymous with introduced, and we should hesitate before concluding
that because one of our common European species occurs in Australia or
South America, it must have been transported there recently by human
agency. Some of our widely-distributed forms are probably of very great
antiquity, and may have spread to distant lands in early Tertiary times,
when a different state of the geographical conditions enabled them to do
so.

I cannot quote a more appropriate instance than the molluscan fauna of
Madeira. No less than thirteen of the Madeiran snails are looked upon as
having been introduced from Europe by human agency, on the sole evidence
that these happen to be common European species. Yet the correctness of
this supposition must be questioned in face of the interesting
observation made by Darwin (p. 357), "that Madeira and the adjoining
islet of Porto Santo possess many distinct but representative species of
land-shells, some of which live in crevices of stone; and although large
quantities of stone are annually transported from Porto Santo to
Madeira, yet this latter island has not become colonised by the Porto
Santo species. Nevertheless, both islands have been colonised by
European land-shells, which no doubt had some advantage over the
indigenous species." Darwin, therefore, meets the evident anomaly by
suggesting that the European species are supposed to possess some
advantages as colonisers. But the true explanation appears to me to lie
in the supposition that the European land-shells found in the Madeiran
Islands are all, or for the greater part, ancient forms which survived
both there and on the continent, whilst the remainder of the forms
inhabiting these islands are either such as are now extinct in Europe,
or have become modified since their arrival there from the continent at
a time when extensive land-connections allowed a free migration by land.

The theory of accidental introductions is an extremely popular one. It
allows free scope to a host of speculations, and once the idea has taken
firm root that a certain species is introduced, especially among the
class of naturalists who by way of experiment are wont to create new
centres of dispersion in their own neighbourhood, evidence to the
contrary must be of the most convincing nature to shake the popular
belief. Thus, it is almost regarded as an established fact by
conchologists and others, that the fresh-water mussel (_Dreyssensia
polymorpha_) was introduced into England at the beginning of this
century. Though it has been proved that this species is quite unable to
live in pure sea-water, yet the view that it has been carried from the
Black Sea ports to this country attached to the bottom of ships is
maintained by many, whilst others incline to the theory that the shell
came with timber. But _Dreyssensia polymorpha_ was by no means always
confined to the Caspian and Black Sea areas; it occurs abundantly in the
lower continental boulder-clay (see p. 230), and no doubt it had at one
time a much wider geographical distribution. It appears to me possible,
that it was able to maintain itself in certain fresh-water lakes and
slow-flowing rivers in Northern Europe, from which it might have spread
since the introduction of canals into Europe at the beginning of the
century. As the larva of this fresh-water mussel is free-swimming, its
propagation is much favoured by canals. Quickly-flowing rivers are fatal
to its existence, since the delicate larvæ are swept out to sea and
perish. Such an hypothesis as this is strengthened by the fact of its
recent discovery in a sandy layer fifteen feet below the present surface
under the streets of London in a deposit which probably, as Mr. Woodward
remarks (p. 8), was accumulated in the early days of the city's
existence. In spite of Mr. Woodward's interesting find, and Dr.
Jeffreys' opinion, who always maintained that this shell was indigenous
to England, popular belief still clings tenaciously to the introduction
theory.

Among man's intentional introductions into a new country, no instance is
better known than that of the rabbit to Australia. Rabbits are entirely
confined to Europe. In their transplantation to Australia they were
carried to a country with a different climate and among new
surroundings. Yet the rabbits flourished, and within comparatively few
years increased to such an extent as to become a burden and pest to the
country. It may be remembered though, that, owing to the complete
absence of small carnivores, which act with us as a check upon the too
rapid increase of this rodent, the speed with which it established
itself in the new surroundings is not so very surprising.

Many of the English settlers in the New World felt that America lacked
the presence of our familiar birds. The homely sparrow was therefore
brought over, with the result that the Agricultural Department of the
United States is now devising means for its destruction, so rapid has
been its increase.

Similarly, the inhabitants of Jamaica, annoyed by the great profusion of
rats in their island, sent over to India for a number of mongoose. These
have decimated the rats since their arrival, but they have multiplied to
such an extent as to be a serious menace to the native fauna.

To give an instance nearer home, the Capercaillie (_Tetrao urogallus_)
was successfully introduced into Scotland in 1837. From its different
centres of distribution it is spreading in all directions where
sufficient cover is obtainable. But this case differs from the others
very materially, in so far as this bird was formerly a native of
Scotland, and only became extinct during the last century.

However, although there are many examples of undoubtedly successful
introductions by human agency, quite as many, or perhaps more,
unsuccessful ones might be quoted. In fact, it is by no means easy to
establish a species in any new locality. Frequently it happens that the
species seems to be on the increase at first, but then there is a
decline, and after a few years the new plantation has entirely vanished.
In other cases, the species disappears immediately after the
introduction takes place, or lingers on for many years if it receives
special and uninterrupted protection.

It may not be generally known that the English Hare (_Lepus Europæus_)
is not found in Ireland, where the Mountain Hare (_Lepus variabilis_)
alone occurs. Attempts to acclimatise the English species have been made
in a number of places in Ireland, but many of them have been failures,
and not one of them has been a signal success.[4] Similarly, the
endeavour to introduce the French or Red-legged Partridge (_Caccabis
rufa_) into Ireland has met with a like result. According to Dr. Day, it
was tried during the summer of 1869 to naturalise the Sterlet
(_Acipenser ruthenus_) from Russian waters into the Duke of Sutherland's
River Fleet by importing artificially impregnated ova. From one hundred
and fifty to two hundred lively young sterlets are said to have been
turned out, but nevertheless the experiment met with no success. Several
fortunately abortive efforts were also made in British rivers to
establish _Silurus glanis_, a hideous monster of a fish, and quite
unpalatable.

The Natterjack Toad (_Bufo calamita_) has a very local distribution in
the British Islands. In Ireland it is found only along the coast of
Dingle Bay in County Kerry, where it is known among the peasantry as the
Black Frog. There is no doubt about its being indigenous there, and
though it has not spread beyond the very limited area of its habitat,
the Irish climate cannot be said to be unsuited to its existence. Yet it
seems to be extremely difficult to acclimatise it elsewhere, for though
no less than sixty specimens were turned out in Phœnix Park, Dublin,
about forty years ago, none of them were ever seen afterwards. They were
placed in the vicinity of one of the lakes, so as to give them ample
scope for breeding and developing the young, and in surroundings which
were considered eminently suitable at the time.

It has occasionally happened, too, that animals are introduced by
kindly-disposed persons with the view of adding a species to their
fauna, in complete ignorance of their previous existence in the country
where they wished to naturalise them. Thus we are told that in the year
1699 one of the Fellows of Trinity College, Dublin, procured Frog's
spawn from England in order to add that amphibian to the Irish fauna. It
was placed in a ditch in the College Park, whence the species is
supposed to have gradually spread all over the island. This story is
quoted by many writers as the true history of the Frog in Ireland, and
is given as an example of the rapidity with which animals spread.
Unfortunately the would-be introducer seemed unaware that, according to
Stuart's _History of Armagh_, the first Frog which was ever seen in
Ireland made its appearance in a pasture field near Waterford about the
year 1630, that is to say, seventy years before its introduction in
Dublin.[5] But even Stuart was mistaken in supposing that no Frog had
ever been seen in Ireland before, since Giraldus Cambrensis, in his
_Topography of Ireland_, mentions that a Frog was found in a meadow near
Waterford in the year 1187.

Certain British species of vertebrates are generally looked upon as
introduced species, though we cannot trace any record of their first
establishment, and it is quite possible that, though there was local
extinction and subsequent local re-introduction, they are truly
indigenous and may never have become totally extinct. Such are, for
instance, the Rabbit (_Lepus cuniculus_) and the Pheasant (_Phasianus
colchicus_). The latter certainly had become naturalised in England
before the Norman invasion.

But cases of introduction such as those above referred to are by no
means confined to the vertebrates, similar instances among invertebrates
being numerous enough. I am sure every naturalist is personally
acquainted with a good number, and it is hardly necessary that I should
quote in any detail after what has been said on the subject generally.
The two species of snails, _Helix pomatia_ and _Cyclostoma elegans_,
both of which occur in England, and which I had occasion to mention
among those experimented on by Darwin, were turned out in several
suitable localities in Ireland by Thompson, but failed to establish
themselves. The former, according to Mr. Kew, was also introduced into
Scotland and Norway, whilst fifty or sixty specimens were brought to
Petersfield in England, but none of these trials at acclimatisation were
successful. As among vertebrates, a large number of the so-called
successful introductions rest upon insufficient evidence.

When we once more carefully review the evidence as to the undoubted
difficulty attendant on intentional introduction of animals by human
agency, placed as they often were in most suitable localities, we must
feel that accidental introduction cannot play an important rôle in the
making of the fauna of any country. Especially is this the case with an
island fauna. Vertebrates are almost altogether excluded, and
invertebrates must arrive singly as a rule, often stranded on an
inhospitable and unsuitable shore. Their chances of surviving a passage
by sea, of finding suitable food and shelter and a mate in order to
procreate their species, appear to me infinitesimally small. Yet there
may be some such cases. However, I quite agree with Mr. Andrew Murray--a
high authority on geographical distribution--that "colonisation or
occasional dispersal is insufficient to account for the character of
the faunas and floras of oceanic islands; and I believe that the normal
mode in which islands have been peopled, has been by direct continuity
with the land at some former period, or by contiguity so close as to be
equivalent to junction" (p. 15). "That a slight intermixture," he
continues, "due to Mr. Darwin's colonisation, occurs in many (probably
in all) I am ready to admit; and from instances to be afterwards
noticed, I am disposed to reckon the proportions of such intermixtures
in the flora, in the most favourable circumstances, at not more than two
per cent. In the fauna I think it must be much less."

Mr. Murray's views, though they relate only to oceanic islands, are
likewise applicable to continental islands such as our own. I think we
might take the admixture in the British fauna due to occasional,
including human introduction, as amounting to five per cent. It is
better to take a high estimate, so as to include all the species about
whose native land there might be some reasonable doubt. Now of what
importance, after all, is this five per cent.? The remaining ninety-five
per cent. of the species of animals belonging to the British fauna
undoubtedly migrated to these islands in the normal way by land.

It is of great importance, in dealing with the question of the origin of
the British fauna, to thoroughly grasp this conclusion--_that
ninety-five per cent. of the animals have reached us by land_. We can
afford in fact to ignore the five per cent. altogether. It is an
insignificant factor. As regards the botanical aspect of the question,
botanists are quite in accord with the zoologists, and entirely share
their views in the belief of a former land-continuity between the
British Islands and the Continent. "It cannot be denied," says Professor
Blytt (p. 32), "that a plant of one or another species may, in an
exceptional case, migrate, without human assistance, all at once, across
large tracts of land and sea, and that such migration, if operating
during geological periods, might introduce a number of species even into
distant oceanic islands; but when the question is of whole communities
of plants, such as the above enumerated elements in our flora, then such
an accidental and sudden transport across large tracts can only be
conceived to be at all probable in the case of Arctic plants carried by
drifting ice to a bare country without native flora; as to the other
species, we must imagine that the _migration during the gradual change
of climate has proceeded slowly and step by step across connected tracts
of country_. In that manner we may assume that our country has in the
course of time obtained its present covering of plants. Each of the
above-named elements in our flora has doubtless its corresponding
element in our fauna. The fauna and flora of a region stand in relation
of complicated dependence to each other. The animals live on the plants.
The fecundation of the plants takes place in a great degree by means of
insects; their seeds are often scattered by resident birds and
quadrupeds. Everything indicates that _conveyance to small distances is
the rule_, and that sudden and long migration is the exception."

The conviction which has been gained by zoologists and botanists, that
the British Islands once formed part of the Continent, is based on the
present British fauna and flora. The remains, however, of animals which
used formerly to live in these countries, such as the Mammoth, the Irish
Elk, the Cave Bear, and many others, tell us the same tale. They could
not have peopled England by swimming across the Channel, or even by
walking across solid ice, as has once been suggested. Nothing but a
land-connection induced them to explore this country more closely, and
finally to decide on settling there.

The origin of the British fauna will be discussed more in detail in the
third chapter. The methods of investigation adopted, along with a
general scheme of this book, will be found in the next.

The manner in which the origin of the fauna of any particular
continental area can be traced is very similar to that adopted in the
case of an island. Portions of the continent of Europe can be shown to
have been islands in former times. Thus the Crimea, now a peninsula
united to the mainland by the narrow isthmus of Perekop, must have been
an island in comparatively recent times. The absence of a number of
striking and familiar South Russian species of mammals and reptiles
proves this to have been the case. It was probably long after the
appearance of man, though before historic times, that these changes
took place.

We shall learn in the subsequent chapters, that by a careful study of
the fauna and flora the fact can be established, not only of the former
connection of an island with a continent, but also whether such union
existed (geologically speaking) within recent or more remote times. The
better the fauna is known, both recent and fossil, the more precisely
can the period of connection be indicated, and its duration determined.

FOOTNOTES:

[1] The numbers in brackets throughout this work refer to the
page-number in the Bibliography at the end.

[2] A map giving its exact distribution in Ireland will be found on p.
300, and a figure of the slug on p. 298.

[3] The term _endemic_ will be employed throughout this work as applied
to species peculiar to a country and not found elsewhere.
_Autochthonous_ will be used in speaking of a species which has
originated in a country to which, however, it is not peculiar; _e.g._,
the Chamois is an autochthonous Alpine species, but occurs also in the
Pyrenees and Caucasus. An _indigenous_ species is one native to a
country, as opposed to the term "introduced," and is applicable to all
species which have reached it by ordinary migration.

[4] I might refer any one more specially interested in these
introductions to an article on this subject in the _Irish Naturalist_ of
March 1898, by Mr. Barrett-Hamilton.

[5] I should recommend those who are particularly interested in the full
history of the Irish frog to read the notes on this subject contained in
vol. ii. of the _Irish Naturalist_.




CHAPTER II.

PRELIMINARY CONSIDERATIONS.


I intend to give in this chapter a general outline of the subject which
will be discussed in the subsequent ones. This will include a brief
history of the great events, in recent geological times, which have
modified the evolution of the European fauna by the influence which they
have exerted on the course of the successive streams of migration.

The composition of the European fauna is the first item which will have
to be taken into consideration. But not only must the existing species
of animals be dealt with: the extinct ones, too, at least those which
have lived in Europe during late Tertiary times, will be useful for our
inquiries. A knowledge of the past faunas is a most important factor in
tracing the original home of the European animals.

Where a species first originated, whether this was in one or several
places, or, in other words, where it first had its home, cannot be
determined with absolute certainty in the present state of our
knowledge, but as a rule it can be indicated approximately with a fair
amount of precision. In a few instances, species may possibly have had
a dual origin. The majority of naturalists doubt that there are any
such, but it seems to me that almost the same forces may have acted in
different localities on certain forms so as to produce, in very
exceptional circumstances, similar species. The vast majority of
animals, however, have no doubt originated in one locality; or, we might
say, almost all species have but one home.

We may assume that every animal gradually extends its range by
migration, as the result of the natural increase of the species
necessitating a search for fresh feeding grounds. Every species thus
tends to slowly take possession of all the habitable parts of the globe
to which it has access. They would all naturally spread from their
original homes in every direction, unless prevented by an impassable
barrier. We have already learned that to all land animals, the sea acts
as such a barrier. Mountains and rivers act also in a similar way, but
not to the same extent. It is not difficult to understand also that a
forest may be a formidable barrier to a typical inhabitant of the open
country and _vice versâ_, whilst a desert is impassable to almost all
terrestrial organisms. Some species are scarcely affected by climate,
and flourish equally well in the tropics and in temperate or cold
countries; the majority, however, are greatly influenced by it. "No more
striking illustration," remarks Merriam (p. 38), "could be desired of
the potency of climate compared with the inefficiency of physical
barriers, than is presented by the almost total dissimilarity of the
North American Tropical and Sonoran Regions, though in direct contact,
contrasted with the great similarity of the Boreal Regions of North
America and Eurasia, now separated by broad oceans, though formerly
united, doubtless, in the region of Behring Sea."

To return to the composition of the European fauna, we now know
positively that a number of the mammals and birds inhabiting Central and
Eastern Europe are of Siberian origin. How they came, and when, will
form the subject for discussion in Chapter V. At present it will suffice
to mention that in the superficial deposits belonging to the Pleistocene
series of the North European plain have been discovered the remains of
many typical members of the Siberian Steppe-fauna. Some of these, such
as the Saiga-Antelope (_Saiga tartarica_), Fig. 2, still inhabit
portions of Eastern Europe, whilst others have retreated to their native
land. But it might be asked, how is it known that these species did not
originate in Europe, and thence migrate to Siberia? Because if they had
originated on our continent, they would have spread there. They would
have invaded Northern and Southern Europe, and they would probably have
left some remains in Spain, Italy, or Greece. They would also have left
some of their relations in Europe; but all their nearest allies, too,
are Asiatic. Moreover,--and this completes, I think, the proof of their
Siberian origin,--the Pleistocene remains of these animals in Europe
become less abundant, and the number of species likewise decreases, as
we proceed from east to west. With these remains of Steppe animals are
generally associated those of others, which we must also look upon as
Siberian emigrants, such as the Pikas or tailless Hares belonging to the
genus _Lagomys_, the pouched Marmots (_Spermophilus_), and others. Some
of them, as I have mentioned, still inhabit Central and Eastern Europe,
whilst others have a wider distribution on our continent.

[Illustration: Fig. 2.--The Saiga-Antelope (_Saiga tartarica_). (From
Lydekker's _Royal Natural History_, vol. ii. p. 298.)]

This migration must have been an unusually large one. It has been
suggested that the Glacial period had some connection with it, and there
can be little doubt, as we shall see later on, that a change of climate
probably brought about this great Siberian invasion of Europe. But other
causes might tend in the same direction, such as want of sufficient food
after a few years of great increase of any particular species. It is not
known to what we owe the periodic visits of the Central Asiatic
Sandgrouse (_Syrrhaptes paradoxus_), Fig. 3, but certain it is that
immense flocks of these birds invade Europe from time to time at the
present day, just as those mammals may have done in past ages.

[Illustration: Fig. 3.--Central Asiatic Sandgrouse (_Syrrhaptes
paradoxus_).]

The _Siberian_ migrations will be spoken of in the subsequent pages, as
the Siberian element of the European fauna. These migrations, however,
are not the only ones which reached Europe from Asia. The sixth chapter
deals with migrations which have influenced our fauna far more than the
Siberian. The latter did not last long, nor did they affect the whole of
Europe. But what I may call the _Oriental_ migrations spread to every
corner of Europe and certainly lasted throughout the whole of the
Tertiary Era. The Oriental element came probably from Central and
Southern Asia, and in its march to Northern Europe it was joined by
local European migrations. For on our continent, too, animals originated
and spread in all directions from their centres of dispersal. A separate
chapter has been given to the _Alpine_ fauna, and another to that of
South-western Europe, which will be known by the name of the
_Lusitanian_ element. Finally, animals have also reached us from the
north, and in the fourth chapter the history of that remarkable
migration will be fully discussed under the title of the _Arctic_
element of the European fauna.

It is generally believed that Africa played an important rôle in the
peopling of our continent, but this is quite a mistake. The eminent
Swiss palæontologist Rütimeyer was quite right in saying (p. 42) that it
is much more probable that Morocco, Algeria, and Tunis were stocked with
animals by way of Gibraltar, and perhaps also by Sicily and Malta, from
Europe, than the South of Europe from Africa.

I have already referred to what are known as "centres of dispersion" of
animals, but before continuing to explain the general outline of this
book, it will be necessary to make a few additional remarks on the
subject.

Since every animal naturally tends to spread in every direction from its
original home--that is to say, from the place of its origin--the latter
should correspond with the centre of its range. And in any particular
group of animals the maximum number of species should be formed in the
area or zone which is the centre of its distribution. In the great
majority of instances this is probably the case, in the higher animals
perhaps less so than in the lower; still the rule must hold good that
the original home of a species is generally indicated by the centre of
its geographical distribution.

Take for example our familiar Badger (_Meles taxus_). It inhabits
Europe and Northern Asia. It is absent apparently from many parts of
Central Asia, but it appears again farther south in Palestine, Syria,
Persia, Turkestan, and Tibet. West Central Asia would be about the
centre of its range. That this corresponds to its place of origin is
indicated by the fact that the only three other Badgers known--viz., _M.
anakuma_, _M. leucurus_, and _M. albogularis_--are confined to Asia. If
we examine the fossil history of the genus, we find that the two most
ancient instances of the existence of Badgers have been discovered in
Persia, where _M. Polaki_ and _M. maraghanus_ occur in miocene deposits.
The latter had migrated as far west as Greece in miocene times; no other
trace of the Badger, however, is known from Europe until we come to the
pleistocene beds. There are a good many cases known among mammals where
the centre of dispersion would indicate to us a similar origin. On the
other hand, there may be no fossil evidence of the occurrence of a
species, or of its ancestors, in Asia, whilst such has been discovered
in Europe. I think, however, that the present range of a species forms a
safer criterion for the determination of its original home, as the
Asiatic continent is still practically unworked from a palæontological
point of view. In a letter which I received from Professor Charles
Depéret, he advocates the view that the wild Boar (_Sus scrofa_) is
probably of European, and not, as I maintained (_c_, p. 455), of Asiatic
origin; because there seemed to be a direct descent from Hyotherium of
the middle miocene of Europe, through the upper miocene Pig of the
Mount Lebéron (_Sus major_) and of Eppelsheim (_Sus antiquus_), and the
pliocene Pigs of Montpellier (_Sus provincialis_) and of the Auvergne
(_Sus arvernensis_). No doubt this appears rather a strong case in
favour of the European origin of the wild Boar, but although the
Tertiary strata of Asia, as I remarked, are as yet little known, a
number of fossil pigs are known from India, Persia, and China, the
oldest being the upper miocene Persian Pig (_Sus maraghanus_). Pigs are
therefore as old in Asia as in Europe, and as a direct intercourse
between the two continents probably never ceased since miocene times, it
is not surprising that this genus should occur in both. Even if the
genus had its origin in Europe, it is quite possible that in later
Tertiary times, the active centre of origin was shifted to the
neighbouring continent, and that henceforth many new species issued
forth from Asia, some of which may subsequently have been modified on
reaching our continent. The wild Boar (_Sus scrofa_), however, to judge
from its general range, I must look upon as merely an immigrant in
Europe. I have no doubt that it originated somewhere in Asia, probably
in the south.

The view I take of the origin of our European Boar is also supported by
Dr. Forsyth Major's recent researches. He was led to a re-investigation
of the history of the Pig while examining a large number of fossil
skulls in the Museum at Florence, and came to the conclusion that only
three or four species of recent wild pigs can be clearly distinguished
(_b_, p. 298). One of these, viz., _Sus vittatus_, he thinks, is
traceable in slight modifications from Sardinia to New Guinea and from
Japan to South Africa. The centre of distribution of this species lies
in Southern Asia. Of the three remaining species, two, viz., _Sus
verrucosus_ and _S. barbarus_, are entirely confined to the great
islands which form part of the Malay Archipelago. Finally, _Sus scrofa_,
our Central European wild Boar, is so closely related to _S. vittatus_
that the Sardinian Boar might be looked upon as a variety of either the
one or the other. At any rate, Dr. Major recognises clearly in _Sus
vittatus_ the representative of the ancestral stock of which _Sus
scrofa_ is a somewhat modified offshoot.

The fauna of Europe consists, as I have mentioned, to a large extent of
immigrants from the neighbouring continents. This is especially
noticeable among the higher animals. When we come to the lower, such as
the amphibia, we find a larger percentage, and among the land mollusca
the great majority, to be of European origin. The foreigners are, as we
learned, called Orientals, Siberians, and Arctics. For the sake of
convenience, only two of the great European centres of origin have a
chapter devoted to themselves, namely, the Alpine and the Lusitanian
centres. There is another, however, of almost equal importance which
lies in the east.

In the British Islands there is only an exceedingly small and
insignificant group of species which are peculiar, and which we may
consider to have had their origin there. Almost the whole of the British
fauna is composed of streams of migrants which came from the north,
south, and east, though many of these immigrant species have since their
arrival been more or less distinctly modified into varieties or local
races.

The eminent French conchologist Bourguignat (_a_, p. 352) was of opinion
that, as far as terrestrial mollusca were concerned, there are in Europe
three principal centres of creation or dispersion--all situated in
mountainous countries and not in the plains. He distinguished the
Spanish, Alpine, and Tauric centres, and believed that almost all
species known from Europe had originated in one of these three, and that
each of them possessed quite a distinct type of its own. This theory
seems to agree very well with the facts of distribution. Let us take,
for instance, the genus _Clausilia_, a pretty turret-shaped snail, which
abounds on old ruined walls. Only two species, viz., _Cl. laminata_ and
_Cl. bidentata_, are met with in Ireland. In England we find the same
species with the addition of two others, _Cl. biplicata_ and _Cl.
Rolphii_. Crossing over the Channel to Belgium, these four species occur
again, and also several others not known in England. In Germany the list
of _Clausiliæ_ mounts up to twenty-five species, including all those
found in the British Islands. As we proceed eastward the number of
species of this genus increases steadily, and when we reach the Caucasus
or the Balkan Peninsula the conchologist is able to make a collection
of several hundred different kinds, whilst farther east again they
diminish. This clearly indicates there is in South-Eastern Europe a
powerful centre of creation of _Clausiliæ_, from which the species have
spread all over Europe. But it is by no means certain that this centre
was always in our continent, for in South-Eastern Asia and the Malay
Archipelago _Clausiliæ_ increase once more. It is interesting to note,
however, that almost all these eastern forms belong to the sub-genus
_Phædusa_ (_vide_ Boettger), which had only been known as a fossil genus
from a few species in the Eocene and Oligocene of Southern Europe. The
first centre of origin, therefore, may possibly have been in Southern
Asia, and in these early Tertiary times a second centre may have become
established in Southern Europe from which the sub-genus _Garnieria_ went
eastward, _Macroptychia_ southward, and _Nenia_ westward across the
Atlantic to South America. Only a few remnants of these primitive
_Clausiliæ_ are now left in Europe, such as the interesting _Cl.
(Laminifera) Pauli_.

As an example of a genus which has its centre of distribution in
South-Western Europe we might take that to which our common brown garden
slug belongs, viz., _Arion_. Dr. Simroth, who was the first to point out
that the species of _Arion_ had spread over our continent from
South-Western Europe (p. 5), is inclined to the belief that the
_Arionidæ_ had originated on the old land-bridge between Europe and
North America, which is generally known by the name of "Atlantis." From
this a branch went westward to the New World and another eastward as far
as Southern Asia, but _Arion_ and a number of other genera are more or
less confined to South-Western Europe. Only a few species of _Arion_
have a wide range in Europe, one of them, _A. subfuscus_, crossing the
borders of our continent into Siberia. In the British Islands and in
Western Germany, which are about equi-distant from the supposed creative
centre of the genus, there are found five species. In France six or
seven species are met with, and in Spain and Portugal about ten. Towards
the east, _Arions_ diminish in number. This genus, therefore, forms part
of a migration which I have designated as "Lusitanian" from _Lusitania_,
the name applied by the Romans to what we now call Portugal. Another
genus of slugs, _Geomalacus_, is interesting from the fact that one
species occurs in the British Islands, being otherwise confined to the
Lusitanian province. Parmacella, a slug-like animal bearing a tiny shell
at the extremity of its tail, has probably likewise had its origin in
this part of Europe. All this, however, will be more fully referred to
in the seventh chapter, which deals with the Lusitanian fauna.

As regards the Alpine centre of origin, Dr. Kobelt considers three
groups of mollusca as especially characteristic of the Alps, viz., the
sub-genus _Campylaea_ of the great and widely-spread genus _Helix_, and
the genera _Pomatias_ and _Zonites_. The latter, which is not to be
confounded with our British _Hyalinia_ (formerly united with _Zonites_),
does not extend very far south or north of the Alps. There may be others
too, which owe their origin to these mountains, but most of the
terrestrial mollusca are exceedingly ancient, and many genera have
existed long before the Alps had made their appearance above the surface
of the early Tertiary seas. It should be remembered that _Hyalinia_ and
_Pupa_, both British genera, are known from carboniferous deposits in
forms which closely approach those living at the present day, and in
these and a great number of other instances, it is quite impossible to
determine the original home of the genus.

This little digression on centres of dispersion will help us to
understand in what manner the indigenous element of the European fauna
joined in with the alien members as they arrived in our continent. The
species confined to South-Eastern England need not necessarily have come
to us from Eastern Europe or Siberia. Alpine species spread northward
probably at the same time as the Siberian animals went westward. An
Alpine form may therefore have joined a batch of the latter and entered
England with them. Even a Lusitanian animal may have mingled with these
migrants, so that all three elements may occur together in one locality.

But these are exceptions. The migrations have, as a rule, not joined to
any great extent; indeed, all those naturalists who have carefully
examined the problem of the origin of the European fauna, have felt
that it was composed of elements which arrived at different times.

The great Russian naturalist, the late Professor Brandt, distinguished
five phases in the history of the Eurasian mammalian fauna (pp.
249-254). During the first phase--an uncertain period of long
duration--the mammals held intact their position in the northern half of
Asia. The Mammoth, the Hairy Rhinoceros, Bison, Musk Ox, Wild Sheep,
Reindeer, and perhaps Tigers, Hyænas, etc., lived then, with numerous
peculiar Rodents, under such climatic conditions, according to Brandt,
that they were able to extend their range along with tree vegetation to
the extreme north of the Asiatic continent. This, he thinks, seems to
have been the case especially with the Reindeer, Mammoth, Rhinoceros,
and Musk Ox. The second phase was characterised by the dispersion of the
Northern Asiatic mammalian fauna towards Central, Southern, and Western
Europe, and this period lasted until the complete extermination of the
Mammoth. The third phase dates from the time when the Mammoth and the
Hairy Rhinoceros had become extinct, whilst the fourth commenced with
the disappearance of the Reindeer in Europe, and terminated when the
Wild Ox in the feral state had become unknown. Finally, the last phase
constitutes the present time. Lartet held similar views, and also
believed that Europe was peopled by successive migrations from Asia.

Botanists have worked at the problem of the European flora much more
systematically, and our knowledge of the origin of that flora has been
greatly increased within the last twenty years, chiefly by the
researches of Professor Engler. More recently, detailed studies have
been made in Scandinavia by Professor Blytt, in the Alps by Dr. Christ
and Mr. Ball, in Germany by Professor Drude, Dr. Schulz, and many
others. Dr. Schulz (p. 1) is of opinion that the great majority of the
European plants have either migrated to or have originated in our
continent since the beginning of the Pliocene epoch, and that the
original home of the immigrants must be looked for in Asia and in Arctic
America. From the latter an almost uninterrupted migration must have
taken place during the greater part of Tertiary times up to the
commencement of the Pliocene epoch, partly over a direct land-connection
with Europe by way of Greenland, Iceland, and the Faroes, and also _viâ_
Spitsbergen, Franz Josef Land and Novaya Zemlya, and partly by an
indirect one across the Behring Straits between Alaska and Kamtchatka.

A good deal of work still requires to be done before zoologists have
acquired the same intimacy with the European fauna as botanists have
with the flora. However, the view that our animals all come from Asia,
as was long ago believed, has been abandoned for some time. The first to
bring under the notice of naturalists the hypothesis, that there must
have been two distinct migrations of northern animals to Central
Europe--one from the north, and another from the east--was the late Mr.
Bogdanov. The Arctic species, of which remains have been discovered in
the Pyrenees--namely, the Reindeer, Arctic Hare, Willow Grouse, etc., he
thought had nothing to do with those which invaded Europe from Siberia
during the Glacial period. He maintained that the former had quite a
distinct origin, and came from Scandinavia (p. 26).

As I shall deal with this problem more fully in a subsequent chapter, I
need only mention that I fully agree with the view expressed by Mr.
Bogdanov that two distinct migrations of northern species to Central
Europe can be traced.

No one, I think, has done more in fostering a careful study of the
migrations of animals than our distinguished geologist Professor Boyd
Dawkins. He did not follow Bogdanov in distinguishing two Arctic
migrations; however, he did more in constructing a very ingenious chart
(_a_, p. 111) representing the geography of Europe during the last and
most recent geological epoch--the Pleistocene--and indicating on it the
probable extent, during that time, of an eastern and a southern
migration of mammals. The map is very instructive, and is the first ever
published giving a clear idea of a southern and an eastern migration to
Europe. He believed that the migration of the southern mammals
northward, took place conjunctly with the westward movement of the
eastern species. Having once reached Europe, the southern species are
supposed to have passed northward in summer time, whilst the eastern
forms (he calls them northern) would swing southwards. The two
migrations would thus occupy, at different times of the year, the same
tract of ground (_a_, p. 113). From the mingling of the remains of the
Hyæna with those of the Reindeer and Hippopotamus in the Kirkdale
Cavern, he infers that the former preyed upon the Reindeer at one time
of the year, and on the Hippopotamus at another. He argues that in such
a manner might be explained the curious mixture of northern and southern
types which we find in the British pleistocene and in cave deposits.

Besides mammals, the only European animals which have received some
attention with a view to a study of their origin, are the Butterflies
and the Land-Snails. The entomologists who have taken up the problem
have in so far scarcely produced satisfactory results, as they all
seemed to be bound down to the hypothesis that practically all the
butterflies had been destroyed in Europe during the Glacial period.
Hofman, in his interesting little work, comes to the conclusion (p. 50),
that only in Greece and Spain could a small remnant of the butterflies
have survived the extreme rigours of climate. Greece was at that time
connected with Asia Minor, and Spain with North Africa; and the author
supposes that the semi-alien fauna inhabiting these tracts was mainly
responsible for the re-stocking of Southern Europe, but that the main
mass of our butterflies are post-glacial Siberian immigrants.

The work published by Messrs. Speyer deals only with the origin of the
Central European Butterflies. The period during which our European
species originated is not specified, but the authors believe that they
had their home either in Southern Russia or Central Asia. The fact that
the number of butterflies decreases very considerably as we proceed
north-westward in Europe appears to them to substantiate these views.
The apparent dislike evinced by butterflies to the damp Atlantic Coast
climate, they think, clearly indicates that they had originated in a dry
and more continental climate. The history of the North European
Butterflies and Moths has been carefully described by Mr. Petersen. He
adopts Hofman's theory as to the almost total extinction of the
Lepidoptera in Europe during the Glacial period. The chief immigration
to Europe after that period is, he thinks, Siberian.

At first there appeared species which belonged to a cold climate, and
which now live in elevated regions; then came forms suited to a milder
climate, which established themselves on the north-easterly slopes of
the Alps. The most recent addition which our continent has received from
Siberia is, according to Mr. Petersen, the present Scandinavian fauna.
Scandinavia has obtained a larger number of species than the European
plain, because to this last migration were added such as prefer a
northern or Alpine climate.

As a contribution to the history and composition of the European fauna,
by far the most important work ever published is that of Dr. Kobelt, the
eminent German conchologist. Whilst the researches into the origin of
the Lepidoptera, above described, have been marred by the prevalent
prejudice as to the deleterious effects of a glacial climate on the
butterflies, the present author boldly works out the problem on
independent lines. He shuns theories and speculations almost altogether.
His great work, as yet practically unknown, the result of a lifetime of
the most painstaking labour, ranks among the most important
contributions to zoogeography. I shall have frequent occasion to refer
to it throughout these pages. Meanwhile some of his more remarkable
conclusions may be mentioned. "Comparing all classes of animals as to
their zoogeographical importance, the highest rank must undoubtedly be
accorded to the land-snails" (i., p. 7). "The Pleistocene, and with it
the land and fresh-water molluscan fauna of the present day has been
gradually evolved from the Tertiary one, and its roots can be traced
through the Cretaceous to the Jurassic epoch. During the whole of that
time no sudden appearance of a new fauna can be demonstrated. Quite
slowly, step by step, the Cretaceous is succeeded by the Tertiary fauna,
and one after the other of the characteristic palæarctic genera
appear--first the fresh-water, then the land forms" (p. 141). "The
division of the North Alpine from the South Alpine fauna must be older
than the Glacial period; and the present Central European fauna had
already become developed from the Pliocene _in all its details of form
and distribution_ before the commencement of the Ice Age" (p. 162). "We
must draw the conclusion from the preceding remarks, that the present
(palæarctic) molluscan fauna in its distribution is older than the
Glacial period, and that the latter produced merely a retreat of the
fauna from the most inhospitable regions of Europe with a subsequent
re-immigration, but did not cause its destruction" (i., p. 169).

A few attempts have also been made by naturalists to trace the origin of
the fauna of some smaller European areas. Thus Rütimeyer, in dealing
with the mammalian fauna of Switzerland, remarks (p. 31) "that it seems
certain that, in spite of many local disturbances, the continuity of
generations was never interrupted throughout the whole of the Tertiary
period until the present day."

An even more interesting memoir is that of Mr. Köppen on the origin of
the Crimean fauna. It is only recently, according to this author, that
this peninsula has become connected with Southern Russia. And it is for
this reason that the Squirrel and a number of other animals, and also
plants, present in Russia, are absent from the Crimea. Originally the
latter probably formed a westward continuation of the Caucasus, and at
that time it was surrounded by the sea on all other sides. "Much later,"
he continues, "after and in consequence of a local subsidence, the
country between the Caucasus and the Crimea became interrupted. The
latter existed for a long time as an island, and only much later, in
recent geological times, did it become united with Southern Russia by
means of the isthmus of Perekop."

There is, on the whole, a great diversity of opinion as to how the
European fauna has originated; however, except in Dr. Kobelt's work, no
attempt has hitherto been made to collect together all the available
information, and to include in the inquiry more than one class of
animals. The little work which I venture to bring before the public will
not by any means exhaust the subject, nor is our knowledge of the
European fauna sufficient to give more than a mere sketch of many of the
animal groups mentioned. As we have learned in the introduction,
different classes of animals are not all of equal importance in
indicating the changes which have taken place in the distribution of
land and water. While Dr. Kobelt is of opinion that the land-snails are
by far the most important in such an inquiry, Mr. Lydekker believes that
mammals afford the safest and truest indications of such changes. Mr.
Beddard puts in a claim for earthworms, as even a narrow strait of
sea-water forms an insuperable barrier to their dispersion. Dr. Wallace
agrees with Mr. Lydekker, and goes so far as to say (p. 74) that
"whenever we find that a considerable number of the mammals of two
countries exhibit distinct marks of relationship, we may be sure that an
actual land-connection, or at all events an approach to within a very
few miles of each other, has at one time existed." Besides the groups
referred to, I claim that particular attention should be devoted to
Amphibia, which, contrary to Wallace, I hold do not possess special
facilities for dispersal; and also to spiders and to all wingless
animals leading a subterranean life, such as some of the wood-lice,
planarian worms and apterous beetles.

A thorough knowledge of the changes in the distribution of land and
water is desirable in order to appreciate the extent and variations of
former migrations. A study of the British fauna, for example, teaches us
that the British Islands were once connected with one another and with
the continent of Europe between England and France. It was Professor
James Geikie, I believe, who first pointed out, many years ago, that the
area now covered by the Irish Sea was formerly in all probability a
fresh-water lake. This had its outlet at the southern extremity in the
form of a stream into which most likely flowed the smaller rivers from
the south-east of Ireland, and which was joined from the east by the
Severn, and finally debouched into the Atlantic (Fig. 4). The range in
the British Islands of those species which have migrated to them from
the south, indicates that whilst the Atlantic Ocean had gradually crept
up and flooded the area between Ireland and Wales, and had turned the
fresh-water lake into a bay, communication between Scotland and Ireland
was still possible. The occurrence of many Scandinavian species in
Scotland which are absent on the continent of Europe, indicates that
these two countries also were united formerly. Most geologists hold that
such a connection, if it existed, must have broken down in Pliocene
times. Professor Judd, however, has expressed his belief (p. 1008) that
it still existed until after the appearance of man in Northern Europe,
and that our forefathers might have been able to walk dry foot from
Scotland to Norway.

[Illustration: Fig. 4.--Map of the British Islands and surrounding area
at a time when the earlier members of the southern migration reached
England. (Only some of the rivers have been indicated. The shaded parts
represent water, the light land.)]

I shall also show on distributional evidence, in the fourth chapter,
that until recent geological times Scandinavia was continued northward,
by way of Bear Island, with Spitsbergen and probably Franz Josef Land,
which islands again were joined with North Greenland and Arctic North
America, and that the polar fauna and flora were able to spread on this
land-connection to both America and Europe.

That Gibraltar was connected with Morocco, and Sicily with Southern
Italy and Greece on the one hand, and with Tunis on the other, is more
generally recognised; whilst Professor Suess has shown (vol. i., p.
442), on purely geological grounds, that the Egean Sea was dry land up
till quite recently--certainly, he thinks, till after the appearance of
man. This supposition enables us to understand, as will be more fully
discussed in the sixth chapter, how the Oriental fauna entered Europe.
Such minor zoogeographical problems as the occurrence of the Wild Goat
of Asia Minor (_Capra ægagrus_) on the islands of Crete and on some of
the Cyclades now almost explain themselves. The Sea of Marmora is
probably a modern formation, so that Asia Minor extended not long ago
beyond the Turkish capital, but Dr. Kobelt believes that an arm of the
Black Sea communicated up till recent times along the lower course of
the Maritza with the Gulf of Saros. It can be shown also that Sardinia
and Corsica formed part of the continent of Europe, and that their
present fauna and flora reached them by migration on land.

The Russian naturalists, Brandt and Köppen, believed that at no very
distant date a sea extended right across Eastern Russia from the Caspian
to the Arctic Ocean, whilst Professor Boyd Dawkins expressed himself in
very similar language as follows (_c_, p. 35): "Before the lowering of
the temperature in Central Europe the sea had already rolled through the
low country of Russia, from the Caspian to the White Sea and the Baltic,
and formed a barrier to western migration to the Arctic mammals of
Asia." These naturalists based their opinions on distributional
evidence, but additional facts will be brought forward in the fifth
chapter to substantiate these views.

These are some of the more important geographical events which will be
dealt with in detail in the subsequent chapters in connection with the
history of the migrations of the European fauna.

A separate chapter has been devoted to the British fauna and its origin,
since it plays a very important part in the evolution of that of our
continent. So essential is a thorough knowledge of this fauna, that I
think it would be difficult to understand, without it, the main
features of the great migrations; and I have before now expressed the
opinion that the British fauna forms the key to the solution of the
problem of the origin of European animals. We know that our British
species came to us by land--at least the bulk of them. But we want to
know what direction they came from, and at what time they arrived. When
Ireland became disconnected from Great Britain, and the latter from
Scandinavia and France, is another interesting problem. Professor Boyd
Dawkins has indicated to us a method of the special line of research to
meet such inquiries. "The absence," he says (_b_, p. xxix), "of the
beaver and the dormouse from Ireland must be due to the existence of
some barrier to their westward migration from the adjacent mainland, and
the fact that the Alpine hare is indigenous, while the common hare is
absent, implies that, so far as relates to the former animal, the
barrier did not exist."

Many members of the great Siberian invasion reached England, but Ireland
remained entirely free from these migrants. The assumption therefore
seems not unreasonable, that the latter country at the time of their
arrival was no longer joined to England. The great bulk of the Irish
fauna is composed of Lusitanian, Alpine, and Oriental immigrants, and
there is besides a distinctly Arctic or North American element. All
these, of course, must have established themselves in Ireland before
the Siberian fauna set foot in England, since it has been shown that a
continuous land-surface was necessary for their migration. Owing to the
perfect preservation of the remains of the Siberian migrants in recent
continental deposits, the history of that migration can be clearly
followed, and it is possible even to determine the date of its arrival
in England--in geological language at any rate. The time of the
colonisation of Ireland can be thus approximately fixed as having taken
place at a period prior to the arrival of the Siberian migrants in
England.

All those who have seriously studied the problems presented by our
British fauna--notably the late Professor Forbes, and more recently Mr.
Carpenter and myself--are agreed that the Lusitanian element is the
oldest, and that the newest is that which has come to us from the east.

The sequence of events in the British Islands was probably as
follows:--The first comers were the members of that fauna which issued
from South-western Europe; then came the Alpine, and at the same time
probably the Arctic and the Oriental; and finally the Eastern or
Siberian. The migrations of all but the last continued, uninterruptedly,
for very long periods.

The study of these migrations has convinced me that, though climate was
a powerful factor in the evolution or history of the European fauna, the
geographical changes which took place on our continent in later Tertiary
times exerted a yet stronger influence. The principal climatic
disturbance is generally supposed to have been the so-called "Ice Age."
So firmly rooted is the conviction, among naturalists of the present
day, of the enormous destruction which this period produced on our
European fauna, so that all animal life practically disappeared from
large areas of our continent, that it is desirable that we should now
shortly review the history of that remarkable period in order to
ascertain in how far these views are corroborated by facts. Frequent
reference, moreover, will be made throughout this work to the theories
connected with the Glacial period.

It has been stated by an eminent geologist that during part of the
Glacial period the climate was such that neither plants nor animals
could have existed in the British Islands. If that had been so, it is
evident that very few organisms could have even survived in France,
though a number of Arctic species might have dragged on an existence in
Southern Europe. At any rate, on the return of more genial conditions,
the Arctic species would undoubtedly have been the first to gain
admission to the British Islands, to re-people the arid wastes. Our
supposition that the Lusitanian element in the British fauna is the
oldest would therefore be wrong. From early Tertiary times onward, the
climate of Europe, which was then semi-tropical, gradually became more
and more temperate; until finally the Ice Age or Glacial period arrived,
during which, according to Professor J. Geikie--one of our highest
authorities on this subject--a great part of Northern Europe became
practically uninhabitable owing to the severity of the climate.

To enable us to judge better of the true value of the many hypotheses
which have been advanced to account for this supposed extraordinary fall
of temperature during the "Ice Age," we must compare the views of other
authorities with the one just quoted. I do not propose to discuss the
causes which have led to the production of the Glacial period--those
interested in these questions should consult the writings of Dr. Croll,
Professor J. Geikie, Professor Bonney, Mr. Falsan, and others--but
merely to give the climatic aspects from a physical, zoological, and
botanical point of view.

According to Professor Penck (_a_, p. 12), the nature of the glacial
climate can be determined by comparing the snow-line of the Glacial
period with that of the present day. The position of the snow-line is
dependent on two climatic factors--viz., precipitation and temperature.
We know the height at which snow must have lain permanently during the
Glacial period, or during the maximum phase of glaciation. If the Ice
Age had been produced solely by an increase of snowfall, as has been
suggested, Professor Penck tells us that then it must have snowed three
or four times as much as it does now. But he does not adopt the view
that the Ice Age is due to an increase of snowfall alone. His
calculations, based upon the height of the snow-line, tend to show that
a general decrease of temperature to the extent of from 4-5 degrees
Centigrade (all other atmospheric conditions remaining the same as now)
would be sufficient to give us back the Glacial period.

Professor Neumayr (p. 619) adopted a similar principle in determining
the temperature which prevailed in Europe during the Glacial period.
Snow now lies in the Pyrenees 1000 metres higher than it did then, 1,200
metres higher in the Alps, and 800 metres higher in the Tatra mountains.
Since the temperature in Central Europe decreases by half a degree
Centigrade for every 100 metres of elevation, it follows that if the
glacial phenomena had only been brought about by a decrease of
temperature without an increase of moisture, we should have had a
reduction of temperature during the Glacial period of six degrees
Centigrade in the Pyrenees, of seven degrees in the Alps, and of four in
the Tatra mountains. The general lowering of the temperature of Europe,
says Professor Neumayr, could not have amounted to more than six degrees
Centigrade. Moreover, he is of opinion that the very low snow-line in
the British Islands proves that even during the Ice Age a comparatively
mild climate prevailed there, and that the climatic conditions
generally, in the different parts of Europe, were relatively about the
same as they are now.

Professor J. Geikie does not give us his views as to the temperature of
the Glacial period, but he maintains that a lowering of the temperature
is evinced not only by the widespread phenomena of glaciation, but by
the former presence in our temperate latitudes of a northern fauna and
flora.

Mr. Charles Martins, who based his calculations on the temperature
during the Glacial period on the glaciers of Chamounix, concluded that
it only needed a lowering of the temperature to the extent of four
degrees Centigrade to bring the glaciers down to the plain of Geneva,
and in fact give us back the Glacial period. It need not surprise us,
therefore, that the French geologist, Mr. Falsan, the author of _La
période glacière_, is of opinion (p. 230) that the mean annual
temperature of France during the Glacial period was approximately from
6-9 degrees Centigrade, perhaps more. Close to the immense glaciers of
the Rhone, it might have been about six degrees. This is the actual mean
annual temperature of the South-west of Sweden and Norway, or the North
of Scotland.

Although all these investigations tend to show that the climate of
Europe during the Glacial period was by no means so severe as we are
often led to believe, yet there exists also a school of geologists who
maintain there was actually a higher temperature than at present. The
inconsistency of mentioning heat in connection with ice and snow is more
apparent, however, than real, for we must remember Tyndall's original
remark on this subject. It is the snow, he says, which feeds the
glaciers. But the snow comes from the clouds, and these again originate
from the vapours which the sun causes to be absorbed from the ocean.
Without the sun's heat, we should have no water vapour in the
atmosphere; without vapour, no clouds; without clouds, no snow; without
snow, no glaciers. The ice of glaciers, therefore, owes its origin
indirectly to the sun's heat. It has been supposed that if the sun's
heat diminished, larger glaciers would form than those existing to-day,
but the diminution of the solar heat would infallibly reduce the amount
of water vapour in the air, and would thus stop the very source of
glaciers.

Mr. Falsan even admits that without a change of the mean annual
temperature (p. 201) of Europe, the central portions of our continent
might at this period have enjoyed an insular climate. This more equable
and humid climate could, within certain limits, favour the development
of the ancient glaciers by increasing the snowfall and slackening the
summer rate of melting.

It seems evident then, according to these views, that with a
comparatively slight change of the atmospheric conditions in the British
Islands, we might have glaciers back again on all our highest mountain
ranges in England, Scotland, and Ireland. But a widespread belief seems
to prevail that the presence of glaciers implies a very low temperature.
Snow and ice, however, are formed as soon as the temperature falls below
freezing point; it does not matter whether there be 1 or 20 degrees of
cold. Winters with a few degrees of frost will be just as favourable for
the growth of glaciers as winters with the most severe cold.

Let us now see what the fauna and flora, as far as we know it, tell us
of the climate of the Glacial period. At the very outset of our inquiry
we are confronted with one very serious difficulty in the problem, and
that is the supposed occurrence of inter-glacial mild phases alternating
with colder ones during the Ice Age. At first, when traces of a
temperate flora and fauna were discovered intercalated between two
layers of boulder clay, their presence was explained by the supposition
of a mild inter-glacial period. The famous Forest-bed on the east coast
of England was also pronounced to be an inter-glacial deposit, though
not coming precisely under this definition. In a few places one such bed
was found, in some two or more, and in others none at all. Professor
James Geikie discovered the evidences of no less than five of such
inter-glacial epochs (p. 612) in Europe. Lest a reader of that author's
remarkable work on the Ice Age might carry with him the idea that his
hypotheses had met with general acceptance, a few quotations from almost
equally high authorities on glacial matters will be useful. "That the
glaciers," remarks Professor Bonney (p. 245), "were liable to important
oscillations seems to be proved, but whether the evidence suffices to
establish inter-glacial epochs, in the usual sense of the words, is more
doubtful. When the snow-fields, as in the Alps, were much more
extensive than they are at present, the glaciers which radiated from
them would be more sensitive to minor climatal change. Even now they
oscillate considerably. But during a Glacial epoch, an inch, either more
or less, of precipitation might mean a considerable advance or retreat
of the ice in the lowlands." French geologists look with even less
favour on Professor Geikie's theories. Mr. Falsan (p. 212) says that he
agrees with Messrs. Favre, de Saporta, Lory, de Mortillet, Desor, de
Lapparent, Lortet, Chantre, Benoit, Fontannes, Depéret, and many other
geologists, that there was only a single Glacial period, which,
according to each particular region, might be divided into several
phases, or into their equivalents--viz., one or more extensions of the
ancient glaciers. But, on the whole, the view that there was at least
one inter-glacial phase in the Glacial period meets with more general
acceptance among geologists, I think, though the other opinion agrees
much better with the nature of the fauna and flora as it has been
revealed to us from the pleistocene deposits.

The occurrence of the remains of such arctic species of mammals as the
Musk-Ox, Arctic Fox, Glutton, Lemming, and many others in these
deposits, is frequently held up to us by geologists as a proof of the
prevalence of an arctic climate while these beds were laid down. And
indeed this appears at first a most satisfactory explanation of the
phenomenon. But we must not judge the climate of Europe by their
presence alone. As I shall explain more fully in Chapter V., these
species invaded Europe owing to two circumstances. Firstly, because the
climate of Siberia was becoming colder, necessitating a southward
movement, with a consequent over-population in a reduced area; secondly,
because a new short route to Europe had been opened up for them about
the same time (see p. 221). An invasion of Europe therefore took place
from east to west. Similar invasions occur even at the present day,
though not caused by a change in our climate, for every now and then
immense flocks of the Siberian Sandgrouse emigrate to our continent. The
mammalian migrants referred to are not to be looked upon as constituting
the whole of our fauna at that time. Europe had a fauna of its own, and
these invaders merely mingled with our animals. There was, no doubt, a
keen struggle for existence, as the result of which the weaker in many
cases succumbed. The hypothesis, however, that these Siberian migrants
occupied an empty continent, forsaken by its pre-glacial inhabitants, is
not supported by any facts.

All those who have investigated the pleistocene fauna have been struck
by the extraordinary mixture of northern and southern types of animals.
Professor Dawkins attempted to explain these facts by the supposition
(p. 113) that "in the summer time the southern species would pass
northwards, and in the winter time the northern would sway southwards,
and thus occupy at different times of the year the same tract of ground,
as is now the case with the elks and reindeer." "In some of the
caverns," he continues (p. 114), "such as that of Kirkdale, the hyæna
preyed upon the reindeer at one time of the year, and the hippopotamus
at another."

A similar mingling of northern and southern faunas has also been
observed in France. Mr. Falsan tells us (p. 236), that the remains of
the mammals gathered and determined by Lartet and Gaudry belong partly
to species which have been wrongly regarded as indications of a severe
climate, and partly to such as are accustomed to a relatively mild
temperature. In several localities in France, viz., at Levallois, St.
Acheul, and Arcy, the remains of the Hippopotamus have occurred together
with those of the Reindeer; whilst, according to Sir H. Howorth, the
Lion has been found together with northern Voles at Bicêtre, near Paris.
It is stated by the same authority (p. 115) that much the same
conditions exist in Germany. "The lion and the spotted hyæna, the
mammoth and rhinoceros, were found with the marmot, the suslik, the
lemming, the pica, and the reindeer." At another locality near Thiede,
remains of the Mammoth, woolly Rhinoceros, Horse, Ox, Reindeer, Arctic
Fox, Lemming, and Pica are met with in the same deposit. In quoting the
presence of these northern animals in Europe as evidence of an arctic
climate, we commit a fatal mistake. Indeed, breeders of animals and
those acquainted with zoological gardens know perfectly well that it is
much easier to keep a northern species in a southern climate, than a
southern species in a northern one. If in a Central European deposit
occur a mixture of northern and southern forms of animals, the presence
of the latter is more remarkable than that of the former. Logically, we
should look upon the occurrence of southern species in the north,
therefore, as supporting the view that a mild climate had induced them
to travel northward. The only indication, indeed, of the presence of a
Monkey in the British Isles in former times comes to us from the very
same strata which have also yielded the remains of the Siberian mammals.

Before I conclude the consideration of the pleistocene fauna, it may be
of interest to hear what Mr. Lydekker, one of our highest authorities on
fossil mammals, has to say on this subject. "The most remarkable feature
connected with this fauna is the apparently contradictory evidence which
it affords as to the nature of the climate then prevalent. The Glutton,
Reindeer, Arctic Fox, and Musk-Ox are strongly indicative of a more or
less arctic climate; many of the Voles (_Microtus_), Picas (_Lagomys_),
and Susliks (_Spermophilus_), together with the Saiga Antelope, appear
to point equally strongly to the prevalence of a Steppe-like condition;
while the Hippopotamus and Spotted Hyæna seem as much in favour of a
sub-tropical state of things. Many attempts have been made to reconcile
these apparently contradictory circumstances; one of the older views
being that while the tropical types of animals lived during a warm
interlude, they migrated southwards with the incoming of colder
conditions to the arctic type of fauna. Since, however, it has now been
ascertained that the remains of both tropical and arctic forms have been
found lying side by side in the same bed, it is perfectly certain that
such an explanation will not meet the exigencies of the case" (p. 300).

In Germany the remains of the Siberian mammals occur to a large extent
in a pleistocene deposit known as "loess," and the theory has of late
years gained ground that the latter is the fine dust-like sand
accumulated during an intensely arctic dry climate. That many of the
mammals discovered in the "loess" now inhabit the dry steppes of Eastern
Europe and North-Western Asia seems to lend support to this supposition;
but besides the mammals there are also land and freshwater shells in
this deposit. The molluscan fauna certainly indicates no
steppe-character, according to Dr. Kobelt (_b_, i. p. 166).

The attempt to utilise the Siberian migrants to Europe as indicators of
a severe climate there, certainly fails to establish conviction. But it
may be asked, surely the remains of the Alpine and Arctic plants which
have been found in pleistocene deposits must decide this question in
favour of one or the other hypothesis? Let us test it.

Plants being more directly affected than animals by changes of
temperature and rainfall, remarks Mr. Clement Reid (p. 185), give
evidence of the highest value when we inquire into former climatic
conditions. The severity of the climate during the Glacial period is
often assumed from the occurrence in pleistocene strata of such plants
as _Dryas octopetala_, some species of willow, the dwarf birch, and
others, which are now found in high latitudes and in the Alps, but are,
as a rule, absent from the plain of Northern Europe. Professor J. Geikie
goes so far as to state (p. 398) that it was unlikely that southern
England during the climax of the glacial cold had much if any vegetation
to boast of, and continues, "It is certain, however, that it was clothed
and peopled by an Arctic flora and fauna when the climatic conditions
were somewhat less severe, relics of that flora having been detected at
Bovey Tracey." He believes, therefore, that an Arctic flora took
possession of England as soon as the climate enabled it to live in the
country. Arctic plants, according to this explanation of the sequence of
events, were the first immigrants to reconquer the dreary, plantless
wastes and make them habitable for mammals.

Fortunately these views do not at all agree with those of many of our
leading European botanists and others entitled to have a voice in the
matter. Professor Warming is of opinion that the main mass of the
present flora of Greenland survived the Glacial period in that country
(p. 403); whilst Professor Drude has shown (p. 288) that all plant life
could not possibly have been destroyed in northern countries. He
maintains that the greater part of the Arctic floral elements which
unite Greenland and Scandinavia must have survived the Glacial period in
these countries in sheltered localities. Indeed, he justly remarks,
where at the present moment do we find such plantless wastes? Greenland,
Franz-Josef Land, and Grinnell Land, situated in high Arctic latitudes,
all have a flora composed of flowering plants and cryptograms. "I cannot
understand," he continues (p. 286), "why a flora, possibly mixed with
northern forms but in the main points agreeing with our present floral
elements, should not have persisted throughout the Ice Age even in the
heart of Germany." "To my mind," says Col. Feilden, the well-known
Arctic traveller (_b_, p. 51), "it seems indisputable that several
plants now confined to the polar area must have originated there, and
have outlived the period of greatest ice-development in that region."
The theory in favour of a survival of the pre-glacial flora has been
especially strengthened by the late Mr. Ball (than whom probably no
botanist possessed a better knowledge of Alpine plants), who was
strongly in favour of this view as far as the Alps are concerned. "Is it
credible," he says (p. 576), "that in the short interval since the close
of the Glacial period hundreds of very distinct species and several
genera have been developed on the Alps, and, what is no less hard to
conceive, that several of these non-Arctic species and genera should
still more recently have been distributed at wide intervals throughout a
discontinuous mountain chain some 1,500 miles in length, from the
Pyrenees to the Eastern Carpathians?" Mr. Ball's remarks, indeed, just
touch upon a very important characteristic of all the so-called _Alpine
plants_. In Europe they chiefly occur in Scandinavia and the central and
southern mountain ranges, whilst they are mostly absent from the
intervening lowlands. Again, we find a large number of species in the
mountains of Central Asia and in some of the North American mountains.
Almost all species of Alpine plants, in fact, are examples of
discontinuous distribution; and this, as every naturalist knows, is
always, in both animals and plants, a proof of antiquity.

The glacial or Alpine flora is very old, and must have originated long
before the Ice Age. But it might be urged, why should these plants be
now almost confined to the Arctic regions and the higher mountain
ranges, where the temperature undoubtedly is very low, if they had
originated during a pre-glacial period probably much milder than the
present? The answer can be given by those who have made Alpine plants
their special study, and who have attempted to grow them by
administering to them a temperature and such climatic conditions as to
be most conducive to good health. We should all expect these plants to
be very robust, and especially to be able to stand extremely low
temperatures. But, strange to say, the very opposite is the case.
Professor Blytt tells us (p. 19) that "Arctic and Alpine species in the
Christiania Botanic Gardens endure the strongest summer heat without
injury, while they are often destroyed when not sufficiently covered
during winter." The English climate then, one would think, ought to suit
these plants, since the winters are not too cold; but we find that at
Kew Gardens the large collection of Alpine plants have to be wintered in
frames under glass in order to keep them in good health; and Professor
Dyer, the Director of the Gardens, thinks they are mostly intolerant of
very low temperatures (compare also pp. 161-164).

Such being the constitution of Alpine plants, how could they possibly
have originated during the Glacial period and wandered from the
mountains into the plains, across numbers of formidable barriers, often
exposed to icy winds, for thousands of miles? As a matter of fact,
Alpine plants have survived in the high North and in the Alps because
they are there permanently protected during winter by a covering of snow
from very low temperatures, and they are at the same time prevented from
drying up. If they are given sufficient moisture and a constant, mild
temperature they seem to do very well. Such conditions are afforded them
in many parts of the British Islands, and we find indeed the Mountain
Avens (_Dryas octopetala_), one of the most typically Arctic plants,
growing wild in profusion on the coast of Galway, in Ireland, at
sea-level. The winter temperature of that part of Ireland resembles
that of southern Europe, being no less than 12° Fahr. above freezing
point. This fact appears to strengthen the view not only that the Alpine
flora is of pre-glacial origin, but that the climate of Europe during
the Glacial period was mild.

Having now shortly reviewed the state of our knowledge with regard to
the former presence in our temperate latitudes of Arctic animals and
plants, it still remains for me to give a succinct statement of the
light thrown by this fauna and flora on the widespread phenomena of
glaciation. It is necessary to do so, because, though the greater
development of glaciers on the mountains of Europe in former times does
not presuppose the prevalence of an Arctic climate, the survival through
the Ice Age of a fauna and flora could not possibly have taken place in
northern Europe if the theories of glaciation now so much in vogue are
really true. Professor Geikie reminds us, in speaking of his native
country (p. 67), that "we must believe that all the hills and valleys
were once swathed in snow and ice; that the whole of Scotland was at
some distant date buried underneath one immense _mer de glace_, through
which peered only the higher mountain tops." That under such conditions
no fauna or flora to speak of could have survived in Scotland is
evident. Then again he argues (p. 426) that because in the great plain
of Europe we meet occasionally with striated rock-surfaces and _roches
moutonnées_ very similar to those produced by the glaciers of
Switzerland, it must have been traversed by "inland ice" flowing from
Scandinavia and the Baltic southward. The boulder clay of Germany is
supposed to have accumulated underneath this vast "_mer de glace_," as
he calls it. There is no question here of a simple local development of
glaciers, such as could have existed under a mild and moist climate;
practically all the plants and animals would have been annihilated in
northern Europe under such conditions, as there were no areas free from
ice. A more vivid idea of the state of Europe during the epoch of
maximum glaciation will be obtained by looking at Professor Geikie's map
(p. 437). The whole of Scandinavia, Iceland, Scotland, Ireland, and
Switzerland is there represented as having been completely enveloped in
ice, and also the greater part of Russia, Germany, and England. In
speaking of Scandinavia (p. 424) he remarks that "the whole country has
been moulded and rubbed and polished by one immense sheet of ice, which
in its deeper portions could hardly have been less than 5000 feet or
even 6000 feet thick." The greater portion of the area indicated as
having been underneath a sheet of ice is thickly covered with
superficial accumulations of gravel, sand, and clay. The latter is
generally spoken of as "boulder clay," and, with the associated sand and
gravel, it may be observed equally well in Russia or Germany, in England
or Ireland. As a rule these stony clays thicken out as they are traced
from the high-lying tracts to the low grounds; and especially near the
mountains the rock-surfaces are often polished and striated. "For many
years it was believed," continues Professor Geikie (p. 432), "that all
those superficial deposits were of iceberg origin. The low grounds of
Northern Europe were supposed to have been submerged at a time when
numerous icebergs, detached from glaciers in Scandinavia and Finland,
sailed across the drowned countries, dropping rock-rubbish on the way.
Such was thought to have been the origin of the erratics, stony clay,
and other superficial accumulations, and hence they came to be known as
the 'great northern drift formation.'" "But," he adds (p. 433), "when
the phenomena came to be studied in greater detail and over a wider
area, this explanation did not prove satisfactory. The facts described
in the preceding paragraphs--the occurrence of striated surfaces and
_roches moutonnées_, the disturbed appearances associated with the till,
and the not infrequent presence of giants' kettles--convinced geologists
that all the vast regions over which boulder-clay is distributed were
formerly occupied by the 'inland ice' of Scandinavia."

I think Professor Geikie over-estimates the value of the evidences which
appear to be in favour of his theory. His treatise on the Ice Age leaves
one under the impression that the older view of the marine origin of the
boulder-clay is not only done with for good and all, but that no
geologists nowadays believe in it. If a more careful study of the
glacial phenomena has led most geologists to abandon what I might call
the "marine view" in favour of the terrestrial one, a more careful study
of the fauna and flora will, I venture to think, have the opposite
effect. However, it appears that even from a purely geological point of
view more can be said in favour of the old theory than Professor Geikie
and his school are ready to admit. Thus we are told by Professor Bonney
(p. 280), in referring to the boulder-clay, that "the singular mixture
and apparent crossing of the paths of boulders are less difficult to
explain on the hypothesis of distribution by floating ice than on that
of transport by land-ice, because, in the former case, though the drift
of winds and currents would be generally in one direction, both might be
varied at particular seasons. So far as concerns the distribution and
thickness of the glacial deposits, there is not much to choose between
either hypothesis; but on that of land-ice it is extremely difficult to
explain the intercalation of perfectly stratified sands and gravel and
of boulder-clay, as well as the not infrequent signs of bedding in the
latter." "Anything," writes Professor Cole (p. 239), "that keeps open
the position maintained by Lyell and others, that extensive glaciation
is compatible with mild and sheltered nooks and corners, and that much
of the distribution of boulder-clay was performed in seas and not on
land, may be welcomed by rationalists, at any rate until further
research has been carried on among the Arctic glaciers. At present every
year brings evidence of modern marine boulder-clays in high latitudes,
and removes us farther and farther from belief in a _moraine profonde_."
That foraminifera are occasionally found in boulder-clay has been known
for a long time, but it is only within recent years that these marine
organisms have been shown to occur in so many localities, that Mr.
Wright, who examined a large number of samples, says (p. 269), "I am
forced to the conclusion that the Scottish as well as the Irish
boulder-clay is a true marine sedimentary deposit."

In the fourth and fifth chapters I shall return to this subject again,
and mention a number of facts of distribution which appear to me much
easier of explanation by means of the marine than by the land-ice
theory. But I do not propose to go into further geological details in
this volume, as I think I have clearly conveyed my position in this
controversy.

Before concluding this short review of the glacial problem, so far as it
affects the origin of the European fauna, I should like to refer to the
opinion of one who has devoted years to the study of the glacial
phenomena in the Arctic Regions, viz., Col. Feilden. "To a certain
extent," he says (_a_, p. 57), "all boulder clays at home are
fragmentary when compared with the boulder-bearing beds of Kolguev,
which we may safely assume are 50 miles in length by 40 in width, with a
thickness of not less than 250 feet, probably far more, all lying in one
undisturbed mass. It is suggestive that all the glacial deposits which I
have met with in Arctic and Polar lands, with the exception of the
terminal moraines now forming above sea-level in areas so widely
separated as Smith's Sound, Grinnell Land, North Greenland, Spitsbergen,
Novaya Zemlya, and Arctic Norway, should be glacio-marine beds.
Throughout this broad expanse of the Arctic Regions I have come across
no beds that could be satisfactorily assigned to the direct action of
land-ice; that is to say, beds formed _in situ_ by the grinding force
and pressure of an ice-sheet. On the contrary, so far as I can judge,
the glacial beds which I have traced over the extensive area mentioned
above have all been deposited subaqueously and re-elevated."

One of the strongest arguments that can be used against the view of the
marine origin of the glacial phenomena in Northern Europe seems to me
the fact that we find polished rock-surfaces far removed from the source
of glaciers, and so exactly resembling those produced at the present day
by our Alpine glaciers as to appear identical to the experienced eye.
Most of such striated and polished rocks occurring in the higher
mountain ranges of Scandinavia, and also of the British Islands, have no
doubt been actually produced by glaciers, whilst those in the plain,
sometimes hundreds of miles away from the mountains, must have
originated in a similar manner; that is to say, by a heavy mass of
material containing stones being slowly dragged over the rock-surfaces.
The weight which causes the stones to polish the latter is generally
ice, but it is quite conceivable that any other substance, especially if
it is in a semi-solid state, must act and operate in much the same way.
All polished rock-surfaces are carved by glaciers, because we can see
them done by glaciers every day, is the argument commonly used nowadays.
It was not so formerly. But Mr. Mallet and his views are almost
forgotten now; his name does not even appear in our great modern works
on the Ice Age. His argument was that as the land rose out of the
glacial sea, the mud which had accumulated round the shore slipped
downward in a direction determined by the contour of the surrounding
valleys and mountains. The moment the land rose above water-level, the
large mass of gravel and mud lying upon it slipped downward. During a
steady rising of the land there would therefore be produced a continuous
sliding down of this mud-glacier, which would groove and polish the rock
underneath it, in the same manner as the ice-glaciers do in the Alps (p.
47). Professors Sedgwick and Haughton became strong adherents of Mr.
Mallet's theory at the time, but it seems later on to have fallen into
disfavour with geologists, who may not even be thankful to have it
brought to light again.


SUMMARY OF CHAPTER II.

I have endeavoured to show in this chapter how we can determine
approximately the original home of an animal. By this means we are able
to study the component elements of the European fauna, which is found to
consist to a large extent of migrants from the neighbouring continents.
There is a Siberian, an Oriental, and an Arctic element in it. The
remainder of the fauna is derived from local centres of dispersal. What
was formerly believed to have been one great northern migration now
resolves itself, on closer study, into two very distinct ones--the
Siberian and the Arctic. The mammals have received most attention
hitherto, because their remains are so frequently met with, thus
enabling us more easily to investigate their past history; but
butterflies and snails have not been neglected, and at least one very
remarkable work on the latter has been published dealing with their
origin in Europe and in the remainder of the Palæarctic region.

The former distribution of land and water is intimately connected with
the origin of the European fauna, and the changes which have taken place
in this respect may be best traced by the present distribution of
mammals, snails, and earthworms. In this manner the British Islands may
be shown to have been connected with one another and with the Continent;
Spain with Morocco across the Straits of Gibraltar; Greece with Asia
Minor, and so forth.

The British fauna has played such an important part in the evolution of
the European fauna, that it forms the key to the solution of the wider
problem. In it five elements are recognisable, of which the Lusitanian
element is the oldest, and the Siberian the most recent. It has been
deemed advisable to conclude this chapter with a short review of the
history of the Glacial period in its climatic effects on the animals and
plants of Europe. A number of writers are quoted who have conducted
special researches in determining the temperature of our continent at
the time. The fauna of Europe is frequently described as having been of
an Arctic nature, but as a matter of fact there existed during the Ice
Age a striking and most remarkable mingling of a northern and a southern
fauna. The presence of Siberian mammals in Europe is said to have been
due to the prevalence of a dry steppe climate, but this view is not
supported by other evidence. The Alpine flora in a wide sense is
probably pre-glacial in origin, and appears to have survived the Ice Age
where it is now known to exist. A few words on the phenomena of
glaciation are added before bringing the chapter to a close.




CHAPTER III.

THE FAUNA OF BRITAIN.


The British Islands are, as I have remarked, very suitable as a
starting-point for our investigations. Their fauna and flora are fairly
well known, and the distribution of the large animals at any rate, which
are of course of much importance in these researches, has been as much
studied as that of any other area in Europe. We possess in England an
abundance of the remains of past animal life, and a combination of the
data furnished by both of these important factors will enable us to draw
up a history of the origin of the present British fauna.

In the first chapter I indicated that in the fauna of the British
Islands three divisions or elements are recognisable--a northern, a
southern, and an eastern. These elements correspond to migrations which
can be proved to have arrived in this country at different periods in
past times. When we investigate these migrations more closely, the
eastern is found to be composed partly of European and partly of
Siberian species. The southern is made up of European and of Central and
Southern Asiatic species. To make matters still more complex, the
southern and eastern migrations insensibly merge into one another, so
that it is often very difficult to determine to which of them an animal
may belong. The European species spread principally from three centres
over Europe--viz., from the Lusitanian, Alpine, and the Balkan centres.
The southern element of the British fauna is therefore composed of
animals which have originated in these three centres, and in Central and
Southern Asia. The Balkan species have been included with those coming
from the latter centre under the term "Oriental" migration. The sixth
chapter is devoted to it, whilst the Lusitanian and Alpine migrations
have each a chapter to themselves.

The Arctic Hare is, as I have already mentioned, one of the mammals of
the northern element of the British fauna. It is now confined to the
mountains of Scotland and the plain and mountains of Ireland. But in
former times it had a wider range in the British Islands. The Stoat is
another distinctly northern mammal. It occurs with us, as Messrs. Thomas
and Barrett-Hamilton have pointed out, in two distinct varieties or
species, the one being confined to Great Britain, the other to Ireland.
As I shall explain more fully later on (p. 135), I have reasons to
believe that the Irish Stoat came from the Arctic Regions as a northern
migrant, but that the English Stoat, on the other hand, reached England
with the Siberian fauna from the east. A third northern animal, now
extinct in the British Islands, is the Reindeer. It is supposed to have
died out in these countries not very many centuries ago, and records
have been handed down to us that it still inhabited Scotland as late as
the thirteenth century. Like the Stoat, it occurred in two well-known
varieties, distinguished from one another by the shape and form of the
antlers. In the English pleistocene deposits the remains of both kinds
are met with mingled together, whilst in Ireland only one of them has
been found. The explanation of this case is similar to that of the two
stoats. One of the varieties, which we may call the northern one, came
to us from the Arctic Regions; the second wandered to the British
Islands at a later period, when Ireland had probably become separated
from England. It was therefore unable to penetrate so far west.

One of the most familiar examples of a northern British bird is the Red
Grouse (_Lagopus scoticus_). By most authorities it is looked upon as a
species distinct from the Scandinavian Willow Grouse (_Lagopus albus_),
but except in colour it is indistinguishable from it, and the eggs are
identical. The whole genus _Lagopus_ is a distinctly Arctic one, and
there can be no doubt that the British Grouse belongs to the northern
migration, just like the Arctic Hare. The Ptarmigan (_Lagopus mutus_)
and the Snow Bunting are also migrants from the north. Though as
resident British birds they are quite confined to Scotland, the remains
of the former have been found in a cave in the south of Ireland, showing
that its range in the British Islands was formerly more extensive.
Another bird which probably came to our shores with this same migration,
though it is now unfortunately extinct, is the Great Auk (_Alca
impennis_), of which some specimens have luckily been preserved in our
museums. From the occurrence of its remains in kitchen-middens and other
recent deposits, the Great Auk is known to have inhabited the coasts of
Scotland, Ireland, and Scandinavia, as well as those of Newfoundland.
Mr. Ussher recently found the bones of this bird near Waterford, which,
I believe, is the most southern locality known. The manner of their
occurrence leaves no doubt that the bird had been used as food by the
early races of man. In all probability it originated in the Arctic
Regions, and subsequently spread south on either side of the Atlantic.
We need not here refer to the many winter visitants,--northern birds
which appear regularly, or at more or less long intervals, in these
islands,--although in most of the ornithological works they are included
under the term "British Birds."

All the British reptiles and amphibia appear to have reached us from the
south or east, but among the fishes there are a good many northern
forms. The whole salmon family--the _Salmonidæ_--are typical northern
immigrants. The Stickleback (_Gasterosteus aculeatus_), too, has
undoubtedly come to us from the north. The genus _Cottus_, like
_Gasterosteus_, is certainly Arctic in origin. Originally freshwater
forms, many species are now found between tide-marks, and of these a
few have migrated southward along the coasts of the great continents.
Thus we meet with various species of _Cottus_ as far south as California
and Japan, on the American and Asiatic coasts of the Pacific
respectively. In Europe, two species, viz., _C. scorpio_ and _C.
bubalis_, range as far south as the French coast. Our freshwater
_Cottus_, the Miller's thumb (_Cottus gobio_), has migrated to us from
the north with the Arctic species. All the freshwater forms, indeed, of
this genus are typically Arctic.

A large number of land and freshwater invertebrates too have no doubt
reached us from the north. Some of them may have originated in
Scandinavia or within the Arctic Circle, but others probably came still
farther, either from America or even from Asia, and used the Arctic
land-connection _viâ_ Greenland in their migration to Europe. As I shall
give a number of additional instances of such migrants in the succeeding
chapters, I need not, perhaps, dwell upon them now any longer, except to
mention a few of the more typical ones. _Vertigo alpestris_, a minute
snail with an amber-coloured shell, and our freshwater pearl-mussel,
_Unio (Margaritana) margaritifer_, belong to this migration. Then among
butterflies we may cite the Marsh-ringlet (_Coenonympha typhon_), and
among beetles, _Pelophila borealis_ and _Blethisa multipunctata_. There
are a number of northern spiders, among which a few certainly indicate
an Arctic origin, or at any rate, that they have wandered to Europe
across Greenland and the old Arctic land-connections. _Bathyphantes
nigrinus_, _Linyphia insignis_, and _Drapetisca socialis_, for instance,
are three British species whose range indicates a northern origin, and
which also occur, according to Mr. Carpenter, in North America. Mr.
Carpenter also tells me that the Collembolan, _Isotoma littoralis_, is a
typical northern migrant. He has recently discovered it in the west of
Ireland, its only station in the British Islands.

Among the crustacea, the genus _Apus_ forms an exceedingly interesting
illustration of the northern migration, _Apus glacialis_ having been
discovered in a Scottish pleistocene freshwater deposit, whilst it is
now almost confined to the Arctic regions.

To the same group of animals also belong the three remarkable species of
freshwater sponges, _Ephydatia crateriformis_, _Heteromeyenia Ryderi_,
and _Tubella pensylvanica_, which Dr. Hanitsch has described from some
lakes in Western Ireland. None of these are known from Great Britain or
from the continent of Europe. A few North American plants grow wild in
the same district. That any of these should owe their existence in
Ireland to accidental introduction appears to me exceedingly improbable.
In a former contribution to this subject (_a_, p. 475) I assumed that
these American plants and animals had migrated to Europe at the same
time as the other northern forms referred to. My friend Mr. Carpenter,
however, takes exception to this (p. 383), and I quite recognise the
force of his argument. "Their very restricted and discontinuous
ranges," he says, "along the extreme western margin of Europe mark them
as decidedly older than those northern animals and plants which have a
circumpolar distribution." We have indeed quite similar examples in the
Oriental migration, of which part is very ancient, surviving here and
there and exhibiting discontinuous distribution. We may therefore look
upon these American immigrants as among the oldest members of that
northern stock which have survived in our islands--probably a mere
remnant of a once luxuriant flora and fauna.

In order to show the importance of the Eastern or Siberian element in
the English, or, we might say with Dr. Sclater, the Anglo-Scotian
mammalian fauna, I herewith give a list of the species of mammals which
probably migrated to Great Britain from Siberia. I have marked with an
asterisk those which still exist in this country (not in Ireland), or
have become extinct within historic times.

    Canis lagopus.
    Gulo luscus.
  * Mustela erminea.
  *   "     putorius.
  *   "     vulgaris.
  * Sorex vulgaris.
    Lagomys pusillus.
  * Castor fiber.
    Spermophilus Eversmanni.
       "         erythrogenoides.
  * Mus minutus.
  * Arvicola agrestis.
  *   "      amphibius.
      "      arvalis.
  *   "      glareolus.
      "      gregalis.
      "      ratticeps.
    Equus caballus.
    Saiga tartarica.
    Ovibos moschatus.
    Cricetus songarus.
    Myodes lemmus.
    Cuniculus torquatus.
    Alces latifrons.
      "   machlis.
    Rangifer tarandus.

We have evidence that most of these twenty-six species of mammals came
from Eastern Europe, but there is no reason to suppose that they
originated there. On the contrary, it is highly probable, as I said
before, that their native home is Siberia, and that they entered Europe
to the north of the Caspian. Along with these, vast numbers of other
forms of life, and also plants, swarmed into our continent, and as we
advance eastward from England we meet with them in increasing numbers to
the present day. But not only on the Continent do we find these
survivals of the great Siberian migration, which has been so ably
described by Professor Nehring; no less than nine species still inhabit
Great Britain (if we include the recently extinct Beaver). On the other
hand, not more than three have been found fossil in Ireland, and of
these only one still survives. This very significant fact will be
referred to again more fully on p. 153. Meanwhile it should be
remembered that these three species, viz., _Mustela erminea_, _Equus
caballus_, and _Rangifer tarandus_, occur in Ireland in varieties
distinct from those found in Central Europe. It is upon this, and many
other circumstances, that I founded my belief that Ireland was already
separated from England at the time of the arrival of the Siberian
emigrants in the latter country. As we shall see, the Irish Stoat,
Horse, and Reindeer probably came by a different route from that taken
by the English representatives of the same species.

Very few of the lower animals of Siberian origin have reached the
British Islands. Most of those which were formerly thought to be
Siberian are either of East European or of Central and South Asiatic
origin, though they probably joined the Siberian migration on their way
to England. The Arctic migration brought a greater variety of species to
this country than the Siberian, but neither the one nor the other has
contributed more than a small percentage to the British fauna. The bulk
of that fauna is derived from the various European centres of dispersal,
and especially from Central and Southern Asia.

Those animals which have their home in the latter area, I have named
Orientals, though it must be remembered that they need not necessarily
have come from what is known among zoologists as the "Oriental Region."
The terms "Oriental animals" and "Oriental migration" are used here in a
wider sense, and include even those species which reached Central and
Northern Europe from South-Eastern Europe. It is astonishing, what a
vast number of both vertebrate and invertebrate animals can be traced
back to this Oriental migration. Great tracts of Europe were repeatedly
submerged beneath the sea during Tertiary times, and on their
re-appearance were formed into green fields and pastures new for the
rich Asiatic fauna, which was ever ready to flood the neighbouring
continent. This went on, and not for a comparatively short space of
time, as in the case of the Siberian invasion; the immeasurable ages
which passed, whilst several of the Tertiary epochs dawned upon Europe,
witnessed an almost constant stream of Asiatic immigrants pouring in
upon us. Europe returned her own products in exchange, but they must
have been scanty in comparison to the enormous number of species which
have undoubtedly originated in Central and Southern Asia. Very many of
the widely distributed forms in the British Islands are of Oriental
origin. Among these are also the cosmopolitan species, such as the Barn
Owl (_Strix flammea_) and the Painted Lady Butterfly (_Vanessa cardui_).
A great number of our British Mammals, Birds, Butterflies, and Beetles
have come to us with the Oriental migration. But, as I shall explain in
the special chapter devoted to it, the earlier migrants from the
south-east found their northward progress barred by a great sea which
stretched through Central Europe from west to east. The Mediterranean
was then divided into two smaller basins. On their arrival in Greece,
which was then connected with Asia Minor and Southern Italy, the
Oriental migrants seem to have turned westward, skirting the shores of
the Mediterranean. When they finally reached Spain, many then changed
their course northward (see Fig. 5, p. 117) and wandered to the British
Islands with the Lusitanian animals which came from South-Western
Europe.

Dr. Wallace makes mention of a fairly large number of species and
varieties of Lepidoptera, Coleoptera, and land and freshwater Mollusca,
supposed to be _peculiar to the British Islands_. Even if these were all
found to be of British origin, most of their nearest relatives are
continental species. Many, however, must be looked upon as mere races or
sub-species of familiar continental forms. But others, such as
_Geomalacus maculosus_ and _Asiminea Grayana_, are by no means confined
to the British Islands. Some of the so-called varieties enumerated by
Dr. Wallace are merely slight individual variations in form and colour,
which, only by the extraordinary tendency of the variety-monger to
advertise himself, have received a distinct Latin denomination. The
number of the remaining species, after weeding out the unworthy ones,
will be found to be insignificant.

Similarly, the list of seventy-five species and varieties of flowering
plants included by Dr. Wallace among the forms peculiar to the British
Islands (p. 360) is reduced by Sir Joseph Hooker to twenty. The
remainder are to be considered as varietal forms of a very trifling
departure from the type, or as hybrids.

Just as we distinguish in the British Islands the parts inhabited by
Englishmen, Scotchmen, and Irishmen, so we can recognise three divisions
in the animal world, and these roughly correspond to the boundaries of
England, Scotland, and Ireland. Most of the eastern species inhabit
England, most of the northern ones are confined to Scotland, whilst
Ireland is occupied chiefly by southern animals. This, however, is only
a very rough-and-ready method of sub-dividing the British Islands into
their component parts according to the origin of their faunas. On closer
study such a division is found to be unsatisfactory. The eastern species
do not really stop at the Scottish frontier, they range far into
Scotland. Nor are the northern forms confined to the latter country.
Many of them range into Ireland, and also into England. I have
constructed a map of the British Islands showing approximately the
boundaries of the northern, eastern, and southern species (p. 7), but
even this may not altogether meet with the views of an ornithologist or
conchologist. For every group of animals the boundaries would probably
require to be marked differently. There is also a good deal of
overlapping, so that the attempt to define the limits of the various
elements meets with great difficulties. But the map represents, I think,
fairly well the general impression one receives as to the disposition of
its component elements, after a careful study of the British fauna as a
whole.

The distribution of the British plants has been worked out much more
thoroughly than that of the animals. It need not surprise us, therefore,
that the first attempt to separate the British Islands into natural
divisions was made by a botanist--the late Mr. Watson. As he himself
pointed out, in making these divisions he did not take into
consideration the origin of the British species. They represent merely
groups of assemblages of plants of different types of vegetation. Edward
Forbes, on the other hand, founded his districts on the origin of
plants. His work is not only the first of the kind, but it is a
classical essay, and remains one of the most remarkable contributions to
the literature on the geographical distribution of living organisms
known to science. The vegetation of the British Islands, he informs us
(p. 4), presents a union of five well-marked floras, four of which are
restricted to definite provinces, whilst the fifth, besides exclusively
claiming a great part of the area, overspreads and commingles with all
the others. These are--

  I. Mountainous districts of South-west }
       and West of Ireland.              }  Lusitanian type.

  II. South-west of England, and         }
        South-east of Ireland.           }  Gallican type.

  III. South-east of England.

  IV. Mountains of Scotland, Cumberland, }
        and Wales.                       }  Scandinavian type.

  V. General Flora.                         Germanic type.

Professor Forbes points out, in connection with the plants of the
Germanic type, that the fauna accompanying this flora presents the same
peculiarities and diminishes westward and to the north. This type
includes, therefore, almost all the species which can be shown to have
come to us directly from the east, few if any of which have penetrated
to Ireland.

On a previous occasion, the same author had divided the British Islands
into ten districts, according to the distribution of their molluscan
fauna. These are--

     I. The Channel Isles.
    II. South-east of England (including Cambridgeshire).
   III. South-west of England.
    IV. North-east of England.
     V. North-west of England (including Isle of Man).
    VI. North of Ireland.
   VII. South of Ireland.
  VIII. South of Scotland.
    IX. North of Scotland.
     X. Shetland Isles.

In a short paper on this subject (_b_, p. 5), I have shown that some of
these districts are founded on erroneous data, whilst, with the
knowledge now at our disposal, others can no longer be maintained as
distinct. I thought then that the molluscan fauna warranted a division
of the British Islands into the following two provinces:--

   I. England and Wales (except the South-west).
  II. South-west of England and Wales and the whole of Ireland and
      Scotland.

The second district contains some species of molluscs which are almost
entirely absent from the first, such as _Geomalacus maculosus_,
_Testacella Maugei_, _Helix pisana_, _Helix revelata_, _Helix acuta_,
and _Pupa ringens_. These are all of Lusitanian origin, and do not occur
in Central Europe. Scotland alone cannot be classed as a separate
province, since it does not contain a single species peculiar to itself.
But, along with Ireland and the South-west of England and Wales, it is
distinguished from the remainder of these countries by the almost total
absence of what have been called Germanic types.

A French conchologist, the late Dr. Fischer, dealt with the British
molluscan fauna in a somewhat similar spirit (p. 57). He divided the
British area into two districts, but these differ from mine in so far as
the South-west of England and Wales and the West of Ireland form one;
the remainder of England and Ireland as well as the whole of Scotland
the other. His classification is of particular interest, since the first
district represents part of a larger Atlantic province, the second a
portion of the Germanic province of the European sub-region. The latter
he looks upon as one of the sub-regions of the great Palæarctic Region.
Attention is thus drawn to the intimate relationship existing between
the western parts of the British Islands and the Spanish peninsula on
the one hand, and between the eastern portions and Central Europe on the
other.

Mr. Jordan's North-Sea-and-Baltic district includes Scotland and the
North of Ireland, whilst England joined with the West and South of
Ireland forms part of his Celtic province. Both of these districts or
provinces belong to Mr. Jordan's greater Germanic Region (p. 302).

In the collection illustrating the geographical distribution of animals
in the Dublin Museum, the British species have been grouped into three
divisions. One contains those with a wide range over the British
Islands, another the characteristic forms of the south-east and lowland
districts of Great Britain, and the third the Irish and the western and
highland Anglo-Scotian species. Mr. Carpenter has named the last two
divisions the "_Teutonic_" and the "_Celtic_." More recently, he has
recognised that this last division contains two distinct groups; one
including animals of northern, the other those of southern origin. He
acknowledges indeed, just as I do, three distinct faunas in the British
Islands, with the addition of the group of generally distributed species
of undetermined origin.

Many other naturalists have worked in the direction I have
indicated--namely, in grouping the British animals into several distinct
assemblages, without, however, taking their foreign range into
consideration, or their origin. I have already referred to the useful
work done by botanists, who have been the pioneers in the science of the
geographical distribution of living organisms. Among the British
naturalists who have applied the principles of Watson to zoology, A. G.
More deserves to be specially mentioned. He was the first to make a
serious study of the British fauna on the lines laid down by that
distinguished botanist. In conjunction with E. Boyd, he published a
valuable essay on the "Distribution of Butterflies in Great Britain,"
and later on the birds were similarly dealt with. All the more
important groups of animals are now being studied with a view to
determining their exact range in these islands. Mr. Harvie-Brown, Mr. J.
W. Taylor, Mr. Eagle Clarke, Mr. Miller Christy, Mr. Ussher, Mr.
Barrington, and a number of others have considerably advanced our
knowledge in this direction in recent years.

Any such contributions are to be welcomed as furnishing us with the
necessary data to solve the problem of the origin of the British fauna.
Meanwhile we know enough to enable us to assert positively that the
latter has reached us by land-connections from various parts of Europe
(cf. p. 35). This statement of course refers to the bulk of the British
fauna. The small proportion of indigenous species, or such as have been
introduced accidentally, may be left out of consideration when dealing
with the great mass of animals which have evidently migrated to the
British Islands on land now sunk beneath the sea (see Fig. 4, p. 60).
Opinions of zoologists, botanists, and geologists are practically
unanimous on this subject; yet there are two other theories, which have
from time to time been advanced to account for the origin of the British
fauna. Only the first of these, however, can claim the serious attention
of those interested in the problem. Its chief contention lies in the
oft-asserted dictum of the "_imperfection of geological record_." It has
been suggested, in fact, that the British fauna, instead of having
migrated to our islands, might have originated there, but that, owing
to the fragmentary nature of our Tertiary deposits, all trace of their
early history had disappeared. "The origin of European species," remarks
Professor Cole (p. 238), "within the area of the British Isles, and
their migration outwards when local conditions became less favourable
for their multiplication, are possibilities that seem too often
disregarded. Yet the geologist must see in the western borderland of
modern Europe a diminished continent from which land-animals must have
again and again moved eastward." "Hence geologists may fairly be
unwilling to look on our isles as barren lands waiting to be peopled in
pliocene or later times. Far rather has the breaking up of a broad
land-area along the present continental edge sent our land-fauna to the
new steppes that opened eastward, leaving us a mere diminished remnant
to struggle with the glacial period."

There are in Professor Cole's views many points with which I readily
agree. In the first place, he acknowledges that migration has taken
place on land, so that we have our land-connection between Great Britain
and the Continent whatever theory we accept as to the direction taken by
the migrants. That the western borderland of Europe has given rise to
many important assemblages of animals in past times, seems to me also
exceedingly probable, nor do I look upon the British Islands as "barren
lands waiting to be peopled in pliocene or later times." On the
contrary, I believe an almost uninterrupted stream of migrants poured
into the British Isles before pliocene times from the south. But what I
thoroughly disagree with, is the remark that our British land-fauna has
been sent to the new steppes that opened eastward. These are the more or
less arid portions of Eastern Europe. Professor Cole no doubt has in
mind those species of mammals which I have included in what I called the
Siberian migration, and of which we have fossil evidence in the late
Tertiary deposits of Europe. It would be impossible here to discuss this
subject fully, especially as I have done so in the subsequent chapters;
but, even if we had no geological record whatsoever, the present range
of the species in question and their nearest relatives must convince us
that they could not have originated in Western Europe. However, on the
strength of the geological evidence, Professor Nehring--the only one who
has made this fauna his special study--remarks (p. 228), that there
seems scarcely any doubt that this steppe-fauna just referred to had
come to us from the east. Professors Boyd Dawkins, Brandt, and Lartet
held similar views.

The theory that an ice-sheet stretched across a narrow sea might be the
means of aiding a fauna across from the mainland to an island, is
particularly inapplicable to the British Islands. Neither Mr. Kinahan
nor Mr. Lamplugh, the two supporters of this view, have, however, taken
the trouble to apply it to more than one species of the British fauna.
An ice-bridge, thinks Mr. Kinahan, "could easily have connected Scotland
and Ireland, thus giving a land causeway for migration" (p. 3). Mr.
Lamplugh throws more light on this interesting speculation by giving us
the name of an animal which he believes crossed a narrow sea on a bridge
of ice. This animal unfortunately happens to be one whose remains have
never been found in high northern latitudes, viz., the Irish elk
(_Cervus giganteus_). And because he is of opinion that this species of
extinct deer found its way to the Isle of Man from the mainland on a
waning ice-sheet, he sees no reason why certain elements of the Irish
fauna should not have been similarly introduced.

It seems of no advantage to begin the discussion on the origin of the
British fauna by assuming the former existence of ice-bridges, and the
possibility of a migration across them of some of its members. If a
glacier connected Scotland and Ireland, the climate of both countries
(since they were highlands and acted as the feeders of the ice-sheet)
must have been uncomfortable to the majority of the British species.
What were the inducements that could have prompted those which had
braved the discomforts of Scotland to emigrate to Ireland at such a
time? What light does it throw on the origin of the Irish fauna as a
whole, to advance the extremely improbable hypothesis that certain
elements of it may have reached Ireland by an ice-bridge? If any
species came to that country in such an unusual manner, surely they must
have been Arctic or northern forms. But what about the southern species,
which form the bulk of the Irish fauna and also the flora? Even the
Arctic element of the British fauna, which probably includes, besides
the Reindeer, many hundreds of species, could not, I think, have
migrated to these islands on an ice-bridge. Indeed, I agree with most of
the writers who have dealt with the subject, in asserting that the
northern as well as all the other elements of our fauna utilised for
their migration the old land-bridges which connected these islands with
one another and with the Continent.

There is a greater diversity of opinion as to the age during which the
British fauna arrived in these islands. This is naturally a much more
complicated problem, but it is one which I am convinced will ultimately
be solved mainly by means of a study of the geographical distribution of
animals and plants. If we can settle the relative ages of the various
migrations, we thereby supply an important link in our attempt to
reconstruct the past geographical features of the British Islands. The
range of the British species will give us an idea of the nature of the
land-connections and their gradual changes in course of time. Geological
data are exceedingly valuable in these inquiries, but it is a fatal
mistake to build our geographical theories and the origin of the British
fauna as a whole entirely on the assumptions of a certain school of
geologists. Unfortunately, Dr. White's very interesting remarks on the
British fauna for this reason lose much of the value which they might
otherwise possess.

In his remarkable essay the late Edward Forbes affirms that the flora
peculiar to the west of Ireland, of which the strawberry tree (_Arbutus
unedo_) is the most striking example, and which exhibits such strong
southern affinities, is not only much the most ancient of our island
floras, but that it is actually of miocene age. It migrated to Ireland
from Spain at a very remote period, during which he supposed that a
direct land-connection existed between the two countries. The
destruction of this old land-bridge, he thinks, must have taken place
before the commencement of the Glacial period. Climatal changes during
that time destroyed the mass of the southern flora which had thus
reached Ireland, the survivors being species such as were most hardy
(saxifrages, heaths, etc.), which he considers to be the only relics of
this most ancient portion of our flora.

The northern or Arctic fauna and flora, according to the same author,
established themselves in the British Isles during the Glacial
period--at a time when these were groups of islands in the midst of an
ice-bound sea. Finally, the great mass of our animals and plants
migrated from the Continent to England after the Glacial period. "The
migration of the species," he says, "less speedy of diffusion, which are
now peculiar to England was arrested by the breaking up of the
land-connection between England and Ireland, and thence the famous
deficiencies of the sister isle, as, for instance, its freedom from
reptiles" (p. 10). He is also of opinion, that the separation between
England and the Continent took place at a later date than that between
England and Ireland.

According to Dr. A. R. Wallace (p. 338), we possessed just before and
during the Glacial period "a fauna almost or quite identical with that
of adjacent parts of the Continent, and equally rich in species." But
the submersion, he thinks, which is supposed to have occurred during the
latter part of the Glacial period, destroyed the greater part of the
life of our country. When England again became continental, continues
Dr. Wallace, this fauna was succeeded by an assemblage of animals from
Central Europe. "But sufficient time does not seem to have elapsed for
the migration to have been completed before subsidence again occurred,
cutting off the further influx of purely terrestrial animals, and
leaving us without the number of species which our favourable climate
and varied surface entitle us to." The comparative zoological poverty of
Ireland he attributes to the fact that "the depth of the Irish Sea being
somewhat greater than that of the German Ocean, the connecting land
would there probably be of small extent and of less duration, thus
offering an additional barrier to migration."

Dr. Wallace's explanation of the origin of the British fauna is
disappointing after Forbes's careful study and critical inquiry into
its component elements. So great an authority on geographical
distribution might have given us more lucid statements of his views on a
variety of topics connected with this subject.

In speaking of the fauna of Ireland, Professor Leith Adams, Professor
Dawkins, and Mr. Alston are evidently only thinking of the mammals,
which form but a very small proportion of it. The first-mentioned
palæontologist held that there was a land-communication between Scotland
and Ireland at the close of the Glacial period, by which the greater
portion of the mammals that had found their way to the former country
crossed to the latter (p. 100). And, he continues, the severance between
the two countries must have taken place before the slow-travelling Mole,
the Beaver, the forest-haunting Elk and the Roebuck had time to arrive.

Much in the same spirit are Mr. Alston's remarks on this subject (p. 5).
"The absence from the known fossil fauna of Scotland and Ireland of most
of the characteristic post-pliocene English animals, shows that the
northward migration of these forms was slow, gradually advancing as the
glacial conditions of the northern parts of our islands decreased in
intensity. Thus it is not difficult to suppose that the Hedgehog,
Ermine, Badger, Squirrel, and Mountain Hare may have found their way
through southern Scotland into Ireland long before they were able to
penetrate into the still sub-arctic regions of the Highlands.
Subsequently, when the improvement of the climate had continued, the
Shrews and Voles may well have found their way northward along the
comparatively genial coasts, before the larger beasts of prey could find
a sufficient stock of game."

That the Bear, Wolf, Stag, Horse, Mammoth, and Reindeer lived in Ireland
before the Glacial period is considered highly probable by Professor
Boyd Dawkins (_a_, p. 152).

Only the Butterflies are dealt with in Dr. Buchanan White's clever
little essay on distribution. And, as I remarked before, his conclusions
are somewhat marred by the unwarrantable assumption that our islands at
no distant date were totally destitute of all plant-life, and were
therefore uninhabitable by animals. But his paper differs in so far from
most of the others, that he has made a thorough study of the one group
he deals with. In some respects it may serve as a model to future
students in its general treatment of the problem he has set himself to
work out. He adopts the principle, even for butterflies, that though it
is possible for them to be blown over from the Continent, they have
probably migrated with the rest of our indigenous fauna and flora across
the dry bed of the German Ocean. His conclusions are that Britain
derived its butterfly fauna from continental Europe in post-glacial
times, that the Arctic and Alpine species were the first arrivals, and
that one part of the Irish species reached Ireland by way of Scotland,
another from the south. He assumes, of course, that Great Britain and
Ireland were connected at that time.

Within the last few years the spell which has bound naturalists to
accept the theory of a total destruction of life during the Glacial
period is happily vanishing, and more enlightened views are gaining
ground. The Lusitanian species of plants in the west of Ireland, which
had already furnished Forbes with an argument in favour of survival, are
also regarded by Mr. Bulman as the remnants of a pre-glacial flora which
was exterminated everywhere else by the cold (p. 265). This view of the
survival of a pre-glacial fauna and flora has since been accepted by Mr.
Carpenter, whilst I also have endeavoured to bring fresh evidence into
the field in its favour. We both agree with Edward Forbes in considering
the Lusitanian element as the oldest section of our fauna and flora, and
that it came long before the Glacial period. But we differ somewhat from
him, in so far as we do not limit that element to Ireland. It seems also
to be represented in South-western England and Wales, though it is there
less conspicuous.

This decision as to the relative age of the British South-western fauna
has not been arrived at from any geological considerations. The
conviction that it must be older than the other sections has been gained
solely from a study of the geographical distribution of the species
belonging to that fauna. Many of them exhibit what is known as
"discontinuous distribution," which zoologists are agreed to regard as
a sign of antiquity. Thus _Geomalacus maculosus_, the Kerry Slug, is in
the British Islands confined to South-western Ireland (see Fig. 19, p.
300), and on the Continent it is unknown north of North-western Spain.
The Millipede, _Polydesmus gallicus_, has a wider range in Ireland, and
is also known from France and the Azores. Two Earthworms of the Spanish
and Mediterranean region, viz., _Allolobophora veneta_ and _Georgii_,
have been discovered in Ireland, but are apparently unknown in England
or France; whilst the Weevil, _Otiorrhynchus auropunctatus_, does not
occur north of the Auvergne Mountains in France except in Ireland. A
very large number of instances might be mentioned of species found in
South-western Europe, France, the South-west of England and Ireland.
Enough, however, has been said to show the nature of the fauna, and
there is, as Forbes has pointed out, a corresponding flora.

A great number of the species belonging to the South-western British
element seem to have originated in South-western Europe, or at any rate
to have spread over our continent from that part. Their home lay
therefore probably in a warm, damp climate, and it seems a reasonable
inference to suppose that they spread north at a time when the
temperature over the British Islands was much higher than what it is
now. Any one familiar with our Bristle fern, or Killarney fern, as it is
called in Ireland (_Trichomanes radicans_), will readily admit that it
must have come to us at such an epoch. It at once suggests some shady
waterfall in a tropical forest, and indeed the home of the genus is
South America. It is one of those plants which have evidently migrated
to us from South-western Europe, a mere remnant of a once luxuriant
flora.

Sir Archibald Geikie tells us (p. 837), and in the main every one agrees
with him, that at the beginning of the Tertiary era in which we now
live, the climate was of a tropical and subtropical character in Europe.
Gradually it became more temperate, and eventually it passed into a
phase of extreme cold, but since that time the cold has again gradually
diminished. It is quite evident, therefore, that from a purely
geological point of view our south-western flora must have migrated
northward before the cold came on, and survived in sheltered localities
under the influence of the mild coast climate. Some, however, suppose
that there occurred a phase of extreme mildness immediately after the
Glacial period, and that it was during that time that the Lusitanian
fauna and flora became established in the British Islands. To this
Professor James Geikie replies (_b_, p. 169), "there are few points we
can be more sure of than this, that since the close of the Glacial
epoch--since the deposition of the clays with Arctic shells and the
Saxicava sands--there have been no great oscillations, but only a
gradual amelioration of climate. It is quite impossible to believe that
any warm period could have intervened between the last Arctic and the
present temperate conditions without leaving some notable evidence in
the superficial deposits of Scotland, Scandinavia, and North America."
Thus it appears that on the whole the assumption that the Lusitanian
fauna and flora are very ancient and pre-glacial is also supported on
geological evidence.

[Illustration: Fig. 5.--Map of Europe, with arrows indicating
approximately the course taken by the different streams of migration
towards the British Islands.]

The course of events in the origin of the British fauna might have been
therefore somewhat as follows:--In early Tertiary times, when the
climate all over Western Europe was moist and semi-tropical, a migration
proceeded northward from the south-western corner of Europe. This was
strengthened by Oriental migrants which had moved westward along the
Mediterranean basin (Fig. 5, No. 1). Owing to geographical changes
supervening, the Alpine fauna (No. 2) was then enabled to colonise the
British Islands, and subsequently another migration had begun to come in
from the south-east (No. 3). The climate had meanwhile gradually become
more temperate and drier. About the same time, or even earlier, an
Arctic migration commenced to pass southward (No. 4), and finally the
Siberian animals (No. 5) poured into our continent. The arrows in the
map indicate the directions followed by the different migrants as they
travelled to the British Islands. The arrows are not meant to represent
the whole nor the full extent of the migrations from any particular
centre, but only in so far as they affect our islands. Moreover, it
would be impossible to indicate on one map the geographical conditions
which obtained during the several migrations. It must be remembered that
during the time which elapsed while they passed into the British
Islands, these were joined in the north to Scandinavia and in the south
to Belgium and France. The various phases of geographical evolution of
Europe will be studied in the subsequent chapters, and maps will then be
given to show as far as possible in a general way the leading
characteristics of these great changes.

I have now given some reasons for the belief that several different
migrations of animals entered the British Islands in later Tertiary
times. I have also shown why some of them must be looked upon as being
older than others, and in so far we have come to a decision as to their
relative ages. It still remains for us, however, to examine how their
geological ages can be approximately determined. We require for this
purpose palæontological aid.

In the fifth chapter will be found the history of the Siberian
migration. And since we possess most valuable records of it in the
numerous fossil remains discovered in Central and Western Europe, we are
able to trace their progress from the east to the west in a very
complete and satisfactory manner. In England their first appearance
dates from the Forest-Bed, for here we find remains of the Glutton
(_Gulo luscus_), Musk-Ox (_Ovibos moschatus_), and others (see p. 204).
It seems reasonable to suppose, therefore, that the first entry of these
Siberian mammals into Europe took place at or just before the Forest-Bed
period. But Professor Nehring tells us in his remarkable work on the
Tundra and Steppes (p. 222), that in Germany the remains of the same
mammals occur in deposits which are certainly more recent than the lower
continental boulder clay; and he is inclined to the belief that they
migrated into Europe during the inter-glacial phase which is supposed to
have separated the earlier from the later stage of the Glacial period.
It is evident that in this case the inter-glacial period in Germany
would have corresponded to, and be contemporaneous with, our Forest-Bed
period. The deposits immediately preceding the Forest-Bed would also be
contemporaneous with the lower continental boulder clay. Although this
may seem rather a startling statement to make, from the evidence which
will be brought forward in the fourth and fifth chapters I am inclined
to the belief that such is probably the case.

Having once arrived at a determination of the exact geological period
during which the Siberian mammals invaded our continent, and having also
previously determined the relative ages of the various other migrations,
we have advanced another step in the direction we are aiming at. Let us
suppose that the Siberian migration actually reached the British Islands
during the Forest-Bed period. Since the Siberian migration is the most
recent of those which entered the British Islands, the others must have
commenced their march before the Forest-Bed period. Now it was Professor
Boyd Dawkins who first indicated to us, as I have remarked before, the
method of research to be adopted in an attempt to determine the
geological age of the different migrations in so far as they affected
the British Islands. I may be excused, therefore, for again quoting the
following important passage in one of his works. "The absence," he says
(_b_, p. xxix), "of the beaver and the dormouse from Ireland must be due
to the existence of some barrier to their westward migration from the
adjacent mainland, and the fact that the Alpine hare is indigenous,
while the common hare is absent, implies that, so far as relates to the
former animal, the barrier did not exist." The Beaver, Dormouse, and
Common Hare are either Siberians or later migrants from elsewhere, and
there can be no doubt that at the Forest-Bed period Ireland was already,
or was just being, separated from England. All the southern species,
that is to say all the Lusitanian, Alpine, and Oriental forms occurring
in Ireland, must therefore be older than that period. I have advocated
similar views in a former essay on this subject. Mr. Carpenter recently
advanced some interesting and valuable criticisms on these views, which
we may examine a little more closely (p. 385). "While, then," he
remarks, "I find myself in almost complete agreement with Dr. Scharff
with regard to the older sections of our fauna, I think that those
widespread species which survived the Glacial period must have been
confined to the more southern parts of our area, and have only
subsequently spread northwards and westwards to Scotland and Ireland."
He suggests, in fact, that the widespread British species belong to a
younger or newer section of our fauna than the local ones. In many cases
this may be quite true, but we possess also a large number of common and
widely-spread forms which bear the impress of antiquity upon them. We
have the most positive proof of the antiquity of the very common small
circular Snail (_Helix rotundata_), since it was found in miocene
freshwater deposits near Bordeaux. Many other examples might be
mentioned to show that, though discontinuous range is generally a proof
of antiquity, continuous range is not always a sign of the opposite.
Some species, in fact, appear to be short-lived and disinclined to
spread, whilst others multiply rapidly even under a change of
temperature and climate, and are to be found almost everywhere. But even
if we supposed, with Mr. Carpenter, that these widely-ranging species
must have been confined during the Glacial period to the more southern
parts of England, the idea that they afterwards made their way
northwards along the eastern shore of the Irish Sea and then passed into
Ireland, does not appeal to me. Southern England was occupied at that
very same time by an assemblage of Siberian mammals. Mr. Carpenter
thinks these might have been kept out of Ireland by an arm of the sea
until the land-connection with North-western England had broken down.
But if an arm of the sea could keep out the Siberian mammals it would
also keep out the widely-spread British species of the general fauna. On
the other hand, I quite admit that my view of the survival in Ireland
of the pre-glacial fauna is somewhat difficult to accept, considering
that we have such undoubted evidence of a very extensive submergence.
The case of Isle of Man, quoted by Mr. Carpenter, can be met, I think,
by the supposition that it was connected with Cumberland until quite
recently, and quite independently of any connection between England and
Ireland; that the Isle of Man, in fact, was always a cape or peninsula
of the mainland, and only recently became separated by local subsidences
or by the action of the sea.

Part of the history of the British fauna will be referred to again in
the next chapter, which deals with the Arctic migration. We need not
therefore dwell any longer on this subject here. There is one matter,
however, which is of importance in connection with the geographical
conditions of the British Islands at the time when the greater portion
of our fauna arrived from abroad.

On page 60 will be found a map indicating the physical geography of that
part of the ancient continent on which what are now the British Islands
were situated. Only one large river has been marked on that map, namely,
that flowing out of a lake which occupied part of the Irish Sea. Another
probably discharged its waters into the Atlantic midway between France
and England, whilst the Thames may have been a tributary of the Rhine,
as it emptied itself into the sea near our south-east coast. I have
shown in a previous essay that the former presence of a freshwater lake
between England and Ireland is indicated by the distribution of the
Charrs and also by the various species of British Coregonus. There are
three British species of Coregonus, viz., _C. clupeoides_, _C.
vandesius_, and _C. pollan_. These are confined to the lakes of North
Wales, North-western England, South-western Scotland, and Ireland. All
but the latter communicate at present directly with the Irish Sea. The
lakes of the latter country, however, must have done so at a time when
the west of Ireland stood at a higher level than it does now. The
ancestors of the three Coregonus species, and also those of the Charrs,
then lived in the large freshwater lake indicated on the map (p. 60),
and when the sea gradually crept up the river valley and finally
converted the lake into a gulf, the freshwater fish took refuge in the
rivers which supplied it with water.

Now as for the continuous sea-shore between the coast of Brittany and
the south-west of Ireland, zoological distribution again aids us in
proving that such must have actually existed at no very distant
geological date. Most of our common shore forms of life migrate along
the coast exactly as land animals do--step by step. Their eggs are
carefully attached to fixed objects, so as not to be carried away by the
waves, whilst the young often remain and grow old in some particular
little pool, rarely venturing farther than a few yards from the spot
where they first saw the light of day. A number of such shore forms are
found on the west coast of France, the same species recurring again on
the south-west coasts of England and Ireland, thus clearly indicating a
former continuity of coast-line between these points, now separated by
deep sea. A very familiar example to British zoologists is the purple
rock-boring Sea-urchin (_Strongylocentrotus lividus_), but there are a
great many others, such as the semi-marine Beetles _Octhebius Lejolisii_
and _Æpophilus Bonnairei_, the Crustaceans _Achæus Cranchii_, _Inachus
leptochirus_, _Gonoplax angulata_, _Thia assidua_, _Callianassa
subterranea_, the Fishes _Blennius galerita_ and _Lepadogaster
Decandollii_, and the Molluscs _Otina otis_, _Donax politus_, and
_Amphidesma castaneum_.

Before concluding this chapter, a few words as to my views on the
conditions prevailing during the Glacial period will not be out of
place. They do not differ very much from those held formerly by most
geologists; and even at present there are, as I have mentioned before, a
few upholders of those older views.

The sea, I think, must have gradually crept across England from the east
during, or shortly after, the Forest-Bed period, so as to separate the
south from the north, whilst Ireland and Scotland were then still
connected with one another. At a later stage, the sea also partially
invaded Ireland, and this condition is very roughly represented on the
accompanying map. Mr. Kendall kindly drew my attention to the fact that
several notable areas on which shelly drift has been observed are here
placed upon the land; but it must be remembered that one stage only can
be shown on the map, and that the sea covered more ground a little
later. Many of the smaller islands in the glacial sea, too, are not
shown. The map, in fact, is merely meant to give a general idea of the
manner in which the great northern sea moved westward and slowly covered
a large portion of the British Islands. These peculiar geographical
conditions explain, I think, better than anything, the absence from
parts of the Midlands and the north of England of such a number of
terrestrial invertebrates which are otherwise widely distributed over
the British Islands. In spite of the fact that a large portion of the
British Islands became submerged, we possessed at that time an extensive
area which has since been claimed by the sea, so that there was ample
room for the present fauna to survive the Glacial period. The climate
during this period was probably much the same as it is at present,
though moister, with cooler summers and milder winters.

[Illustration: Fig. 6.--Map of the British Islands, showing
approximately in what manner the sea may have invaded the country from
the east during, or shortly after, the Forest-Bed period. The darkly
shaded parts indicate the areas covered by water, and the lightly shaded
and white portions what was land at that time.]

It may be asked what proof we have of such an extensive submergence of
England and Ireland. My own views are principally based on the general
distribution of the fauna in the British Islands, and the belief that
nothing but a mild climate during the Glacial period could have brought
it about. On purely geological grounds, however, some geologists,
notably Mr. Mellard Reade, have come to a similar conclusion. "The whole
of Lancashire and Cheshire," he remarks (_a_, p. 542), "from sea-level
up to about 400 feet, and in places 600 feet, is covered by a continuous
mantle of boulder-clay and sands." "These clays, as a rule, contain
distributed through them, in a greater or less degree, fragments of
shells and some perfect ones. I myself have recorded forty-four
species." Again he continues (pp. 545 and 546): "A large part of
Ayrshire is covered with similar shelly boulder-clays from sea-level to
1061 feet at Dippal. These Ayrshire high-level shells have, in the
majority of cases, been taken, not from sand and gravel beds, but from
boulder-clay, and in that respect they are most important and unique. In
Moel Tryfan the shells are found in sands and gravels at 982 feet; on
the range of hills from Miaera to Llangollen from 1000-1200 feet; also
in sands and gravels at Gloppa, near Oswestry, at 1100-1200 feet; and
near Macclesfield at a level of about 1200 feet. In Ireland marine
shells can be traced almost from sea-level to a height of over 1000
feet."

"Again," continues the same author, "if we look broadly at the
distribution of these shelly deposits, we find that they occur all round
our maritime coasts in Lancashire, Cheshire, and Wales, in Cumberland
and Westmoreland, Wigtonshire and Ayrshire, and along the eastern coast
of Ireland. The same is to be said of the eastern coasts of England and
Scotland."

That a very considerable change of sea-level has taken place in some
parts of the British Islands would appear to a zoologist the most
logical conclusion after an examination of these "high-level shelly
sands and gravels," but the shells contained in them are now generally
supposed to have been carried there frozen in the sole of a glacier or
pushed up in front of it. The older view, however, which agrees so much
better with the facts of distribution, fortunately has not disappeared
among geologists. "When we call up," says Mr. Mellard Reade (_b_, p.
435), "before our mental vision the simple and well-known facts of
nature which suffice to explain the marine drifts on the theory of
submergence, it seems unnecessary to resort to the ingenious and
artificial system of physics elaborated to explain the phenomena of
land-ice."

"When we have more knowledge of the glaciers of the Arctic Regions, and
facts, in place of ingenious suppositions, to base our reasoning upon,
we may possibly have to revise all our glacial conceptions. In the
meantime, the submergence theory of the origin of high-level shelly
gravels and sands seems to me by far the simpler of the two theories,
and the most consistent with the facts and phenomena which the labours
of a succession of enthusiastic geologists have made us acquainted
with."

Among those geologists, and they form the majority, who hold that
Ireland was covered by land-ice, there is a great diversity of opinion
as to its extent. Messrs. Close, Kinahan, J. Geikie, and others believe
that the ice covered practically everything, whilst others who claim to
have examined the ground with equal care, such as Professor Carvill
Lewis, were led to believe that the south of Ireland, with the exception
of a few local glaciers, was free from ice. The glacial phenomena of
the country can therefore be interpreted in different ways, even by
those who are convinced that they are due to land-ice and not to
icebergs or mud-glaciers.


SUMMARY OF CHAPTER III.

The history of the British fauna is not only of interest to us from a
sentimental point of view, it is a convenient starting-point in the
study of the larger European problem. The fauna, broadly speaking, is
composed of three foreign elements, viz., the northern, eastern, and
southern, to which may be added a small endemic one. Examples are given
of the more noteworthy forms belonging to each of these. This leads us
to the subject of the natural divisions of the British Islands according
to their animal inhabitants. Zoologists attempted at first to subdivide
these countries, on the lines laid down by botanists, into a large
number of provinces. Forbes proposed ten such divisions for mollusca,
and subsequently five, which were ultimately reduced by others to two or
three.

The opinions of biologists are almost unanimous in attributing the bulk
of the British fauna and flora to migrations by land from the Continent,
but two other theories, viz., those of Professor Cole and Messrs.
Kinahan and Lamplugh, are also referred to. The first believes in a
possible migration eastward from Western Europe, and the latter support
the view of the former existence of ice-bridges to assist the fauna in
their migrations.

An endeavour is next made to determine at what geological periods the
various migrations entered the British Islands. There is considerable
difference of opinion on this subject. Some believe that the British
fauna is altogether post-glacial; a few think that it is partly so and
the remainder glacial; others again hold that a portion is pre-glacial
and the rest glacial and post-glacial. Those who have studied the
subject most closely feel convinced that the south-western or Lusitanian
fauna, and also the flora, must have arrived before the Glacial period
and survived the latter in these Islands. It seems reasonable to
suppose, therefore, that the climate cannot have been very severe during
the so-called Ice-Age. This Lusitanian fauna must be looked upon as the
oldest portion of the British fauna. The Alpine and Oriental migrations
arrived next. After these came the Arctic, and finally the Eastern or
Siberian. As the fossil evidence is most complete with regard to the
last, we are able to determine with precision not only the direction
whence this migration came, but approximately its geological age. It
arrived in Germany from the east after the deposition of the lower
boulder-clay. Since the boulder-clay is looked upon as a glacial
deposit, the Siberian migration reached Central Europe after the first
portion of the Glacial period had passed. In England it makes its first
appearance in the Forest-Bed, which would therefore correspond to the
"Loess" formation of Central Europe. All the other migrations are older
than the Siberian. They must therefore have come to Great Britain during
the earlier part of the Glacial period or before it.

The chapter concludes with a short statement on the physical geography
of the British Islands during the time when these migrations entered
them. That there existed a continuous coast-line between France and
Ireland is proved by the occurrence of a considerable number of
identical shore species, whilst the former existence of a freshwater
lake on the site of the present Irish Sea is indicated by the
distribution of some freshwater fishes.




CHAPTER IV.

THE ARCTIC FAUNA.


The lands lying within the Polar Circle are inhabited by an assemblage
of animals and plants, many of which are peculiar to those regions. They
are mostly adapted to the abnormal conditions of life prevailing in the
high latitudes of our globe--the long, dark winters, and the short
summers of one long day. Though the numbers of species and of
individuals are few, there is a keen struggle for existence in those
regions. The prevailing colour of the ground is white, and since a
resemblance in the colour of an animal to the ground it lives on acts as
a protection to weak ones, and also enables Carnivores to approach their
prey with greater facility, it is not surprising that we should find the
majority of polar animals coloured white. As I remarked, the polar area
contains a very distinct set of species; most of them, however, range
beyond the confines of the Arctic Circle. It is therefore scarcely
justifiable to raise this Arctic area into a distinct zoological region
equivalent to the great zoogeographic regions, which have been
established by Sclater and Wallace, though we might, with Dr. Brauer,
look upon it as a sub-region.

There are six typical Polar Land-mammals, one of which, the Polar Bear,
is semi-aquatic. The Reindeer (_Rangifer tarandus_) occurs upon almost
all the polar lands, and it has often been a source of speculation in
what manner it has reached such remote islands as Spitsbergen and Novaya
Zemlya--the former of the two being so remote from a continent. There is
no doubt that Reindeer are great wanderers, owing to the difficulty of
finding sufficient food-supply for the large herds in which they are
accustomed to travel; and for this reason they can cross, and have been
known to cross, distances of from ten to twenty miles on ice. The
Behring Straits, when frozen over in winter, is frequently traversed by
them. But I quite agree with Dr. Brauer (p. 260) that it is impossible
to account for their presence in Spitsbergen by an immigration from
either Novaya Zemlya, Greenland, or Scandinavia, under the present
geographical conditions. The seas between the former island and the
other land-masses referred to are rarely entirely frozen over. Even if
this should occur, the distances between Spitsbergen and Greenland,
Novaya Zemlya, or Scandinavia are so great, that a migration across ice
is quite excluded from the range of possibilities, since Reindeer could
not subsist without food during the time it would take to travel from
one to the other. The manner in which it did reach Spitsbergen and
Greenland will be discussed more fully below, and I will therefore
proceed to mention the other Arctic mammals.

One of the most important and most typical species is the Polar Bear
(_Ursus maritimus_), the greater part of whose life is spent on the ice
and in the sea. The fact that its favourite nourishment consists of
seals proves its excellent and keen faculties of sight and hearing, and
its facility in swimming. But it is not a dainty feeder, and lives upon
almost all animals which come within its reach; birds, land-mammals, or
fish are not despised in times of scarcity. Its fur throughout the year
is coloured white, though in old bears it assumes a more yellowish hue.

[Illustration: Fig. 7.--The Musk-Ox (_Ovibos moschatus_). (From Flower &
Lydekker's _Mammals_, p. 358. London: Adam & Chas. Black.)]

Another large mammal, perhaps less well known, is the Musk-Ox (_Ovibos
moschatus_, Fig. 7), which resembles in size the smaller varieties of
Oxen, but in structure and habits is closely allied to the Sheep. As is
implied by the specific name, it exhales a musky odour; this does not,
however, appear to be due to the secretion of a special gland, as is the
case in other animals with a similar smell. The skin is covered with
long brown thickly-matted hair, interspersed with white. It is confined
to the most northerly parts of North America and the American Arctic
islands, and to North Greenland. Though not now living in the Old World,
it seems formerly to have been abundant in Siberia, and, as we shall
learn later on, it was one of the species which took part in the great
Siberian invasion of Europe. Its remains have been found not only in
Germany and France, but also in the south of England.

The Polar Fox (_Canis lagopus_) occurs throughout the Polar Regions, and
on islands where even the Reindeer and the Musk-Ox are unknown. Beyond
the Polar Circle, its range extends into Northern Asia, to the extreme
north of North America, and the mountains of Scandinavia. Like its
congeners, it had in pleistocene times a more southerly extension, and
fossil remains have been met with in various parts of continental Europe
and in England.

The Stoat (_Mustela erminea_), which is known and much valued in
commerce under the name of Ermine, was formerly believed to occur only
in Arctic America and the northern parts of the Old World, but in more
recent years it has been discovered in a number of the northern
islands, such as Saghalien, in the islands of the Behring Straits, the
Aleutian islands, and also in Greenland and Spitsbergen. In Europe, it
is found as far south as the Arctic Hare, or perhaps even farther, and
it flourishes in the Alps up to a height of 9000 feet. It offers a
parallel to the Arctic Hare in the fact that in some countries, such as
Ireland, it only rarely turns white in winter. The Irish form of the
Stoat differs so much from the English, that Messrs. Thomas and
Barrett-Hamilton are of opinion that it is specifically distinct, as I
mentioned in speaking of the divisions of the British fauna (p. 90).

The Arctic Hare (_Lepus variabilis_) is almost the only one of the
typical Arctic mammals which still inhabits the British Islands, and for
that reason it is to most of us more familiar than any of the preceding
species. Hares have been described from Greenland by the name of _Lepus
glacialis_, from the European Alps as _Lepus alpinus_, and under other
names from Arctic North America; but though slight differences in the
fur and even in the skull can be pointed out, there is no doubt that all
these are only varieties or races of what, in the British Islands, is
known as the Irish or the Scotch Mountain Hare, _Lepus variabilis_. In
the Arctic Regions this Hare remains white throughout the year, but in
Scandinavia and some other parts its fur becomes brown in the summer,
and in Ireland it frequently remains entirely brown during the whole
year, and never, or only in very rare cases, becomes entirely white in
winter. Besides Scandinavia, Scotland, and Ireland, it is found in
Northern Russia, and also in the Pyrenees, the Alps, and the Caucasus.
In Asia it occurs not only on the mainland of Siberia, but it has been
obtained on the Akita Mountains in Japan and on the Mioko San Mountain,
and also on the island of Saghalien. It had in former times a more
extensive range, and its remains have been discovered in England and in
a number of places on the continent of Europe. The peculiarity of its
range, which will be explained more fully directly, lies in the fact of
the occurrence of isolated colonies in the mountains of Europe, in
Ireland and Scotland, and in the mountains of Japan (Fig. 8). From a
distributional point of view, it is one of the most interesting species
of mammals, and its history throws a flood of light on the geographical
changes which have occurred in former times.

[Illustration: Fig. 8.--Map of the northern hemisphere, to show the
geographical distribution of the Arctic Hare (_Lepus variabilis_)
indicated in black.]

One more species must be mentioned, and that is the Banded Lemming
(_Cuniculus torquatus_), which occurs chiefly in Arctic America,
Northern Siberia, and Greenland. Though frequently mistaken for the
Scandinavian Lemming, there is a striking difference in the character of
the teeth, which has induced zoologists to put them into distinct
genera. The Arctic Lemming, moreover, is distinguished from the
Scandinavian by the absence of external ears, the densely furred feet,
and by the great length of the two middle claws in the fore-feet. There
are two species of the true Lemming, namely, the one just referred to,
_Myodus lemmus_, and _Myodus obensis_. These may be looked upon as more
or less Arctic species, since they occur within the Polar Circle, but
they are not so exclusively confined to that region as the Banded
Lemming (_Cuniculus torquatus_). The remains of both _Cuniculus
torquatus_ and of _Myodus lemmus_ have been found in British pleistocene
deposits.

Until recently no Lemming remains had been found to the south of
France, but Mr. Barrett-Hamilton announced to us a short time since that
Dr. Gadow had discovered some skeletons with their skins still preserved
in a cave in Northern Portugal. These were found to belong to the
Scandinavian Lemming (_M. lemmus_), and the author incidentally
expressed the opinion that there was some possibility of this species
still inhabiting the mountains of Spain.

The Lemming multiplies with great rapidity under favourable conditions.
In speaking of his experiences in Siberia Dr. Brehm says (p. 79): "All
the young of the first litter of the various Lemming females thrive, and
six weeks later at the most these also multiply. Meanwhile the parents
have brought forth a second and a third litter, and these in their turn
bring forth young. Within three months the heights and low grounds of
the tundra teem with lemmings, just as our fields do with mice under
similar circumstances. Whichever way we turn we see the busy little
creatures, dozens at a single glance, thousands in the course of an
hour. But the countless and still increasing numbers prove their own
destruction. Soon the lean tundra ceases to afford employment enough for
their greedy teeth. Famine threatens, perhaps actually sets in. The
anxious animals crowd together and begin their march, hundreds join with
hundreds, thousands with other thousands, the troops become swarms, the
swarms armies. They travel in a definite direction, at first following
old tracks, but soon striking out new ones; in unending files--defying
all computation--they hasten onwards; over the cliffs they plunge into
the water. Thousands fall victims to want and hunger; the army behind
streams on over their corpses; hundreds of thousands are drowned in the
water or are shattered at the foot of the cliffs; the remainder speed
on; other hundreds and thousands fall victims to the voracity of Arctic
and red foxes, wolves and gluttons, rough-legged buzzards and ravens,
owls and skuas which have followed them; the survivors pay no heed.
Where these go, how they end, none can say; but certain it is, that the
tundra behind them is as if dead, that a number of years pass ere the
few who have remained behind and have managed to survive slowly multiply
and visibly re-people their native fields." This eloquent passage
reminds us of the manner in which migrations of all kinds of animals
have taken place in former times, and are still taking place. It is
principally want of food which compels them to search for new homes.

On page 91 I have referred to some birds which have come to us from the
north. One of these, the Snow Bunting (_Plectrophenax nivalis_), is a
typically Arctic species. In summer it is widely distributed, and is
found in Spitsbergen, Novaya Zemlya, Siberia, and the Arctic Regions
generally. In winter it migrates down into North America, into Japan,
Northern China, Turkestan, Southern Russia, and occasionally even across
Europe into North Africa. Very characteristic Arctic birds are the Eider
Ducks belonging to the genus _Somateria_. Three species have visited
the British Islands. The common Eider Duck (_S. mollissima_), which is
of such high commercial value, is abundant in Norway and northward,
throughout the Polar Regions. The appearance of the King Eider (_S.
spectabilis_) on our coasts is an extremely rare occurrence, and even in
Norway it is only known as a visitor, but on Novaya Zemlya and along the
Arctic shores of Siberia, in Greenland and Arctic North America, it is
known to breed. The third species, Steller's Eider (_S. Stelleri_),
seems to be still rarer, and only in the Aleutian islands and in the
north of Alaska can it be said to be at all abundant. It is probable
that the famous Great Auk (_Alca impennis_, Fig. 9) also was a typical
Arctic species. Its range extended to both sides of the Atlantic. In
Newfoundland and on the coast of Iceland it is known to have been met
with in considerable numbers within historic times; and no doubt, like
all Arctic species, it extended farther southwards at a more remote
period.

[Illustration: Fig. 9.--The Great Auk (_Alca impennis_).]

The members of the genus _Lagopus_, including the various species of
Grouse, are likewise of northern origin. The British Red Grouse (_L.
scoticus_), which may be looked upon as a form of the Scandinavian
Willow Grouse (_L. albus_) (compare p. 91), constitutes in some respects
a curious case of parallelism with the Arctic Hare, since the latter, in
its more southern station, generally retains the summer fur throughout
the year. The allied Ptarmigan (_L. mutus_) inhabits Scandinavia, the
Ural Mountains, and some of the Asiatic mountain ranges. It is also
found in the European Alps and in the Pyrenees. The North European range
of the Ptarmigan suggests that we are dealing with an ancient species
which came south from the Arctic Regions at about the same time as the
Arctic Hare; but it is more probable, as I have shown in a subsequent
chapter (p. 334), that this species has entered Europe more recently
with the Siberian migrants from Central Asia, where indeed the genus had
its original home. The Black Cock (_Tetrao tetrix_) and the Capercaillie
(_Tetrao urogallus_) have also come to us from the east, and have even
penetrated into Ireland. They are therefore some of the few instances of
members of the Siberian invasion having become temporarily established
there.

Reptiles and amphibia are altogether unknown in the Polar Regions, but a
large number of fish, chiefly marine, have taken their origin there. The
Salmon family are of Arctic origin, as also are the Sticklebacks and the
Perches, many of the Cod family, the Herrings, and several of the Flat
fish.

It would lead me too far to refer to the invertebrate fauna of the Polar
Regions, but a few remarks on the Arctic plants may not be out of place.

The principal Arctic genera are Salix, Ranunculus, Draba, Pedicularis,
Potentilla, Saxifraga, Carex, Juncus, Luzula, Eriophorum, and others.

Among the most characteristic Arctic plants may be mentioned _Dryas
octopetala_, to which I have already referred as occurring in the west
of Ireland; _Saxifraga oppositifolia_, another British species, occurs
in the higher mountains of Scotland, Ireland, and Wales; _Braya alpina_,
_Papaver nudicaule_, _Lychnis apetala_, _Diapensia lapponica_, and
_Lobelia Dortmanna_, which is found in the lakes of Scotland and
Ireland. The dwarf birch (_Betula nana_) also, which still occurs in
Scotland and the North of England, and which had formerly a wider range
in the British Islands, should be included among these; but there are
other plants probably of Arctic origin, though not now occurring in the
Arctic Regions, and to these may be classed the so-called American
species of plants which are found on the northern and western coasts of
Ireland, in the Hebrides, in Scotland, and in North America. These are
no doubt the relics of an Arctic flora which flourished in high
latitudes in past times when the climate there was more temperate. A
list of these species will be found on page 166.

As none of them occur in Siberia, they must either have found their way
to North America and to Europe from the Arctic Regions, or have
travelled from North America across the latter to Europe. In any case a
former land-connection between the two continents must have existed.
This becomes the more evident when we examine the remarkable results
obtained by the late Professor Heer, who first described the Tertiary
plant-beds in North Greenland. No less than 282 species of plants have
been described by this eminent botanist from these deposits. A large
number of the plants found were trees belonging to the genus _Sequoia_,
_Thujopsis_, and _Salisburia_, besides beeches, oaks, planes, poplars,
limes, and magnolias. That they grew on the spot is proved by the
fruits, which have been obtained from these beds in various stages of
growth.

From a similar deposit in Spitsbergen a large number of fossil plants
have also been brought to light, many of which are identical with those
found in Greenland; and some of the Greenland forms (such as _Taxodium
distichum_ and _Sequoia Langsdorfii_) have been found too in Alaska,
showing that there was probably a continuity of land between Spitsbergen
and North America by way of Greenland. Two species of _Sequoias_,
namely, _S. sempervirens_ and _S. gigantea_, the well-known Californian
giant trees, are very closely allied to the Greenland forms discovered
by Professor Heer.

Heer assigned the Arctic plant-bearing beds to the Miocene epoch, but
doubts have been recently thrown upon this opinion by Mr. Starkie
Gardner, who brought forward arguments in support of his theory of their
being of the Eocene age. Professor Heer, however, was able to meet these
criticisms, and he is ably supported in his views by Professor Engler
and other eminent continental botanists.

It is evident that under the present conditions of temperature none of
those plants could have flourished in Greenland. The climate must have
been much milder than it is at present. Professor Heer estimated from
the general aspect of the fossil flora that the mean annual temperature
of North Greenland was at least nine degrees centigrade, and that the
mean winter temperature was not below zero.

It will hardly be necessary for me to review here the various theories
which have been advanced by geologists and botanists to account for this
remarkably high temperature in such northern latitudes. Any one who has
read the writings of the late Dr. Croll cannot help being struck by the
facts he adduces to show the importance of ocean currents in relation to
the distribution of heat over the globe, and it seems to me that the
view which attributes the mild climate prevailing in former times in
Greenland to warm ocean currents reaching the Polar Circle is the one
least open to serious objections. If we suppose that the North Atlantic
Ocean was bridged by a land-connection between Scandinavia and Greenland
by way of Spitsbergen, and between Greenland and North America, the
Polar Ocean would be practically a closed sea. If, then, a wide passage
existed somewhere about Behring Straits to allow a warm current to enter
and circulate within the Arctic Seas, we should have the southern shores
of Greenland washed by the warm Atlantic current and the northern shores
by a warm Pacific current, which combination would undoubtedly produce
the effect of raising the temperature throughout the Polar Regions very
considerably; and especially would that be the case with regard to
Greenland and the neighbouring islands.

It might be urged that the constant darkness during winter must have had
an injurious action upon the flora, but it is found that in countries
such as Northern Russia, where southern plants are housed during winter
in greenhouses, the light being almost entirely excluded by a covering
of straw, no serious damage is done thereby to the plants.

It seems probable that a similar gradual refrigeration of climate in
northern latitudes has taken place after Miocene times as has been
proved to have occurred in Europe.

Some years ago Dr. Haacke propounded the hypothesis that the centre of
creation of all the larger groups of animals was situated in the region
of the North Pole, and that the newly originated groups must always push
the older ones farther and farther south into the most remote corners of
the earth. As instances of the correctness of his view he quotes the
fact that the more ancient mammals, such as Monotremes, Marsupials,
Lemurs, Edentates, and Insectivores, all inhabit the more southerly
parts of the world. The Apteryx, Moa, Rhea, and the Ostrich, as well as
Æpyornis, which is only recently extinct, are found in the same regions.
But we have no palæontological evidence in favour of these extravagant
views. Fossil Edentates and Marsupials are almost entirely confined to
the Southern Hemisphere, and the supposition that because these
primitive mammals inhabit the extreme south of our great continental
land-masses, they therefore came from the north, cannot be said to be an
argument. Nevertheless, I am quite with Dr. Haacke in considering that
the North Pole, or, we might say, the lands within the Arctic Circle,
have been the place of origin of some of our European mammals, and there
can be no doubt that certain species in other groups, among
invertebrates and also plants, have originated in the Polar Regions.
The facts of geographical distribution teach us that in these regions
there has been a centre of origin within comparatively recent geological
times. I have on a previous occasion drawn attention to the range of the
Reindeer: that it lives almost throughout the Polar lands, and that it
spreads into North America, Northern Europe, and Northern Asia. We have,
again, fossil proof that its range extended down to the Pyrenees in
Europe in pleistocene times. But there is not a scrap of evidence that
it ever during any time occurred farther south, either in Europe, Asia,
or North America. Its original home must therefore have been in the
Polar Regions, for if it had originated either in Central Europe, Asia,
or America, there is no reason why it should not, in the natural course
of events, have extended its range to the south as well as to the north.

The Arctic Hare presents us with a very similar case of distribution.
Like the Reindeer, it inhabits, as we have learned, the Polar Regions
and the northerly parts of the Old World and the New; but while we have
only fossil evidence of the former, more southerly, extension of the
range of the Reindeer, the Arctic Hare furnishes us with a still
stronger proof of its past southward range in the survival of small
isolated colonies in some of the southern mountain ranges of Europe and
Asia. It is generally believed that the occurrence of the Arctic Hare in
these southern mountains is a standing testimony to the severity of the
climate at the time when it commenced its southerly increase of range,
but I have already shown that the climate of Europe at that time was not
necessarily colder than it is at present, but that it may have been
somewhat milder (p. 80). I think that a vast increase of ice in the
Polar Regions has taken place only at a comparatively recent date, and
that both the Reindeer and the Arctic Hare originated there during a
much more temperate climate than obtains at present. A great sensation
was produced among European zoologists and anthropologists when the
discovery was first announced that the remains of the Reindeer had been
found in the Pyrenees, and it naturally gave rise to many speculations
as to the nature of the climate at the time when its range extended so
far south.[1] The greater number of our best authorities are still of
opinion that the existence of the Reindeer in Southern Europe points to
the prevalence of an arctic climate in that region. It is generally
overlooked, however, that the Reindeer-remains occur in company with
many typically southern animals, which, if they had been found alone,
would have been held to be a certain indication of a warm climate. The
French geologist Professor Lartet, indeed, was of opinion that the
temperature during the time when the Reindeer lived in the Pyrenees must
have been rather milder than it is at present (compare pp. 71-75).
Similarly, Mr. Harlé argues, that the extremely cold climate probably
did not extend to South-western France, since that area only received
occasional visits from some of the representatives of the Arctic fauna.

Long ago North American zoologists recognised the existence in their
country of two well-marked races of the Reindeer (Caribou)--a smaller
one with rounded antlers (Fig. 10), and a larger one in which the
antlers are more or less flattened out (Fig. 11). Two somewhat similar
races can also be traced in the fossil remains of the Reindeer in
Europe. It was, I think, Gervais who first pointed out that the Reindeer
remains from the north of France differed from those found in the south;
and Lartet referred to the fact that the southern remains were more like
what, in America, is called the Barren-ground Caribou, while those from
Central European deposits all belonged to the Siberian variety, which is
more like the Woodland Caribou of North America. In Ireland, Professor
Leith Adams also drew attention to the curious fact that all the Irish
Reindeer remains resemble the Norwegian variety rather than the
Siberian; and Mr. Murray was so much struck by the close resemblance
between the Spitsbergen and Greenland forms with the Barren-ground
Caribou, that he based some speculations on a former land-connection
between these countries on this circumstance.

[Illustration: Fig. 10.--Head of a Barren-ground Reindeer in the Dublin
Museum (photographed by Mr. McGoogan).]

[Illustration: Fig. 11.--Head of a Woodland Reindeer in the Dublin
Museum (photographed by Mr. McGoogan).]

We have, therefore, records of the present or the former existence of a
Reindeer resembling the North American Barren-ground form in Greenland,
Spitsbergen, Scandinavia, Ireland, and the South of France. In England
the remains of the two forms occur mixed, but I do not know in how far
either the one or the other predominates. The Barren-ground Reindeer is
in Europe altogether confined to the west; the most easterly locality
that I am acquainted with being Rixdorf, near Berlin. The majority of
the European remains of the Reindeer seem to belong to the Siberian or
Woodland variety, and it would appear as if some intercrossing between
the two forms had occurred in Lapland, since it is stated that in that
country the Reindeer is somewhat intermediate between the two. All the
Asiatic remains also resemble the Woodland variety.

As far as I know, no explanation has been attempted to account for this
peculiar range in Europe of the two forms of Reindeer. But if we look
more closely into the mode of occurrence of the Reindeer remains, we
find that the Barren-ground form, seems to have existed in Western
Europe long before the other variety made its appearance there. It was
pointed out by Struckmann that the Reindeer in Southern Europe occurs in
older deposits than in the north. In speaking of the northern ones, he
had of course chiefly the German deposits in view. It is in one of the
oldest pleistocene deposits in Germany that the isolated instance,
referred to above, of the occurrence of the Barren-ground Reindeer, near
Berlin, has been noted.

There is still a further point which illustrates the supposition that
the Barren-ground Reindeer was a more ancient inhabitant of Europe than
the Woodland one. The latter in all Central European stations (in fact
almost wherever it occurs fossil) is associated with the remains of the
typical inhabitants of Siberia, such as the Glutton, Sousliks, Lemmings,
and others; but in the deposits in which the Barren-ground Reindeer have
been found in South-western France, no other Arctic mammal finds a
place. Again, in Irish deposits none of the Siberian migrants are found.
The only explanation of this remarkable fact is that the two varieties
of the Reindeer have come to Europe by different routes. We have learned
already from the observations of Mr. Murray that there are evidences of
the existence of a former land-connection between North America,
Greenland, and Spitsbergen. Professor Petersen tells us that, according
to recent surveys, a high submarine plateau with a sharp fall of 1000
fathoms towards the Atlantic Ocean begins from Northern Norway and is
continued as far as Spitsbergen. Several islands, such as Bear Island,
King Charles Land, and others, arise from this plateau, and these must
be looked upon as the remains of a sunken land (Fig. 12).

From Arctic America, thinks Professor Schulz (p. 1), we probably have
had an uninterrupted migration during the greater part of later Tertiary
times up to the commencement of the Pliocene epoch--partly over a direct
land-connection between Greenland, Iceland, and the Faroes, and also
between Arctic America, Spitsbergen, Franz Josef Land, etc. There was
also a connection between Asia and Alaska.

The distribution of the Barren-ground Reindeer in Europe seems to
warrant the belief that, at the time it began its southward wanderings
from the Polar area, Northern Norway must have been connected with
Greenland in the manner just indicated, but, as I shall explain later
on, Russian Lapland and part of Northern Russia, or the land between the
White Sea and the Baltic, must at that time have been submerged by the
sea. The greater part of Denmark and the lowlands of Sweden were
likewise submerged, but Scandinavia extended south as far as Scotland,
while Scotland was connected with Ireland, and the latter with England
and France. The Reindeer migrating south into Scandinavia could only
reach the continent of Europe by way of the British Islands. It appeared
there in the west and gradually extended its range east, where, as I
mentioned above, it has occurred in a few isolated localities.

The advent of the Woodland form of the Reindeer in Europe took place at
a much later stage. It came, as I indicated, with the hordes of
Siberian migrants which invaded Europe during what is known as the
Inter-glacial phase of the Glacial period. Scandinavia, not being then
directly connected with continental Europe, was not accessible to it;
neither was Ireland, which had by that time become disconnected from
Great Britain. None of the Siberian migrants seem to have been able to
cross the River Garonne, and we therefore find neither the Woodland
Reindeer nor any of the typical Siberian species represented in the
Pyrenean deposits.

[Illustration: Fig. 12.--Map of Europe, indicating the parts which were
probably submerged (shaded) at the commencement of the Glacial period.
The light portions represent, approximately, the extent of the land at
that time.]

The Woodland Reindeer persisted in continental Europe until
comparatively recent times, and it has since made its way into
Scandinavia across Northern Russia, and probably mingled with the older
stock of the Barren-ground form. In the same way, it may have come about
that in the English pleistocene deposits the remains of the two races
occur.

In a recent contribution to our knowledge of the deer tribe (_c_, p.
88), Mr. Lydekker suggests that the former division of the Reindeer
races into the two forms of Woodland and Barren-ground Caribou, no
longer holds good. He now recognises no less than six races, as
follows:--

  1. Rangifer tarandus typicus.
  2.    "        "     spitzbergensis.
  3.    "        "     caribou.
  4.    "        "     terræ-novæ.
  5.    "        "     grœnlandicus.
  6.    "        "     arcticus.

I hardly think these can be considered of equal value; indeed, though
there may be differences between _R. grœnlandicus_, _typicus_,
_arcticus_, and _spitzbergensis_, the antlers exhibit a certain much
closer relationship among one another than to _R. terræ-novæ_ and
_caribou_. But the whole subject is by no means as well known as could
be wished, and a very careful comparative study of recent and fossil
remains of the Reindeer from various parts of the Old and New Worlds is
much needed to put our views on a firmer basis.

The presence of the Arctic Hare in Ireland and the absence of the common
European Hare (_Lepus europæus_) can be explained in a somewhat similar
manner. The Arctic Hare is the older of the two species--corresponding
with the Barren-ground Reindeer--and the European Hare the newer one,
associating, like the Woodland Reindeer, in its westward migration with
Siberian animals, though probably of Oriental origin.

Let us once more refer back again to the map on page 137 indicating the
geographical distribution of the Arctic Hare. Its discontinuous range
and its isolated position in the Alps, Pyrenees, and the Japanese
mountains, all tend to show that it is an ancient species. Moreover, its
presence in Ireland in the plain as well as in the mountains, clearly
points to the fact that, in the British Islands at any rate, the Arctic
Hare was the first comer, and that subsequently the European Hare
invaded these countries. It probably found Ireland then no longer
accessible, having since become separated from England. Again and again
do we find the statement repeated, that the presence of the Arctic Hare
in Europe is a clear proof of the former prevalence in our continent of
an Arctic climate. But if so, why should this Hare at present live and
thrive in Ireland, which has a particularly mild climate in winter, and
be absent from so many continental stations where the temperature more
resembles that of its native home? If we suppose that the European Hare
migrated to Europe from the east, after the Arctic Hare had become
established in Western Europe, and drove the latter into the mountains
or northward whenever the two came into contact, we should have, it
seems to me, a better explanation of the range presented by the two
species. I was formerly of opinion that the European Hare had come with
the Siberian animals from Siberia, but it appears to me more likely now,
that it reached our continent with the Oriental migrants, and only then
joined the Siberians in Eastern Europe.

The evidence in favour of a former land-connection between Scandinavia
and Greenland, rests on many other facts besides those already brought
forward. That some form of land-connection formerly existed between
Europe and Greenland is now indeed almost universally accepted. That it
was situated more to the south between Scotland and Greenland is a
supposition which has been actively supported by many leading
authorities, but it seems to me that if such a land-bridge existed, it
must have been in very early Tertiary times, whilst the northern one,
such as I have indicated, may have originated later and persisted until
a recent geological date.

The distribution of few groups of animals is now better known than that
of the larger butterflies and moths (_Macro-lepidoptera_); even those
of Siberia have been fairly well investigated. The interesting facts
obtainable from their distribution are therefore of special value. No
less than 243 species of _Lepidoptera_ are mentioned by Möschler as
being common to North America and Europe. It is extremely probable that
a fair number of these have either migrated direct from America to
Europe or _vice versâ_, though many may be of Asiatic origin, and have
wandered east and west from their original home. The following twelve
species are mentioned by Petersen (p. 38) as occurring in Arctic Europe
and also in Arctic North America, but not in Asia:--_Colias nastes_,
_Colias hecla_, _Syrichthus centaureæ_, _Pachnobia carnea_, _Plusia
parilis_, _Anarta Richardsoni_, _Anarta Schönherri_, _Anarta lapponica_,
_Anarta Zetterstedti_, _Cidaria frigidaria_, _Cidaria polata_,
_Eupithecia hyperboreata_; and these, as he remarks, point to the
possibility of a former direct land-connection between Europe and North
America.

Mr. Petersen believes that the chief immigration into the Arctic area of
Europe is post-glacial and took place from Siberia, since the majority
of the species are still to be found in that country at the present day
(p. 57). He also draws particular attention to a fact,--which I shall
discuss more fully in the next chapter,--namely, that the most
characteristically Arctic forms of Northern Europe, which also partly
occur in the Alps, are entirely absent from the Caucasus.

Adopting the glacial views of some of our leading geologists, Petersen
comes to the logical conclusion that Central Europe could not have
possessed any butterflies during the height of the Glacial period, but
since all evidences seem to point to the chief migration from Siberia
having taken place after the Glacial period, he concludes that they must
have survived the severe cold of that time in Central Asia. He leaves
us, however, to imagine under what possible geographical conditions the
climate in Europe could be too severe for a lepidopterous fauna, while
at the same time Central Asia could maintain an abundant one.

In a suggestive note on the origin of European and North American Ants,
Professor Emery states (p. 399) that a great number of North American
ants are specifically identical with European ones; whilst Dr. Hamilton
tells us (p. 89), as an instance, that specimens of the beetle _Loricera
cœrulescens_ from Lake Superior and from Scotland do not seem to vary
to the extent of a hair on the antennæ. He enumerates 487 species of
_Coleoptera_ as being common to North America, Northern Asia, and
Europe, many of which no doubt have migrated by the Americo-European
land-connection.

Arctic Scandinavia or Lapland, according to Sir Joseph Hooker, contains
three-fourths of the entire number of species of plants known from the
whole circumpolar area. His view, that the Greenland flora is almost
exclusively Lapponian,--having only an extremely slight admixture of
American or Asiatic types,--again points to a former more intimate
connection between North America and Arctic Europe, and indeed he
remarks (p. 252), "It is inconceivable to me that so many Scandinavian
plants should, under existing conditions of sea, land, and temperature,
have not only found their way to Greenland by migration across the
Atlantic, but should have stopped short on its western coast and not
crossed to America."

Hooker's view, that the Scandinavian flora is of great antiquity, that,
at the advent of the Glacial period, it was everywhere driven
southwards, and that during the succeeding warm epoch the surviving
species returned north, has been adopted by the great majority of
naturalists.

The natural corollary of this theory is that there must have been,
between the beginning of the Glacial period and the present time, either
two independent land-connections between the Polar Regions and Northern
Europe at different epochs to enable animals and plants to travel
southwards and once more to regain their former northern home, or, that
during the whole of the Glacial period the Polar Regions were
uninterruptedly connected with Northern Europe, until the fauna and
flora had once more reached their northern goal, after the Polar lands
had been desolated by the supposed rigours of that period.

In following the history of the Arctic migration to Europe, it is of
great importance to determine the nature and the time of duration of
these land-connections. The Greenland flora is a very instructive one in
helping us to understand many of the problems connected with the origin
of the European plants and animals. To judge from the remarks of
Professor James Geikie and Mr. Clement Reid, no flowering plants could
have existed in the British Islands during the height of the Glacial
period, and one would suppose that the cold in Greenland at that time
must have been far more intense than in England. If no flowering plants
could exist in the latter country, then very surely none could in
Greenland, where the climate was of necessity by far more rigorous. It
will be a surprise, therefore, to those who are acquainted only with
Professor Geikie's views of the nature of the Glacial period, that two
of the most eminent Swedish botanists, who have made a special study of
the flora of Greenland, have come to the conclusion that a survival of
flowering plants has taken place in Greenland itself from pre-glacial
times. According to Professor Nathorst (p. 200), only a few plants could
have survived the Glacial period in Greenland. The species now peculiar
to that country may perhaps, he thinks, be the remnants of those which
existed in pre-glacial times. Mr. Warming, on the other hand, is of
opinion that the main mass of Greenland's present flora survived the
Glacial period there (p. 403), and that the remainder was carried from
Europe and North America by occasional means of distribution of the
nature indicated by Darwin.

Very similar views on the origin of the present Polar flora are
expressed by Colonel Feilden, who says, "To my mind it seems
indisputable that several plants now confined to the Polar area must
have originated there and have outlived the period of greatest
ice-development in that region" (_b_, p. 50). No land-connection at all
need be supposed to have existed in recent geological times, that is to
say, during the Glacial period or after, if Mr. Warming's and Colonel
Feilden's views be adopted. A pre-glacial connection would be sufficient
to explain the general features of distribution. An admission is thus
obtained from these two independent authorities that the climate during
the Glacial period must have been vastly less severe in the Polar
Regions than is generally conceded. I am of opinion that not only the
whole of the present flora, but also the fauna of Greenland survived the
Glacial period in that country.

If we suppose that an extensive centre of origin existed in the Polar
area, or we may say in Greenland, both animals and plants would have
been able to spread from it into Northern Europe and North America by
means of the land-connections which are generally supposed to have
existed in pliocene times, that is to say, just before the commencement
of the Glacial period. There must have been at this time a connection
too between Scotland and Scandinavia, which will be dealt with more
fully presently. The important point is to consider what light the
Greenland flora and fauna will throw upon the problem of the continuity
of the aforesaid land-connection during the Glacial period. We have seen
that the Barren-ground Reindeer, a typically Polar species, penetrated
as far south as the Pyrenees, the Arctic Hare went as far, while a
number of other species of Polar animals and also of plants occur in the
Alps. Of these it remains to be seen how many have come direct by way of
Northern Europe or from the Polar Regions by way of Asia. At any rate,
as the origin of the Alpine animals and plants will be discussed in
another chapter, there is no need to dwell on this subject at present.

From the nature of the distribution in Ireland of Arctic plants and
animals, which occur mostly on the north and west coasts, it would seem
that a stream of migration entered from Scotland, and I have no doubt
that that same migration came into Scotland directly from Scandinavia by
a route over which now roll the waves of the North Sea. There is,
moreover, as I already mentioned on p. 94, a very interesting so-called
American element in the north-western European flora, that is to say,
plants now found in North-west Europe and North America without
occurring in Greenland or any of the islands which might have formed the
former highway between the Old World and the New. These are probably
some of the more ancient Polar plants which have become extinct in the
Arctic Regions and survive in isolated patches in favourable localities.
We find seven species of these American plants in Ireland, almost
entirely confined to the north and west coasts. These are _Spiranthes
Romanzoviana_, _Sisyrinchium anceps_, _Naias flexilis_, _Eriocaulon
septangulare_, _Juncus tenuis_, and _Polygonum sagittifolium_. To them
must be added another plant recently discovered by the Rev. Mr. Marshall
in the south of Ireland, namely _Sisyrinchium californicum_. As I have
mentioned in former writings, there are three species of North American
freshwater-sponges in Ireland which have not hitherto been discovered
elsewhere in Europe or in Asia. These, namely _Ephydatia crateriformis_,
_Heteromeyenia Ryderi_, and _Tubella pennsylvanica_, all occur in some
of the lakes near the western coast of Ireland.

There are in all groups of animals instances of species which are
confined to Europe and North America, while unknown from the Asiatic
continent, but none, as far as is known, have such a very discontinuous
range as that of the animals and plants just referred to. In some cases
the species still occur in Greenland, and in this way make it still
clearer that their migration in former times took place from one
continent to the other by way of that country. As an interesting
instance of such distribution may be mentioned the Common Stickleback
(_Gasterosteus aculeatus_), which is found in Greenland, North America,
and Europe, but is quite absent from Asia. Then again, the Nine-spined
Stickleback (_Gasterosteus pungitius_) is confined to Western Europe
and North America, though an allied species, _Gasterosteus sinensis_,
lives in China and has probably penetrated there from the New World
across the old Behring Straits land-connection.

The Coleoptera _Diachila arctica_, _Elaphrus lapponicus_, and _Blethisa
multipunctata_ are good instances of species which have come to us from
North America by way of Greenland. I have already referred to the
Lepidoptera, but might add that eleven species of _Anarta_ occur in
Scandinavia, eight of which reappear again in Labrador, none of them,
however, being met with in Siberia. Then again, take the interesting
Crustacean _Lepidurus (Apus) glacialis_. It is found in Greenland,
Spitsbergen, Lapland, and Norway; and formerly, as we know from fossil
evidence, it ranged into Scotland. Another Phyllopod, viz.,
_Branchinecta paludosa_, inhabits Greenland, Lapland, and Norway. Mr.
Kennard suggests that the freshwater Snail _Planorbis glaber_ might also
belong to the same migration. And there are no doubt large numbers of
others.

Professor Emery mentions that Northern Europe possesses one peculiar
genus of Ant, viz., _Anergates_. This is closely allied to _Epoccus_,
another genus confined to North America. It seems probable, therefore,
that both of these have sprung from an Arctic genus which sent two
branches southward into the two continents without there being any
migration through Asia.

The general range of the Arctic plants and animals gives no reason to
suppose that the Greenland fauna and flora of the present day were
exterminated by the Glacial period and then reintroduced into that
country. Nor have we any evidence that such a fauna and flora migrated
across the British Islands northward. The Greenland animals and plants
too are altogether much more like the Lapland ones than those of
Scotland. It will also become evident to the reader of this work that no
very extensive migrations could have taken place during the post-glacial
period, and that almost everything points to a survival of both fauna
and flora in northern latitudes throughout the Glacial period.

If we take into consideration the palæontological evidence of the two
races of Reindeer in Europe, one of which came to us from the north, and
that the Arctic Hare and one of the races of the Stoat entered our
continent from the same direction--when we, moreover, carefully review
the numerous other instances quoted of plants and animals which could
only have reached us from the north, the irresistible conclusion is
forced upon us that a land-connection existed at no very distant period
between Northern Europe and the Arctic Regions of North America. This is
not a new hypothesis. Many geologists are of opinion that a land-passage
did exist within comparatively recent times, uniting Europe, Greenland,
and North America. But the position of this old land-bridge, as I have
mentioned, has been generally placed somewhat farther south than I
should feel inclined to put it.

The fact that very extensive glaciers formerly covered the mountains of
Scandinavia on the eastern side, whilst they scarcely reached the sea on
the west (Feilden, _a_, p. 721), seems to favour the view of a warm
current having washed the western shores. As I shall attempt to show
later on (p. 179), the Arctic Ocean extended across Northern Russia at
that time from the White Sea to the Baltic--that is to say, to the
eastern shores of Scandinavia, which country was then joined to the
north of Scotland. The predisposing agents to a copious snowfall existed
in Scandinavia, viz., an excessive evaporation of the warm Atlantic
waters and unusual precipitation in the form of snow owing to the cold
given off by the Arctic waters on the east side of the mountains. It is
therefore probable that the land-connection which united Europe and
North America was farther north than has been supposed.

If we sail straight across from Northern Scandinavia to Greenland, we
traverse an exceedingly deep marine basin; but if we examine the
sub-marine bank which runs all along the coast of the former country
from south to north, we find that it does not end when the extreme north
of the land is reached. The bank extends much farther north, and is
continued as far as Spitsbergen. As I have said before, the latter, as
well as Bear Island, must be looked upon as the remains of a large mass
of sunken land--the ancient Scandinavia stretching far into the Arctic
Circle. Professor Nathorst speaks of Spitsbergen as a northern
continuation of Europe, not only geographically, but also botanically
and geologically. However, this northern land must have stretched even
farther--not perhaps farther north, but farther west. Here lay the old
land-connection between Scandinavia, Greenland, and North America (Fig.
13). One of the highest authorities on the geographical distribution of
plants, Professor Engler, maintains that the arguments in favour of this
Arctic connection of America with Europe are more weighty than those for
a land-bridge between Greenland, Iceland, the Faroes, and Great Britain.
Moreover, he is of opinion that a certain number of species of plants
belonging to the Alpine flora of Arctic Siberia have travelled from
Scandinavia _viâ_ Greenland and North America to Eastern Asia, and not
direct from Scandinavia to Siberia (p. 143).

[Illustration: Fig. 13.--Map of Europe, indicating approximately the
distribution of land and water during the earlier stages of the Glacial
period--shortly after the period represented in Fig. 12, p. 156. The
darkly shaded parts indicate the areas covered by water, and the white
portions what was land at the time.]

That this ancient Arctic land-connection existed almost throughout the
Glacial period appears to me probable. It has often been suggested that
such a land-barrier was one of the principal causes of the production of
the glacial phenomena in Europe, and as such it must have existed intact
certainly during the earlier stages of the Glacial period. The barrier
must then have gradually subsided in one or two places; and once a
breach was formed, the complete union between the Atlantic and the
Arctic Oceans could not have been long delayed.

The terrestrial fauna and flora, as we have seen, lend strong support to
the view of the former connection between Scandinavia and Greenland, but
many other facts point in the same direction. It was Edward Forbes who
first drew attention to the presence of a number of species of littoral
molluscs on the coast of Finmark which also occur on the coast of
Greenland, and he expressed the firm conviction that they indicated by
their existence on both sides of the Atlantic some ancient continuity of
the coast-line. He held that the line of migration of these mollusca was
probably from west to east, and that it must have taken place during
physical conditions entirely different from those prevailing at present.
If Forbes's view is correct, a current must have existed from the north
coast of North America along the northern shore of the ancient land
which stretched east as far as Europe. We have also some palæontological
evidence bearing on the existence of such a current (p. 173).

As we shall learn presently, the early stages of the Glacial period were
accompanied by a marine transgression over Northern Russia and
Germany--an overflow, as it were, of the waters of the Arctic Ocean
covering a great part of Northern Europe, with the exception of Norway.
One continuous ocean ultimately extended from the east coast of England
across Holland, Northern Germany, and Russia to the White Sea (Fig. 12,
p. 156). The south of England being at that time joined to France, and
Scotland to Scandinavia, there was no direct communication between this
large North European Sea and the Atlantic. The glaciers which took their
origin in the Scandinavian Mountains discharged icebergs into this sea,
and many of them no doubt were stranded on the east coast of England.
The boulders of Scandinavian origin which have been discovered in recent
geological deposits on that coast have generally been traced to the
action of land-ice, but the supposition that they have been carried by
icebergs--the older theory--appears to me the more probable one. Such
boulders begin to make their first appearance in the Red Crag, a deposit
which is now looked upon as belonging to the newer pliocene series. But
whether we call it pliocene or pleistocene really matters little. The
important fact is, that glacial phenomena, consisting of the appearance
of boulders foreign to the country together with an invasion of Arctic
shells, are now ushered in upon a coast which shortly before teemed with
the southern life of a Mediterranean character. Among the new arrivals
in these English crags there are no less than eighteen species of North
American marine mollusca. Since the German Ocean had then no direct
communication with the Atlantic, these mollusca could only have come
from the White Sea, and Forbes's _Arctic current_ would offer an
explanation of the manner in which they were enabled to migrate there
from their original home.

It might be urged that we have no grounds for the supposition that the
German Ocean was practically a closed basin; and that these American
species probably inhabited at that time the whole of the North Atlantic
Ocean. But if such had been the case, we ought to have evidence of the
occurrence of some of these species in the newer Tertiary deposits along
the west coasts of the British Islands. Such beds exist; there is,
however, not a trace in any of them of any American mollusca. In
examining the marine deposits of St. Erth, on the coast of Cornwall,
which are believed to be of about the same age as the newer crags,
Messrs. Kendall and Bell were much struck by the absence of the species
characteristic of the latter. The St. Erth fauna led them to believe
that the Arctic Ocean could not then have opened into the Atlantic, but
that a land-communication had existed between Europe and North America,
so as to form a barrier of separation between the two oceans. This again
perfectly harmonises with the views I have expressed, and supports them.

Let us now look a little more closely at the history and the fauna of
the Baltic and the adjoining lakes, in order to gain additional
information as to the geographical changes which have had such lasting
influence on the peninsula of Scandinavia. The Baltic is a shallow sea
covering an area of 184,496 square miles, and its waters are decidedly
brackish. The fauna is a poor one, being too salt for the purely
freshwater species and not salt enough for the typical marine forms. The
absence of some animals which we should expect to find there is one of
the remarkable features about the Baltic, but, on the other hand, some
species occur which are altogether strangers to the fauna. And these,
moreover, are confined to the extreme northern end of the sea. I need
only refer to the Arctic Seal (_Phoca annelata_), which is confined to
the Gulf of Bothnia, and to the four-horned sting-fish (_Cottus
quadricornis_, Fig. 14, p. 178), neither of which occur on the west
coast of Scandinavia. But there are others which point in an equally
unmistakable manner to the former existence of a marine connection
between the Baltic and the southward prolongation of the Arctic
Ocean--known as the White Sea. It is generally admitted now that such a
union between these two seas, viz., the Baltic and the White Sea,
occurred in recent geological times, but opinions differ as to the
duration of this connection. I adhere to the view expressed by Murchison
and others, that the boulder-clay is a marine deposit. I am also
convinced that the Arctic Ocean, as I have already mentioned,
transgressed over the lowlands of Northern Russia at about the time when
the newer crags were being deposited on the east coast of England; that
the same large sea also covered Northern Germany, Denmark, Holland, and
the lowlands of Sweden, and laid down the lower continental boulder-clay
which is spread over such vast tracts of land in those countries. I
shall have occasion to refer to this again more fully in the next
chapter; meanwhile, it should be remembered that this stage was followed
by a partial retreat of the northern sea, though Scandinavia did not
become joined to the Continent. The date of this retreat of the sea,
represented in Fig. 13, corresponds probably to what is known as the
inter-glacial phase of the Glacial period, and I think it must have been
during this time that the Forest-Bed on the coast of Norfolk was laid
down.[2]

None of the Siberian mammals apparently entered Scandinavia at the time
when they invaded Central Europe and penetrated as far west as England
and Western France. Nor did the great Oriental mammals, like the Mammoth
and others, reach Scandinavia; and Professor Pohlig argued, on the
strength of these facts, that the latter country was either for a very
short time only free from ice, or that it had defective
land-communication with the Continent during inter-glacial times. This
seems to me scarcely to explain the facts of distribution and account
satisfactorily for the absentees. Nor does it, of course, harmonise with
the views that I have announced above. Professor Engler's remark (p.
131), that Scandinavia probably projected above the glacial sea as an
island, is more in accordance with these views, though the term island
is scarcely applicable to that country, since it was always, as I said,
indirectly joined to the Continent (_vide_ Fig. 13, p. 170). The fauna
of Scandinavia, both fossil and recent, points to a direct isolation of
that country from the continent of Europe during a considerable period.

Another proof that Northern Russia and the lowlands of Sweden were
covered by the sea comes to us from a study of the fauna of the relict
lakes--the "Reliktenseen" of Leuckart. This name was first applied by
Leuckart to lakes containing marine organisms, which are supposed to
have been flooded by, or to have been in close communication with the
sea at some former period, like the lakes Ladoga and Onega in Russia.
His views have been worked out subsequently in greater detail by Lovén
and O. Peschel, who gave them their strong adherence. Many leading
zoologists, such as Professor Sars and others, have since adopted them,
and though discredited by Professor Credner, the theory still offers the
best explanation for the origin of marine animals in freshwater lakes.

Professor Credner's contention, that marine mollusca are always absent
from these relict lakes, seems at first sight a stumbling-block to the
theory. But the explanation is really simple enough. It is to Dr. Sollas
that we owe a very ingenious explanation of the origin of freshwater
faunas. He showed that all freshwater organisms in their early stages of
development are provided either with some process enabling them to
attach themselves to a foreign object, or that they pass this period
within the body of the parent. This is a provision of nature to prevent
freshwater organisms from being floated out to sea, where they would
perish, until they reach maturity and can cope with floods and currents.
Had Professor Credner been aware of Dr. Sollas's views, no doubt he
would have modified his criticisms, for, as most marine mollusca have
free-swimming larvæ, they would have little chance of becoming permanent
residents of lakes. During their larval stage, marine molluscs are quite
a prey to the currents of the sea. They have practically no swimming
organs, and only move by lashing to and fro the tender cilia with which
they are provided.

[Illustration: Fig. 14--The Four-horned Sting-fish (_Cottus
quadricornis_), reduced from Professor Smitt's figure in the _Fishes of
Scandinavia_.]

This disposes, therefore, of Professor Credner's main criticisms. As for
the fauna of the relict lakes, we are now only concerned with those of
Northern Russia, Finland, and Sweden. In the lakes Wetter and Wener in
the latter country occurs the four-horned sting-fish (_Cottus
quadricornis_, Fig. 14), which, as we have learned, also inhabits the
northern part of the Baltic, and, as was suggested, migrated there at a
time when the latter was connected with the White Sea. The principal
food of this little fish consists in a marine Crustacean called _Idotea
entomon_, an animal allied to our common woodlouse. This is a typical
marine species, but it occurs also in the relict lakes of the countries
mentioned above, as well as in the Baltic and the Caspian. Perhaps the
best known form with a similar range is the Schizopod crustacean _Mysis
relicta_[3] (Fig. 15), which is clearly a descendant of the Arctic
marine _Mysis oculata_, of which it was formerly considered a mere
variety. The two Amphipods _Gammaracanthus relictus_ and _Pontoporeia
affinis_ and the Copepod _Limnocalanus macrurus_, are three additional
well-known Arctic crustaceans whose range differs but little from those
above-mentioned.[4]

[Illustration: Fig. 15--Mysis relicta, a small shrimp-like Crustacean,
after Sars (enlarged).]

These facts all go to prove that the sea formerly covered the lowlands
of Sweden, Finland, and Northern Russia. The fauna of Scandinavia, as we
have seen, indicates that during the greater part of the Glacial period
the country was not directly connected with continental Europe as it is
now. It seems that the barrier of separation probably consisted of a
broad expanse of ocean on which floated numerous icebergs, which
originated from the Scandinavian glaciers as they reached the sea. This
was a cold sea, whilst Western Scandinavia was washed by the Gulf Stream
(_vide_ Fig. 12, p. 156). We might look upon the boulder-clay which
covers such vast tracts of country in Northern Germany, Russia, and
Holland as deposits formed by this sea rather than the ground-moraine of
a huge Scandinavian glacier. I shall refer to this subject again in the
next chapter; meanwhile it may be remembered that the boulder-clay of
Northern Europe exactly resembles in all important particulars the
similar accumulations met with in the British Islands. They resemble one
another also in the occasional occurrence of sea-shells, the frequent
appearance of bedded deposits, and the often inexplicable course taken
by boulders from their source of origin. There occurs often a singular
mixture and an apparent crossing of the paths of boulders in the
boulder-clay. Professor Bonney remarks (p. 280) that these are less
difficult to explain on the hypothesis of distribution by floating ice
than on that of transport by land-ice, because, in the former case,
though the drift of winds and currents would be generally in one
direction, both might be varied at particular seasons. So far as
concerns the distribution and thickness of the glacial deposits, he says
there is not much to choose between either hypothesis; but on that of
land-ice it is extremely difficult to explain the intercalation of
perfectly stratified sands and gravels and of boulder-clay, as well as
the not infrequent signs of bedding in the latter. Two divisions are
generally recognisable in the continental boulder-clay--a lower and an
upper. An inter-glacial phase characterised by a less severe climate is
assumed to have intervened between the deposition of the two. In Russia
no such division can as a rule be made out, and sea-shells are either
entirely absent or extremely scarce. It has been pointed out by
Professor J. Geikie that the erratics--a name applied to boulders in
boulder-clay--in the upper division have travelled in a different
direction from those contained in the lower. Taking for granted that the
boulder-clay is a marine deposit, this phenomenon seems to indicate that
the current which prevailed during the early part of the Glacial period
in this North European ocean was different from the prevailing current
during the latter part. I have attempted to explain this circumstance by
the supposition that during the early part of the Glacial period the
Northern Sea had a connection with the Ponto-Caspian Sea--a sea formed
by the junction of the Black Sea and the Caspian (Fig. 12, p. 156).
There is geological evidence, as will be explained in the following
chapter, that the area of these two seas was considerably larger in
glacial times than it is now, and that they were joined across the
valley of the Manytch. After the inter-glacial phase of the Glacial
period, the North European Ocean became connected with the Atlantic
Ocean across the north of England (Fig. 6, p. 126), the junction between
the former and the Ponto-Caspian having meanwhile become dry land (Fig.
13, p. 170). A fresh current, now flowing westward, was set up in the
North European Ocean, which accounts for the fact just cited that the
erratics in the upper continental boulder-clay have travelled in a
different direction from those in the lower. The boulder-clay laid down
by the sea on the midland and northern counties of England, just as was
the case with the similar deposit on the Continent, is generally
accredited to the action of land-ice. It is by most geologists looked
upon as the ground-moraine, partly of the huge Scandinavian glacier
which is supposed to have impinged upon the English coast, partly of
local British glaciers.

But renewed geological investigations on this point throw doubts upon
these theories. Thus Mr. Harmer remarks in a recent contribution to
glacial literature (p. 775), that "it is difficult to see how the Baltic
glacier could have reached East Anglia, though ice-floes with
Scandinavian boulders might easily have done so, while had the Norwegian
ice filled the North Sea and overflowed the county of Norfolk, some
evidence of its presence ought to be found in the glacial beds of
Holland."

All the phenomena of distribution of the British fauna and flora are, as
we have seen, much more easily explained by the supposition of a damp,
temperate climate, such as might have been produced by the proximity of
a cold sea on one side and of a warm one at the other, than by invoking
an arctic climate with enormous glaciers. Most of the living animals and
plants would have been exterminated under the latter conditions.
Palæontological evidence in Great Britain clearly indicates that
southern species migrated first to these islands, that Arctic species
were then driven south from their native lands,--probably owing
insufficient food-supply and climatic changes in the north,--that
finally eastern species invaded the country--all this without the annual
temperature of Europe being apparently much affected. For we find in the
British pleistocene deposits--and Mr. Lydekker draws particular
attention to this remarkable fact--a curious intermingling of southern
and northern mammals, which undoubtedly lived side by side. Everybody
knows that northern and Arctic species can live perfectly well in a
temperate climate, but that it is almost impossible to acclimatise
southern animals in an Arctic or even temperate one. We have in this
circumstance almost a proof, therefore, that the climate cannot have
been very cold. Though a cold sea bathed the shores of Eastern England,
and even eventually invaded a portion of Northern England, the warm
ocean on the west must have effectually prevented any great lowering of
temperature.

At the time when the North European Sea flooded a portion of England,
Scandinavia was still connected with Scotland, and the latter with
Ireland (Fig. 6, p. 126). There is no doubt that the food-supply in the
Arctic Regions was decreasing with an increase of snowfall and with the
gradual lowering of the land, which reduced also the habitable area.
Arctic species therefore were driven south in search of fresh pastures.
But it need not be supposed that anything like a vast destruction of the
fauna of the Arctic Regions took place. Only fewer mammals were able to
find food in a given space than heretofore. This southward migration may
have commenced, in the case of plants and the invertebrates, at a much
earlier time,--during the Miocene or Pliocene Epochs,--but it is
doubtful whether the mammals and birds which we find in our pleistocene
and recent deposits began to travel south much before the commencement
of the Glacial period. The beginning of the Glacial period in England, I
think, is indicated by the deposition of the Red Crag, though the latter
is generally regarded as belonging to the pliocene series. Much of the
northward migration from the British Islands of Lusitanian and other
forms had then ceased, but we have in Scandinavia, just as in these
islands, a southern relict fauna and flora, plants and animals which had
wandered across what is now the German Ocean from Scotland to
Scandinavia, and have never become extinct in that country to the
present day. I need only mention the Red Deer, the Badger, and Slugs of
the genus _Arion_.

Professor Blytt directs attention to some such southern relict species
of plants now only found in the extreme south-west of Scandinavia, such
as _Asplenium marinum_, _Hymenophyllum Wilsoni_, _Carex binervis_,
_Scilla verna_, _Erica cinerea_, _Conopodium denudatum_, _Meum
athamanticum_, and _Rosa involuta_ (p. 28).

The Arctic fauna and flora in Scandinavia--that is to say, the
descendants of those species which migrated direct from Greenland and
Spitsbergen, as we have seen, are numerous. They of course persisted
throughout the Glacial period in the country, and are now in many
localities being exterminated partly by change of climate, partly by a
keen competition with more vigorous rivals which have come to
Scandinavia from the east. It is a curious circumstance, as pointed out
by Professor Blytt, that the Arctic plants in the Botanic Gardens at
Christiania are able to stand almost any amount of sunshine, but are
very liable to be injured by the frost, and have to be covered in the
winter. A similar observation has been made in the case of the Alpine
plants at Kew Gardens, which have to be wintered in frames, though their
homes are either in the high Alps--among the everlasting snows--or in
the intensely cold climate of Greenland. Many of the Scandinavian plants
exhibit instances of discontinuous distribution, thus showing their
ancient origin; and there is altogether nothing in the fauna and flora
of that country which might lead us to believe that these were
exterminated during the Glacial period and reintroduced subsequently.
The climate during that period in Scandinavia was probably more equable
and moister,--with a greater snowfall in winter and with less sun to
melt the snow during summer,--so that the development of glaciers took
more formidable dimensions, chiefly on the east side. The lowlands of
Sweden were covered by the sea, whilst many of the valleys were choked
with great glaciers, which cast off portions of ice as they reached the
sea, just as the Greenland and other northern glaciers do (_vide_ p.
237). A country which at the present day probably somewhat resembles the
former Scandinavia climatically is Tierra del Fuego, in the extreme
south of South America. Though there is an abundant snowfall, so that
glaciers reach the sea in many parts of the country, the flora has been
described by travellers as luxuriant; and it appears that the fauna also
is richer than might be expected from the cheerless climate.

Towards the latter part of the Glacial period the land-connection
between Scandinavia, Spitsbergen, and Greenland broke down, and the
waters of the Arctic and Atlantic Oceans joined. Whether it was at this
time or later that the other land-connection between Scandinavia and
Scotland collapsed is difficult to determine; but it is certain, I
think, that Scotland was still united with Ireland even after these two
great land-bridges ceased to exist.


SUMMARY OF CHAPTER IV.

The fauna of the Arctic Regions is much poorer than that of the other
regions which are dealt with in this work. In some groups, such as
Reptiles and Amphibia, there are no representatives at all, but no doubt
a larger number of species existed there in earlier Tertiary times. At
least we have fossil evidence that during the Miocene Epoch plants of
many families flourished in Greenland of which no vestige is now left in
the Polar area. Climatic conditions must therefore have changed, as in
Europe. A gradual refrigeration took place, owing probably to the slow
withdrawal of the current which supplied the Arctic Sea with warmth.
Greenland and Europe were then connected, and the Arctic Ocean was
separated from the Atlantic. This land-connection is supposed to have
lain far north between Scandinavia, Spitsbergen, and Greenland, and must
have persisted until towards the end of the Glacial period.

As the temperature decreased and the land-area available in the north
diminished, the surplus population, consisting of animals and plants,
and possibly also of human beings, moved southward. We have traces in
Europe, and especially in the British Islands, of a very early migration
from the north in the so-called American plants and in the freshwater
sponges. The geographical distribution of some of the Arctic species of
mammals is referred to in greater detail, to show how the relative age
of their entry into Europe can be determined. Two forms of Reindeer,
resembling the Barren-ground and Woodland varieties, have been met with
in European deposits, but only the former occurs in Ireland and the
south of France, whilst eastward the other becomes more common, and
finally is the only one found. It is believed that the Barren-ground is
the older form as far as Europe is concerned, and that it came to us
with the Arctic migration, and that the other Reindeer reached Europe
much later from Siberia, when Ireland had already become detached from
England. The range of the Arctic Hare is equally instructive. It must
have been a native of Europe since early glacial or pre-glacial
times--before the common English Hare had made its appearance in Central
Europe. Along with other Arctic forms, it entered Northern Europe
directly from the Arctic Regions, by means of the former land-connection
which joined, as I remarked, Lapland with Spitsbergen, Greenland, and
North America. There need not have been a post-glacial connection
between Europe and Greenland; the present flora of that country may have
survived the Glacial period in the Arctic Regions, as has been
maintained by some botanists and other authorities. Professor Forbes
argued from the occurrence of the same species of shore mollusca on the
coast of Finmark and Greenland that these two countries were not long
ago joined, so that a slow migration from west to east along an ancient
coast-line could have taken place. That such a migration actually
occurred is further made probable, judging from the presence of American
mollusca in the Crag deposits on the east coast of England. These came
into the North Sea in the first place direct from the Arctic Ocean at a
time when the two oceans freely communicated with one another across the
lowlands of Northern Russia, Northern Germany, and Holland. Arctic
shells are also found below the boulder-clay on the Baltic coast, and a
free communication such as indicated is generally held to have taken
place at no very distant date. The so-called "relict species"--marine
animals left in freshwater lakes in districts formerly covered by this
sea--lend some support to this view. But the view that the continental
boulder-clay is a marine deposit is not now held except by a few, though
I here bring it forward again, as it seems to me to fit in so much
better with the known facts of distribution. The sea just referred to
probably existed throughout the greater part of the Glacial period; and
icebergs, which originated from the Scandinavian glaciers, would have
brought detritus and boulders to the lowlands. Scandinavia was then
connected with Scotland, and England with France.

FOOTNOTES:

[1] A very interesting piece of information has been given us, recently,
by Mr. Barrett-Hamilton on the Arctic Fox of Spitsbergen. In comparing
the skulls of Spitsbergen Foxes with those of Europe, he found that the
former are much smaller, and represent a distinct race or sub-species.
This small race he believes to be confined to Greenland, Iceland,
Spitsbergen, and Novaya Zemlya, whilst the larger one occurs in Europe,
Asia, and on the Commander Islands. This fact favours the view which I
have advocated in Chapter V., that the Arctic Fox in Europe is a
Siberian migrant, and did not come from the north with the Reindeer and
Arctic Hare.

[2] I have already expressed this view on p. 120.

[3] The occurrence of this species in Lough Neagh in Ireland, pointing
to a connection between the Irish Sea and the Baltic, will be referred
to later on; as also that of two allied forms in the Caspian Sea.

[4] For additional species with a similar range, _vide_ Nordquist.




CHAPTER V.

THE SIBERIAN MIGRATION.


In dealing with the British fauna in particular, I have drawn attention
to the fact that it is chiefly in the south of England that we find
fossil remains of eastern species of mammals in recent geological
deposits. We can actually trace the remains of these species and their
course of migration across part of the Continent towards Eastern Europe,
and as none of their bones have been discovered in the southern or
northern parts of our Continent, it must be assumed that their home lay
in Siberia, where many still exist to the present day, and where closely
allied forms also are found. Some of these Siberian migrants have
remained in England and on the Continent to the present day. Many have
become extinct. But the animals forming this eastern migration did not
all originate in Siberia, though I have sometimes spoken of them
collectively as Siberian migrants. There must have been other centres of
dispersion of species in Europe. We know that a very active centre of
development--at any rate for land-mollusca--lay in South-eastern Europe,
either in the Caucasus or in the Balkan peninsula, or more probably in
both. The Alps no doubt produced a number of species which have spread
north and south, and may in their wanderings have joined the Siberian
migrants in their western course, and thus have reached the British
Islands. Nevertheless, the majority of the mammals belonging to the
eastern element of the British fauna (_vide_ p. 95) have undoubtedly
originated in Siberia. The Polecat (_Mustela putorius_) and the Harvest
Mouse (_Mus minutus_), for instance, are members of that eastern
migration. Both occur throughout Central Europe and a large portion of
Siberia, but are absent from the extreme north and south of Europe and
also from all the Mediterranean Islands. A Siberian species, which has
never penetrated so far west as the British Islands, nor even so far
north as Scandinavia or south to Italy, is what is known in Germany as
the "Hamster" (_Cricetus frumentarius_), a little Rodent which spends
the winter asleep in its burrows, and surrounds itself with a great
accumulation of food-material carried there during autumn. The common
English Hare, which I formerly regarded as an instance of a Siberian
mammal, must now find a place among the Oriental migrants. Its history
is very instructive, and I shall have an opportunity later on to refer
to it again. Meanwhile, it may be mentioned that though this Hare
inhabits Europe in two varieties or races, one of which, _Lepus
mediterraneus_, is confined to Southern Europe, the latter owes its
origin to an earlier migration from Asia.

When we come to consider the eastern birds, we have to distinguish
between resident species and migratory ones. The Black-throated Thrush
(_Turdus atrigularis_), which has been twice obtained in the British
Islands, is a mere straggler to Europe, and is not known to breed there
at all. Better known birds, perhaps, are the Golden Thrush (_Turdus
varius_), which has even occurred as far west as Ireland, the
Rock-Thrush (_Monticola saxatilis_) and the Scarlet Grosbeak
(_Carpodacus erythrinus_), which breed in Eastern Europe, but are known
only as occasional visitors in the west.

To judge by their distribution, the Bullfinches (_Pyrrhula_) are of
Asiatic origin, for seven species out of ten are confined to that
continent. Our common Bullfinch (_P. europæa_) probably came with the
Oriental migrants, or perhaps its ancestors did. But the larger Northern
or Russian Bullfinch (_P. major_) has no doubt entered our Continent
directly from the east. We have in many groups similar instances of
closely allied species or varieties, one of which, originating at a
somewhat later stage than the other, took a different route of migration
from that followed by its near relative.

The Pine-Grosbeak (_Pinicola enucleator_) is only known to British
ornithologists as an exceedingly rare visitor. Its real home lies in the
northern parts of Europe, Asia, and North America, and it is one of the
most typical of the Siberian migrants.

But there are a number of other species of birds, which, though probably
not of Siberian origin, only migrated westward recently, and have
either not yet reached the British Islands, or which lead one to
suppose, from their British range, that they are eastern forms.

Such, for instance, is the Nightingale (_Daulias luscinia_), which is
probably of Oriental origin, but only visits England regularly in
spring. There is no authenticated record of its ever having migrated
either to Scotland or Ireland.

The Bearded Titmouse (_Panurus biarmicus_) is one of the eastern birds
still resident in England, though unfortunately it seems to be on the
verge of extinction. It is unknown in Scotland and Ireland. Another
resident eastern species is the Nuthatch (_Sitta cæsia_), but neither of
these is probably of Siberian origin.

The majority of the European Reptiles are probably of eastern origin.
Among our British species, the Common Viper (_Pelias berus_), for
example, is a typically eastern form. It is almost unknown in Southern
Europe proper--that is to say, in Italy, the Balkan peninsula, and the
Mediterranean Islands, but its range extends in the west as far as
Spain, and in the east right across the Asiatic continent to Japan. It
is well known that the Viper occurs in Scotland, and that neither it nor
any other snake is found in Ireland. There is a legend, indeed, that
snakes did once exist in Ireland and were banished from the island by
St. Patrick, but unfortunately we have no historical evidence that such
an interesting event actually took place. The Sand-Lizard (_Lacerta
agilis_), another British species, may be looked upon as an eastern
form. It is quite absent from Italy, the Balkan peninsula, and the
Mediterranean Islands, but extends throughout Central Europe to the
east.

Among the species of eastern Reptiles which have a mere local range in
Europe might be mentioned the two Lizards, _Phrynocephalus auritus_ and
_Agama sanguinolenta_. They belong to the family _Iguanidæ_, which
includes some very large species. Both of them are Asiatic forms, which
have only just penetrated across the eastern steppes into Europe, where
they inhabit the arid regions between the Caspian and the River Don in
Southern Russia.

The species of Mammals living in Europe at the present day have, with
few exceptions, migrated to our continent from other parts of the world.
With regard to the Birds, it is possible that a somewhat larger number
proportionally may be of European origin. Still, the great majority are,
I think, to be regarded as immigrants. The autochthones are about equal
to the immigrant reptiles, but many of the European Amphibians and the
majority of the Fishes have probably originated on our continent. Some
of the European Amphibia--especially among the tailless forms--appear to
be immigrants from Asia. Thus the distribution of _Rana arvalis_ in
Europe is remarkably like that of a Siberian migrant. This frog occurs
in Siberia, ranging southward as far as Persia and parts of Asia Minor.
Crossing the European border, we find it in Russia, Upper Hungary, North
and Central Germany,--being rarer in the south,--Denmark, and
Scandinavia. According to Bedriaga, it crosses the Rhine only in Alsace,
but occurs no farther west. It only just enters Holland. If we suppose
the species to have originated in Central Europe, we should expect to
find it in Switzerland, France, and perhaps England. If it had its
ancestral home in Eastern Europe, we might expect it to occur on the
Balkan peninsula. It seems to me more probable, therefore, that _Rana
arvalis_ came with the Siberian migration. This need not cause surprise,
as the genus _Rana_ is certainly not European. Out of about 110 species,
only four are peculiar to Europe, the rest are scattered over all parts
of the globe. Moreover, the fact that these four species are confined to
Southern Europe would seem to indicate that the first species entered
from the south, and there either became modified or spread over nearly
the whole continent, as did, for instance, _Rana esculenta_ and _R.
temporaria_. Neither of these is by any means confined to Europe. _R.
esculenta_ ranges right across the Asiatic continent to Japan, and also
enters North Africa, while the other has a wide distribution in northern
and temperate Asia.

The various groups of Vertebrates are not dependent on each other in
their migrations. Mammals and Birds extend their range with so much
greater facility than Reptiles and Amphibians, that the surplus
population of our neighbouring continents readily poured into Europe
when--owing to changes of climate perhaps--they forsook their original
homes.

We observe much the same differences of origin in the various groups of
European Invertebrates. The Central European Molluscan fauna, remarks
Dr. Kobelt, had already developed from the pliocene--in almost all its
details, as regards formation of species and distribution--when the
Ice-Age commenced (_b_, i. p. 162). Certain very interesting
dislocations, however, in the range of land mollusca can be proved to
have taken place about that time. Thus, as Dr. Kobelt has pointed out,
the genus _Zonites_, which is now almost confined to the south-east of
Europe, occurs in inter-glacial deposits in the valley of the Neckar,
and even as far west as the Seine. If we might judge from this single
instance, a molluscan migration from the east to the west seems to have
occurred either in early or pre-glacial times. That _Helix pomatia_ has
migrated only comparatively recently from the East to Western Europe is
rendered probable by its general range in northern and western Europe,
but I cannot agree with Dr. Kobelt in the belief that _Helix aspersa_ is
of an equally recent origin in the North. No matter whether it has been
found fossil or no, its range in the British Islands points to its
having penetrated to Ireland when the latter was still connected with
the Continent by way of England. Its migration from the Mediterranean
dates therefore from early pleistocene or late pliocene times.

In referring to the sixty-five species of Land and Freshwater Mollusca
which have been described from the continental "Loess," Dr. Kobelt
states (p. 166) that this fauna has certainly not a steppe-character. It
does not therefore strengthen Professor Nehring's view that Europe
during the deposition of the loess had a climate comparable to that of
the Siberian steppes. The Glacial period had hardly any effect on the
molluscan fauna of Europe. Dr. Kobelt believes in a certain movement of
that fauna from the least favourable areas, with a subsequent
re-immigration; but even that could not have taken place on a large
scale. Nothing like a destruction of the fauna occurred, as far as we
know from fossil evidence.

Not a single species of land or freshwater mollusc can be quoted as
having migrated to Europe from Siberia in recent geological times. The
molluscan fauna of the latter country is so closely connected with that
of Europe, that it is quite impossible to elevate it to the rank of a
sub-region of the Holarctic Region. Dr. Kobelt insists that Siberia
cannot even claim to be placed into a distinct province. According to
the same authority, we find no species in the whole Siberian molluscan
fauna which we might regard as having immigrated since the close of the
Glacial period. Even to attempt the location of the original homes of
many of the species which Siberia has in common with Europe, seems
hopeless. Such forms as _Arion hortensis_, which has been obtained in
Siberia, and which, as we have seen, must have originated in Western
Europe, migrated in pliocene or miocene times, possibly along the shores
of the Mediterranean and across Asia Minor. We have evidence, therefore,
of an eastward migration among the land and freshwater mollusca in later
Tertiary times, but not of a westward one from Siberia.

A very different view is presented to us by the coleopterous fauna of
Europe. Many of our European Beetles are Siberian migrants. Let us take,
for instance, the Tiger Beetles (_Cicindelidæ_). There are over forty
species of the genus _Cicindela_ in Europe, five of which reach the
British Islands. This seems a large number; but there are altogether no
less than 600 species of the genus scattered over the greater part of
the world, many of them being Asiatic. The genus is certainly not of
European origin, for not only are most of the European species confined
to the Caucasus and the south-east generally, but no _Cicindelidæ_
whatsoever occur, for example, in Madeira or the Canaries, where we
should expect some to have persisted if the genus had originated on our
continent. Moreover, of the five tribes into which the large family of
_Cicindelidæ_ can be sub-divided, only two range to Europe, and one of
them is represented by only a single species on our continent.

Some of the _Cicindelas_ may have come with the Oriental migration. I
think this was the case with the only Irish species of the genus, _C.
campestris_. It occurs all over continental Europe and Northern Asia,
and varieties of the species are known from Corsica, Sicily, Crete, the
Cyclades, Sardinia, Asia Minor, Greece, and Spain. Five species of
_Cicindela_, as I said, are known from England, of which _C. silvatica_
and _C. maritima_ are certainly Siberian migrants, and perhaps _C.
hybrida_ too. Neither of the two first species is found in Southern
Europe or in Spain, where we should expect them to occur had they
originated on our continent. _C. silvatica_ and _maritima_ have no doubt
entered Europe from Siberia in recent geological times, probably soon
after a way was opened up across the Tchornosjem district of Southern
Russia--that is to say, in inter-glacial times. The former spread along
the Central European plain as far west as the south-east of England when
Great Britain still formed part of France. _C. maritima_, which
preferred the proximity of the sea, migrated along the shores of the
Caspian and then across Russia to the shores of the Baltic and North
Sea, and has penetrated a little farther north and west in England than
its near relative. _C. litterata_ has a very similar distribution and
origin, but instead of wandering so far west as the British Islands, it
seems to have preferred extending its range southward, and has just
reached Northern Italy.

The closely allied Ground-beetles (_Carabidæ_) furnish us with equally
interesting and instructive proofs of a migration from Asia. Over 300
species of _Carabus_ are known to science. The number of species
inhabiting Asia and Europe are about equal. But the genus does not
extend its range to Southern Asia or to South America or Australia. Very
few species enter Africa, and only nine North America, of which three
also occur in Siberia. The genus is unknown in Madeira, and only
represented by three species in the Canary Islands. To judge from its
distribution, it has probably originated in Western Asia. Probably some
_Carabi_ of European origin have spread into Asia, but the Asiatic--or
we might say the Siberian--origin and subsequent migration westward of a
number of well-known forms appears to me evident. Such forms as _C.
clathratus_, _C. granulatus_, and _C. cancellatus_ are no doubt of
European origin, and have only in recent geological times extended their
range across Northern Asia, whilst _C. marginalis_, coming from Siberia,
can hardly be said to have invaded Europe, since it has never been met
with farther west than the eastern provinces of Prussia.

Among the _Carabidæ_ there are altogether very many examples pointing to
a migration from Asia to Europe, but I do not wish here to give a list
of all such cases, and only refer to a few of the more remarkable ones.
One of the European species of Demetrias (_D. unipunctatus_), known to
English entomologists as a south-eastern form, seems to have arrived
with the Siberian migration, whilst the closely allied _D.
atricapillus_, which has been able to reach Ireland, has a wider range
and came earlier with the Orientals.

Messrs. Speyer state (p. 68) that almost all those species of Central
European Butterflies whose northern limit is deflected southward as we
approach the west coast of Europe, inhabit also the Volga country and
the adjoining parts of Asia. Many of them are much commoner there than
in Central Europe, and it appears probable to the authors of the
_Geographical Distribution of Butterflies_ that these species came from
the east. Asia and Central Europe have, according to Messrs. Speyer, no
fewer than 156 species in common. Mr. Petersen estimates that no less
than 91 per cent. of the Arctic-European Butterflies also occur in
Siberia. He made a special study of the Arctic _Macro-lepidoptera_, and
came to the conclusion that Central Asia, not having been glaciated in
the Ice-Age, offered a possibility of existence to both animals and
plants. Here, he thinks, was the principal centre to which Europe owed
its re-population in post-glacial times. Mr. Petersen is of opinion (p.
40) that the Arctic-European _Lepidoptera_ are composed of two
elements--the pliocene relics which persisted in Europe during the
Glacial period, and the new immigrants from Siberia.

No doubt Siberia supplied Europe with a number of species of
Butterflies and Moths in recent geological times, but we need not
necessarily suppose that these arrived only after the Glacial period.
Even the most extreme glacialists admit that large areas on our
continent were free from ice at the height of the Ice-Age, Siberia had
therefore no particular advantage over Europe in giving an asylum to
Butterflies and Moths which were escaping from the rigours of a supposed
arctic climate. But we have already learned (p. 80) that the climate
during the Glacial period probably differed but little from that which
we enjoy at the present day, and we may assume, therefore, that the
_Lepidoptera_ of Siberia migrated during that time or even earlier to
Europe.

Let us for a moment reconsider some instances of mammalian migration
from Siberia, with a view to studying more closely the nature of these
great events. I mentioned the fact that some of the Siberian migrants
have remained in England, that more have settled down permanently on our
continent, but that many others have either become entirely extinct or
do not live any longer in Europe.

Of the mammals which made their appearance in Great Britain in recent
geological times, _i.e._, during and since the deposition of the
Forest-Bed for example, the following species probably came direct from
Siberia across the plains of Europe, as already mentioned (p. 95):--

    Canis lagopus.
    Gulo luscus.
  * Mustela erminea.
  *    "    putorius.
  *    "    vulgaris.
  * Sorex vulgaris.
    Lagomys pusillus.
  * Castor fiber.
    Spermophilus Eversmanni.
      "        erythrogenoides.
    Cricetus songarus.
    Myodes lemmus.
    Cuniculus torquatus.
  * Mus minutus.
  * Arvicola agrestis.
  *    "     amphibius.
       "     arvalis.
  *    "     glareolus.
       "     gregalis.
       "     ratticeps.
    Equus caballus.
    Saiga tartarica.
    Ovibos moschatus.
    Alces latifrons.
      "   machlis.
    Rangifer tarandus.

  * Those marked with an asterisk still inhabit Great Britain,
  or did so within historic times.

Of the arrival of many of these in Europe we have geological proof, as
they have left their bones in recent pleistocene deposits, and are
unknown from older European strata. The remote ancestors of others, such
as _Sorex_ and _Lagomys_, no doubt lived in Europe, but the recent
species probably had their original homes in Asia. It is evident that in
recent geological times there existed no active centre of origin for
mammals in Europe, and that our continent was largely dependent on the
neighbouring one for the supply of its mammalian fauna. A shifting of
the centre of development from Europe to Asia appears to have taken
place occasionally, as already mentioned (p. 45). Mr. Lydekker has drawn
attention to the fact that though the remote ancestors of the
_Elephantidæ_ resided in Europe, neither the latter continent nor North
America was the home of the direct ancestor of any of the true
Elephants. Similarly, though we have had our _Sorex_ in Europe from the
Upper Eocene and _Lagomys_ from the Middle Miocene, the geographical
distribution of _Sorex vulgaris_ and _Lagomys pusillus_ does not support
the view that they are of European origin and have migrated to Asia.
Their absence from most of the European islands indicates either an
extremely recent origin or a recent immigration from Asia, and the
latter view seems to me much the more probable.

No less than twenty-six species of the Siberian mammals penetrated as
far west as the British Islands, and nine of these still inhabit Great
Britain. Some of the remaining seventeen species probably lived only for
a very short time in England, and the rest gradually became extinct one
by one. This process of extinction of the aliens still continues. The
Beaver (_Castor fiber_) has died out within recent historic times. We
possess legends and uncertain historic records pointing to the existence
of the Reindeer in Scotland as recently as about seven centuries ago.
But much the same state of things has happened on the Continent. The
Glutton (_Gulo luscus_), which still lived in Northern Germany last
century, has now entirely vanished from that country, as also the
Reindeer. The Lemmings have found an asylum in Scandinavia. The Musk-Ox
(_Ovibos moschatus_) has disappeared not only from Europe but also from
Asia, and is now confined to Arctic America and Greenland. The Horse no
longer occurs in Europe in the wild state, and the Saiga Antelope
(_Saiga tartarica_) has retreated to the Steppes of Eastern Europe and
Western Siberia.

As we proceed more and more eastward across Central Europe, we find that
a larger and larger percentage of the Siberian migrants have adopted the
new country as their permanent home, though in France and Germany, as
well as in Austria, we have evidence that a great number of Siberian
species, which formerly lived there, have either become entirely
extinct, or have retreated towards the land of their origin. There is a
prevalent belief that these migrants have taken refuge on the higher
European mountain ranges, but this idea is altogether erroneous, as will
be shown in the chapter dealing with the origin of the Alpine fauna.

One of the Jerboas (_Alactaga jaculus_) occurs fossil as far west as
Western Germany, but it is now confined to Russia and Western Siberia.
The Bobak marmot (_Arctomys bobak_), which has a similar range now,
probably inhabited France in former times. A Siberian species which has
retreated but little is the Hamster (_Cricetus vulgaris_). Its fossil
remains have been found in Central France, but it does not now occur
west of the Vosges Mountains.

It appears, therefore, as if a wave of migration had swept over Central
Europe from east to west, that those species which were able to adapt
themselves to the new surroundings had remained, and as if the rest had
died out or were gradually retreating to the east.

Ornithologists are well acquainted with the fact that in some years
there is an unusually large exodus from Eastern Europe and Siberia of
birds; and that species like the Waxwing (_Ampelis garrulus_) then
appear in great numbers. But the appearance of this bird in Western
Europe is not looked upon as so remarkable as that of Pallas's
Sandgrouse (_Syrrhaptes paradoxus_, Fig. 3, p. 42), a typical inhabitant
and resident of the Arctic Steppes. The last great irruption took place
in 1888, and many birds reached even the extreme west of Ireland in May
and June of that year. A few weeks before, it had been announced to the
German papers that large flocks of this peculiar pigeon-like bird had
arrived in the eastern provinces; and though the vast majority vanished
as quickly as they had come, a certain number remained for a year or so
in the newly visited countries, and some even bred in England.

Twenty-five years before, in 1863, a similar migration had occurred,
though not perhaps on quite such a vast scale, and a few small flocks
had made their appearance in Western Europe on several occasions between
these dates.

It may not be generally known that no other bird has been honoured by
our Government in a like manner, for it is the only animal for whose
protection a separate Act of Parliament has been passed. In spite of
this unusual precaution, the species has not survived to add another
member to the resident British fauna. The wave of migration from the
east has come and vanished again just like so many others with which
history is familiar.

These migrations from the east occurring at the present day give us some
idea of those of which we have fossil evidence, and which all had their
origin in Central and Northern Asia. Almost all the species of mammals
to which I have referred as being of Siberian origin have been found in
the fossil state in comparatively recent geological deposits within a
certain very limited area. None of the typical species have ever been
found in Southern Europe proper, including the Mediterranean islands. It
must be remembered that though the Reindeer is a Siberian migrant, the
form of the Reindeer which was found in the Pyrenees belonged to a
distinct variety--in fact, to a much earlier migration which issued from
the Arctic European Regions, and to which I have referred in detail (pp.
150-158). Curiously enough, no deposits of these typical Siberian
mammals have ever been obtained in Scandinavia--only in Russia, Austria,
Switzerland (the lowlands), Germany, Belgium, France, and England. To
facilitate a study of the extent of these migrations, I have constructed
a map on which the probable course taken across Central Europe is
roughly indicated by dots (Fig. 16).

[Illustration: Fig. 16.--Map of Europe. The dotted portions represent,
approximately, the course of migration of the Siberian mammals. The
principal mountain ranges are roughly indicated in black.]

In the migrations of to-day we perceive the same tendency as in the
older ones of which we have fossil evidence, viz., generally a spreading
of species on a large scale over new territory, and then a gradual
shrinkage towards their original home, with an occasional survival of
small colonies in the invaded part. It must not be supposed that this
observation applies alone to the Siberian migration. In the case of the
Arctic one, precisely the same thing has happened, and we shall see that
the Southern (migration from the south) agrees in this respect with the
others.

As for the immediate cause of these migrations, it is to be looked for
either in the scarcity of food dependent upon a temporary or permanent
change of climate, or in an excessive increase in numbers of a
particular species. I do not propose to trace back migrations beyond the
Pliocene Epoch, or indeed much beyond the beginning of the Glacial
period, which is regarded as a phase of the most recent geological
epoch, viz., the Pleistocene. During the period in question, we have
indirect evidence of one vast migration from Siberia into Europe across
the lowlands lying to the north of the Caspian and to the south of the
Ural Mountains. There is a general consensus of opinion that this
migration took place in Pleistocene times. Professor Nehring thinks that
there can be no doubt (p. 222) that the Siberian migrants arrived in
Northern Germany after the first stage or division of the Glacial
period, and lived there probably during the inter-glacial phase which
occurred between the first and second stages--if indeed we look upon
this period as being divisible into two distinct stages.

Judging from the evidence of distribution of mammals in pleistocene
Europe, Professor Boyd Dawkins came to the conclusion (p. 113) that the
climate of our continent "was severe in the north and warm in the
south, while in the middle zone, comprising France, Germany, and the
greater part of Britain, the winters were cold and the summers warm, as
in Middle Asia and North America." "In the summer time the southern
species would pass northwards, and in the winter time the northern would
swing southwards, and thus occupy at different times of the year the
same tract of ground, as is now the case with the Elks and Reindeer."
Very different are the views of Professor Nehring on this subject.
According to him, the climate in Germany must have been extremely cold
and damp, resembling that of Greenland, though perhaps not quite so
arctic. Professor Nehring does not at all believe that southern and
northern species of mammals could have lived in Central or Northern
Europe at the same time; though of this we have undoubted geological
evidence (pp. 72-75). He thinks that the supposed commingling of
southern and northern types, which has actually been shown by Professor
Dawkins to occur, is either due to careless observation or to the fact
that some of the species need not necessarily have lived where their
bones were found (p. 133).

The most reliable conclusions as regards former conditions of vegetation
and climate can be drawn, according to Professor Nehring, from the
smaller burrowing mammals, such as the marmots, sousliks, etc. He is of
opinion that a great portion of Northern Europe, where their remains
have been discovered, must have possessed tundras and steppes, as we
find them nowadays in Siberia, and a climate similar to that of Northern
Asia. It is presumed that the climate, after the maximum cold of the
first stage of the Ice-Age, ameliorated so far as to permit these
mammals to exist in Europe.

The natural question, however, which is forced upon us in reading
Professor Nehring's interesting and suggestive work is, where did all
these steppe animals live during the earlier part of the Ice-Age? No
traces of their remains have been discovered in Southern Europe, and it
can therefore certainly be affirmed that they could not have lived
there. If Central and Northern Europe were uninhabitable for mammals,
Central and Northern Asia must have been even more so, and we have to
fall back upon the Oriental Region as a possible home of these species
during the assumed maximum cold of the Glacial period. In invading
Europe from the Oriental Region these Siberian mammals would have taken
the shorter route by Asia Minor and Greece, which was open to them. This
they certainly did not do, which proves that they came directly from
Siberia to Europe without retreating first to Southern Asia.

But it seems to me that there is no necessity for assuming such drastic
changes of climate to have taken place at all (compare pp. 75-80). We
really have no idea under what precise climatic conditions the Siberian
mammals lived in their original home. The only thing we can be certain
of is that the smaller burrowing mammals would not have chosen a wood
to live in, if they could possibly help it. Prairies, or sand-dunes with
short grass or shrubs, such as abound in Europe near the sea-coast,
would suit these species perfectly. If we suppose Northern Germany to
have been covered by sea (p. 156) during part of the Pleistocene Epoch,
forests would probably not have grown there for a very considerable time
afterwards, owing to the excessive salinity of the soil, but a tract of
sandy country would have been left on the retreat of the sea. Possibly a
slight change of climate in the original home of these steppe-species
may have reduced their habitable area, and thus caused their migration
into Europe.

But this migration problem cannot be solved without tracing the mammals
to their place of origin and investigating their early history. This I
shall attempt to do presently; meanwhile, it would be interesting to
note whether other groups of animals support Professor Nehring's
steppe-theory.

Among groups other than mammals, the most important, for the purpose of
drawing conclusions as to former physical conditions and climate, are
the mollusca. Their remains have been well preserved, and are easily
identified. Though Professor Nehring argues that the molluscs found
along with the small mammals harmonise perfectly with the assumption of
a steppe-climate (p. 212), I cannot at all agree with him. He enumerates
the following sixteen species as having been discovered by him:--

   1. Pupa muscorum.
   2. Chondrula tridens.
   3. Cionella lubrica.
   4. Patula ruderata.
   5.  Do.   rotundata.
   6. Helix striata.
   7.  Do.  hispidia.
   8.  Do.  tenuilabris.
   9. Helix pulchella.
  10.  Do.  hortensis.
  11.  Do.  obvoluta.
  12. Hyalinia radiatula.
  13. Succinea oblonga.
  14. Limnæa peregra.
  15. Clausilia sp.
  16. Pisidium pusillum.

Only two of these can be looked upon as typically northern species,
viz., _Patula ruderata_ and _Helix tenuilabris_, though both of them are
still found living locally in Germany. Some of the others are decidedly
southern species, like _Chondrula tridens_, _Helix obvoluta_, _H.
rotundata_, and _H. striata_. All the rest live and flourish, for
example, in Ireland at the present day, where, as we all know, anything
but a dry steppe-climate prevails.

Dr. Kobelt quite agrees with me in thinking that the remains of the
mollusca found along with the so-called "steppe-mammals" afford no proof
of a steppe-character of the country at the time when they were alive
(p. 166). Nor do the mollusca which have been found in England in the
Forest-Bed and the succeeding pleistocene strata support such a view.
The Forest-Bed, generally regarded as belonging to the Upper Pliocene, I
believe to be an inter-glacial pleistocene deposit--contemporaneous with
the loess formation in Germany. Of fifty-nine species of land and
freshwater mollusca which have been discovered in this bed, forty-eight
species, according to Mr. Clement Reid (p. 186), are at present living
in Norfolk, six are extinct, two are continental forms living in the
same latitudes as Norfolk, and the other three are all southern forms.
Not a single species has a particularly northern range. Of the land and
freshwater mollusca of the South of England in the succeeding
pleistocene deposits, six species are now no longer living in the
British Islands, but only one (_Helix ruderata_) can be looked upon as
an Arctic or Alpine form. After this short digression on the mollusca, I
will briefly recapitulate what is known about the early history of the
Siberian mammals, which will assist us in tracing the cause of their
migration to Europe.

We have in Siberia problems quite as difficult of solution as the
European ones. Volumes have been written to explain the former presence
of Arctic mammals like the Reindeer in Southern Europe, and the most
extraordinary demands on the credulity of the public have been made by
some geologists in their attempts to account for this comparatively
simple problem. In Northern Asia a somewhat similar phenomenon, but much
more difficult of explanation, has taken place. Mammals have been found
fossil in recent geological deposits in localities where they do not now
occur, and apparently the Siberian and the European deposits are of
about the same age. Now, however, comes the extraordinary difference. In
Europe the Arctic mammals went southward, but in Siberia the Southern
ones went northward. Not only do we find the Saiga-Antelope, Tiger,
Wild Horse, European Bison, Mammoth, and Rhinoceros in the extreme north
of the mainland of Siberia; their remains have even been obtained in the
New Siberian Islands. As these islands are situated in the same latitude
as the northern part of Novaya Zemlya,--indeed, not far south of the
latitude of Spitsbergen,--the fact of such huge mammals having been able
to find subsistence there at apparently quite a recent geological period
seems an astounding fact. It may be urged that their bones might have
been carried so far north by ice, or by some other equally powerful
agency. But Tcherski and all other palæontologists who have examined
these northern deposits are unanimous in the belief that these
herbivores and carnivores lived and died where their remains are now
found. "It is evident," says Tcherski (p. 451), "that these large
animals could only have lived in those extremely northern latitudes
under correspondingly favourable conditions of the vegetation, viz.,
during the existence of forests, meadows, and steppes." He also is of
opinion that the moist climate which evidently prevailed in Europe
during Post-tertiary (Pleistocene) times must have modified the Siberian
climate in so far as to render it milder. The existence of the
Aralo-Caspian basin (Fig. 12, p. 156) must also have tended in the same
direction. It appears then that, at the time when plants and animals are
believed to have retired southward in Europe before the supposed
advancing Scandinavian ice-sheet, no agency existed in North Siberia
which was able to suppress and to annihilate the forest and meadow
vegetation, and drive away the fauna connected with it. We know,
continues Tcherski, that such genera as Bison, Colus (_Saiga_),
Rhinoceros, Elephas, and Equus are met with in all horizons of the
diluvium of West Siberia. He therefore comes to the conclusion (p. 474),
that these and other facts imply that the retreat of the North Asiatic
fauna commenced about the end of the Tertiary Era (Pliocene), and that
it was continued very slowly throughout the Post-tertiary (Pleistocene)
Epoch, without any visible changes in its southward direction, even
_during the time of the most important glacial developments in Northern
Europe_. Only after the conditions disappeared which had produced the
augmentation of an atmospheric moisture, did the climate of North
Siberia become deadly to a temperate fauna and flora. Tundras then
spread over the meadow-lands and remnants of forests, whilst arctic
animals replaced the large ungulates and carnivores which had wandered
far away from their native southern home.

This is Tcherski's explanation of the extraordinary events which he has
chronicled, after years of the most arduous labour and under conditions
of peculiar hardship. And though his work cannot be over-estimated, and
his opinions should receive the most careful consideration, yet I fear
the explanation will not be looked upon as entirely satisfactory. Every
one will agree with him that the climate of Siberia must have been
greatly moister in pliocene and pleistocene times than it is now. The
Aralo-Caspian covered a vast area of South-western Siberia. Freshwater
basins existed along the east of the Ural Mountains, while Central Asia
was studded over with a number of large lakes, which have now almost
entirely vanished. But that the generally assumed refrigeration of
Europe must have had a chilling effect on the Siberian atmosphere seems
to me evident. That the whole of Northern Europe should have been made
uninhabitable owing to the advance of the Scandinavian ice-sheet, while
North Siberia at the same time supported forests, meadows, and a
temperate fauna, is incredible. At the approach of winter, at any rate,
the animals would have been driven southward for thousands of miles to
seek shelter from the snows and cold and to obtain nourishment, and it
would scarcely have been possible for them to undertake such vast
migrations at every season. Professor James Geikie's suggestion (p.
706), that the Mammoth and Woolly Rhinoceros could have survived the
Pleistocene Epoch in Southern Siberia, does not appear to solve the
problem, as that part of Asia must have participated in the great cold
which is said to have prevailed all over Europe.

Let us now concede, for the sake of argument, that the current views
regarding the pleistocene climate of Europe are correct. We are told by
Professor Geikie that the climate of Scotland during part of the
Pleistocene Epoch was so cold, that the whole country was buried
underneath one immense _mer de glace_, through which peered only the
higher mountain-tops (p. 67). If this was the state of climate in close
proximity to the Atlantic, it must probably have been still more severe
on the European continent. Now at the present time Siberia has the
reputation of being the coldest country in the world, and the mercury of
the thermometer is said to remain frozen for weeks during winter, even
in the south.

With the prevailing dampness in pleistocene times the snowfall
throughout Siberia would have been much heavier than at present, though
it would have modified the temperature to some extent. Under such
circumstances Southern Siberia could not have been a desirable place of
residence for large mammals. It would have been necessary for the
Mammoth and the other species referred to, to wander farther into the
extreme south of Asia or Europe to find a suitable refuge during the
arctic conditions which are supposed to have prevailed in Northern
Europe. To quote Professor J. Geikie's own words (p. 706): "They
(Mammoth, etc.) would seem to have lived in Southern Siberia throughout
the whole Pleistocene period, from which region doubtless they
originally invaded our Continent. But with the approach of our genial
forest-epoch (penultimate inter-glacial stage) they gradually vanished
from Europe, to linger for a long time in Siberia before they finally
died out." It is suggested, therefore, by the author that the Mammoth
and the other mammals whose remains have been discovered on the New
Siberian Islands found their way there during one of the late
inter-glacial stages of the Ice-Age. But there is no astonishment
expressed by Professor Geikie at the extraordinary change of climate
which must have occurred in Siberia to allow of such migrations. I can
find no very definite statement in this author's work as to the nature
of the climate in Europe during those inter-glacial phases, but he
remarks (p. 129) "that the evidence of the Scottish inter-glacial beds,
so far as it went, did not entitle us to infer that during their
accumulation local glaciers may not have existed in the Highland
valleys." There is no evidence, in other words, of the existence in
Europe of a milder climate than that prevailing at present. Still less
can there be any ground for the supposition that the climate of the
whole of Siberia ameliorated to such an extent that forests and meadows
could develop as far north as the New Siberian Islands; for if the
temperature in Europe was then about the same as now, that of Siberia
could not have been vastly higher than it is at present.

It is highly improbable, therefore, that a sufficiently mild climate
prevailed in the extreme north of Siberia during the so-called _later
inter-glacial periods_ to induce the mammals to which I have referred to
seek fresh pastures there.

The late Professor Brandt, one of the highest zoological authorities in
Russia, was of opinion that at the commencement of the Glacial period
the great mammals of Northern Siberia either perished or migrated
southward. From there they gradually penetrated into European Russia. He
believed that before the Glacial period a connection existed between the
Aralo-Caspian Sea and the Arctic Ocean, carrying warm water northward.
The gradual disappearance of this marine channel caused a decrease of
warmth in Northern Asia, so that large accumulations of frozen soil and
ice were formed, which still more depressed the temperature. This, he
suggested, probably took place at the time when the Glacial period
commenced in North-western Europe.

It has been urged against these views of Tcherski and Brandt, that the
bone beds in the Liakov Islands (New Siberian Islands) rest partly upon
a solid layer of ice of nearly seventy feet thick. This mass of ice, it
was thought, must have accumulated during the Glacial period. As the
bones rest upon it, the mammals could only have lived in those islands
in more recent times, after the Ice-Age had passed away. Nothing,
apparently, can be clearer, and yet in the face of this seeming proof
one feels, as I have mentioned before, that if such an extraordinary
revolution of climate as is implied by this admission had taken place,
we should be able to perceive the traces throughout the northern
hemisphere. In this dilemma, a suggestion made by Dr. Bunge, who visited
the New Siberian Islands recently at the instance of the Imperial
Academy of St. Petersburg, helps us out of the difficulty. He found
that, as a rule, these so-called fossil glaciers contain seams of mud
and sand, and he argued that the ice had formed, and is still forming at
the present day, in fissures of the earth. I entirely concur with this
view. Neither palæontology nor the geographical distribution of animals
lend any support to the other theory, and I think we may conclude that
Brandt's view in the main is probably the correct explanation of the
phenomena which we have discussed. Some important facts of distribution
are more easily explicable on this assumption. Why, for instance, should
the Siberian fauna of pliocene times have remained in Siberia and not
have migrated to Europe at that time? The pliocene mammals of Siberia
are mostly of southern origin. Their range increased enormously during
the epoch throughout Northern Asia. We should expect them, therefore, to
have crossed the Caspian plains, or even the low-lying Ural Mountains,
to pour into the neighbouring continent. But Professor Brandt explained
how they were prevented from spreading west. An arm of the sea stretched
from the Aralo-Caspian to the Arctic Ocean, thus raising an effectual
barrier between the two continents. There is some evidence for the
belief, as we shall learn presently, that this marine barrier existed
also during the early part of the pleistocene epoch. After having
greatly expanded during pliocene times, the fauna of Siberia gradually
withdrew from the northern regions during the earlier portion of the
succeeding epoch. It was only after the marine connection above referred
to ceased to exist, or became disconnected, that an entry into Europe
was possible.

A fauna, to some extent composed of species now inhabiting the steppes
of Eastern Europe and Siberia, poured into the neighbouring continent.
On p. 95 I have given a list of those which reached as far west as the
British Islands, but, as I mentioned, many other species came from the
east about this time. With regard to the early history of the Siberian
mammals, I favour a view somewhat between that of Tcherski and that of
Brandt. The outpouring of the fauna into Europe seems to me to indicate
that there was a sudden change of climate in Siberia. This was produced,
perhaps, by the rupture of the marine connection between the Arctic
Ocean and the Aralo-Caspian. Such an event would not only have caused
the sudden shrinkage of the area available for food-supply by lowering
the temperature in Siberia, it would have acted also as a means in
assisting the fauna to enter a new continent where an inconsiderable
number of mammals, already established, were mostly dispossessed of
their homes by the advancing eastern host.

Brandt's theory, however, of a marine connection between the Arctic
Ocean and the Aralo-Caspian is by no means generally accepted. That the
Caspian Sea was at that time greatly larger than it is at present, and
joined to the Sea of Aral and the Black Sea, is acknowledged by
everybody. That the deposits laid down by this huge inland sea reach as
far north as the shores of the river Kama, in Central Russia, is also
well known to geologists. But what comes rather as a surprise, is that
Professor Karpinski, whom we must take as one of the highest authorities
on the geology of Russia, asserts that this Aralo-Caspian Sea was
probably joined by a system of lakes or channels to the Arctic Ocean (p.
183). He was by no means the first, though, to put forward such a
theory. We have already learned that Professor Brandt held a somewhat
similar view, though he believed in something more than a connection by
mere channels, and Mr. Köppen, and also the Russian traveller Mr.
Kessler, agreed with him. So much was Professor Boyd Dawkins impressed
with their arguments at the time, that he wrote (_c_, p. 148): "Before
the lowering of the temperature in Central Europe, the sea had already
rolled through the low country of Russia, from the Caspian to the White
Sea and the Baltic, and formed a barrier to western migration to the
Arctic mammals of Asia."

In one particular Professor Dawkins's views differ from those of almost
all the previous writers. His connection between the Caspian and the
Arctic Ocean is placed to the west of the Ural Mountains, while it had
always been assumed by the Russian writers to have lain on the eastern
or Asiatic side of that mountain range. Thus, when Tcherski in recent
years announced that the tract on this eastern side of the mountains was
covered by freshwater deposits, his discovery seemed once for all to
settle the problem of the arctic marine connection in the negative. As
Professor Dawkins's theory has, however, received much additional
affirmative evidence by current faunal researches, a connection between
the Caspian (or Aralo-Caspian) and the Arctic Ocean (White Sea) may have
actually existed within recent geological times.

What _relict lakes_ are, has already been explained (p. 176), and their
fauna will again be referred to in a subsequent chapter. I might perhaps
be allowed to repeat that such lakes are supposed to have been flooded
by, or to have been in close connection with, the sea at some former
period. Many of the Swedish lakes are spoken of as relict lakes
(Reliktenseen), because they contain a number of marine species of
animals which have now become adapted to live in fresh water, but all of
whose nearest relatives inhabit the sea. One of these, the schizopod
crustacean _Mysis relicta_,--a shrimp-like creature,--which was formerly
believed to inhabit also the Caspian, is of particular interest. More
recently, the occurrence of this _Mysis_ in the Caspian was denied, but
though this denial has been confirmed by Professor Sars in his memoir on
the crustaceans of the great Russian inland sea, he has been enabled to
add two new species of _Mysis_ to the list of those already known to
science. These are _M. caspia_ and _M. micropthalma_, and both are
closely related to the arctic marine _Mysis oculata_. According to
Professor Sars, the genus _Mysis_ as a whole may be regarded as arctic
in character. The occurrence of these two species, therefore, in his
opinion, points to a recent connection of the Caspian with the Glacial
Sea.

A large number of other crustaceans have been described by the same
author from the Caspian. Of the order Cumacea, which is exclusively
marine, ten species are mentioned, but none of these seems to range
beyond the Caspian. Among the smaller species of crustaceans, a minute
pelagic copepod (_Limnocalanus grimaldii_) also inhabits the Baltic and
the Arctic Ocean. The marine isopod _Idotea entomon_, related to the
common wood-louse, has a similar distribution.

Genuine Arctic species of Fishes do not seem to occur in the Caspian,
though some, viz., _Clupea caspia_, _Atherina pontica_, _Clupionella
Grimmi_, and _Syngnathus bucculentus_, are almost certainly the
descendants of marine forms.

The Seal of the Caspian (_Phoca caspica_) is closely allied to the
Arctic Seal, and its presence alone in that sea indicates that at no
very distant date--at any rate since pliocene times--a closer connection
with the Arctic Ocean existed than at present.

I am sure it will be readily granted that there is zoological evidence
for the belief of such a connection or union between the two great seas.
However, it may be urged that owing to the presence of an ice-sheet in
Northern Europe during the Glacial period, such a connection must either
have been pre-glacial or have existed after that period. But the
connection must have occurred at a time when the Caspian extended far to
the north--when indeed the so-called post-tertiary Caspian deposits were
laid down (Fig. 17). Since the boulder-clay which covers the plain of
Northern Russia is assumed to be the ground-moraine of the great
northern ice-sheet, we might expect to find that the Caspian deposits
were not contemporaneous with it. Curiously enough, it has been shown by
Mr. Sjögren that all observations have pointed to the fact that these
two deposits do not overlie one another, but occur side by side, and are
therefore contemporaneous. This seems to warrant our belief, that while
the boulder-clay was being laid down in Northern Europe, the
Aralo-Caspian Sea had some communication with the White Sea.

[Illustration: Fig. 17.--Map of European Russia (after Karpinski). The
faintly dotted parts indicate the areas covered by boulder-clay, the
strongly dotted ones those exhibiting Aralo-Caspian and other
post-pliocene deposits.]

The boulder-clay of Northern Continental Europe, as already stated, is
now generally recognised to be the product of a huge ice-sheet which
invaded the lowlands of Continental Europe from the Scandinavian
mountains. Though Alpine glaciers at the present day produce little or
no ground moraine, these ancient larger ice-sheets, or "mers de glace,"
are believed to have deposited immense layers of mud containing
scratched and polished stones. Many of the latter have been carried
great distances from their source of origin. The Scandinavian ice-sheet
is supposed to have advanced as far south as the line indicated on the
map, after which it gradually retreated. On this point, however, as in
almost every detail connected with the Glacial period, geologists are at
variance. Professor James Geikie maintains, that there were no less than
four Glacial periods, separated from one another by milder inter-glacial
phases. On the Continent the view of two Glacial and one inter-glacial
period is, I think, more generally adopted. Professor Geikie's four
periods seem to me to have originated in a desire to correlate the
British pleistocene deposits with the continental ones, and at the same
time to retain the old view of the inter-glacial position of the
Forest-Bed. The two theories agree in so far as that in both the glacial
conditions culminate in a maximum glaciation, followed by a more
temperate phase of climate, with consequent retreat of the ice-sheets,
and finally by a renewed advance of the glaciers.

We are told that there is not the slightest doubt about it that a marked
but gradual decrease of temperature took place all over Europe either
during the beginning of the Pleistocene or towards the end of the
Pliocene Epoch.

We might reasonably suppose, then, that a similar climatic effect was
produced in Siberia, in consequence of which the fauna would have been
obliged to retreat from the extreme northern latitudes southward. No
doubt great efforts would have been made by the members of the Siberian
fauna--at any rate by those possessing strong power of locomotion--to
extend their range in other directions. But we have no evidence that a
migration from Siberia came to Eastern Europe at that time. It seems,
therefore, as if the barrier referred to by Brandt, Köppen, Boyd
Dawkins, and others (p. 222), had existed at this time. This would have
effectually prevented an overflow of the fauna from Siberia. Only in
deposits later than the lower continental boulder-clay do we find traces
of a Siberian migration. The time of maximum glaciation had then passed
away; the great glacier which was believed to have invaded the lowlands
of Northern Europe had again retreated, before the Siberian mammals made
their appearance in Germany.

It has been stated above (p. 226) that while the Russian boulder-clay
was being laid down, the Aralo-Caspian probably had some communication
with the White Sea.

But how can this view be reconciled with the existence of a huge _mer de
glace_ in the northern plains of Russia? The existence of the ice-sheet
has been conjured up in order to explain the presence of the
boulder-clay. But not long ago a very different interpretation of the
origin of this clay was given; and one, I may say, which explains the
history of the Siberian and the European fauna in a more satisfactory
manner than is done by the ice-sheet hypothesis. It is that the
boulder-clay is not the product of land-ice, but has been deposited by a
sea with floating icebergs. Thus the latter hypothesis does not deny the
existence of glaciers, but allows the mud to be deposited on the floor
of a turbid sea, instead of beneath an immense _mer de glace_. I need
hardly mention that this view, which was formerly universally accepted
by geologists, is now scouted by almost every authority, both British
and Continental. I should scarcely venture the attempt to revive old
memories and stir up again long forgotten controversies, were it not for
the fact that many new points have arisen in the course of the above
inquiries, which appear to me so very difficult to explain by the
land-ice hypothesis, while they are comparatively easy to understand
when we adopt the old theory of the marine origin of the boulder-clay.
But a few geologists even at the present day, while believing in the
land-ice theory, recognise that the marine hypothesis should have some
consideration shown to it. I need only remind glacialists of the work
recently published by Professor Bonney. "The singular mixture," he
remarks (p. 280), "and apparent crossing of the paths of boulders, as
already stated, are less difficult to explain on the hypothesis of
distribution by floating ice than on that of transport by land-ice,
because, in the former case, though the drift of winds and currents
would be generally in one direction, both might be varied at particular
seasons. So far as concerns the distribution and thickness of the
glacial deposits, there is not much to choose between either hypothesis;
but on that of land-ice it is extremely difficult to explain the
intercalation of perfectly stratified sands and gravels and of
boulder-clay, as well as the not infrequent signs of bedding in the
latter."

Now with regard to the land-ice theory, several serious difficulties
present themselves in connection with the origin of the European fauna.
In the first place, as the climate renders Northern Siberia almost
uninhabitable for mammals at the present day, how much more severe must
it have been during the time of the maximum glaciation in Europe. As the
then existing fauna was not driven into Europe, where could it possibly
have survived? Secondly, how can we reconcile the contemporaneous
existence of a great inland sea (the Aralo-Caspian) containing survivals
of mild Sarmatic times with an immense glacier almost touching it on its
northern shores? How did one of the most characteristic species of that
sea, _Dreyssensia polymorpha_, come to make its appearance in the lower
boulder-clay of Prussia and then disappear in the upper? And finally,
how are we to explain the sudden appearance of a Siberian fauna after
the deposition of the lower boulder-clay, except by the removal of a
barrier which had prevented their egress from Siberia?

If we assume that the continental boulder-clay of Russia has been formed
in the manner so ably explained by Murchison, de Verneuil, and von
Keyserling, viz., by a sea with floating icebergs, the temperature of
Siberia might have been higher than at present, and have supported a
fauna in more northern latitudes.

The contemporaneousness of the deposits of this sea with those of the
Aralo-Caspian is also rendered more intelligible. If we suppose,
moreover, the connection between the Aralo-Caspian and the White Sea
(Fig. 12, p. 156) to have existed at this time, we possess an
explanation of the method of migration of the Arctic marine species into
the Southern and of the Caspian species (_Dreyssensia_) into the
Northern Sea.

An inter-glacial phase is believed to have supervened after the
deposition of the lower boulder-clay, and it is during this period that
the Siberian species first appeared in Central Europe. If we assume then
that the retreat of the Northern Sea (Fig. 13, p. 170) opened up a
passage for the Siberian fauna, we have in this very fact also an
explanation of the extraordinarily large exodus of Asiatic mammals,
because the great reduction of the marine area in Northern Europe would
have had an important influence in lowering the temperature in Asia.
Only a sudden change of climate in Siberia could have brought about the
migration of the vast hordes of Asiatic mammals whose remains we find in
Central and Western Europe in deposits of that period.

Throughout this work we are made acquainted with facts which bear out
the view that the climate during the greater part of the Glacial period
was mild rather than intensely arctic in Europe. That a huge ice-sheet
could have covered Northern Europe under such conditions appears to me
very doubtful. No one can deny, however, that glaciers must have existed
during the Glacial period in all the mountainous regions of Central and
Northern Europe, though their existence is not incompatible with a mild
climate. Tree-ferns and other tropical vegetation grow at the foot of
glaciers in New Zealand. We need not even go so far afield, for in
Switzerland grapes ripen and an abundant fauna and flora thrive in close
proximity to some of the well-known glaciers.

One matter of importance still remains to be considered before
concluding this chapter, viz., the fauna contained in the English
geological deposit known as the "Forest-Bed." This interesting deposit
is exposed at the base of a range of cliffs on the coast of Norfolk. It
is composed of beds of estuarine and marine origin. The tree-stumps
formerly believed to be the remains of trees _in situ_ have, after more
careful examination, proved to be in all cases drifted specimens. A
portion of the "Forest-Bed" no doubt was laid down in close proximity to
a large river, and subject to being periodically flooded by it. It is
not absolutely certain, therefore, that all the mammals whose remains
occur in this deposit lived in England or whether only on the banks of
the river farther south. Nevertheless, we may take for granted that some
of them did. England was at the time connected with France and Belgium,
and for our purpose it matters little whether they had crossed the
Channel or inhabited those parts of the Continent through which the
great river flowed which sent its alluvial detritus as far as the plains
of Norfolk. All we have to remember is that certain mammals, which
appear to have originated in Siberia, and of which we have some
evidence that they crossed Central Europe in their westward course, had
now reached the great river just alluded to, which some geologists
believe to have been the Rhine.

I have had occasion to refer to a number of British mammals (p.
202)--some of which are now extinct--which I believe to have migrated
across the plains of continental Europe direct from Siberia. There were
twenty-six species of these Siberian mammals; and no less than ten of
these occur in the Forest-Bed. None appear in any older British deposit.
It is perfectly clear, therefore, that the Forest-Bed must have been
laid down after their immigration into Europe. They probably wandered to
Western Europe very soon after crossing the eastern boundaries of our
continent; the deposits in which they are found are therefore
contemporaneous. But we have learned above (p. 208), that the beds in
Eastern Europe in which the Siberian mammal-remains are found are more
recent than the lower boulder-clay. As already stated, the Forest-Bed
must also be more recent than the lower continental boulder-clay, and
should be included in the pleistocene series.

That the Forest-Bed is an inter-glacial deposit has been urged long ago
by various writers. Professor Geikie regards it as stratigraphically
contemporaneous with the peat and freshwater beds below the lower
diluvium of Western and Middle Germany, and as having been laid down
during the first Inter-glacial Epoch of the great Ice-Age. The fact
that no boulder-clay underlies the Forest-Bed seems rather a strong
argument against the view of its being an inter-glacial deposit. It lies
directly on what is known as the Newer Pliocene Crags. If the Forest-Bed
is included in the pleistocene series, as I suggested it should, the
crags, or a portion of them, would therefore be equivalent as regards
time of deposition to the lower continental boulder-clay. And again, if
the lower continental boulder-clay is contemporaneous with the Newer
Crags, the latter should also be classed with the pleistocene strata. I
can scarcely hope that geologists will be ready to admit such a sweeping
change of nomenclature without a protest. I venture, therefore, to
explain more fully my reasons for adhering to these unorthodox views.

Let us look once more at the map which I constructed (Fig. 12, p. 156)
to elucidate the migration of the Arctic terrestrial species to the
British Islands. It will be noticed that one continuous ocean extends
from the east coast of England across Holland, Northern Germany, and
Russia to the White Sea. At the same time Greenland and Northern
Scandinavia, Scotland and Southern Scandinavia, are united by a narrow
strip of land, and so are England and France. The waters of the Atlantic
and this North European Sea do not therefore intermingle at any point,
the two seas being absolutely independent of one another.

Such I assume to have been the geographical condition of Northern
Europe during the deposition of the Red Crag. Arctic mollusca were then
brought to the east coast of England, and boulders were scattered
through the beds laid down on that coast by icebergs which had been cast
off by Scandinavian glaciers on reaching the sea. Bedded clays which
have yielded arctic shells lie beneath the lower continental
boulder-clay on the Baltic coast-lands and on the coast of the White
Sea. According to Professor Geikie, marine clays on the same geological
horizon reach an elevation of some 230 feet. "It would seem, then," he
says, "that before the deposition of the lower boulder-clay of those
regions the Baltic Sea had open communication with the German Ocean" (p.
442). All these clays are evidently deposits of the same sea. But apart
from the fact that the Red Crag and these Baltic deposits are the oldest
of the upper Tertiary beds containing arctic shells, there is no
evidence that they are contemporaneous.

Overlying the same Baltic deposits comes the lower boulder-clay,
reaching a thickness of several hundred feet in some parts of Germany.
It presents, like the upper clay, frequent interstratification with
well-bedded deposits of sand and gravel. The scarcity of marine
mollusca, the occurrence of striated surfaces, and the occasional
presence of so-called giants' kettles, appear to favour the view, which
at present is generally adopted by both British and Continental
geologists, that the boulder-clay owes its origin to land-ice. I have
stated on several occasions that the view of the marine origin of the
boulder-clay agrees best with the known facts of distribution, and with
the history of the European fauna (pp. 80-86, and p. 129). It may be
urged that if the lower boulder-clay were contemporaneous with the
British Crags which succeeded the Red Crag, how can we explain the fact
that these crags contain plenty of shells, while in the lower
continental boulder-clay there are scarcely any?

But as yet our knowledge of the conditions of life of the marine
mollusca and of their distribution is extremely scanty. We are apt to
imagine that the bottom of the sea is covered by a more or less uniform
thick layer of shells; but whenever a careful survey of the nature of
the deposits now forming there has been made, such is by no means found
to be the case. Some of the best results obtained by that useful body,
the Liverpool Marine Biological Committee, have been precisely in this
direction. A most interesting account has been published by Professor
Herdman and Mr. Lomas on the floor deposits of the Irish Sea, in which
the authors state (p. 217), that "a place may be swarming with life and
yet leave no trace of anything capable of being preserved in the fossil
state, whereas in other places, barren of living things, banks of
drifted and dead shells may be found, and remain as a permanent deposit
on the ocean floor."

Owing to the fact of the peculiar geographical position of Scandinavia
at this time--an isthmus of land with a high mountain range lying
between the warm Atlantic and the cold Arctic Sea--the snowfall must
have been excessive, and large glaciers were evidently forming. These
produced icebergs as soon as the lower parts had advanced to the Baltic
coast-land and deposited their detritus in the sea. Immense masses of
mud and stones were thus cast to the bottom of the sea, and under these
circumstances no delicate mollusca or other marine life probably could
have developed within a considerable distance from the shore. To judge
from the direction pursued by the majority of the boulders from their
source of origin, the prevailing current during the deposition of the
lower boulder-clay was from north-west to south-east. It is possible
that little marine life, except free-swimming forms, would have been
able to live within the Russian area of this sea. But the free-swimming
larvæ of molluscs and other surface species were not prevented from
passing from the White Sea south-westward, and in sheltered localities
where little or no mud deposition was going on, these no doubt might
have developed into adults on the sea-floor. It is quite conceivable,
therefore, that in one portion of the North European Sea, which was
fully exposed to the destructive influences of the iceberg action, the
fauna was scanty or totally absent, while in another part there lived a
fairly abundant one. The unfossiliferous state of the lower continental
boulder-clay does not, therefore, offer any serious difficulty to the
supposition that some of the so-called Newer Pliocene Crags of the east
coast of England were laid down at the same time by the same sea.

This would also explain how the Arctic species come to inhabit the
Caspian, as the old Aralo-Caspian Sea could have had some communication
(Fig. 12, p. 156) with the North European Sea. And this again offers an
explanation of the otherwise mysterious occurrence of the Caspian
_Dreyssensia polymorpha_ in the lower continental boulder-clay.

The climatic reasons for the supposition that the boulder-clay is a
marine deposit have already been given (p. 66). However, it may be asked
what about the glacial flora which has been proved to have existed all
over the plains of Northern Europe?--what about the relics of this same
flora which still linger on in a few localities to the great delight of
the systematic botanist? They have been spoken of as indications of a
former Arctic climate in Europe. The presence of an Arctic species such
as _Dryas octopetala_ in any of the pleistocene deposits is often looked
upon as an absolute proof of a very severe climate having prevailed at
the time they were laid down. Professor Geikie tells us that the South
of England was clothed with an Arctic flora, when the climate became
somewhat less severe than it had been during the climax of the glacial
cold (p. 398). Relics of such a flora have been detected at Bovey
Tracey, in Devonshire, the Arctic plants found comprising _Betula nana_
and _B. alba_, _Salix cinerea_ and _Arctostaphylos uva-ursi_.

Now three of these four species of plants are still natives in the
British Islands, and all are forms which probably came to us with the
Arctic migration which I described in Chapter IV. They travelled south
with the reindeer, or before it, and may have covered large tracts of
country at the time. With the increased struggle for existence on the
arrival of the Siberian and Oriental migrants, they have probably been
evicted by these more powerful rivals. A discovery of their remains does
not necessarily indicate that a great change of climate has taken place
since they lived in the country. And certainly these Arctic plants
cannot be taken as indicating a low temperature, for it has been shown
that Alpine plants are mostly intolerant of very low temperatures.
"Arctic and Alpine species in the Botanical Gardens at Christiania,"
says Professor Blytt (p. 19), "endure the strongest summer heat without
injury, while they are often destroyed when not sufficiently covered
during the winter." Similar observations have been made in other
countries. For this reason they have to be generally wintered in frames
in the Botanic Gardens at Kew and Dublin, and are thus exposed to higher
temperatures than at present obtain in the British Islands. This fact
suggests that the Alpine and Arctic plants really did not originate in
countries with cold temperatures. They probably made their first
appearance long before the Glacial period--perhaps in early Tertiary
times--chiefly in the Arctic Regions, which at that time had a mild
climate. They have since become adapted to live in cold countries where
they flourish, provided they receive sufficient moisture in the summer,
and are protected from severe frost in the winter by a covering of snow.

When we carefully examine the present range of Arctic plants in the
British Islands, a curious fact presents itself which no doubt has
frequently been noted by botanists, viz., that some of the most
characteristically Arctic species, and some which are often quoted by
glacialists in support of their theories, flourish at the present moment
in very mild situations. I have already referred to the fact that the
Mountain Avens (_Dryas octopetala_) abounds in the west of Ireland
(County Galway) down to sea-level. Now it is well known that the mean
winter temperature of that part of Ireland resembles that of Southern
Europe, being no less than 12° F. (=7° Cent.) above freezing point. The
plant, of course, is here a native, and not introduced. This instance
shows clearly, that as long as more vigorous competitors are absent, and
as long as it is not exposed to severe frost or undue dryness, this and
allied species do just as well in a mild climate as in their native
Arctic home.

In his interesting essay on the distribution of the Arctic plants in
Europe during the Glacial period, Professor Nathorst adduces the fact
that all the localities but one, in which remains of such plants have
been discovered, lie either within or close to the limits of the maximum
extension of the supposed northern ice-sheet, or within those of the
former Alpine glaciers. Whether we look upon the boulder-clay as a
marine or a terrestrial product, it is quite conceivable that, in many
instances, the remains of the Arctic plants may have been carried by ice
to great distances from where they grew. The probability, however, is in
favour of most of them having lived where their remains are now found.
Now, it is a remarkable fact, that the single instance in Europe of a
deposit of Arctic plants having been found far removed from the maximum
extension of the northern ice-sheet is the one quoted above, viz., at
Bovey Tracey, in Devonshire. Even up to recent times Arctic plants may
have persisted at Bovey Tracey just as they do in Galway under the
influence of a mild coast climate. Similar circumstances may have led to
their survival along the shores of the sea which deposited the North
European boulder-clay, while they moved northward from the Alps along
with the glaciers, which always supplied them with an abundance of
moisture. Alpine plants probably became exterminated in the plain of
Central Europe at a much earlier period.


SUMMARY OF CHAPTER V.

What has been spoken of in the earlier parts of this book as the eastern
migration, refers in a general way to the animals which have come to
England from the east. But these are by no means natives of one country
alone. We can trace a number of the British mammals to a Siberian
origin, and also some birds; among many of the lower vertebrates and
invertebrates, however, there are few species which have reached us from
Siberia. They may have had their original homes in the Alps, in Eastern
Europe, or in Central and Southern Asia, and have joined in their
westward course the later, more quickly travelling mammals. Many
instances are given from all the more important groups of animals to
show how we may proceed in approximately identifying the home of a
species.

The periodical invasion into our continent of Pallas's Sandgrouse and
other birds, suggests an explanation as to the cause of the great
westward migration in former times of the Siberian mammals. Since a
considerable amount of fossil evidence is available to show the path of
migration pursued by these mammals, other important problems, such as
the time of their arrival in Europe and the geographical conditions
surrounding them, may perhaps be approximately ascertained, and thus
throw much light on the general features of the European fauna. It has
been proved by Professor Nehring that the Siberian mammals arrived in
Eastern Europe after the deposition of the lower continental
boulder-clay. He believes that the climate of Germany at that time had
ameliorated so far, after the maximum cold of the Glacial period, that
steppes with a Siberian fauna could exist. Other groups, such as the
Mollusca, however, do not support Professor Nehring's theory, and in
order to arrive at an independent solution of this and the other
problems referred to, a short history is given of the Siberian fauna.
Recent geological ages have witnessed the arrival in Southern Europe of
mammals now almost confined to the arctic and subarctic regions. In
Siberia, on the other hand, many southern species penetrated, apparently
about the same time, to the extreme northern limits of that country. The
greatest authority on the Siberian fossil fauna, Tcherski, believes that
this took place in pliocene times, the gradual retreat occupying the
whole of the Glacial period. If this were correct, the retreat from the
Arctic Regions would have occurred at the same time when, according to
our European authorities, Professors Nehring and Geikie, the much more
southern parts of our continent were already uninhabitable. But Siberia
could not have supported the large mammals at all at a time when Europe
was uninhabitable, as it would be difficult to conceive under what
geographical conditions the climate of the latter was arctic and that of
the former temperate. If the whole fauna was driven into Southern Asia,
how is it that the Siberian invasion of Europe occurred immediately
after the deposition of the lower boulder-clay, that is to say, after
the earlier part of the Glacial period? The difficulty can be met by the
supposition that both Europe and Siberia had a temperate climate at that
time. This view is supported by certain evidences, fully described, of a
connection between the Caspian and the White Sea, which would have had
the effect of influencing the climate. The Siberian fauna would thus
have been prevented from spreading westward in Pliocene and early
Glacial times. But on the disappearance of the marine connection, a way
would have been opened into our continent, which again had an effect on
the climate. The latter would have become sensibly colder and thus have
reduced the habitable area of the Siberian fauna.

Such geographical conditions would have been incompatible with a great
northern _mer de glace_, and the boulder-clay in Northern Europe could
not have represented a ground moraine but is a marine deposit. The sea
is supposed to have covered the Northern Russian and German plains, and
into it icebergs discharged the detritus which had accumulated on them
when they were still Scandinavian glaciers.

As regards the time of the arrival of the Siberian migrants in Europe,
the English Forest-Bed gives us an additional clue to its determination.
Since Siberian migrants are unknown from earlier deposits than this, it
is reasonable to suppose that they arrived in England about the time
when it was laid down. But since they appear in Germany in the
inter-glacial beds subsequent to the deposition of the lower
boulder-clay, the former are probably contemporaneous with the
Forest-Bed. Some of the deposits generally regarded as upper pliocene by
British geologists would therefore have to be classed with the lower
continental boulder-clay as lower pleistocene. In connection with this
theory some interesting faunistic data are given which seem to support
it.

In conclusion, the former presence of Arctic plants in Central Europe
and their bearing on the climatic problems are discussed.




CHAPTER VI.

THE ORIENTAL MIGRATION.


The Oriental migration is closely related to the Siberian. Both have
originated within the Asiatic continent, and in many respects a strict
line cannot be drawn between them. There can be no doubt that some of
the species which we regard as Siberian migrants had their original home
in more southern latitudes, and thus may have formed part of the older
Oriental migration. The home of that migration I take to be Central and
Southern Asia, that is to say, everything south of the Altaï Mountains
and the Caucasus. Its members have reached Europe across an old
land-connection which united Turkey, Greece, and Syria, while the
Siberian animals invaded our continent to the north of the Caspian and
Caucasus.

The Siberian immigrants into Europe on the whole are not very numerous,
but it is different with those from the more southern parts of the
Asiatic continent. The members of the Oriental migration form a very
large percentage of the European fauna. No other migration has affected
our continent so powerfully, because it continued uninterruptedly for a
very long time. Hence its results can be traced from one corner of
Europe to the other. We have seen that the Siberian migration only
commenced after the first portion of the Glacial period had passed away.
The Oriental, however, persisted throughout, or at any rate for the
greater part of that period. It commenced ages before it, in miocene
times, or even earlier. And as the Ægean Sea, which broke up the highway
of the Oriental migrants, is only of recent formation, there was a
steady westward march for a very considerable time. No doubt the
migration was also favoured by the fact that scarcely any formidable
barriers had to be crossed.

Many instances might be quoted of the same species forming part of the
Oriental and also of the Siberian migration, but as a rule the Siberian
migrant belongs to a distinct variety, or has such well-marked racial
characters as to be at once detected from its more southern relative.
Among the examples of Oriental migrants which I have occasion to bring
forward, such instances will be specially dealt with.

In its wild state the Red Deer (_Cervus elaphus_) is almost extinct in
the British Islands, though it still occurs in the moorlands of
Devonshire and Somersetshire in England, in the south-west of Ireland,
and in some localities in Scotland. Fifty years ago it was also found
wild in several other of the Irish western counties; and in the
seventeenth century it was common in most of the mountainous districts
of Ireland. Its remains have been found fossil in the marls and caves
of Ireland, and in the Forest-Bed, as well as in a large number of caves
in England. The history of the Red Deer in other countries is very
similar. In Scandinavia it flourished as far north as the sixty-eighth
degree of latitude, whereas it is now quite extinct on the mainland,
though still lingering on in some of the western islands. Denmark and
Switzerland know it no more, and it is almost extinct in Belgium. Nearly
throughout Europe where it occurs, its numbers are diminishing, greatly
owing, perhaps, to the relentless persecution by man, but its gradual
disappearance must likewise be partly due to other causes. Formerly it
inhabited every country of Europe and all the larger islands. It still
exists in Corsica and Sardinia, and at an earlier period it was also met
with on the island of Malta. The Red Deer found in Corsica and Sardinia
is smaller than that inhabiting Central Europe, and is by some
authorities regarded as a distinct species, which has been named _Cervus
corsicanus_. But Sir Victor Brooke has pointed out that the antlers of
some of the Scotch Deer agree in every point with those of the Sardinian
species. Indeed, the West European Red Deer altogether is a
small-antlered form, compared with the Eastern one. This character,
however, is only a racial one, and not of specific value. In the
pleistocene deposits of Eastern and Central Europe, a very
large-antlered race has been discovered, and identified by Professor
Nehring with _Cervus canadensis_--the Canadian Red Deer. Tcherski, the
Siberian traveller, believed that _Cervus canadensis_ was identical
with, or a variety of, the Asiatic species of Deer, _Cervus
eustephanus_, _Cervus xanthopygus_, and _Cervus maral_. Some
authorities--and to these belong Mr. Lydekker--think that we ought
perhaps to regard the whole number of Red Deer-like forms as local
varieties of one widely-spread species. Besides the deer already
referred to, the following belong to this same group:--_Cervus
cashmirianus_, _Cervus affinis_, _Cervus Roosvelti_, from North America,
and the North African _Cervus barbarus_.

The question now is, where have these varieties originated? Or, if we go
to the root of the matter, where is the original home of their
ancestors? Considering that so many _Cervidæ_ have been found in French
and English pliocene deposits, and that remains of the Red Deer occur
not only in the English Forest-Bed, but have been found associated with
those of the Pigmy Hippopotamus in Malta, it would only be reasonable to
suppose that the genus _Cervus_ had originated in Europe. It might also
be argued with equal force that the Red Deer had its birthplace in our
continent. But when we carefully study its present range this verdict
cannot be accepted. The view of the Asiatic origin of the Red Deer, so
ably maintained by Köppen, corresponds far better with its present
distribution, especially if we look upon the Asiatic, North American,
and North African forms as varieties of the same species.

If the Red Deer were of European origin, it must have come into
existence at a time when Malta was part of the mainland, when North
Africa and the British Islands were connected with the continent of
Europe, and of course before the deposition of the Forest-Bed. Such
land-connections existed probably during the Pliocene Epoch. Migrants
would have wandered from Europe into Asia. These would have developed
into larger races, which again furnished emigrants for North America.
The latter crossed by the old land-connection which once joined America
and Asia at Behring's Straits. During pleistocene times the large
Siberian race would now have re-migrated to the home of its ancestors in
Europe, for we find the remains only in Central and Eastern Europe,
indicating that an invasion of the Red Deer from Asia must then have
taken place.

Against this view of the European origin of the Red Deer, it may be
urged that deer are known from Indian as well as from European pliocene
deposits, and that a migration could have taken place from the Oriental
Region to Europe just as easily as from the latter to Asia. The majority
of the species of the genus _Cervus_ (in a wide sense), moreover, are
Asiatic, ranging to Borneo, Sumatra, and the Philippine Islands, all of
which islands have been separated from the mainland for a considerable
time. Finally, the original home of a species, as we have learned,
generally corresponds with the centre of its geographical range, and
this lies in the case of the Red Deer in Central Asia.

One of the highest authorities on the deer family, Sir Victor Brooke,
also was of opinion that the _Cervidæ_ originated in Asia, and from
there spread east and west. Of the two divisions into which true deer
are divided, viz., the _Plesiometacarpalia_ and the _Telemetacarpalia_,
the former is almost confined to the Old and the latter to the New
World. The only North American species belonging to the first division
is the Canadian Red Deer, which fact clearly indicates its recent
immigration to that continent.

There were probably two distinct migrations of the Red Deer into Europe.
An older one coming from Asia Minor into Greece, which stocked Sardinia,
Corsica, Malta, and North Africa in the first place, when these were
still connected with one another. This same migration likewise affected
western continental Europe, the Irish Red Deer being probably the
descendant of this very ancient stock. The latter entered the island
when it was still part of the Continent. The later migration of a larger
form came from Siberia and spread mainly over Eastern and Central
Europe, but it appears that it also reached England, although there is
no evidence of any of these Siberian deer having ever inhabited Ireland.

The range of this deer, therefore, to some extent corresponds to that
of another described on p. 153. We found then that two races of Reindeer
had migrated to the British Islands--one from the Arctic Regions, and
the other from Siberia, but that only the former had reached Ireland.

The so-called Irish Elk (_Cervus giganteus_) has been referred to the
Oriental migration, but, as stated below, it has some claims to be
regarded as a European. Unfortunately it is now extinct; it seems not
unlikely, however, that it inhabited Ireland when man had already made
his appearance on the island. Although its remains are found in such
extraordinary abundance in Ireland, it certainly did not originate
there. It lived also in England and Scotland, and in the Isle of Man, in
France, Denmark, Germany, Austria, North Italy, and Russia. Its remains
have been discovered even in Siberia. It must either have originated in
Europe and then migrated to Asia, or have had its birthplace in Asia and
wandered to Europe. There is nothing to lead any one to assert
positively that either of these two continents was the one in which the
original home of the Irish Elk was situated, and we can only be guided
in this case by the history of its nearest relatives. These are the
Fallow Deer (_Cervus dama_). There are two very closely allied species,
the Persian and the European, but several others have been discovered in
the Forest-Bed and the pliocene deposits of the Auvergne. As no remains
of the Fallow Deer are known from Asia, it seems probable that it and
also the Irish Elk originated in Southern Europe, and only invaded Asia
in early pleistocene times.

The Mammoth (_Elephas primigenius_) is a familiar example among a large
number of mammals which have come to us about the same time from Asia by
the Asia Minor route. It had a much wider range than the Irish Elk,
since its remains have been discovered in a large number of European
localities as far west as Ireland, also in Siberia, and even North
America. Though we have had _Proboscidea_ in Europe from the Middle
Miocene onwards, Mr. Lydekker (_d_, p. viii.) holds that "our
comparatively full knowledge of Lower Miocene and Upper Eocene mammalian
faunas of the greater part of Europe and North America, renders it
almost certain that neither of those regions was the home of the direct
ancestors of the _Elephantidæ_; and we must therefore look forward to
the discovery of mammaliferous Lower Miocene or Upper Eocene strata in
some other region of the (probably old) world which may yield these
missing forms."

The genus _Elephas_ makes its first appearance in the Upper Miocene of
India. Our European _E. antiquus_ is, according to Professor Zittel,
probably identical with _E. armeniacus_ of Asia Minor, while _E.
meridionalis_ agrees in all essential characters with the Indian _E.
hysudricus_. The Indian and European species of fossil elephants
altogether are very closely related, and the supposition that they all
have had their original home in the Oriental Region offers, I think, no
serious obstacle. The view of the European origin of the mammoth
especially is open to very serious objections. It does not occur in any
European pliocene deposits, and could not therefore have originated in
our Continent until pleistocene times. That it should then have
commenced its travels through Europe and Siberia to the New Siberian
Islands and North America seems almost an impossibility. But if we
suppose the mammoth to have had its home in India in pliocene times, it
could then easily have migrated to all the parts of the world where its
remains have been discovered.

Of the Asiatic mammals still living, some have only just crossed the
borders of Europe and then died out again. Similar cases have been
referred to in discussing the Siberian migration. Thus remains of the
camel have been found in Roumania and in Southern Russia in pleistocene
deposits. Others have lingered on to the present day. _Crocidura
etrusca_, for instance, still lives in Southern France, Italy, Sicily,
and North-western Africa. All its nearest relations are typically
Oriental species. In spite of the fact that a _Crocidura_ is known from
French and German miocene deposits, the general range of the genus
suggests an Oriental origin. In early Tertiary times a section spread
into African territory and another eastward as far as the island of
Timor. This may possibly have happened in miocene times, when a few
species likewise found their way into Europe. Many other mammals have
wandered still farther west, and now form an important percentage of the
European fauna.

Of Birds, too, a large number might be mentioned which had their home in
Asia and have found their way to Europe with the Oriental migrants. A
few instances have already been alluded to, and some additional ones may
be specified at random, without attempting to give a complete list.

Some of the Wagtails (_Motacilla_), as I mentioned in the last chapter,
have certainly come to us with the Siberian migration; but others seem
to be Oriental, such as _Motacilla melanope_, which is resident in
Southern Europe and migratory in the North. _M. campestris_--the Yellow
Wagtail--has a most peculiar discontinuous range. One colony breeds in
the British Isles and Western Europe generally, where it is known as a
summer visitor, retiring to West Africa during winter; another is found
from South-east Russia to Turkestan in summer, and winters in Southern
Africa. This fact may possibly be due to two distinct migrations from
Asia having taken place: an earlier one from the South-east--that is to
say, an Oriental one--and a Siberian one more recently. In this case the
members of the two migrations have not become sufficiently
differentiated to be regarded as distinct varieties. Though most of the
Wagtails have a somewhat northern range, none (except perhaps _M.
borealis_) are truly Arctic; and indeed, as almost all of them pass the
winter in southern latitudes, it may be assumed that they are of
southern and not of northern origin.

The Dippers (_Cinclus_) are practically unknown in the Central European
plain, but they occur in Western Europe as far north as Scandinavia,
also in the Alps, Carpathians, and Southern Europe, including Sicily and
Sardinia. Some authorities distinguish three species, others only one.
As a matter of fact, the difference between the three forms is very
slight, and their nests and eggs are undistinguishable. Eight other
species have been recognised, and all these are either Asiatic or
American. As one of the American forms is peculiar to Peru and another
to Ecuador and Columbia, and since the genus as a whole is a
mountain-genus, it probably is an ancient one. Its European range alone,
however, implies that it has inhabited our continent for a considerable
time and is no new-comer. We may look upon it as of Asiatic origin. The
ancestors have spread east and west, the European species having arrived
with the earlier Oriental migrants, and wandered along the Mediterranean
at a time when the geographical conditions of that sea were vastly
different from what they are to-day.

Not quite so ancient as the Dippers, but likewise Asiatic in their
origin, are the Bullfinches (_Pyrrhula_). The closely allied
Pine-Grosbeak (_Pinicola enucleator_) has already been referred to (p.
191) as a member of the Siberian migration. The distribution of the
European Bullfinch (_P. europæa_) is very interesting, as it occurs in
two distinct forms, by some authorities regarded as races, by others as
species. In all probability these two races owe their origin to two
different migrations from the same ancestral stock. We may suppose that
_P. europæa_ came to Europe along with the Oriental migration, spreading
chiefly over the south and west, while another branch developed in
Siberia into the larger and more brilliant race (_P. major_), which
subsequently entered the neighbouring continent with the Siberian fauna.
The latter race inhabits, according to Mr. Saunders, Northern and
Eastern Europe, and also Siberia. All the other species--there are eight
more--except one, are found in Asia. This one species, which inhabits
the Azores, appears to be more closely related to one of the Siberian
bullfinches than to the European. It stands isolated, and is an
extraordinary instance of discontinuous distribution, as no Bullfinch
inhabits either Madeira or the Canary Islands. We must assume that the
form connecting it with the Asiatic probably lived in Southern Europe,
and has become extinct.

One of the most typically Oriental genera of birds is _Phasianus_, to
which our Common Pheasant belongs. Out of twenty species, nineteen are
found exclusively in Asia, most of them being confined to the central
plateaux of that continent. Only one species passes the confines of
Asia into Greece, Turkey, and Southern Russia. This is _Phasianus
colchicus_. Formerly, however, the Pheasant appears to have had a wider
range in Europe, for three species are known fossil from France.
Altogether, it is not quite certain whether the Pheasant is not really
an indigenous bird in the British Islands, having survived from
pre-glacial times. It is believed that the Romans brought it to England,
but there is no record of an introduction at that time.

Among the older Oriental bird migrants might be mentioned the
Fire-crested Wren (_Regulus ignicapillus_), which has even occasionally
visited England. It becomes commoner as we go south-eastward. In Asia
Minor it is more abundant than the Gold-crest; and throughout the year
it is resident in Southern Europe, where it occurs in Turkey, Greece,
Italy, Spain, Sardinia, and Malta. On the opposite shore, in North-west
Africa, it again makes its appearance, and its range extends westward to
the Canaries (_R. teneriffæ_) and Madeira (_R. maderensis_).

The genus to which our common Goldfinch belongs, viz., _Carduelis_, is
also probably of Oriental origin, and may be looked upon as one of the
earlier migrants. That species (_C. elegans_) breeds throughout Europe,
except in the extreme north, but it is especially abundant in Southern
Europe and North-west Africa. It is also resident in Madeira and the
Canaries. Eastward its range extends to Persia. A larger race (_C.
major_) inhabits Western Siberia and crosses the European border into
Russia. It interbreeds in Siberia with _C. caniceps_, an East Siberian
form.

A few instances of Reptiles and Amphibia with a similar range will show
that the Oriental migration was not confined to the higher vertebrates.

Two species of the genus _Eremias_ (_Podarcis_) occur in South-eastern
Europe. This is a genus of Lizards with rather a wide distribution,
ranging from Central Asia to South Africa southward and China eastward.
Altogether there are twenty-four species, two of which just enter
Europe; and of the rest half are Asiatic and half African. Even if the
genus were of African origin, it is extremely unlikely that the Asiatic
species came by way of Europe. We may assume, therefore, with a fair
degree of probability that the two European species wandered westward
along with the Oriental migrants.

The genus _Ablepharus_ belongs to a family of Lizards in which the legs
are either very fully developed, or quite absent as in the Slow-worm
(_Anguis fragilis_). It is an ancient genus, having a wide range from
Central Asia to Australia on the one hand, and to South Africa on the
other. One species of this Scink-like Lizard, viz., _Ablepharus
pannonicus_, enters Europe in the south-east, inhabiting Greece as far
north as Southern Hungary. In Asia it is found in Syria and North
Arabia. This clearly signifies that the Lizard is an Oriental migrant.

Among the Snakes which participated in the Oriental migration might be
mentioned _Eryx jaculus_, whose home is probably in Western Asia. It is
known in Europe from the Greek islands of Tinos and Naxos, from Turkey
and Southern Russia. Another, a peculiar worm-like form, lives
underground in damp earth and under stones--_Typhlops lumbricalis_. This
species inhabits the mainland of Greece as well as the Greek islands,
and Asia Minor as far as the Caucasus.

A most interesting case of distribution is that of the pretty little
Toad so well known on the Continent under the name of "fire-toad"
(_Bombinator igneus_). Though some authorities, such as Boulenger,
recognise only one form of _Bombinator_,[1] others are of opinion that
two well-marked varieties exist in Europe. These are looked upon by Dr.
von Bedriaga as good species, but he acknowledges that they are rather
critical and difficult to identify. No other species of _Bombinator_
occur in Europe. _Bombinator pachypus_, the western race,--or if we
choose to call it species,--occurs in France, Germany, Switzerland,
Austria, Sicily, and Greece. _B. igneus_--the eastern race--is found in
Southern Sweden, Denmark, Germany, Austria, and Russia. The latter has
therefore a more northerly and easterly range. The species is not known
from Siberia, but makes its appearance again in China in a form which,
according to Dr. von Bedriaga, does not quite agree with either of the
two European races.

Now if we supposed _Bombinator_ to have originated in Europe, its
absence from the British Islands, most of the Mediterranean islands, and
the greater part of Scandinavia would not be easy of explanation, while
as an Asiatic migrant the European range is more readily understood. Its
apparent absence from Western Asia might quite likely be due to the fact
that the zoology of that part of the Continent is only now being
investigated. The latter has, moreover, undergone great physical changes
in recent geological times. The supposition that one migration of
_Bombinator_ from the south-east has taken place, and then another from
the east, seems to explain this case of distribution, as other similar
ones, in a most satisfactory manner.

The Tree-Frog (_Hyla arborea_) must be an ancient species, but it is not
of European origin. Few genera of Amphibia have a wider distribution
than _Hyla_. There are only three species in Asia, Europe, and Africa,
the remaining 129 being confined to America and Australia. Two of the
three Old World Tree-frogs are so closely allied that until recently
they were regarded as mere varieties of one another. These are _Hyla
arborea_ and _H. chinensis_. The former is found in Asia Minor, Persia,
China and Japan, and in most of the Mediterranean islands and Southern
Europe generally. It does not occur in the British Islands, Norway, or
North Russia, but in South Sweden, Germany, France, and Spain. It is
also known from North Africa and from Madeira, the Canaries, and the
Salvages. The occurrence of the Tree-Frog on so many of the
Mediterranean islands is of particular interest, especially as four
well-marked varieties have been distinguished by our leading
herpetologists, so that the more minute features of the various forms
can be traced from island to island, adding one more proof--if proof
were needed--of their former continuity. Of course, that _Hyla arborea_
must be considered an Oriental migrant seems so evident that it scarcely
needs further comment.

A number of mollusca might be mentioned whose range indicates that they
have migrated to Europe from Asia Minor. _Buliminus pupa_ is one of
these. It is known from Asia Minor, Greece, South Italy, Sicily, and
Algeria. _Buliminus detritus_ is perhaps better known, being common in
some parts of Germany. From there its range spreads east as far as Asia
Minor. Many closely allied species inhabit Western Asia, to which they
are confined, while others enter on European territory in some of the
Greek islands. _B. fasciolatus_ occurs on the islands of Crete, Rhodes,
Cyprus, and in Greece and Syria. Most of the species of _Buliminus_ have
a very restricted range, but _Buliminus obscurus_ is found almost all
over Europe, from Ireland in the west to the Crimea and Transcaucasia in
the east.

Whether the sub-genus _Pomatia_ of the genus _Helix_--to which the
so-called Roman Snail belongs--is of Asiatic origin, or whether some of
the species have migrated from Europe to Asia, I am not prepared to say;
but there can be no doubt that _Helix pomatia_ has reached Western
Europe from the east.

On the whole, the number of mollusca which we might point to as having
migrated to Europe is not large, the great majority being indigenous to
our continent. However, some of the other groups of invertebrates differ
very materially in that respect from the mollusca. I cannot leave the
consideration of the mollusca without referring to the fact that there
appears to be a very important centre of distribution in South-eastern
Europe. It is from this centre that many species have spread north and
south, east and west. Take, for example, the genus _Clausilia_, a small
land-shell shaped like a pointed round tower, and abundant on old walls
and tree trunks. In England we have four species of _Clausilia_, in
Ireland only two. In the greater part of Spain only our common _Cl.
bidentata_ occurs. As we go east the number of species rapidly
increases. A maximum is reached in South-eastern Europe, where hundreds
of different kinds are found. Towards Northern Europe a similar decrease
of species takes place. So far the history of the _Clausiliæ_ seems
perfectly simple. An active centre of origin appears to exist in
South-eastern Europe, from which the species radiate out in all
directions. But when we come to look more closely into the
extra-European distribution of the genus, and especially when we
examine its past history, we find that its origin is extremely complex,
and dates back to a much more remote period than would have been
imagined, had we merely taken into account its present range in our own
continent. Professor Boettger, who is the highest authority on
_Clausilia_, tells us that the genus is known from the earliest deposits
of the Tertiary Era. About 700 species are now known, and these have
been sub-divided by Professor Boettger and others into a number of
sub-genera. Some of these are extinct, but the great majority are still
living. The sub-genus _Phædusa_ occurs in the eocene and oligocene of
Southern Europe, but it is extinct as far as our continent is concerned.
Close upon a hundred species, however, still inhabit India, the Malayan
Islands, China, Ceylon, and Japan. Then again, the sub-genus
_Laminifera_ occurs in the oligocene and miocene of Central Europe, and
survives in a single species, _Cl. Pauli_, in South-western France. The
groups _Garnieria_ of China, _Macroptychia_ of East Africa, _Boettgeria_
of Madeira, and _Nenia_ of South America, have no fossil
representatives. We have here some very remarkable cases of
discontinuous distribution which testify to the antiquity of the genus,
and this is certainly confirmed by the fossil evidence. However, it is
hardly likely that the headquarters, as it were, of _Clausilia_ have
always been in South-eastern Europe. Most of that part of the Continent
has been submerged since eocene times more than once. The peculiar
distribution of the genus might be explained, I think, if we supposed
the original home of _Clausilia_ to have been in Southern Asia, that
from this centre Southern Europe was colonised, where a new centre
developed in oligocene and miocene times, sending colonies off to
Madeira and across the old land-connection which united Northern Africa
and South America about that time. The most active centre of development
then gradually shifted eastward again, while the older centres were
perhaps submerged during the physical changes in the distribution of
land and water.

I should have mentioned that the species wandering westward and
northward from this South-European centre of distribution, would
naturally have joined the migrants which came from beyond the borders of
our continent. They might thus appear to be true Oriental migrants, and
on a previous occasion I grouped all these together under the term of
"Southern Fauna," as I assumed the observer to be stationed in the
British Islands. All new-comers from the south-east, south, or
south-west of Europe would be to him southerners quite irrespective of
their original home, which might be in Southern Europe, Asia, or Africa.

The Swallow-tail is well known to all collectors of Butterflies in
England, though it has of late years become very rare and is now
confined to a few localities in the east of England. The members of the
family _Papilionidæ_, to which it belongs, are mostly large and striking
species, and their distribution is therefore more accurately known than
that of the smaller and less conspicuous butterflies. Only four
different kinds of Swallow-tail Butterflies inhabit Europe, but in
Southern Asia and the Malay peninsula they attain their maximum as
regards numbers; and there we find a great many species of this genus
_Papilio_. Of the four European species only one, viz., _Papilio
hospiton_, is peculiar to Europe; all the others range into Asia. It
would seem, therefore, as if this genus was an Asiatic one and had
migrated to Europe, and that the route taken was the one from Asia Minor
across to Greece. We have a similar case in the closely allied genus
_Thais_ two of the three European species living also in Asia Minor.
_Thais cerisyi_ inhabits some of the Greek islands, as well as the
mainland of Turkey and Greece.

Another genus of the great family _Papilionidæ_ with which most
lepidopterists are well acquainted is _Parnassius_. What
butterfly-hunter has been in Switzerland without hearing of, or seeing,
the famous _Parnassius Apollo_? We have four European species of
_Parnassius_, only one of which is peculiar to our continent, but the
locality where it occurs, the Caucasus, is on the borders of Asia.
Almost all the other species are Asiatic, none however range to the
south. Its headquarters, and I think its original home, are the
mountains of Central Asia. From there it has spread--some species to
the Himalayas, and a few to Europe and North America. But these
migrations are not of very recent date. _Parnassius_ no doubt arrived
accompanied by a large number of other Central Asiatic mountain insects
and plants. I shall refer to the latter again when dealing with the
origin of the Alpine fauna, but meanwhile it might be mentioned that the
famous Swiss "Edelweiss" (_Leontopodium alpinum_), which we are
accustomed to regard as a typical Alpine plant, is certainly of Asiatic
origin. In some parts of Southern Siberia it is one of the common
meadow-flowers, and ranges from there south into Kashmere, but not
northward. Like the _Apollo_, it does not occur in Scandinavia or
Northern Siberia. Both plant and insect evidently migrated from Central
Asia, directly westward along the southern border of the sea, which
extended from that region as far as the European Alps in early Tertiary
times. At that time the Caucasus was possibly still connected with the
Balkan Mountains, across what is now the Black Sea, and that may have
been the highway on which they travelled west.

Some of the Clouded-Yellows--butterflies appertaining to the genus
_Colias_--formed part of the Oriental migration. The genus is
undoubtedly of Asiatic origin, and while many of the species have turned
northward, ranging across Siberia and North America, others have taken a
southern and westward turn and thus reached Europe. We have two
Clouded-Yellows in Western Europe, and both of them must have come with
this migration.

A very good example of an Oriental migrant is _Danais chrysippus_, a
magnificent butterfly found in Greece and Southern Italy. In Asia it is
known from Syria, Persia, and from the whole of the southern portion of
the Continent. The genus _Danais_ (in its wide sense) is a large one,
and principally occurs in the warmer regions of Asia. Three species are
found in North America and only one in Europe.

Among the beetles belonging to this migration, there is one of very
considerable interest from a distributional point of view, for all the
species of the genus--even the whole family to which the genus
belongs--are what is known by zoologists as "Commensalists." These are
animals habitually associating and living in close connection with
others with which they are not tied by any family relations or kinship.
Such a state of close and permanent friendship is called "commensalism."
Now it appears as if the members of this family of beetles
(_Clavigeridæ_) had of their own free will formed such a close
connection with colonies of ants--sometimes with one species, sometimes
another. They are the permanent guests of the ants, and in return they
secrete a fluid which is apparently highly prized by them. All of the
_Clavigers_ are provided with peculiar club-shaped antennæ, with which
they ungraciously beat their hosts, when they are in want of food.
According to some authorities, they even occasionally gnaw at the pupæ
and larvæ of the ant with which they live.

Such beetles naturally can only have extremely limited means of
distribution, and they are comparable in that respect with the woodlice
of the genus _Platyarthrus_, to which I have already had occasion to
refer. All the species of _Claviger_ are confined to Europe, chiefly to
the south, but one species, _Cl. testaceus_, has wandered farther north
and occurs in the nest of the ant _Lasius flavus_ in the south of
England, Ireland, and Scotland. Though none of the _Clavigers_ can be
claimed as Oriental migrants, the centre of distribution of the genera
belonging to the _Clavigeridæ_ is in Southern Asia, and it is probable
that the ancestors of the European _Clavigers_ have spread westward from
that region to Europe, eastward to Australia and Japan, and southward to
Madagascar and South Africa. The genus _Hopatroides_, belonging to the
same family as the so-called Spanish-fly (_Tenebrionidæ_), has twelve
species in Western Asia and Greece. One only, _H. thoracicus_--an
instance of discontinuous distribution--occurs in Andalusia. _Amphicoma_
is represented in Western Asia and the Balkan peninsula by fifteen
species, while three others are met with in North-west Africa and
Southern Spain.

A genus of Dragon-fly, _Onychogomphus_, has in Europe a somewhat similar
distribution to _Claviger_, but it has besides a very extensive foreign
range. There are altogether thirty-five species; of these ten are
Holarctic, twelve Oriental, five Mascarene, and eight Ethiopian. The
centre of distribution is therefore in the Oriental region, and we may
assume that in all probability the genus has originated there, the
European species having travelled west with the Oriental migration at an
early date of the Tertiary Era.

_Ryothemis_, another genus of Dragon-flies, has originated perhaps
somewhat farther east than the last, for no less than thirteen species
are found in Australia, a like number in India, five in Madagascar and
Africa, and five in the Holarctic region. Both of these genera are
entirely absent from America, and they have possibly travelled to Europe
together.

Among the European _Orthoptera_--the group to which our Earwigs and
Grasshoppers belong--there are also a good many instances of Oriental
migrants. One of the most striking of these is the curious "praying
insect" (_Mantis religiosa_). It occurs all over Southern Europe, and
ranges as far north as the north of France. It is also found in Southern
Germany and in Austria, and has a vast extra-European range. There are
even records of its occurrence from all parts of Southern Asia and Java
and a great part of Africa. That it belongs to an extremely ancient
genus is testified by the fact of its presence in Mauritius, Japan,
Australia, New Zealand, South America, and Madagascar. The genus
_Bacillus_--to which the typical Stick-insects belong--has a somewhat
similar geographical distribution. But no less than four species of
_Bacillus_ are known from Europe, according to our great authority Mr.
Brunner von Wattenwyl--all from the south; and some of these also range
into North Africa. There are thirty-two other species distributed over
Southern Asia, Africa, Australia, New Zealand, and the Sandwich Islands.

Volumes, indeed, might be filled with lists of species and genera of
terrestrial invertebrates of Oriental origin, but I will not weary the
reader with further enumeration of such instances. Just two more,
however, before concluding, as I have not alluded to the large group of
the _Arachnida_.

Two peculiar spider-like genera, viz., _Galeodes_ and _Rhax_, are found
in Southern Europe. Both occur also in North Africa, and in Western and
a portion of Southern Asia. As the whole family altogether has an
Asiatic character, I cannot agree with Mr. Pocock, who considers them of
European origin and believes that they are migrating eastward.

But not only terrestrial forms migrated to Europe from Western and
Southern Asia. Freshwater species also took part in this great Oriental
migration. I need only refer to the freshwater Crab (_Thelphusa
fluviatilis_), with which Southern Europeans are familiar. It is the
sole representative of a large genus which ranges east as far as
Australia and southward to Madagascar and the Cape of Good Hope. The
European species is found in Turkey, Cyprus, Greece, Southern Italy,
Sicily, North Africa, Southern Spain, Syria, and Persia.

There is a corresponding flora with a range exactly similar to that of
some of the animals quoted. Thus the Balkan Rhododendron (_Rhododendron
ponticum_) is again met with in the western Mediterranean region in
Southern Spain. The Cedar occurs in local varieties in the Himalayan
Mountains, in the Lebanon, and the Atlas Mountains. Both of these are
instances of discontinuous distribution, a proof of their antiquity; but
a large number of plants have a continuous range between Asia Minor and
Spain.

On looking through these few instances of what have been called Oriental
migrants, one cannot help being struck by the fact that the species
after their entry into Europe evidently did not all follow the same path
during their westward advance. We have seen that a good many seem to
have travelled either due west or north-west on entering our continent
from Asia Minor. They may now perhaps be found in Greece, Southern
Italy, Algiers, and Spain, also probably on some of the intervening
islands in the Greek Archipelago, in Sicily, Sardinia, and Corsica, or
they may have travelled north-east and occur in the Alps. This
distribution indicates undoubtedly, as I have already set forth in
another memoir (_c_, p. 459), that land extended from Asia Minor across
Greece to Southern Italy, that the latter again was disconnected with
Central Italy, but united with Sicily, Sardinia, and Tunis, and that the
Straits of Gibraltar did not exist at the time when these species
migrated westward. Some species are only to be found as far west as
Southern Italy, while others occur in Central and Northern Europe,
scarcely in the South, and not at all in the larger Mediterranean
islands or in North Africa. This appears to me to indicate that the late
comers from the east found that geographical changes had taken place in
Southern Europe which prevented them from following the same track as
the older immigrants. They were now obliged to turn directly northward
and then westward. It may be asked, why should not the earlier migrants
have taken the same route? This question will be answered immediately.
Meanwhile it should be clearly understood that there probably was an
older and a newer migration from the east. The Oriental genera--from
whose general range we know that they must be very ancient indeed, such
as _Mantis_ and _Bacillus_--are almost invariably confined to Southern
Europe. There they are frequently found on some of the Mediterranean
islands. The earlier migrants therefore went westward and the later ones
northward.

Let us now inquire a little into the reasons why such different courses
were pursued by the migrants--why the Oriental migration divided into
two streams, an older and a newer.

During early Tertiary times, and probably throughout the Miocene and
Pliocene Epochs, the Ægean Sea did not exist. From the island of Crete
to the Peloponnesus, and from Asia Minor to Thessaly and Macedonia,
stretched a vast and fertile plain dotted over with numerous freshwater
lakes. Gradually the sea encroached upon this land from the south, owing
chiefly to extensive subsidences having taken place. Only very recently,
says Professor Suess, did the whole of the Ægean continent subside (i.,
p. 437). Huge cliffs of levantine freshwater deposits now mark the new
coast-line, and the Mediterranean advances steadily towards the Black
Sea and the Sea of Asov. A new order of things is now established,
continues the famous author of _Das Antlitz der Erde_; where there were
high mountains we now behold a deep sea, in some places many thousand
feet deep. All this took place quite recently,--geologically
speaking,--certainly in post-glacial times; and man may even have
witnessed these imposing events. Most geologists admit the correctness
of these views. They are, moreover, built upon such solid geological
evidence, that even if the science of zoogeography had not yet taught us
anything, naturalists would not hesitate in accepting them.

Animals and plants were free to migrate from Central and Southern Asia
to Greece by land for untold ages. The vast accumulation of mammalian
bones which have been discovered at Pikermi, and so ably described by
Gaudry, are probably to a large extent the remains of Asiatic immigrants
to Europe. Many of these resemble forms still living in South Africa,
which implies that a highway existed also at that time between Asia and
Africa. Among these is a giraffe and antelopes closely allied to
African species, and other most interesting mammals.

In still earlier European deposits--the Miocene--we find the ancestors
of modern Elephants, which are probably of Asiatic origin. The remains
of several kinds of monkeys occur, whose nearest relations are now
confined to Southern Asia. Altogether the fauna bears a strong Asiatic
facies. Many of our European terrestrial invertebrates probably arrived
about this time from Asia. The struggle for existence being keener and
the facility for migration much greater in the higher vertebrates,
they--or at any rate the mammalian faunas--were subjected to more rapid
changes than the invertebrates. I have repeatedly expressed my belief
that a great number of our familiar insects and mollusca inhabited
Europe long before our present mammals came into existence.[2]

Let us now follow one of the miocene Oriental migrants starting from
Central Asia on its way to Europe. Very soon after leaving its home, it
must have encountered a sea which extended at that time from the Eastern
Mediterranean to the borders of Afghanistan. In following a westward
course, the emigrant was compelled to keep along the northern shore of
it. We do not know the state of the physical geography of the region
between the Black Sea and the Tianshan Mountains, but it seems certain
that a considerable extent of dry land enabled a wanderer from Central
or Southern Asia to reach the Balkan peninsula by skirting the northern
shore of that large miocene sea. No miocene deposits occur north of
Teheran or of the Upper Euphrates, nor are they known from the islands
of the Ægean Sea or the lands surrounding it. From the Balkan peninsula
it was possible for our migrant to reach the European Alps, which were
then slowly rising as a peninsula out of the western portion of the
great miocene sea. What are now the Alps was then hilly ground, which
was being raised from the bottom of the sea. It was no doubt connected
with the Balkan peninsula, so that an intercourse of species could take
place between this newly-formed peninsula and Central Asia. I say
peninsula, because the miocene sea almost completely surrounded it. From
the Western Mediterranean a wide gulf extended up the Rhone valley into
that of the Rhine as far north as Maintz. Then skirting along the
northern outliers of the Tyrol, the gulf can be followed as far east as
Transylvania. It is quite probable that it extended much farther east
still, but there is as yet no geological evidence forthcoming. At any
rate, our Asiatic migrant turning northward from the Balkan peninsula
found its farther progress barred once more by an arm of the same sea
which in its earlier peregrinations had stopped it from going south (cf.
Suess, i., p. 406).

In later miocene times the sea does not seem to have surrounded the
Alps to the same extent as it did before, but it certainly extended from
the Eastern Alps to the shores of the Sea of Asov, so that the direct
northward passage was still more or less barred to the Oriental
immigrants. At the same time Alpine species were now able to emigrate to
the North European provinces. During the last stages of this epoch, the
same sea increased its area very considerably in an eastward direction.
One continuous expanse of water now stretched from the Alps as far as
the Sea of Aral in Central Asia, perhaps even farther.

During pliocene times especially, the northern parts of the Balkan
peninsula were occupied by a series of freshwater lakes, while Greece
was joined to Southern Italy, Sicily, and Tunis. Central and Northern
Italy were represented by a long narrow peninsula connected in the north
with the Alps. Corsica and Sardinia were joined to Sicily, and the
Straits of Gibraltar did not exist. When I first published my views
regarding these geographical conditions of the Mediterranean area,
Professor Depéret was good enough to send me his criticisms from a
purely geological standpoint. He is of opinion that though Sicily and
Sardinia might at this time have still been connected with Tunis, the
Straits of Messina must already have been formed--in other words,
Southern Italy and Sicily could no longer have been connected with one
another. This opinion is based upon the fact that in the upper strata
of the enormously thick Sicilian pliocene deposits are found a number of
arctic or subarctic species of mollusca which are entirely foreign to
the Mediterranean fauna. It is generally supposed that these reached the
Mediterranean area by the newly opened Straits of Gibraltar in later
pliocene times, and that the lower Sicilian deposits must therefore have
been laid down earlier. So far the deductions are perfectly correct, if
we assume the northern mollusca to have arrived in the Atlantic at the
time stated. However, they must have reached the Atlantic much
later--not till pleistocene times--if we adopt the above-stated
suggestions as to the age of the Forest-Bed (cf. p. 125). Moreover, the
great similarity between the faunas of Southern Spain and North-western
Africa indicate that the formation of the Straits of Gibraltar is of
very recent date. The northern mollusca, of course, could not have
reached Sicily till later. To suppose that the Sicilian deposits have
been uplifted 7000 feet since then is no doubt contrary to all our
geological teaching, but we must remember that this is altogether an
exceptional case. The area in question has probably ever since been in
the immediate neighbourhood of an active volcano, and the rate of the
uplift has therefore been immeasurably greater than at other localities
with which this one might be compared. The disconnection between Tunis,
Sicily, and Southern Italy was evidently produced by a subsidence of the
tract of land uniting these countries. If we suppose that this happened
in early pliocene times, we have either to take for granted that the
terrestrial fauna and flora of these countries are of miocene origin, or
that they were joined again during the Pleistocene Epoch. The range of a
very large number of animals and plants is such as can only be explained
by assuming that Tunis, Sicily, Sardinia, Corsica, and Southern Italy
were connected with one another. Of such extensive land-connections
subsequent to the arrival of the northern marine mollusca we possess,
however, no geological evidence whatsoever; and it is extremely
improbable that the land-areas which had sunk were once more raised
before again subsiding. The many animals whose presence in the
Mediterranean Region bears witness to these ancient land-connections
could not have arrived there in miocene times--in fact, they could
hardly have lived there before the end of the Pliocene Epoch. On the
other hand, it seems difficult to believe, once the Straits of Gibraltar
were open and the waters of the Atlantic able to enter the
Mediterranean, that the sunken parts between Sicily, Italy, and Tunis
could have been raised without affecting the entire area of that sea.
Nor is it likely that the junction between these countries could have
then been brought about by a general lowering of the Mediterranean
waters. As it may be asked what evidences we possess at all for the
supposition of such land-connections as I have indicated, also that
Southern Italy and Greece were connected, a few of the more salient
instances of distribution bearing on this problem may be of interest.

I have already referred to the occurrence of the remains of a small race
of Red Deer in the caves of Malta, similar to those still living in
North-west Africa, Corsica, and Sardinia. The Black-mouthed Weasel
(_Mustela boccamela_) inhabits Persia, Asia Minor, Greece, South Italy,
Sicily, and Sardinia, while _Mustela africana_ is found in Malta and
Algiers. The European Porcupine inhabits Asia Minor, the island of
Rhodos, Greece, Southern Italy, Sicily, North Africa, and Spain. Then we
have the Wild Sheep of Asia Minor, Cyprus, Sardinia, and Corsica, all of
which are closely allied. The small shrew-like _Crocidura etrusca_
occurs in South France, Italy, Sicily, and North Africa. Many other
mammalia might be quoted, but these are sufficient for our purpose.

There are a good many reptiles and amphibians with a similar
distribution. The European Chamæleon (_Chamæleon vulgaris_) has been
found in South Spain, North Africa, and Sicily. The Snake _Periops
hippocrepis_ is confined to Spain, Sardinia, and Greece. The worm-like
Lizard _Blanus cinereus_ inhabits some of the Greek islands, North
Africa, and Spain. Another Lizard belonging to the _Scincidæ_ has also
been found in some of the Greek islands, Sicily, Sardinia, Southern
Spain, and the Canary Islands. _Discoglossus pictus_--a toad--occurs in
Spain, North-west Africa, Malta, Sicily, Sardinia, and Corsica. A
variety of the Tree Frog (_Hyla arborea Savignyi_) is found in Europe
only in Corsica, Sardinia, and the Greek Archipelago.

Eight species of Reptiles and Amphibia--some of which I have just
referred to--are enumerated by Dr. Forsyth Major as occurring eastward
and westward of the Italian peninsula (and almost all also in North
Africa) without being known on the mainland of Italy. And in order to
show that Sardinia and Corsica are more closely related to North Africa
than to Italy, he indicates the general range of the Reptiles and
Amphibians found in these islands. Of the twenty-one species, only
twelve inhabit Italy, but at least sixteen North Africa and seventeen
Spain. Indeed, he shows that Corsica, Sardinia, Sicily, and North-west
Africa form a zoogeographical province, from which Italy, with the
exception of a few localities on its west coast, is excluded. It is a
remarkable fact that there are a few localities on the west coast of
Italy which in their fauna and flora exhibit closer relationship with
Corsica and Sardinia than with the mainland. Thus Dr. Major pointed out
that the _Catena Mettalifera_, the _Monte Argentario_, and _Monte
Circeo_ all belong to what we may call the former Tyrrhenian continent.
They are to be regarded as its eastern limits, which remained standing,
while the central portion--now occupied by the Tyrrhenian Sea--subsided,
and is at present covered by deep sea. Subsequently these remnants of
the old continent became joined with the newly-formed Italian
peninsula, but the plants and animals belonging to the older flora and
fauna were mostly destroyed by newer and more vigorous immigrants. A few
of the more hardy ones survived, and are a standing testimony of the
geographical revolutions of that part of Southern Europe.

That the Mediterranean area has undergone such profound geographical
changes as I have endeavoured to indicate is no new theory. Many
zoologists who have investigated the fauna of that region, and have
attempted to explain the faunistic relations, had to acknowledge that
the migrations must have taken place under geographical conditions
entirely different from those obtaining at present. Rütimeyer long ago
remarked that it seemed to him much more probable that Morocco, Algeria,
and Tunis were peopled by way of Gibraltar, and perhaps also by Sicily
and Malta from Europe, than Southern Europe from Africa. After careful
conchological researches in the Western Mediterranean region, Dr. Kobelt
came to the conclusion that formerly Southern Spain and Morocco must
have been united by a broad land-connection. Sicily and Algeria do not
apparently show any very intimate relationship conchologically, but
farther west--in the mountains of Tetuan--Dr. Kobelt discovered a colony
of Sicilian forms.[3]

"The close relationship," remarks Dr. Major (_a_, p. 106), "shown in
the fauna of Corsica and Sardinia to Africa, permits the supposition
that the connection with these islands had persisted to a much more
recent date than that with Europe."

Many other authors have pointed out the close similarity existing
between the faunas of Southern Europe and North Africa. We need only
refer to the writings of Professor Suess, Milne-Edwards, and Boyd
Dawkins. Mr. Blanchard went even so far as to say, "a comparer les
plantes et les animaux de la Sicile et de la Tunésie, on se croirait sur
le même terrain" (p. 1047).

No less than 113 species of phanerogamic plants are enumerated by
Professor Engler (p. 53) as occurring in the Mediterranean coast region
east and west of Italy without being found in that peninsula, or at
least only in the extreme south of it. But he tells us that these
species represent only a portion of such plants, which are extremely
numerous.

In taking a general survey of these plants, Professor Engler is of
opinion that their range implies that a large number of the
Mediterranean species have migrated along a line which can be drawn
between North Africa, Sicily, Greece, Crete, and Asia Minor, and that
from this line the distribution started northward again.

Many of these plants then, and also some of the animals I have referred
to, formed part of the older stream of migration which entered Europe
from Asia Minor (_vide_ Fig. 5, p. 117). There were only two courses
open to them as they arrived on our continent during earlier Tertiary
times. They could either go straight west towards Greece, or in a more
northward direction to the newly-formed Alps. As the latter were raised,
some of the immigrants were modified so as to adapt themselves to the
new surroundings. Others became extinct; but a great many have persisted
in the Alps to the present day and exhibit discontinuous distribution,
having meanwhile disappeared in the intermediate tract between the
latter and their original home in Asia. The lowlands of Eastern and
Central Europe were either occupied by the sea or by large freshwater
lakes, so as effectually to prevent a direct migration northward.

When the newer migrants arrived from Asia not only had the Alps risen to
a lofty mountain chain acting as an effectual barrier, but Southern
Italy and Greece had become disconnected. Some time after, Sicily and
Southern Italy also became separated. Meanwhile the stream of migrants
which consisted less and less of typically southern forms, emigrants
from Central Asia and even Southern Siberia, mingled with the southern
forms on their way to Europe, and these now poured across the newly
opened plain of Central and Northern Europe. But it was not until some
time after this that the Mediterranean Sea broke across the Ægean
region, and that the Northern Sea retired from the plains of Eastern
Russia to admit the typical Siberian fauna and flora into our continent
(_vide_ pp. 189-241).

I cannot close this chapter without referring to the active
distributional centre--or I might say, centre of origin--of species
situated in South-eastern Europe. No group of animals is more
instructive in elucidating the paths of migration from this centre than
the terrestrial mollusca. Wherever the original home of the genus
_Clausilia_ may have been in early Tertiary times, it is certain that
the most active centre of origin is now, and has been for a considerable
time past, in South-eastern Europe. One of the earliest migrants from
that modern centre of this interesting genus is _Clausilia bidentata_,
which is the only species found in Southern Spain, and one of the two
met with in Ireland, and which has been observed in high altitudes in
the Alps and in Scandinavia. As we go eastward from Western Europe the
number of species of _Clausilia_, as we have seen, increases until we
reach a maximum in the Balkan peninsula and the region of the Caucasus.
_Limax_, _Agriolimax_, and _Amalia_, three genera of slugs, likewise
appear to have originated in the same region and spread over Europe from
there. Some species like _Limax maximus_ and _L. marginatus_ are very
ancient, and probably commenced their wanderings in early Tertiary
times. In this manner many animals of European origin have joined the
Oriental migrants in their westward and also in their later northward
travels. In a similar way species of plants and animals of Alpine origin
might have joined these migrants in their northward course, and it is
only when we come to carefully analyse the constituent parts of all
these members which have come to us in England from the south, that we
realise the complexity of their origin. Finally, even the Siberian
migrants mingled with the later Oriental ones, and in some cases the
decision as to whether a certain species belongs to the former or to the
latter migration becomes a matter of great difficulty.


SUMMARY OF CHAPTER VI.

Like the last chapter, this deals with the Asiatic migrants. But while
the former described the history of the northern invasion, those animals
which entered Europe from the south-east are here more particularly
referred to. They originated in Central, Southern, and Western Asia. It
is not easy to discriminate in all cases between this Oriental migration
and the Siberian. To a certain extent, even an entry of Northern Asiatic
species has taken place by the southern route, and _vice versâ_. On the
other hand, southern species might have come to Europe by the southern
route--that is to say, to the south of the Caspian--and also by the
northern, which lay to the north of that great inland sea. The Red Deer
is a good example. It arrived on our continent by both routes. However,
there is a racial difference in the members of the two migrations. The
small race now found in Corsica, Sardinia, North-west Africa, and
Western Europe, is probably the older of the two, while the larger
one--resembling the American Wapiti Deer--arrived very much later from
Siberia.

The Mammoth, Wild Boar, Badger, the Dippers and Pheasants, are all
Oriental species which have come to us from the south-east; but there
are also Reptiles and Amphibians, and a host of Invertebrates. Not all
the animals, for instance, which have reached us in England from the
south-east are of Asiatic origin. There is an active centre of
distribution in South-eastern Europe itself, from which species radiate
out in all directions. This fact is well illustrated by the genus
_Clausilia_. Species from this centre, and also from the Alps, joined
the Oriental stream in their northward course.

In reviewing a number of instances of Oriental species in Europe, one is
struck by the peculiarity of their having apparently followed two
distinct routes. All entered from Asia Minor, which is proved to have
been connected with Greece until recent geological times. From here some
seem to have proceeded straight west, others northward. Further study
reveals the fact that the first route was followed by a much older set
of migrants at a time when the Mediterranean area was greatly different
from what it is at the present day. Greece was then joined to Southern
Italy, Sicily, and Tunis. The latter was also connected with Sardinia
and Corsica, and the Straits of Gibraltar did not exist. Under such
geographical conditions a direct migration on land from Southern Greece
to Spain was not only possible, but was actually undertaken by a very
large number of Oriental species.

FOOTNOTES:

[1] Since writing the above account, Mr. Boulenger, in his new work on
the Batrachia of Europe, has accepted the specific distinctions between
the two fire-toads.

[2] In some cases the accuracy of this view is proved by fossil
evidence, _Helix rotundata_, a common and widely spread British species,
having been found in miocene strata near Bordeaux.

[3] There are a great many instances of discontinuous distribution among
Oriental Invertebrates. Thus the Freshwater Crab (_Thelphusa
fluviatilis_) occurs in Southern Italy, Greece, Turkey, Cyprus, and Asia
Minor. Another crustacean--a Freshwater Crayfish--(_Hemicaridina
Desmaresti_) inhabits Spain, Corsica, Sardinia, Sicily, and Asia Minor.




CHAPTER VII.

THE LUSITANIAN FAUNA.


Under the Roman Emperor Augustus, the Spanish peninsula was divided into
three provinces, one of which--namely Lusitania--occupied a large
portion of the present area of Portugal. The term "Lusitanian" is
therefore almost synonymous with Portuguese, but it has frequently been
applied by zoologists and botanists in a much wider sense, so as to
vaguely include the extreme south-west of Europe without any definite
limits. Neither do I propose to restrict the term to everything found
within the borders of Portugal. For the sake of convenience, we may
designate as Lusitanian forms those animals and plants which have
migrated to Central, Southern, or Northern Europe from South-western
Europe. They may really be North-west African species, or they may have
originated on land which lay to the west of Portugal, and which is now
mostly buried beneath a deep sea. Nevertheless, we have received them
from the extreme south-western portion of our continent--they have come
to greater Europe from that direction.

In discussing the component elements of the British fauna and flora in
the third chapter, I have already referred to the distinguishing
characters of the Lusitanian migrants and to their distribution. I need
only repeat, therefore, that these are now principally confined to the
south-western portions of the British Islands. The late Edward Forbes
was the first to trace the Lusitanian flora to its native home. In his
classical memoir on the geological relations of the existing fauna and
flora of the British Isles, he laid the foundations of a new method of
research. We are as yet only beginning to realise the far-reaching
conclusions obtainable by a careful study of the geographical
distribution of animals and plants, though the lines of investigation
were indicated by him more than fifty years ago. Forbes was of opinion
that the Lusitanian element in the British flora was of miocene age, and
that it survived the Glacial period on a now sunken land to the
south-west of Ireland. Mr. Carpenter and myself agree in so far that we
are both inclined to look upon this Lusitanian flora and the
accompanying fauna in Ireland as of pre-glacial origin. But I am not
quite satisfied that the Lusitanian migration ceased to come north then.
It may have received a temporary check; but the presence, for instance,
of the Dartford Warbler (_Melizophilus undatus_) in the south-east of
England would seem to indicate that its northward migration took place
in very recent times. It is possible also that the very restricted
occurrence of the Dartford Warbler may imply that it is gradually
withdrawing towards its centre of origin from a former wider range. Such
an eventuality, as we have seen, has actually taken place in a great
number of instances.

It is not only in the British Islands that we perceive the influence of
the Lusitanian element. Scandinavia, Russia--indeed almost every part of
Europe--can boast of some migrants which have originated in
South-western Europe or on the mysterious lands which lay beyond it. As
a rule, however, we notice a marked decrease of Lusitanian species as we
travel eastward from Western Europe. Nevertheless, certain forms have
travelled far beyond the confines of our continent, and we certainly
meet with them in Asia and Northern Africa.

It is remarkable that we are apt to mistake sometimes for Lusitanian
migrants species which are of Oriental origin. In a previous paper I
classed such animals which had apparently originated in South-western
Europe, but had really come from Asia by a circuitous southern route,
with the Lusitanians. However, there is really no reason why the two
should not be kept apart, provided we can discriminate between the
pseudo-Lusitanians and the true ones. I have already indicated in the
last chapter how these pseudo-Lusitanian migrants originated.

Supposing an Oriental species had left Asia for Europe in miocene times,
it would on its arrival in Greece have had to decide between two
courses. It could either advance into the newly-formed Alpine peninsula
and there remain, or at once push on westward into Southern Italy,
Sicily, and Tunis, by means of the old land-connections, and thence into
Southern Spain. The Atlantic communicated at that time with the
Mediterranean across the valley of the Guadalquivir; but that connection
ceased to exist towards the end of the Miocene Epoch, when the Oriental
migrants were free to ramble through Spain and the whole of the North
European plain. I have indicated on a previous occasion (_a_, p. 484)
that the earliest members of the Red Deer migration, which have left
their traces in the caves of Malta, and whose descendants still live in
Corsica, Sardinia, and North Africa, may have found their way to
Northern Europe in this manner. Many other Asiatic mammals probably
reached the British Islands in a similar way.

I cannot call to mind any large species of mammal which we might
reasonably suppose to have originated in South-western Europe. Even
among the smaller ones, few give us any definite clue in this respect.
For instance, the present range of the genus _Myogale_--a small
Insectivore belonging to the Mole family (_Talpidæ_)--teaches us
nothing. The two living species show discontinuous distribution, and are
almost confined to Europe. _Myogale_ occurs fossil in French miocene
deposits, but is unknown beyond the confines of our continent. It is
therefore probably of West European origin. The gap between the South
Russian _M. moschata_ and the Spanish _M. pyrenaica_ is bridged over in
so far as we know from fossil evidence that the former had a much wider
range in pleistocene times, being then found in England, Belgium, and
Germany. _Talpa_, too,--to which genus our common Mole belongs,--seems
to be a West European genus, since it occurs in French miocene deposits.
However, it would be difficult to name many more recent genera which
could be included in the area which I propose to investigate in this
chapter. The genus _Lepus_ is probably not of Lusitanian origin, but the
sub-genus _Oryctolagus_--to which our common Rabbit belongs--has no
doubt had its original home in that region. Only two species of _Lepus_
(_Oryctolagus_) are known, one of which--_Lepus lacostei_--has been met
with in French pliocene deposits. The other is the Rabbit (_L.
cuniculus_). Though generally considered to have been introduced into
the British Islands, no reason can be brought forward in favour of such
a supposition, especially as it is known to have spread into Germany in
pleistocene times from South-western Europe. It occurs in France, the
Spanish peninsula, North-western Africa, and on some of the
Mediterranean islands. Its nearest living relatives, as we should almost
expect, are found in South America.

Of the Lusitanian Birds I have already mentioned the so-called Dartford
Warbler (_Melizophilus undatus_), which ranges from the south of England
to the extreme south-west of Europe. A second species occurs on the
Balearic Islands and on Corsica, Sardinia, and Sicily. The Andalusian
Bush-quail (_Turnix sylvatica_) is probably of North African origin,
and has subsequently spread into Southern Spain and Portugal, and
eastward as far as Sicily. It is an instance of a migrant utilising the
old Mediterranean land-connections in the opposite direction from that
described in the last chapter.

Two of our British Wagtails are very closely related, so much so that it
requires a very critical eye to distinguish them even at close range.
They also frequently interbreed. In their distribution, however, there
is a considerable difference between the White Wagtail (_Motacilla
alba_) and the Pied Wagtail (_M. lugubris_). While the former ranges
almost all over Europe and Asia, the latter is a local form resident in
the British Islands, Southern Scandinavia, and France, and a winter
visitor to Spain and North-west Africa. The genus _Motacilla_ is
probably Oriental in its origin, but it seems as if the Pied Wagtail was
a Lusitanian species which had gradually spread northward, only to
return to South-western Europe in severe weather for shelter.

The Bearded Titmouse (_Panurus biarmicus_)--the only representative of
the family _Panuridæ_--may possibly be a Lusitanian bird. The fact of
its being absent from Scandinavia and Northern Russia is suggestive of a
southern origin. It is doubtful whether the bird occurs on the south
side of the Mediterranean, but it is common in the south of France and
Spain, and has also been observed in Sicily, Greece, and Asia Minor. In
Central Europe it is found sparingly, and eastward its range extends as
far as Turkestan.

The genus _Fringilla_, which belongs to the great family of the Finches,
appears to be not only of European origin, but, if the range of the
species counts for anything, I should feel inclined to locate their home
in the south-west. Altogether, five species are known. One of them,
viz., _Fringilla teydea_, is confined to the Island of Teneriffe;
another, _F. madeirensis_, is found in Madeira, the Canaries, and the
Azores; a third, _F. spodiogenys_, inhabits North-west Africa. The two
remaining species have a much wider range. _F. cœlebs_--the common
Chaffinch--occurs in Europe, while its range extends eastward to Western
Siberia, Persia, and Turkestan. The other--_F. montifringilla_, known as
the Brambling--is more common in Northern Europe, and generally
frequents the more northern latitudes of Asia as far as Japan.

It might be urged that the peculiar little blue Magpie of
Spain--_Cyanopolius Cooki_--should find a place among the Lusitanian
species, since there is no bird like it anywhere else in Europe. But in
Eastern Siberia there lives a bird so closely allied as to be barely
distinguishable from it. Nevertheless, since there are some
distinguishing characters, it has received a distinct name--_C. cyanus_.
This is a most interesting and remarkable case of discontinuous
distribution, which may perhaps be explained by the supposition that the
genus is of Oriental origin, and has died out at its former
headquarters in Southern Asia and all along the line of migration,
except at the extreme limits of the range in both directions--east and
west.

As we go down in the scale of life--among the lower vertebrates and
invertebrates--we meet with a greater number of prominent members of the
Lusitanian migration. The Bullfinch, Dipper, and Chough, which might be
thought to be of Lusitanian origin, are, as I have shown in the last
chapter, Asiatic.

The European snakes seem to be all of eastern origin, unless
_Tropidonotus viperinus_ might be claimed as a Lusitanian form. Of very
great interest from a zoogeographical point of view is our only European
member of the South American and African family _Amphisbænidæ_. This
species--_Blanus cinereus_--is of the size and shape of an ordinary
earth-worm, from which, however, it may be distinguished by its
snake-like wriggling motions. It lives under stones in Spain and
Portugal, North-west Africa, and Greece. It has, therefore, a somewhat
similar distribution to that of many of the animals and plants referred
to in the last chapter. But here we have an animal which has evidently
utilised the old Mediterranean route described on p. 271, from west to
east. Two other species of _Blanus_ inhabit Asia Minor and Syria, but
most of its nearest relations either live in South America or tropical
Africa. In migrating to North and West Africa, its ancestors probably
made use of the land-bridge which spanned the Atlantic in early
Tertiary times. Another Lusitanian Lizard--belonging not to an aberrant
group, but to the typical Lacertidæ--is _Psammodromus hispanicus_. It is
rather variable in colour--generally of a brown or green--and grows to a
length at about four or five inches. It occurs throughout the Spanish
peninsula and also in Southern France. One of the handsomest European
Lizards, which reaches almost a foot in length,--of an olive colour with
greenish or mother-of-pearl reflection, and with two yellow stripes
along each side of the body,--is an allied species (_P. algirus_). From
the Spanish peninsula it passes into Southern France and North Africa.
Two other species of the genus are confined to North-west Africa.

It is quite possible that the genus _Pelobates_ is of south-western
origin. Of the two known species of this genus of Toads, one is found in
the Central European plain and the other on the Spanish peninsula and in
France. The closely allied _Pelodytes punctatus_, too, is confined to
this south-western district, and their nearest relations are found in
Mexico. Similarly, the genus to which the Midwife Toad (_Alytes
obstetricans_) belongs may have its original home in that part of
Europe. Of the two species, one is confined to France, Switzerland,
Belgium, and Western Germany, and the other, viz., _Alytes cisternasii_,
to Spain. _Discoglossus pictus_--a well-known and conspicuous Toad in
Southern Europe--inhabits Spain, Algiers, and Tunis, the islands of
Malta, Sicily, Sardinia, and Corsica. From the general range of the
family _Discoglossidæ_, as given in Mr. Boulenger's excellent catalogue,
it appears that nowhere in the vast space between China and New Zealand
has any member of the family been discovered. The peculiar genus of
Salamander--_Chioglossa_--is quite confined to the Spanish peninsula.

The Butterflies _Nemeobius lucina_ and _Charaxes jasius_ may also have
had their home in that south-western district. To this migration also
seems to belong the genus _Gonepteryx_, which has so peculiar a range in
the British Islands. The only British species, known as the Brimstone
Butterfly (_Gonepteryx rhamni_), occurs in the south of England and in
the south and west of Ireland. It is met with over the greater part of
Europe, and its range extends into Asia Minor and Northern India, and
then it reappears again in distinct varieties in Japan and the Amur
district. Three other species of _Gonepteryx_ are known from Tibet and
India, and one (_G. cleopatra_) from Southern Europe and Northern
Africa. All the remaining species inhabit the west, viz., Brazil,
Mexico, and Venezuela. That the genus has migrated from America eastward
to Europe appears to be more probable than a migration in the opposite
direction. At any rate, that an exchange of species between the
south-western portion of the Holarctic Region and the Neotropical area
took place is indicated by the fact, not only that a variety of _G.
cleopatra_ has been found in Madeira, but also that the Canary Islands
possess a distinct form of _Gonepteryx_, viz., _G. cleobule_.

Dr. Kobelt has given us such an exhaustive memoir on the characteristic
Mollusca of the different zoogeographical provinces of Europe, that we
are particularly well informed as regards that group of Invertebrates.
He tells us that the group _Torquilla_ of the genus _Pupa_--which is a
small chrysalis-like snail--is especially characteristic of the
Pyrenees, Spain, and Portugal. In a certain measure they replace there
the _Clausiliæ_ which, as we have seen in the last chapter, have come
from the east and are almost entirely absent in the south-west of
Europe. Of about seventy species of _Torquilla_, the larger number are
confined to this district, and some, which like _Pupa_ (_Torquilla_)
_granum_, range eastward, have travelled along the old Mediterranean
highway, _viâ_ Algiers, Sicily and Greece, to Asia Minor. They are still
found along the whole of this route.

Similarly, we are told by the same author, that _Gonostoma_--a group of
the large genus _Helix_--has a number of species in the same
south-western district, while only one, viz., _Helix obvoluta_, occurs
in England and Germany, and two in the Alps. Southward we again find
many representatives crossing over to North Africa, among which _Helix
lenticula_ has a similar range to _Pupa granum_, which I have just
referred to. The Alpine sub-genus _Campylaea_ is quite absent in the
Lusitanian district.

Among our own British testaceous Land Mollusca, several _Helices_,
viz., _Helix pisana_, _ericetorum_, _virgata_, _acuta_, _fusca_,
_rotundata_, _aculeata_, and probably many others, have come to us from
the south-west. The species of _Hyalinia_ are undoubtedly of very remote
origin, and it would be futile at the present state of our knowledge to
speculate as to their home. Some of our species may possibly be of
British origin. _Balea perversa_ is probably a south-western species,
and certainly _Pupa anglica_, which is quite confined to Western Europe.

[Illustration: Fig. 18.--The Spotted Slug (_Geomalacus maculosus_).]

Much more characteristic of South-western Europe, however, than these
land-shells are some of the slugs. The peculiar genus _Geomalacus_ is
almost entirely confined to Portugal. One species, which I have had
several occasions to refer to in illustration of the term "discontinuous
distribution," ranges far beyond the confines of that country. This is
_Geomalacus maculosus_ (Fig. 18), first discovered in the south-west of
Ireland, and more recently also in Portugal. Although careful search has
been made for it in other parts of the British Islands, this slug has
only been found in the portion of Ireland just indicated. Within the
last few years I have taken it, up to a height of over a thousand feet,
on the promontory north of the Kenmare River, also from sea-level up to
a considerable height near Glengariff, and more recently Messrs. Praeger
and Welch discovered it in abundance near the town of Kenmare. But
beyond this rather circumscribed area in the counties of Cork and Kerry
it does not occur (_vide_ Fig. 19). Several Portuguese species of this
interesting genus have since been added to science by Dr. Simroth and
others. Dr. Simroth, too, has promulgated the view that the genus
_Arion_--to which our common brown garden slug belongs--is of Lusitanian
origin. Indeed, the number of species of _Arion_ diminishes as we leave
that province, though one extends beyond the borders of Europe into
Siberia. The same number of species, viz. five, occur in Germany and in
England. _Testacella_--a slug-like mollusc--which lives underground on
earthworms, and of which genus three species, viz. _T. maugei_, _T.
haliotidea_, _T. scutulum_, are known to inhabit the British Islands, is
another Lusitanian animal. All the species are confined to Western
Europe and North Africa; they do not even reach Germany or Switzerland.

[Illustration: Fig. 19.--Map of the British Islands on which the
geographical distribution of _Geomalacus maculosus_ is indicated in
black.]

I have had occasion to mention once before an extremely interesting
genus of blind Woodlouse, viz., _Platyarthrus_. Like _Testacella_, it
lives underground, and also resembles it in its general range. Its
distribution is therefore of particular interest. It is difficult to
conceive that _Platyarthrus_, from its peculiar mode of life could have
crossed any formidable barrier, such as even a narrow straits of sea.
Its occurrence in Spain and North Africa indicates, therefore, that the
Straits of Gibraltar did not exist at the time when it undertook the
migration southward, just as the English Channel and the Irish Sea could
not have been there when it wandered to England and Ireland. The species
which occurs in the south of England has a wide range in Ireland, and
reaches in Scotland its most northern European limit of distribution.
_Platyarthrus_ is only one of the Lusitanian genera of woodlice. In
Ireland--chiefly on the west coast--we also find a brilliantly coloured
Woodlouse, which is absent from Great Britain, viz. _Metoponorthus
cingendus_. It reappears again on the Continent in the south of France.
Its range is therefore suggestive of a Lusitanian origin; and indeed,
when we examine the general distribution of the genus _Metoponorthus_,
we find that out of the forty-four known species, fully one-half are
confined to Western Europe and North Africa.

My friend and colleague, Mr. Carpenter, informs me that among the Irish
Spiders he is acquainted with, the following are to be looked upon as
Lusitanian species:--

  Dysdera crocota.
  Oonops pulcher.
  Tegenaria hibernica.
  Theridion aulicum.
  Lasæola inornata.
  Agroeca celans.
    do.   gracilipes.
  Teutana grossa.
  Cnephalocotes curtus.
  Porrhomma myops.

Of the _Coleoptera_, the genera _Trichis_, _Glycia_, and _Singilis_, all
belonging to the Running Beetles (_Carabidæ_), are almost confined to
the Spanish peninsula.

The beetles _Rhopalomesites Tardyi_, _Eurynebria complanata_, and
_Otiorrhynchus auropunctatus_ also belong to this fauna, as also the
Earthworms _Allolobophora veneta_ and _A. Georgii_, and the Millipede
_Polydesmus gallicus_.

It will be evident to every one from these few instances of Lusitanian
species, that somewhere in South-western Europe and North-western
Africa, and also, perhaps, in a larger now submerged western land-area,
there existed an active centre of development, from which animals spread
in all directions.

If the presence of _Platyarthrus_ in North-west Africa proves that the
Straits of Gibraltar had come into existence after its southward
migration, it also suggests that the ancestral home of this woodlouse
was in the Spanish peninsula. Whether this supposition is correct or
not, does not affect the Straits of Gibraltar problem, for in a
migration northward into Spain from Morocco a land-connection would be
equally necessary. Almost every group of vertebrates and invertebrates
furnishes instances of species which must have crossed the Straits on
dry land. Many naturalists have come to this conclusion, and have
clearly expressed their views on the subject. At the commencement of the
present period, says Mr. Bourguignat (p. 354), the north of Africa was a
peninsula of Spain, the Straits of Gibraltar did not exist, and the
Mediterranean communicated by the Sahara with the Atlantic.

The faunas of North-west Africa and the south-western portion of our
continent are so closely related, that an uninterrupted intercourse by
land must have existed for a very long period. The Mediterranean,
however, throughout the Tertiary period--at any rate since miocene
times--must have had almost constant communication with the Atlantic.
According to Professor Suess, this was the case. The Atlantic was joined
with the Mediterranean across the valley of the Guadalquivir during the
Miocene Epoch, so that Andalusia must have belonged to North Africa in
those days. The Straits of Gibraltar are supposed to have been formed in
the next epoch. I have already expressed my disagreement with that
theory from a zoogeographical point of view. The old Guadalquivir
connection probably persisted much longer,--though interrupted by
temporary periods of a partial retreat--so as to uncover sufficient land
to allow of an interchange during miocene as well as pliocene times
between the European and North African faunas. It is in this way,
perhaps, that some of the members of the Alpine fauna have reached Spain
by way of Corsica, Sardinia, and North-western Africa, and _vice versâ_.
The Balearic Islands were then connected with Spain; and we find there
many curious survivals which have long ago become extinct on the
mainland.

That the Straits of Gibraltar are only of recent formation has been
suggested on zoogeographical evidence by Bourguignat, Simroth, Kobelt,
and many others. Dr. Kobelt believes that the former land-connection
between the south of Spain and Morocco was much wider than is generally
assumed, and that the coast-line stretched from Oran in Algeria straight
across to Cartagena in Spain (_b_, ii., p. 228).

My allusions to the lands lying beyond the Lusitanian province, refer
chiefly to the Canary Islands and Madeira. Whatever doubts Dr. Wallace
had on the subject of their former connection with Morocco, it cannot be
denied that they used to be of much larger extent, especially in miocene
and pliocene times. It seems extremely probable that these islands
formed part of the mainland of North Africa until comparatively
recently, and that they are the last traces of a sunken continent which
united Africa and South America. A discussion of this problem, however,
must be deferred, as it is a complicated one, and one which would lead
me altogether outside the scope of this little volume. I hope I shall
have an opportunity to publish my views on this subject before long,
meanwhile the reader must content himself with this mere statement.

During the greater portion of the Miocene, and I think for part of the
Pliocene Epoch too, the advance of the Lusitanian species eastward was
barred on the continent of Europe by an arm of the sea which stretched
northward along the Rhone valley from the Mediterranean. The Lusitanian
forms which originated in Southern Spain were able to travel east during
these times by way of North-west Africa, Sicily, Southern Italy, and
Greece; it is possible that some may have reached the Alps in this
manner, and Eastern Europe generally. That the Lusitanian centre was
never a very active one compared with, for instance, the Oriental is
indicated by many distributional facts. It is difficult to understand,
however, why the Oriental species, on the whole, have migrated so far
west, while few Lusitanians have gone very far east. This seems to have
been noted particularly in the case of the flora. Mr. Bonnet drew
attention to the fact that in Tunis there are none of the absolutely
characteristic plants of Morocco and Spain, while the Oriental flora is
represented by a good many species. Lusitanian species have spread
chiefly southward into North Africa, and northward into France, the
British Islands, and even Scandinavia. As I have mentioned in the third
chapter, there are a good many species of Lusitanian origin in the
British Islands. However, we have only a mere remnant of what we ought
to have, had the climate been less trying. It is probable, too, that the
submergence destroyed a good many plants and the insects dependent on
them. That the Lusitanian fauna is very ancient in the British Islands
is proved by the fact of the discontinuous distribution of so many
species. A greater number survived in Ireland than in England.

[Illustration: Fig. 20.--The Strawberry-tree (_Arbutus unedo_) in its
native habitat in the south-west of Ireland. (From a photograph by
Robert Welch.)]

[Illustration: Fig. 21.--The Irish Spurge (_Euphorbia hiberna_) in its
native habitat in the south of Ireland. (From a photograph by Robert
Welch.)]

Altogether--and this was strongly urged by Edward Forbes--the Lusitanian
element is the oldest of the components of our fauna, and it must have
poured into the British Islands for many geological periods almost
without cessation. The same author, in his classic essay, refers
especially to the Lusitanian flora, two prominent members of which are
the British plants, _Arbutus unedo_ (Fig. 20, p. 305) and _Euphorbia
hiberna_ (Fig. 21, p. 306). The former has a wide range in the
Mediterranean region, and occurs in the British Islands only in the
south-west of Ireland. The Spurge, on the other hand, is also found in
the south-west of England, besides Ireland and Southern Europe.


SUMMARY OF CHAPTER VII.

The term "Lusitanian" is in this chapter employed in the wide sense, as
indicating the South-west of Europe and North-western Africa. From this
centre, and probably also from a now sunken land which lay to the west
of it, issued a fauna and flora of which we have abundant evidence in
our own islands, especially in Ireland. Edward Forbes held that the
Lusitanian element of the British flora was of miocene age, and that it
survived the Glacial period in this country.

At the time when the Straits of Gibraltar did not exist, and when there
was free land communication between Asia Minor, Greece, and Tunis, many
Oriental species migrated westward by this ancient Mediterranean route
as far as Spain. They would then have invaded the more central parts of
Europe from the south-west, without however being of Lusitanian origin.
Of the true Lusitanian mammals a typical example is the Rabbit. Then we
have a few birds and several interesting reptiles and amphibians. The
genus to which the Brimstone Butterfly belongs is also of south-western
origin. A number of Mollusca are mentioned which from their range
likewise indicate a Lusitanian origin. Most of our British Slugs and
many of our larger Snails belong to this group.

All these are merely a small remnant of what we received from
South-western Europe during the Miocene and Pliocene Epochs. But they
spread into many parts of Europe, and a few even crossed into Asia. The
antiquity of the Lusitanian element in our fauna is especially indicated
by the frequent recurrence of "discontinuous distribution" among the
species belonging to that section.




CHAPTER VIII.

THE ALPINE FAUNA.


We are told by Sir Archibald Geikie (p. 851) that "from the Pyrenees
eastwards, through the Alps and Apennines into Greece, and the southern
side of the Mediterranean basin, through the Carpathian Mountains and
the Balkan into Asia Minor, and thence through Persia and the heart of
Asia to the shores of China and Japan, a series of massive limestones
has been traced, which, from the abundance of their characteristic
foraminifera, have been called the Nummulitic Limestone. Unlike the
thin, soft, modern-looking, undisturbed beds of the Anglo-Parisian area,
these limestones attain a depth of sometimes several thousand feet of
hard, compact, sometimes crystalline rock, passing even into marble, and
they have been folded and fractured on such a colossal scale that their
strata have been heaved up into lofty mountain crests sometimes 10,000,
and in the Himalaya range more than 16,000 feet above the sea." "Nowhere
in Europe," continues the same author (p. 860), "do oligocene strata
play so important a part in the scenery of the land, or present on the
whole so interesting and full a picture of the state of Europe when
they were deposited, as in Switzerland. Rising into massive mountains,
as in the well-known Rigi and Rossberg, they attain a thickness of more
than 6000 feet." "By far the larger portion of these strata is of
lacustrine origin. They must have been formed in a large lake, the area
of which probably underwent gradual subsidence during the period of
deposition, until in Miocene times the sea once more overflowed the
area."

From these remarks by our most eminent British geologist, we gather that
in early Tertiary times much of the present area of Switzerland was
either a sea or a large freshwater lake. The Alps were then appearing in
this sea, probably as a chain of islands, and in the beginning of the
Miocene Epoch one large elongated island had made its appearance--the
future European Alps. I have already mentioned that the Miocene Sea
skirted the Alps from the Mediterranean up the valley of the Rhone and
along its northern and eastern margin. Miocene marine deposits are also
known from the Southern Alps and the east side of the Apennines, from
Corsica, Sardinia, and Malta. No trace, however, of them has been
noticed anywhere along the Ægean Sea or on the Balkan peninsula. The
Alps were therefore connected to the east with the outliers of the
Balkan Mountains, and in this way with Asia, from which they received so
large a proportion of their fauna and flora. In pliocene times the sea
still washed the southern shore of the Alps, but to the north dry land
gradually supplemented the sea, and the Alpine fauna and flora were
able to pour into the plain. It was then that the Arctic species--which
we have learned had migrated into Northern Europe from the north--found
their way to the Alps. In a similar way Lusitanian forms--in fact,
species from almost all parts of Europe--were now free to wander to the
newly opened up peninsula which had become part of the mainland of
Europe. The typical Siberian species had not entered our continent at
that time, it was not till much later--not until the middle of the
Pleistocene Epoch--that they made their appearance at the foot of the
Alps, but, as we shall see later on, it is doubtful whether many of
these species ever reached the mountains.

The fauna of the Alps, and also the flora, is therefore made up of a
number of component elements. In the first place we have the Oriental
element--the migrants from Central and Southern Asia. When the nature
and origin of the Oriental fauna in Europe was discussed, reference was
made to the fact (p. 272) that we can distinguish an older from a newer
Oriental migration. Both of these have entered the Alps. As we might
anticipate, many of the older Oriental migrants have developed into new
species, laying the foundation of an indigenous Alpine element. From the
fact that they set foot on the Alpine peninsula, it might be expected
that there could have existed no mountains to speak of. The climate was
mild and damp. Now as the country rose, and a formidable mountain range
took the place of a hilly island, the whole fauna was lifted up and
transferred to entirely different conditions. A modification of their
structure to suit the new surroundings was therefore to be anticipated,
and that is exactly what occurred, though not in all cases.

Take, for example, the goats which are of Asiatic origin. Every one has
heard of the "Steinbock,"--the Alpine mountain goat (_Capra
ibex_)--though very few have seen it in its native haunts, where it is
now on the verge of extinction. A closely allied species (_Capra
sibirica_) inhabits the Altaï and Himalayan Mountains; a third species
(_Capra sinaitica_) lives in Palestine, and has entered Egypt by way of
the Sinaitic peninsula. Another (_C. ægagrus_) occurs in Asia Minor,
Persia, the island of Crete, and some of the Cyclades. This exemplifies
what I remarked in the last chapter about the former land-connection
between Greece and the Asiatic continent. Finally, we have the Pyrenean
Goat (_Capra pyrenaica_), which is found in the Pyrenees, the higher
ranges of Central Spain, in Andalusia, and Portugal, thus indicating
that it probably reached the Spanish peninsula from the south by means
of the old Sicilo-Algerian highway, especially as remains of the species
occur in the cave deposits of Gibraltar. The ancestors of the goat-like
Antelope--known as the Chamois (_Rupicapra tragus_)--no doubt also came
from Asia. The genus is not represented there, but _Nemorhœdus_ and
_Budorcas_ are allied Asiatic genera, while the Rocky Mountain Goat
(_Haploceros montanus_) also has certain affinities with the Chamois.
Besides the Alps, the latter occurs in the Caucasus and the Pyrenees.
The Alpine Marmot (_Arctomys marmotta_) is sometimes quoted as owing its
origin to the Siberian pleistocene migration, but it does not occur in
Siberia now, nor is there any palæontological evidence that it was ever
found there. The genus _Arctomys_ is an ancient Asiatic genus, to judge
from its general range. Only two species occur in Europe, one of which,
the true Siberian Marmot (_A. bobac_), just enters our continent in the
east--or rather, it is one of those species which came to us in
pleistocene times and are now gradually retreating towards their native
land. The genus, however, is probably not of Siberian origin. No less
than seven other species occur in Asia, six of which are confined to
Central Asia and the Himalayan Mountains, while four have wandered to
North America. The sequence of events, therefore, was that the ancestor
of _Arctomys marmotta_ probably came to the Alps direct from Central
Asia by way of Asia Minor in miocene or pliocene times. It has since
become modified into a distinct species, and has spread to the European
plain, where it occurs fossil in pleistocene strata, and to the
Carpathian Mountains and the Pyrenees.

The great majority of species of the large genus _Microtus_ (_Arvicola_)
are Asiatic, and there can be little doubt that it has originated in
that continent. There is one species of Vole (_Microtus nivalis_) which
occurs in the high Alps, and which has been supposed to be a typical
Alpine form. It is known, however, to occur also in North Italy and in
Bohemia, while _Microtus leucurus_ of the Pyrenees is identical with
this species. But its range is by no means confined to Europe, for it
has also been discovered in Syria and Palestine, while a closely allied
form exists in the Himalayan Mountains. This shows clearly that the
species has migrated to the Alps from Asia Minor. That this migration
may have taken place at an early period--at a time when Sardinia and
Corsica were still connected with Southern Europe--is indicated by the
occurrence of an extinct Vole (_Microtus brecciensis_) in Sardinian and
Corsican pleistocene (?) deposits.

All the Alpine species mentioned except the Chamois can be easily traced
to their former Asiatic home. But even it has its nearest relations in
Asia. I might also refer to another Vole (_Evotomys Nageri_) which is
practically confined to the Alps and Northern Italy, and which has
probably originated there, though most of its nearest relations are
either Asiatic or North American species.

But besides these Asiatic immigrants and their modified descendants we
have a small truly native Alpine mammalian fauna. _Sorex alpinus_--the
Alpine Shrew--occurs only in the Alps, the Harz Mountains, Pyrenees, and
Carpathians. The genus has been found in European eocene strata,--in
vastly older deposits in our own continent than elsewhere,--so that it
is extremely probable that it has originated there. It may then have
developed a new centre of distribution in the newly-formed Alps where
both _Sorex alpinus_ and _S. minutus_ (_pygmæus_) have their home. From
there they again spread--perhaps already in miocene times--to Asia and
North America, where a large number of new species originated. It seems
to me even probable that one of these Asiatic species of _Sorex_, viz.
_S. araneus_ (_vulgaris_), subsequently migrated towards the old home of
its forefathers, since we find it more or less confined to Central and
Northern Asia and Northern Europe.

Though the origin of the Alpine Hare has already been referred to and
fully discussed in a previous chapter (p. 148), the conclusions arrived
at may be once more repeated. The Alpine Hare (_Lepus variabilis_) is of
Arctic origin. It spread southward into Europe, North America, and Asia
in early glacial times, and reached our continent from Spitsbergen by
means of a direct land-connection with Lapland. The Scandinavian
peninsula was then separated from Russia, but connected with Scotland
and Ireland (Fig. 13, p. 170). Since England was then united to France,
the Alpine Hare was able to invade western continental Europe and all
the mountain ranges. Its range is very discontinuous, small colonies
being scattered all over the mountainous parts of the Northern
Hemisphere, while the European Hare--a closely allied species--occurs in
the plain, and now occupies to some extent the former haunts of the
Alpine Hare (cf. Fig. 8, p. 137). Might not the European Hare, as
suggested, possess some advantages which enabled it to drive the other
into more inaccessible parts, thus producing the peculiarity of range?
The present distribution of the Alpine and the European Hare (_L.
Europæus_) appears to me to strongly support such an assumption. It is
not the cold which has driven the Alpine Hare to the Alps; and its
presence there is not, as is often supposed, a "_standing testimony of a
former arctic climate_" in Europe, but merely the necessary consequence
of the weaker species being thrust into less accessible regions by a
stronger rival.

_Muscardinus avellanarius_,--the common Dormouse,--though by no means
confined to the Alps, has probably originated there. It is found up to a
height of nearly 5000 feet in these mountains, and is spread over Europe
at nearly equal distances from the Alps in all directions. Being absent
from Ireland, Scotland, Norway, and Northern Russia, it seems as if it
had only diffused northward in more recent times.

The closely allied genus _Myoxus_ is likewise of European extraction,
some species being known from French eocene deposits.

There are only a few typically Alpine Birds. One of these is the Alpine
Accentor (_Accentor collaris_), which on rare occasions visits England,
and Northern Europe generally. It is, however, by no means peculiar to
the European Alps; a variety of this species occurs in Central Asia,
Eastern Siberia, and Japan. The only other Accentor inhabiting our
continent is the Hedge Accentor (_A. modularis_), which is resident over
the greater part of it, and also in North Africa and the Mediterranean
Islands. It also extends its range across the Ægean Sea to Asia Minor,
so that really not a single Accentor is peculiar to Europe.

Both the European species are evidently old forms, and the genus, as
might be expected, is certainly Asiatic. No less than ten other species
of Accentor are known, all of which are confined to Central Asia and the
Himalayan Mountains, and are therefore all Holarctic. I may mention that
much difference of opinion still exists as to the true zoological
position of this anomalous genus. It has been located in several
different families by various ornithologists, but has not yet found a
permanent resting-place. Another bird generally considered to be
peculiar to Switzerland is the Alpine Chough (_Pyrrhocorax alpinus_),
but its range extends across Asia Minor to the Himalayas. Whether the
European Chough should not form a distinct genus is a matter of opinion.
Some of our leading ornithologists, like Dr. B. Sharpe, are inclined to
separate it from _Pyrrhocorax_; however, there is no doubt that it is
closely related to the Alpine Chough, whatever view we may take of the
generic distinctness. It inhabits principally Western and Southern
Europe, also North Africa; and its range extends eastward to the
Himalayas, China, and Eastern Siberia. If any doubt still existed as to
the Asiatic origin of the Choughs, it may be noted that the only two
other closely allied genera, viz., _Corcorax_ and _Podoces_, live in
Australia and Central Asia respectively.

There are two other birds to which I should like to refer. These are the
Rock Sparrow and the Alpine Snow Finch. The first of these (_Petronia
stulta_) is by no means peculiar to the Alps. It is the only species of
the genus inhabiting Europe; and besides the Alps it occurs in Southern
Europe generally, and ranges as far west as the Canaries and Madeira.
Eastward it is not found beyond Central Asia. Of the remaining five
species of _Petronia_, two occur in Asia (including India) and three in
Africa. Whether the genus is African or Asiatic is immaterial for our
purpose, since, in any case, the only European species came to us from
the east with the Oriental migration. The distribution of the Alpine
Snow Finch (_Montifringilla nivalis_) is very similar to that of the
birds we have just been considering. It inhabits the Alps up to a great
height, but occurs also on the Pyrenees and other South European
mountain ranges as far east as Palestine, where again it is found in the
Lebanon. The genus _Montifringilla_ has seventeen other species. Twelve
of these live in Central Asia and Japan, extending as far north as
Kamtchatka, while five inhabit Western North America right down to
Mexico. There is every probability that in this case also we have to
deal with an Asiatic genus which spread eastward to America, and
westward to Europe.

As regards the Reptiles, there are _no_ peculiar Alpine forms, but among
the Amphibia some species deserve to be mentioned. Up to an elevation of
10,000 feet we find in the Alps the Black Salamander (_Salamandra
atra_); and it is apparently quite peculiar to them, never having been
observed in the plains. The handsome black and yellow Salamander
(_Salamandra maculosa_)--so well known as a terrarium specimen--likewise
occurs in the Alps, and it has besides a fairly wide distribution in
Europe. It is known from Southern Germany, the Pyrenees, Spain,
Portugal, Sardinia, Corsica, Greece, Syria, and Algiers. A third species
(_S. caucasica_) inhabits the Caucasus. The evidence of distribution
here points emphatically to an Alpine origin of the genus _Salamandra_.
We cannot tell where the ancestors of _Salamandra_ may have come from,
but several other genera of _Salamandridæ_ are certainly Asiatic. Our
common Newt (_Molge vulgaris_) belongs to a genus with nineteen species,
several of which are peculiar to Europe. The general range of the genus,
however, extends to North America, and it is more probable therefore
that it originated in Asia. If so, it certainly must have passed into
Europe at a very early date. Let us assume the first _Molges_ to have
traversed the Ægean Sea on _terra firma_ to Greece in miocene times,
they might thus have been able to travel straight on to the old
Tyrrhenian continent of which Corsica and Sardinia now form the
remains, and also on to North-west Africa. Indeed, we find high up in
the Corsican mountains an interesting large brownish-grey Newt (_Molge
montana_), and another in Sardinia (_Molge Rusconii_). Again, in Algiers
there are two species, viz., _Molge Poireti_ and _M. Hagenmülleri_,
while the Moroccan _M. Waltlii_ passes into the south of Spain. Here
_Molge boscæ_, _M. aspera_, and _M. marmorata_ originated, the latter
passing into France.

Another branch of the _Molge_ tribe turned northward from Greece towards
the newly forming Alps; and there originated _Molge alpestris_ and _M.
palmata_, which more recently have spread into England (one at least),
Germany, France, Austria, and Southern Italy. _Molge vulgaris_ is an
Asiatic species which wandered northward after entering Europe, covering
a large area, but never reached the extreme south or south-west. _M.
cristata_--the large Water Newt--has a similar but not quite so extended
a range, while _M. vittata_ never managed to cross the borders of Asia
Minor. Some of the other species occur in China, Japan, and North
America.

None of the tailless Batrachians--the Frogs and Toads--are peculiar to
the Alps, but one, viz. _Rana temporaria_, ascends to the height of no
less than 10,000 feet. It is our common British Frog. No other Frog
probably ranges so far north or to such heights.

Let us now inquire what the invertebrate fauna of the Alps teaches us.
We are told by Dr. Kobelt, the great authority on European land shells,
that a uniformity of character marks the Alpine Molluscan fauna (_b_,
i., p. 251). One of the characteristic genera _Campylaea_--often looked
upon as a sub-genus of _Helix_--is a group containing somewhat flattened
conspicuous snails of large size. These are found everywhere in the
Alps, and wherever they occur beyond the confines of these mountains,
remarks Dr. Kobelt, their origin from the main stock is easily traced.
They have been gathered in the Apennines in Sicily, and even beyond the
Mediterranean in Algeria. On the Balkan peninsula they occur right down
to the most southern point of Greece, but are not met with either in
Crete or Asia Minor. One species has been found sub-fossil in Thuringia
in Northern Germany.

Another truly Alpine genus, says Dr. Kobelt, is the operculate
_Pomatias_, which in its geographical distribution offers some
interesting modifications from that of _Campylaea_. Less limited to high
elevations, it has spread over a greater part of the plains. This has
happened especially in France, while in Germany one species advances
almost as far north as Heidelberg. In other directions also the genus
has travelled beyond the limits of range of _Campylaea_. _Pomatias_
occurs in the Pyrenees and Northern Spain, in Sardinia and Crete, and
may, according to the same author, be expected in Asia Minor, although
no species has as yet been met with there. In Greece, again, it has been
observed, and numerous species inhabit Tunis and Algeria. Dr. Kobelt
connects the wider range of _Pomatias_ with the geological history of
the genus (_b_, i., p. 253). He tells us that species of Pomatias have
been found in eocene deposits differing but little from our present
forms, while undoubted _Campylaeæ_ are not met with till we reach the
upper Miocene.

_Zonites_ is, according to Dr. Kobelt, a third Alpine genus, whose range
scarcely differs from the other two (_b_, i., p. 254). The centre of
distribution lies at present in one of the branches of the most southern
Alpine chain which help to form a large portion of the Balkan peninsula.
The bulk of the species inhabit that peninsula, the Greek Islands
(except Crete) and Asia Minor. Neither in the Tyrol nor in Switzerland
do we find any _Zonites_, and the few species that do occur in the
south-eastern Alps only just cross the outliers of these mountains.
Between the south-western Alps and the Rhone we again find a
_Zonites_--a remarkable case of discontinuous distribution, since the
nearest other habitat of the genus is Monte Gargano in South-eastern
Italy, which is known to harbour a good many interesting geographical
puzzles.

We still have a good deal to learn as regards the molluscan fauna of
Sicily, Sardinia, and Corsica. These islands have scarcely been more
than skimmed by conchologists, and _Zonites_ may inhabit one or all of
these, which might indicate to us the manner in which this genus
travelled from Southern Italy to Provence in the south of France. The
distribution of _Zonites_ certainly does not seem to imply an Alpine
origin, because it is almost completely absent from the Alps proper.
But I do not think my views differ materially from those of Dr. Kobelt,
since the Alps, in the wide sense, include the mountains of the Balkan
peninsula, where I should feel inclined to locate the ancestral home of
the genus.

The small operculate genus _Acme_ is a similar case. Dr. Kobelt places
the centre of distribution on the southern slope of the Alps, but
scarcely any of the species inhabit the Alps proper. Some occur in
France, others in North Africa, Sicily, Southern Italy, and the
Caucasus. It is evidently a very ancient genus. The species live in moss
or underground, and are not likely to be transported across the sea by
accidental or occasional means of distribution.

Still another genus, which resembles _Acme_ in its geographical
distribution, is _Daudebardia_--a small slug-like mollusc with a tiny
shell. It does not, however, range nearly so far north or west as
_Acme_, for it occurs neither in the British Islands nor in Spain or the
Pyrenees.

I shall not be able to refer to more than a few of the most typical
Alpine species of Lepidoptera, but they may be taken as fair examples of
the geographical distribution of the rest of the group.

Even those visitors to Switzerland who do not claim to be naturalists
have heard of the remarkably handsome and stately Butterfly known as
Apollo. To the ardent entomologist, the first sight of this typical
Alpine species is a never-to-be-forgotten delight, and he generally
brings home with him a rich harvest of specimens. The more experienced
Butterfly hunter knows that there are no less than three different kinds
of Apollo--or, as we should say more correctly, of Parnassius--in
Switzerland. There is first the common Apollo (_Parnassius Apollo_),
then the rarer and more local _P. delius_, which inhabits more elevated
regions, and finally the still scarcer _P. mnemosyne_, which is only
known from the highest mountain ranges. It may be a surprise to those
who have accustomed themselves to connect Apollo with the Alps, and who
think the two belong together and cannot do without one another, to hear
that it is by no means confined to them. It is also found in
Scandinavia, France, Spain, Russia, and in Siberia. _Parnassius delius_
is confined to the European Alps and the mountains of Central Asia,
while _P. mnemosyne_ is known from the Pyrenees, Sweden, Hungary,
Sicily, Russia, and Western Asia. One other Parnassius inhabits Europe,
viz., _P. Nordmanni_ of the Caucasus, but all the remaining species of
the genus--and there are nearly thirty more--are confined to Central
Asia. A few, as we have seen, have reached Europe, some have travelled
to the Himalayan Mountains, and others to Western North America. The
centre of distribution is certainly in Central Asia, and we have no
reason to suppose that the original home in this case does not agree
with that centre.

_Melitæa_, a genus to which some of our British Fritillaries belong, has
also some typically Alpine members. Two of these, viz. _M. cynthia_ and
_M. asteria_, are peculiar to the Alps, the latter being only found at
considerable elevations. Most of the remaining fourteen European species
are also found in Central Asia. Thus the isolated _M. maturna_, which in
Europe is confined to Lapland, is also known from the Altaï Mountains,
which again are near the centre of distribution, since some species of
_Melitæa_ range across the Northern Pacific to Western North America.

The small British Mountain Ringlet, and also the Scotch Argus, belong to
a genus of butterflies which is very characteristic of the European
Alps. But owing to its enormous geographical distribution, its probable
home is somewhat difficult to ascertain. Nevertheless it is a noteworthy
genus, especially so from the fact that the two British species _Erebia
epiphron_ and _E. æthiops_ are taken at first sight for true Arctic
migrants. As neither of them, however, occurs in Scandinavia, Greenland,
or Arctic America, this supposition must be abandoned. They must be
looked upon as species which once had a wider range in the southern
parts of the British Islands, and which have survived in a few isolated
localities, where they are apparently on the verge of extinction.

About sixty species of _Erebia_ are known to science, half of which are
found in Europe, the remainder in Siberia, the Himalayas, Arctic
America, Chili, Patagonia, South Africa, and Madagascar. Though a few do
range into these outlying regions of the earth, Central Asia seems to
lie near the centre of distribution of the genus, and the probability is
that it also was its original home. Most of the European species are
high Alpine forms--_E. glacialis_ being met with at a height of 10,000
feet--and these are generally quite peculiar to the Alps, showing that
their ancestors came from Asia at an early date, probably by way of Asia
Minor and Greece. A few, as for instance _E. lappona_, range right
across to the Altaï Mountains from the Alps, and at least one--_E.
melas_--is found in Greece. _Erebia_ migrations seem therefore to have
taken place by the Southern or Oriental route at different geological
periods. But some of the European species which are more or less
confined to the plain, and are either absent from Switzerland or do not
reach the higher elevations, appear to me to have come by the more
direct northern or Siberian highway, at a still more recent period.
These are _Erebia æthiops_, _medusa_, _ligea_, and _ambla_.

Only one species of the well-known Polar genus _Œneis_, viz. _Œ.
aëllo_ occurs in the Alps. It has always been taken at very high
elevations near the verge of the snow-line on the most lofty parts of
the Simplon Pass, and other similar situations. Altogether about a
dozen species of this genus of butterfly are known, most of which are
confined to the polar regions of the Old World and the New, though some
have found their way to the extreme south end of South America, in what
manner is still a mystery. Like the preceding genera, this also appears
to have emerged from Central Asia. The genus, too, is closely allied to
the last, and though its range is not quite so extensive, it resembles
it in many respects. The Alpine species of _Œneis_ came to Europe by
the Oriental route. But the Lapland species--at any rate _Œ. jutta_
and _Œ. bore_--have taken a somewhat circuitous route to reach our
continent. They first migrated from Asia to North America, and then by
the old land-connections by way of Greenland to Lapland. It is
noteworthy that Professor Engler felt convinced (cf. p. 171) that the
occurrence of many of the Arctic plants in North Scandinavia and Siberia
could be best explained by the assumption of such a migration from Asia
_viâ_ North America to Europe rather than by the shorter route.

There are far more Alpine beetles than butterflies, but their
geographical distribution is less well known, and it is therefore not at
all safe to base important conclusions as to the origin of a fauna on
that group alone; however, as far as my limited knowledge of the
_Coleoptera_ of the Alps goes, their general range seems to agree
perfectly with other orders of insects. Many can also be traced to an
Asiatic home, and the route they came by is the Oriental and not what I
have called the Siberian.

Take, for instance, the genus _Nebria_, of which we have one species in
England--a black insect with a bright reddish-yellow border and long
light legs--known as _N. livida_. There are about eighty European
species, most of which are confined to the Alps, the Caucasus, the
Pyrenees, Spain, and Greece. The genus, however, ranges all over the
Holarctic Region, that is to say roughly, over Europe, Central and
Northern Asia, and North America. The centre of distribution lies in
Central Asia. If the genus had poured into Europe by the northern or
Siberian route, we should probably now find many species in Northern
Russia, Germany, and France; but this is not the case, and we may
therefore assume with some justification that the Southern or Oriental
route was the only one available at the time when the bulk of the
species of _Nebria_ wandered to Europe. Many of the _Nebrias_ occur in
Switzerland and in the Alps, generally on the margins of the snow-fields
and glaciers, like _N. Germari_ and _Brunii_. Others, for example, _N.
atrata_, ascend to the highest limit of animal life, having been
observed at a height of over 10,000 feet.

Of the remaining orders of insects we know as yet very little. Central
Asia and even Siberia are only beginning to be explored, and their
invertebrate fauna--except _Lepidoptera_ and _Coleoptera_--is
practically unknown. However, I cannot conclude this short summary of
some of the more characteristic Alpine animals without referring to the
Grasshoppers which are so conspicuous in the mountains. The mountain air
simply rings during a bright summer's day with the loud and cheerful
song of millions of these insects. It is one of the most vivid
impressions a tourist brings back from Switzerland--this constant shrill
sound issuing from an apparently invisible source.

Among these Grasshoppers there are some highly characteristic Alpine
genera. _Pezotettix_--formerly known as _Podisma_--is one of these. _P.
alpinus_ is almost confined to the high Alps; with _P. mendax_ it occurs
in lower levels chiefly towards the south-east, that is to say, in the
direction of Hungary, Servia, and Dalmatia. _P. frigidus_ occurs not
only in the high Alps, but also in Lapland. _P. Schmidti_ and _P.
salamandra_ are found in Carinthia, Servia, and Transylvania; and one
species also inhabits the Pyrenees and another the Italian Mountains.
Finally, the only English species of _Pezotettix_, viz. _P. pedestris_,
has been taken in Sweden, Denmark, and then again in Austria, Hungary,
Servia, etc., as far east as the Volga, and also on the high Alps, in
Sardinia and the Abruzzi Mountains in Italy.

Very little, as I remarked, is known of the Asiatic range of this genus,
but either the same or a closely allied one has many representatives in
North and South America. Whether _Pezotettix_ is therefore of Asiatic
origin we cannot positively affirm, but whatever view we take, the
general range of the European species indicates that the migration took
place from the Alps in a south-easterly direction, or to them in a
north-westerly one. That is to say the Oriental route, and not the
Siberian, was utilised by the migrants.

Fortunately, we know a little more about another Grasshopper genus,
called _Chrysochraon_. There are only two species, one of which, _Chr.
dispar_, has been found from Northern France to the mountains of Servia,
but not in the Alps. The other, _Chr. brachypterus_, has a somewhat
similar range in the plain; but, moreover, it inhabits the Alps up to a
considerable height. It is interesting to note that both these
Grasshoppers again turn up on the Amur in Eastern Siberia.

In conclusion, I might mention one more Grasshopper, viz. _Tettix_,
because it includes a species--_T. bipunctatus_--which, though well
known in the plain of Middle and North Europe, ascends the Alps to a
height of nearly 10,000 feet. It is one of the few instances I know of
an animal occurring in the same form in such an enormous range of
altitude--from sea-level to the highest regions where animal life is
known to exist. It is also known from Asia Minor and Siberia. _T.
subulatus_ has a similar distribution, but is more common in Southern
Europe than the other. _T. fuliginosus_ occurs in Lapland and Siberia,
_T. meridionalis_ and _T. depressus_ all along the shores of the
Mediterranean. There can be no doubt that here also we can trace
migration to or from Siberia, and again, as on previous occasions, by
the Oriental route.

We now possess a fair general idea of the fauna of the Alps. We have
learned that a good many of the animals are indigenous, and that others
have migrated to the Alps by various routes. The majority of these have
come from Central and Southern Asia with what has been described as the
Oriental migration. A much smaller number have reached the Alps from the
north and the west, but none of the latter are among the high Alpine
forms. What will be the most surprising revelation is that the eastern
species, which arrived in Europe with the Siberian migration, are
practically absent from the Alps proper. No doubt some of them still
survive in the lowlands of Switzerland and the Tyrol, but none of the
true Alpine fauna owes its origin to the Siberian migration. If we
compare the Alpine mammals with the Siberian forms which reached England
(_vide_ p. 202), we at once perceive the difference. We should expect to
find in the Alps--if not the Reindeer and the Glutton--the Arctic Fox,
the little Pica, the Lemmings, and the pouched Marmots. It might be
urged that some of the smaller Siberian carnivores and rodents do
inhabit the Alps. So they do. The Stoat and Weasel have found such a
congenial home in Europe, both in the plain and mountains, that they
have spread rapidly to the latter, and no doubt reached within a
comparatively short time the great heights at which they now occur in
the Alps. But the Voles (_Arvicola_) have scarcely spread beyond the
region of fields and cultivated ground. A height of 5000 feet at the
most marks their maximum altitude in the Alps.

The fauna which reached the Alps in miocene and pliocene times, as well
as the indigenous element, must have survived the Glacial period in
their mountain home. Though I think that the conditions of the climate
at that time and the size of the Scandinavian glaciers have been greatly
exaggerated, there can be no doubt at all about the enormous size of
many of the Alpine glaciers at this period. The climate was probably
much moister but not colder than what it is now, possibly warmer. The
snowfall was therefore greater, so that glaciers filled many of the
lower valleys of Switzerland which are now quite free from ice, and even
invaded the plain. But there is no reason whatsoever why the Alps should
not even then have supported a luxuriant fauna and flora as they do now.
Possibly many of the miocene plants and animals became extinct then, but
extinction of species occurs at the present day. We hear complaints that
the Chamois and the Steinbock have nearly vanished; we know that the
Marmot is now much scarcer than it used to be, and that the Edelweiss
and many other plants are more and more difficult to find, and seem
rapidly to disappear. No doubt all this is in a great measure due to
the influence of man, but not altogether. There is a constant struggle
for existence going on among the animals and plants themselves--the
stronger and fitter species driving the less fit and weaker into a
corner, where they finally succumb. This happens now just as it did in
pliocene and pleistocene times, and need not imply change of climate.

As soon as the Miocene sea to the north of the mountains had retreated,
a portion of the Alpine fauna poured into the plain, and many species
have found their way to the British Islands, a few to Scandinavia and
Russia. Westward too, the sea soon after retired and opened a way for
those Alpine species which were vigorous enough to extend their range in
that direction. South-eastward, of course, a highway had long ago been
open, and Alpine forms which were able to migrate towards the incoming
Oriental stream, had no difficulty in doing so. When they arrived in
Greece, some turned westward again and populated Sicily, Southern Italy,
Sardinia, Corsica, and Northern Africa, while others crossed over to
Asia Minor, which was then connected with Greece, and wandered towards
the Central Asiatic or the Himalayan Mountains.

But, as I remarked, few of the typical Alpine species reached
Scandinavia and Lapland. I have already referred to the similarity
between the Northern Scandinavian and the Alpine faunas in a previous
chapter, and I have shown that this resemblance cannot altogether be
explained by the supposition of an interchange in the faunas of the two
regions. That this has taken place to some extent is probable, but the
resemblance appears more especially due to the fact that the Alps and
Scandinavia have been peopled from the same centres of distribution.

In order to make this matter quite clear, I will give a familiar example
as an instance of the manner in which the present distribution can be
explained without taking recourse to direct migration from the Alps to
Scandinavia or _vice versâ_. The example I will take is that of a family
of birds, not only of extreme interest from the fact of its northern
range, but also from the pleasure it gives to those addicted to sport.
This is the grouse family, the _Tetraonidæ_.

Let us commence with our British Grouse (_Lagopus scoticus_), which is
peculiar to the British Islands. In Norway we find a Grouse (_L. albus_)
which differs in habit, and in the fact of its turning white in winter;
otherwise it is so closely allied to our Grouse that many ornithologists
do not separate them specifically. No doubt the British Grouse is a
descendant of this Scandinavian Willow-grouse. The latter is known also
to inhabit Greenland and Arctic North America, and it is even found
beyond Behring Straits in Northern Siberia. _En route_ between
Scandinavia and Asia, travelling in a westward direction, we meet with
two other very local species of Grouse, which may be looked upon as
offshoots of _L. rupestris_--viz., _L. hyperboreus_ of Spitsbergen, and
_leucurus_ of Western North America. In Asia we then again find two
kinds of Grouse, very closely related, and by some indeed regarded as
belonging to the same species. These are _L. rupestris_ and _L. mutus_.
Mr. Ogilvie-Grant tells us of the former (p. 49), that it is merely a
more northern rufous form of _L. mutus_, and that it goes through
similar changes of plumage. In summer the males are readily
distinguishable, but in winter it is impossible to tell one from the
other. "_L. rupestris_ taken as a whole," says Mr. Ogilvie-Grant,
"appears to us barely specifically distinct from _L. mutus_." _L.
rupestris_ occurs not only in Northern Asia, but crosses the Behring
Straits to Arctic America, being still found on the Aleutian Islands,
which represent the last remains of the former land-bridge between Asia
and North America, then eastward to Greenland and Iceland. However,
while this form does not cross the confines of Asia in a westerly
direction, its near relative _L. mutus_--better known as the
Ptarmigan--does; and may perhaps have entered Europe as a Siberian and
also as an Arctic migrant. It is still found in the Ural Mountains, in
Finland, and the highlands of Scandinavia. It is gradually being driven
out of the Alpine lowlands, while it has long ago disappeared from
Germany, France, and Austria--in fact, from all the lowlands of Europe.
It has also been met with in the Pyrenees and in some of the Spanish
mountains. Similarly, the bird has become extinct in England and
Ireland, while it is becoming more and more scarce in Scotland. The
centre of distribution of the genus lies in Arctic America, and from
there the genus has spread to Europe and Asia. _L. albus_ and _L. mutus_
appear in our continent chiefly as Arctic migrants.

The Black Grouse (_Lyrurus tetrix_) belongs to a closely allied genus,
which has only two species. One of these is very local in distribution,
being confined to the Caucasus, but the smallness of range is to some
extent compensated for by the peculiarity of its name, which is _L.
mlokosiewiczi_. The Black Grouse, on the contrary, is widely
distributed. It inhabits Northern Asia from the Pacific to the Ural
Mountains, and extends as far south as Pekin and the Tian Shan range. In
Europe it is found from the extreme east to the Pyrenees, the Apennines
on the south, and to Great Britain and Scandinavia in the north. It is
important to note its absence from Spain, the Mediterranean islands, and
Ireland; and we have learned that it is one of those Siberian migrants
which have succeeded in establishing themselves in the Alps.

The Capercaillie (_Tetrao urogallus_)--another great favourite with
sportsmen--is now generally separated generically from the Black Grouse,
though they are of course near relations. Its range greatly resembles
that of the Black Grouse, except that it does not go quite as far east
in Siberia, not having been met with beyond Lake Baikal. From there it
is found westward as far as the Pyrenees. It occurs also in the
Carpathians and the Alps. In England, where it used to be known by the
name Cock of the Wood, it became extinct at some remote period in
history, while it lingered on in Scotland and Ireland until the end of
the last century. In Scotland it has been reintroduced into several
counties, and being protected, it appears to spread from these
artificial centres of distribution.

Like the Black Cock, the Capercaillie is a Siberian migrant, and it is
one of the few Siberian species which have reached Ireland, as I have
had occasion to mention in dealing with the origin of the British fauna.
Two other species of Capercaillie and an allied genus (_Falcipennis_)
are met with in the extreme north-east of Siberia, and six other genera,
all belonging to the grouse family, are confined to North America. We
have therefore a very intimate relationship between the grouse of Asia
and those of North America, some species even ranging right across the
two continents.

The last genus of this very interesting family is _Tetrastes_. This
grouse is not familiar to British ornithologists, since it is entirely
absent from the British Islands. But sportsmen who have tramped over
Scandinavia know it well by the name of Hazel Grouse. It is ashy grey in
colour, barred and vermiculated with black. The Common Hazel Grouse
(_Tetrastes bonasia_) is found from Northern Spain in the west right
through the mountainous parts of Central and Northern Europe and
Northern Asia to Kamtchatka and the Russian convict island of Saghalien
in the Pacific. Besides the Common Hazel Grouse, two other species are
known, one from Eastern Russia and the other from China.

Having now shortly reviewed the whole grouse family, we have seen that,
although some species live within the Polar Circle, the majority are
more or less confined to the more temperate or rather the less arctic
parts of the Northern Hemisphere. They are quite absent from Southern
Asia and even the southern parts of North America, and almost so from
the Mediterranean basin. The whole range of the family is therefore
suggestive of a northern origin, and this view agrees perfectly with all
the details of distribution. The centre of distribution lies in Northern
Asia, or in Arctic North America. From there the great genus _Lagopus_
spread east and west, reaching Europe by these vastly divergent routes
at a time when the physical geography was very different from what it is
to-day. Several of the species common to the Alps and Scandinavia have
migrated from Siberia direct to Eastern Europe. But we can now imagine
how from a similar centre in Asia--perhaps at a rather more remote
time--a species spread eastward across North America and Greenland to
Scandinavia, and westward along the mountain ranges of the Tian Shan and
the mountains of Asia Minor to Greece, and finally to the Alps. We
should then have the same species in the Alps and in Scandinavia, not
far removed from one another; but how different were their paths of
migration! This, however, is not an imaginary instance. Such a migration
must have actually taken place in a good number of instances among the
terrestrial invertebrates and also among plants.

The view still current among many zoologists and botanists, that animals
and plants were driven down into the plain from the mountains of Europe
during the height of the Glacial period and there lived together till
the return of a more genial temperature, when they retreated to their
mountain homes, is a very plausible one. During their sojourn in the
plain, the plants and animals--say from Scandinavia--intermingled with
those from the Alps; and when the time of separation came, many Alpine
forms retired northward with the Scandinavians, while many Scandinavians
would go with the Alpines to their home. In this way the similarity
between the Alpine and Scandinavian faunas and floras is assumed to have
been brought about. These theories, first promulgated by Edward Forbes,
were hailed with general satisfaction by the scientific world. Even
Darwin says of them (p. 331), that grounded as they are on the perfectly
well-ascertained occurrence of a former Glacial period, they seemed to
him to explain in a satisfactory manner the present distribution of the
Alpine and Arctic productions of Europe. To the present day this view
meets with much favour among naturalists. It is somewhat similar to one
which has recently been strongly supported by Professor Nehring and
accepted by Professor Th. Studer and many others. They have never made
it quite clear whether the pre-glacial fauna and flora are supposed to
have been absolutely destroyed by the glacial climate, or whether part
of them have been able to take refuge somewhere in the south; but the
great mass of our Alpine plants and animals are believed to have been
derived from the Siberian invasion, which I have fully described in the
fifth chapter. This invasion spread over the European plain, and when
the climate ameliorated, both animals and plants migrated north and
south to the mountains. This view agrees with the earlier theory, except
that the adaptation to Alpine conditions would, according to the former,
have taken place since the close of the Glacial period, during which
time no such modification or change of species seems to have been
produced in other parts of the world. The characteristic fauna of the
Alps, as has been gathered from the preceding pages, is mainly of
Central Asiatic rather than of Siberian origin. Migration to the Alps
took place by the Oriental route long before the Siberian invasion. Some
of the species of the latter have penetrated to the Alps, but these
Siberian species have not given to the fauna of the highest European
mountain range the striking character with which we all associate it.

Before concluding this chapter, a few remarks on the botanical aspect
of the Alpine problem might not be out of place. It will enable us to
judge which of the views indicated is the more probable, and will add to
the interest which may have been aroused by the perusal of this sketch
of the fauna of the Alps. Very much the same train of argument was
applied as to the course of events in the formation of the Alpine flora
as in the case of the fauna. The plants were all supposed to have been
killed or driven away by the arctic temperature of the Glacial period,
and their place taken by new migrants from the north or east when the
climate ameliorated.

Professor Engler, one of the highest living authorities on the
geographical distribution of plants, is of opinion (p. 102) that a large
number of the indigenous Alpine species did not originate till after the
close of the Glacial period, because so many of them are absent from the
Sierra Nevada in Spain, where the condition for their well-being exists,
while many have evidently spread from the Alps to the Carpathian
Mountains and to the Pyrenees. He does not believe that a glacial flora
could have existed in the plain between the Sierra Nevada and the
Pyrenees during the Glacial period (p. 109). In speaking of the
Caucasus, Professor Engler informs us (p. 117) that a good many species
which do not occur in the Alps reached these mountains from Siberia.
Apart from the northern glacial plants, the Caucasus has only few
species in common with the Alps, more with the Balkan mountains and
Northern Persia. Turning to Afghanistan, our author mentions (p. 121) a
few Alpine plants as occurring in that country, and likewise in the
Caucasus and the Himalayas. He considers it probable that the route of
migration of some glacial plants from the east to the west, and _vice
versâ_, lay across the Afghan mountains. Many of our Alpine plants occur
in the Siberian mountains, but in the Altaï and Eastern Siberia
generally a considerable number of these are by no means confined to the
mountains (p. 125). They are also met with in the lower regions, and the
rare Alpine Edelweiss (_Leontopodium alpinum_) frequently covers wide
tracts in the plain, and is passed by almost unnoticed by the Siberian
botanist.

Special attention is drawn by Professor Engler to the fact (p. 130) that
several of the Siberian plants inhabit the Alps and the Caucasus, but
are not found in Scandinavia. And from this he deduces the conclusion
that part of the Siberian flora migrated in a south-westerly direction
towards the Caucasus and the mountains of the Mediterranean area,
exactly in the manner indicated in respect to the fauna of the Alps. We
learned that the migration to the Alps from Central and perhaps also
parts of Northern Asia took a south-westerly course first, and was then
followed by one in an easterly direction. I called the former the
Oriental migration and the latter the Siberian. Later on Professor
Engler states (p. 142) that the main mass of the Siberian forms of
plants certainly wandered westward to the south of the Ural. This is
proved by the numerous glacial plants found in the Caucasus, while the
glacial flora of the Ural Mountains is poor. Finally, he expresses the
opinion that the probability of most of the Alpine plants occurring in
Arctic Siberia, having wandered from the Alps, by way of Scandinavia,
Greenland, and North America, to North-eastern Siberia, is greater than
the direct migration from Europe to Siberia (p. 143).

Another continental writer on the Alpine flora who deserves special
mention is Dr. Christ. His observation that Alpine plants by no means
suffer from a high temperature (p. 309), but solely from a drying up of
the soil, seems to me to point to the correctness of the view I have
expressed on several occasions, that these plants have originated long
before the Glacial period at a time when the climate was warmer and
moister than it is now. It seems quite natural to Dr. Christ that the
Arcto-Alpine flora should have originated in Asia, but he excepts thirty
species which are absent from Northern Asia, though occurring in America
(p. 327). These he thinks have penetrated direct from America to the
Alps by way of Scandinavia, since no less than twenty-three still occur
in the latter country. In the human population of the Alps, he continues
(p. 336), one can distinguish an indigenous Celtic race, a Germanic
colder and more apathetic race, and a more lively Roman one. The flora
is composed of quite a similar mixture. We find also an indigenous
element--an Arctic and a Mediterranean one. The last element is a
survival of the Tertiary flora of the Central European plateau (p. 532).
The plants were driven down to the shores of the Mediterranean, and it
is only after the retreat of the glaciers that a few of them have been
able to regain their ancient territory. The incoming Asiatic and North
American flora likewise retired at the end of the Glacial period to the
Alps and the Arctic countries, and left isolated traces of its former
abundance on the North European plain. The bulk of the Arctic or Alpine
flora is held to be of Asiatic origin. Since Siberia shows little trace
of having been glaciated, owing to the dryness of the climate, a rich
flora was able to develop there, which spread into Europe as soon as the
vanishing glaciers made room for it.

These are the views of Professor Engler and Dr. Christ. They agree in so
far as both of them maintain that the bulk of the Alpine flora is
post-glacial--that is to say, that it has developed quite recently, or
migrated to the Alps after the glaciers had retreated from the plain to
the mountain recesses. It is assumed by Dr. Christ that while Europe was
practically uninhabitable, a rich flora survived in Northern Asia,
because the climate there was too dry for the development of glaciers.
Due consideration in this interesting speculation, however, is not given
to the fact which he himself emphasised, that Alpine plants are
particularly prone to suffer from a dry climate. Even a moderately dry
cold kills most of them. How can we then reconcile this fact with the
theory of their origin in a dry and intensely cold climate? I quite
agree with the views as to the Asiatic origin of the bulk of the Alpine
flora, while the dry state of the Siberian climate is certainly
indicated by the extremely feeble development of the glaciers during a
large part of the Glacial period. We know, however, that in Pliocene and
even in early Glacial times the atmospheric conditions must have been
very different in Siberia. A great slice of Central Asia was under
water, and numerous freshwater lakes covered the lowlands in the north,
so that the climate must have been damp though not cold enough for the
formation of extensive glaciers. Everything, in fact, seems to indicate
that the migration of the Asiatic Alpine flora took place at a very
early date--probably long before the Glacial period--either by the
Oriental or by the Arctic route _viâ_ North America, Greenland, and
Scandinavia. But would this not necessitate a survival of the Alpine
plants in the Alps themselves? That is the view which has already been
expressed with regard to the fauna, and the flora probably followed a
very similar course. This is by no means a novel theory, however, and
though unfortunately an untimely death has removed one of our very best
authorities on the Alpine flora before he had completed his life's work,
we have some indications in the earlier writings of John Ball that his
opinions on the origin of that flora did not coincide with those held by
the leading continental authors. To quote the words of this
distinguished botanist (p. 576): "Is it credible that in the short
interval since the close of the Glacial period hundreds of very distinct
species and several genera have been developed in the Alps, and--what is
no less hard to conceive--that several of these non-Arctic species and
genera should still more recently have been distributed at wide
intervals throughout a discontinuous chain some 1500 miles in length,
from the Pyrenees to the Eastern Carpathians? Nor would the difficulties
cease there. You would have left unexplained the fact that many of the
non-Arctic types which are present in the Alps are represented in the
mountains of distant regions, not by the same, but by allied species,
which must have descended from a common ancestor; that one species of
_Wulfenia_, for example, inhabits one small corner of the Alps, that
another is found in Northern Syria, while a third allied species has its
home in the Himalaya." Mr. Ball is of opinion (p. 584) that the effects
of the Glacial period have been greatly overrated. "Even during the
period of maximum cold the highest ridges of the Alps were not
completely covered with snow and ice; for we still see by the appearance
of the surface, the limit above which the ancient ice did not reach, and
in the middle zone the slopes that rose above the ancient glaciers had a
summer climate not very different from that which now prevails. In my
opinion the effect of the Glacial period on the growth of plants in the
Alps was to lower the vertical height of the zones of vegetation by
from one to two thousand feet." He acknowledges that there was probably
a moderate diminution of the mean temperature of Europe with an
increased snowfall, so as to cause a great extension of glaciers on all
the mountains of Northern Europe. "But that the climate of Middle Europe
was such that the plants of the high Alps could spread across the plains
seems to me an improbable supposition" (p. 584).

On the Continent, also, some botanists seem to feel that Forbes's
theories of the origin of the Alpine flora, which were at first hailed
with such delight, and accepted by almost every naturalist as the final
verdict, must be modified in the light of recent researches. Professor
Krasan believes that many plants which now live in the high Alps
flourished in pliocene times at sea-level (p. 37). "Especially the
evergreen species exhibit the impression of an originally mild
climate--of a climate without winter frosts--for otherwise the plants
would have developed into species with deciduous leaves." To the
favourable conditions, consisting in periodic snowfalls and high summer
temperature, must be attributed the fact that in the highlands so many
more species from Tertiary times have survived than in the plains. The
temperature was probably much higher during the Glacial period than is
generally believed. The climate was more moist, thus contributing to an
abundant snowfall, while the survivors of ancient Tertiary times were
able to repeople the parts which were temporarily devastated by the
advancing glaciers.

In so short a chapter it is impossible to deal with the Alpine fauna in
a manner more deserving of this theme. I have merely sought to give a
sketch of the general outlines of the subject and to suggest another
possible mode of origin of Alpine animals than that currently believed
in by naturalists. It is to be hoped these suggestions will be useful to
those intending to reinvestigate the problems raised in this chapter.
When our knowledge of the fauna of Asia is more complete, it will be
possible to give a more thorough and in many respects a more
satisfactory history of the European fauna than at present.


SUMMARY OF CHAPTER VIII.

In early Tertiary times the area now covered by the European Alps was
covered by the sea. Islands slowly rose above the surface of the waters,
which finally coalesced to form a peninsula connected with the mainland
in the east. Animals now began to invade the new territory which
continued to rise, while the sea retired farther and farther to the
north and south. During the Pliocene Epoch the sea ceased to wash the
northern shores of the Alps, and both emigration and immigration became
possible in that direction, and also from and to the west.

The Alpine fauna and also the flora are made up of a number of elements,
the eastern one being the oldest. The latter is represented in the Alps
by the older and newer Oriental migration. The general range of the
Alpine Steinbock, Chamois, Marmot, Vole, Shrew, and Hare are specially
referred to. The Alpine birds are few in number, and all of them are
readily traceable to an Asiatic ancestry. Among the Amphibia, the
Salamanders are considered of Alpine origin.

Dr. Kobelt tells us that a uniformity of character marks the Alpine
molluscan fauna. _Campylaea_,--often considered a sub-genus of
_Helix_,--_Pomatias_, _Zonites_, are looked upon as truly Alpine genera.
For very long periods the Alps seem to have received no addition to
their molluscan fauna from other areas. The case is very different with
the _Lepidoptera_, some of the most striking species being evidently
Asiatic immigrants. Some examples of _Coleoptera_ and _Orthoptera_ are
mentioned, and their origin discussed.

We find as the result of these considerations that the majority of the
Alpine species are either indigenous or have come from Asia with the
Oriental migration. None of the northern or western immigrants appear to
be among the characteristic Alpine species, and it seems that the
Siberian migrants have not retired to the Alps, as some naturalists have
been led to suppose. It is evident that the fauna must have survived the
Glacial period on the Alps, though according to geological evidence
glaciers of enormous size originated on these mountains.

The identity of many Alpine species with Scandinavian ones appears at
first sight due to a direct migration from the Alps to Scandinavia or
_vice versâ_. Perhaps such a migration has taken place to some extent,
but it is probable that from a Central Asiatic centre some species
spread across Arctic America into Northern Europe, and also westward to
the Alps. The Grouse family forms an interesting example.

There are two older theories which explain the similarity between the
Scandinavian and Alpine faunas. Forbes's view, which gained most
adherents among naturalists, was that the Scandinavian and Alpine
animals were driven into the plain by the cold during the Glacial
period, and when they ultimately regained their homes, some individuals
of the northern species moved southward, and a few of the southern ones
northward. By the more recent theory of Nehring, the Siberian animals
which invaded our continent from the east, and then spread northward to
Scandinavia and southward to the Alps, formed the nucleus of the faunas
of these two areas. The objections to both of these views are fully set
forth in this chapter.

A few remarks on the botanical aspect of the Alpine problem conclude the
chapter. The origin of the flora has been explained in a very similar
manner to that of the fauna. But already Ball and Krasan have raised
their voices against the current theories, as the facts of distribution
appear to them more satisfactorily explained on lines more consonant
with those which I have used in discussing the origin of the Alpine
fauna. One of the most important conclusions obtained by this study of
the flora in conjunction with the fauna, is that I have emphasised in
most of the preceding chapters--viz., that the Glacial period in Europe
was not a time of extreme cold, and that its destructive effect on the
animals and plants was by no means such as is currently believed.




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Sjögren, H.--Ueber das diluviale Aralo-Kaspische Meer und die
nord-europäische Vereisung, "Jahrb. d. Kais. K. Geol. Reichsanstalt,"
vol. xl., 1890.

Sollas, W. J.--On the Origin of Freshwater Faunas, "Trans. Royal Dublin
Soc." (2nd ser.), vol. iii., 1884.

Speyer, A. and A.--"Die Geographische Verbreitung der Schmetterlinge
Deutschlands und der Schweiz," vol. i., 1858.

Struckmann, C.--Ueber die Verbreitung d. Rennthiers, in d. Gegenwart,
etc., "Zeitschr. d. deutsch. Geol. Gesell.," vol. iii., 1883.

Suess, E.--"Das Antlitz der Erde," vol. i., 1892.

Tcherski, J. D.--Das Janaland und die Neusibirischen Inseln, "Mém. Acad.
Imp. St. Petersburg," vol. xl., 1892.

Thomas, O., and Barrett-Hamilton, G. E. H.--The Irish Stoat distinct
from the British species, "Zoologist," 1895.

Wallace, A. R.--"Island Life," 2nd edit., 1892.

Warming, E.--Ueber Grönlands Vegetation, "Botanische Jahrbücher," vol.
x., 1888-89.

White, F. B.--Some Thoughts on the Distribution of the British
Butterflies, "The Entomologist," vol. xiv., 1881.

Woodward, B. B.--On the Pleistocene (non-marine) Mollusca of the London
District, "Proc. Geologists' Association," vol. ii. (_vide_ also Kennard
and Woodward).

Wright, J.--Boulder-clay a marine deposit, "Trans. Geol. Soc. Glasgow,"
vol. x., 1896.




INDEX.


  _Ablepharus pannonicus_, 258

  _Accentor collaris_, 316
    _modularis_, 317

  Accidental distribution, 12, 26

  _Acipenser ruthenus_, 29

  Acme, 323

  Adams, Leith, 112, 150

  Ægean continent, subsidence of, 272-273

  Agriolimax, 284

  _Alactaga jaculus_, 204

  _Alca impennis_, 92, 142

  Alligator, accidental dispersal of, 14

  _Allolobophora Georgii_, 115, 302
    _veneta_, 115, 302

  Alpine Accentor, 316
    Chough, 317
    fauna, survival of, during Glacial period, 332
    flora, 341-348
    flora, age of, 78, 79
    flora, suitable conditions for, 78-79
    Hare, as a test of climate, 316
    Snow-finch, 318

  Alps, component elements of fauna, 311-312

  Alston, E. R., 312

  _Alytes cisternasii_, 295
    _obstetricans_, 295

  _Amalia_, 284

  America, introductions from, 24

  American beetles in the British Islands, 167
    plants, origin of, in the British Islands, 144
    plants in Ireland, 166
    sponges in Ireland, 166

  _Ampelis garrulus_, 205

  Amphibia of Europe, 193-194
    dispersal of, 21

  _Amphicoma_, 268

  Andalusian Bush-quail, 291-292

  _Anergates_, 167

  Anglo-Scotian fauna, 95

  Animals as tests of climate, 71-75

  Antelope, 39

  Ants, European origin of, 161

  _Apollo_, 325

  _Apus glacialis_, 94, 167

  Aralo-Caspian Sea and Arctic Ocean, connection between, 219-231

  _Arbutus unedo_, 110, 307

  Arctic animals in Caspian Sea, 238
    flora in Europe, 238-241
    Hare, origin of, 148-149, 158-159
    Hare, range of, 136-138
    Lepidoptera, 200
    plant-beds at Bovey Tracy, 238
    plants, 143-144
    plants, delicacy of, 185
    mollusca in Red Crag, 235-236
    Seal, 174
    sub-region, 132

  _Arctomys bobak_, 204, 313
    _marmotta_, 313

  _Arion_, 48, 299
    _subfuscus_, 49

  _Arionidæ_, origin of, 48, 299

  _Asiminea Grayana_, 99

  Aucapitaine, Baron, experiments by, 15

  Autochthonous species, 10

  Azores, remains of a continent, 19


  _Bacillus_, 269-270

  Badger, distribution of, 43

  _Balea perversa_, 298

  Ball, J., 77, 345-347

  Baltic Sea, fauna of, 174

  Baltic and White Seas, connection between, 175

  Banded Lemming, range of, 138

  Barn Owl, 98

  Barrett-Hamilton, G. E. H., 29, 90, 139, 149

  Barriers to animal migration, 38

  Barrington, R. M., 105

  _Bathyphantes nigrinus_, 94

  Baur, G., 19

  Bearded Titmouse, 292

  Beaver, 203

  Beaver absent from Ireland, 121

  Beddard, F. E., 19, 58

  Bedriaga, J. von, 259-260

  Beetles common to North America and Europe, 161
    American, in British Islands, 167

  Bell (_vide_ Kendall and Bell)

  Black Cock, 143

  Black Grouse, 336

  Blanchard, E., 282

  _Blanus cinereus_, 279, 294

  _Blethisa multipunctata_, 93

  Blytt, A., 34, 52, 79, 185, 239

  Boar, distribution of, 44

  Bobak Marmot, 204

  Boettger, O., 48, 263

  Bogdanov, M. M., 53

  _Bombinator_, 259-260
    _igneus_, 259
    _pachypus_, 259

  Bonnet, 306

  Bonney, T. G., 66, 70, 83, 180, 229

  Boulenger, G. A., 259

  Boulder-clay, foraminifera in, 84
    origin of, 81, 175, 180-181, 229-230
    of Continental Europe, 180, 226-231

  Bourguignat, J. R., 18, 47, 302

  Bovey Tracy, arctic plant beds at, 238

  Boyd, E., 104

  _Branchinecta palludosa_, 167

  Brandt, J. F., 51, 62, 107, 218, 222

  Brauer, A., 132-133

  Brehm, A. E., 139

  Bristle-fern, 115

  British flora during Glacial period, 163

  British Islands, Lusitanian flora in, 288, 306-307
    submergence of, 127

  Brooke, Sir V., 247, 250

  Brunner von Wattenwyl, 270

  _Bufo calamita_, 30

  _Buliminus detritus_, 261
    _fasciolatus_, 261
    _obscurus_, 261
    _pupa_, 261

  Bullfinch, origin of, 191, 255-256

  Bulman, G. W., 114

  Bunge, D., 219

  Bush-quail, Andalusian, 291-292

  Butterflies, Arctic distribution of, 159-161
    origin of North European, 55


  _Caccabis rufa_, 29

  _Campylaea_, sub-genus of _Helix_, 49, 321

  Canary Islands, origin of, 19

  _Canis lagopus_, 135

  Capercaillie, 28, 143, 336-337

  _Capra ibex_, 312
    _ægagrus_, 61, 312
    _pyrenaica_, 312
    _sibirica_, 312
    _sinaitica_, 312

  _Carabus_, 199

  _Carduelis_, 257
    _caniceps_, 258
    _elegans_, 257
    _major_, 257

  Carpenter, G. H., 64, 94-95, 104, 114, 121-123, 288, 301

  Caspian Fishes, 224
    post-pliocene deposits, 222, 226
    Sea, Arctic animals in, 238
    seal, 224

  _Castor fiber_, 203

  Cave deposits, mixture of Northern and Southern animals in, 54

  Cenocosmic species, 24

  Centre of distribution, 12, 43, 47
    origin, shifting of, 202

  _Cervidæ_, origin of, 248

  _Cervus dama_, 251
    _elaphus_, 246-250
    _giganteus_, 108, 251

  _Chamæleon vulgaris_, 279

  Chamois, 312

  Charrs, origin of, 124

  _Chioglossa_, 296

  Chough, Alpine, 317

  Christ, H., 52, 343-344

  Christy, Miller, 105

  _Chrysochraon_, 330

  _Cicindela_, 197-198

  _Cinclus_, 255

  Clarke, Eagle, 105

  _Clausilia_, 47, 262-264, 284
    _bidentata_, 47, 262, 284
    _biplicata_, 47
    _laminata_, 47
    _Pauli_, 48, 263
    _Rolphii_, 47

  _Claviger_, 267-268
    _testaceus_, 268

  Climate in Glacial period, 65, 81, 127, 149, 182-183
    in Pleistocene Europe, 208-209

  Close, Maxwell, 129

  Cod-fish, origin of, 143

  _Coecilianella_, 17

  _Coenonympha typhon_, 93

  Cole, G. J., 83, 106-107

  Coleoptera of Europe, origin of, 197
    common to Europe and North America, 161

  _Colias_, 266

  _Coregonus_, 124
    _clupeoides_, 124
    _pollan_, 124
    _vandesius_, 124

  Cosmopolitan species, 24

  _Cottus_, 92-93
    _bubalis_, 93
    _gobio_, 93
    _quadricornis_, 175
    _scorpio_, 93

  Credner, R., 177-178

  _Cricetus frumentarius_, 190
    _vulgaris_, 204

  Crimea formerly an island, 35

  Crimean fauna, 57

  Croll, J., 66

  _Crocidura_, 253
    _etrusca_, 253, 279

  _Cuniculus torquatus_, 138

  Current, Arctic, 172-173

  _Cyanopolius Cooki_, 293
    _cyanus_, 293

  _Cyclostoma elegans_, 16


  _Danais chrysippus_, 267

  Dartford Warbler, 288

  Darwin, C., 13-15, 17-19, 25, 32-33, 339

  _Daudebardia_, 323

  _Daulias luscinea_, 192

  Dawkins, Boyd, 53, 62-63, 72-73, 107, 112-113, 120, 208, 222-223, 282

  Day, F., 29

  Depéret, C., 44, 276

  Dippers, origin of, 255

  _Discoglossus pictus_, 279, 295-296

  Dispersal of Amphibia, 59
    of beetles (_apterous_), 59
    of British butterflies, 113
    of earthworms, 58
    of planarian worms, 59
    of spiders, 59
    of wood-lice, 59

  Distribution, centres of, 12, 43, 47
    discontinuous, 114

  Dormouse, 316
    absent from Ireland, 121

  _Drapetisca socialis_, 94

  _Dreyssensia polymorpha_, 26, 230-231

  Drift, a marine deposit, 129

  Drude, O., 52, 77

  _Dryas octopetala_, 79, 238

  Dual origin, possibility of, 38

  Dyer, Th., 79


  Earth-worms, distribution of, 19, 23, 58

  Edelweiss, 266, 342

  Egean Continent, subsidence of, 272-273

  Eider-duck, range of, 141

  _Elephantidæ_, origin of, 202, 252-253

  _Elephas primigenius_, 214, 252

  Emery, C., 161, 167

  Endemic species, 10

  Engler, A., 52, 145, 171, 176, 282, 341-342

  English Hare, 29

  _Ephydatia crateriformis_, 94

  _Epoccus_, 167

  _Erebia_, 325-326
    _æthiops_, 325-326
    _epiphron_, 325
    _glacialis_, 326
    _lappona_, 326

  _Eremias_, 258

  Erratics, 181-182

  _Eryx jaculus_, 259

  _Euphorbia hiberna_, 307

  European beetles, origin of, 197
    butterflies, origin of, 200
    land and fresh-water mollusca, origin of, 196
    mammals, origin of, 106, 193

  _Eurynebria complanata_, 302

  _Evotomys Nageri_, 314

  Extension of range, mode of, 38


  Fallow Deer, 251

  Falsan, A., 66, 68-69, 71, 73

  Feilden, H. W., 13, 77, 84-85, 164

  Finmark, Greenland mollusca on coast of, 171

  Fire-toads, origin of, 259

  Fischer, P., 103

  Fishes, Caspian, 224

  "Flotsam and jetsam" theory, 20

  Foraminifera in boulder-clay, 84

  Forbes, E., 64, 101, 110, 114-115, 171, 288, 339

  Forest-Bed an inter-glacial deposit, 70
    corresponding to continental inter-glacial deposits, 120
    fauna of, 232-234
    mollusca, 212-213

  Fossil glaciers, 220

  Fresh-water faunas, origin of, 177

  _Fringilla_, 293
    _cœlebs_, 293
    _madeirensis_, 293
    _montifringilla_, 293
    _spodiogenys_, 293
    _teydea_, 293

  Frog, introduction of, into Ireland, 30-31


  Gadow, H., 139

  Galapagos Islands, 19

  _Galeodes_, 270

  _Gammaracanthus relictus_, 179

  Gardner, J. S., 145

  _Garnieria_, sub-genus of _Clausilia_, 48

  _Gasterosteus aculeatus_, 92

  Gaudry, A., 73, 273

  Geikie, Sir A., 116, 309

  Geikie, J., 59, 66-67, 70, 75-76, 80-83, 116, 129, 163, 182, 216-217,
    226-227, 233, 235, 238

  Geographical changes, importance of, 64

  _Geomalacus maculosus_, 5, 49, 99, 102, 115, 298-299

  Gervais, E., 150

  Glacial climate in France, 150
    period, climate of, 65-81, 127, 149, 182-183
    period in Scandinavia, 176
    period, survival of animals and plants during, 65

  Glaciation of Ireland, 129

  Glutton, 119, 203

  Goldfinch, origin of, 257

  _Gonepteryx_, 296-297
    _cleobule_, 297
    _cleopatra_, 296
    _rhamni_, 296

  Gould, J. E., 20

  Great Auk, range of, 92, 142

  Greenland flora, 161-162
    flora, survival of, 163-164
    miocene temperature in, 146
    mollusca on coast of Finmark, 171
    Tertiary plants, 144-145

  Grouse, 91, 334
    black, 336

  _Gulo luscus_, 119, 203


  Haacke, W., 147

  Hamilton, John, 161

  Hamster, 190, 204

  Hanitsch, R., 94

  Hare, 2, 29, 90
    Arctic, 2, 90-91
    English, 29

  Hare, Alpine, as a test of climate, 316

  Harlé, E., 150

  Harmer, F. W., 182

  Harvest-mouse, 3, 190

  Harvie-Brown, J. A., 105

  Haughton, W., 86

  Hazel-grouse, 337

  Hedge Accentor, 317

  Hedley, C., 20

  Heer, O., 144-145

  _Helix_, 4
    _acuta_, 102, 298
    _aculeata_, 298
    _aspersa_, 24, 195
    _ericetorum_, 298
    _fusca_, 298
    _lapicida_, 4
    _obvoluta_, 4, 297
    _pisana_, 102, 298
    _pomatia_, 15, 32, 195, 262
    _revelata_, 102
    _rotundata_, 122, 274, 298
    _ruderata_, 212-213

  Herdman, W. A., and Lomas, J., 236

  Herring, origin of, 143

  _Heteromeyenia Ryderi_, 94

  Hofman, E., 54

  Hooker, Sir J., 99, 161

  _Hopatroides thoracicus_, 268

  Howorth, Sir H., 73

  Hyalinia, antiquity of, 50

  _Hyla_, 260
    _arborea_, 260-261, 280
    _chinensis_, 260


  Ice-Age, climate of, 65, 81

  Ice-bridge, migration on, 108

  _Idotea entomon_, 178, 224

  Ihering, H. von, 19, 20, 24-25

  Indigenous species, 10

  Inter-glacial deposit, the Forest-Bed an, 70
    periods, climate of, 181, 218

  Introduced species, 10, 23, 27-29

  Introduction by man, 32-33

  Introductions from America, 24

  Ireland, glaciation of, 129

  Irish and Scotch Hare, 136
    Elk, 108, 251-252

  Irish fauna, composition of, 63
    Stoat, 136

  Isle of Man, fauna of, 123

  _Isotoma littoralis_, 94


  Jeffreys, J. G., 27

  Jerboa, 204

  Jordan, H., 103

  Judd, J. W., 61


  Karpinski, H., 222

  Kendall, P. J., 125

  Kendall, P. J., and Bell, A., 174

  Kennard, A. S., 167

  Kennard, A. S., and Woodward, B. B., 4

  Kessler, H., 222

  Kew, H. W., 17, 23, 32

  Killarney fern, 115

  Kinahan, G. H., 107-108, 129

  Kirkdale Cavern, remains in, 54

  Kobelt, W., 49, 56, 58, 62, 75, 195-196, 212, 281, 297, 303, 321-323

  Köppen, F. T., 51, 62, 222, 248

  Krasan, F., 347


  _Lagomys_, origin of, 41, 203

  _Lagopus_, 334
    _albus_, 91, 142, 334
    _hyperboreus_, 334
    _leucurus_, 335
    _mutus_, 91, 142, 334
    _rupestris_, 334
    _scoticus_, 334

  _Laminifera_, sub-genus of _Clausilia_, 48

  Lamplugh, G. W., 107-108

  Land-connection between America and Northern Europe, 61
    British Islands and France, 59-60
    British Islands and Scandinavia, 61
    Europe and North Africa, 61
    Europe and North America, 61, 168-172
    Greece and Asia Minor, 61
    Greenland and Europe, 155, 159
    Ireland and Spain, 110

  Land Mollusca, migrations of, 9

  Land shells, West Indian, 21

  Lartet, E., 51, 73, 107, 150

  Lemming, range of, 138-140

  _Leontopodium alpinum_, 266, 342

  _Lepus_, 27, 29, 31
    _alpinus_, 136
    _cuniculus_, 27, 31, 291
    _europæus_, 29, 316
    _glacialis_, 136
    _lacostei_, 291
    _variabilis_, 2, 29, 136, 315

  Lepidoptera, range of, 159-160
    Arctic, 200
    surviving Glacial period, 54

  Leuckart, R., 176

  Lewis, Carvill, 129

  _Limax_, 284
    _marginatus_, 284
    _maximus_, 284

  _Limnocalanus macrurus_, 179

  _Linyphia insignis_, 94

  "Loess" fauna, 75, 196

  Lomas (_vide_ Herdman and Lomas)

  Lovén, S., 177

  Lusitanian flora in British Islands, 288, 306-307
    spiders, 301

  Lydekker, R., 14, 22, 32, 58, 157, 183, 202, 248, 252

  Lyell, Sir C., 14, 22

  _Lyrurus tetrix_, 336


  _Macroptychia_, sub-genus of _Clausilia_, 48

  Madeira, 19
    molluscan fauna of, 25
    remains of a continent, 19

  Major, Forsyth, 45-46, 280, 282

  Mallet, R., 86

  Mammoth in Siberia, 214-217
    range of, 252-253

  Mammals, dispersal of, 9, 21

  _Mantis religiosa_, 269

  Maps, general plan of, 8

  Margaritana, 93

  Marine connection between Caspian Sea and Arctic Ocean, 62, 219-231
    mollusca, distribution of, 236
    origin of boulder-clay, 82-86, 228-230

  Marine shells above sea-level, 127-128
    transgression in Northern Russia, 172

  Marmot, Alpine, 313
    Bobak, 204

  Marsh-ringlet, 93

  Marshall, Rev., 166

  Martins, C., 68

  Mediterranean land-connections, 276-282

  _Meles_, 43
    _albogularis_, 44
    _anakuma_, 44
    _leucurus_, 44
    _maraghanus_, 44
    _polaki_, 44
    _taxus_, 43

  _Melitæa asteria_, 325
    _cynthia_, 325
    _maturna_, 325

  _Melizophilus undatus_, 288

  Merriam, C. H., 38

  _Metoponorthus cingendus_, 301

  _Microtus_, 313
    _brecciensis_, 314
    _leucurus_, 314
    _nivalis_, 313

  Mid-wife Toad, 295

  Migrations, 8-9
    cause of, 208
    of British shore-forms, 124

  Migration from Asia to Europe by North America, 327

  Migration on ice-bridge, 108
    waves of, 204-206

  Miller's thumb, 93

  Milne-Edwards, A., 282

  Mingling of Southern and Northern Mammals, 72-75, 209

  Miocene geography, 274-276
    temperature in Greenland, 146

  _Miogale moschata_, 290
    _pyrenaica_, 290

  _Molge alpestris_, 320
    _cristata_, 320
    _montana_, 320
    _palmata_, 320
    _rusconii_, 320
    _vulgaris_, 319

  Mollusca in Loess, 196

  Mollusca, distribution of marine, 236

  Molluscan fauna, divisions of British, 102
    Madeira, 25
    Porto Santo, 25

  Molluscs, dispersal of, 17, 24

  Mongoose, 28

  _Montifringilla nivalis_, 318

  More, A. G., 104

  Möschler, E., 160

  _Motacilla_, 254, 292
    _alba_, 292
    _borealis_, 255
    _campestris_, 254
    _lugubris_, 292
    _melanope_, 254

  Mountain Avens, 79

  Mountain-ringlet, 325

  Mouse, distribution of Harvest, 3

  Mud-glaciers, 86

  Murchison, R., 175, 230

  Murray, Andrew, 32-33, 150, 154

  _Muscardinus avellanarius_, 316

  Musk-Ox, range of, 119, 134-135, 203

  _Mus minutus_, 3, 95, 190

  _Mustela africana_, 279
    _boccamela_, 279
    _erminea_, 135-136
    _putorius_, 190

  _Myodus lemmus_, 138
    _obensis_, 138

  _Myoxus_, 316

  _Mysis caspica_, 223
    _micropthalma_, 223
    _relicta_, 179, 223


  Nathorst, A. G., 163, 169, 240-241

  Natterjack Toad, 30

  _Nebria atrata_, 328
    _livida_, 328

  Nehring, A., 96, 107, 119, 196, 208-211, 340

  _Nenia_, sub-genus of _Clausilia_, 48

  Neumayr, M., 19, 67

  Newt, 319

  New Siberian Islands, origin of
    bone-beds, 219
    extinct fauna of, 218

  Nightingale, 192

  Nordquist, 179

  North American marine mollusca in crag deposits, 173

  North European Sea, 172


  Ocean basins, permanence of, 18

  Oceanic Islands, 18

  _Œneis_, 326-327
    _aëllo_, 326

  _Onychogomphus_, 268

  Oriental migration, old and new, 272

  Oriental plants, 282-283

  Origin, centre of, shifting, 202

  _Otiorrhynchus auropunctatus_, 115, 302

  _Ovibos moschatus_, 119, 134-135, 203


  Pacific Continent, 20

  Painted-lady Butterfly, 98

  Palincosmic species, 25

  Pallas's Sandgrouse, 205

  _Panurus biarmicus_, 292

  _Papilio hospiton_, 265

  _Parmacella_, 49

  _Parnassius_, 265-266, 324
    _Apollo_, 265, 324
    _delius_, 324
    _mnemosyne_, 324
    _Nordmanni_, 324

  Partridge, 29

  _Pelias berus_, 192

  _Pelobates_, 295

  _Pelodytes punctatus_, 295

  _Pelophila borealis_, 93

  Penck, A., 66

  Perches, origin of, 143

  _Periops hippocrepis_, 279

  Peschel, O., 177

  Petersen, W., 55, 154, 160, 200

  _Petronia stulta_, 318

  _Pezotettix_, 329-330
    _alpinus_, 329
    _pedestris_, 329

  _Phasianus_, 256-257
    _colchicus_, 31, 257

  Pheasant, origin of, 256-257

  _Phoca annelata_, 174
    _caspica_, 224

  _Phædusa_, sub-genus of _Clausilia_, 263

  _Phylloxera vastatrix_, 24

  Pigs, origin of, 44-46

  Pika, 41

  Pine-Grosbeak, 191

  _Pinicola enucleator_, 191

  _Planorbis dilatatus_, 24
    _glaber_, 167

  Plants, American, in Ireland, 166
    as tests of climate, 75-80
    migration of, 34

  _Platyarthrus_, 299-302

  _Plectrophenax nivalis_, 140

  Pleistocene climate of Asia, 210, 214-215
    Europe, climate in, 208-209
    fauna, northern and southern animals in, 72-75
    mollusca, 211-213

  Pliocene deposits of Sicily, 277
    geography, 276-277

  Pohlig, H., 176

  Polar Bear, 134
    Fox, range of, 135, 149
    origin of animals, 147

  Pole-cat, 190

  _Polydesmus gallicus_, 115, 302

  Polynesian Islands, 20

  _Pomatias_, 49, 321-322

  _Pontoporeia affinis_, 179

  Porto Santo, molluscan fauna of, 25

  Pouched Marmot, 41

  Praeger, R. L., 298

  Praying insect, 269

  _Proboscidea_, origin of, 252

  _Psammodromus algirus_, 295
    _hispanicus_, 295

  Ptarmigan, 91, 142

  _Pupa_, antiquity of, 50

  _Pupa_, 297-298
    _anglica_, 298
    _granum_, 297
    _ringens_, 102

  _Pyrrhocorax alpinus_, 317

  _Pyrrhula_, 191, 255
    _europæa_, 191, 256
    _major_, 191, 256


  Rabbit, introduction of, 27, 31, 291

  _Rana temporaria_, 194, 320

  Range, extension of, 38

  _Rangifer tarandus_, 133, 150-158

  Reade, Mellard, 127-129

  Red Crag, Arctic molluscs in, 235-236

  Red Deer, 246-250

  Red Grouse, 91, 142

  Red-legged Partridge, 29

  _Regulus ignicapillus_, 257
    _maderensis_, 257
    _teneriffæ_, 257

  Reid, Clement, 76, 163

  Reindeer, range and varieties of, 91, 133, 149-158

  Relict lakes, 176-179, 223

  Reptiles, dispersal of, 21

  Reptiles of Europe, 192-193

  _Rhax_, 270

  Rhinoceros, distribution of, 214-216

  _Rhododendron ponticum_, 271

  _Rhopalomesites Tardyi_, 302

  Rock Sparrow, 318

  Route of migration of Siberian mammals, 210

  _Rupicapra tragus_, 312

  Russia, marine transgression in, 172
    submergence of North, 155

  Rütimeyer, L., 43, 57, 281

  _Ryothemis_, 269


  Saiga Antelope, 39, 204

  _Saiga tartarica_, 39, 204

  _Salamandra atra_, 319
    _caucasica_, 319
    _maculosa_, 319

  _Salmonidæ_, origin of, 92, 143

  Sandgrouse, migration of Pallas's, 41, 205

  Sars, O., 177, 223-224

  Saunders, H., 256

  Seal, Arctic, 174

  Sea-urchin, 125

  Sedgwick, A., 86

  Scandinavia, absence of Oriental and Siberian mammals from, 176, 206
    during Glacial period, 176

  Scandinavian boulders, origin of, 172-173
    butterflies in America, 167
    flora, antiquity of, 162, 185
    glaciers, 172

  Scandinavian lepidopterous fauna, 55

  Schulz, A., 52, 155

  Sclater, P. L., 95

  Scotch Argus, 325

  Scotch and Irish Hare, 136

  Siberia, climate of, during Glacial period, 217

  Siberian birds in British Islands, 191-192
    mammals absent from Scandinavia, 176, 206
    mammals absent from Southern Europe, 206
    mammals in Great Britain, 95-96, 190, 202-204
    migration, date of, 208
    steppe-fauna, 39

  Sicily, Pliocene deposits in, 277

  _Silurus glanis_, 29

  Simpson, C. T., 21

  Simroth, H., 48, 299

  Sjögren, H., 226

  Slugs, dispersal of, 16-17

  Snails, dispersal of, 17

  Snow-Bunting, range of, 91, 140

  Snow-Finch, 318

  Sollas, W., 177

  _Somateria mollissima_, 141

  _Sorex_, 202, 314-315
    _alpinus_, 314-315
    _araneus_, 315
    _minutus_, 315

  Southern mammals in Arctic Siberia, 213-216

  Sparrow, introduction of, 28

  _Spermophilus_, 41

  Speyer, A. and A., 55, 200

  Spiders, Lusitanian, 301

  Sponges, American, in Ireland, 166

  St. Erth fauna, 174

  Steinbock, 312

  Steppe-fauna, Siberian, 39

  Sterlet, introduction of, 29

  Stick-insect, 269

  Stickleback, origin of, 92, 143, 166-167

  Stoat, range of, 90-91, 135-136

  Straits of Gibraltar, age of, 277-278, 281

  _Strix flammea_, 98

  _Strongylocentrotus lividus_, 125

  Struckmann, C., 153

  Studer, Th., 340

  Sub-marine plateau between Norway and Spitsbergen, 154

  Suess, E., 61, 273, 282, 303

  _Sus scrofa_, 44-46

  Swallow-tail Butterfly, 264-265

  _Syrrhaptes paradoxus_, 41, 205


  Tailless Hare, 41

  _Talpa_, 291

  Taylor, J. W., 105

  Tcherski, J. D., 214-215, 222

  Tertiary plants in Greenland, 144-145

  _Testacella_, 17, 299
    _haliotidea_, 299
    _maugei_, 102, 299
    _scutulum_, 299

  _Tetrao_, 28
    _urogallus_, 28, 143, 336-337

  _Tetrastes bonasia_, 337

  _Tettix_, 330
    _bipunctatus_, 330

  _Thais cerisyi_, 265

  _Thelphusa fluviatilis_, 270, 281

  Thomas, O., 90

  Thompson, W., 32

  Time of disconnection between Great Britain and Ireland, 63

  Titmouse, bearded, 292

  Toad, Natterjack, 30

  Tree-frog, 260, 280

  _Trichomanes radicans_, 115

  _Tropidonotus viperinus_, 294

  _Tubella pensylvanica_, 94

  Tundras in Northern Europe, 209-210

  _Turnix sylvatica_, 291-292

  Tyndall, J., 68

  _Typhlops lumbricalis_, 259

  Tyrrhenian Continent, 280


  _Unio (Margaritana) margaritifer_, 93

  _Ursus maritimus_, 134

  Ussher, R. J., 92, 105


  _Vanessa cardui_, 98

  _Vertigo alpestris_, 93

  Viper, range of, 192

  Vole, range of, 313-314

  Wagtails, origin and range of, 254, 292

  Wallace, A. R., 12-13, 18-19, 23, 58, 99, 111, 304

  Warming, E., 76, 163

  Watson, H. C., 100

  Wax-bill, migrations of, 205

  Welch, R., 298

  West-Indian land-shells, 21

  White, Buchanan, 509, 113

  Willow-grouse, 91, 142

  Woodward, B. B. (_vide_ Kennard and Woodward)

  Wright, J., 84


  Zittel, 252

  _Zonites_, 49, 195, 322-323


THE END.


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       *       *       *       *       *

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   30 BURNS'S LETTERS.
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   32 SARTOR RESARTUS.
   33 WRITINGS OF EMERSON.
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   38 ESSAYS OF DR. JOHNSON.
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  105 PRINCIPLES OF SUCCESS IN LITERATURE.
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   1 CHRISTIAN YEAR
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   7 BLAKE
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  92 BROWNING'S POEMS.
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  95 LYRA NICOTIANA
  96 AURORA LEIGH.

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Illustrations by T. EYRE MACKLIN, a Photogravure Frontispiece Portrait
of the Author, and over 600 pages of letterpress, printed from large
clear type.

TWENTY YEARS AFTER. By ALEXANDRE DUMAS. With Sixteen Full-page
Illustrations by FRANK T. MERRILL, and 800 pages of letterpress, set
from new type.

LES MISÉRABLES. By VICTOR HUGO. With Eleven Full-page Illustrations, and
1384 pages of letterpress.

NOTRE DAME. By VICTOR HUGO. With numerous Illustrations.

JANE EYRE. By CHARLOTTE BRONTË. With Sixteen Full-page Illustrations,
and Thirty-two Illustrations in the Text, by EDMUND H. GARRETT, and
Photogravure Portrait of Charlotte Brontë. Printed in large clear type;
660 pages of letterpress.


     Tolstoy's Great Masterpiece. New Edition of Anna Karénina.

ANNA KARÉNINA: A Novel. By COUNT TOLSTOY. With Ten Illustrations drawn
by PAUL FRÉNZENY, and a Frontispiece Portrait of Count Tolstoy in
Photogravure.

     "Other novels one can afford to leave unread, but _Anna
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London: WALTER SCOTT, Ltd., Paternoster Square.




Transcriber's Notes.


The publisher's advertisement for the Contemporary Science Series, which
was at the beginning of the book was moved directly after the Index,
before the other advertisements.

Spelling variants were there was no obvious preference were left as is.
These include: "Ægean" and "Egean;" "bobac" and "bobak" (Arctomys);
"boulder-clay" and "boulder clay;" "caspia" and "caspica" (Mysis);
"earthworm" and "earth-worm;" "eocene" and "Eocene;" "europæus" and
"Europæus" (Lepus); "freshwater" and "fresh-water;" "indistinguishable"
and "undistinguishable;" "luscinea" and "luscinia" (Daulias); "maugei"
and "Maugei" (Testacella); "Midwife" and "Mid-wife;" "miocene" and
"Miocene;" "Miogale" and "Myogale;" "oligocene" and "Oligocene;"
"paludosa" and "palludosa" (Branchinecta); "pensylvanica" and
"pennsylvanica;" "Pica" and "Pika;" "pleistocene" and "Pleistocene;"
"pliocene" and "Pliocene;" "polaki" and "Polaki" (Meles); "repeople" and
"re-people;" "Rhodes" and "Rhodos;" "rusconii" and "Rusconii" (Molge);
"souslik" and "suslik", along with derivatives; "subarctic" and
"sub-arctic;" "subdivide" and "sub-divide", along with derivatives;
"submarine" and "sub-marine;" "subtropical" and "sub-tropical;"
"Tianshan" and "Tian Shan;" "woodlice" and "wood-lice", with "woodlouse"
and "wood-louse."

Changed "Atlantis" to "Atlantic" on page 48: "across the Atlantic."

Changed "Millepede" to "Millipede" on page 115: "Millipede, Polydesmus
gallicus."

Added period at end of sentence on page 144: "was more temperate."

Added period at end of sentence on page 145: "such northern latitudes."

Changed "know" to "known" on page 175: "known as the inter-glacial
phase."

Changed "europea" to "europæa" on page 191: "Bullfinch (P. europæa)."

Changed "mers-de-glace" to "mers de glace" on page 226: 'ice-sheets, or
"mers de glace,"'.

Changed "Altai" to "Altaï" on page 245: "the Altaï Mountains."

Changed "Telphusa" to "Thelphusa" on page 281: "(Thelphusa
fluviatilis)."

Changed "Campylæa" to "Campylaea" on page 297: "Alpine sub-genus
Campylaea."

Changed "Grönland's" to "Grönlands" on page 354: "Ueber Grönlands
Vegetation."

Inserted comma after "65" on page 357 in index entry for "Climate in
Glacial period."

Changed "octopetela" to "octopetala" on page 357: "Dryas octopetala, 79,
238."

In the index entry for Mysis, changed "necropthalma" to "micropthalma"
to match the text of the book. However, I suspect both should actually
be "microphthalma."

Changed "Oeneis" to "Œneis" on page 361, in its index entry.

Changed "moschatas" to "moschatus" on page 361: "Ovibos moschatus."

Changed "apollo" to "Apollo" on page 361 in the index entry for
Parnassius.

Changed "Stronglyocentrotus" to "Strongylocentrotus" on page 363:
"Strongylocentrotus lividus, 125."

Changed "Natter-jack" to "Natterjack" on page 363: "Toad, Natterjack,
30."

Changed "Wag-tails" to "Wagtails" on page 364, in its index entry.

Added closing square bracket in advertisement for the HUMOUR OF JAPAN:
"[In preparation.]".





End of Project Gutenberg's The History of the European Fauna, by R. F. Scharff