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 _Salmonidae_--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 _via_ 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 Palaearctic 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
palaeontologist 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 palaeontological 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 _AEpophilus Bonnairei_, the Crustaceans _Achaeus 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.