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
AEpyornis, which is only recently extinct, are found in the same regions.
But we have no palaeontological 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. Harle 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. " " terrae-novae.
5. " " groenlandicus.
6. " " arcticus.
I hardly think these can be considered of equal value; indeed, though
there may be differences between _R. groenlandicus_, _typicus_,
_arcticus_, and _spitzbergensis_, the antlers exhibit a certain much
closer relationship among one another than to _R. terrae-novae_ 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 europaeus_) 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 Moeschler 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 versa_, 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 centaureae_, _Pachnobia carnea_, _Plusia
parilis_, _Anarta Richardsoni_, _Anarta Schoenherri_, _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
coerulescens_ from Lake Superior and from Scotland do not seem to vary
to the extent of a hair on the antennae. 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 palaeontological 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 _via_ 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 palaeontological
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 Loven
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 larvae, 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.
Palaeontological 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.