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 pa.s.sed. 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 sh.o.r.e species, whilst the former existence of a freshwater lake on the site of the present Irish Sea is indicated by the distribution of some freshwater fishes.

CHAPTER IV.

THE ARCTIC FAUNA.

The lands lying within the Polar Circle are inhabited by an a.s.semblage 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 lat.i.tudes 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-ma.s.ses 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 a.s.sumes a more yellowish hue.

[Ill.u.s.tration: 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 j.a.pan 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 j.a.pan (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.

[Ill.u.s.tration: 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 circ.u.mstances. 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 pa.s.s ere the few who have remained behind and have managed to survive slowly multiply and visibly re-people their native fields." This eloquent pa.s.sage 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 princ.i.p.ally 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 j.a.pan, 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 sh.o.r.es 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.

[Ill.u.s.tration: 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), const.i.tutes 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 c.o.c.k (_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 princ.i.p.al 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 cla.s.sed 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 lat.i.tudes 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 a.s.signed 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 lat.i.tudes. 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 pa.s.sage existed somewhere about Behring Straits to allow a warm current to enter and circulate within the Arctic Seas, we should have the southern sh.o.r.es of Greenland washed by the warm Atlantic current and the northern sh.o.r.es 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 lat.i.tudes 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-ma.s.ses, 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 sc.r.a.p 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 circ.u.mstance.

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

[Ill.u.s.tration: 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 ill.u.s.trates 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 a.s.sociated 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.

[Ill.u.s.tration: 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.]