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.

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.

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.

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

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

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

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

Among the most characteristic Arctic plants may be mentioned Dryas octopetala, to which I have already referred as occurring in the west of Ireland; Saxifraga oppositifolia, another British species, occurs in the higher mountains of Scotland, Ireland, and Wales; Braya alpina, Papaver nudicaule, Lychnis apetala, Diapensia lapponica, and Lobelia Dortmanna, which is found in the lakes of Scotland and Ireland. The dwarf birch (Betula nana) also, which still occurs in Scotland and the North of England, and which had formerly a wider range in the British Islands, should be included among these; but there are other plants probably of Arctic origin, though not now occurring in the Arctic Regions, and to these may be classed the so-called American species of plants which are found on the northern and western coasts of Ireland, in the Hebrides, in Scotland, and in North America. These are no doubt the relics of an Arctic flora which flourished in high latitudes in past times when the climate there was more temperate. A list of these species will be found on page 166.

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

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

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

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

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

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

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

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

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

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

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

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.

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. terrÆ-novÆ and caribou. But the whole subject is by no means as well known as could be wished, and a very careful comparative study of recent and fossil remains of the Reindeer from various parts of the Old and New Worlds is much needed to put our views on a firmer basis.

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

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

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

The distribution of few groups of animals is now better known than that of the larger butterflies and moths (Macro-lepidoptera); even those of Siberia have been fairly well investigated. The interesting facts obtainable from their distribution are therefore of special value. No less than 243 species of Lepidoptera are mentioned by MÖschler as being common to North America and Europe. It is extremely probable that a fair number of these have either migrated direct from America to Europe or vice versÂ, though many may be of Asiatic origin, and have wandered east and west from their original home. The following twelve species are mentioned by Petersen (p. 38) as occurring in Arctic Europe and also in Arctic North America, but not in Asia:—Colias nastes, Colias hecla, Syrichthus centaureÆ, Pachnobia carnea, Plusia parilis, Anarta Richardsoni, Anarta SchÖnherri, Anarta lapponica, Anarta Zetterstedti, Cidaria frigidaria, Cidaria polata, Eupithecia hyperboreata; and these, as he remarks, point to the possibility of a former direct land-connection between Europe and North America.

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

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

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

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

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

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

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

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

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

From the nature of the distribution in Ireland of Arctic plants and animals, which occur mostly on the north and west coasts, it would seem that a stream of migration entered from Scotland, and I have no doubt that that same migration came into Scotland directly from Scandinavia by a route over which now roll the waves of the North Sea. There is, moreover, as I already mentioned on p. 94, a very interesting so-called American element in the north-western European flora, that is to say, plants now found in North-west Europe and North America without occurring in Greenland or any of the islands which might have formed the former highway between the Old World and the New. These are probably some of the more ancient Polar plants which have become extinct in the Arctic Regions and survive in isolated patches in favourable localities. We find seven species of these American plants in Ireland, almost entirely confined to the north and west coasts. These are Spiranthes Romanzoviana, Sisyrinchium anceps, Naias flexilis, Eriocaulon septangulare, Juncus tenuis, and Polygonum sagittifolium. To them must be added another plant recently discovered by the Rev. Mr. Marshall in the south of Ireland, namely Sisyrinchium californicum. As I have mentioned in former writings, there are three species of North American freshwater-sponges in Ireland which have not hitherto been discovered elsewhere in Europe or in Asia. These, namely Ephydatia crateriformis, Heteromeyenia Ryderi, and Tubella pennsylvanica, all occur in some of the lakes near the western coast of Ireland.

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

The Coleoptera Diachila arctica, Elaphrus lapponicus, and Blethisa multipunctata are good instances of species which have come to us from North America by way of Greenland. I have already referred to the Lepidoptera, but might add that eleven species of Anarta occur in Scandinavia, eight of which reappear again in Labrador, none of them, however, being met with in Siberia. Then again, take the interesting Crustacean Lepidurus (Apus) glacialis. It is found in Greenland, Spitsbergen, Lapland, and Norway; and formerly, as we know from fossil evidence, it ranged into Scotland. Another Phyllopod, viz., Branchinecta paludosa, inhabits Greenland, Lapland, and Norway. Mr. Kennard suggests that the freshwater Snail Planorbis glaber might also belong to the same migration. And there are no doubt large numbers of others.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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]

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

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

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

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

Professor Blytt directs attention to some such southern relict species of plants now only found in the extreme south-west of Scandinavia, such as Asplenium marinum, Hymenophyllum Wilsoni, Carex binervis, Scilla verna, Erica cinerea, Conopodium denudatum, Meum athamanticum, and Rosa involuta (p. 28).

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

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

SUMMARY OF CHAPTER IV.

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

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

[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.