R. F. Scharff

“ In past times, before man began to make observations on the geographical distribution of birds and butterflies, or even before the appearance of man in Northern Europe, they may have lived all over the British Islands. For some reason or other they are perhaps dying out or withdrawing towards their original home, which may either be northward, or to the east or south. If we had some clue as to their former history from fossil evidence—or, in other words, if their remains had been preserved to us in geological deposits,—we should have less difficulty in deciding this problem. ”

“ 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. ”

“ I cannot call to mind any large species of mammal which we might reasonably suppose to have originated in South-western Europe. Even among the smaller ones, few give us any definite clue in this respect. For instance, the present range of the genus Myogale—a small Insectivore belonging to the Mole family (Talpidæ) —teaches us nothing. The two living species show discontinuous distribution, and are almost confined to Europe. Myogale occurs fossil in French miocene deposits, but is unknown beyond the confines of our continent. It is therefore probably of West European origin. ”

“ 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. ”

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

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

“ The view of the European origin of the mammoth especially is open to very serious objections. It does not occur in any European pliocene deposits, and could not therefore have originated in our Continent until pleistocene times. That it should then have commenced its travels through Europe and Siberia to the New Siberian Islands and North America seems almost an impossibility. But if we suppose the mammoth to have had its home in India in pliocene times, it could then easily have migrated to all the parts of the world where its remains have been discovered. ”

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

“ The outpouring of the fauna into Europe seems to me to indicate that there was a sudden change of climate in Siberia. This was produced, perhaps, by the rupture of the marine connection between the Arctic Ocean and the Aralo-Caspian. Such an event would not only have caused the sudden shrinkage of the area available for food-supply by lowering the temperature in Siberia, it would have acted also as a means in assisting the fauna to enter a new continent where an inconsiderable number of mammals, already established, were mostly dispossessed of their homes by the advancing eastern host. ”

“ In dealing with the British fauna in particular, I have drawn attention to the fact that it is chiefly in the south of England that we find fossil remains of eastern species of mammals in recent geological deposits. We can actually trace the remains of these species and their course of migration across part of the Continent towards Eastern Europe, and as none of their bones have been discovered in the southern or northern parts of our Continent, it must be assumed that their home lay in Siberia, where many still exist to the present day, and where closely allied forms also are found. ”

“ Siberia has in common with Europe, seems hopeless. Such forms as Arion hortensis, which has been obtained in Siberia, and which, as we have seen, must have originated in Western Europe, migrated in pliocene or miocene times, possibly along the shores of the Mediterranean and across Asia Minor. We have evidence, therefore, of an eastward migration among the land and freshwater mollusca in later Tertiary times, but not of a westward one from Siberia.
A very different view is presented to us by the coleopterous fauna of Europe. Many of our European Beetles are Siberian migrants. ”

“ The fauna of Europe is frequently described as having been of an Arctic nature, but as a matter of fact there existed during the Ice Age a striking and most remarkable mingling of a northern and a southern fauna. The presence of Siberian mammals in Europe is said to have been due to the prevalence of a dry steppe climate, but this view is not supported by other evidence. The Alpine flora in a wide sense is probably pre-glacial in origin, and appears to have survived the Ice Age where it is now known to exist. ”

“ It has been stated by an eminent geologist that during part of the Glacial period the climate was such that neither plants nor animals could have existed in the British Islands. If that had been so, it is evident that very few organisms could have even survived in France, though a number of Arctic species might have dragged on an existence in Southern Europe. At any rate, on the return of more genial conditions, the Arctic species would undoubtedly have been the first to gain admission to the British Islands, to re-people the arid wastes. ”

“ The fauna of the Alps, and also the flora, is therefore made up of a number of component elements. In the first place we have the Oriental element—the migrants from Central and Southern Asia. When the nature and origin of the Oriental fauna in Europe was discussed, reference was made to the fact (p. 272) that we can distinguish an older from a newer Oriental migration. Both of these have entered the Alps. As we might anticipate, many of the older Oriental migrants have developed into new species, laying the foundation of an indigenous Alpine element. ”

“ Every student of natural history, whether he be interested in birds, butterflies, or shells, contributes his share of facts which help to show how the fauna of his country has originated. The capture of a Swallow-tail or of a Marbled White Butterfly in England at once furnishes material for reflection as to the reason of its absence from Scotland and Ireland. ”

“ We have four European species of Parnassius, only one of which is peculiar to our continent, but the locality where it occurs, the Caucasus, is on the borders of Asia. Almost all the other species are Asiatic, none however range to the south. Its headquarters, and I think its original home, are the mountains of Central Asia. From there it [Pg 266] has spread—some species to the Himalayas, and a few to Europe and North America. But these migrations are not of very recent date. Parnassius no doubt arrived accompanied by a large number of other Central Asiatic mountain insects and plants. ”

“ As a matter of fact, Alpine plants have survived in the high North and in the Alps because they are there permanently protected during winter by a covering of snow from very low temperatures, and they are at the same time prevented from drying up. If they are given sufficient moisture and a constant, mild temperature they seem to do very well. Such conditions are afforded them in many parts of the British Islands, and we find indeed the Mountain Avens (Dryas octopetala) , one of the most typically Arctic plants, growing wild in profusion on the coast of Galway, in Ireland, at sea-level. ”

“ Whether we look upon the boulder-clay as a marine or a terrestrial product, it is quite conceivable that, in many instances, the remains of the Arctic plants may have been carried by ice to great distances from where they grew. The probability, however, is in favour of most of them having lived where their remains are now found. Now, it is a remarkable fact, that the single instance in Europe of a deposit of Arctic plants having been found far removed from the maximum extension of the northern ice-sheet is the one quoted above, viz., at Bovey Tracey, in Devonshire. ”

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

“ Besides mammals, the only European animals which have received some attention with a view to a study of their origin, are the Butterflies and the Land-Snails. The entomologists who have taken up the problem have in so far scarcely produced satisfactory results, as they all seemed to be bound down to the hypothesis that practically all the butterflies had been destroyed in Europe during the Glacial period. Hofman, in his interesting little work, comes to the conclusion (p. 50) , that only in Greece and Spain could a small remnant of the butterflies have survived the extreme rigours of climate. ”

“ We are altogether too apt to regard cosmopolitan as synonymous with introduced, and we should hesitate before concluding that because one of our common European species occurs in Australia or South America, it must have been transported there recently by human agency. Some of our widely-distributed forms are probably of very great antiquity, and may have spread to distant lands in early Tertiary times, when a different state of the geographical conditions enabled them to do so. ”

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

“ In still earlier European deposits—the Miocene—we find the ancestors of modern Elephants, which are probably of Asiatic origin. The remains of several kinds of monkeys occur, whose nearest relations are now confined to Southern Asia. Altogether the fauna bears a strong Asiatic facies. Many of our European terrestrial invertebrates probably arrived about this time from Asia. The struggle for existence being keener and the facility for migration much greater in the higher vertebrates, they—or at any rate the mammalian faunas—were subjected to more rapid changes than the invertebrates. ”