Dr. Kobelt tells us that a uniformity of character marks the Alpine molluscan fauna. Campylaea,—often considered a sub-genus of Helix,—Pomatias, Zonites, are looked upon as truly Alpine genera. For very long periods the Alps seem to have received no addition to their molluscan fauna from other areas. The case is very different with the Lepidoptera, some of the most striking species being evidently Asiatic immigrants. Some examples of Coleoptera and Orthoptera are mentioned, and their origin discussed.
We find as the result of these considerations that the majority of the Alpine species are either indigenous or have come from Asia with the Oriental migration. None of the northern or western immigrants appear to be among the characteristic Alpine species, and it seems that the Siberian migrants have not retired to the Alps, as some naturalists have been led to suppose. It is evident that the fauna must have survived the Glacial period on the Alps, though according to geological evidence glaciers of enormous size originated on these mountains.
The identity of many Alpine species with Scandinavian ones appears at first sight due to a direct migration from the Alps to Scandinavia or vice versâ. Perhaps such a migration has taken place to some extent, but it is probable that from a Central Asiatic centre some species spread across Arctic America into Northern Europe, and also westward to the Alps. The Grouse family forms an interesting example.
There are two older theories which explain the similarity between the Scandinavian and Alpine faunas. Forbes's view, which gained most adherents among naturalists, was that the Scandinavian and Alpine animals were driven into the plain by the cold during the Glacial period, and when they ultimately regained their homes, some individuals of the northern species moved southward, and a few of the southern ones northward. By the more recent theory of Nehring, the Siberian animals which invaded our continent from the east, and then spread northward to Scandinavia and southward to the Alps, formed the nucleus of the faunas of these two areas. The objections to both of these views are fully set forth in this chapter.
A few remarks on the botanical aspect of the Alpine problem conclude the chapter. The origin of the flora has been explained in a very similar manner to that of the fauna. But already Ball and Krasan have raised their voices against the current theories, as the facts of distribution appear to them more satisfactorily explained on lines more consonant with those which I have used in discussing the origin of the Alpine fauna. One of the most important conclusions obtained by this study of the flora in conjunction with the fauna, is that I have emphasised in most of the preceding chapters—viz., that the Glacial period in Europe was not a time of extreme cold, and that its destructive effect on the animals and plants was by no means such as is currently believed.
BIBLIOGRAPHY.
(Titles of Works and Papers referred to in the Text.)
Adams, A. Leith.—Report on the History of Irish Fossil Mammals, "Proc. Royal Irish Acad." (2nd series), vol. iii., 1878.