Botanists have worked at the problem of the European flora much more systematically, and our knowledge of the origin of that flora has been greatly increased within the last twenty years, chiefly by the researches of Professor Engler. More recently, detailed studies have been made in Scandinavia by Professor Blytt, in the Alps by Dr. Christ and Mr. Ball, in Germany by Professor Drude, Dr. Schulz, and many others. Dr. Schulz (p. 1) is of opinion that the great majority of the European plants have either migrated to or have originated in our continent since the beginning of the Pliocene epoch, and that the original home of the immigrants must be looked for in Asia and in Arctic America. From the latter an almost uninterrupted migration must have taken place during the greater part of Tertiary times up to the commencement of the Pliocene epoch, partly over a direct land-connection with Europe by way of Greenland, Iceland, and the Faroes, and also _viâ_ Spitsbergen, Franz Josef Land and Novaya Zemlya, and partly by an indirect one across the Behring Straits between Alaska and Kamtchatka. A good deal of work still requires to be done before zoologists have acquired the same intimacy with the European fauna as botanists have with the flora. However, the view that our animals all come from Asia, as was long ago believed, has been abandoned for some time. The first to bring under the notice of naturalists the hypothesis, that there must have been two distinct migrations of northern animals to Central Europe--one from the north, and another from the east--was the late Mr. Bogdanov. The Arctic species, of which remains have been discovered in the Pyrenees--namely, the Reindeer, Arctic Hare, Willow Grouse, etc., he thought had nothing to do with those which invaded Europe from Siberia during the Glacial period. He maintained that the former had quite a distinct origin, and came from Scandinavia (p. 26). As I shall deal with this problem more fully in a subsequent chapter, I need only mention that I fully agree with the view expressed by Mr. Bogdanov that two distinct migrations of northern species to Central Europe can be traced.