In the fifth chapter will be found the history of the Siberian migration. And since we possess most valuable records of it in the numerous fossil remains discovered in Central and Western Europe, we are able to trace their progress from the east to the west in a very complete and satisfactory manner. In England their first appearance dates from the Forest-Bed, for here we find remains of the Glutton (_Gulo luscus_), Musk-Ox (_Ovibos moschatus_), and others (see p. 204). It seems reasonable to suppose, therefore, that the first entry of these Siberian mammals into Europe took place at or just before the Forest-Bed period. But Professor Nehring tells us in his remarkable work on the Tundra and Steppes (p. 222), that in Germany the remains of the same mammals occur in deposits which are certainly more recent than the lower continental boulder clay; and he is inclined to the belief that they migrated into Europe during the inter-glacial phase which is supposed to have separated the earlier from the later stage of the Glacial period. It is evident that in this case the inter-glacial period in Germany would have corresponded to, and be contemporaneous with, our Forest-Bed period. The deposits immediately preceding the Forest-Bed would also be contemporaneous with the lower continental boulder clay. Although this may seem rather a startling statement to make, from the evidence which will be brought forward in the fourth and fifth chapters I am inclined to the belief that such is probably the case.