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 _via_
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.

No one, I think, has done more in fostering a careful study of the
migrations of animals than our distinguished geologist Professor Boyd
Dawkins. He did not follow Bogdanov in distinguishing two Arctic
migrations; however, he did more in constructing a very ingenious chart
(_a_, p. 111) representing the geography of Europe during the last and
most recent geological epoch--the Pleistocene--and indicating on it the
probable extent, during that time, of an eastern and a southern
migration of mammals. The map is very instructive, and is the first ever
published giving a clear idea of a southern and an eastern migration to
Europe. He believed that the migration of the southern mammals
northward, took place conjunctly with the westward movement of the
eastern species. Having once reached Europe, the southern species are
supposed to have passed northward in summer time, whilst the eastern
forms (he calls them northern) would swing southwards. The two
migrations would thus occupy, at dif