the Barren-ground and Woodland varieties, have been met with
in European deposits, but only the former occurs in Ireland and the
south of France, whilst eastward the other becomes more common, and
finally is the only one found. It is believed that the Barren-ground is
the older form as far as Europe is concerned, and that it came to us
with the Arctic migration, and that the other Reindeer reached Europe
much later from Siberia, when Ireland had already become detached from
England. The range of the Arctic Hare is equally instructive. It must
have been a native of Europe since early glacial or pre-glacial
times--before the common English Hare had made its appearance in Central
Europe. Along with other Arctic forms, it entered Northern Europe
directly from the Arctic Regions, by means of the former land-connection
which joined, as I remarked, Lapland with Spitsbergen, Greenland, and
North America. There need not have been a post-glacial connection
between Europe and Greenland; the present flora of that country may have
survived the Glacial period in the Arctic Regions, as has been
maintained by some botanists and other authorities. Professor Forbes
argued from the occurrence of the same species of shore mollusca on the
coast of Finmark and Greenland that these two countries were not long
ago joined, so that a slow migration from west to east along an ancient
coast-line could have taken place. That such a migration actually
occurred is further made probable, judging from the presence of American
mollusca in the Crag deposits on the east coast of England. These came
into the North Sea in the first place direct from the Arctic Ocean at a
time when the two oceans freely communicated with one another across the
lowlands of Northern Russia, Northern Germany, and Holland. Arctic
shells are also found below the boulder-clay on the Baltic coast, and a
free communication such as indicated is generally held to have taken
place at no very distant date. The so-called "relict species"--marine
animals left in freshwater lakes in districts formerly covered by this
sea--lend some support to this view. But the view that the continental
boulder-clay is a marine deposit is not now held except by a few, though
I here bring it forward again, as it seems to me to fit in so much
better with the known facts of distribution. The sea just referred to
probably existed throughout the greater part of the Glacial period; and
icebergs, which originated