which had accumulated on them
when they were still Scandinavian glaciers.

As regards the time of the arrival of the Siberian migrants in Europe,
the English Forest-Bed gives us an additional clue to its determination.
Since Siberian migrants are unknown from earlier deposits than this, it
is reasonable to suppose that they arrived in England about the time
when it was laid down. But since they appear in Germany in the
inter-glacial beds subsequent to the deposition of the lower
boulder-clay, the former are probably contemporaneous with the
Forest-Bed. Some of the deposits generally regarded as upper pliocene by
British geologists would therefore have to be classed with the lower
continental boulder-clay as lower pleistocene. In connection with this
theory some interesting faunistic data are given which seem to support
it.

In conclusion, the former presence of Arctic plants in Central Europe
and their bearing on the climatic problems are discussed.

CHAPTER VI.

THE ORIENTAL MIGRATION.

The Oriental migration is closely related to the Siberian. Both have
originated within the Asiatic continent, and in many respects a strict
line cannot be drawn between them. There can be no doubt that some of
the species which we regard as Siberian migrants had their original home
in more southern latitudes, and thus may have formed part of the older
Oriental migration. The home of that migration I take to be Central and
Southern Asia, that is to say, everything south of the Altai Mountains
and the Caucasus. Its members have reached Europe across an old
land-connection which united Turkey, Greece, and Syria, while the
Siberian animals invaded our continent to the north of the Caspian and
Caucasus.

The Siberian immigrants into Europe on the whole are not very numerous,
but it is different with those from the more southern parts of the
Asiatic continent. The members of the Oriental migration form a very
large percentage of the European fauna. No other migration has affected
our continent so powerfully, because it continued uninterruptedly for a
very long time. Hence its results can be traced from one corner of
Europe to the other. We have seen that the Siberian migration only
commenced after the first portion of the Glacial period had passed away.
The Oriental, however, persisted throughout, or at any rate for the
greater part of that period. It commenced ages before it, in miocene
times, or even earlier. And as the AEg