e joined the
Oriental migrants in their westward and also in their later northward
travels. In a similar way species of plants and animals of Alpine origin
might have joined these migrants in their northward course, and it is
only when we come to carefully analyse the constituent parts of all
these members which have come to us in England from the south, that we
realise the complexity of their origin. Finally, even the Siberian
migrants mingled with the later Oriental ones, and in some cases the
decision as to whether a certain species belongs to the former or to the
latter migration becomes a matter of great difficulty.

SUMMARY OF CHAPTER VI.

Like the last chapter, this deals with the Asiatic migrants. But while
the former described the history of the northern invasion, those animals
which entered Europe from the south-east are here more particularly
referred to. They originated in Central, Southern, and Western Asia. It
is not easy to discriminate in all cases between this Oriental migration
and the Siberian. To a certain extent, even an entry of Northern Asiatic
species has taken place by the southern route, and _vice versa_. On the
other hand, southern species might have come to Europe by the southern
route--that is to say, to the south of the Caspian--and also by the
northern, which lay to the north of that great inland sea. The Red Deer
is a good example. It arrived on our continent by both routes. However,
there is a racial difference in the members of the two migrations. The
small race now found in Corsica, Sardinia, North-west Africa, and
Western Europe, is probably the older of the two, while the larger
one--resembling the American Wapiti Deer--arrived very much later from
Siberia.

The Mammoth, Wild Boar, Badger, the Dippers and Pheasants, are all
Oriental species which have come to us from the south-east; but there
are also Reptiles and Amphibians, and a host of Invertebrates. Not all
the animals, for instance, which have reached us in England from the
south-east are of Asiatic origin. There is an active centre of
distribution in South-eastern Europe itself, from which species radiate
out in all directions. This fact is well illustrated by the genus
_Clausilia_. Species from this centre, and also from the Alps, joined
the Oriental stream in their northward course.

In reviewing a number of instances of Oriental species in Europe, one is
struck by the peculiarity of their having apparently followed tw