iginated on our continent. _C. silvatica_ and _maritima_ have no doubt
entered Europe from Siberia in recent geological times, probably soon
after a way was opened up across the Tchornosjem district of Southern
Russia--that is to say, in inter-glacial times. The former spread along
the Central European plain as far west as the south-east of England when
Great Britain still formed part of France. _C. maritima_, which
preferred the proximity of the sea, migrated along the shores of the
Caspian and then across Russia to the shores of the Baltic and North
Sea, and has penetrated a little farther north and west in England than
its near relative. _C. litterata_ has a very similar distribution and
origin, but instead of wandering so far west as the British Islands, it
seems to have preferred extending its range southward, and has just
reached Northern Italy.

The closely allied Ground-beetles (_Carabidae_) furnish us with equally
interesting and instructive proofs of a migration from Asia. Over 300
species of _Carabus_ are known to science. The number of species
inhabiting Asia and Europe are about equal. But the genus does not
extend its range to Southern Asia or to South America or Australia. Very
few species enter Africa, and only nine North America, of which three
also occur in Siberia. The genus is unknown in Madeira, and only
represented by three species in the Canary Islands. To judge from its
distribution, it has probably originated in Western Asia. Probably some
_Carabi_ of European origin have spread into Asia, but the Asiatic--or
we might say the Siberian--origin and subsequent migration westward of a
number of well-known forms appears to me evident. Such forms as _C.
clathratus_, _C. granulatus_, and _C. cancellatus_ are no doubt of
European origin, and have only in recent geological times extended their
range across Northern Asia, whilst _C. marginalis_, coming from Siberia,
can hardly be said to have invaded Europe, since it has never been met
with farther west than the eastern provinces of Prussia.

Among the _Carabidae_ there are altogether very many examples pointing to
a migration from Asia to Europe, but I do not wish here to give a list
of all such cases, and only refer to a few of the more remarkable ones.
One of the European species of Demetrias (_D. unipunctatus_), known to
English entomologists as a south-eastern form, seems to have arrived
with the Siberian migration, whilst the closely allied _D.
atr