t fact will be
referred to again more fully on p. 153. Meanwhile it should be
remembered that these three species, viz., _Mustela erminea_, _Equus
caballus_, and _Rangifer tarandus_, occur in Ireland in varieties
distinct from those found in Central Europe. It is upon this, and many
other circumstances, that I founded my belief that Ireland was already
separated from England at the time of the arrival of the Siberian
emigrants in the latter country. As we shall see, the Irish Stoat,
Horse, and Reindeer probably came by a different route from that taken
by the English representatives of the same species.

Very few of the lower animals of Siberian origin have reached the
British Islands. Most of those which were formerly thought to be
Siberian are either of East European or of Central and South Asiatic
origin, though they probably joined the Siberian migration on their way
to England. The Arctic migration brought a greater variety of species to
this country than the Siberian, but neither the one nor the other has
contributed more than a small percentage to the British fauna. The bulk
of that fauna is derived from the various European centres of dispersal,
and especially from Central and Southern Asia.

Those animals which have their home in the latter area, I have named
Orientals, though it must be remembered that they need not necessarily
have come from what is known among zoologists as the "Oriental Region."
The terms "Oriental animals" and "Oriental migration" are used here in a
wider sense, and include even those species which reached Central and
Northern Europe from South-Eastern Europe. It is astonishing, what a
vast number of both vertebrate and invertebrate animals can be traced
back to this Oriental migration. Great tracts of Europe were repeatedly
submerged beneath the sea during Tertiary times, and on their
re-appearance were formed into green fields and pastures new for the
rich Asiatic fauna, which was ever ready to flood the neighbouring
continent. This went on, and not for a comparatively short space of
time, as in the case of the Siberian invasion; the immeasurable ages
which passed, whilst several of the Tertiary epochs dawned upon Europe,
witnessed an almost constant stream of Asiatic immigrants pouring in
upon us. Europe returned her own products in exchange, but they must
have been scanty in comparison to the enormous number of species which
have undoubtedly originated in Central and Southern Asia. Ve