ies occur in Asia, six of which are confined to
Central Asia and the Himalayan Mountains, while four have wandered to
North America. The sequence of events, therefore, was that the ancestor
of _Arctomys marmotta_ probably came to the Alps direct from Central
Asia by way of Asia Minor in miocene or pliocene times. It has since
become modified into a distinct species, and has spread to the European
plain, where it occurs fossil in pleistocene strata, and to the
Carpathian Mountains and the Pyrenees.

The great majority of species of the large genus _Microtus_ (_Arvicola_)
are Asiatic, and there can be little doubt that it has originated in
that continent. There is one species of Vole (_Microtus nivalis_) which
occurs in the high Alps, and which has been supposed to be a typical
Alpine form. It is known, however, to occur also in North Italy and in
Bohemia, while _Microtus leucurus_ of the Pyrenees is identical with
this species. But its range is by no means confined to Europe, for it
has also been discovered in Syria and Palestine, while a closely allied
form exists in the Himalayan Mountains. This shows clearly that the
species has migrated to the Alps from Asia Minor. That this migration
may have taken place at an early period--at a time when Sardinia and
Corsica were still connected with Southern Europe--is indicated by the
occurrence of an extinct Vole (_Microtus brecciensis_) in Sardinian and
Corsican pleistocene (?) deposits.

All the Alpine species mentioned except the Chamois can be easily traced
to their former Asiatic home. But even it has its nearest relations in
Asia. I might also refer to another Vole (_Evotomys Nageri_) which is
practically confined to the Alps and Northern Italy, and which has
probably originated there, though most of its nearest relations are
either Asiatic or North American species.

But besides these Asiatic immigrants and their modified descendants we
have a small truly native Alpine mammalian fauna. _Sorex alpinus_--the
Alpine Shrew--occurs only in the Alps, the Harz Mountains, Pyrenees, and
Carpathians. The genus has been found in European eocene strata,--in
vastly older deposits in our own continent than elsewhere,--so that it
is extremely probable that it has originated there. It may then have
developed a new centre of distribution in the newly-formed Alps where
both _Sorex alpinus_ and _S. minutus_ (_pygmaeus_) have their home. From
there they again spread--perhaps already in mio