er of fossil
skulls in the Museum at Florence, and came to the conclusion that only
three or four species of recent wild pigs can be clearly distinguished
(_b_, p. 298). One of these, viz., _Sus vittatus_, he thinks, is
traceable in slight modifications from Sardinia to New Guinea and from
Japan to South Africa. The centre of distribution of this species lies
in Southern Asia. Of the three remaining species, two, viz., _Sus
verrucosus_ and _S. barbarus_, are entirely confined to the great
islands which form part of the Malay Archipelago. Finally, _Sus scrofa_,
our Central European wild Boar, is so closely related to _S. vittatus_
that the Sardinian Boar might be looked upon as a variety of either the
one or the other. At any rate, Dr. Major recognises clearly in _Sus
vittatus_ the representative of the ancestral stock of which _Sus
scrofa_ is a somewhat modified offshoot.

The fauna of Europe consists, as I have mentioned, to a large extent of
immigrants from the neighbouring continents. This is especially
noticeable among the higher animals. When we come to the lower, such as
the amphibia, we find a larger percentage, and among the land mollusca
the great majority, to be of European origin. The foreigners are, as we
learned, called Orientals, Siberians, and Arctics. For the sake of
convenience, only two of the great European centres of origin have a
chapter devoted to themselves, namely, the Alpine and the Lusitanian
centres. There is another, however, of almost equal importance which
lies in the east.

In the British Islands there is only an exceedingly small and
insignificant group of species which are peculiar, and which we may
consider to have had their origin there. Almost the whole of the British
fauna is composed of streams of migrants which came from the north,
south, and east, though many of these immigrant species have since their
arrival been more or less distinctly modified into varieties or local
races.

The eminent French conchologist Bourguignat (_a_, p. 352) was of opinion
that, as far as terrestrial mollusca were concerned, there are in Europe
three principal centres of creation or dispersion--all situated in
mountainous countries and not in the plains. He distinguished the
Spanish, Alpine, and Tauric centres, and believed that almost all
species known from Europe had originated in one of these three, and that
each of them possessed quite a distinct type of its own. This theory
seems to agree very