Continental and Island Life [pp. 1-29]

CONTINENTAL AND ISLAND LIFE.
them, however, seem to have enjoyed greater immunity from
causes of change than others, and present accordingly animals
and plants having an antique aspect, geologically speaking, in
comparison with the others. In this sense the Australian province may be regarded as the oldest of all in the facies of its animal forms, since creatures exist there of genera and families
which have very long ago become extinct everywhere else. Next
in age to this should rank the Neotropical or South American
region, which like Australia presents many low and archaic
forms of animal life. The Ethiopian region stands next to it
in this, the Oriental and Nearctic next, and last and most modern in its aspect is the great Palearctic region, to which man
himself belongs, and the animals and plants of which vindicate
their claims to youth by that aggressive and colonizing character already referred to, and which has enabled them to spread
themselves widely over the other regions, even independently
of the influence of man. On the other hand, the animals and
plants of the Australian and South American regions show no
such colonizing tendency, and can scarcely maintain themselves
against those of other regions when introduced among them.
Thus we have at once in these continental regions a great and
suggestive example of the connection of geographical and geological distribution, the details of which are of the deepest interest and have not yet been fully worked out. One great principle is, however, sufficiently established; namely, that the northern regions have been the birthplace of new forms of land life,
whence they have extended themselves to the south, while the
comparative isolation and equable climate of the South Ameri.
can and Australian regions have enabled them to shelter and
retain the old and moribund tribes.
Those smaller portions of land separated from the continental masses, the islands properly so called, present, as might be
expected, many peculiar features. Wallace divides them into
two classes, tho he admits that these pass into each other.
Continental islands are those in the vicinity of continents. They
consist of ancient as well as modern rock-formations, and contain animals which indicate a former continental connection.
Some of these are separated from the nearest mainland only by
shallow seas or straits, and may be assumed to have become
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