As in the case of all the other
departments of zooelogy the immediate data themselves are familiar, but
because they are so obvious the mind does not look for their
interpretation but accepts the facts at their face value. While the
phenomena of distribution are no less fascinating to the naturalist, and
no less effective in their demonstration of evolution, their comprehensive
treatment would demand more space than the whole purpose of the present
description of organic evolution would justify. Thus a brief outline only
can be given of the salient principles of this subject in order that their
bearing upon the problem of species may be indicated.
Even as children we learn many facts of animal distribution; every one
knows that lions occur in Africa and not in America, that tigers live in
Asia and Malaysia, that the jaguar is an inhabitant of the Brazilian
forests, and that the American puma or mountain lion spreads from north to
south and from east to west throughout the American continents. The
occurrence of differing human races in widely separated localities is no
less familiar and striking, for the red man in America, the Zulu in
Africa, the Mongol and Malay in their own territories, display the same
discontinuity in distribution that is characteristic of all other groups
of animals and of plants as well.
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