ady observed, we must remember that this correlation between a
geographically restricted habitat and the zoological or botanical
affinities of its inhabitants, is repeated over and over and over again
in the faunas and floras of the world, so that merely to enumerate the
instances would require a separate chapter.

Furthermore, the general argument thus presented in favour of descent
with continuous modification admits of being enormously strengthened by
three different classes of additional facts.

The first is, that the correlation in question--namely, that between a
geographically restricted habitat and the zoological or botanical
affinities of its inhabitants--is not limited to the now existing
species, but extends also to the extinct. That is to say, the dead
species are allied to the living species, as we should expect that they
must be, if the latter are modified descendants of the former. On the
alternative theory, however, we have to suppose that the policy of
maintaining a correlation between geographical restriction and natural
affinity extends very much further back than even the existing species
of plants and animals; indeed we must suppose that a practically
infinite number of additional acts of separate creation were governed by
the same policy, in the case of long lines of species long since
extinct.

Thus far, then, the only answer which an advocate of special creation
can adduce is, that for some reason unknown to us such a policy may have
been more wise than it appears: it may have served some inscrutable
purpose that allied products of distinct acts of creation should all be
kept together on the same areas. Well, in answer to this unjustifiable
appeal to the argument from ignorance, I will adduce the second of the
three considerations. This is, that in cases where the geographical
areas are not restricted the policy in question fails. In other words,
where the inhabitants of an area are free to migrate to other areas, the
policy of correlating affinity with distribution is most significantly
forgotten. In this case species wander away from their native homes, and
the course of their wanderings is marked by the origination of new
species springing up en route. Now, is it reasonable to suppose that the
mere circumstance of some members of a species being able to leave their
native home should furnish any occasion for creating new and allied
species upon the tracts over which they travel, or the terri