Each new form,
also, as soon as it has been much improved, will be able to spread over the
open and continuous area, and will thus come into competition with many
other forms. Moreover, great areas, though now continuous, will often,
owing to former oscillations of level, have existed in a broken condition,
so that the good effects of isolation will generally, to a certain extent,
have concurred. Finally, I conclude that, although small isolated areas
have been in some respects highly favourable for the production of new
species, yet that the course of modification will generally have been more
rapid on large areas; and what is more important, that the new forms
produced on large areas, which already have been victorious over many
competitors, will be those that will spread most widely, and will give rise
to the greatest number of new varieties and species. They will thus play a
more important part in the changing history of the organic world.
In accordance with this view, we can, perhaps, understand some facts which
will be again alluded to in our chapter on Geographical Distribution; for
instance, the fact of the productions of the smaller continent of Australia
now yielding before those of the larger Europaeo-Asiatic area. Thus, also,
it is that continental productions have everywhere become so largely
naturalised on islands. On a small island, the race for life will have
been less severe, and there will have been less modification and less
extermination.
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