sight seems to have been highly
favourable for the production of new species. But we may thus deceive
ourselves, for to ascertain whether a small isolated area, or a large
open area like a continent, has been most favourable for the production
of new organic forms, we ought to make the comparison within equal
times; and this we are incapable of doing.

Although isolation is of great importance in the production of new
species, on the whole I am inclined to believe that largeness of area
is still more important, especially for the production of species which
shall prove capable of enduring for a long period, and of spreading
widely. Throughout a great and open area, not only will there be a
better chance of favourable variations, arising from the large number of
individuals of the same species there supported, but the conditions of
life are much more complex from the large number of already existing
species; and if some of these many species become modified and improved,
others will have to be improved in a corresponding degree, or they
will be exterminated. 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