ction of new species. But we may thus greatly
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 I do not doubt that isolation is of considerable importance in the
production of new species, on the whole I am inclined to believe that
largeness of area is of more importance, more especially in the production
of species, which will 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 {106} there supported, but the conditions
of life are infinitely 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 others. Hence more new places will be
formed, and the competition to fill them will be more severe, on a large
than on a small and isolated area. Moreover, great areas, though now
continuous, owing to oscillations of level, will often have recently
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 probably 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, will give rise to most new varieties and species, and
will thus play an important part in the changing history of the organic
world.

We can, perhaps, on these views, understand some facts which will be again
alluded to in our chapter on geographical distribution; for instance, that
the productions of the smaller continent of Australia have formerly
yielded, and apparently are now yielding, before those of the larger
Europaeo-Asiatic area. Thus, also, it is