ations.

If we turn to nature to test the truth of these remarks, and look at
any small isolated area, such as an oceanic island, although the total
number of the species inhabiting it, will be found to be small, as we
shall see in our chapter on geographical distribution; yet of these
species a very large proportion are endemic,--that is, have been
produced there, and nowhere else. Hence an oceanic island at first sight
seems to have been highly favourable for the production 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 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