the island continued rising we
might also expect an occasional new visitant; and I repeat that even one
new being must often affect beyond our calculation by occupying the room
and taking part of the subsistence of another (and this again from
another and so on), several or many other organisms. Now as the first
transported and any occasional successive visitants spread or tended to
spread over the growing island, they would undoubtedly be exposed
through several generations to new and varying conditions: it might also
easily happen that some of the species _on an average_ might obtain an
increase of food, or food of a more nourishing quality{405}. According
then to every analogy with what we have seen takes place in every
country, with nearly every organic being under domestication, we might
expect that some of the inhabitants of the island would "sport," or have
their organization rendered in some degree plastic. As the number of the
inhabitants are supposed to be few and as all these cannot be so well
adapted to their new and varying conditions as they were in their native
country and habitat, we cannot believe that every place or office in the
economy of the island would be as well filled as on a continent where
the number of aboriginal species is far greater and where they
consequently hold a more strictly limited place. We might therefore
expect on our island that although very many slight variations were of
no use to the plastic individuals, yet that occasionally in the course
of a century an individual might be born{406} of which the structure or
constitution in some slight degree would allow it better to fill up some
office in the insular economy and to struggle against other species. If
such were the case the individual and its offspring would have a better
_chance_ of surviving and of beating out its parent form; and if (as is
probable) it and its offspring crossed with the unvaried parent form,
yet the number of the individuals being not very great, there would be a
chance of the new and more serviceable form being nevertheless in some
slight degree preserved. The struggle for existence would go on annually
selecting such individuals until a new race or species was formed.
Either few or all the first visitants to the island might become
modified, according as the physical conditions of the island and those
resulting from the kind and number of other transported species were
different from those of the parent c