m South America, and which has a very
peculiar soil, does not possess one endemic land bird; and we know from
Mr. J. M. Jones's admirable account of Bermuda, that very many North
American birds, during their great annual migrations, visit either
periodically or occasionally this island. Madeira does not possess one
peculiar bird, and many European and African birds are almost every year
blown there, as I am informed by Mr. E. V. Harcourt. So that these two
islands of Bermuda and Madeira have been stocked by birds, which for
long ages have struggled together in their former homes, and have become
mutually adapted to each other; and when settled in their new homes,
each kind will have been kept by the others to their proper places and
habits, and will consequently have been little liable to modification.
Madeira, again, is inhabited by a wonderful number of peculiar
land-shells, whereas not one species of sea-shell is confined to its
shores: now, though we do not know how seashells are dispersed, yet
we can see that their eggs or larvae, perhaps attached to seaweed or
floating timber, or to the feet of wading-birds, might be transported
far more easily than land-shells, across three or four hundred miles of
open sea. The different orders of insects in Madeira apparently present
analogous facts.

Oceanic islands are sometimes deficient in certain classes, and
their places are apparently occupied by the other inhabitants; in the
Galapagos Islands reptiles, and in New Zealand gigantic wingless birds,
take the place of mammals. In the plants of the Galapagos Islands, Dr.
Hooker has shown that the proportional numbers of the different
orders are very different from what they are elsewhere. Such cases are
generally accounted for by the physical conditions of the islands;
but this explanation seems to me not a little doubtful. Facility of
immigration, I believe, has been at least as important as the nature of
the conditions.

Many remarkable little facts could be given with respect to the
inhabitants of remote islands. For instance, in certain islands not
tenanted by mammals, some of the endemic plants have beautifully hooked
seeds; yet few relations are more striking than the adaptation of hooked
seeds for transportal by the wool and fur of quadrupeds. This
case presents no difficulty on my view, for a hooked seed might be
transported to an island by some other means; and the plant then
becoming slightly modified, but still r