ll is peculiar to its shores: now, though we do not know how
sea-shells 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 across three or four hundred miles of open
sea far more easily than land-shells. The different orders of insects
inhabiting Madeira present nearly parallel cases.

Oceanic islands are sometimes deficient in animals of certain whole
classes, and their places are occupied by other classes; thus in the
Galapagos Islands reptiles, and in New Zealand gigantic wingless birds,
take, or recently took, the place of mammals. Although New Zealand
is here spoken of as an oceanic island, it is in some degree doubtful
whether it should be so ranked; it is of large size, and is not
separated from Australia by a profoundly deep sea; from its geological
character and the direction of its mountain ranges, the Rev. W.B. Clarke
has lately maintained that this island, as well as New Caledonia, should
be considered as appurtenances of Australia. Turning to plants, Dr.
Hooker has shown that in the Galapagos Islands the proportional numbers
of the different orders are very different from what they are elsewhere.
All such differences in number, and the absence of certain whole
groups of animals and plants, are generally accounted for by supposed
differences in the physical conditions of the islands; but this
explanation is not a little doubtful. Facility of immigration seems to
have been fully as important as the nature of the conditions.

Many remarkable little facts could be given with respect to the
inhabitants of oceanic islands. For instance, in certain islands not
tenanted by a single mammal, some of the endemic plants have beautifully
hooked seeds; yet few relations are more manifest than that hooks serve
for the transportal of seeds in the wool or fur of quadrupeds. But a
hooked seed might be carried to an island by other means; and the plant
then becoming modified would form an endemic species, still retaining
its hooks, which would form a useless appendage, like the shrivelled
wings under the soldered wing-covers of many insular beetles. Again,
islands often possess trees or bushes belonging to orders which
elsewhere include only herbaceous species; now trees, as Alph. de
Candolle has shown, generally have, whatever the cause may be, confined
ranges. Hence trees would be little likely to reach distant oceanic