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.