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what they are elsewhere. All such differences in number, and the absence of certain whole groups of animals and plants on islands, are generally accounted for by supposed differences in their physical conditions; ... 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; and few relations are more manifest than that hooked seeds are adapted for transportal 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, which might still retain the hooks, which would not form a more useless appendage than the shrivelled wings under the soldered elytra of many insular beetles. Again, islands often possess trees or bushes belonging to orders .. elsewhere including only herbaceous species; now trees, as Alph. de Candolle has shown, generally have, what- ever the cause may be, confined ranges. Hence trees would he little likely to reach distant oceanic islands; and an herbaceous plant, which had no chance of successfully competing with the many fully developed trees growing on a continent, might, when established on an island, gain an advantage by growing taller and taller and overtopping the other herbaceous plants. In this case, natural selection would .. tend to add to the stature of the plant, ... to whatever order it belonged, and thus convert it first into a bush and then into a tree.
Absence of Batrachians and Terrestrial Mammals on Oceanic Islands .
With respect to the absence of whole orders of animals on
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 retaining its hooked seeds, would form an endemic species, having as useless an appendage as any rudimentary organ,— for instance, as the shrivelled wings under the soldered elytra 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 islands; and an herbaceous plant, though it would have no chance of successfully competing in stature with a fully developed tree, when established on an island and having to compete with herbaceous plants alone, might readily gain an advantage by growing taller and taller and overtopping the other plants. If so, natural selection would often tend to add to the stature of herbaceous plants when growing on an island, to whatever order they belonged, and thus convert them first into bushes and ultimately into trees. ↑
With respect to the absence of whole orders on