The objections to islands being thus stocked are, as far as I understand, that certain species and genera have been more freely introduced, and others less freely than might have been expected.

But then the sea kills some sorts of seeds, others are killed by the digestion of birds, and some would be more liable than others to adhere to birds' feet.

But we know so very little on these points that it seems to me that we cannot at all tell what forms would probably be introduced and what would not.

I do not for a moment pretend that these means of introduction can be proved to have acted; but they seem to me sufficient, with no valid or heavy objections, whilst there are, as it seems to me, the heaviest objections on geological and on geographical distribution grounds (pages 387, 388, "Origin" (366/4.

Edition III., or Edition VI., page 323.) to Forbes' enormous continental extensions.