On either side, the islands stand on a moderately shallow submarine bank, and these islands are inhabited by the same or by closely allied quadrupeds.

I have not as yet had time to follow up this subject in all quarters of the world; but as far as I have gone, the relation holds good.

For instance, Britain is separated by a shallow channel from Europe, and the mammals are the same on both sides; and so it is with all the islands near the shores of Australia.