The most striking and important fact for us is the affinity of the species which inhabit islands to those of the nearest mainland, without being actually the same.

Numerous instances could be given.

The Galapagos Archipelago, situated under the equator, lies at a distance of between 500 and 600 miles from the shores of South America.

Here almost every product of the land and of the water bears the unmistakable stamp of the American continent.

There are twenty-six land birds.