Although in oceanic islands the species are few in number, the proportion of endemic kinds (i.

e.

those found nowhere else in the world) is often extremely large.

If we compare, for instance, the number of endemic land-shells in Madeira, or of endemic birds in the Galapagos Archipelago, with the number found on any continent, and then compare the area of the island with that of the continent, we shall see that this is true.