“ The sea forms a barrier to some forms of life but acts as a carrier to other colonizing forms that frequently develop new features in their isolated surroundings where the struggle for existence is greater or less than before. When a sea barrier has existed for a very long time there is a marked difference between the fauna and flora even of adjacent islands. ”

“ In all cases where the continental islands occur, they are connected with the mainland by a continental shelf, and their structure is essentially that of the mainland. The islands off the west coast of Scotland and the Isles of Man and Wight have this relation to Britain, while Britain and Ireland have a similar relation to the continent of Europe. The north-east coast of Australia furnishes similar examples, but in addition to these in that locality there are true oceanic islands near the mainland, formed by the growth of the Great Barrier coral reef. ”

“ In Java and Sumatra, though belonging to the same group, there are marked developments of bird life, the peacock being found in Java and the Argus pheasant in Sumatra, having become too specialized to migrate. ”