A set of animals, with their organisation but little diversified, could hardly compete with a set more perfectly diversified in structure.

It may be doubted, for instance, whether the Australian marsupials, which are divided into groups differing but little from each other, and feebly representing, as Mr. Waterhouse and others have remarked, our carnivorous, ruminant, and rodent mammals, could successfully compete with these well-developed orders.

In the Australian mammals, we see the process of diversification in an early and incomplete stage of development.