In Australia the tribe--a term to be defined presently--is nearly always split up into two exogamous divisions, which it is usual to call phratries.[5] Then, in some of the Australian tribes, the phratry is subdivided into two, and, in others, into four portions, between which exogamy takes place according to a curious criss-cross scheme.

These exogamous subdivisions, which are peculiar to Australia, are known as matrimonial classes.

Dr.Frazer thinks that they are the result of deliberate arrangement on the part of native statesmen; and certainly he is right in his contention that there is an artificial and man-made look about them.

The system of phratries, on the other hand, whether it carves up the tribe into two, or, as sometimes in North America and elsewhere, into more than two primary divisions, under which the clans tend to group themselves in a more or less orderly way, has all the appearance of a natural development out of the clan-system.

Thus, to revert to the imaginary case of the Cockatoos and Crows practising exogamy across the river, it seems easy to understand how the numbers on both sides might increase until, whilst remaining Cockatoos and Crows for cross-river purposes, they would find it necessary to adopt among themselves subordinate distinctions; such as would be sure to model themselves on the old Cockatoo-Crow principle of separate totemic badges.