In the present work we are concerned with kinship groups and the marriage regulations based on them.  A kinship group, whether it be a totem kin, phratry, class, or other form of association, is a fraction of a tribe; and before we proceed to deal with kinship organisations, it will be necessary to say a few words on the nature of the tribe and the family.  In Australia the tribe is a local aggregate, composed of friendly groups speaking the same language and owning corporately or individually the land to which the tribe lays claim.  A change of tribe is effected by marriage plus removal, and possibly by simple residence; children belong to the tribe among which their parents reside.  In the ordinary tribe each member seems to apply to every other member one or other of the kinship terms; and this no doubt accounts for the feeling of tribal solidarity already mentioned.  There are however certain tribes in which the marriage regulations, as with the Urabunna, so split the intermarrying fractions, that the tribe is, as it were, divided into water-tight compartments; how far kinship terms are applied under these circumstances our information does not say.

The tribe is defined by American anthropologists as a union of hordes or clans for common defence under a chief.  The American tribe differs in two respects, at least, from the Australian tribe; in the first place, marriage outside the tribe is exceptional in America and common in Australia; in the second place, the stranger gains entrance to the American tribe only by adoption; and we may probably add, thirdly, that the American tribe does not invariably lay claim to landed property or hunting rights.

The tribe is subdivided in various ways.  In addition to the various forms of natal and other associations, there is, at any rate in Australia, a local organisation; the local group is often the owner of a portion of the tribal area.  This local group again falls into a number of families (in the European sense), and the land is parcelled out among them in some cases, in others it may be the property of individuals.  But there is a great lack of clearness with regard to the bodies or persons in whom landed property is vested.  The composition of the local group varies according to the customs of residence after marriage, and the rules by which membership of the kinship organisation is determined.  These two forces acting together may produce two types of local group:  (1) the mixed group, in which persons of various kinship organisations are scattered at random; (2) the kin group, in which either all the males or all the females together with the children are members of one kinship organisation.

Save in the rare instances of non-exogamous kinship groups, the family necessarily contains one member, at least, whose kin is not the same as that of the remainder; this is either the husband or the wife, according as descent is reckoned in the female or the male line; where polygyny is practised, this unity may go no further than the phratry or the class, each wife being of a different totem kin.