ideas modify the ideas held as to actually existing consanguine relations, as we conceive them.  The latter peculiarity does not affect the enquiry to any extent; it merely limits the sphere within which consanguinity plays a part, side by side with kinship, in moulding social institutions.  If an Australian tribe, for example, distinguishes the actual mother of a child from the other women who go by the same kinship name, they may or may not develop on parallel lines their ideas as to the relation of the child and his real father.  Some relation will almost certainly be found to exist between them; but it by no means follows that it arises from any idea of consanguinity.  In other communities potestas and not consanguinity is held to determine the relations of the husband of a woman to her offspring; and it is a matter for careful enquiry how far the same holds good in Australia, where the fact of fatherhood is in some cases asserted to be unrecognised by the natives.  In speaking of consanguinity therefore, it must be made quite clear whether consanguinity according to native ideas or according to our own ideas is meant.

The customary limitations and extensions of consanguinity, on the other hand, cause more inconvenience.  They are of course sometimes combined with the other kind, which we may term quasi-physiological, but with this combination we need not deal, as we are concerned to analyse only on broad lines the nature of these elements.  Just as, with us, kinship and consanguinity largely coincide, so with primitive peoples are the kinship organisations immense, if one-sided, extensions of blood relationship, at all events in theory.  In many parts of the world a totem kin traces its descent to a single male or female ancestor; and even where, as in Australia, this is not the case, blood brotherhood is expressly asserted of the totem kin[3].

Entry into the totem kin may often be gained by adoption, though not apparently in Australia, and the blood relationship thus becomes an artificial one and partakes, even if the initial assumption be accepted as true, far more of the nature of kinship than of consanguinity.  In Australia, and possibly in other parts of the world, there is a further extension of natal kinship.  Although the tribe is not regarded as descended from a single pair, its members are certainly reckoned as of kin to each other in some way; the situation may be summarised by saying that under one of the systems of kinship organisation (the two-phratry), half of the members of the tribe in a given generation are related to a given man, A, and the other half to his wife.  More than one observer assures us that there is a solidarity about the tribe, which regards some, if not all other tribes as “wild blacks,” though it may be on terms of friendship and alliance with certain neighbours, and feel itself united to them by a bond analogous to, though weaker than, that which holds its own members together.