Looking now at the Ngerikudi system, we see that elder and younger sisters are distinguished in the generations of EGO and his parents.  Possibly they are the eight-class tribe of Queensland to which Dr Howitt alludes.  If not, we have in them a tribe one stage earlier than the southern Arunta, who have their four classes divided but as yet without any corresponding names.

The Dieri rule is that of the eight-class tribes.  The person designated as the proper spouse for a male is his mother’s mother’s brother’s daughter’s daughter, in other words, the grandchildren of brother and sister intermarry.  This, as we have already seen, is precisely the effect of the eight-class rules.  We are therefore confronted with three possibilities.  Either the Dieri regulations are aberrant or they have introduced these rules under the influence of the neighbouring eight-class system; or the eight-class organisation is a systematisation of the Dieri rule, adopted perhaps to facilitate the determination of marriageableness or otherwise in the case of persons residing at some distance from each other and therefore less likely to be acquainted with genealogical niceties than the members of a small community.  Now if the second of these hypotheses is correct, it is by no means clear why the Dieri, having in view the attainment of the object of the eight-class system, did not simply adopt it; for this we can find no reason; and it is clearly more reasonable on other grounds to suppose that these regulations are of independent origin.  But we know the eight-class rule to have arisen from a division within a generation, which the Dieri rule is not.  Therefore the latter must be sporadic.

The same is probably true of the Urabunna, but here our information is very scanty and the precise working of the rules is far from clear.  What happens is that an elder brother (A) of a woman (B) marries an elder sister (D) of a man (C); the daughter of this elder sister (D) is the proper mate for the son of the younger sister (B) of her husband; this younger sister’s husband is the younger brother, C. Now the term elder brother, elder sister, does not seem to refer to age; the rule appears to be—­once an elder brother, always an elder brother from generation to generation.

We learn from Spencer and Gillen, that all the women of a generation in the one phratry, and presumably within the right totem only, are to a man either nupa (=marriageable) or apillia.  In the case given by Dr Howitt the younger sister is nupa to the younger brother, the elder to the elder brother; but we do not learn how elder and younger are distinguished, if it is not by descent.  Apparently it cannot be by descent, however; for we find that the son of the younger brother and sister marries the daughter of the elder brother and sister.  As to what would happen if the younger brother and sister have a daughter, the elder a son, we have no information; but apparently they cannot marry.  Such a daughter must find the son of two people who stand to her father and mother as they stood to A and D.