It would have been easy for me to quote the testimony of travelers and ethnologists in support of the conclusions drawn by me from the forms of relationship among Australian negroes. But I purposely refrain from doing this, with a few exceptions, first because I do not wish to write a general history of the primitive family, and, secondly, because I consider all references of this kind as very doubtful testimony, unless they are accompanied by an analysis of the entire organization. We frequently find analogies to the institutions of a lower stage in a high stage, and yet they are founded on radically different premises and causes. The evolution of the Australian aborigines shows that. Among the Australians of the lower stage, e. g., the hordes are endogamous, among those of the middle stage they are exogamous, and in the higher stage they are again endogamous. But while in the one instance the marriage in the horde is conditioned on the fact that the more remote relatives are not yet excluded from sexual intercourse, it is founded in the other case on the difference between local and sexual organization. Furthermore, the marriage between daughter and father is permitted in the lower stage, and again in that higher stage, where the class organization of the Kamilaroi is on the verge of dissolution. But in both cases the circle of those who are regarded as fathers is entirely different. The character of an institution can only be perfectly understood, if we examine its connection with the entire organization, and, if possible, trace its metamorphoses in the preceding stages.... The characteristic feature of the class system is that by the side of the gentile order, such as is found among the North American Indians, there is always another system of four marriage classes for the purpose of limiting sexual intercourse between certain groups of relatives. Neither the phratry nor the gens of the Kamilaroi forms a distinct territorial community. Their members are scattered among different roving hordes, and they only meet occasionally, e. g., to celebrate a feast or dance.... The origin of gentile systems out of Punaluan groups has never been proven, while we see among the Australian negroes that the classes are clearly and irrefutably in existence among the first traces of gentilism.... The class system in its original form is a conclusive proof of Morgan's theory, that the first step in the formation of systems of relationship consisted in prohibiting sexual intercourse between parents and children (in a wider sense)....