This theory (presently to be more fully set forth) is original on my part, at least as far as my supraliminal consciousness is concerned. I mean that I conceived myself to have hit on the idea in July 1902. But something very like my notion (I later discovered) had been printed by Dr. Durkheim, and something not unlike it was propounded by Herr Cunow (1894). Mr. Daniel McLennan had also suggested it: and I find that the Rev. John Mathew had stated a form of it in his _Eagle-Hawk and Crow_ (1899), (pp. 1922, 93-112). Mr. Mathew’s hypothesis, however, involves a theory of contending and alien races in Australia. This theory does not seem well based, but, however that may be, I recognise that Mr. Mathew’s hypothesis of the origin of exogamy (p. 98), and of the origin of the ‘phratries’ or ‘primary classes,’ in many respects anticipates my own. He opposes Mr. Howitt’s conclusions, and I may be allowed to say that I would prefer Mr. Howitt, owing to his unrivalled knowledge, as an ally. On the other hand, the undesigned coincidence of Dr. Durkheim’s, Mr. Daniel McLennan’s, Mr. Mathew’s, and Herr Cunow’s ideas with my own, raises a presumption that mine may not be untenable. THE CLASS SYSTEM IN AUSTRALIA Though the existence of what are called exogamous ‘phratries’ (two to each tribe) was made known, as regards the North American tribes, by Mr. Lewis Morgan (to whose work we return) in the middle of the nineteenth century, almost our earliest hint of its existence in Australia came from the Rev. W. Ridley, a learned missionary, in 1853-55. In Mr. McLennan’s _Studies in Ancient History_[2] will be found an account of Mr. Ridley’s facts, as they gradually swelled in volume, altered in character, and were added to, and critically constructed, by the Rev. Mr. Fison, and Mr. A. W. Howitt. These gentlemen were regarded by Mr. McLennan as the allies of Mr. Morgan, in a controversy then being waged with some acerbity. He, therefore, criticised the evidence from Australia rather keenly. It is probable that Mr. Morgan and Mr. McLennan both had some right on their parts--seeing each a different side of the shield--though a few points in the discussion are still undecided. But it seems certain that the continued researches of Messrs. Fison and Howitt, reinforced by the studies of Messrs. Spencer and Gillen in Central Australia, have invalidated some of Mr. McLennan’s opinions as to matters of fact.