Rivers discusses here the question whether the concept of property has an instinctive basis. He does not think that it is necessary to postulate a distinct instinct for the impulse to acquire, and so confines himself to that of retaining wealth. Consideration of animal life and of his studies in Melanesia lead him to the conclusion that the instinct of acquisition is a primary and individual one, though it has been modified in various ways by social tradition; whether these modifications also constitute an instinct cannot as yet be decided. The most striking feature of the paper is the total absence of any reference to all the work that has been done in the past fifteen years on the psychogenesis of the two impulses in question; the word 'anal-erotism' is nowhere mentioned.