An epoch in M. de Mortillet's life was marked in 1873, when a discussion took place at the Anthropological Congress, in Lyons, between him and M. Abel Hovelacque concerning the precursors of man. The researches of the two masters had already led them, by a series of observations and deductions, to regard as certain the geological existence of a being intermediate between man and the monkey, which they called the _Anthropopithecus_, and they were trying to indicate, hypothetically, its leading characteristics. M. de Mortillet's reasons for believing in the existence of this precursor of man as a definite being were presented in the _Revue d'Anthropologie_, in an article which was translated and published in the Popular Science Monthly for April, 1879. In this paper the author summarized the evidence, already copious, in favor of the existence of Quaternary man, and then took up the question, "Did there exist in the Tertiary age beings sufficiently intelligent to perform a part of the acts which are characteristic of man?" He then reviewed the researches of the Abbé Bourgeois at Thenay in the light of a collection of fire-marked flints which he had exhibited at the International Congress of Prehistoric Archæology and Anthropology held in Paris in 1867, and deduced from the result that "during the Middle Tertiary there existed a creature, precursor of man, an anthropopithecus, which was acquainted with fire, and could make use of it for splitting flints. It also was able to trim the flint flakes thus produced, and to convert them into tools. This curious and interesting discovery for a long time stood alone, and arguments were even drawn from its isolated position to favor the rejection of it. Fortunately, another French observer, M.J.B. Rames, has found in the vicinity of Aurillac (Cantal), in the strata of the upper part of the Middle Tertiary--here, too, in company with mastodons and dinotheriums, though of more recent species than those of Thenay--flints which also have been redressed intentionally. In this case, however, the flints are no longer split by fire, but by tapping. It is something more than a continuation, it is a development. Among the few specimens exhibited by M. Rames, whose discoveries are quite recent, is one which, had it been found on the surface of the ground, would never have been called in question." The evidence afforded by these flints was confirmed by a collection of flints from the Miocene and the Pliocene of the valley of the Tagus shown by Señor Ribeiro in the same exhibition, a considerable proportion of which bore evidence of intentional chipping.