This theory of a hypothetical primate ancestor of man, which is supposed to have inhabited the earth during the earlier part of the Tertiary period, and to have presented a more man-like appearance than any known type of ape, was first propounded by Karl Snell in 1863. It was popularized at the beginning of the present century by Klaatsch, who saw in it a means of escape from the absurdities and perplexities of the theory of lineal descent—“the less,” says the latter, “an ape has changed from its original form, just so much the more human it appears.” This saying is revamped by Kohlbrugge to read: “Man comes from an original form much more like himself than any existing ape.” Kohlbrugge’s comment is as follows: “The line of descent of man thus receives on the side of the primates a quite different form from its previous-one. Such new hypotheses as those of Hubrecht and Klaatsch seem, therefore, fortunate for nature-philosophers, because evolution always failed us when we compared known forms in their details, and led us only to confusion. But if one works with such distant hypothetical ancestors, one escapes much disillusioning.” (Quoted by Dwight, _op. cit._, p. 195.) One thing, at any rate, is certain, namely: that we do not possess any fossils of this primitive “large brained, erectly walking primate,” who is alleged to have roamed the earth during the eocene or oligocene epoch. The Foxhall Man, whose culture Osborn ascribes to the Upper Pliocene, is far too recent, and, what is worse, far too intelligent, to be this Tertiary Ancestor. The _Pithecanthropus erectus_, likewise, is excluded for reasons which we shall presently consider. Meanwhile, let it be noted, that we have Osborn’s assurance for the fact that we are descended from a brainy and upright oligocene ancestor, as yet, however, undiscovered.