In his bodily formation the man-ape differed little from man. The differences which existed were probably of a minor character, no greater than could readily exist within the limits of a species. If this assertion be questioned, it seems sufficient to call attention to the recent researches into the anatomy of the anthropoid apes, which differ in species, if not in genera, from man, yet are closely similar to him in all their main features of organization. Even in the brain, to whose great development man owes his superiority, the only marked difference is in size. Structurally, the distinctions are unimportant. If, then, these distant relatives so closely resemble man in physical frame, his immediate relative in the line of descent must have approached him still more closely in organization. After this ancestor had become a true, surface-dwelling biped, the differences in structure were probably so slight that physically the two forms were in effect identical. The man-ape was, as there is reason to believe, considerably smaller than man, perhaps about equal in size and stature to the chimpanzee, but that does not constitute a specific difference. There may have been some differences in the skeletal and muscular structure. The vocal organs, for instance, probably differed, the evolution of language in man being accompanied with certain changes in the larynx. The skull was certainly much more ape-like. Yet variations of this kind, due to differences in mode of life, are minor in importance, and may easily come within the limits of a species. While the great features of organization remain intact, small changes, due to new exigencies of life, may take place without affecting the zoölogical position of an animal. The most striking difference between man-ape and man, that of the development of the brain to two or three times its size and weight, is similarly unessential in classification while the brain remains unchanged in structure. That it has remained unchanged we may safely deduce from the close similarity between the brain of man and those of the existing anthropoid apes. The cause of the increase in size is so evident that it need only be referred to. Since the era of the man-ape, almost the whole sum of the forces of development have been centred in the mental powers of this animal, with the result that the brain has grown in size and functional capacity, while the remainder of the body has remained practically unchanged.