But this conclusively accounts for only one of the many anatomical differences between man and his caudal progenitor. For why should the loss of his tail have resulted in the changed chemistry of the monkey's brain? or in the increased involutions of his brain even? The specific differences between the present and ancestral types are very numerous and demand separate classification. Their variability runs through every bone, muscle, tissue, fibre, nerve. Their blood corpuscles are not the same. The chemistry of their bones essentially differs. The nerves are differently bundled and differently strung. In intonations of voice--symmetry of arms, legs, chest--hairlessness of body, and aquatic and land habits, the frog is a much nearer approach to man than the monkey, as all caricaturists, delineating aldermanic proportions, will agree. And Mr. Darwin might have immortalized himself by deriving the builders of the ancient pile-habitations and other primitive water-rats and croakers of the Swiss lakes, from this tailless batrachian. For everybody knows, or thinks he knows, how the frog lost his tail. If he didn't wag it off, he certainly absorbed its waggishness as a distinguishing characteristic of the "coming man"--the future Artemas Wards and Mark Twains of the race. This ancestral origin will also account for the otherwise unaccountable proclivity of all human juveniles to play at the game of leap-frog! Besides, it would have relieved Mr. Darwin from one of the greatest perplexities he has had to encounter. As he derives man from a hairy quadruped, the absence of hair on the human body, is a phenomenal fact that gives him great trouble. He agrees that it does not result from "natural selection," as he says "the loss of hair is an inconvenience and probably an injury to man." Nor does he suppose it to result from what he calls "correlated development." He is more puzzled over this problem of divestiture than any other, and finds the solution of it only in "sexual selection." That is, he assumes that among our semi-human progenitors, far back in the Tertiary or some other period, some female monkeys were less hirsute than others, and that they naturally preferred males possessing similar characteristics. These divergencies were thus commenced, and, by continuous "sexual selection," the infirmity (for such he regards the loss of hair) was propagated until the race was almost entirely denuded or bereft of this covering. In the same way he accounts for nearly all the differentiations of the race, among the various tribes now or formerly inhabiting the earth. All have sprung from the same semi-human progenitors--_apes that lost their capacity to subsist as apes, and hence found it necessary to subsist as men_!