different men as forming a relative homogen—a species, as M. de Quatrefages contends. The most ancient human race, that of Neanderthal, is in the same category. Its cranial capacity—that is, that which really characterizes man—is still considerable and higher than in the lowest existing human races. Between the lowest mean of the capacity of the skull of human races, which I put in round numbers at eleven hundred cubic centimetres, and the mean of the highest anthropoid species, which I estimate at five hundred and thirty cubic centimetres, the distance is prodigious when we compare it with such slight mean differences—taking account of the relation of brain-volume to that of the body—as have been determined between the succeeding species, genera, families, and orders of animals. The working of such a cerebral transformation as this calls for would require a length of time defying all our conceptions.
Pliocene man has probably been found in America. Miocene man is indisputable, although we have not yet been able to demonstrate the fact. Now, it is in the Miocene that the monkeys appear with their existing characteristics. Has man, then, been constituted since they appeared? Did the evolution choose an animal whose hind-limb was organized for a life in trees, was at once hand and foot, when there were beside it and already previously existing animals whose organization presented a part of the desired characteristics? There is little probability of it; and considering, I repeat, the number of species which would have been needed to reach the actual constitution of our brain, it seems probable that the preparatory steps are rather taken in the Eocene epoch at the expense of one of those condylarthra which had already the principal morphological characteristics of man except those relating to the brain, and which Mr. Cope has shown to be intermediate between the marsupials and most of the recent mammals. From this point could be made the differentiation corresponding with different modes of life, which has given on one side the ungulate and carnivorous branches and many others that disappeared without forming a stock, and on the other side the quadrumanous and human branches.
The human type—that is, the type that was destined to result in the astonishing brain-development that we know, and to which all the rest is only accessory—had then a stem of its own—a stem which was the most central continuation of the general primitive trunk of the mammalia. In the present order of science, the mammalian class, as a whole, is compared to a branching tree, having numerous principal limbs, each terminating in efflorescences higher in growth. These are our most specialized groups, the Equidæ and the ruminants among the ungulates, the lion and the dog among the carnivores, etc. In this new system the com-