It is well known that this naturalist shares with Darwin and M. Naudin, the honour of having sought in natural selection for an explanation of organic origins. But our fellow countryman has confined himself to a sketch the fundamental character of which he has recently entirely modified. Darwin has embraced the problem as a whole and in its details; he has added to his first work several publications upon subjects very different in appearance, but all of which tend to the same end. He may with justice be considered as the chief of the school. Wallace, who almost anticipated Darwin in the publication of ideas which are common to both, recognises him as his master on all occasions. He has discussed a small number of points in special memoirs which never cover much ground. From not attempting the solution of all the questions suggested by the theory, he has neither met with so many or such serious difficulties as his eminent rival. This, perhaps, explains the fact that he generally shows himself more precise and logical. He therefore, always possessed considerable authority among the partisans of Darwinism, until he published his special views on man. According to Wallace, _immediate and personal utility_ is the only cause which sets _selection_ in action. This is fundamentally the theory of Darwin; but the latter has allowed himself to be influenced by comparisons or metaphors, which have raised sharp criticisms, which have perhaps deceived him, and which he employs more or less to evade his difficulties. We never meet with the same in Wallace, who accepts all the consequences to which his absolute principle leads him. According to Wallace, _utility alone_ is able to account for the manner in which inferior animal forms could have produced apes, and afterwards a being having almost all the physical characters of man as he is now. This _race_ lived in herds scattered throughout the hot regions of the ancient continent. It was not, however, wanting in true sociability; it possessed the perception of sensations, but was incapable of thought; moral sense and sympathetic feelings were unknown to it. It was still only a _material outline_ of the human being, yet superior to the _tailed man_ of Darwin, and to the pithecoid man of Haeckel.