Evidently, if the descendants of Lambert and Colburn had been treated like those of the first Ancon or Mauchamp sheep, two human races would have been obtained, one characterised by a cutaneous carapace, and the other by the possession of six fingers. But here selection was wanting, and the exceptional blood, from being diluted at each fresh marriage, did not fail to be rapidly exhausted. X. Man does not subject himself to the selection, which he applies with so much success to animals and plants. In his species, therefore, the extreme variations which are obtained elsewhere are not produced. It is thus easily explained why the limits of variation are not so extensive with man as with domesticated or cultivated races. But if, for some motive or other, he were to apply the process of selection to himself, we should not have to wait long for the result. By marrying the tallest women to the giants of their guard, Frederick William and Frederick II. had created at Potsdam a real race distinguished for its tall stature. In Alsace a Duke de Deux-Ponts, who imitated the Prussian sovereigns, obtained the same result. There is another cause which contributes powerfully to restrict the limits of variation in man, namely, the power which his intelligence gives him of partly escaping from the effects of the conditions of life. He is always struggling, as much as he is able, against the external influences capable of disturbing the equilibrium which constitutes his well-being. In the tropics, he uses contrivances for avoiding the heat; in the polar circle, he perfects his means of heating; if he emigrates, he carries with him, as far as he can, his manners and customs, and struggles with redoubled care against the new conditions of life. There is nothing strange in finding him successful in neutralising to a certain extent the modifying influences of the external world. XI. Nevertheless, the conditions of life do not surrender their rights; although diminished, their action is none the less real. This is a fact which can be affirmed by what occurs in our great western colonies. Each great European race is there represented by derived _sub-races_ which vary according to the locality. The islands in the Gulf of Mexico, North and South America, and Australia itself, which has been so recently colonised, have at this time their own peculiar races, some of which are remarkably characterised.