LECTURE SIV, 413 



morialj not so races ; species have always propagated in tlie 

 same manner, races have been formed nnder our own eyes ; 

 species are impei'isliable types, races disappear as they have 

 come. We were enabled to show that all these distinctions 

 lost their significance through modern researches; that the 

 chief races of our domestic animals trace their origin as far 

 back as the wild species which surround us j that they have pro- 

 pagated exactly in the same constant manner as these wild 

 species ; — that finally wild species have disappeared from the 

 creation like tamed races; that consequently all distinctions 

 vanish, and that race and species are in this respect perfectly 

 identical. 



Thus there remain only the conditions resulting from gene- 

 ration. Races, it is said, can interbreed and produce a progeny 

 indefinitely prolific. Species, it is said, sometimes interbreed, 

 but their progeny is sterile, if not in the first, certainly in sub- 

 sequent generations. 



This principle, if firmly established, leads, it is believed, 

 to the inference, that all races spring from a single stock, but 

 all species from different primary stocks. Let us first examine 

 how it is with the species, and let us confine ourselves to the 

 mammals which stand nearest to man. 



There can be no doubt that animals even in a wild state 

 pair or endeavour to copulate with races not allied to their 

 own, such is especially the case with males driven away by 

 stronger rivals, who, in the impossibility of gratifying the 

 sexual desire with females of their own species, pair with those 

 of other species with whom they frequently come in contact. 

 This phenomenon resembles that of the adoption of the young 

 of other species by a mother deprived of her own progeny. 

 Connexions of this kind have been observed between dog and 

 swine, stag and cow ; but it was always found that in species 

 so remote from each other there was no issue, which is fre- 

 quently impossible from incompatible organic structure. We 

 may, therefore, from actual observation, consider it as a law, 

 that copulation between remote species differing in structure 

 is either impossible, or, at all events, sterile. 



AUied species may copulate and produce bastards. This is 



