26 INTERMIXTURE OF CERTAIN RACES 



tion of the species, and provided it can repair the loss at every 

 generation, the crossing would still be eugenesic, nor would 

 it cease being so, even if the breed were only half as strong as 

 their parents, and only half as long-lived. 



When, therefore, a physiologist wishes to demonstrate the 

 existence of that degree of hybridity which we have termed 

 eugenesic, he selects two perfectly recognised distinct species 

 of animals, crosses them, studies their breeds, and if he finds 

 that they are indefinitely prolific, it is sufficient for him to affirm 

 the existence of engenesic hybridity that is to say, that the 

 physiological definition of the species is unacceptable. But 

 when a zoologist, in studying two races of animals, the specific 

 determination of which is still contested, endeavours to estab- 

 lish that these two races are merely varieties of the same 

 species, and when in order to weaken the differential anatomi- 

 cal characters pointed out by his adversaries, he invokes the 

 physiological analogy exhibited by intermixture, we have a 

 right to expect more than a partial demonstration. We must 

 first prove that the intermixture of the two races constitutes a 

 case of eugenesic hybridity ; for if the cross-breed are not be- 

 tween themselves indefinitely prolific, it is certain that the two 

 races are not of the same species. This first point being es- 

 tablished, would not yet lead to any conclusion, since animals 

 of different species may engender eugenesic breeds. He must, 

 therefore, completely analyse all the phenomena of reproduc- 

 tion and prove that they are exactly the same in the parent 

 races and in the hybrid race. It is not merely the sexual ana- 

 logy but the sexual identity which must be rendered evident ; 

 for from his point of view, it is not sufficient that the two races 

 in question should be homogenesic in some degree, they must 

 be entirely homogeneous, and the least genital difference be- 

 comes an argument against the proposition he sustains. If the 

 cross-breed, though very prolific, are less so than their parents, 

 or less productive in their crossings than their direct alliances; 

 or, finally, if the investigation of these crossings exhibits any 

 functional inequality, it might become very probable that the 

 two races do not belong to the same species. Such would also 

 be the case if the cross-breed were less strong and vivacious 



