CROSS-BREEDING AND ITS RESULTS. 19 



" The embryo of hybrids," he says, " fre- 

 quently dies prematurely, and if born, seems 

 to be defective in vitality." 1 



He also refers to experiments with eggs 

 of cross-bred fowls, where nearly all the 

 few chickens that emerged from the shell 

 died soon after " without any cause, appar- 

 ently from mere inability to live." 1 



The sterility of some hybrids was not to 

 be anticipated, for if the life-forces of two 

 races are so closely allied that they can 

 combine to produce a hybrid, might it not 

 be expected that the life-forces of the hy- 

 brids, inferentially still more closely allied, 

 would prove more fertile ? 



But uniform experience emphatically nega- 

 tives the inference, even in the case of 

 races so closely allied as our breeds of 

 domestic cattle. 



In this elimination of mongrel stock may 

 we not recognise Nature's hostility to a 

 new type ? 



Attempts have been made, with more or 

 less success, to vary expression of type 

 by intermixture, to a limited extent, of 

 the blood of another breed. 



If a hybrid is bred into the race of 

 either parent, and the progeny again into 



1 Origin of Species, Ed. vi., p. 249. 



