160 DARWINISM chap. 



has received decisive evidence that the hybrids between these 

 are perfectly fertile inter se. 



Dogs have been frequently crossed with wolves and with 

 jackals, and theii- hybrid ottspring have been found to be fertile 

 inter se to the third or fourth generation, and then usually to 

 show some signs of sterility or of deterioration. The wolf 

 and dog may be originally the same species, but the jackal is 

 certainly distinct ; and the appearance of infertility or of weak- 

 ness is probably due to the fact that, in almost all these experi- 

 ments, the ofispring of a single pair — themselves usually from 

 the same litter — were bred in-and-in, and this alone sometimes 

 produces the most deleterious effects. Thus, Mr. Low in his 

 great work on the Domesticated Animals of Great Britain, 

 says : "If we shall breed a pair of dogs from the same litter, 

 and unite again the offspring of this pair, we shall produce at 

 once a feeble race of creatures ; and the process being repeated 

 for one or two generations more, the family will die out, or be 

 incapable of propagating their race. A gentleman of Scotland 

 made the experiment on a large scale with certain foxhounds, 

 and he found that the race actually became monstrous 

 and perished utterly." The same writer tells us that hogs 

 have been made the subject of similar experiments : " After a 

 few generations the victims manifest the change induced in the 

 system. They become of diminished size ; the bristles are 

 changed into hairs ; the limbs become feeble and short ; the 

 litters diminish in frequency, and in the number of the young 

 produced ; the mother becomes unable to nourish them, and, 

 if the experiment be carried as far as the case will allow, the 

 feeble, and frequently monstrous offspring, will be incapable of 

 being reared up, and the miserable race will utterly perish. "^ 



These precise statements, by one of the greatest authorities 

 on our domesticated animals, are sufficient to show that the 

 fact of infertility or degeneracy appearing in the oflspring of 

 hybrids after a few generations need not be imputed to the 

 fact of the first parents being distinct species, since exactly the 

 same phenomena appear when individuals of the same species 

 are bred under similar adverse conditions. But in almost all 

 the experiments that have hitherto been made in crossing 

 distinct species, no care has been taken to avoid close inter- 



^ Low's Domesticated Animals of Great Britain, Introduction, p. Ixiv. 



