Cuap. VIII. STEKILITY. 253 



hybrid animals, I hardly know of an instance in which 

 two families of the same hybrid have been raised at the 

 same time from different parents, so as to avoid the ill 

 effects of close interbreeding. On the contrary, bro- 

 thers and sisters have usually been crossed in each suc- 

 cessive generation, in opposition to the constantly re- 

 peated admonition of every breeder. And in this case, 

 it is not at all surprising that the inherent sterility in 

 the hybrids should have gone on increasing. If we 

 were to act thus, and pair brothers and sisters in the 

 case of any pure animal, which from any cause had 

 the least tendency to sterility, the breed would as- 

 suredly be lost in a very few generations. 



Although I do not know of any thoroughly well-authen- 

 ticated cases of perfectly fertile hybrid animals, I have 

 some reason to believe that the hybrids from Cervulus 

 vaginalis and Keevesii, and from Phasianus colchicus 

 with P. torquatus and with P. versicolor are perfectly 

 fertile. The hybrids from the common and Chinese 

 geese (A. cygnoides), species which are so different that 

 they are generally ranked in distinct genera, have often 

 bred in this country with either pure parent, and in 

 one single instance they have bred inter se. This was 

 effected by Mr. Eyton, who raised two hybrids from the 

 same parents but from different hatches ; and from 

 these two birds he raised no less than eight hybrids 

 (grandchildren of the pure geese) from one nest. In 

 India, however, these cross-bred geese must be far 

 more fertile ; for I am assured by two eminently 

 capable judges, namely Mr. Blyth and Capt, Hutton, 

 that whole flocks of these crossed geese are kept in 

 various parts of the country ; and as they are kept for 

 profit, where neither pure parent-species exists, they 

 must certainly be highly fertile. 



A doctrine which originated with Pallas, has been 



