244 THE ORIGIN OF SPECIES 



fully tried than with plants. If our systematic arrangements can 

 be trusted, that is, if the genera of animals are as distinct from 

 each other as are the genera of plants, then we may infer that 

 animals more widely distinct in the scale of nature can be crossed 

 more easily than in the case of plants ; but the hybrids themselves 

 are, I think, more sterile. It should, however, be borne in mind, 

 that, owing to few animals breeding freely under confinement, 

 few experiments have been fairly tried; for instance, the canary 

 bird has been crossed with nine distinct species of finches, but, 

 as not one of these breeds freely in confinement, we have no right 

 to expect that the first crosses between them and the canary, or 

 that their hybrids, should be perfectly fertile. Again, with respect 

 to the fertility in successive generations of the more fertile 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, brothers and sisters have usually been crossed in 

 each successive 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. 



Although I know of hardly any thoroughly well-authenticated 

 cases of perfectly fertile hybrid animals, I have reason to believe 

 that the hybrids from Cervulus vaginalis and Reevesii, and from 

 Phasianus colchicus with P. torquatus, are perfectly fertile. M. 

 Quatrefages states that the hybrids from two moths (Bombyx cyn- 

 thia and arrindia) were proved in Paris to be fertile inter se for 

 eight generations. It has lately been asserted that two such distinct 

 species as the hare and rabbit, when they can be got to breed to- 

 gether, produce offspring which are highly fertile when crossed 

 with one of the parent-species. 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 (grand- 

 children 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 Captain 

 Hutton, that whole flocks of these crossed geese are kept in 

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



