Seite - 304 - in The Origin of Species

304 ORIGIN OF SPECIES 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 repeated 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 in- creasing. Although I know of hardly any thoroughly well-authen- ticated cases of perfectly fertile hybrid animals, I have reason to believe that the hybrids from Cervulus vaginalis and Ree- vesii, and from Phasianus colchicus with P. torquatus, are perfectly fertile. M. Quatrefages states that the hybrids from two moths (Bombyx cynthia 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 together, produce ofif- spring, which are highly fertile when crossed with one of the parent-species. The hybrids from the common and Chi- nese 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 in- stance 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 or perfectly fertile. With our domesticated animals, the various races when crossed together are quite fertile ; yet in many cases they are descended from two or more wild species. From this fact we must conclude either that the aboriginal parent-species at