HYBKIDS IN CONFINEMKNT. 353 



intended by nature to be capable of actual sexual union. Hence 

 the opponents of Darwin's theory — maintaining, as they do, the 

 immutability of species — have always denied the occurrence of 

 hybrids, or have declared that even if they could occur the ofi"- 

 spi'ing of such an unnatural union must inevitably prove barren, 

 or, finally, that the fertility of the progeny of a successful case 

 of hybridisation affords a proof in itself that the animal forms 

 previously regarded as distinct species must henceforth be con- 

 sidered a mere variety of the same species. 



The importance of the subject induces me to pass the facts 

 briefly under review. 



In the first place, it must be stated that those persons who 

 deny, even now, the general possibility of hybridisation, by that 

 very denial display their ignorance of the subject. It is simple 

 folly, in the face of the increasing number of cases of successful 

 hybridisation in our Zoological Gardens, to insist on maintain- 

 ing this negative position. Hybrids are already known to us in 

 the most widely dissimilar classes of the animal kingdom. 

 Among apes, CynocepJialus mormon and Macacus cynomolgua 

 have crossed and produced young ; the hybrid race of Lepoiidse, 

 a cross between the rabbit and the hare, is very generally 

 known ; the tiger has bred with the lion, the leopard with the 

 jaguar, the polar bear with the brown bear, the masked pig 

 with the common Berkshire pig, Dania vulgaris with Dama 

 tnesopotamica, Equus onager with Equus hemippus, Equus 

 BurcheUi with the common horse, and then again with the 

 common ass and Equus hemionus, and all these crossed couples 

 have repeatedly given bii-th to ofispring. Quite lately a 

 hybrid snake was born in the Zoological Gardens in London, a 

 cross between Ghilobothrus inornatus and Epicrates angulifer. 

 Among ducks hybrids are extremely common; Anas sponsa 

 crosses with Fulicula ferina and nyrocca, Anas boschas with 

 Anas crecca. Among fishes hybridisation between two species 

 of carp or of trout is very easily effected.* Hybrids of inver- 

 tebrate animals are less common ; this, however, may be because 

 they have been less experimented on by man, or because they 

 have generally attracted less attention than the vertebrata. 

 * Salmo sahtelinus and S.fano; Cyprinus carino and C. carasmis. 



