Fertile Mammalian Hybrids 



" Gordon's currant," which is considered to be a 

 hybrid between the Californian and the Missouri 

 species. He also gives Cytisus adami as an 

 absolutely sterile hybrid, this being a cross 

 between two species of Labernum the common 

 and the purple. 



In the case of animals the known hybrids are 

 so much less numerous that we are able to furnish 

 a list which may be taken as fairly exhaustive. 



FERTILE MAMMALIAN HYBRIDS 



Taking the mammals first, we find that, in 

 addition to those cited by Darwin, there are 

 several recorded cases of crosses between well- 

 defined species which are fertile. 



There is the hybrid between the brown bear 

 and the polar bear, which is perfectly fertile. In 

 the London Zoological Gardens there is a speci- 

 men of this hybrid, also one of this individual's 

 offspring by a pure polar bear. 



The stoat has been crossed with the domestic 

 ferret, a descendant of the polecat, a very distinct 

 species ; the resulting hybrids have nevertheless 

 proved fertile. 



The bull American bison produces with the 

 domestic cow hybrids known as " cataloes," 

 which are fertile. The reverse cross of the 

 domestic bull with the bison cow does not, how- 

 ever, succeed at all, which reminds us of what 

 happens in the case of finch-hybrids. 



119 



