Fertile Mammalian Hybrids 
‘“‘Gordon’s currant,” which is considered to be a 
hybrid between the Californian and the Missouri 
species. He also gives Cytzsus adamz 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. 
FertitE Mammatian Hysrips 
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. 
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