HYBRIDIZATION IN ANIMAL BREEDING 521 
gayal, Bebos frontalis; with the gaur, Bibos gaurus; with the zebu, Bos 
indicus, and with the American bison, Bison americanus. Apparently 
all these hybrids are fertile in the female sex, and sterile in the male. 
They are commonly more vigorous than the parents, and in some cases 
they provide a source for breed improvement for specific purposes. 
These features are discussed in the next following chapter, in which 
illustrations also will be found. 
Many other species hybrids have been reported among domestic 
animals. Thus there are persistent reports of hybrids between the sheep 
and goat. In fowls a great variety of strange hybrids have been pro- 
duced. Brentana lists thirteen remarkable hybrids in the Phasianide 
among them peacock-guinea fowl, pheasant-fowl, guinea fowl-fowl, 
and various pheasant species crosses. Although of technical interest these 
-hybrids do not promise to yield anything of commercial value. 
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