CROSS-BREEDING AND INBREEDING 301 



A number of other Equus hybrids have been produced. The horse 

 has been crossed with the now extinct quagga (E. quagga) and with 

 several species of zebras. And the zebras have been crossed with 

 asses. No particular use has been made of such hybrids. 



Cattle hybrids. — -There are many species of the genus Bos. The 

 auroch is designated Bos taurus primegenus. The now extinct wild 

 ox of Europe, supposed to be the ancestor of European cattle, is called 

 Bos taurus. The characteristic humped cattle of India is known as 

 Bos indiais. The wild ox of Java is called Bibos sondaicus, and hence 

 belongs to a different genus. The bison of Europe and the closely 

 related American bison are called, respectively, Bison bonasus and 

 Bison bison. There are three species of buffalos belonging to the genus 

 Bubalns. Various hybrids, both interspecific and intergeneric, have 

 been made by crossing these and other species of cattle-like animals. 

 Hybridization of European and Brahman cattle, or zebus (Bos indicus), 

 has been carried on very successfully in the southern states, especially 

 in Texas and Louisiana. The hybrids are vigorous, and both sexes are 

 fertile. The F x hybrids are predominantly of the European breed, 

 with only the suggestion of the zebu hump and much less of the hang- 

 ing dewlap than in pure zebus. When the Fi individuals are interbred, 

 there is a great deal of variation among the F 2 offspring, of which no 

 satisfactory analysis has yet been made. The chief advantage de- 

 rived from introducing the zebu strain into American cattle is that 

 zebus are immune to Texas fever, and hybrids with as low as one-eighth 

 zebu blood are also immune to this most serious of cattle diseases. 



Bisons and European cattle have been successfully crossed, the 

 cross usually made being between cattle cows and bison bulls. The 

 cross is successful only in a small percentage of cases, and very fre- 

 quently both dam and calf are lost. The sex ratio of these hybrids is 

 very unequal, the ratio being at one time 33 females to 6 males. 

 Usually the Fi males are sterile, but the females are fertile and may be 

 back-crossed to bison bulls or cattle bulls as desired, and there is no 

 difficulty or danger of loss of life as in the F r cross. Animals that are 

 the product of various grades of admixture of bison and cattle are 

 called catialos. It is expected that, by selection, a desirable hybrid 

 type may be fixed, combining the best features of both genera. 



Fowl hybrids. — The domestic fowl is commonly designated Gallus 

 domesticus and is believed to have been derived from one or more of 

 several wild species of the genus Gallus. Four wild species are recog- 

 nized: G. gallus, the red jungle fowl of northern India, Malay states, 



