534 GENETICS IN RELATION TO AGRICULTURE 
few males have been born and these have always proved sterile. The 
hybrids are apparently very uniform. The female hybrids appear to have 
no difficulty in parturition when bred to domestic bulls or bison bulls. 
Fic. 208:—An F, hybrid between a bison bull and an Aberdeen-Angus cow. Note polled 
character. (From Journal of Heredity.) 
Fia. 209.— Quinto Porto, five-eighths buffalo, three-cighths polled Hereford. A fertile bull 
which displays the characters of both species. (From the Journal of Heredity.) 
When bred to bison bulls, the three-fourths hybrids which are produced 
are intermediate between the bison and the hybrid, and one-fourth 
hybrids produced by breeding an F’; female to a domestic bull are inter- 
mediate between the hybrid and domestic cattle. Bulls of these two 
Digitized by Microsoft® 
