576 GENETICS IN RELATION TO AGRICULTURE 



allelomorphic pair shall be dominant or recessive; and that this influence 

 becomes stronger when large sets of factors determine a particular 

 character. 



Greater Prepotency of the Male. There has been a decided tendency 

 to credit the male with greater prepotency than the female. Many 

 investigators have pointed out that extra-biological influences such as 

 the more rigid choice of males and the greater opportunity they have 

 for impressing offspring may account for this belief among animal 

 breeders. Some of the statistical evidence which Pearson has collected 

 on this point seems to indicate no constant behavior in this respect. At 

 the same time it should be noted that phenomena of sex-linkage and 

 crossing-over may play an important role here. The operation of the 

 former we see in Pearl's investigations of fecundity in fowls. Here the 

 male is obviously the more prepotent with respect to the transmission 

 of fecundity. The operation of the latter we see in Drosophila experi- 

 ments Here there is no crossing-over in the male, as a consequence of 

 which hybrid males more often transmit the particular set of factors 

 which determine a phenotype like their own than do hybrid females. 

 While the possibility of extending this phenomenon to mammals appears 

 to have been destroyed by Castle's work with rats, which demonstrated 

 the occurrence of crossing-over in the male, nevertheless as a possible 

 factor in relative prepotency of the sexes it should not be ignored. 



Conclusions with respect to prepotency. For the present then we 

 must regard prepotency as an established fact, a phenomenon which has 

 not yet been subjected to scientific analysis. From a biological stand- 

 point, however, it is clear that even with our present restricted knowledge 

 there is room for prepotency based upon the existence of different kinds 

 of relations between factors. 



