48 THE ORIGIN OF SPECIES 



Such alone are the unimportant differences which 

 Gartner is able to point out between hybrid and mon- 

 grel plants. On the other hand, the degrees and kinds 

 of resemblance in mongrels and in hybrids to their re- 

 spective parents, more especially in hybrids produced 

 from nearly related species, follow according to Gartner 

 the same laws. When two species are crossed, one has 

 sometimes a prepotent power of impressing its likeness 

 on the hybrid. So I believe it to be with varieties of 

 plants; and with animals one variety certainly often has 

 this prepotent power over another variety. Hybrid plants 

 produced from a reciprocal cross generally resemble each 

 other closely; and so it is with mongrel plants from a 

 reciprocal cross. Both hybrids and mongrels can be re- 

 duced to either pure parent-form, by repeated crosses 

 in successive generations with either parent. 



These several remarks are apparently applicable to 

 animals; but the subject is here much complicated, partly 

 owing to the existence of secondary sexual characters; 

 but more especially owing to prepotency in transmitting 

 likeness running more strongly in one sex than in the | 

 other, both when one species is crossed with another, 

 and when one variety is crossed with another variety. 

 For instance, I think those authors are right who main- 

 tain that the ass has a prepotent power over the horse, 

 so that both the mule and the hinny resemble more 

 closely the ass than the horse; but that the prepotency 

 runs more strongly in the male than in the female 

 ass, so that the mule, which is the offspring of the 

 male ass and mare, is more like an ass, than is the 

 hinny, which is the offspring of the female ass and 

 stallion. 



