HYBRIDS AND MONGRELS COMPARED. 307 



than hybrids to revert to either parent form; but this, if it 

 be true, is certainly only a difference in degree. More- 

 over, Gartner expressly states that the hybrids from long 

 cultivated plants are more subject to reversion than 

 hybrids from species in their natural state; and this prob- 

 ably explains the singular difference in the results arrived 

 at by different observers. Thus Max Wichura doubts 

 whether hybrids ever revert to their parent forms, and he 

 experimented on uncultivated species of willows, while 

 Naudin, on the other hand, insists in the strongest terms 

 on the almost universal tendency to reversion in hybrids, 

 and he experimented chiefly on cultivated plants. Gilrtner 

 further states that when any two species, although most 

 closely allied to each other, are crossed with a third species, 

 the hybrids are widely different from each other; whereas 

 if two very distinct varieties of one species are crossed with 

 another species, the hybrids do not differ much. But this 

 conclusion, as far as I can make out, is founded on a 

 single experiment, and seems directly opposed to the 

 results of several experiments made by Kolreuter. 



Such alone are the unimportant differences which 

 Gartner is able to point out between hybrid and mongrel 

 plants. On the other hand, the degrees and kinds of re- 

 semblance in mongrels and in hybrids to their respective 

 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 

 prepotefat power of impressing its likeness on the hybrid. 

 So I believe it to be with varieties of plants; and with ani- 

 mals, 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 reduced to either pure parent 

 form by repeated crosses in successive generations with 

 either parent. 



These several remarks are apparently applicable to ani- 

 mals, but the subject is here much complicated, partly 

 owing to the existence of secondary sexual characters, but 

 more especially owing to prepotency in transmitting like- 

 ness running more strongly in one sex than in the other, 

 both when one species is crossed with another and when 



