HYBRIDS AND MONGRELS COMPARED. 289 



to the existence of secondary sexual characters, but more 

 especially owing to prepotency in transmitting likeness run- 

 ning 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 maintain 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 m the male than in the 

 female ass, so that the mule, which is an 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. 



Much stress has been laid by some authors on the sup- 

 posed fact, that it is only with mongrels that the offspring are 

 not intermediate in character, but closely resemble one of 

 their parents : but this does sometimes occur with hybrids, 

 yet I grant much less frequently than with mongrels. 

 Looking to the cases which I have collected of cross-bred 

 animals closely resembling one parent, the resemblances 

 seem chiefly confined to characters almost monstrous in 

 their nature, and which have suddenly appeared — such as 

 albinism, melanism, deficiency of tail or horns, or additional 

 fingers and toes ; and do not relate to characters which have 

 been slowly acquired through selection. A tendency to 

 sudden reversions to the perfect character of either parent 

 would, also, be much more likely to occur with mongrels, 

 which are descended from varieties often suddenly produced 

 and semi-monstrous in character, than with hybrids, which 

 are descended from species slowly and naturally produced. 

 On the whole, I entirely agree with Dr. Prosper Lucas, who, 

 after arranging an enormous body of facts with respect to 

 animals, comes to the conclusion that the laws of resem- 

 blance of the child to its parents are the same, whether the 

 two parents differ little or much from each other, namely, 

 in the union of individuals of the same variety, or of differ- 

 ent varieties, or of distinct species. 



Independently of the question of fertility and sterility, in 

 all other respects there seems to be a general and close simi- 

 larity in the offspring of crossed species, and of crossed 

 varieties. If we look at species as having been specially 

 created, and at varieties as having been produced by sec- 

 ondary laws, this similarity would be an astonishing fact. 

 But it harmonizes perfectly with the view that there is no 

 essential distinction between species and varieties. 



