HYBRIDS AND MONGRELS COMPARED. 287 



HYBRIDS AND MONGRELS COMPARED, INDEPENDENTLY OF 



THEIR FERTILITY. 



Independently of the question of fertility, the offspring 

 of species and of varieties when crossed may be compared in 

 several other respects. Gartner, whose strong wish it was to 

 draw a distinct line between species and varieties, could find 

 very few, and, as it seems to me, quite unimportant differ- 

 ences between the so-called hybrid offspring of species, and 

 the so-called mongrel offspring of varieties. And, on the 

 other hand, they agree most closely in many important 

 respects. 



I shall here discuss this subject with extreme brevity. 

 The most important distinction is, that in the first genera- 

 tion mongrels are more variable than hybrids ; but Gartner 

 admits that hybrids from species which have long been cul- 

 tivated are often variable in the first generation ; and I 

 have myself seen striking instances of this fact. Gartner 

 further admits that hybrids between very closely allied spe- 

 cies are more variable than those from very distinct species ; 

 and this shows that the difference in the degree of variabil- 

 ity graduates away. When mongrels and the more fertile 

 hybrids are propagated for several generations, an extreme 

 amount of variability in the offspring in both cases is noto- 

 rious ; but some few instances of both hybrids and mongrels 

 long retaining a uniform character could be given. The 

 variability, however, in the successive generations of mon- 

 grels is, perhaps, greater than in hybrids. 



This greater variability in mongrels than in hybrids does 

 not seem at all surprising. For the parents of mongrels are 

 varieties, and mostly domestic varieties (very few experi- 

 ments having been tried on natural varieties), and this 

 implies that there has been recent variability, which would 

 often continue and would augment that arising from the act 

 of crossing. The slight variability of hybrids in the first 

 generation, in contrast with that in the succeeding genera- 

 tions, is a curious fact and deserves attention. For it bears 

 on the view which I have taken of one of the causes of 

 ordinary variability, namely, that the reproductive system, 

 from being eminently sensitive to changed conditions of life, 

 fails under these circumstances to perform its proper funo* 

 tion of producing offspring closely similar in all respects to 

 the parent form. Now, hybrids in the first generation are 



