244 ON THE ORIGIN OF SPECIES 



between varieties and species. The general fertility of 

 varieties does not seem to me sufficient to overthrow 

 the view which I have taken with respect to the very 

 general, but not invariable, sterility of first crosses and 

 of hybrids, namely, that it is not a special endowment, 

 but is incidental on slowly acquired modifications, more 

 especially in the reproductive systems of the forms 

 which are crossed. 



Hybrids and Mongrels compared, independently of their 

 fertility. — Independently of the question of fertility, 

 the offspring of species when crossed and of varieties 

 when crossed may be compared in several other respects. 

 Gartner, whose strong wish was to draw a marked line 

 of distinction between species and varieties, could find 

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

 differences 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 

 very many important respects. 



I shall here discuss this subject with extreme brevity. 

 The most important distinction is, that in the first 

 generation mongrels are more variable than hybrids ; 

 but Gartner admits that hybrids from species which 

 have long been cultivated are often variable in the first 

 generation ; and I have myself seen striking instances 

 of this fact. Gartner further admits that hybrids be- 

 tween very closely allied species are more variable 

 than those from very distinct species ; and this shows 

 that the difference in the degree of variability graduates 

 away. When mongrels and the more fertile hybrids 

 are propagated for several generations an extreme 

 amount of variability in their offspring is notorious ; 

 but some few cases both of hybrids and mongrels long 

 retaining uniformity of character could be given. The 

 variability, however, in the successive generations of 

 mongrels is, perhaps, greater than in hybrids. 



This greater variability of mongrels than of hybrids 

 does not seem to me at all surprising. For the parents 

 of mongrels are varieties, and mostly domestic varieties 



