272 HYBKIDISM. Chap. VIII. 



fertility of varieties can be proved to be of universal 

 occurrence, or to form a fundamental distinction 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 inci- 

 dental 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 gra- 

 duates away. When mongrels and the more fertile 

 hybrids are propagated for several generations an ex- 

 treme amount of variability in their offspring is notori- 



