272 
HYBKIDISM. 
Chap. YIII. 
external characters in the production of the most dis¬ 
tinct domestic varieties, and from not wishing or being 
able to produce recondite and functional differences in 
the reproductive system; from these several consider¬ 
ations and facts, I do not think that the very general 
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 
liave 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 
