278 HYBKIDISM. Chap. VIIL 
versally, fertile. Nor is this nearly general and perfect 
fertility surprising, when we remember how liable we are 
to argue in a circle with respect to varieties in a state 
of nature ; and when we remember that the greater 
number of varieties have been produced under domesti¬ 
cation by the selection of mere external differences, and 
not of differences in the reproductive system. In all 
other respects, excluding fertility, there is a close gene¬ 
ral resemblance between hybrids and mongrels. Finally, 
then, the facts briefly given in this chapter do not seem 
to me opposed to, but even rather to support the view, 
that there is no fundamental distinction between species 
and varieties. 
