246 
HYBEIDISM. 
Chap, VIII. 
when first crossed^ and the sterility of the hybrids pro¬ 
duced from them. 
Pure species have of course their organs of reproduc¬ 
tion in a perfect condition^ yet when intercrossed they 
produce either few or no offspring. Hybrids^ on the 
other handj have their reproductive organs functionally 
impotent^ as may be clearly seen in the state of the 
male element in both plants and animals; though the 
organs themselves are perfect in structure, as far as the 
microscope reveals. In the first case the two sexual ele¬ 
ments which go to form the embryo are perfect; in the 
second case they are either not at all developed, or are 
imperfectly developed. This distinction is important, 
when the cause of the sterility, which is common to the 
two cases, has to be considered. The distinction has 
probably been slurred over, owing to the sterility in 
both cases being looked on as a special endowment, 
beyond the province of our reasoning powers. 
The fertility of varieties, that is of the forms known 
or believed to have descended from common parents, 
when intercrossed, and likewise the fertility of their 
mongrel offspring, is, on my theory, of equal import¬ 
ance with the sterility of species; for it seems to make 
a broad and clear distinction between varieties and 
species. 
First, for the sterility of species when crossed and of 
their hybrid offspring. It is impossible to study the 
several memoirs and works of those two conscientious 
and admirable observers, Kolreuter and Gartner, who 
almost devoted their lives to this subject, without being 
deeply impressed with the high generality of some de¬ 
gree of sterility, Kolreuter makes the rule universal; 
but then he cuts the knot, for in ten cases in which he 
found two forms, considered by most authors as distinct 
species, quite fertile together, he unhesitatingly ranks 
