286 Evolution and Adaptation 
the questions of variation which were raised in the preceding 
pages. It should be pointed out, however, that it would be 
premature to do more than indicate, in the most general 
way, the application of these conclusions. The chief value 
of Mendel’s results lies in their relation to the theory of in- 
heritance rather than to that of evolution. 
In the first place, Mendel’s results indicate that we cannot 
make any such sharp distinction as Darwin does between 
the results of inheritance of discontinuous and of continu- 
ous variations. As Mendel’s results show, it is the separate 
characters that must be considered in each case, and not 
simply the sum total of characters. 
The more general objection that Darwin has made may 
appear to hold, nevertheless. He thinks that the evolution of. 
animals and plants cannot rest primarily on the appearance 
of discontinuous variations, because they occur rarely and 
would be swamped by intercrossing. If Mendel’s law ap- 
plies to such cases, that is, if a cross were made between 
such a sport and the original form, the hybrid in this case, if 
self-fertilized, would begin to split up into the two original 
forms. But, on the other hand, it could very rarely happen 
that the hybrid did fertilize its own eggs, and, unless this oc- 
curred, the hybrid, by crossing with the parent forms in each 
generation, would soon lose all its characters inherited from 
its “sport” ancestor. Unless, therefore, other individuals 
gave rise to sports at the same time, there would be little 
jchance of producing new species in this way. We see then 
jthat discontinuity in itself, unless it involved infertility with 
the parent species, of which there is no evidence, cannot be 
made the basis for a theory of evolution, any more than can 
individual differences, for the swamping effect of intercross- 
ing would in both cases soon obliterate the new form. If, 
however, a species begins to give rise to a large number of 
individuals of the same kind through a process of discontinu- 
ous variation, then it may happen that a new form may 
