Variation and Heredity 269 
new and the old forms are fertile, the hybrids may be like 
one or the other parent, as in several cases to be given later. 
Not that I mean to say that in either of these two ways can we 
really offer a solution of the question of infertility, for, from 
the evidence that we possess, it appears improbable that the 
infertility of species zwzer se has been the outcome of either 
of these causes. 
In support of his main thesis Pearson gives certain data in 
respect to preferential mating in the human race. By this is 
meant that selection of certain types of individuals is more 
likely to take place, and also that the fertility of certain types 
of individuals is greater than that of other types. The cal- 
culations are based on stature, color of hair, and of eyes. 
The results appear to show in all cases examined that there 
is a slight tendency to form new races as the result of the 
more frequent selection of certain kinds of individuals. But 
even if this is the case, what more do the results show than 
that local races may be formed,—races having a certain 
mode for height, for color of eyes or of hair? That changes 
of this kind can be brought about we knew already without 
any elaborate measurements, yet we should not conclude from 
this that new species will be formed by a continuation of the 
process. . 
Pearson writes: “As to the problem of evolution itself we 
are learning to see it under a new light. Natural selection, 
combined with sexual selection [by which Pearson means 
segregation of certain types through individual selection ] 
and heredity, is actually at work changing types. We have 
quantitative evidence of its effects in many directions.” Yes! 
but no evidence that selection of this sort can do anything 
more than keep up the type to the upper limit attained in 
each generation by fluctuating variations. Pearson adds, 
“ Variations do not occur accidentally, or in isolated instances ; 
autogamic and assortive mating are realities, and the problem 
of the near future is not whether Darwinism is a reality, but 
