Organic Evolution , Darwinism and the Genesis of Species. i 7 
accidental occurrence, preservation, and development of vari¬ 
ations resulting simultaneously in these and other cases is 
practically infinite. 
Many other objections, scientific, metaphysical and teleo¬ 
logical, have been offered against the acceptance of natural 
selection as the chief factor in development, which for want 
of time cannot be considered here. A consideration of these 
and the objections above mentioned leads me to the conclu¬ 
sion that while natural selection may be and undoubtedly is 
a factor in development, it is not the chief factor, and cer¬ 
tainly not the only one in the case. 
From the first Darwin was not unaware of the weakness 
of his theory and the criticism it encountered from some 
of the ablest naturalists who rejected it convinced him still 
more of its inadequacy as a whole. He therefore supple¬ 
mented it by a theory of sexual selection which he believed 
would account for much of the specific variation which 
natural selection had proved incapable of explaining. Sexual 
selection is thus defined by Darwin: “It has been shown 
that the largest number of vigorous offspring will be reared 
from the pairing of the strongest and best-formed males, 
vigorous in contests over other males, with the most vigo¬ 
rous and best nourished females, which are the first to breed 
in the spring. If such females select the more attractive, 
and, at the same time, vigorous males they will rear a larger 
number of offspring than the retarded females which must 
pair with the less vigorous and less attractive males . . . 
The advantage thus gained by the more vigorous pairs in 
rearing a larger number of offspring has apparently sufficed 
to render sexual selection efficient.” 
Unquestionably where there is a direct competition for 
the female the weakest males will either be destroyed out¬ 
right or eliminated by reduced opportunity for procreating, 
and consequently there will be a weaker and less numerous 
progeny. But evidence is wanting that any considerable 
number of males is thus debarred from mating, or that the 
vigorous females are exclusively acquired by the vigorous 
