Wallace’s Theory 
such weapons on account of their being useless, 
superfluous, or in some way injurious. On the 
contrary, as they are often used by the males for 
various purposes, more especially as a defence 
against their enemies, it is a surprising fact that 
they are so poorly developed, or quite absent, 
in the females of so many animals.” 
We have, we believe, demonstrated that 
Darwin’s theory of sexual selection is unable to 
account satisfactorily for all the phenomena of 
sexual dimorphism. But, as we have seen, it is 
quite possible that sexual selection is a real 
factor of evolution. 
We trust that what we have said will stimu- 
late some leisured naturalist to study the question 
of male and female preference. 
We now pass on to consider briefly some of 
the other attempts that have been made to ex- 
plain the phenomena of sexual dimorphism. 
Wattace’s ExpLaNATION OF SEXUAL 
DISSIMILARITY 
Wallace does not accept the theory of sexual 
selection. He admits that the form of male 
rivalry, which Darwin calls “the law of battle,” 
is ‘‘a real power in nature,” and believes that 
“to it we must impute the development of the 
exceptional strength, size, and activity of the 
male, together with the possession of special 
offensive and defensive weapons, and of all 
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