ment of the powers of perception.
Few biologists question that we have here a mode of selection of much
importance, though its influence on psychological evolution often
fails to receive its due emphasis. Mr. Wallace[174] regards it as "a
form of natural selection"; "to it," he says, "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 other characters which arise from the development
of these or are correlated with them." So far there is little
disagreement among the followers of Darwin--for Mr. Wallace, with fine
magnanimity, has always preferred to be ranked as such,
notwithstanding his right, on which a smaller man would have
constantly insisted, to the claim of independent originator of the
doctrine of natural selection. So far with regard to sexual selection
Darwin and Mr. Wallace are agreed; so far and no farther. For Darwin,
says Mr. Wallace,[175] "has extended the principle into a totally
different field of action, which has none of that character of
constancy and of inevitable result that attaches to natural selection,
including male rivalry; for by far the larger portion of the
phenomena, which he endeavours to explain by the direct action of
sexual selection, can only be so explained on the hypothesis that the
immediate agency is female choice or preference. It is to this that he
imputes the origin of all secondary sexual characters other than
weapons of offence and defence.... In this extension of sexual
selection to include the action of female choice or preference, and in
the attempt to give to that choice such wide-reaching effects, I am
unable to follow him more than a very little way."

Into the details of Mr. Wallace's criticisms it is impossible to enter
here. We cannot discuss either the mode of origin of the variations in
structure which have rendered secondary sexual characters possible or
the modes of selection other than sexual which have rendered them,
within narrow limits, specifically constant. Mendelism and mutation
theories may have something to say on the subject when these theories
have been more fully correlated with the basal principles of
selection. It is noteworthy that Mr. Wallace says:[176] "Besides the
acquisition of weapons by the male for the purpose of fighting with
other males, there are some other sexual characters which may have
been produced by natural