has come under the influence of sexual selection, it is the one sex only—almost always the male—that has been modified by its action, is a correct one. It seems to me more probable that where the sexes are alike, or where they differ markedly, and are both handsome, each of them has acquired such beauty as it possesses in accordance with the taste and choice of the opposite one. Darwin, though he did not consider this probable, yet recognised its possibility, as the following passage will show: "It may be suggested that in some cases a double process of selection has been carried on: that the males have selected the more attractive females, and the latter the more attractive males. This process, however, though it might lead to the modification of both sexes, would not make the one sex different from the other, unless, indeed, their tastes for the beautiful differed; but this is a supposition too improbable to be worth considering in the case of any animal excepting man. There are, however, many animals in which the sexes resemble each other, both being furnished with the same ornaments, which analogy would lead us to attribute to the agency of sexual selection. In such cases it may be suggested with more plausibility that there has been a double or mutual process of sexual selection, the more vigorous and precocious females selecting the more attractive and vigorous males, the latter rejecting all except the more attractive females. But from what we know of the habits of animals this view is hardly probable, for the male is generally eager to pair with
