The brilliant mouth-cavity can, of course, only be exhibited by the opening of the bill, and in doing this—in the particular way, and with the accompaniments described in each case—both sexes act alike. In other words, if there is really a conscious display in the matter then each sex displays to the other. What conclusion are we to draw from this? Either, as it appears to me, we must assume that both the male and female equally strive to please one another, or that, while the actions of the male mean something, those of the female mean nothing, or nothing in particular, having been transmitted to her, through him, by those same laws of inheritance which have given her, in these and other cases, his own ornamental plumage, and not in accordance with any principle by virtue of which she has been rendered more and more attractive to him. For, except in some special cases where the female is larger and handsomer than the male, the Darwinian theory does not suppose that the hen bird has been modified to please the taste of the cock, whose eagerness, it is assumed, has made this quite unnecessary.
But any uniformly repeated action is a habit, and habits must bear a relation to the psychology of the being practising them, from which it would seem to follow that whatever be the mental state of the male bird through whom any habit has been transmitted to the female, such mental state, being the cause of such habit, must have been transmitted to her along with it. To suppose, however, that the female acts in a certain
