Thus we are led back to sexual selection. If we are satisfied that the males of certain species do as a matter of fact behave in specific and distinguishable ways at the breeding season, and in presence of their would-be mates, the question is, What, if any, is the biological value of such behaviour? What has fostered and guided it in the course of its evolution? From the case of the Argus pheasant, which is only a sample of the large class of cases in which the male has special adornments, we see that the behaviour has often direct relation to the display of such plumage, or, in some apes, of coloured surfaces, so that behaviour and ornamentation must be taken together. The essence of Darwin’s contention is, that the adornments and behaviour give rise to a situation through which the female is stimulated or excited to accept the male; that the male in which they are best developed gives rise to the most effective situation, produces most excitement, and therefore has the best chance of acceptance, being “unconsciously preferred;”[141] and that he thus begets offspring which inherit his adornments and modes of behaviour, such inheritance being, however, confined to the males. Thus sexual selection takes effect through preferential mating, whereby certain hereditary traits are transmitted and become racial characteristics. And this is brought about through an appeal to consciousness, and seems to involve choice--generally that of the female. Now, as I have elsewhere urged,[142] the hypothesis of sexual selection has often been placed in a false light by the introduction of the unnecessary supposition that the hen bird, for example, must possess a standard or ideal of æsthetic value, and that she selects that singer which comes nearest to her conception of what a songster should be. Darwin occasionally expressed himself unguardedly in the matter; he says, for example, that the female appreciates the display of the male, and places to her credit a taste for the beautiful.[143] But he also distinctly states that “it is not probable that she consciously deliberates; she is most excited or attracted by the most beautiful, or melodious, or gallant males.”[144] This is all that is really necessary for the theory of sexual selection. The hen accepts that mate which by his song or otherwise excites in sufficient degree the pairing impulse; if others fail to excite this impulse, they are not accepted. Even Mr. A. R. Wallace, who rejects the theory save in a very subordinate form, says[145] that “it may be admitted, as highly probable, that the female is pleased or excited by the display,” and speaks[146] of a possible choice of “the most vigorous, defiant, and mettlesome male,” giving, moreover,[147] several telling examples of preferential mating. Stripped of all its unnecessary æsthetic surplusage, at any rate so far as this implies an æsthetic ideal, or æsthetic motive, the hypothesis