6. The development, or the presence, of the æsthetic feeling in the selecting sex is not accounted for on the theory. There is just as much need to explain why the females are gifted with an appreciation of the beautiful, as that the beautiful colors develop in the males. Shall we assume that still another process of selection is going on, as a result of which those females are selected by the males that appreciate their unusual beauty, or that those females whose taste has soared a little higher than that of the average (a variation of this sort having appeared) select males to correspond, and thus the two continue heaping up the ornaments on one side and the appreciation of these ornaments on the other? No doubt an interesting fiction could be built up along these lines, but would any one believe it, and, if he did, could he prove it? Darwin assumes that the appreciation on the part of the female is always present, and he thus simplifies, in appearance, the problem, but he leaves half of it unexplained. 7. It has been pointed out, that it is important to distinguish between the possible excitement of the female by the display or antics of the male, and the selection of the more beautiful or agile performer. Darwin himself records a few cases, which plainly show that the more beautiful is not always the more successful. It has also been suggested that the battles of the males are sometimes sham performances, and even when they are real, if the less vigorous do not remain to be destroyed but run away, they live to find mates of their own. In fact, the conduct of the males at the breeding season appears to be much more the outcome of their own excitement than an attempt to attract the females. 8. There is another side to the question, the importance of which is so great, that it is surprising that Darwin has not taken any notice of it. If, in order to bring about, or even maintain, the results of sexual selection, such a tremendous elimination of individuals must take place, it is surprising that natural selection would not counteract this by destroying those species in which a process, so useless for the welfare of the species, is going on. It is curious that this has not been realized by those who believe in both of these two hypotheses.