In sexual selection by preferential mating, even if we follow Professor Groos in believing that it is a special mode of natural selection, the conscious situation is essential. If we accept the theory in any form, we must regard the adornments, antics, and display of the male as an appeal in some way to the consciousness of the female, whatever particular form the effects in that consciousness may take, whether the appeal evoke a sense of beauty, or simply be a means of exciting to the consummation of the natural end of courtship. Even if we follow Mr. Wallace in regarding plume and song as “recognition marks,” it is only by their appeal to consciousness in this way, if in no other, that they are of any biological value. And this, of course, applies equally to the whole range of his theory of recognition marks--their sole utility lies in their being a stimulus to consciousness through which the end of recognition is secured. So, too, not only the specialized behaviour which we dignify by the name of “courtship,” but every case in which mate is drawn to mate through sight, smell, hearing--any of the leading senses--testifies to the importance of consciousness in furthering an end of supreme biological importance. And if, as Darwin urged, the “law of battle” among the males co-operates with preferential mating, as we can hardly deny, in securing strong, vigorous, and healthy fathers of the generation they beget, here, too, consciousness is an important factor. Can we conceive a “law of battle” among unconscious beings? If success in the combat were a mere matter of brute strength, it would imply some consciousness in its dull exercise. But it is more. It is also a trial of skill. Were it not so our forefathers would not have spent hours in watching a cock-fight, or laid heavy odds on their particular “fancy.”