The strife, as we have described it thus far, is a purely selfish struggle. Every point gained is a point favorable to the welfare of the individual animal. But nature is uncommonly careless of the individual unless the advantage gained is also of use to the species as a whole. Very often the life of an animal ceases when provision has been made for its young. The male garden spider may have a long and dangerous courtship, in which the uncertain temper of his ladylove may lead her to bite off four or five of his eight legs. But her ingratitude is not yet complete. He may have barely accomplished his desperate purpose of fertilizing her eggs at all hazards, when she ends the process by eating him. The male bumblebee fertilizes the female in the late summer and then dies. She does not lay her eggs before the next season. So it happens that no bumblebee ever sees its own father, and no father bumblebee ever sees his own children. In the honey bee the male, which has been fortunate enough to fertilize the queen, pays for his honor by death within the hour. Superfluous bachelors, among the honey bees, when the bridal season has passed, are driven from the hive to die of starvation. An animal need not always be successful himself, but it is more essential that he hand down his successful traits to those who come after him. It is more important for the future generation that an animal should have had it in him to do great things, though he himself really have never done them, than that he should have learned to do great things on a meager original endowment. Not what an animal accomplishes is important to his children, but what he has it in him to accomplish. Accordingly Nature is full of devices by which those who have proved their original endowment by winning out in the struggle shall hand on this endowment to a subsequent generation. In other words, Nature is anxious that they may successfully mate. Here we are again on distinctly debatable ground. Darwin himself believed thoroughly in what he called sexual selection. It is the essence of this idea that the males and females have grown unlike, more technically have developed secondary sexual characters, through the choice of the mating pair. It would usually be the more serious loss if accident should come to the female, for she may carry fertilized eggs for some time. Hence, if both sexes may not become attractive, it is usually the male that develops fine colors, ornamental appendages or a captivating voice.