Where, then, shall we look for this other factor, if not in the processes of selection, in the selecting of the most suitable variations among all those which occur? We are confronted with the alternative of either working out a sufficient explanation with this factor, or of giving up the attempt at explanation altogether. Yet the application of the principle of selection in relation to the neuters of colony-forming insects is by no means simple, for, as the workers are sterile, a modification of them through processes of breeding cannot begin directly with themselves. The workers which exhibit the most suitable variations cannot be selected for breeding, but only their parents, the sexual animals, and these according to whether they produce better workers or worse. This is how Darwin looked at the matter, and his view receives support from one peculiarity in the composition of these animal colonies, whose significance becomes apparent in relation to this problem. It has long been known that in a bee-hive there are from 10,000 to 20,000 workers, but only one true female, the so-called queen, and the meaning of this remarkable arrangement probably is, that the adaptation of the workers through natural selection becomes much more easily possible, _since the whole number are the children of a single pair_. It is not the individual workers, but the whole colony, that is, the whole progeny of the queen, which is selected, according to the greater or less degree of effectiveness displayed by the workers. Strictly speaking, it is the single queen that is selected in relation to her power of producing superior or inferior workers. A colony whose queen was unsatisfactory in this respect could not hold its own in the struggle for existence, and only the best colonies and the best hives would survive, that is, through their descendants. If the hive contained a hundred queens instead of a single queen the process of selection would be much more complex and less clear, and it is even quite conceivable that the production of specially modified workers, adapted to their functions, or of two or three different kinds of workers, would not have been possible at all. For it would not have helped much if one out of a hundred females had produced workers of better structure; only a majority of such females could give the colony any advantage as compared with other colonies.