therefore apparent. Instead of this district being overcrowded and that one deserted; instead of there being too many of one sex here and too few of the other sex there; instead of a high percentage of individuals failing to procreate their kind, just because circumstances over which they have no control prevent their discovering one another at the appropriate time—each sex has its allotted part to play, each district has its allotted number of inhabitants, and the waste of energy and the loss of time incurred in the process of mating is reduced to a minimum.
Let us return again to the question of fortuitous mating, and consider the position of a male and female that have discovered one another by accident and have paired; what will be the subsequent course-of their behaviour? We are assuming, of course, that a territory forms no part of their life - history. If the discharge of the sexual function takes place immediately and the ovaries of the female are in an advanced state of seasonal development, the construction of the nest will proceed without delay—and the nest will answer the same purpose as the territory in so far as it serves to restrict the movements of the birds and tends to make them remain in, or return to, its vicinity; but if not, there will be an interval during which both sexes will continue to wander as before, guided only by the scarcity or abundance of food. In the first case, there will be the attraction of the nest to prevent any untimely
