In winter, then, the individual loses its individuality and is subordinated to the welfare of the community, whilst in spring it regains its individuality, and all its inherited instincts which then come into operation lead to its isolation from the flock. The impulse to seek isolation is dependent upon internal organic conditions which are peculiar to a certain season; whereas the gregarious impulse depends upon internal organic conditions which inhere at all times, though its functioning is inhibited by the functioning of the former impulse. The evidence which leads to this conclusion is to be found in the fact that a male often deserts its territory temporarily and joins the flock, where it remains at peace with its companions--an aspect of behaviour which we have discussed on various occasions. The former impulse becomes dominant in the spring owing to its innately superior strength; the latter becomes dominant in the autumn because the organic condition which determines the functioning of the former then subsides. The impulse to seek the appropriate breeding ground and to dwell there would seem to be the strongest of all the impulses save one--the sexual. When, however, I speak of the sexual, I refer to the actual discharge of the sexual function, which is the consummation of the whole process. But the territory and all that appertains to it is part of that process--the search for the breeding ground, the dwelling there, and the intolerance of intrusion are but different stages, each one of which must have an impulse peculiar to it; and since the completion of the sexual act can only be successfully accomplished providing that success is attained at every stage, the probability is that, of the impulses concerned, one is neither more powerful nor less powerful than another. So that we have two impulses operating at different seasons and guiding the behaviour into widely divergent channels. But though the proximate end to which the behaviour is directed is apparently different, there are not two biological ends in view, but one--the attainment of reproduction; and the changes that we witness are not contrary but complementary, and their prospective value lies in the circumstance that they contribute towards the preservation of the race.