ended, how can this be? An answer to the question will be found in the fact that a bird has an innate capacity to return to the neighbourhood of its birthplace, or to the place wherein it had previously reared offspring—which means that the results of prior process persist as the basis and starting-point of subsequent process.
Bearing then in mind that the seeming peace in bird life around us in the spring is but the expression of transitory adjustments in the distribution of individuals and of species; bearing in mind how widespread is the search for isolation each recurring season, how frequently the search leads to competition and competition to failure, and how failure implies a renewal of the search; bearing in mind that situations, which appear to be eminently suitable for breeding purposes, are passed by year after year and remain unoccupied, just because, for reasons which have yet to be ascertained, the environment fails to supply some condition which is essential if the inherited nature of the bird is to respond—can there be any doubt that the general result of the functioning of the disposition will be expansion; or, since no limit is placed upon it from within but only from without—that is, by unfavourable circumstances in the external world, that the expansion will not merely be in one direction but in every direction?
If now, when reproduction is ended, all the impulses relating to it die away, and the
