finds himself forced to abandon the domain which he has devastated; he emigrates to the plains and leads a wandering life, settling temporarily in such regions as offer abundant game. He picks out in the center of his hunting ground temporary shelters, to which he returns every evening until spring brings him back to the solitudes, where he builds his nest. What guides the bird of prey in this long expedition? Undoubtedly the sense of direction. We can not admit that the bird has a memory sufficiently lasting to retain for many months the recollection of all the irregularities of the ground which mark a course of many thousands of kilometers. All the bird's power of observation is in fact concentrated on one object—the chase. Topography is of no consequence to him. Like a registering machine set going at the moment of departure, the sense of direction notes automatically all the road covered by the bird in his pursuit of prey.
The cormorant and many of the fishing birds sometimes follow for many months the long routes of migrating fishes. Though lost in the midst of the sea, they know well how to return to their homes when their fishing is over.
Naturalists who have studied orientation have very wrongly noticed only one fact—the return to a single home. They have usually attributed this to a knowledge of the locality, founded on long observation. Such a theory gives no explanation of the facts we have just cited. Have we not shown that the law of retracement guides the animal when it wanders away from the known territory, brings him back to a temporary home, and sometimes, after an absence of many months, leads him back to his native region?
VII.
It would be interesting to know whether the theory we have just explained is applicable to man.
An animal's movements are regulated by the law of preservation, which assigns to him an imperative purpose, leaving him a restricted liberty in the choice of means. Man is actuated by the same law, but instinct is not the only determining cause of his action; he is also endowed with reason. While instinct points out to the animal only one course, reason points out to man many solutions; he chooses freely whichever seems best to him. He can even consider the promptings of instinct of no consequence; thus by suicide and Malthusian practices he may set himself in revolt against the law of preservation of himself and his kind.
We have attempted to prove that the action of orientation from a distance depends solely on the function of one organ—the sense of direction—which acts to some extent automatically. If a man who is trying to orient himself calls to his aid both reason and observation, the sense of direction, through lack of exercise, becomes atrophied. This is why a well-informed man, who estimates everything that he
