THE SENSE OF DIRECTION. 49 



proven ability of animals to return safely home though they are 

 carried in closed receptacles on the outward journey, through a 

 country they cannot possibly know. Bonnier, with regard to 

 human orientation, considered that a knowledge and memory 

 of all the series of displacements, since the point of departure 

 was left, are sufficient to keep us constantly in touch with this 

 point, or we may exert ourselves, perhaps unconsciously, to 

 maintain always the notion of its direction in the course of our 

 displacement, but without preserving a memory of our succes- 

 sive displacements. So many instances are known of animals 

 returning by a different route from that along which they set out, 

 or were carried, that a memory of the successive displacements 

 may be dismissed as unnecessary. The alternative proposed by 

 Bonnier is more in keeping with the facts as they are known to 

 occur in animals. As each displacement occurs and is sensed, 

 the bearing of the point of departure is readjusted in terms of 

 the extent and direction of the displacement, but a memory 

 of the displacement is not necessarily retained, and there is no 

 subsequent readjustment in terms of memory. There may thus 

 be a constant knowledge of the position of the point of departure, 

 but there must evidently be a limit to the formation of associa- 

 tions on this basis, just as much as there is to the formation of 

 associations on the basis of landmarks. 



While Bonnier's theory is the most probable expression 

 of the mechanism of the first component, the theory contri- 

 butes nothing to the working of the second component. The 

 superlative need of being able to keep a true course is in- 

 disputable. The ability is wonderfully developed in flying 

 insects and birds, and it plays no inconsiderable part in 

 successful orientation. 



The Canary's cage stood in a window recess and was always 

 clearly lighted for a considerable time after sunset, but the 

 room was apt to grow rapidly dim. Observations extending 

 over several years proved that the Canary had then considerable 

 difficulty in returning to its cage, that it frequently failed to 

 keep a true course, and that it circled the room repeatedly. 

 This result speaks for visual impressions as a factor in the 

 perfection of the second component of the sense of direction. 



I have already quoted some observations to show that the 



