HISTORICAL AND EXPERIMENTAL STUDY OF HOMING. 21 



of departure. The point of departure is a landmark (repere) forcibly known to 

 us, since we go directly from it. By remembering all of our displacements 

 since our departure we remain, after a fashion, in continual contact with this 

 point. Whenever we are distant from it we strive, without keeping detailed 

 accounts of these displacements (even unconsciously), to maintain at every 

 moment the notion of its direction with reference to the course of our dis- 

 placements. The consciousness of the point of departure is a fundamental base 

 and suffices for all our operations. The idea of its orientation, that is to say, 

 of its displacement with reference to us, increases in clearness just in propor- 

 tion as we feel that we are displaced with reference to it. This idea is furnished 

 by the operation of the sense of total "aptitude" (aptitudes totales),thQ ampullar 

 sense of our 3 labyrinthian canals (" . . . le sens ampullaire de nos trois 

 canaux labyrinthiques") . The memory which supplies this notion fixes it and 

 preserves it just in the proportion that memory itself develops. This 

 memory is but an aptitude, not more astonishing than many others, and it is 

 natural that this aptitude should have acquired, by hereditary accumulations, 

 an extraordinary power in the species in which the exercise of this instinct is 

 a condition of survival and an important factor in evolution. 



We have given above as faithful a presentation as we can gather of Bonnier's 

 position. We have attempted where possible to give a free translation of his 

 writing. So far as he advances the hypothesis of orientation by appeal to dis- 

 placement, we presume Reynaud would agree with him. Bonnier then advances 

 the idea that individual birds differ in their capacity to orient, as follows: 



The homing pigeon, transported in a basket, holds fast to the memory of the direction of 

 the point of departure (in spite of the various successive passive displacements). Arrived 

 at the point of release, he has not for a moment lost the precise notion of the component 

 displacements or of the total displacement. This notion, condensed by memory, is like the 

 thread of Ariane which he attached to his point of departure. If he is not quite sure of 

 himself he retraces stage by stage the road which bore him to the distant point but if he is 

 expert in distant orientation, he holds directly to the thread in place of following its twists 

 and turns. He relies upon direct orientation, on the notion of the point of departure, an 

 idea which he guards in proportion to his displacement, relying among all these detours only 

 upon this constant idea of the sense of return, or orientation from the point of departure 

 [i.e., as we understand Bonnier, the bird resorts to a kind of triangulation process]. It is to 

 be presumed that expert birds in distant orientation have a more highly organized hereditary 

 memory. 



Bonnier's aptitude or displacement theory, if such we may call it, must be 

 looked upon as a suggestion, and one which is extremely vague at that. 



REFLEX THEORIES ASSUMING MAGNETIC SENSIBILITY. 



Viguier,* basing his views upon the " absurdity " of supposing that a bird 

 can fly high enough to perceive its cote when at long distances at sea, and that 

 migrating fish can run their course through vision or smell, maintains that the 

 physical force which enables animals to direct their course must be everywhere 

 present, "in the heights of the atmosphere as well as in the depths of the sea." 

 This force is terrestrial magnetism. To the objection (already raised by Dar- 

 win) that a compass without a chart avails but little, Viguier replies: 



Is this objection insurmountable? I think not. The compass gives to our mariners a 

 simple direction. They need to know the angle that this direction makes with their route 



*Viguier, C., Revue Philosophique, 14, p. 11. 



