1 66 THE HOMING FACULTY. 



ception of direction acquired ? I think we must say certainly 

 not by the higher perfection of any sense which homing 

 animals share in common with us. Insects have organs 

 whose functions can only be surmised, and it is conceivable 

 that they are, by their aid, sensitive to waves of motion to 

 which we are insensible ; but birds have no such organs, and 

 if, as I suppose, they are sensitive to such waves of motion, 

 it must be by means of nerves terminating at the surface of 

 the body everywhere, in fact the sense of feeling adapted to 

 the reception of impressions to which our nerves are insen- 

 sible. The conditions require that such waves of motion 

 must be continuous, omnipresent, and always flowing in the 

 same direction around the globe. As far as our knowledge 

 extends, the magnetic earth-current is the only wave-motion 

 which fulfils these conditions. I venture therefore to sug- 

 gest as a plausible hypothesis of the homing faculty in so 

 many of the lower animals, that they are sensitive to the 

 ever-present motion of this current. I assume that it is 

 barely appreciable unless the attention is alert and directed 

 to it, but the observation of their own sensations is easily 

 cultivated in animals which have little else to occupy them. 

 The amount of calculation concerned in keeping the outward 

 reckoning of the course certainly involves greater mental 

 powers than some of you will be willing to ascribe to animals ; 

 but allowing for the facts, first that animal intelligence being 

 developed only in a few narrow grooves, may easily transcend 

 ours at points, secondly that all possessing the faculty are 

 great roamers, and consequently familiar with the country 

 over a wide radius round their homes, which leaves room for 

 the correction of a considerable margin of error in calcula- 

 tion, and thirdly that even Homing Pigeons do not always 

 return, and that only the cleverest of them are useful for long 

 flights, I do not think that the measure of intelligence de- 

 manded \s prima facie fatal to the hypothesis. 



But is the hypothesis susceptible of proof ? I think so. In 

 fact it is the certainty that it can be proved experimentally 



