MIGRATION. 291 



Now it is evident that this fact alone — i.e., of animals not 

 requiring to return by the same route — is sufficient to dis- 

 pose of the hypothesis advanced by Mr. Wallace* to the effect 

 that the return journey is due to a memory of the odours 

 perceived during the out-going journey, these odours thus 

 serving as land- marks. Therefore it seems to me there are 

 only two hypotheses open to us whereby to meet the facts. 

 First, it has been thought possible that animals may be ^ 

 endowed with a special sense enabling them to perceive the 

 magnetic currents of the earth, and so to guide themselves as 

 by a compass. There is no inherent impossibility attaching 

 to this hypothesis, but as it is wholly destitute of evidence, 

 we may disregard it. The only other hypothesis is that Jfj- 

 animals are able to keep an unconscious register of the turns 

 and curves taken in the outgoing journey, and so to retain a 

 general impression of their bearings. This hypothesis is 

 substantiated by the fact that, as Mr. Darwin observes, 

 savage man is certainly endowed with some such faculty ; 

 and a friend of my own (Mr. Henry Forde quoted below), 

 who has spent many years in the forests and prairies of 

 America, informs me that even civilized man when long 

 accustomed to such primitive habits of life, acquires this 

 faculty in a degree of perfection quite comparable with that of 

 savages. He also informs me that, occasionally, without any 

 assignable reason, the sense of direction becomes confused, 

 leading to a distressed sensation of bewilderment. He has 

 seen a hunter thus reduced to a lamentable condition of 

 nervousness, and when at last he abandoned himself to the 

 leadership of his companions (who relied entirely on their 

 own sense of direction), he felt persuaded tliat they were 

 going the wrong way. But on approaching his dwelling- 

 place he recognized one of the trees, and declared that a 

 particular notch upon it had passed round to the other side 

 of the trunk. Eventually he said that the whole world 



time that I slackened tlie reins, he turned sharply round and began to trot to 

 the eastward by a little north, which was nearly in the direction of his home 

 in Kent. I had ridden this horse daily for several years, and he had never 

 before behaved in this manner. My impression was that he somehow knew 

 the direction whence he had been brought. I should state that the last stage 

 from Yarmouth to Freshwater is almost due south, and along this road he 

 had been ridden by my groom ; but he never once showed any wish to return 

 in this direction " {Nature, vol. vii, p. 360). See also Nature, viii, p. 322. 

 * Nature, loc. cit. 



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