DISTRIBUTION OF MEMORY 223 



One of the most remarkable conclusions of Bethe 

 is the assumption that the roads of the ants have two 

 paths which differ chemically from each other, one 

 leading from and one toward the nest. Bethe tried 

 to prove this by experiments that had been undertaken 

 before by Lubbock, who obtained no definite results. 

 Bethe arranged a broad ant-street so that it led over 

 a turn-bridge. He revolved this bridge 180, when 



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the ants were passing to and from the nest, and found 

 that it was impossible for the two armies to continue 

 on their way. He again turned the bridge 180 so 

 that the tracks had the original orientation. The 

 ants continued in the direction they were pursuing 

 when disturbed. An observation made by Forel also 

 agrees with this : " An ant that is picked up from 

 the path while moving and then put down again is al- 

 most sure to take the same direction, no matter what 

 orientation is given to its body." This, however, 

 only holds good for a street which is often travelled. 

 A weak track which leads in one direction is qualified 

 to lead in the opposite direction, as is shown by the 

 fact that an ant which has found a new supply returns 

 to the nest the same way that it came. It is evidently 

 the load and lack of load which determine which path 

 the ant will take (that is, to or from the nest). The 

 load causes the ant to go to the nest reflexly ; the lack 

 of a load causes it to O from the nest. Bethe comes 



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to the conclusion that the reactions of ants, which 

 have always been considered psychic phenomena, are 

 merely reflex processes comparable to the tropisms. 



