386 yoiinial of Comparative Neurology ami Psychology. 



a specimen of Formica fusca var. subsericea Say. On this occa- 

 sion two marked workers, A and B, were being experimented upon 

 at the same time. The one I have called A readily learned the 

 way down and up the incline; but to B this was an insoluble prob- 

 lem. It continued for a long time to move at random over the 

 stage, reaching down over first one edge and then over another, 

 as though it were reaching for a support that was not to be found; 

 but nothing prompted it to pass down the incline. In experiments 

 where the time required to learn the trick was not the point to be 

 investigated, I had sometimes helped ants to learn the way by 

 forcing them with forceps or spatula, to move in the right direction. 

 I thought I would thus help B to learn. So with my forceps I 

 pushed it along. Several times I succeeded in getting it to the 

 incline, but nothing that I did would induce it to go down. I had 

 failed, but this was not the first time that I had failed in similar 

 attempts with other ants. 



Prompted by another thought, I shoved the section-lifter under 

 the ant and transferred it to the island. The ant then stepped off 

 and carried the pupa into the nest. As soon as B returned to the 

 island, I shoved the section-lifter under it and transferred it to the 

 stage. B stepped off and picked up another pupa. With the 

 section-lifter I again transferred it to the island. After this had 

 been repeated several times, the moment I presented the section- 

 lifter, whether on the island or on the stage, the ant immediately 

 mounted it and rested quietly thereon until it had been removed to 

 the stage or to the island; then it stepped off and picked up a pupa 

 or else went into the nest. I usually held the section-lifter from 

 two to four millimeters above the surface of the island or stage. 

 In this manner the industrious creature passed to and from the 

 stage about fifty times in something less than two hours. 



Whenever I presented the section-lifter to other ants of the 

 same colony, they would attack it, or avoid it, or else mount it and 

 roam over blade and handle and sometimes even my hand. When 

 the same section-lifter was presented to A (the one that all this 

 time had been conveying pupze down the incline) it would avoid 

 it and pass on. 



Thus I had two individuals of the same colony, at the same time 

 and under identical external conditions, responding to the same 

 stimulus in quite different ways. To the one the incline had no 

 psychic value, to the other it was a stimulus to pass to and from 



