Turner, Homing of Ants. 417 



shorter, often much shorter, than was needed by the ant the first 

 time such a problem was presented. Aside from the differences 

 of time required for different individuals to reach the nest, there 

 were marked individual differences in their conduct. I noted 

 five different modes of response: (i) An ant would take a pupa 

 to the nest and remain therein instead of returning to the stage. 

 (2) An ant would pass unburdened to the nest and remain there- 

 in instead of returning to the stage. (3) An ant would carry a 

 pupa to the nest or to some point on the island and then return to 

 the stage and make repeated trips. (4) An ant would pass, 

 unburdened, to the nest, and then immediately return to the stage 

 for a pupa and thereafter make regular trips. (5) Occasionally, 

 a worker would pass, unburdened, to a point near the nest, then 

 return to the stage for a pupa and thereafter make regular trips. 



Such marked individual differences in conduct were noted be- 

 tween members of the same colony, under the same external 

 environmental conditions. 'AH of these individuals, at the time 

 of their imprisonment, were thoroughly acquainted with the way 

 between the nest and the stage. The difference cannot be attrib- 

 uted to fatigue, for they had been resting from one to several 

 hours. It seems to me that these facts harmonize rather with the 

 memory hypothesis than with either the "assimilation of idea to 

 impulse" or to the "determination of stimulus" hypothesis. 



If either of the two latter hypotheses is true, the following is 

 probably a fair statement of the factors that guided my ants to and 

 from the stage to the nest. The sensing of the pupa on the stage 

 causes the ant to pick it up and move in a certain direction. The 

 direction of the rays of light, etc., cause it to move to the point of 

 union of stage and incline. Contact with that point, etc., cause it 

 to turn and pass down the inchne, receiving the light on a differ- 

 ent side than before. At the base of the incline, contact with the 

 zinc, etc., cause it to pass to the side of the nest, where other stimuli 

 cause it to go into the nest, where yet other stimuli cause it to lay 

 down its pupa. Now all of these several stimuli act on it in a 

 reverse way and cause it to return to the stage. After the "assim- 

 ilation of impulse and idea" or the "determination of stimulus" 

 has been made, the animal moves along just as automatically as 

 an animal in a tropic response. Each stimulus is responded to as 

 an end in itself and not as a means to an end. Now, if I interpret 

 my experiments aright, none of the ants examined acted this way. 



