428 'Journal of Comparative Neurology and Psychology. 



12. Do. 9:30 a.m. Same stage, substituted incline B for A and placed incline A on the opposite 

 side of the nest. The ants had rested five minutes. (At the beginning a worker went, unburdened, up 

 incline B to the nest, but did not return to the stage.) 



13. July 25, 7:30 a.m. A stage from which incline A descends from the left side to the nest. It 

 was illuminated by a 16 c.p. incandescent lamp placed near to the off-side of the incline. The ants had 

 rested fifteen minutes. 



Fig. 4. Learning-curve of Formica fusca var. subsericea Say, acting in concert; showing the efiect of 

 frequent changes of environment. 



1. July I, 8:30 a.m. A cardboard stage with an incline attached to the left side. 



2. Do. 9:00 a.m. Same as above. The ants had rested ten minutes. 



3. Do. 9:10 a.m. Same as above. The ants had rested one minute. 



4. Do. 9:33 a.m. Same as above. The ants had rested one minute. 



5. Do. 10:33 ^•™' Same as above. The ants had rested three minutes. 



6. Do. 1 1 :00 a.m. Same as above. The ants had rested one minute. 



7. Do. 3:30 p.m. The same stage used in the above, but a new incline B is substituted for incline 

 A. A is then attached to the opposite side of the stage. The majority of the pupa: were carried down 

 incline B. At first, occasionally, a worker would carry a pupa down A, but in each case that worker 

 moved much slower than those moving down B. The ants had rested four hours. 



8. Do. 4:40 p.m. A new stage and a new incline. The ants had rested one hour. 



9. July 6, 1 1 :24 a.m. A new stage with a new incline on the right side (the other inclines had been 

 on the left side). The ants had rested four days, fourteen hours and thirty-four minutes. 



10. Do. 12:28 p.m. Same apparatus as above. The ants had rested one minute. 



11. July 6, 2:25 p.m. Same apparatus as above. The ants had rested five minutes. 



12. Do. 3:00 p.m. Same stage, but incline yf was placed on the opposite side of the stage and a 

 new incline B placed where A had been. The pupae were all carried down B to the nest, occasionally 

 a worker would carry a pupa partly down A and then return to the stage. The ants had rested thirteen 

 minutes. 



13- July 10, 7:55 a.m. A new stage with a new incline attached to the right side of the stage. The 

 ants had rested four hours and twenty-five minutes. 



Fig. 5. Learning-curve of Prenolepis imparis Say acting in concert, showing unexpected variations 

 in the mode of response. • 



1. July 9, 7:31 a.m. A cardboard stage with an incline A attached to the left side. 



2. Do. 10:46 a.m. Same apparatus as above. The ants had rested one minute. 



3. Do. 8:05 p.m. Same apparatus as above. The workers had rested over nine hours. 



4. July 10, 6:30 a.m. Same apparatus as above. The ants had rested eight hours and ten 

 minutes. 



5. Do. 7:55 a.m. Same apparatus as above. The ants had rested ten minutes. 



6. Do. 9:35 a.m. Same stage, a new incline B is substituted for A and A is placed on the 

 opposite side of the stage. The ants had rested ten minutes. 



Fig. 6. Learning-curve of Prenolepis imparis Say acting in concert, showing the effect of the 

 direction of the rays of light and the result of placing a dark chamber over the top of the incline. 



1. July 9, 7:06 a.m. A cardboard stage with incline -i on left side. 



2. Do. 8:16 a.m. Same apparatus as above. The ants had rested one minute. 



3. Do. 9:55 a.m. Same apparatus as before. The ants had rested one minute. 



4. Do. 10:45 a.m. Same apparatus only the stage was revolved through an angle of 180°, but 

 the incline was left in the same position. Thus there was an unscented path from the pupae to the incline. 

 The ants had rested six minutes. 



5. July 10, 6:30 a.m. Same apparatus as before. The ants had rested twenty hours. 



6. Do. 9:08 a.m. Same as above only the stage was revolved through 180°, J was left in the 

 old place. Thus there was an unscented path from the pupae to the incline. 



7. July II, 6:28 a.m. Same apparatus as above. The ants had rested twenty-one hours. 



8. Do. 7:21 a.m. Same apparatus as above. The ants had rested fifty minutes. 



9. July 12, 7:46 a.m. A new cardboard stage with a new incline leading down to the island. A 19 

 c.p. incandescent lamp was placed near the incline. The ants had rested one day and twenty-five minutes. 



10. Do. 8:53 a.m. Same apparatus as before. The ants had rested three minutes. 



11. July 13,7:11 a.m. Stage with incline B on the right. 16 c.p. lamp on the same side as B. 

 The ants had rested forty-nine minutes. 



