410 "Journal of Comparative Neurology and Psychology. 



the direction of the nest, it would receive the hght rays on the 

 same side of the body as it would in passing down the incline. 

 The only new factor that entered the life of the ant that moved 

 down the incline rather than horizontally along the stage towards 

 the nest was the experience of moving downward. Vertical 

 changes in direction must aftect ants differently from horizontal 

 changes in direction, otherwise there is no reason why the ant 

 should pass regularly down the incline rather than horizontally 

 along the stage towards the nest. 



Again, after an ant had thoroughly learned the way down and 

 up the incline, it would often not take the trouble to go all the way 

 to the union of stage and incline, but, reaching the edge of the 

 stage at a greater or less distance from its union with the incline, 

 the ant would reach downward over the edge; if it could not touch 

 the incline it would move nearer the junction of stage and incline 

 and again reach downwards. If necessary, it would move nearer 

 still. As soon as the ant could touch the incline, it would step 

 off of the stage and move obhquely downward to the nest. 



To test this matter further, the following experiment was de- 

 vised. Underneath the incline of one of my stages was placed an 

 adjustable support made by sticking a pin vertically into the cork 

 of a small bottle. Since the lower end of the incline was free while 

 the upper was attached to the stage, by moving this adjustable 

 support more or less towards the base of the incline, a vertical gap 

 of any desired size could be formed and maintained between the 

 base of the mclme and the island. After the ants had thoroughly 

 learned the way to and from the nest, a small vertical gap, which 

 was gradually increased until the ants on the island could no 

 longer touch the base of the incline with their antennae, was made 

 between the foot of the mcline and the island. Now so long as 

 the ants could touch the incline with their antennae, they would 

 stretch upward until their forefeet touched the incline, then mount 

 the incline and go to the stage. Ants coming down the stage acted 

 the same way, only they stretched downward rather than upward. 

 When, however, the base of the incline could no longer be touched 

 by their antennae, the ants would come to the place where the foot 

 of the incline had been, elevate the front part of their bodies as 

 much as possible and reach upwards with their antennae. Ele- 

 vating the base of the incline still more, I placed along the side of 

 the path and parallel to it a stack of clean microscopic slides, one 



