330 Journal of Comparative Neurology and Psychology. 



started out. In one experiment a Ranatra with the the right 

 eye blackened over was placed at a distance of four feet from a 

 l6 candle power lamp. In all of the twelve trials that were 

 made it started on a nearly straight course towards the light as 

 it was originally pointed. In all cases it veered to the left and 

 naturally diverged from the straight path more and more the 

 farther it proceded. When a little more than half the distance 

 to the light had been covered it corrected its course and pro- 

 ceeded towards the light again in a more direct path. This 

 took place by two methods and usually occurred when the nor- 

 mal eye was looking away from the light. In this situation the 

 insect would frequently stand for some time as if undecided 

 which way to turn. In four instances it turned towards the 

 right and proceeded again in the direction of the light. In 

 eight cases it continued turning to the left until it had gone 

 completely around in a circle after which it went up to the light. 



Specimens with one eye blackened over present, however, 

 marked individual differences of behavior. In some cases the 

 insect walks toward the light in a nearly straight line. Rana- 

 tras which were taken late in the fall or early in the winter in 

 most cases went nearly straight to the light while those experi- 

 mented with in the early fall usually performed circus move- 

 ments. This difference may have been due to accidental indi- 

 vidual differences in the specimens, or it may have been the 

 result of differences in age, the older Ranatras being better able 

 to correct their course than the younger ones. The tendency 

 to turn away from the blind side is manifested to a greater or 

 less extent in all cases, but in many specimens it does not go so 

 far as to produce decided circus movements. 



If the whole of one eye and all but the posterior surface of 

 the other is blackened over the insect in many cases is still 

 capable of following a nearly straight path towards the light, 

 A tendency to perform circus movements is more or less mani- 

 fest and many specimens will go around in a circle repeatedly, 

 especially when the light is near them. When all but the pos- 

 terior surface of one eye is blackened over the insect is able to 

 guide itself to the light nearly as well as when one eye is entire- 



