Tropisms Relation to Modes of Behavior 61 



and which indicate that this insect is something more 

 than a mere "reflex machine." If one eye is black- 

 ened over there is a strong tendency for the insect 

 to perform circus movements toward the normal 

 side. Frequently as the insect veers over toward 

 the normal side in going toward the light and thus 

 brings the unblackened eye more and more out of 

 the region of direct stimulation, a point is reached 

 where there is hesitation, moving this way and that, 

 accompanied by increasing uneasiness and excite- 

 ment as if the creature were exasperated over its 

 predicament. Sometimes the insect may get out 

 of this situation by going completely around in 

 a circle toward the normal side, or it may make 

 a direct turn toward the blackened side and go 

 toward the light. In several cases among Ra- 

 natras and Notonectas individuals which at first 

 performed circus movements and succeeded in 

 going to the light by a very irregular route finally 

 came, after a number of trials, to go to the light 

 in a nearly straight line. Other individuals went 

 to the light in a nearly straight line from the first. 

 In some cases covering all of one eye and all but 

 the posterior face of the other did not prevent the 

 insect from going in a nearly straight path toward 

 the light. Other specimens would do the same with 

 only a small part of the lateral face of one eye 

 uncovered. In the latter case neither the lightest 

 nor the darkest part of the visual field was kept be- 

 fore the eye. The insect behaved as if it were 



