346 Journal of Comparative Neurology and Psychology. 



cooperate in the maintenance of a direct course towards the 

 light. 



But even if we invoke the aid of both the factors mentioned, 

 we are not able completely to bring the phototaxis of Ranatra 

 under the category of direct, mechanical reflexes. Consider the 

 behavior of the Ranatra with its right eye blackened over, 

 placed at right angles to the rays with the normal eye looking 

 away from the light. The effect of light upon the muscular 

 tonus of the creature would tend to make it turn towards the 

 left side. But either at first, or after a few trials, the insect 

 turns directly to the right and goes to the light. This is done 

 with greater readiness after several trials are made ; soon the in- 

 sect turns immediately after being set free. In these experi- 

 ments the specimens were turned about, first one way and then 

 the other, before being set down on the table, but this made no 

 difference in the directness with which they turned towards the 

 light. In many cases the insects would struggle to turn towards 

 the blind side to get to the light before they were liberated from 

 my hand. So far as could be observed, there was no prelimi- 

 nary feeling about, no employment of the method of trial and 

 error; the insect seemed to retain awareness of the position of 

 the light, since it immediately made for it by the shortest route 

 as soon as it was liberated. The non-mechanical character of 

 the response is further evinced by the fact that habits of turn- 

 ing towards a certain side may be persisted in in situations in 

 which turning would otherwise take place in the opposite direc- 

 tion. The fact that Ranatras and Notonectas which have one 

 eye blackened over come, after several trials, to dispense with 

 circus movements towards the normal side and correct devia- 

 tions from their course by a direct turn in the right direction 

 affords further evidence for the same conclusion. We have seen 

 that Ranatras which at first will turn only a slight way towards 

 the blinded side when the light is carried over in that direction 

 will make sharper turns after they have become accustomed to 

 following the light around towards that side. These features of 

 the phototaxis of Ranatra indicate that seeking the light has an 

 attractiveness or interest much like that which catching prey has 



