326 Journal of Comparative Neurology and Psychology. 



appearance of a large object in the field of vision. Ranatras that 

 are swimming towards the light generally check their move- 

 ments and lie perfectly quiet for some minutes as soon as they 

 perceive one's approach, but if no movement is made near them 

 they soon resume their phototactic activities. This inhibition 

 of movement recalls that which in higher forms is often brought 

 about by fear, but of the usual manifestation of fear in the efforts 

 to escape from enemies by flight Ranatra evinces no sign. 



Control in Ranatra probably amounts to nothing more than 

 supplanting one instinctive tendency by another. The reac- 

 tions of the insect to light seem to take place inevitably unless 

 some circumstance calls into play some other equally stereo- 

 typed form of instinctive response. 



8. The Effect of Hemisecting the Brain. Cutting the 

 brain of Ranatra through the middle was accomplished by 

 means of a fine needle ground down to a sharp edge. Only a 

 small opening need be made, and there does not follow the pro- 

 fuse bleeding which results from making larger incisions. After 

 hemisection of the brain specimens are easily kept alive for sev- 

 eral days. Their behavior may be illustrated by the following 

 records of experiments : 



The brain was hemisected in three specimens^at 8:45 A. M. In one minute 

 or less they came out of their death feint; in five minutes they were picked up 

 and stroked and then laid on the table. None feigned death for more than two 

 or three seconds. At 9:25 they were still very restless and none of them paid the 

 least attention to the light that was held near them. They all performed circus 

 movements to a greater or less extent, due, doubtless, to the fact that the brain 

 was not cut exactly through the middle. At 11 A. M., one flew out of the dish . 

 They were all picked up aud stroked again, but none feigned for more than a few 

 seconds. When the light was moved about near them they would show no head 

 reflexes or other decided response, although the light seemed to stimulate them in 

 an indefinite way. During the next two or three days they continued the same 

 restless movements and could be induced to feign death only for a few seconds. 

 Definite responses to light failed to return. 



The brain in three other specimens was hemisected at 12 M. They all soon 

 came out of the death feint that was induced by handling them during the oper- 

 ation. At i:20 P. M., when they were again observed, they were very restless. 

 When picked up, stroked, and laid on the table they feigned death for one min- 

 ute, four minutes, and ten minutes respectively. The next day they could not 

 be induced to feign for more than a minute and they showed no definite response 

 to light. They were also tried on each of the three following days and their be- 



