Holmes, The Reactions of Ranatra to Light. 335 



positive phototaxis, when it turned twice towards it; the specimen was put back 

 into the water. At one o'clock on the day following, it was taken out again. 

 It still showed a decided negative reaction and turned to the left and went away 

 from the light twenty-five times in succession. In nearly all cases after it had 

 turned its back upon the light it went away from it in nearly a straight line. 



After a rest of an hour and a half the asphalt varnish was removed from its 

 eye. When placed on the table, three feet from the light, the specimen went 

 towards the light and passed by it, but it turned around before proceeding very 

 far and went up to it. After this it went to the light eleven times in nearly a 

 straight line. The left eye was then blackened over. In the first two trials the 

 insect veered slightly to the left, but reached the lamp by a turn to the right. 

 In the third trial it turned sharply to the right and went off from the table. In 

 the fourth trial it went straight to the lamp. After this another fit of negative 

 phototaxis apparently seized it, for it turned from the light and walked away 

 from it in numerous trials. It then became fatigued and the experiment was 

 discontinued. It is worthy of note that while the insect, after one eye was first 

 painted over, came to take a direct course to the light only after several trials, it 

 went to the light, when the opposite eye was painted over in nearly a straight 

 line at the first attempt. Unfortunately the fit of negative phototaxis which 

 supervened prevented observation on this point from being carried out as fully as 

 would be desirable. Owing probably to fatigue or frequent handling, the speci- 

 men became more prone to react negatively the longer it was worked with, until 

 it no longer served the purpose of the experiment. 



Other experiments showed a similar straightening of the 

 course after a number of trials. As experiments on this subject 

 were undertaken late in the season, most of the inviduals worked 

 with went nearly straight to the light at the first trial. In one 

 case a specimen went nearly straight to the light six times in 

 succession ; it was then taken up and its right eye given 

 another coat of varnish to make sure that it was entirely cov- 

 ered. When put down again it seemed confused and performed 

 a number of circus movements to the left. After several 

 attempts, however, it came to travel to the light in nearly a 

 straight line. 



Similar experiments were tried on Notonecta with much 

 the same results. These insects when placed on a table near a 

 lamp travel towards the light with much eagerness. If one eye 

 is blackened over they perform circus movements towards the 

 normal side. After quite a number of trials, however, the 

 Notonectas come to take a nearly straight course to the light. 

 When they become deflected from their course they orient them- 

 selves by a direct turn in the appropriate direction. If the 



