342 THORBORG MARIE BRUNDIN 



temperature was raised in case of specimens in the water and 

 also in the air. Even aquatic species were found to become 

 positive when the water was heated to one hundred degrees F. 



I noticed often in the course of experiments that negative 

 specimens of traskiana were made positive in a very short time 

 if they were disturbed and kept moving about. When a speci- 

 men began to run from the light, I would stop it with a stick 

 or bit of cardboard and turn it toward the light. After this 

 was repeated a number of times, sometimes only six or seven 

 times, the most negative specimens would become positive in 

 a fraction of the time it would take under ordinary conditions. 



There are but two causes, so far as I can see, that might be 

 responsible for this hastening of the positive response — first — 

 the greater amount of light stimulus received by the eyes under 

 the constant turning toward it, and second, the greater amount 

 of activity brought about by the struggle to get away from 

 the l'ght. 



Upon the hypothesis that bodily activity, no matter how 

 brought about, would cause a rapid positive phototaxis, I 

 shook up some 0. traskiana in a dish in complete darkness for 

 about ten minutes. These specimens were part of a set that 

 had been standing in the dark for twenty-four hours in moist 

 filter paper. I removed the filter paper, allowed about one-half 

 of the specimens to remain quiet in the dark, and put the other 

 one-4ialf in a separate dish which had been moistened, in order 

 that conditions might be the same for the two sets. These I 

 shook up for the length of time I have mentioned, and when 

 exposed to the electric light they became positive in two and 

 one-half minutes, while those w T hich had been kept quiet became 

 positive in thirteen minutes. I tried the experiment a few days 

 later, shaking the specimens only five minutes. The reaction 

 time was three minutes for those disturbed, and eight minutes 

 for those which had been kept quiet. 



Holmes has shown in his work on Ranatra that after a nega- 

 tive specimen had been picked up and placed at right angles 

 to the light nine times, it became positive. He found, however, 

 that dipping positive specimens in water would reverse the 

 response. 0. agilis when placed in water, would remain per- 

 manently negative, while Talorchestia longicornis was found by 

 Holmes to show but a very weak and temporary negative re- 



