340 THORBORG MARIE BRUNDIN 



obliquely in the direction of the light, and finally the direct 

 positive response begins. The first positive reactions are marked 

 by a wavering, hurried, excited manner. The wavering then 

 disappears, the path to the light becomes definite and the crea- 

 tures become more and more excited until they begin to leap 

 to the light, and try frantically to get to it through the side 

 o f the dish. This state of great activity lasts some time, and 

 finally through exhaustion, they become indifferent to the 

 stimulus, and some specimens show a weak negativity. 



Reaction time of large and small specimens. — The following 



table shows the number of minutes o F negative response in 



large and small specimens taken out of the dark-room in which 



they had been kept for twenty-four hours. Some of these had 



been kept in a low temperature, hence the difference in time 



reactions. 



Number of Minutes of Negative Phototaxis 



Large specimens Small specimens 



4 



3J 2 



13 5 



H 



10 5 



4+ 1 



10 3 



4 o 



4* 2 



10 



7 : 3i 



6+ 



I timed one set of a dozen large and small Orchestias on five 

 successive days. They were kept in darkness with the same 

 conditions o f moisture, and taken out every twenty-four hours 

 and exposed to a strong light. The following gives the time 

 reactions of the large and small specimens : 



In a set o f specimens kept on ice for twenty-four hours, and 

 then exposed to light, the large ones remained negative for 



