278 



W. C. ALLEE 



TABLE 7 



Showing the average reactions of the individ\ial isopods under identical conditions. 

 The data were compiled from the successive reactions of isopods before they were 

 subjected to changes in the environment. Thus isopod no. I was tested 39 times 

 under such conditions making a total of 390 individual trials. Of these 88 per 

 cent were positive, 3 per cent negative and 9 per cent indefinite. The efficiency 

 was recorded 36 times and averaged 2.83. The average vigor of 19 concussion trials 

 {380 individual tests) was 0.86. The final averages were obtained by multiplying 

 the significant figures by the number of trials of which they are averages and divid- 

 ing by the total number of trials 



THE QUESTION OF A DAILY RHYTHM 



One other problem in the variation in response remains to be 

 mentioned. That is the question of a daily rhythm in the rheo- 

 tactic reaction such as Bohn found to exist in Convoluta (Bohn 

 '03, '03 a). A large number of tests have been made through- 

 out the entire period of experimentation covering the time from 



