RHEOTAXIS IN ISOPODA 



269 



TABLE 4 



Showing the efficiency and response to shock accompanying high and low positive- 

 ness. The respo?ises are averages of all the reactions given by the individual under 

 the conditions of the table. The general averages are obtained by multiplying the 

 number of instances by the average response and dividing by the total number of 

 instances. 



Table 5 shows a similar state of affairs when the responses 

 accompanying high and low efficiency are compared. An effi- 

 ciency of 2.8 or more is regarded as high and one of 1.8 or less 

 as low. As before isopods nos. VII, XII, XV and XIX, which 

 showed a large number of negative responses, indicate that high 

 efficiency and a high degree of positiveness do not necessarily 

 go together. On the other hand, the individual items and aver- 

 ages indicate that in the main they do. In stream isopods, how- 



