204 W. C. ALLEE AND SHIRO TASHIRO 



THE PROBLEM 



With this more refined method of obtaining an insight into 

 the relation between physiological states and animal behavior 

 the following three lines of inquiry were prosecuted during the 

 time at our disposal at Woods Hole during the summer of 1913: 



1. What is the relation between the rate of carbon dioxide 

 production of isopods and their resistance to relatively strong 

 solutions of potassium cyanide? 



2. What is the effect of the calcium ion upon carbon dioxide 

 production and rheotaxis in isopods? 



3. Is there a relationship between the variation in carbon 

 dioxide production and the rheotactic reaction of isopods? 



THE STOCK 



Isopods from a series of collections from small fresh water ponds 

 near Woods Hole, Massachusetts, were used in these experi- 

 ments. They were all Asellus communis, Say, and were about 

 half grown. The isopods came from silt and debris bottomed 

 ponds and were kept under comparable conditions in the 



laboratory. 



METHODS 



The isopods were tested for their rheotactic reaction in a 

 circular current the bottom of which was covered with wax. 

 The responses of an individual isopod for ten successive minute 

 reaction periods were taken as a fair indication of the rheo- 

 tactic tendencies of the animal. The isopods were judged to 

 give a positive reaction when they went against the current for 

 over half of the minute's reaction period. They were considered 

 to give a negative reaction when they moved with the current 

 for over half of their minute's trial and indefinite when their 

 movements gave no indication of being regulated by the direc- 

 tion of the current. The approximate distance covered by each 

 reaction was recorded and will be found in a standardized form 

 in the tables under the head of efficiency in the current. In 

 general the movements of highly positive isopods are more vig- 

 orous than those of negative isopods, which in turn are more 

 vigorous than those giving an indefinite reaction. (For further 

 details see Allee, '13.) 



When the carbon dioxide output was to be tested the isopod 

 was dipped into water free from carbon dioxide, dried momen- 



