FURTHER STUDIES ON PHYSIOLOGICAL STATES AND 

 RHEOTAXIS IN ISOPODA 



W. C. ALLEE 



The University of Illinois 



NINE FIGURES 



CONTENTS 



Introduction 257 



1. Stock 259 



Response to concussion compared with the sign and efficiency of the rheo- 



tactic reaction 261 



1. Methods 261 



2. Interrelations 267 



Daily variations in the rheotactic reaction 273 



1. Question of a daily rhythm 278 



Effect of low oxygen and potassium cyanide on the reactions of individual 



isopods 279 



Rheotaxis during the molting period 283 



Summary of results 289 



Discussion 290 



Bibliography 294 



INTRODUCTION 



This is the second of a proposed series of experimental studies 

 upon the relation between physiological states and rheotaxis in 

 the isopod Asellus communis Say. In an earlier paper (Allee 

 '12) I showed that the species A. communis Is composed of 

 pond and stream mores (Shelf ord '11 a). These mores are easily 

 distinguished, since when tested in a circular current the nor- 

 mal stream isopods give a high percentage, while those from 

 ponds give a low percentage of positive rheotactic responses. 

 Experiments have shown that conditions that are known to 

 depress the rate of metabolism decrease the percentage of 

 positive responses given by stream isopods. The depressing 



257 



THE JOURNAL OF EXPEHIMENTAL ZOOLOGY, VOL. 15, NO. 3 

 OCTOBER, 1913 



