294 W. C. ALLEE 



munis in a water current depend primarily upon the rate of 

 metabolism. 



It is possible to measure the rate of metabolism by the sur- 

 vival time in a standard strength of potassium cyanide (Child 

 '13, p. 155). Since the purpose of these experiments was to 

 study the extent of variations in individual isopods this proce- 

 dure was obviously impossible. Now that something has been 

 learned concerning the amount of individual variation, the cyan- 

 ide method can be used to advantage. 



I am indebted to Dr. V. E. Shelford and Dr. C. M. Child for 

 criticism and suggestions during the progress of this work; to 

 Dr. Shelford also for reading the manuscript; to M. H. Allee 

 for assistance with certain of the experiments; to B. W. Bene- 

 dict for making the concussion apparatus without charge; and 

 to Dr. C. F. Hottes for furnishing laboratory facilities for the 

 prosecution of the work. 



April, 1913. 



