CERTAIN RELATIONS BETWEEN RHEOTAXIS AND 



RESISTANCE TO POTASSIUM CYANIDE IN 



ISOPODAi 



W. C. ALLEE 



Thompson Biological Laboratory, Williams College 



Earlier experiments (Allee '12-13) showed that certain condi- 

 tions known to affect the rate of metabolism of animals regularly 

 affected the rheotactic reaction of the isopod, Asellus communis, 

 Say. Low oxygen, chloretone, potassium cyanide, lowered 

 temperature, suddenly heightened temperature, increased carbon 

 dioxide tension, and starvation, all of which depress the rate of 

 metabolism of animals, also lower the positive rheotactic response 

 of isopods. High oxygen, caffein, and a gradual increase in 

 temperature have the opposite effect. 



A desire to obtain more exact information regarding this corre- 

 lation of metabolic rate and the rheotactic reaction of isopods led 

 to an attempt to measure the rate of metabolism by means of the 

 survival-time in potassium cyanide. This method was worked 

 out by Professor Child ('13) for planarians, and is essentially as 

 follows : 



In a relatively strong solution of potassium cyanide (0.001 mol. 

 or thereabouts) the animals having the highest rate of metabolism 

 die first, or in other words, they have the shortest survival- time. 

 Those having the lowest rate die last and hence have the highest 

 rate of metabolism. Child called this the 'direct method' of 



^ The experiments upon which this paper is based were performed in the Lab- 

 oratory of Plant Physiology at the University of Illinois and in the Marine Bio- 

 logical Laboratory, Woods Hole, Mass. I am indebted to Dr. C. F. Hottes and 

 Prof. F. R. Lillie for furnishing facilities for carrying on the experiments. I am 

 also indebted to Prof. C. M. Child and to Dr. Shiro Tashiro for many helpful 

 suggestions, and to Marjorie Hill Allee for assistance with certain experiments and 

 for aid in tabulating results. 



397 



