258 W. C. ALLEE 



conditions used experimentally were: low oxygen, chloretone, 

 potassium cyanide, low temperature, sudden extreme increase of 

 temperature, increased carbon dioxide, and starvation. On the 

 other hand, atmospheric or complete saturation of oxygen, caffein, 

 and an increase of temperature if not too extreme, caused the 

 pond isopods to give a higher percentage of positive responses. 

 These last conditions are known to increase the metabolic rate 

 of the organism. 



All this first work was done on groups of isopods selected at 

 random from the general stock. Usually from five to eight were 

 tested at the same time and the averaged results from ten suc- 

 cessive trials were taken as representing the condition of the 

 group under experimentation. The present series of experiments 

 deals with the individual isopod rather than the group. In 

 order to give time for more intensive study these experiments 

 deal with individuals of the stream mores only. They were 

 conducted to throw light on the following questions: 



1. What is. the relation between the efficiency of movement 

 in the current and the sign of response in rheotactic reactions? 



2. Is there any relation between the reaction to a uniform 

 shock stimulus and the sign of the rheotactic response, or the 

 efficiency of that response? 



3. How great a variation is there in the rheotactic reaction 

 of individual isopods kept in uniform conditions? 



4. What is the effect of the depressing agents, potassium 

 cyanide and low oxygen, upon the rheotactic and shock reactions 

 of the individual isopods? 



5. What is the effect of the molting period upon rheotaxis? 

 These experiments are being prosecuted from the ecological 



point of view. The term 'ecology,' as I understand it, means 

 that portion of general physiology which has for its problem 

 the relation between the organism and its complete environment 

 (cf. Semper '81, pp. 25-35; Shelford '12 c, pp. 333-34) I fully 

 agree with Shelford ('12 c, p. 365) that the ecologist must spe- 

 cialize upon some aspect of the subject, because it is unusually 

 large and its concepts unusually complex. Since the data as 

 collected in field observations are so complex and since there 



