338 W. C. ALLEE 



IV. DISCUSSION 



In presenting these results the writer realizes fully the attend- 

 ing imperfections and the need of more work along some lines. 

 But in order to do further work with this material, in this field, 

 in an intelligent manner, these general relationships had to be 

 first blocked out. It is the author's intention to follow this paper 

 with a study of the effect of the same conditions upon another 

 characteristic isopod reaction, and to further analyze the interest- 

 ing relations shown during the breeding season. 



The principles upon which this paper is based have been suc- 

 cessfully worked out (under the author's direction) with amphi- 

 pods by Mr. W. J. Saunders in an unpublished master's thesis 

 and with amphipods and planarians by graduate students doing 

 course work in experimental animal behavior. The work of these 

 students has shown that the rheotactic reactions of both amphi- 

 pods and planarians are comparable with those of pond and stream 

 isopods and may be controlled by the same external factors. 



In the summary of the experimental results just given, the basis 

 for classification was made the positiveness of the isopods in their 

 rheotactic responses, but if the heading were rather the effect of 

 these conditions upon the metabolic state of the organism, the 

 summary would not need to be changed. For all the conditions 

 that have been found to cause a decrease in the positive reaction 

 are known to depress the rate of animal metabolism (Child, I.e., 

 p. 173). Low oxygen (Haldane and Smith, '97, p". 242) potassium 

 cyanide (Geppert, '99, p. 208) and high carbon dioxide (Cushny' 

 '10, p. 587) do this by directly decreasing the oxidations. Chlo e- 

 tone belongs to the general group of anaesthetics that are known to 

 have a depressing effect upon certain of the fundamental meta- 

 bolic reactions (Child, I.e., p. 173; Cushny, I.e., p. 195). The 

 decrease in activity due to low temperature is a well known phe- 

 nomenon in both animals and plants, as is also the depressing 

 effect of an increase of temperature above the optimum for life 

 relations, while starvation decreases metabolism by removing 

 the material to be oxidized and so gives the same, results from the 

 other side of the equation. On the other hand, the rate of metab- 



