RHEOTAXIS OF ISOPODS 207 



isopods from the respiration chamber they were placed in an 

 Erlenmeyer flask in 0.001 mol. solution of potassium cyanide 

 and their survival time was ascertained by Allee. It should 

 be noted that the experimenter on the determination of the 

 carbon dioxide output was ignorant of the behavior of the 

 animals, thus eliminating any prejudice for the determinations. 

 The results of experiments of this character are shown in 

 table 1. 



The table shows that in ten of the twelve isopods tried the 

 evidence from the survival time ran parallel with that of the 

 carbon dioxide production, that is, the isopods giving the more 

 carbon dioxide had the shorter survival time in the cyanide. 

 The table also shows that where there was a difference in the 

 rheotactic reaction of the animal tested, the more carbon dioxide 

 was given by the isopod that gave the higher percentage of 

 positive rheotactic reactions. (Cf. page 213; also Allee, '14.) 

 In the case of isopods No. 94 and 95 where the isopod that gave 

 off less carbon dioxide lived a shorter time in the cyanide the 

 experimental records show that No. 95 moved more in the 

 respiration chamber than did No. 94 and also that it was two 

 millimeters longer. Either of these factors might account for 

 the discrepancy. If the potassium cyanide resistance in this 

 case is taken as the true index of the metabolism it will be noted 

 that the animals living longer, i.e., having the lower rate of 

 metabolism gave the highest percentage of positive rheotactic 

 reactions. This apparent contradiction will be discussed later 

 (page 211). 



Since in S3% of the cases tried the carbon dioxide produc- 

 tion tallied exactly with the resistance to potassium cyanide 

 and in the other 17% of the cases the apparent exception 

 is capable of reasonable explanation, it seems safe to conclude 

 that so far as carbon dioxide production is concerned the resis- 

 tance of isopods to potassium cyanide is a safe index of the 

 metabolic activity of the animals. 



THE EFFECT OF THE CALCIUM ION UPON RHEOTAXIS 

 AND CARBON DIOXIDE PRODUCTION 



In connection with experiments on irritability Tashiro has 

 studied the effects of inorganic salts upon tissue metabolism. 

 Whatever the mechanism of the effect of such salts on tissues 



