168 



W. C. ALLEE 



The chlorides of potassium and rubidium were found to be 

 most efficient in increasing the positiveness of the rheotactic 

 reaction. These salts are chemically closely related and must 

 represent the optimum of the series of conditions that are found 

 in the alkali metal series. The effect of these two cations (with 

 the chlorine anion) is so striking that it is worth while exhibiting 

 the result of their action. The effect of rubidium chloride may 

 be seen in table 2 and that of potassium chloride in table 5, p. 190. 



TABLE 2 



1 The figures in these columns give in a standardized from the amount of 

 movement of the isopods during their rheotactic test. For detailed account 

 see '13, p. 261. 



The cases listed in the rubidium table are selected and are 

 the most diagrammatic obtained with that reagent while those 

 shown for potassium include all the tests for a given experiment 

 which explains the apparently greater efficiency of rubidium. 



The stimulating effect of potassium and rubidium chlorides 

 was noticeable in the general behavior and particularly in the 

 increased rapidity of movement of the isopods. One of many 

 similar laboratory notes for rubidium (N/10 solution) is: 'Tsopod 

 became nervously active immediately although it had been slug- 

 gish before." Another for potassium (N/10) is "All nervous, 

 excited, although losing power of coordination." Continued 



