188 W. C. ALLEE 



the metabolic rate of Asellus. The results of this inquiry are 

 shown in figure 9. In this figure the broken line gives the sur- 

 vival time of 7 small isopods, averaging 4.3 mm. long, in N/400 

 concentration. This is to be compared with the unbroken line 

 which gives the resistance of 5 isopods that averaged 7.1 mm. 

 long. The temperature in both cases was 24°C. The vertical 

 lines give averages and the arrows show the extent of the prob- 

 able error which here is less than a fourth of the difference. 



The dotted line gives the resistance of 10 isopods 5.6 mm. 

 long in N/500 solution whose temperature had been raised 6 

 to 8°. This is to be compared with the dot-dash line which 

 gives the survival time of the same number of isopods 5.8 mm. 

 long in the same solution strength whose temperature had been 

 lowered 16°. 



The dash-three-dot-dash line represents the survival time 

 of 10 isopods which were stimulated by shaking. The average 

 length of these animals was 5.8 mm.; the temperature 24°; 

 the solution strength N/500. Shaking greatly hastens the loss 

 of equiUbrium but after the isopods quit moving, the effect 

 is almost nil. This curve is to be compared with the cross 

 barred line which shows the resistance of 20 isopods under 

 conditions identical with the last but which were not stimulated. 

 The probable error of the averages in this connection is about 

 the same as the difference and taken alone would be meaningless 

 but it supports the other curves at least to the extent that the 

 difference is in the same direction. 



We have here good evidence that young isopods and those 

 at a higher temperature have a shorter survival time in cyanide 

 than older animals or those at a lower temperature, and in- 

 dications that stimulation by shaking also increases the sus- 

 ceptibilit3^ If the cyanide is a measure of the metabolic rate 

 of Asellus these results are logical. 



Effect of potassium chloride on resistance to sodium cyanide 



Since potassium chloride was the most efficient reagent found 

 for increasing the positiveness of the rheotactic response the 

 effect of this salt on susceptibility to sodium cyanide would 



