TOXICITY OF ACIDS TO CILIATE INFUSORIA 



455 



of the coefficients for a change of 10° obtamed with Paramoe- 

 cium He between 2 and 3, whether the temperature range is 10° 

 to 20° or 20° to 30°, so chemical reactions would seem to be im- 

 portant. Euplotes also has coefficients between 2 and 3 for the 

 range 20° to 30° which are to be explained in the same way. 

 At lower temperatures, however, the condition for Euplotes is 

 different. Over the range 15° to 25° and 10° to 20° the coefficients 

 are generally little more than unity. A few coefficients of less 

 than 2 were observed over this range for Paramoecium, but were 

 decidedly the exception, instead of being the rule as with 

 Euplotes. These low coefficients suggest complicating physical 



Minutes. 10 20 30 40 



Graph 3, D Effect of temperature upon the toxicity of hydrochloric and of 

 butyric acids to Euplotes. A. HCl, 0.0005 N; B. HCl, 0.0002 N; C. Butyric, 

 0.001 N; D. Butyric, 0.0005 N. 



factors perhaps masking a chemical reaction. Especially remark- 

 able are the results obtained with Euplotes in acetic and 

 butyric acids. 



