218 ROBERT H. HUTCHISON 



The above results agree with those of Loeb and Wasteneys, 

 in one respect at least, in that they show that the protective 

 action of salt solutions is not an osmotic effect. But when we 

 find distilled water just as effective as three of the salt solu- 

 tions used and almost as effective as M/50 NaCl, and the combi- 

 nation of NaCl and CaCl2, it is apparent that in the case of 

 Paramecium at least, the results are not due to the ''specific 

 action of the salts." 



Some results of tests with another race of Paramecia in an acid 

 medium detract still more from the specific salt action as a 

 satisfactory explanation. An account of some of these results 

 follow. 



Parainecium caudatum in an acid medium. The culture me- 

 dium was prepared by boiling 20 grams of hay in 500 cc. of tap- 

 water for one-half hour. The following day it was seeded with 

 a single individual isolated from another pure culture which 

 had been growing in the laboratory for some time. This culture 

 medium retained its hght straw color throughout. It was never 

 as densely populated as the alkaline mediiun and died out sooner, 

 i.e., in about three months. Most of the following experiments 

 were performed when the culture was about two months old. 

 It was still light colored and slightly acid to litmus. Tables 

 7 and 8 summarize the results of tests with M/4000 CaCl2, with 

 M/lOO NaCl, and with distilled water. 



It is to be noted that the control experiments show that the 

 normal heat resistance of this race was somewhat higher than that 

 of the race from the alkaline medium, the average of all the con- 

 trols of the acid medium being about one degree higher than the 

 average of all the controls of the alkaline medium. This is 

 just the opposite effect from that produced by acids and alkalis 

 on the coagulation temperature of proteids. Further, it will be 

 noted that the same salts (NaCl and CaCl2) which gave the 

 most pronounced protective action with the Paramecia from the 

 alkaline medium, actually decreased the resistance of those 

 from the acid medium. Considering the action of the salts 

 alone it might be supposed that their effects were conditioned 

 by the reaction of the medium in which the animals had pre- 



