HEAT RESISTANCE OF PARAMECIUM 



217 



Perhaps the most curious results of all were obtained when this 

 race was subjected to the influence of M/600 Na2C03, and to 

 distilled water. Table 6 shows these results and those of the 

 corresponding controls, all of which were carried out at the same 

 time. 



The results in table 6 show that distilled water was just as 

 eff"ective in its protective action for this race as was M/600 

 NasCOs, or M/50 KNO3, or as M/3000 CaCls. The mean death 

 temperature in distilled water was 1.78°C. higher than the 

 corresponding controls. 



In cane sugar solutions there was no protective action mani- 

 fest. In one experiment two drops of the medium densely popu- 

 lated with Paramecia were transferred to 5 cc. of M/8 cane 

 sugar. When subjected to heat some deaths occurred at 38° 

 and above. This solution was much less effective than distilled 

 water; indeed, it appeared to have a weakening effect. 



TABLE 6 



The effect of M/600 Na^COz, and of distilled water, on the heat resistance of P. 

 caudatum from an alkaline medium 



MEANS OF THE ABOVE FATAL TEMPERATURE 

 ZONES 



in M/600 NaoCOa 41 .62° 



in distilled water 41 .82° 



in controls 40.04° 



