458 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Expt. No. 9, Oct. S4, 1901, 



was similar to Experiments 6 and 7, except that 0.016 m. potassic chlo- 

 ride was used in the test experiment and that the count was taken after 

 sixteen hours. Test and control contained 142 and 170 Stentors resjiec- 

 tively and gave average increases of 1.09 and 1.05 respectively. 



I now abandoned the method of temjwrary application of the reagent, 

 for reasons that will be stated in the subsequent discussion. Hence in 

 all the subsequent tables of this section the given concentration of the 

 reagent was continuously applied, except when the time is expressly stated. 

 I also desired to compare the reaction to jjotassic chloride with that to 

 sodic chloride. 



Expt. No. 11, Nov. 1, 1901. 



The method of hanging drops was used as previously described. I 

 here adopted the plan, later abandoned, of making both test and control 

 experiments in a medium consisting of diluted and more or less fermented 

 hay infusion. Both media when completed contained the same propor- 

 tion of strong hay infusion, the dilution being made with tap water. 

 They differed in the fact that one portion of test medium contained 

 potassic chloride added in the proportion of 0.01 m., while the other con- 

 tained sodic chloride added in the proportion of 0.01 m. The results of 

 three sets of simultaneous preparations were as follows : 



The Division- Reaction of Stentor to Potassic Chloride. 



I shall now describe the phenomenon of division in a potassic chloride 

 medium, which occurred abundantly in this and the following experi- 

 ments. I observed in the hanging drops of the potassic chloride medium 

 numerous Stentors of sizes ranging from that of a normal individual to 

 that of one so very much smaller than normal, that it was difficult to 

 decide whether to count each as a single individual. The count given 

 above under 0.01 m. potassic chloride does not include all the individuals 



