460 PROCEEDINGS OF THE AMERICAN ACADEMY. 



observations, and a discussion of the results will be reserved until the 

 close of the section. 



Experience having taught that Stentors are very sensitive and respon- 

 sive animals, I decided to make an experiment by which to determine 

 whether the numerous Stentors produced in the manner last described 

 were really due to the influence of potassic chloride upon division. The 

 possibility of this suggested itself, and indeed the following experiment 

 was made, before the above-described detailed examination of the process 

 was undertaken. 



Expt. No. 13, Nov. 4, 1901. 



Preparations of Stentor by the drop method in a 0.0167 m. potassic 

 chloride medium and the control preparations made in hay infusion were 

 strictly parallel in origin of animals used, in time, in dilution of reagent, 

 and in room conditions. They were all handled with great caution to 

 avoid violence, especially in mixing fluids. The following results were 

 obtained : 



0.0167 m. KCl. Control. 



Time hr. 6 hr. hr. 6 hr. 



No. of Stentors 298 331 192 193 



No. of Divisions 33 6 



Mortality 5 



Mean Result ...... 1.11 1.00 



As in Experiment No. 11, the number recorded in the potassic 

 chloride preparations did not include all that might have been counted, 

 some having been omitted because of their small size. In the control 

 experiment no such dithculty arose, as the offspring were all of nearly 

 normal size. 



A comparison of the division-reaction of different Protozoa subjected 

 to the same essential conditions is of interest. I therefore give, briefly, 

 the results of some experiments made with potassic chloride and sodic 

 chloride upon Paramaecia. The conditions were parallel with those 

 employed in the experiments on Stentor. 



Expt. No. 20, Nov. 20, 1901. 



Hanging-drop preparations of Paramaecia in hay infusion were 

 treated tor one minute with a 0.167 m. sodic chloride solution. It was 



