PETERS. — METABOLISM AND DIVISION IN PROTOZOA. 467 



that I abandoned my original intention of making the solutions used 

 strictly isotonic, as measured by the dissociation coefficient, i. 



Closely fitting solid watch-glasses only partially filled with the liquid 

 medium were used. The test media consisted simply of distilled water 

 containing, accurately, the specified concentration of the salts. The 

 control medium, when used, was a filtered culture liquid from the native 

 culture of the Stentors employed. In presenting the results of experi- 

 ments the origin of the Stentors is always stated by giving the number 

 of the mass-culture. Nearly all of the animals used in the following 

 experiments came from the same or a few continued cultures. The 

 results are therefore all the more comparable. Customarily I placed ten 

 Stentors in each dish, and prepared either five or ten dishes (in all fifty 

 or a hundred Stentors) of each medium to be tested. All the prepara- 

 tions described under the serial number of a single experiment were 

 made simultaneously and carried on under strictly identical surroundings. 

 Further details of the above procedure have been given in the section 

 on General Methods and Technique (p. 444). 



The mean result states the number of individuals to which, on the aver- 

 age, one Stentor increased or diminished in the given time. My general 

 experience in the use of solutions has taught that for my purposes the 

 number of molecular parts iu 100,000 is an appropriate measure of their 

 concentration from a physiological point of view. 



Series 1. Expt. No. 45. April 8, 1902. 



(All Stentors originated from culture No. 20318.) 



.01000 m. KC1. 



Time hr. 29 hr. 



No. of Stentors 100 6? 



No. of Divisions 



Mortality 94 



Mean Result 0.06 



.01000 m. NaCl. 



Time hr. 29 hr. 



No. of Stentors 100 



No. of Divisions 



Mortality . 100 



Mean Result 



