EFFECT OF EXCRETION PRODUCTS OF INFUSORIA 579 



fully eliminated, and eight (comprising two sets) were isolated in 

 media from flask which was uncontaminated with paramaecia 

 or hypotrichs. At the same time sixteen Stylonychia were 

 similarly isolated on separate slides and treated identically the 

 same as the paramaecia just described. There were then in this 

 experiment thirty-two lines of cells forming eight sets designated 

 as follows : 



Pol = paramaecia on uncontaminated medium 



Po2 = paramaecia on uncontaminated medium 



Pp = paramaecia on paramaecia contaminated medium 



Ph = paramaecia on hypotrich contaminated medium 



Hoi = hypotrichs on uncontaminated medium 



Ho2 = hypotrichs on uncontaminated medium 



Hh = hypotrichs on hypotrich contaminated medium 



Hp = hypotrichs on paramaecia contaminated medium 



This first experiment gave the following results which repre- 

 sent the average rate of division of the four lines of cells of each 

 set, again averaged for the ten days during which they were 

 continued : 



Pol = 2.25 divisions per (hij^ 

 Po2 = 2.31 divisions per day 



Pp = 1.95 divisions per day 



Ph = 2.46 divisions per day 

 Hoi = 4.50 divisions per day 

 Ho2 = 4.45 divisions per day 



Hh = 4.15 divisions per day 



Hp = 3.95 divisions per day 



This result is interpreted as showing that the P medium 

 decreases the division rate while the H medium increases the 

 division rate of Paramaecium. Further the H medium and the 

 P medium decreases the division rate of the hypotrichs. 



As the second example. Experiment 4 (February) may be cited. 

 This was continued for four days with the following result: 



Pol = 1.80 divisions per day 



Po2 = 2.05 divisions per day 



Pp = 1.35 divisions per day 



Ph = 1.95 divisions per day 



Hoi = 3.73 divisions per day 



Ho2 = 3.75 divisions per day 



Hh = 3.40 divisions per day 



Hp = 3.50 divisions per day 



THE JOURNAL OF EXPERIMENTAL ZO6LOGY, VOL. 14, NO. 4 



