EFFECTS OF CHANC>ES OF MEDIUM. 



181 



2. Experiments with Di-sodiurn Phosphate. 



Two parallel experiments were carried on with di-sodium 

 phosphate as the initial treatment. In one set a N/iooo solution 

 of Na 2 HPO 4 was used for the 3O-minute initial dose, in the other 

 set a N/7000 solution of the same salt was used. The latter 

 strength was selected because it gives approximately the same 

 percentage of sodium when added daily to the normal medium 

 as that which caused a distinct increase in the rate of division of 

 Paramecium (Packard) and of Uroleptus (Austin). Table II. 

 gives the results of these experiments. 



TABLE II. 



THE EFFECTS OF AN INITIAL DOSE OF DI-SODIUM PHOSPHATE ON PROTOPLASM OF 



VARYING AGES. 



At this time series 129 B was the only young series available 

 for experimentation. This series was in the i8th generation and 

 after the treatment with both the stronger and weaker solution, 

 the division rate was lowered 1.4 divisions per line in the one 

 case and 4.4 divisions per line in the other case as compared with 

 the control series. The other nine experiments with individuals 

 that varied in age from the 63d to the 295th generation showed 

 the varying results that are characteristic of mature protoplasm, 

 the majority being stimulated by the treatment. A few were 

 slightly depressed and there was but little difference in the effects 

 of the two solutions. 



