Studies on the Life History of Protozoa. 433 



They died in twenty-four hours. The experiment was repeated 

 on July 14, three drops to five of hay infusion being used. On 

 the 15th they did not divide, on the 17th they divided once, and 

 died on the i8th. Experiment not repeated. 



c. Sodium Chloride. This salt was used on several occasions with 

 negative results as a rule. (See, however, table below.) In 

 September, 1902, when the race was comparatively vigorous, an 

 individual was treated for 30 minutes with f^ NaCL, one drop of 

 the salt to twelve of the hay infusion. At the end of 48 hours it 

 had divided once, but died within five days without further 

 division. The effect upon the protoplasmic structure was not 

 particularly noticeable (see Fig. 18). 



The following table gives a comparative view of the efficiency 

 of different salts on the division rate for thirty days subsequent to 

 treatment. Several individuals of the A series were treated on 

 the 20th of March with potassium phosphate and the progeny of 

 one of these in the 78th generation were again treated in part on 

 May 6 with potassium phosphate, and in part, with potas- 

 sium chloride, magnesium chloride, sodium chloride and calcium 

 chloride with the strengths, and for the times indicated. The 

 following notes were made at the time of the treatment. "When 

 the individual was put into the potassium chloride it began at 

 once to swim backward with great rapidity, and continued this 

 for about five minutes. It then straightened out and appeared 

 perfectly normal in the solution. When returned to the hay in- 

 fusion at the end of the treatment, it went through the same con- 

 vulsions but soon became normal, perhaps slightly swollen and 

 transparent." Again: "When the individual (another individual 

 of course) was put into the magnesium chloride solution it was 

 hardly affected in any way, a very slight increase in movement 

 being noticed." Again: "Treatment with NaCl did not affect the 

 individual, it appears fat and happy in the hay-infusion." Again: 

 "Very much affected by the CaCl2 solution. One of the three 

 specimens died; the other two were distorted and badly shrunken, 

 this lasted for at least fifteen minutes after they had been trans- 

 ferred to the hay infusion." 



