O. L. INMAN 175 



algas to the chloroform was never more than 96 minutes. After an 

 excessively long exposure to the chloroform (10 to 15 hours) about 

 95 per cent of the cells stained; in this case there is Kttle doubt that 

 most of the cells were killed, but such long exposures were never used 

 in the ordinary experiments. 



Staining was also tried after treatment with hypertonic salt solu- 

 tions. Here partial recovery, was found and yet not more than 5 to 

 8 per cent of the cells stained. In these experiments the longest 

 time of exposure to the salt solution was about an hour. If the 

 cells were treated for from 5 to 8 days with hypertonic NaCl about 

 95 per cent stained. 



It would therefore appear that a treatment with hypertonic salt 

 solutions which lowers the rate of respiration so much that recovery 

 is incomplete kills few or none of the cells. If this be true then it 

 cannot be said that partial recovery is due to the fact that some of 

 the cells are killed by the toxic agents while others recover com- 

 pletely. The fact that the recovery is not complete must be due to 

 the diminished metabolism of practically all the cells. 



SUMMARY. 



The respiration of Chlorella is diminished by exposure to hyper- 

 tonic salt solutions. After a short exposure there is complete 

 recovery when the algae are removed to the normal medium. After 

 a longer exposure recovery may be incomplete, as shown by the fact 

 that the rate of respiration fails to rise to the normal level. Staining 

 with methylene blue indicates that few, if any, of the cells are 

 killed as the result of the exposure. It would therefore seem that 

 the treatment produces a persistent lowering of the rate of metab- 

 olism. Such a condition of metabolism is also found after exposure 

 to chloroform. 



