380 ■ JULIA ELEANOR MOODY 



than they would otherwise have been, then to a certain extent 

 Spathidiinn was rejuvenated by the beef-juice, by the treatment 

 of salts, and by the slight change in environment which the 

 cultures experienced when transferred from hay infusion to tap 

 water and later into spring water. 



Considerable difference was noted in the amount of reaction 

 manifested by the individuals of the same culture. In some 

 cases there was absolutely no response to treatment with beef 

 extract or salts, while other individuals showed varying degrees 

 of sensitiveness. 



If the individuality of the protoplasm of a culture subjected 

 to the same environmental conditions during a long period of 

 time show this marked difference in response to stimuli, it seems 

 reasonable to interpret the effects noted in Paramoecium, Oxy- 

 tricha, Tillina and Spathidium as identical in nature, differing 

 only in degree. 



Except during the last period represented in the curve of 

 the life-cycle, Spathidium showed no morphological changes 

 coincident with the lowered division rate. Through the first 

 twelve periods of the life history the appearance of the proto- 

 plasm was normal; Colpidium were consumed and digested in 

 large numbers. It was only at the very end of the series that 

 abnormal forms appeared, this abnormality being accompanied 

 by an extremely dense condition of the protoplasm. Without 

 doubt it would have been impossible to carry the cultures as 

 far as the 218th generation hdd not the use of beef extract, salts, 

 etc., been resorted to. Since Spathidium subsists exclusively 

 on Colpidium colpoda, of which it had an abundance, the grad- 

 ual degeneration of the cultures resulting in physiological death 

 must be traced to a lack in the food medium. The addition 

 of beef extract and salts of various dilutions changed to some 

 extent the chemical composition of the medium and as a result 

 the protoplasm showed a slight response. Owing to the fact 

 that the cultures, aside from a low division energy, showed no 

 signs of depression until the last ten-day period, I am inclined 

 to think the death of the series was due, not to senile degeneration, 

 but to abnormal conditions of environment and that death 



