I - 8 LOUISE H. GREGORY. 



The complete histories of several series showing their response 

 to treatment at different periods in the life cycle would indicate 

 clearly this variation in the activities of the protoplasm. Further 

 experiments are planned to emphasize this point showing the 

 instability of youthful protoplasm, the gradual increasing ability 

 of maturing protoplasm to adjust itself to changes in its medium 

 and finally the loss of this power as old age advances. 



These experiments with potassium and sodium phosphate 

 using series of different ages as well as the same series at different 

 periods in its life history, add further evidence to the theory of 

 Calkins (5), that changes are taking place in the derived organiza- 

 tion of the protoplasm of Uroleptus mobilis throughout the life 

 cycle. These results can not be explained as ordinary variations 

 in the division rate as the numbers of experiments are too many 

 and the results too uniform; neither can they be due to varia- 

 tions in the hydrogen ion concentration as that has been main- 

 tained practically the same as that of the control save in the one 

 experiment. Under certain conditions a low hydrogen ion con- 

 centration may be a secondary cause of the variation in response, 

 but the primary, underlying cause must be sought in the condition 

 of the protoplasm itself, its organization changing as the series 

 passes from the period of youth or immaturity, through one of 

 maturity and finally into that of old age. 



BARNARD COLLEGE, 



COLUMBIA UNIVERSITY, 

 NEW YORK CITY, 

 April, 1926. 



REFERENCES. 



1. Gregory, L. H. 



'25 BIOL. BULL., Vol. XLVIII., No. 3. 



2. Woodruff, L. L. 



'05 Jour. Exp. Zool., Vol. 2, No. 4. 



3. Packard, Charles. 



'26 Jour. Cancer Research, May. 



4. Austin, Mary. 



Unpublished. 



5. Calkins, Gary N. 



'26 Biology of the Protozoa. Lea and Febiger. 



6. Hartmann, M. 



'21 Arch. f. Protistenkunde, Bd. 43. 



