REPRODUCTION 



207 



Environmental conditions which alter the permeability of the 

 cell, thereby enhancing or retarding metabolic activities do, how- 

 ever, have a corresponding effect upon the division rate. Age of 

 individuals, or the protoplasmic organization at different periods of 

 the life cycle likewise has a determining effect on the rate of division, 

 the differences, as shown in the following table, being due to the 

 differences in the reactions of the protoplasm to the same medium 

 under different conditions of organization. Series 111 and 112, for 



Uroleptus Mobilis Division Rate. 

 Experiment from September 2 1 to November 10, 1924. 



