PHYSIOLOGICAL SENESCENCE IN HYDROMEDUS^. 



55 



certain limit or may even decrease. The facts suggest that the 

 high concentrations may decrease permeability to themselves, 

 at least up to a certain limit where their action becomes violently 

 destructive to protoplasm, and so practically instantaneous. 



In Table III., HC1 and Table IV. KOH, the action in stopping 

 pulsation increases very rapidly with increasing concentration, 



TABLE III. 



jEquorea: SUSCEPTIBILITY TO HC1. 



proportionately much more rapidly than the concentration, 

 because more or less acclimation to the lower concentration 

 occurs. In HCI 777/1500 not tabulated acclimation occurs 

 in the young animal to a greater degree than in the old. After 

 five days in this concentration the young animal still shows well- 

 marked rhythmic pulsation after mechanical excitation while 



