96 C. M. CHILD. 



evident that the beginning of death does not stop the reduction 

 of permanganate, and even after death is complete the reaction 

 occurs to some extent. The slight regional differences in rate of 

 reduction which sometimes persist for a time after death is 

 apparently complete may perhaps mean that certain death 

 changes, e.g., inactivation of oxidizing enzymes, stabilization of 

 oxidizable substance, are not yet complete, but at most these 

 differences are mere vestiges of the original differences. 



And finally, the regional differences in the total amount of 

 reduction cannot be due to differences in the permeability of 

 limiting surfaces. In the light of all the facts concerning the 

 physiological gradients, the only conclusion at present justifiable 

 seems to be that they are associated with and dependent upon 

 differences in the chemical, and particularly the oxidative activity 

 of the protoplasm concerned, though it is, of course, granted that 

 various factors are concerned in these chemical differences. 

 The reduction gradients appear only when living protoplasm 

 reacts with permanganate, or as mere vestiges in protoplasm 

 very recently killed. The regions of greatest amount of reduction 

 are the regions of greatest physiological activity, as indicated by 

 growth, development, susceptibility, electro-negativity, and in 

 those forms for which it has been determined, of respiratory 

 activity. I believe we are justified in concluding that, when 

 used with proper precaution and in connection with other 

 methods, the rate and amount of reduction of potassium per- 

 manganate by organisms which are alive at the beginning of the 

 reaction serves as an indicator of the fundamental physiological 

 condition of the protoplasm. This conclusion holds, not only 

 for hydroids, but for all other forms examined (Child, '190). 



SUMMARY . 



Hydroids and hydromedusae placed in dilute solutions of 

 potassium permanganate show characteristic axial gradients in 

 rate and total amount of reduction of permanganate, as indicated 

 by the coloration of the protoplasm by MnO2 or other products 

 of the reaction. These gradients correspond with the physio- 

 logical gradients indicated by other methods and by the develop- 

 ment, growth-form and functional activities of the organisms. 



