44 THE ORIGIN OF THE NERVOUS SYSTEM 



are still present, for a time, but after a few days in 

 alcohol they are completely absent in all cases examined. 



Since the chemical reaction concerned here is an 

 oxidation-reduction the rate and amount of reduction of 

 permanganate must be associated in some way with the 

 oxidative activity of protoplasm, the regions of higher 

 rate of oxidation showing a higher rate and greater total 

 amount of reduction. We find that the permanganate 

 gradients correspond with those demonstrated by other 

 methods, i.e., the more active and more susceptible 

 regions reduce permanganate more rapidly and in larger 

 amount than the less active and less susceptible. This 

 method is a very delicate one and I believe of consider- 

 able value as a means of determining regional and axial 

 differences in physiological state, particularly in small 

 organisms. 



In certain cases the indophenol reaction has been 

 used to demonstrate the existence of axial gradients in 

 blastulae and gastrulae. This reaction is an oxidation 

 which is catalyzed by oxidizing enzymes and which 

 results in the formation of indophenol in the form of a 

 blue precipitate. In living starfish blastulae and 

 gastrulae (Child, 191 5#) a distinct apico-basal color 

 gradient has been observed by this means, the forma- 

 tion of indophenol occurring most rapidly in the cells 

 of the apical region. If the animals are killed by some 

 other agent before the indophenol reaction, the blue 

 color is much less marked and the gradient is absent. 



THE EVIDENCE FROM BIOELECTRIC PHENOMENA 



Axial gradients in electric potential have been found 

 to exist by Drs. Bellamy and Hyman in axiate animals 



