4-OO LIBBIE H. HYMAN. 



basal parts are used" can expect nothing but irregular and 

 inexplicable results. By using such methods and failing to de- 

 scribe them it is possible to accumulate data which appear to 

 contradict everything that previous workers have obtained. As' 

 long as no one takes the trouble to inquire by what procedures 

 such data were obtained and as long as the author refuses to 

 furnish any information about his methods, such data might 

 stand on record indenfiitely in the scientific journals to puzzle 

 future investigators. I believe that I have conclusively shown 

 that Banus's data are completely invalidated by his experimental 

 method. This work and that of previous investigators Driesch, 

 Morgan, Child, Stevens, and Alice demonstrate incontestably 

 that in Tubularia when other factors are equal the rate of re- 

 generation of pieces of equal size depends upon the level which 

 they occupied in the intact stem; it is more rapid the nearer the 

 pieces lie to the original distal end of the stem. A metabolic 

 gradient exists in the stem of Tubularia which is the primary cause 

 of these regional differences in rate of regeneration. 



H. SUMMARY. 



1. This experimental work was undertaken as a reply to a 

 paper published by Banus ('18). 



2. The existence of a metabolic gradient in the stem of Tubu- 

 laria is demonstrated in this paper in four different ways. 



(a) Differential susceptibility of apical and basal regions of 

 the stem to ether and cyanide. Apical regions are more suscep- 

 tible. 



(b) Differential capacity of apical and basal regions to reduce 

 potassium permanganate. The apical end of the organism has 

 the greatest reducing power. 



(c) Difference in electrical potential along the stem. Apical 

 regions are electronegative (galvanometrically) to basal levels 

 within the limits of the individual. (At a certain distance from 

 the original hydranth of Tubularia a new individual is arising 

 and the apical end of this is likewise electronegative to regions 

 anterior to its level.) Since in general electronegativity is asso- 

 ciated in protoplasm with increased oxidative metabolism, this 

 difference in electrical potential along the stem of Tubularia is 



