CONTROL OF ORGANIC POLARITY 483 



By a careful study of these drawings the following facts 

 appear : 



1. The greater the current density the greater the inhibition 

 of regeneration. This occurs to a lesser extent in the end which 

 happens to be turned toward the anode than in that turned 

 toward the cathode. 



2. There is a lower current density, branch I, below which 

 regeneration takes place in practically a normal manner. It 

 should be noted that in branch I the regeneration at the apical 

 end of all the internodes preceded that at the basal end; i.e., 

 the electric current did not overcome the inherent polarity of the 

 pieces in branch I. This means that with respect to the effect of 

 the current there is something which is similar to a threshold 

 density. Compare the orientation of Paramecium in an elec- 

 tric current. 



3. Regeneration on the end toward the cathode, branches II, 

 III, and also IV, is inhibited to a greater degree (if not com- 

 pletely) than regeneration on the end toward the anode, irre- 

 spective of whether the apical or basal end of the internode is 

 pointed toward the cathode. 



4: The density of the electric current necessary to inhibit 

 (delay) regeneration in apical internodes is greater than that 

 necessary for inhibition of regeneration in more basal internodes 

 of the same branch. That is, the threshold density for inhi- 

 bition of apical internodes is higher than for basal internodes, 

 other conditions being the same. This statement corresponds 

 to the fact that apical internodes in the absence of the current 

 regenerate sooner than more basal internodes of the same branch. 

 Branch I was practically normal in its regeneration and might 

 as a matter of fact serve as a control for the results in branches 

 II, III, and IV. 



The result in this experiment does not differ from that in 

 experiment I, for if we had selected internodes from the level of 

 branches corresponding to that of the middle region of branch 

 III for example, and left them to regenerate for forty-five hours 

 instead of thirty-four hours then we should have expected the 

 same results. 



