OONTEOL OF ORGANIC POLARITY 481 



stained and mounted according to the drawings made of the 

 pieces while in position in the trough m. No attempt was made 

 to retain the original orientation of the pieces in n, since this 

 was immaterial for the results of the experiment. The same 

 procedure in handling the material was followed in all the 

 experiments. 



The final result is shown in plate 1. A is the control in n and 

 B the set of internodes in m. 



Attention is called to the following facts: 1) The electric 

 current delayed hydranth formation on the end toward the 

 anode for about fifteen to twenty hours when compared to con- 

 trol. 2) Within the duration of the experiment hydranths 

 formed only on the ends toward the anode and in this experi- 

 ment in all the pieces, while no beginning of hydranth formation 

 nor growth occurred at the cathode end. This holds for all 

 pieces irrespective of whether the basal or apical end of the inter- 

 node was turned toward the anode. Compare this result with 

 normal development figure 3. The hydranths formed in 7n 

 appeared normal in form and behavior. 



Such complete orientation in all pieces was not obtained if the 

 current density was not suitable, for, as will be illustrated in the 

 following experiments, pieces from greatly different levels in the 

 same branch 'orient' to different densities of the electric current. 

 This experiment was not continued long enough to indicate 

 what finally would have happened at the ends toward the cathode 

 in m. 



In order to show, first, the effect of different current densities 

 upon the regeneration process and, second, the differences which 

 occur in regeneration of apical and basal internodes from the 

 same branch, the gradient trough figure 2, D, was used. 



Experiment 2. Four vigorously growing branches from the 

 same colony were used. The internodes from base to tip of 

 each branch were cut in serial order and this same order was 

 carefully retained when they were fastened in the cork strip. 

 No attention was paid to whether apical or basal end of the inter- 

 node was pointed toward the anode. The internodes from 

 branch number IV were placed in serial order on the cork strip 



