ELECTRICAL POLARITY IN OBELIA 



489 



During the work represented in part by the experiments given 

 abo^•e, the impression was gained that the amount of the P.D. 

 in comparable pieces from different stems was distinctly different. 

 In some pieces of stem very little, if any, difference could be 

 detected, for example, table 4 A, stem 3, while in other pieces it 

 would be relatively large. Therefore it was decided to compare 

 in a preliminary way the magnitude and direction of the differences 

 between deflections when pieces from the apical and more basal 

 regions of the same stem were used. Three experiments were 

 carried out, in each of which five main stems of actively growing 

 colonies were used. In the first experiment two pieces from the 

 same stem were compared. The total length of each of the stems 



Apex 



Figure 2 



numbered 1 to 5 in table 5 were, respectively, 110, 80, 100, 110, 

 115 mm. Three cuts were made, as shown in fig-ure 2, x, y, 

 and z. The lengths of the pieces included between x and z in 

 stems 1 to 5 were, respectively, 75. 70, 64 and 66 mm. The cut 

 at y was made exactly in the middle so as to give two pieces A 

 and B of equal length. The tests on the A pieces are given in 

 table 5 A and the tests on the corresponding B pieces in B of the 

 same table. There is a distinct P.D. in the A pieces such that 

 the apical ends are all electronegative to the basal end of the same 

 piece. While in the B pieces the direction of the P.D. is reversed. 

 The magnitude of the P.D. varies but is quite distinct in every 

 case. A second experiment similar to the first except that the 

 cuts y and z, figure 2, were made proportionately nearer the apical 

 end of the stem, again showed that the apical ends of the A pieces 

 were electronegative and that in three of the B pieces the basal 

 end was electronegative to the apical end. The other two B 

 pieces showed no significant P.D. 



