CONTKOL OF ORGANIC POLARITY 485 



In branch II thirteen internodes formed stolons on ends 

 toward the cathode, nine showed no growth toward the cathode, 

 within sixty-six hours, while only one internode from the 

 apical end formed a hydranth toward the cathode. Again no 

 stolons formed toward the anode. 



In branch I no stolons formed. Hydranths were more 

 numerous on the anode than on the cathode side, showing a 

 marked orienting effect of the current. However, the current 

 was not strong enough to bring .about any growth of stolons, 

 on cathode end, instead of hydranths, within the limit of sixty- 

 six hours. 



In removing the pieces of branches II and III, most of the 

 stolons were broken off, because of their attachment to the 

 side of the cork plate. Hence they are not shown complete in 

 the drawings. Pieces of cork are shown attached to some of the 

 stolons. 



The important fact which this experiment shows besides 

 confirming all the previous statements is that inhibition of hy- 

 dranth formation at the cathode in a suitable current density does not 

 mean that the capacity of this tissue to grow is lost, but rather that 

 the tissue can and does differentiate into a stolon which functions 

 normally, and this occurs irrespective of the original orientation 

 of the internode in the current. We have therefore fulfilled the 

 second requirement for a proof, page 479 above, that an electric 

 current of proper density can reverse the inherent polarity of an 

 internode and determine the direction of the physiological axis in 

 the piece according to which morphological development and 

 differentiation take place. 



It might be supposed that hght played a part in determining 

 the orientation, since growth in some hydroids shows a directive 

 effect due to light, e.g., Eudendrium. That light plays no part 

 in the result is evident from the control in experiment 1, also 

 branch I in experiment 2. Other experiments showed clearly 

 that light did not enter into the experiment as a directive factor. 

 The possible directive effect of the water current is ruled out 

 for the same reasons as those for light. 



