352 



Florence Peebles 



SERIES 4 B 



Old proximal row retained, new distal in front 22 



New anlage 8 



Total number 3° 



The method of completion of the hydranth on the proximal piece 

 {B) when the original row persisted, in Series I and 2 was that 

 described by Driesch as the "Ersatzanlagemodus," a new distal 

 row developed in front of the proximal row before the hydranth 

 emerged. That in Series 4 was Driesch's " Regenerationsmodus " 

 where the hydranth emerged first, and later a new row of distal 

 tentacles developed. I agree with Child ('07c) that there is no 

 essential difference in the two methods. 



CONCLUSIONS 



These experiments prove that before the ridges have become 

 visible, changes have taken place in the tip of the stem that render 

 it when isolated incapable of producing a complete hydranth. 

 These changes however do not take place until several hours 

 after the wound has closed. If the tip is removed shortly after 

 closure of the wound, even as long as twenty-four hours after the 

 first operation, it is still possible for the isolated tip to form a com- 

 plete hydranth. After the proximal tentacle anlage has appeared 

 the distal piece when isolated, even if the tentacle ridges are not 

 visible, does not form a complete hydranth. Instead the distal 

 tentacles and mouth develop. 



7 REVERSING THE DISTAL ROW OF TENTACLES 



In earher experiments ('00) I have shown that when the tip 

 of the oral end of a long piece is cut off, reversed, and grafted back 

 again at once, that the new hydranth develops in exactly the same 

 region as it would have if the piece had not been removed. The 

 distal row of tentacles appears in the small piece and the prox- 

 imal row in the longer one. In the following experiment the tip 

 was not removed until after the distal row of tentacles had appeared 

 (Fig. 20). The piece A was then removed and grafted in 



