Factors of Form Regulation in Harenactis Attenuata 487 



that quoted. I believe that much more extensive series of experi- 

 ments are necessary as a foundation for such a conclusion and it is 

 my experience that the more varied and extensive the experimenta- 

 tion, the less teleological do the reactions appear. In certain cases, 

 at least, the "choice" of a method of reaction, of w^hich Moszkow- 

 ski speaks, is nothing more than the fact, clothed in teleological 

 language, that the structure of the animal is such that only a cer- 

 tain reaction is possible. It might be said for Cerianthus and 

 Harenactis, for example, that in the oesophageal region, the 

 reaction is chosen w^hich brings the cut edges of body-wall and 

 oesophagus together and so hastens restitution. However, 

 when we find that such a reaction occurs aborally as readily 

 as orally although in this case it renders continued existence 

 impossible, it becomes evident that there is nothing adaptive 

 or teleological about it. When we actually analyze it instead of 

 assuming its teleological character, we find that it results primarily 

 simply from the fact that all tissues of these species contract when 

 wounded and freed from the tension resulting from enteric fluid. 

 This being the case, the anatomical arrangement of parts deter- 

 mines that the method of closure shall be different in the oesopha- 

 geal and the suboesophageal regions. The reaction occurs in the 

 characteristic manner in each region, whether it leads to the death 

 of the individual or to complete restitution. Something more 

 convincing than the facts recorded in this paper of Moszkowski's 

 are necessary before we can accept his conclusions. 



II THE DIFFERENTIATION OF NEW PARTS 



The visible stages of the diflperentiation of new structures re- 

 quires only brief consideration because Harenactis does not differ 

 widely from Cerianthus (Child '03a). The disc and tentacles 

 are formed by redifferentiation of the most distal portions of the 

 body-wall of the piece, together with the new tissue which closes 

 the wound (Figs. 16-17). When the level of section is in the oesoph- 

 ageal region the union of the cut edges of body-wall and oesophagus 

 leaves the distal end of the old oesophagus widely open as a mouth 

 (Figs. 8 and 16), but in the suboesophageal region the oesophagus 



