FORM-REGULATION IN CERIANTHUS. 2O5 



No attempt at general application of this conclusion to mor- 

 phology need be made at present, though the field for speculation 

 is most attractive. I desire merely to call attention to the fact 

 that this regulative process belongs in the same category with 

 the changes in form of pieces of Stenostoma in consequence of 

 the attempts of these pieces to carry on their typical movements 

 (Child, '02, '03). In both cases the form is, speaking broadly, 

 the result, not the cause of the behavior. 



THE REGENERATION OF PIECES FROM THE CESOPHAGEAL 



REGION. 



Pieces with the oral cut surface at some level of the cesoph- 

 ageal region of the parent specimen and the aboral end at a 

 greater or less distance below the cesophagus differ from pieces 

 cut wholly aboral to the cesophagus only as regards rapidity of 

 regeneration. In such pieces, containing a part of the cesophagus, 

 the cut oral end of this organ unites with the cut body-wall and 

 thus a functional mouth is formed within a day or two after sec- 

 tion. Consequently such pieces become fully distended earlier 

 and the tentacles appear somewhat sooner than in pieces in which 

 a new mouth is regenerated. 



In pieces representing only the oesophageal region or part of 

 it (Fig. 7) the result usually differs widely from the preceding. 

 In such pieces the cut ends of the cesophagus usually unite both 

 orally and aborally with the cut body-wall and the cesophagus 

 forms a tube extending completely through the piece and open 

 at both ends to the exterior. Fig. 8 represents a longitudinal 

 section of such a piece : in order that the cesophagus and body- 

 wall may be readily distinguished in the diagrams the thin mus- 

 cular layer of the former is not indicated. In these pieces there 

 is no connection between the cesophagus and the enteron ; water 

 passing into the oral end of the cesophagus simply passes out 

 again at its aboral end. Each intermesenterial chamber is thus 

 shut !"off from all communication with the exterior and with 

 adjacent chambers. 



As regards tentacle-regeneration these pieces follow the usual 

 course during the first few days, becoming more or less distended 

 with fluid, which is secreted into the enteric cavity or diffuses 



