FORM-REGULATION IN CERIANTHUS. 97 



isting in the cesophageal pieces described in a previous paper 

 (Child, '04^). Consequently water can enter this portion only 

 by diffusion or as a secretion. 



The lower (/. <?., aboral) margin of the transverse cut and the 

 oral end of the body on the uncut side present similar conditions 

 (Fig. 2). In both regions the union of oesophagus and body- 

 wall produces conditions apparently favorable for typical tentacle 

 regeneration ; in both the intermesenterial chambers are in free 



o 



communication with the main enteric cavity and distension and 

 free movement of the circulatory currents is therefore possible. 



It is clear from the diagram (Fig. 2) that each of the discs will 

 form a mouth. The relations of these two mouths is also suffi- 

 ciently evident from the figure. 



If the conclusions reached in preceding papers ('04/7, '04^, 

 '04^) are valid we may expect that tentacle-regeneration will 

 occur in the typical manner on the oral margins of the body of 

 the uncut side and on the aboral margin of the transverse cut, 

 i. e., the lower margin which corresponds to an oral end with 

 respect to that part of the body aboral to it. 



On the oral end of the body over the transverse cut regener- 

 ation must be delayed if internal water-pressure is effective, since 

 only the slight distension due to diffusion or secretion is possible 

 in this region. The history of the piece fulfills all expectations. 



For convenience the regenerating region at the oral end of the 

 piece may be designated as terminal and that on the side of the 

 body as lateral. It is also necessary to distinguish between the 

 cut side of the body, that on which the lateral cut is made and 

 the uncut side. 



Regeneration of the marginal tentacles has already begun in 

 this piece (Fig. 2) ; the terminal marginal tentacles on the uncut 

 side are I mm. in length, those on the cut side are minute buds 

 0.25-0.5 mm. in length. The lateral marginal tentacles are about 

 0.5 mm. in length. In appearance they are more advanced than 

 the terminal tentacles on the cut side but somewhat less advanced 

 than those on the uncut side. The portion of the body between 

 the lateral cut and the oral end is very evidently less distended 

 than the other parts. 



November 6.- -Thirteen days after section. Terminal mar- 



