FORM-REGULATION IN CERIANTHUS. 13! 



December 8. - - 1 7 days after section. Experimental pieces : 

 Since these differ somewhat from this stage on, each piece is spe- 

 cially designated by a letter which it retains throughout the re- 

 mainder of the experiment. In pieces a and b the longitudinal 

 cuts extend only about half the length of the piece, in c about 

 two thirds, while in d and e they extend more than three fourths 

 the length. 



(a] In this piece the longitudinal cuts are less deep than in the 

 others and the end closes more perfectly being less irregular. 

 At each examination before reopening the piece was more or 

 less distended with water. Marginal tentacles r mm.; oral end 

 partially expanded. 



(ft) This piece also succeeded in closing the aboral end more 

 or less perfectly by approximation of parts between the times 

 of reopening. Marginal tentacles 0.5-1 mm.; oral end partially 

 expanded, a small area of new tissue visible at center. 



(V) Has been only very slightly distended at any time : aboral 

 end has remained partly open most of the time except for slime. 

 The tentacular ridge bears only minute buds ; the oral end is not 

 expanded sufficiently to show the new tissue in the center. 



(W) Has been widely open aborally since December 2 : aboral 

 end torn in reopening and margins rolled inward in such manner 

 that a wide communication between enteron and exterior re- 

 mains. The oral regeneration of this piece has not advanced 

 visibly since December 2 ; the oral end is still unexpanded and 

 new tissue not visible at the center ; a tentacular ridge is barely 

 visible but tentacle buds are wholly absent. 



(V) Has remained most widely open aborally of all throughout 

 the experiment : oral end wholly unexpanded ; no tentacular 

 ridge and no trace of tentacles visible. 



Controls : All five pieces with oral ends expanded and show- 

 ing a distinct area of new tissue at center ; tentacles 1 1.5 mm. 



December 12.- -21 days after section. Experimental pieces. 

 Since December 8 have been reopened daily : 



(a and b) Oral ends slightly expanded, diameter less than that 

 of body ; marginal tentacles 1.5-2 mm., slightly longer in a than 

 in b ; blunt and less slender than normal tentacles (Fig. 2). 



(c} Oral end not expanded ; very minute tentacle buds on ten- 

 tacular ridge. 



