FORM REGULATION' I\ CERIAXTHUS .KSTUARII. 39 



lowed by the formation of tentacles. Below the oesophagus no 

 tentacles formed because here no closure of the wound took place. 



A month after the operation the pieces possessed the form 

 shown in Fig. 12. The most distal part of the oral end was bent 

 over so that the oblique disc was applied to the side of the body 

 in the region of the opening below the oesophagus. The disc 

 bore a semicircle of marginal tentacles which showed the usual 

 differences in length of tentacles. 



These pieces are of interest because they show an extreme 

 type of reaction to the wound, but even in this case the reaction 

 seems to consist essentially of contraction of the cut edges of the 

 body-wall. The fact that this contraction produces so marked 

 a change in the position of the oral end is due merely to the 

 position of the cut. 



III. Experimental Change in Length and Atrophv 

 OF Tentacles. 



The marginal tentacles are 40-50 mm. in length when fully 

 distended and the labial tentacles about 10 mm. Exact measure- 

 ments are of course out of the question. Reduction and atrophy 

 of the tentacles can be induced in this species as in C. solitariiis 

 by preventing distension of the body and tentacles. As has been 

 noted above, openings in the body-wall do not entirely prevent 

 distension, even when frequently reopened, for provisional closure 

 occurs, sometimes within a few minutes after reopening. These 

 provisional closures, however, cannot withstand anything like the 

 normal internal pressure, so that even when they occur the total 

 distension is very much below the normal. 



In one series of this kind the tentacles were reduced in fifty 

 days from full length to mere stumps, the marginal tentacles 

 being 2 mm. in length and the labials just visible as slight eleva- 

 tions. Atrophy of the tentacles proceeds in the centripetal direc- 

 tion as in C. so/itarius, and at the tip of each tentacle a small 

 mass of degenerating tissue is visible (cf. Child, '04^, Figs. 3-5). 

 If the specimens are allowed to close and become distended after 

 atrophy of the tentacles, growth of the tentacles begins anew and 

 proceeds according to the degree of distension established. 



Tentacle-atrophy is a characteristic feature of pieces taken 



