FORM REGULATION IN CERIANTHUS. 65 



wholly incorrect. The question as to whether osmotic phenom- 

 ena play a part in the changes above described requires, however, 

 a moment's consideration. As regards the inrolling after section 

 and the reduction in size of the collapsed pieces there is certainly 

 no reason for supposing that it is due to changed osmotic condi- 

 tions. It is difficult to understand how, in a form like CcriantJius 

 section of the body-wall at one level should cause changes in 

 turgor in the cells of the whole piece or of those at a distant 

 region unless we suppose that special stimuli producing these 

 changes arise from the region of the cut. If this be the case 

 then the change is not primarily osmotic but reactive. More- 

 over, the phenomena are so obviously due to elasticity that the 

 search for any other explanation is clearly unnecessary. 



THE ROLE OF THE SLIME SECRETION IN THE CLOSURE OF THE 

 ENTERIC CAVITY AFTER SECTION. 



As has been shown, the inrolling of the margins of the piece 

 under ordinary conditions approximates the various parts of the 

 cut surface, and thus reduces the size of the opening. The radi- 

 ating wrinkles and folds into which the inrolling portions are 

 thrown and the frequent protrusion of parts of the mesenteries 

 through the opening render the closure by contact imperfect. 

 There are always slits and angles between the various parts, 

 through which the enteric cavity is in communication with the 

 exterior. 



In spite of this fact I have often found pieces distended with 

 water, before any closure of the ends by new tissue has occurred. 

 A series of experiments in which the body-wall was sectioned 

 transversely at some level and the oral portion, still bearing ten- 

 tacles and disc intact, was used, will serve to illustrate this point. 

 In every case collapse of the tentacles and body occurred imme- 

 diately after section, owing to the escape of water from the en- 

 teron, but very frequently the whole oral piece including the ten- 

 tacles was again distended with water in less than an hour. 



O 



Examination of the aboral cut end in such cases showed that 

 inrolling and approximation of the margins had occurred, but 

 frequently distinct spaces between the wrinkles could be observed 

 opening into the enteron. If the end were spread open with 



