44 



C. M. CHILD. 



tion of the septa in the region of the incision is indicated dia- 

 gramatically by the dotted lines. With the approximation of the 

 obhque margins of the cut the cut ends of the septa are also 

 closely approximated, and since the oesophagus closes in the 

 same manner as the body-wall the consequence is that some of 

 the interseptal chambers distal to the apical region of the cut be- 

 come almost or completely closed aborally, while lower down, 

 where more new tissue is formed between the old margins of the 

 body-wall they remain more widely open. When the body is 

 distended with water those chambers which are nearly or quite 

 closed aborally remain almost or wholly collapsed, since they 



19 



are nearly or quite isolated from the other parts of the enteron, 

 and the pressure resulting from the more rapid distension of other 

 parts aids still further in closing small openings which may re- 

 main. After the distension resulting from the passage of water 

 through the body -wall or septa has subsided this region remains 

 collapsed and the tentacles corresponding to those chambers 

 begin to atrophy. But in the further course of regulation after 

 closure the area of new tissue increases and the old margins of 

 the cut, now united by a thin membrane of new tissue, gradually 

 separate as it increases, and the relations of the septa also un- 

 dergo regulation in consequence. At a certain stage the inter- 

 septal chambers which were shut off from other parts of the 



