XXll INTRODUCTION. 



The walls of the true digestive sac, like those of the 

 oesophagus, are furnished with transverse muscular fibres, 

 by means of which the vigorous peristaltic movement, 

 which plays so important a part in the digestive process, 

 is secured. 



From the upper part of the stomach, and near the point 

 where the oesophagus or the cardiac cavity (as the case 

 may be) rises from the main digestive sac, the intestine 

 (Woodcut, fig. i^ int) takes its origin, and passes upwards, 

 terminating in an orifice which opens out through the ten- 

 tacular sheath at a short distance (Woodcut, fig. vi. a) 

 from the base of the corona"^. 



Near the lower extremity of the intestinal tube is placed 



Fig. viii. 



Alimentary canal of Cellepora. 



ph. Pharynx, cc. Cardiac chamber, st. Stomach, pv. Pyloric Testibule. 



p. Pylorus, a. Anus. 



the pyloric valve, which regulates the admission of the 

 rejectamenta into it. Sometimes the valve is borne on 



* The position varies: in some cases the anal opening is situated much 

 lower down on the side of the zooecium ; in Alcyonidium gelatinosum it is 

 represented by Farre as occurring at the base of the setose operculum — 

 that is, about halfway down the cell. 



