INTRODUCTION. XXV 



one section of the Polyzoa, the Ctenostomata, of which 

 the well-known Boiverbankia is a characteristic example 

 (Woodcut, fig. ix.) . We find its equivalent, however, in 

 many of the Cheilostomata. This consists of a prolon- 

 gation of the stomach upwards in the line of the oeso- 

 phagus, extending to the cardia, Avhich is placed high up 

 in cases in w^hich this appendage is largely developed. 

 (Woodcuts, figs. vi. & viii. cc.) In the former of these 

 figures, representing the polypide of Bugula plumosa, 

 this cardiac chamber appears as a globular dilatation, 

 occupying the lower portion of what in other species 

 would be the oesophagus; in the latter [Cellepora) it is 

 elongate-oval in form, and extends from the base o£ the 

 intestine to the pharynx. In this case the oesophagus is 

 reduced to the pharyngeal cavity, while the stomach is 

 proportionately enlarged. The walls of the cardiac cham- 

 ber are thickly covered by the hepatic glands. We must, 

 I think, recognize in this structure the homologue of the 

 gizzard, whose place it fills. 



In some species a peculiarity is ^^" ^" 



noticeable in the lower portion of the , ,?k 



digestive sac. The extremity of the Ni^^A 



csecum is separated from the rest of W^\ 



the stomach by a narrow passage or ^^^ ^" 



channel, and has the appearance of a Bicdlaria dUata. 

 distinct chamber suspended below it Lower part of stomach. 

 (Woodcut, fig. X.). This cffical appen- '''■ ^^'"'^^ appeudage. 

 dage is formed, according to Joliet, by a thickening of 

 the Avails of the stomach at a certain point. It shares 

 in the vigorous peristaltic movements of that organ ; 

 the food is carried into it from above, and then forciblv 

 driven back into the upper compartment. This appen- 



