INTRODUCTION. XXV 



one section of the Polyzoa, the Ctenostomata, of which 

 the well-known Bowerbankia is a characteristic example 

 (\Yoodcut, 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, which is placed high up 

 in cases in which 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 of the 

 intestine to the pharynx. In this case the resophagus 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 

 digestive sac. The extremity of the 

 caecum is separated from the rest of 

 the stomach by a narrow passage or . 

 channel, and has the appearance of a BiceUaria ^iota. 

 distinct chamber suspended below it Lower part of stomach. 

 (Woodcut, fig. x.). This csecal appen- ** Caecal a PP^age. 

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

 the walls 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 appcn- 



