BRITISH ZOOrHYTES. 203 



mouth (m) opening into the oesophagus (oe), which 

 passes into the stomach (s), from which the intestine (i) 

 leads to the anal orifice (a). The oesophagus, stomach, 

 and intestine, with the tentacular corona, form the 

 polypide, which may be described as suspended by the 

 lophophore in the cavity of the zooecium. The polypide 

 is kept in its place and regulated by the muscles (r) 

 and funiculus (z), which will be afterwards described. 

 This description applies to nearly all the Polyzoa, but 

 a few species grouped as Entoprocta have both orifices, 

 the oral and the anal, within the lophophore, and, as 

 has been stated, in the fresh-water Polyzoa (except 

 Paludicella) the mouth of each polypide is protected by 

 the epistome. 



The zooecium consists of an external part or ectocyst, 

 and an internal lining or endocyst. Connections be- 

 tween the different zooecia in a colony are kept up by 

 means of openings in the ectocyst called communi- 

 cation plates (Plate XVI., fig. 4). The endocyst is a 

 transparent membrane forming a lining of living proto- 

 plasm to the zooecium. In Oristatella the ectocyst is 

 absent, and the endocyst presents the appearance 

 below of a flattened disc resembling the foot of a 

 gasteropod, on which the colony creeps about on the 

 stems of plants, &c. The many and beautiful forma 

 which the zooecia of the various members of this class 

 assume will be pointed out in the description of the 

 species, the appearance and arrangement of the zooecia 

 being important elements in classification. 



The polypide requires a more detailed description. 

 Commencing* with the tentacles, we fiind them to be 

 hollow, closed at the extremities and opening inwardly 

 into the cavity of the zocecium. They are borne upon 



