552 POLYZOA. 



elongated ciliated oesophagus, often dilated at its upper end into 

 a muscular pharynx ; (2) a spacious stomach with a blind backward 

 prolongation, the hind end of which is attached to the body-wall 

 by the funiculus ; and (3) a narrow intestine which is bent nearly 

 parallel with the pharynx, and is directed upwards. The intestine 

 opens by the anus, which is placed either within the tentacular 

 circlet (Entoprocta), or near but outside it on the body-wall (Ecto- 

 procta, Fig. 440). The anal side of the body is called the dorsal 

 side. In the Phylactolaemata the epistome and concavity of the 

 horseshoe lophophore are dorsal. 



The nervous system consists of a ganglion placed on the oeso- 

 phagus between the mouth and the anus (Fig. 441, go). It lies 

 in the space (ring-canal of lophophore) already described (p. 551), 

 which surrounds the oesophagus and is developed as a part of the 

 body -cavity. In the Phylactolaemata the ganglion is placed in 

 the concavity of the lophophore, and is attached to the oesophagus 

 by a delicate circumoesophageal ring : it contains a cavity which 

 arises as an ectodermal pit in the bud, and it sends off numerous 

 nerves to the tentacles and oesophagus. According to Fr. Miiller 

 there is in Serialaria (Zooltotryoii) a so-called colonial nervous system 

 which connects the individual zooids of a colony, and enables them 

 to coordinate their activities. Claparede describes the same in some 

 forms. Special organs of sense have not been recognized. 



Heart and vascular system are absent. The body-cavity is 

 absent in the Entoproda. In the Edoprocta it is spacious and 

 filled with fluid, and its lining gives rise to the generative cells ; 

 it is therefore to be regarded as coelomic, which view of it is justified 

 by the intertentacular organ of the Ectoprocta. This is a fine 

 ciliated tube leading outAvards from the body-cavity, and opening 

 externally between two of the tentacles on the anal side of the 

 lophophore. It is not found in all specimens, and, according to 

 Prouho, only in individuals containing an ovary. It functions as 

 an oviduct, and probably also as an outlet for the sperm. 



The body-cavity is divided, as stated above, into two parts, (1) the general 

 body-cavity and (2) the ring-canal of the lophophore which is prolonged into 

 the tentacles. The ring-canal is completely shut off from the general body- 

 cavity in the Gymnolacmata, but in the Phylactolaemata the two are in 

 communication on the dorsal (anal) side of the lophophore except in the middle 

 line, where the ring-canal is cut off from the general body-cavity by the 

 prolongation of the latter into the epistome. For the epistome of the Phylac- 

 tolaemata is hollow and contains a prolongation from the general body-cavity 

 which is continued upwards into it as a tube which passes on the anal side 



