POLYZOA 607 



between the mouth and the anus, and many nerves chiefly supplying 

 the tentacles and gut. There are no special sense organs. No trace of 

 a vascular system exists. 



A remarkable phenomenon very characteristic of the Polyzoa is the 

 formation of the brown body. Tentacles, gut, in fact the whole of the 



m,retr. 



staU — IL' 



Fig. 416. View of right hali of Plumatellafungosa, slightly diagrammatic. After 

 Allman and Nitsche. an. anus ; bzv. body wall ; ep. epistome ; fn. funiculus ; 

 ga. ganglion ; int. intestine ; Iph. lophophore ; M. mouth ; m.retr. retractor 

 muscles of polypide; oe. oesophagus; ov. ovary; p.m. parietal muscles; sp. 

 spermatozoa; st. stomach; stat. statoblast; t. testis; t.' the same, more 

 mature ; tb. wall of tube ; ten. tentacles. 



polypide, degenerates and forms a brown, compact mass. A new poly- 

 pide is regenerated from the zooecium and the brown body often 

 comes to lie in the new stomach and is evacuated through the anus. 

 This periodical renewal of the individual is a normal process in most 

 polyzoa. It was formerly explained as due to the accumulation of 



