430 



ZOOLOGY 



SECT. 



Each segment, with certain exceptions to be noted presently, 

 bears either a pair of parapodia or merely certain setae repre- 

 senting the parapodia. Parapodia are lateral hollow processes 

 of the body-wall bearing a number of bristles or setae. Fre- 

 quently the parapodium is divided horizontally into two distinct 

 lobes or branches a dorsal Avhich is termed the notopodium, 

 and a ventral which is termed the neuropodium. Even when 

 this is not the case there may be two bundles of setae repre- 

 senting the two parts. The setae are nearly always chitinous ; 



a L>d 



PIG. 337. A Serpulid(Vernrilia ccespitosa).- Lateral view of animal removed from its tube 

 abd. abdomen ; br. branchiie ; op. operculum ; th. thorax. 



in Et/p/<i'os-//ne they are calcified. They are hollow or solid, 

 entire or divided into a number of joints. In shape (Fig. 338) 

 they vary greatly in different groups; often several very dis- 

 tinct forms of setae are present in different parts of each para- 

 pndium of a single worm, or in parapodia of different regions of 

 the bod}-. Some are exceedingly delicate and hair-like, others 

 needle-shaped, others compressed and sabre-like, others bayonet- 

 like. Very often there is a long, straight, narrow part or handle 

 with which is articulated a terminal blade, or bayonet, or hook. 



