58 



YERMES. 



bristles and without a double blood-vascular system), including 

 Sipunculidse and Priapulidae; and Armata or Chsetiferi (with 

 corneous bristles and a double blood- vascular system), =Echiuridae 

 and Sternaspidas. The latter is, however, referred by Olaus to 

 Polychaeta. Chafoderma, placed in Priapulidae by the same 

 authority, has the body furnished with spines. 



SipuncuWda. Priapulida. Bonellia. 



Sipunculus= Syrinx. Priapulus. Thalassema. 



Phascolosoma. Anoplosomatum. Ancistropus. 



Aspidosiphon. Chaetoderma. 

 Diesinga. Sterne 



Dendrostomum. Echiurida. Sternaspis. 



Echiurus. 



Class Y. ANNELIDA. 

 ANNUL ATA. 



Body composed of numerous segments [somites], the limbs 

 rarely present, or, if present, rudimentary [parapoclia]. A vas- 

 cular system with red blood, but without corpuscles, in most. 



The skin is soft, composed of many layers, the surface mostly 

 ciliated, the cilia bristle-like, and often fasciculate ; the segments 

 are sometimes to the number of 400. There is occasionally a 

 rudimentary head [prostomium] ; it bears two or more cirri or 

 tentacles (antennae and palpi), sometimes, but rarely, jointed. 

 The blood -vascular system is very variable, but is composed mainly 

 of longitudinal canals. The blood is rarely propelled from behind 

 forwards. 



There are no true parasites in this class, except some Hiru- 

 dinea ; but inquilines or commensals are sometimes met with. 

 Very few species are terrestrial. 



The genera Polyophthalmus, Dero, and Capitella form the 

 Haloscolecina of Carus. Anarthropoda is a divisional name, used 

 to include this and the two preceding classes. 



Mouth suctorial HIRUDINEA. 



Mouth not suctorial. 



Without branchiae OLIQOCB^TA. 



With branchiae. 



Branchiae dorsal CH^ETOPOD A. 



Branchiae cephalic CEPHALOBKANCHIA. 



