THE ANNELTDA. 



51 



being connected by lateral commissural cords with the post- 

 cesophageal ganglia. 



In many of these animals the body is divided into segments, 

 each of which corresponds with a single pair of ganglia of the 

 chain, and each of these segments may be provided with a pair 

 of lateral appendages ; but the appendages are never articulated ; 

 and are never so modified, as to be converted into masticatory 

 i organs, in the cephalic region of the body. 



No Annelid ever possesses a heart comparable to the heart 

 of a Crustacean, or Insect ; but a system of vessels, with more 

 or less extensively contractile walls, containing a clear fluid, 

 usually red or green in colour, and, in some rare cases only, 

 corpusculated, is very generally developed, and sends pro- 

 longations into the respiratory organs, where such exist. This 

 has been termed the "pseudo-haemal" system; and I have 



Fig. 24. 



Fig. 24. — Pohjnoc squamata. 



A. Viewed from above and enlarged. a,b. Feelers. c,d. Cirri, e. Elytra. /. Space left 



between the two posterior elytra, rj. Seta? and fimbriae of the elytra. 



B. Posterior extremity, inferior view, the appendages of the left side being omitted. 



h. Inferior tubercle. 



C. Section of half a somite with elytron, t. Notopodium, h. Xeuropodium. 



D. Section of half a somite with cirrus. 



E 2 



