ABRANCHIATiE. 463 



ORDER III. 

 ABRANCHIATE. 



The Abranchiatse have no apparent external organ of respi- 

 ration whatever, and appear to respire, some, like the Lura- 

 brici, by the entire surface of the skin, and others, like the 

 Hirudines, by internal cavities. They have a closed circulat- 

 ing system, usually filled with red blood, and, like all the An- 

 nelides, a knotted nervous cord(l). Some are also provided 

 with setae which enable them to crawl, and others are de- 

 prived of them. This has caused their division into two 

 families. 



FAMILY I. 



ABRANCHIATE SETIGERE. 



This first family comprises the Lumbrici and Naides of 

 Linnaeus. 



LuMBRicus, Lin. 



The Earth-worms, as they are commonly called, characterized by a 

 long, cylindrical body, divided by rugae into a great number of 

 rings, and by an edentated mouth, necessarily required to be subdi- 

 vided. 



LUMBRICUS, CuV. 



Eyes, tentacula, branchiae and cirri, all wanting; a tubercle or visible 

 enlargement, particularly sensible in the nuptial season, serves to 

 attach the two sexes to each other in coitu. The intestine is straight 

 and rugose, and in the anterior part of the body we observe some 

 whitish glands which appear to be concerned in the process of gene- 

 ration. The Lumbrici are certainly hermaphrodites, but it is poss- 

 ible that their coalescing may serve to excite them to the act of 



(1) For the anatomy and physiology of tlie abrancliiate Annelidas see the Me- 

 moir of M- Ant. Duges, Annales des Sciences Naturelies, Sept. 1828. 



