294 ANNULATA. 



Division of the Annulata into three Orders. 



This class, which contains but few species, presents a sufficient 

 basis of division in its organs of respiration. 



The branchias of some resemble tufts or arbusculee, attached to 

 the head or anterior part of the body: they, nearly all, inhabit tubes. 

 We will call them the Tubicola. 



Those of others resemble trees, tufts, laminae or tubercles in 

 which vessels ramify, and are placed on the middle of the body: 

 most of them inhabit mud or swim in the ocean, the smaller por- 

 tion being furnished with tubes. We name them the Dorsibran- 



CHIATA. 



Others again have no apparent branchiae, and respire, either by 

 the surface of the skin, or as some authors opine, by the internal 

 cavities. Most of them live free in mud or water; some of them 

 only, in humid earth. They are the Abranchiata. 



The genera of the first two orders are all furnished with stiff setae, 

 of a metallic colour, that issue from their sides, sometimes simply, 

 and at others in fasciculi, which serve in lieu of feet; but there are 

 some genera in the third order which are deprived of that support. 



The head of the Annulata of the two first orders is generally fur- 

 nished with tentacula or filaments, to which, notwithstanding their 

 fleshy nature, some modern naturalists give the name of antennae; 

 and several genera of the second and third are marked with black 

 and shining points, usually considered as eyes. The organization 

 of their mouth varies greatly. 



ORDER I. 



TUBICOLA. 



Some of the Tubicola form a calcareous, homogeneous tube, pro- 

 bably the result of transudation, like the shell of the Mollusca, with 

 which however they have no muscular adhesion; others construct 

 one by agglutinating grains of sand, fragments of shells and particles 

 of mud, by means of a membrane, also unquestionably transuded; 



