ANIMALIA ARTICULATA. Ill 



ORDER II. DORSIBRANCHIATA. 



Branchiae in the form of tufts, arbusculae, laminae or tuber- 

 cles placed upon the middle of the body, or along the sides ; 

 most species live in the mud, or swirn freely in the sea ; a 

 few have tubes. 



GENUS APHRODITA, Lin. 



Back covered by two longitudinal ranges of scales, under 

 which are concealed the branchiae ; body usually flat, short 

 and broad. 



ORDER III. ABRANCHIATE. 



No apparent branchiae ; respiration by the surface of the 

 skin, or, as it is thought, in some by internal cavities; the 

 greater part live free in the water or mud, some in the moist 

 earth. Two families ; one of which have setae, the other is 

 without any. 



FAMILY I. ABRANCHIATE SETIGEILE. 



One remarkable genus. 



; V LUMBRICI, Lin. Earth-Worms. 



Body long, cylindrical and formed by a great number of 

 rings ; no eyes, tentacula or branchiae ; mouth without teeth ; 

 the common Worm is so widely disseminated as to be uni- 

 versally known; its body, which sometimes attains the length 

 of a foot, includes more than one hundred and twenty rings, 

 each having eight hairs beneath ; it feeds on vegetable matter 

 or animal substances. 



Circulation of the Earth- Worm, PL 31, Fig. 1 : A, dorsal 

 vessel ; B, abdominal vessel ; C, subnervous vessel ; D, mo- 

 liniform vessels or hearts ; E, deep seated abdomino-dorsal 

 vessels ; F, superficial abdomino-dorsal vessels. 



The mixed blood of the dorsal vessel A is conveyed, by 

 the contractions of the hearts D, into the abdominal vessel B, 

 which distributes it to the different parts of the body ; thence 



