280 ARTICULATA. 



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 

 furnished with tentacula or filaments, to which, notwithstanding their 

 fleshy nature, some modern naturalists give the name of antenna; ; and 

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

 shining points, usually considered as eyes. The organisation of their 

 mouth varies greatly. 



ORDER I. 



TUBICOLA. 



SOME of the Tubicola form a calcareous, homogeneous tube, probably 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; the tube of others again is entirely membranous or 

 horny. To the first belongs the genus 



SERPULA, Linnceug. 



The calcareous tubes of the Serpulse'twine round and cover stones, shells, 

 and all submarine bodies. The section of these tubes is sometimes round, and 

 sometimes angular, according to the species. 



The body of the animal is composed of numerous segments; its anterior 

 portion is spread into a disk, armed on each side with several bundles of coarse 

 hairs, and on each side of its mouth is a tuft of branchiae, shaped like a fan, and 

 usually tinged with bright colours. At the base of each tuft is a fleshy fila- 

 ment, one of which, either on the right or left, indifferently, is always elongated, 

 and dilated at its extremity into a variously formed disk, which serves as an 

 operculum, and seals up the orifice of the tube when the animal has withdrawn 

 into it. 



Serp. contortuplicata. The most common species; its tubes are round, three 

 lines in diameter, and twisted. The operculum is infundibuliform, and the 

 branchiae are frequently of a beautiful red colour, or variegated with yellow, 

 violet, &c. Vases or other objects thrown into the sea are soon covered by 

 its tubes. 



