ON ANNELIDA. 77 



tribes, which, adhering to immerged bodies, appear in fact to 

 creep upon their surface, from the great number of inflexions 

 which they form there. 



Notwithstanding the labours of Linnaeus and his editor 

 Gmelin, it was only since the introduction of the consideration 

 of the animal into the systematic disposition of shells and testae 

 in general, a consideration owing to Pallas, to Poll, and after- 

 wards to MM. Cuvier and de Lamarck, that any kind of cer- 

 tain order could be established in the great genus Serpula of 

 Gmelin. M. de Lamarck was the writer whom the nature of 

 his labours most necessarily conducted to this task, and to him 

 is owing the definitive establishment of the genera Verme- 

 ius and four others, which are now ranged under the type of 

 the moUusca, and also of the genera, Spiro7' bis, and some others, 

 w hich have remained among the chetopoda or annelida, along- 

 side of the true Serpula. Nevertheless, it would appear that 

 science did not possess any just character whereby to distin- 

 guish the tribes which belonged to the mollusca from those of 

 the chetopoda, until it was furnished by M. de Blainville. 

 We shall briefly notice his distinction here. A tube or funnel 

 of a molluscous animal, usually free through a great part of its 

 extent, is never pierced at its extremity or summit, and its 

 cavity often presents a series of partitions, which are formed 

 in proportion as the animal in growing larger, has been obliged 

 to abandon the most narrow part of it ; sometimes this part of 

 the shell is entirely filled and solid, as in mugil. The testa 

 of a chetopod, or tubicola, however solid it may be, is, on the 

 contrary, constantly, at least at its origin, fixed, applied by its 

 ventral face, on a foreign body, and does not rise more or less, 

 except towards its termination, which varies according to the 

 form and the extent of the sub-posed body. It is always 

 pierced obliquely towards its origin or its summit ; and there 

 are no partitions or divisions whatsoever in any part of its 

 cavity. This is in strict relation with the organization of the 



