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 Linnseus 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 Poli, 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 - 
tus and four others, which are now ranged under the type of 
the mollusca, and also of the genera Spirorbis, and some others, 
which 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 
