70 CLASS T.— ORDER II. 



NEMERTESIA. 



Plant-like and horny; garnished through its 

 whole extent with small polypiferous oils, curved to- 

 wards the stem, and verticillated ; cells placed on the 

 inner part of the cil. 



The Nemertesias, not numerous in their species, 

 are distinguished from the Sertularias, with which 

 they have hitherto been classed, by a variety of cha- 

 racters that belong to them exclusively, and which 

 do not allow us to confound them with any of the 

 genera which compose that Order. 



These Polypidoms are sometimes branching, some- 

 times not branching ; in the latter case, their general 

 appearance resembles a mouse's tail ; in the first case, 

 they cannot be compared to any thing, their aspect is 

 peculiarly their own. 



Their cells are invisible to the naked eye, bare, 

 and always placed on the interior part of the cils, a 

 single one at each articulation. 



The numerous ovaria are axillary to the cils and 

 stem. 



The substance of the Nemertesias is membranous, 

 horny, and very flexible ; they become almost trans- 

 parent by desiccation. 



Their colour, when first taken from the sea, is a 

 beautiful citron-yellow, sometimes orange; they be- 

 come dull and whitish when exposed to the air and 

 light. 



Their height varies from two to five decimetres. 



The Nemertesias are never parasites on marine 



