33S 



Anatomy of the Ventriculites of Mantel, 



a somewhat radiated manner, as seen in Jig, 93. b ; and 

 similar processes pass 

 from the longitudinal 

 vessels, but are rarely 

 well preserved : they 

 may possibly be mere 

 membranaceous or 

 spongious processes, 

 for the purpose of 

 keeping the tubes in 

 situ ; but I am much 

 more disposed to consider them as tubuli performing the 



office of nutrient arte- 

 ^^ ries, and entering the 



substance of the ani- 

 mal to deposit the as- 

 similated pabulum for 

 its support. 



The External Coat, 

 — Of the structure of 

 this coat I have, from 

 my examinations, been 

 led to form a different 

 opinion from that of 

 Mr. Mantel; he de- 

 scribes it as " com- 

 posed of cylindrical 

 fibres, that extend in 

 a radiating manner 

 from a centre or base 

 to the outer margin, 

 and, by frequently sub- 

 dividing and anasto- 

 mosing, constitute a re- 

 ticulated integument, 

 capable ^of very con- 

 siderable contraction 

 and expansion. The 

 fibres are solid, and 

 when viewed through a lens, exhibit a porous structure, 

 bearing considerable resemblance to dried sponge. The 

 meshes, or interstices between the fibres, are narrow and 

 elongated in the specimens that are expanded, but very ir- 

 regular in those which are corrugated by contraction. In 

 some instances, slender transverse filaments extend from one 



