194 TOILERS IN THE SEA. 



solid tubular structure, so long known to us, is at 

 length reached. 



" The mouth, which is circular, is distinctly marked, 

 and leads into the stomachal cavity, which is small ; 

 the stomachal cavity is separated by a thin and deli- 

 cate membrane from the general body cavity. I 

 have not been able to determine with exactness the 

 number of openings between these two portions. 

 The ovaries are in the general cavity, and are 

 invested by a delicate membrane, which is continued 

 in the form of eight mesenteric bands to the body of 

 .the tube. 



" The structure of the skeleton is certainly not 

 "crystalline, as some have suggested. Fusiform 

 spicules are secreted by the ectodermic layer ; 

 these spicules around the base of the tentacles 

 are of a white colour, and in many cases are simply 

 fusiform, not warty ; but those at a little distance 

 from the base of the tentacles not only assume a 

 light red colour, but become crowded over with warty 

 excrescences, and there is then to be found a gradual 

 growing together, and consolidation, of those around 

 the edge of the tube, that is, where this is formed. 

 In the case of a young bud, there is at first no tube, 

 the spicules having not yet become coalesced ; they 

 are here simply placed side by side. 



" The polyp certainly can, and does constantly, add 

 to the height of its tube ; or, in other words, the 



