178 J. E. DuERDEN — Jamaican Actiniaria : 



feeble circular endodermal muscle is, however, present in the perioral region of 

 the disc. 



The tentacles in this species therefore differ from those of the two previous 

 forms in not having a capitulum histologically distinct from a stem, and also in 

 not being much differentiated in structure from the disc itself. 



Towards the middle of the disc, that is, in the naked area, the details, however, 

 approach more closely those of the column ; gland cells, with highly refractive 

 contents, occur in the ectoderm, and the endodermal muscle is stronger. 



The wall of the stomodseum is much folded, both vertically and transversely. 

 The ectoderm is broad, ciliated throughout, and bears numerous, long, granular, 

 gland cells, and a less number of oval-shaped nematocysts, much larger than those 

 of the tentacles. A very weak ectodermal musculature is discernible. The 

 endoderm is slightly pigmented like that of the disc and tentacles, and contains a 

 few highly refractive gland cells. 



A transverse section through the polyp, in the middle stomodseal region, shows 

 to the naked eye the following details : — 



Twenty-five pairs of mesenteries, all of which are complete ; of these two 

 pairs are directives, so that of the other pairs, twelve occur on one side, and 

 eleven on the other. No incomplete mesenteries are developed. A single deep 

 gonidial groove, with very smooth walls and much thickened mesoglcea, is included 

 between one of the pairs of directives, but no indication of a second is presented 

 in connexion with the opposite pair. 



The inner mesenterial stomata occur just within the lips, and the outer a little 

 from the column-wall, about a centimetre below the sjDhincter muscle. Both 

 are rather large apertures of about equal size. The retractor muscles of the 

 mesenteries are large, thick, oval, or reniform projections from one face, and are 

 attached by only a narrow, short pedicle ; on the opposite face of the mesentery 

 a very distinct pennon arises a little beyond the insertion of the mesentery in the 

 column-wall. 



In a section below the stomodseal region, the same twenty-five pairs of 

 mesenteries occur, and, with their mesenterial filament and gonads, completely 

 fill the coelenteron. Towards the basal part of the column, alternate larger 

 and smaller pairs are exhibited, but irregularities occur, in one region 

 seven pairs being of the same size. The number of mesenteries bearing 

 mesenterial filaments begins to diminish, until a little above the base they are met 

 with only on four. In the single example studied, the gonads were bright red in 

 colour, and a reddish oil was extracted by alcohol. 



The microscopic appearance of a portion of a mesentery , near its place of origin 

 in the column-wall, is represented in PI. xiii., fig. 2. The pennon is seen to be 

 strongly developed, and the mesoglcea long and deeply plaited on both sides. In the 



