152 J. E. Durerpen—Jamaican Actiniaria : 
tentacles does not, however, yield any stinging cells. Gland cells are not developed 
in the marginal tentacles to the same extent asin the column-wall. The endodermal 
muscle is continued into the tentacles only as a very thin layer, the mesoglea not 
being plaited; but, in the naked region of the disc, directly from the base of the 
tentacles, it is again strongly developed on mesogleal plaitings, and extends the 
whole width of the naked area, practically disappearing again as the disc tentacles 
are reached. ‘The ectoderm of the disc, though still containing gland cells, is 
narrow, but the endoderm becomes enormously thickened, and presents the 
appearance of an extremely loose vesicular tissue. In the disc tentacles, the ecto- 
derm and mesoglcea are thin, but the large cavity is almost filled with the loose 
endodermal tissue, among which are numerous zooxanthelle and medium-sized 
ovate nematocysts, with a loose thread thrown into four or five loops; an 
extraordinarily large stinging cyst is met with here and there. These latter are 
enormous, horn-coloured cysts when mature, and bear tubercular or spine-like out- 
growths. ‘They are by far the largest met with in any anemone described from 
this region (Pl. x1, fig. 4). 
The constituent cells of the endoderm readily separate on maceration. The 
supporting cells are of the usual type, but longer, and the free extremity is 
ciliated; the small nucleus occurs about the middle of the length. In places 
where one or more zooxanthelle are enclosed the cell is greatly swollen. 
The stomodzeum is round in transverse section, but short vertically, and its 
walls are very deeply folded in the latter direction. These foldings which are so 
marked a feature amongst the external characters are seen on anatomical exami- 
nation to be elevations of the ectoderm followed by the mesoglea, but not by the 
endoderm. ‘They often branch even more than is shown in M*Murrich’s figure 
(1889, Pl. 1v., fig.3). The ectoderm presents the usual characters, having a clear 
peripheral zone ciliated on the outside, a broad middle zone of oval deeply- 
staining nuclei, and a narrow fibrillar zone. Nematocysts of various sizes are 
present, including the large, colourless cysts with a spiral thread. A feeble 
longitudinal musculature can be detected. The endoderm is much like that of 
the column-wall, but deeper, and fewer zooxanthellz and no nematocysts occur. 
The endodermal muscle is clearly distinguished, and rather strong, arranged on 
small mesogleeal plaitings. 
As already remarked by Prof. M°*Murrich the arrangement of the mesenteries 
is difficult to determine, and appears very irregular in the alternation of perfect 
and imperfect pairs, as does also the number of pairs. In addition to the complete 
mesenteries an imperfect series is well developed, extending some distance within 
the ccelenteron, and, in certain regions, a second incomplete order is also formed. 
The pairs are closely situated at about equal distances all the way round, the 
endoceles and exocceles being of nearly equal width ; the endoderm of the column- 
