J. E. Durrpen—Jamaican Actiniaria: Part I.—Zoanthee. 367 
Tentacles.—The tentacles have a very broad ciliated ectoderm crowded with 
narrow elongated nematocysts, zooxanthellae, and pigment granules; the meso- 
gloea and the endoderm are thin. The longitudinal ectodermal muscle is well 
developed on small mesoglceal plaitings. 
Dise.—The ectoderm of the dise is broad and contains nematocysts, zooxan- 
thelle, and pigment granules in the deeper parts. The mesogloea thickens 
towards the middle, and incrustations are there present. The endoderm is like 
that of the column-wall. 
sophagus.—The outline of the cesophagus varies in different regions and in 
different specimens. In most polyps it is the usual pyriform, truncated shape, 
with the ectoderm thrown into seven or eight longitudinal folds on each side, and 
the cesophageal groove well marked and occupying nearly one-third of the trans- 
verse diameter ; but in others, it may be almost circular in outline with none of 
the folds showing. The ectoderm is very thick, stains deeply, is richly ciliated, 
and loaded internally with yellow pigment granules, and outwardly with elon- 
gated nematocysts. The mesogloea is narrow, thickening a little at the groove ; 
the endoderm is like that of the column-wall. 
Mesenteries (Pl. x1x., fig. 7).—The mesenteries present the usual brachyenemic 
arrangement in most cases; but, as already mentioned, irregularities may occur, 
so that a polyp may be brachycnemic on one side and macrocnemic on the other, 
while one polyp has been met with which has the latter arrangement on both sides. 
The number of pairs is variable, and the two lateral halves do not always corre- 
spond. In a portion of one colony two polyps have eight perfect mesenteries 
on each side; two have eight on one side and seven on the other; while another 
has six on one side and eleven on the other. The imperfect mesenteries are well 
developed. The endoderm is very thick, and contains zooxanthelle, nematocysts, 
and abundant pigment matter. The parieto-basilar muscle is clearly seen on 
each side, but the retractor muscle layer is scarcely distinguishable. The mesogloa 
is extremely thin, except towards the column-wall, where the canals or sinuses 
extend nearly the whole vertical length; they occupy almost the whole transverse 
width in the uppermost region, but are elongated or oval below. The basal canals 
are well developed in both the perfect and imperfect mesenteries, and are 
crowded with oval nematocysts and pigment particles, and connected below 
with the sinuses in the ccenenchyme. The ectoderm of the cesophagus is 
reflected and folded on the mesenteries. The endoderm on the lower part of 
the mesenteries is enormously thickened and loaded with granules; the mesen- 
terial filaments become nearly circular. 
Gonads (Pl. x1x., fig. 6)—Spermaria, arranged in vertical and transverse 
rows, were present in the mesenteries of some of the polyps examined. 
