J. E. Durrpren—Jamaican Actiniaria: Part I.—Zoanthee. 355 
Drunkenman Cay; sometimes the polyps are partially embedded in sand and 
débris. Numerous young individuals arising directly from the ccenenchyme, or 
from the base of other polyps, are mingled with the older examples. 
Column-wall (Pl. xvut., fig. 10).—The ectoderm is continuous, and not much 
broken up by incrusting matter. The cuticle is thin, with few adhering foreign 
bodies. The ectoderm is broad in the distal part of the column, but narrows 
below, and the nuclei of the cells are uniformly distributed except near the cuticle, 
a regular columnar epithelium not being formed. Large oval nematocysts occur, 
and large zooxanthelle are present in company with small narrow stinging cells 
and cells containing highly refractive pigment granules. The inner boundaries of 
the ectoderm are not well defined, and at the capitulum the layer becomes very 
thick and still more irregular in its internal outline; definite bays or growths into 
the mesogloea appear in sections, probably due to the presence of capitular ridges 
and furrows. 
The mesogleea is of medium thickness, enlarging a little both proximally 
and distally ; the incrustations are limited to the outer portion and the adjacent 
ectoderm. They occur very sparingly, not interfering with the cutting of thin 
sections, and consist of calcareous and a few siliceous sand grains, sponge spicules, 
and an occasional Foraminiferal or Radiolarian test. The mesogloa contains 
isolated cells and cell-islets distributed with some uniformity, except in the lower 
part where an irregular zone of larger inclosures may be found a little nearer the 
inner boundary. The larger islets contain zooxanthelle, large oval nematocysts, 
and occasionally pigment granules similar to those in the ectoderm, from which 
layer the cell-islets can be seen to originate. 
The endoderm is thin, more so than in @. variabilis, and contains many zoox- 
anthelle. The circular endodermal muscle is well developed ; fine fibrils from it 
stretch nearly across the mesogloea, and others are seen connecting the various 
cells and cell-islets. 
Sphincter muscle (Pl. xvi. A, fig. 10).—The sphincter muscle is single and 
mesogloeal. It is long and situated near the endoderm. Proximally it commences 
in small irregular cavities in groups of two or three, and arranged in a not very 
regular row. The more distal cavities are much larger, irregular in form, and 
extend further across the mesogloea ; the muscle fibres are arranged obliquely, and 
isolated spherical cells occur. The muscle is shorter, the cavities less regular in 
arrangement, and not in such a single series as in G. variabilis; while the upper 
ones are closer, broader, and more irregular in outline. 
Tentacles—The ectoderm of the tentacles is very thick, and consists of an 
outer zone of small narrow nematocysts, and an inner zone of zooxanthelle and 
nuclei irregularly arranged. A few pigment granules, a number of homogeneous 
3H2 
