356 J. EK. Durrpen—Jamaican Actiniaria: Part I.—Zoanthee. 
deeply staining bodies, and glands filled with clear contents, are met with, and 
an occasional large oval stinging cell. Transverse sections show a well developed 
ectodermal muscle on mesogleal plaitings. The mesogloea has small cells 
scattered throughout. The endoderm is made up of small regularly arranged 
cells; an endodermal circular muscle is supported on fine mesoglceal plaitings ; 
and zooxanthelle are present. 
Dise.—The ectoderm of the disc is even thicker than that of the tentacles, and 
exhibits an outer zone of clear gland spaces and small narrow nematocysts. The 
deeper part is largely composed of zooxanthellae, glandular cells or spaces, and an 
occasional large oval stinging cell. An ectodermal muscle occurs on mesogloeal 
plaitings, and an endodermal muscle is present. The mesogloea is thick and 
contains cells and cell-islets, but is devoid of incrustations. 
sophagus.—Only a slight cesophageal groove is indicated, the mesogloea 
being a little thickened and truncate, and the directives extend from the two 
corners. Below it is oval-shaped in section, and the ectoderm remains unfolded ; 
distally the latter is thrown into eight or nine well marked folds on each 
side, only exceptionally followed by the mesogloea. In a second specimen, the 
number of folds was fifteen on each side. Immediately on passing, in longitu- 
dinal sections, beyond the lips of the mouth, the ectoderm undergoes a great 
alteration from that of the disc. It is richly ciliated, a narrow zone immediately 
below is colourless ; then follows a thick zone of narrow, closely-arranged nuclei, 
gland cells, and nematocysts, which together form a dense deeply staining band, 
extending the whole length of the cesophagus. A zone below this has only a few 
scattered nuclei, and, in places, the large oval stinging cells and pigment granules. 
The mesoglea is a homogeneous layer with rarely an enclosed cell, and the 
endoderm is extremely thin. A weak endodermal but no ectodermal musculature 
occurs. ‘Terminally the ectoderm is reflected upwards on the mesenteries for 
a short distance, and folded in a double pinnate manner, and then descends, 
constituting the mesenterial filaments. 
Mesenteries—The mesenteries are brachyenemic in arrangement. Twelve 
perfect pairs occur on each side in one specimen, and sixteen in another. In the 
middle cesophageal region each is extremely delicate, scarcely showing any 
enlargement towards the insertion at the body-wall or cesophagus; the usual 
basal canal is often absent, especially distally. The imperfect mesenteries are 
broad above, but very short below, not being readily distinguishable in places. 
The parieto-basilar muscle is present on each side; the retractor muscle is weak. 
A little beyond the insertion of the mesenteries is the flattened or oval-shaped 
basal canal filled with deeply-staining tissue, and now and then a large oval 
nematocyst. The endoderm is poorly developed, and has large zooxanthelle. 
Gonads.—No reproductive cells were present in the examples studied. 
