J. E. Durerpen—Jamaican Actiniaria: Part T.—Zoanthee. 847 
In none of the specimens could the disc and tentacles be noted externally ; 
the individuals, as appears to be usually the case, maintaining a retracted condition. 
Colour.—Ccenenchymatous base colourless in some, irregularly greenish brown 
in others ; column dark brown, mottled with green and black, the pigment appear- 
ing in granular form. The green colouring matter seems largely external, and 
due to adhering unicellular alge. 
Dimensions.—Diameter of base may be 1°7 em.; diameter at commencement 
of column varies from 0:4 cm. to 1 cm.; average diameter of column 0°6 cm. ; 
height, from 2°2 em. to 4:2 em.; tentacles, measured in sections, 0°3 em. long. 
Localiity.—Seven specimens were found associated and firmly adhering to a 
small block of coral-rock on the south-east side of Drunkenman Cay. 
Column-wall.—The cuticle on the outside is devoid of adhering foreign matter, 
except in places where a unicellular green alga is attached, giving rise to the 
greenish patches seen on the living animal. The sub-cuticla is of regular thick- 
ness, but enlarged a little where it communicates with the internal mesoglea by 
strands across the ectoderm. The ectoderm is thick; the nuclei of the individual 
cells show no regular zonal arrangement; it is broken up by the strands of 
mesogloea into somewhat cubical or spheroidal blocks ; large, thick-walled, highly 
refractive zooxanthellae, and occasional large colourless stinging cells are present 
in places. In the uppermost part of the column the sub-cuticla is absent, and 
the ectoderm continuous. The internal boundary is often not clearly defined, 
portions being, as it were, cut off and isolated, and, as still smaller parts, often 
only individual cells, sunk further into the mesoglcea. 
The mesogloea is very thick, and contains abundant cell-inclosures, and uni- 
formly distributed small cells with granular protoplasm. In the lower parts more 
especially these take the form of small communicating canals. M*Murrich refers 
to the alteration in histological structure which some of the cells undergo in the 
mesoglea, by which they become filled with refractive, deeply staining granules, 
and suggests (p. 118) that they may be concerned in the formation of the 
mesoglea, their granules being particles which will later on be added to the 
matrix of the mesoglea. Many of the cells in my sections, generally in limited 
areas, appear to go a stage beyond, and instead of the granules filling the cells, 
they become arranged peripherally, giving the appearance of a thickened granular 
cell-wall, a distinct central nucleus remaining (fig. 6, Pl. xvi. A). 
The endoderm is thin, and contains abundant zooxanthellee and small stinging 
cells. A circular endodermal muscle occurs along the greater part of the length 
of the column. Endodermal bays are met with at different levels, extending 
nearly as far as the ectoderm, and evidently correspond with the thin annuli 
noticed amongst the external characters. The endodermal muscle follows the 
outgrowths for only a short distance. Perhaps the bays serve to give flexibility 
3G2 
