352 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
The specimens preserved in alcohol are now practically colorless; the tentacles, however, are 
slightly brown, due to the presence of brown pigment granules within the endodermal cells. 
The height of the larger specimen is 1 cm., and of the shorter 0.4 cm. The diameter of the 
column of the former is 0.8 cm., and of the basal disk 0.5 cm. In all probability the dimensions of 
living specimens would be much larger. 
Anatomy and Histology. — The basal disk possesses a very broad ectodermal layer, constituted of 
long narrow cells, many of which are peripherally charged with a yellowish granular secretion. 
The column-wall is moderately thin throughout. The ectoderm is a broad epithelial layer; the 
mesogloea nowhere becomes greatly thickened, while the endoderm everywhere is exceptionally low. 
The ectoderm consists mainly of glandular cells of two kinds — clear mucous gland cells and granular 
gland cells. The granular gland cells are so plentiful that it is very likely they give a certain degree 
of opacity to the tissues of the living polyp. Histologically the vesicular verrucse differ in no important 
respect from the remainder of the column-wall, except that the ectoderm contains numbers of small 
nematocysts. The verrucse are outgrowths from all the mesenterial chambers, the twenty-four rows 
of large vesicles being entocoelic and the smaller rows exoccelic in position. The acrorhagi are 
practically the same in structure as the other columnar outgrowths, but the ectoderm is a little higher 
than elsewhere and is abundantly charged with nematocysts, not, however, to such a degree as in the 
tentacles. The comparative fewness and small size of the nematocysts indicate that neither the vesicles 
nor the acrorhagi can be regarded as special batteries of nematocysts. In such organs the nematocysts 
are usually very large, thick-walled, and closely arranged. 
The mesoglcea of the column-wall presents a slightly fibrous appearance and contains small, 
isolated, connective-tissue cells; its external and internal surfaces are smooth. 
The endoderm throughout the polyp is remarkable for the shortness of its cells, these being 
scarcely half as long as the cells of the ectoderm, so that the layer everywhere is very narrow in 
section. Further, the cells are charged with brown or black pigment granules, whiclf tend to obscure 
the other constituents. The granules evidently take the place of the symbiotic zooxanthella: of other 
Actiniae, for these are everywhere absent in the present species. In other examples of the Bunodaclidx 
a similar substitution seems to take place. Pigment granules occur in Bunodospma granulifera, but 
zooxanthellfe are absent; in A nl actinia stelloides the conditions are reversed. Similar relations occur 
also among the Sagartid.r, but in some ZoantMdte, such as Polythoa, both granules and zooxanthellfe 
occur in the same polyp. 
The circular endodermal musculature is everywhere very feebly developed, except in the region 
between the outermost tentacles and acrorhagi, where it forms a characteristic circumscribed endo- 
dermal sphincter (fig. 36). Compared with that in many other Bunodartidie, the sphincter muscle is 
rather feeble, but is remarkable on account of the very distinct peduncle which it possesses. In truly 
radial sections, away from the insertion of a mesentery, the muscle is, as it were, suspended from the 
inner surface of the wall of the polyp, but near the mesenteries it is displayed as a thickened ridge of 
the wall, and the mesentery may appear as if attached to it. The mesoglceal plaitings of the muscle 
are very numerous, and are disposed almost wholly on one side of the axis — not, as is usually the case, 
more or less pinnately on each side of the median axis. 
The tentacles are of practically the same structure throughout their length. A uniform peripheral 
zone of long, narrow nematocysts extends from the origin to the apex. An ectodermal nerve layer 
is clearly shown, while the longitudinal muscle fibers are strongly developed on fine, subdendroid, 
mesoglceal plaitings, which are best seen in transverse sections. The tentacles being in the retracted 
condition, the mesoglceal layer is probably much thicker than would be the case in extended polyps. 
Here, as elsewhere in the polyp, the endoderm is a narrow layer with many pigment granules. In the 
tentacles the granules are often restricted to limited areas, other areas being wholly free from them; 
non-pigmented endoderm patches occur more plentifully toward the proximal extremity. Longitudinal 
sections of the tentacles display the ends of a weak, circular, endodermal muscle. 
The stomodfeum is wide and nearly circular in section, the ciliation being well preserved all 
round. The walls are thrown into numerous vertical ridges, which correspond somewhat with the 
internal attachment of the mesenteries, and are due to an increase in the thickness of the mesoglcea. 
The number of ridges, however, slightly exceeds that of the complete mesenteries, being from fourteen 
to sixteen on each side, while the mesenteries are only twelve on each side. The ridges become 
stronger in the lower region of the stomodamm, where many of the mesenteries have become free. 
