362 
BULLETIN OF THE UNITED STATES FISH COMMISSION 
cavities varying somewhat in size and outline in transverse section. Toward the lower extremity the 
linear character is almost lost, the chambers becoming irregularly arranged. 
The form of the sphincter here represented should be compared with that which McMurrich 
gives of the same species (1898, pi. i, lig. 6; pi. ii, ligs. 1, 2). It will be seen that they present 
certain differences as regards the arrangement of the muscle-bearing cavities. Neither McMurrich’ s 
description nor figures give any indication that the cavities are arranged in transverse rows, though 
he speaks of an appearance of two or three longitudinal bands of mesogloea. The reticular region 
occurs in both instances, but occupies a much larger proportion in the Cuban polyp; in the latter the 
remaining cavities are irregularly arranged, while they form very distinct rows in the polyps now 
under examination. 
The differences between the two are so great that one would be inclined to doubt their specific 
identity. In other polyps which I have sectionized, however, intermediate conditions are met with. 
Sometimes only a slight indication of the linear arrangement of the rows is exhibited, and the reticular 
portion also varies much in extent. I am inclined to regard the differences in the character of the 
sphincter as in some measure dependent upon t he age of the polyp. The specimen from which fig. 45 
was taken was a young polyp only about two-thirds of a centimeter in diameter. McMurrich’s single 
specimen (2.7 cm. in height, the diameter near the base about 2 cm.) was a medium-sized individual. 
Other examples which I have studied, and in which the appearance more nearly resembles that 
of the Cuban polyp, are also mature. It may be that with age the regularity of the chambers charac- 
teristic of young polyps becomes broken up. Were it merely an individual variation the possibility of 
a sphincter muscle of any species exhibiting such marked differences would greatly lessen the value 
which has been placed upon it for taxonomic purposes. 
The tentacles display a very broad ectoderm, loaded peripherally with narrow nematocysts. 
The longitudinal muscle fibers are moderately well developed on deep, narrow mesogloeal plaitings; 
the endoderm presents irregular internal boundaries, the cells being much vacuolated. A strong 
endodermal muscle occurs and pigment matter is present in some abundance, but no zooxanthelho 
occur within the endoderm of this or any part of the polyp. Professor McMurrich (1893, p. 182) also 
found a bright reddish orange pigment everywhere in the endoderm of Adamsia involvens, without 
mention of any zooxanthelke. 
The three layers of the disk much resemble those of the tentacles, but the ectoderm is nearly 
devoid of nematocysts and contains many gland cells. Both the endodermal and ectodermal discal 
muscles are strongly developed toward the tentacular region, but do not become mesoglceal. 
The stomodfeum is much folded in sections, and the gonidial grooves are only feebly indicated. 
The ectoderm is richly ciliated all round; narrow nematocysts and glandular cells with granular 
contents are observable toward the periphery of the layer, while the broad, deeply staining nuclear 
zone occurs below. The mesogloea and endoderm are very thin; an ectodermal nerve layer and 
endodermal musculature occur. 
Six pairs of perfect mesenteries occur, two pairs of which, the directives, are radially shorter 
than the others. Six pairs of secondaries alternate, and are never complete; four pairs of tl»e c e bear 
mesenterial filaments more abundantly coiled than on the other two. Twelve pairs of mesenteries 
form a third cycle, and the mesenterial filaments on these are but slightly developed; twenty-four 
pairs of very short mesenteries form a fourth cycle. Representatives of a fifth cycle are present in 
large polyps, but the full number, forty-eight, appears to be rarely reached. The second, third, and 
fourth cycles bear the gonads in three examples sectionized transversely. Hints of a dorso-ventrality 
in the polyps are indicated in that the reproductive organs may not be present on a few of the mesen- 
teries around one of the pairs of directives, while they are fully developed at the opposite aspect. In 
two young polyps only the first, second, and third mesenterial cycles were present. The third cycle 
of twelve was very fully developed, though no trace of the members of the fourth cycle could be found. 
The mesenteries are usually thin at their origin from the body-wall and broader beyond. The 
retractor muscles occur on branching mesogkeal plaitings, extending over the greater part of the width 
of the mesenteries. In the second cycle the retractor muscle may be somewhat circumscribed in 
character. The endoderm becomes much thickened below the stomodceum, and contains many 
granular particles and a little brown pigment matter. The parieto-basilar muscles appear to be absent, 
or, at any rate, no mesogheal pennons are formed for their support. McMurrich was unable to find 
any basilar muscle, but a very feeble pair occurs, as represented in fig. 46. 
