THE ACTINIANS OF PORTO RICO. 
357 
aggregation which produces the granular character of the brown coloration observed in the living 
tentacles. McMurrich makes no mention of the peculiarity in his specimens of A. annulata, but 
records and figures a very similar condition in Heteractis lucida (1896). 
The walls of the stomodreum are thrown into numerous small folds, except at the gonidial grooves, 
which are clearly indicated in sections. Cilia are present all around the stomodteum, but are longer 
at the grooves. Deeply-staining granular gland cells and long nematocysts are present in the 
stomodaeal ectoderm, and the nerve layer is very evident in places. Muscle fibrillse occur on the 
endodermal face of the mesogloea. 
In three Jamaica specimens dissected transversely only the eight Edwardsian mesenteries extend 
the whole length of the stomodteum; the ventral moities of each of the four lateral pairs, or what are 
known as the fifth and sixth developmental pairs, are complete in the uppermost region, but for the 
greater part of the stomodteal extent they are free (fig. 43). Three of the Porto Rican specimens 
dissected exhibited the same condition of the primary mesenteries, so that it may be assumed to be a 
general characteristic of the species. Six pairs of mesenteries form a second cycle and are never 
complete; twelve pairs constitute a third cycle, and twenty-four a fourth cycle. The last project 
but a little way beyond the column-wall, and do not bear retractor muscles. In one specimen only 
the second and third cycles bear the gonads in the lower stomodaeal region; in another the four free 
mesenteries belonging to the primary cycle also bear gonads. The directives extending from the angle 
of the gonidial grooves are shorter than the other complete mesenteries. The large inner mesenterial 
stomata are easily seen in dissections, and the outer are large marginal apertures some distance from 
the upper extremity. 
The retractor muscles on the three first cycles of mesenteries are strong and form a thickened 
band along the greater part of the face of each mesentery. The muscle commences a little beyond the 
origin of the mesentery at the column-wall and, slowly enlarging in thickness, ends centripetally in a 
rather abrupt manner. The parieto-basilar muscle is well developed, and also the basilar muscle. 
The mesenterial endoderm in the lower region exhibits cells with clear contents; granular gland 
cells and zooxanthellae also occur. The mesenterial filaments are provided with ciliated and glandular 
streaks. They are remarkable for the thickness of the endoderm on their outer aspect, which gives 
them a very exceptional appearance (fig. 44). The middle lobe is somewhat digitiform in transverse 
section and greatly prolonged beyond the lateral lobes. 
Acontia are abundant and contain large thick-walled nematocysts, closely arranged. One example 
sectionized contained ova arranged in long, narrow, single rows on the mesenteries of the second and 
third cycles in the upper part, of the stomodaeum. They were more plentiful around one pair of direct- 
ives than around the other. In another specimen both ova and sper maria occurred together on the 
second and third cycle mesenteries, and also on the free fifth and sixth pairs of the primary cycle, so 
that the species is hermaphrodite. McMurrieh’s specimens bore immature ova only on the mesenteries 
of the second and third cycles. 
This large and handsome Aiptasia is found plentifully all around Jamaica, firmly attached to 
various objects, such as stones, rocks, and old shells, often to their under surface, the disk with the 
long tentacles showing above the sea-floor. Sometimes it attains considerable dimensions, having 
quite an impressive appearance when seen in situ with all its long, snake-like tentacles waving grace- 
fully. A variety is occasionally met with in which the diameterof the whole disk and tentacles is 18 or 20 
centimeters. In these the outer tentacles are of the usual granular brown color, with white, incomplete 
rings, but the inner tentacles are a very pale blue, with only a few urticating areas toward the apex, 
and when fully extended they are extremely delicate objects. The Porto Rican specimens are on the 
whole smaller than similarly preserved Jamaican examples. The large size which the species occasion- 
ally attains places it more in agreement with Lesueur’s A. solifera, the body of which is stated to be 
about 4 inches in length (1817, p. 173). McMurrich has already discussed (1889, p. 10) the reasons for 
uniting the two forms, A. solifera and A. annulata, regarded by Lesueur as distinct species, and the 
large Jamaican specimens serve to confirm his conclusions.' 
The polyps appear very sensitive to light, contracting when exposed to full sunlight in the 
laboratory, but expanding again if placed in the shade. The long tentacles are usually in constant 
and graceful motion and are incapable of being much retracted. Acontia are emitted both through 
the cinclides and the mouth. 
