172 J. E. Dusrpen—Jamaican Actiniaria : 
while some of the free pairs were attached higher up. The members of the fourth 
cycle extended only a short distance from the column-wall. It would thus appear 
that the normal arrangement of the mesenteries in the stomodzal region of young 
polyps is as follows :—the first eycle of twelve pairs of perfect mesenteries consti- 
tutes the first and second orders; a second cycle is formed of twelve alternating 
pairs; and a third cycle of twenty-four pairs. Beyond this irregularities begin to 
step in. In older specimens many more than twelve pairs become united with the 
stomodeum. The region of the directives is always that of most forward growth. 
The mesenteries present a concave outline as they cease their connexion with 
the stomodeeum, so that in sections through the lower region of the latter the free 
edge of the mesenteries, bounded by a mesenterial filament, appears twice, one 
part bemg in connexion with the column-wall, and the other, shorter part with the 
stomodeeum. ‘The six mesenteries of the second series become free in advance of 
those of the first. 
The retractor muscles extend across nearly the whole face of the mesentery, 
but are nowhere much thickened, resembling somewhat those of S. helianthus. 
They differ in this respect from those of A. elegans, which are circumscribed and 
project considerably. 
The parieto-basilar muscle is strongly developed on both faces, and supported on 
numerous fine mesogleeal plaitings, but a separate pennon is not present, at any rate 
in the upper region. ‘The nervous layer and fibrillee are very distinct in this region. 
The retractor muscle commences abruptly and extends along the greater part 
of the face of the mesentery, terminating more gradually centripetally. The 
mesoglceal processes are long, narrow, and branching, and constitute nearly the 
whole of the thickness of the mesentery. The endodermal epithelium is very 
narrow comparatively, and contains numerous granular gland cells. There is little 
trace of any oblique musculature. The mesenteries are very narrow beyond the 
retractor region. 
The mesenterial filaments are typical in character, closely resembling those of 
Phymanthus crucifer, already described. ‘The trilobed condition occurs on the first 
two or three cycles, and is continued for but a short distance below the aboral 
termination of the stomodeum. The Nesseldriisenstreif or glandular streak at the 
apex of the middle lobe, is very limited in its extent, and the first portion of the 
intermediate streak is characterized by an abundance of small zooxanthellae. The 
Flimmerstreifen or ciliated streaks also occupy but a small region of the lateral 
lobes. The cells of the reticular streak contain but little protoplasm, while the 
mesogloeal axis in all three lobes is crowded with small, deeply-staining cells. 
Below the stomodzum the mesenteries branch considerably at their free 
extremity, each division being terminated by a simple, more or less rounded 
filament. As each side of the filament approaches the mesenterial epithelium, its 
