104 
ME. H. N. MOSELEY ON THE 
lining the ccenenchymal tubes and calicles, and the median plates of the mesenteries, 
part of the wall of the stomach, &c. The layer immediately beneath the ectoderm is 
pierced by the superficial system of canals and traversed by the projecting points of 
the corallum, Plate 9. fig. 10. Nematocysts occur in this last-mentioned layer. They 
are extremely small, measuring only ‘009 millim. in their longest diameter. They are 
of an ovoid form, and contain a single filament within wound in a spiral whose axis 
corresponds to the long axis of the cell. They are often to be seen with the thread 
emitted and twisted in a loop against the side of the cell, which frequently assumes 
after the ejection of the thread a reniform outline, Plate 9. figs. 13, b, b'. They are so 
small that they might readily be overlooked, and a very high power is required to 
determine their structure. They appear to be not very abundant. They are seen 
in situ , Plate 9. fig. 10, N. 
(2) Imbedded within the superficial homogeneous layer of the mesoderm occur also 
fusiform and branched connective-tissue cells, which are associated together in elongate, 
often nearly linear groups, Plate 9. fig. 10. Many of these cells are branched, throwing 
off fine filamentous processes in various directions. Layers of similar cells lie every- 
where next opposed to the hard tissues of the living corallum, as has already been 
described. These cells do not compose any portion of the polyps themselves, but 
merely line the calcareous calicles. 
(3) In decalcified preparations of Heliopora enclosed within the layers of connective- 
tissue cells, at the places before occupied by the growing points of the corallum, occur 
the masses of very finely fibrillar calciferous tissue already described, Plate 9. fig. 10, P. 
Both this and the corallum itself belong to the mesoderm. 
The entoderm consists of spherical cells, each with small transparent nucleus and 
contents, consisting of irregular yellow pigmented masses and dark coarse granules. 
They have a mean diameter of about '014 millim., but vary much in size. They are 
most probably ciliated in the fresh condition, as are the closely similar entodermic cells 
of other Alcyonarians. I have not been able to see cilia in the hardened specimen 
which I have examined; nor have I in these specimens been able to detect differences 
between the entodermic cells lining the cavities of the calicles and tubes and those 
lining the canals. Some of the cells show a division of their contents into four (Plate 9. 
fig. 13, a, a!). The entodermic cells form layers lining the canals, the ccenenchymal 
tube-cavities, the cavities of the calicles, and interseptal spaces. 
The ccenenchymal tubes in their upper cavities are thus lined throughout by a 
membrane consisting of three layers, viz. an outer layer of connective-tissue cells, a 
middle layer of homogeneous connective-tissue, and an inner lining layer of entodermic 
cells. The calicles are lined throughout in like manner. The arrangement will be 
seen in Plate 8. fig. 4. In the membrane lining the calicles, in transverse sections a 
peculiar structure (shown Plate 8. fig. 3) is to be constantly observed. Stout offsets 
from the median connective-tissue layer pierce the outer layer of connective-tissue 
cells, and hang loose externally as flattened tags, which appear as if broken off, and are 
