MR. H. N. MOSELEY OR THE STRUCTURE OF THE STYLASTERIDiE. 
445 
the coral which is living supported by dead corallum below, but the deeper canals ol 
the coenosarc retain their vitality even to the very axes of the branches. The general 
arrangement of the coenosarcal canals is seen in Plate 37. Closer mesliworks compose 
the mass near the surface, and in deeper regions the canals are larger and form wider 
and longer meshes, and constitute an axial system of main canals by which the various 
distant zooids are brought into relation with one another. Around the sacs of the 
gastrozooids an irregular radial arrangement of the canals immediately adjoining the 
sacs is to be observed, representing the more regular radial disposition described as 
existing in Sporadopora dichotoma. 
The histological structure of the coenosarcal canals is closely similar to that occurring 
in those of Sporadopora. The endodermal pigmented cells are of a light brick red 
colour, and hence the entire coral in the recent state is thus coloured. The pigment 
is, however, soluble in alcohol, and thus quickly extracted in specimens preserved 
in that fluid, but it is insoluble in glycerine. A continuous superficial layer is present 
on the surface of the coral, as shown in Plate 37, and it is composed of polygonal 
nucleated cells (Plate 11, fig. 10). 
Errina is the only genus of Stylasteridm in which the definite cellular structure of 
the surface layer of the ectoderm could be determined, although no doubt a similar 
structure exists in that of all the species of the family. 
In places, the cells composing the layer appear to overlap and sometimes to form 
a double layer, as seen in the figure. Possibly this appearance is due to the action of 
reagents. 
Nematocysts of two kinds, larger, and smaller occur, and of the usual forms. The 
larger are mostly gathered into thickly set masses or nematophores (Plate 37, N N), 
but occur also scattered, or in twos or threes, within the surface layer (Plate 44, 
fig. 10, N). These scattered nematocysts have the appearance of lying within the 
polygonal cells composing the surface layer (Plate It, fig. 10), as is the case in 
Hydra viridis, as shown by F. E. Schultze.* 
The smaller nematocysts occur scattered in the surface layer (Plate 44, fig. 10, N), 
and thickly set in the tentacles of the gastrozooids and outer surfaces of the clactyio- 
zooids. 
Zooids. 
Dactylozooids. — These are simple elongate mouthless conical bodies closely similar 
to those of Sporadopora but somewhat more attenuated in appearance (Plate 37, D Z). 
They are attached to the bases of sacs which line the cavities of the nariform dactylo- 
pores of the corallum, the walls of which sacs are continuous in structure with the 
surface layer of ectoderm. 
Gastrozooids. — These are cylindrical in form (Plate 37, G Z), with a rounded conical 
hypostome and four tentacles set in a single whorl at its base. The tentacles are in 
* “liber den Ban und die Entwicklung von Gordi/lophora lacustris.” Leipzic : W. Engelman, 1871. 
Taf 6, fig. 10, s. tv. 
