REPORT ON CORALS—HYDROCORALLINE. dS 
Errina is the only genus of Stylasteridze 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 (PI. IV. NN), but 
occur also scattered, or in twos or threes, within the surface layer (Pl. XI. fig. 10, N). 
These scattered nematocysts have the appearance of lying within the polygonal cells com- 
posing the surface layer (Pl. XI. fig. 10), as is the case in Hydra viridis, as shown by 
F. E. Schulze.’ 
The smaller nematocysts occur scattered in the surface layer (Pl. XLIV. fig. 10, N), 
and thickly set in the tentacles of the gastrozooids and outer surfaces of the dactylo- 
zooids, 
Dactylozooids.—These are simple elongate mouthless conical bodies, closely similar 
to those of Sporadopora, but somewhat more attenuated in appearance (Pl. XXXVII. 
DZ). They are attached to the bases of sacs which line the cavities of the nariform 
dactylopores of the ccenosare, the walls of which sacs are continuous in structure with the 
surface layer of ectoderm. 
Gastrozooids.—These are cylindrical in form (Pl. IV. G Z), with a rounded conical 
hypostome and four tentacles set in a single whorl at its base. The tentacles are, in the 
contracted condition, clavate in form. The base of the zooid rests on the style of the 
containing gastropore, which in the retracted condition of the zooid appears to project 
into the gastric cavity to a considerable distance as in Sporadopora. The ectodermal 
covering of the gastrozooids is composed of transparent ovoid cells (Pl. XI. fig. 4), 
which form a layer resting upon a substratum containing numerous nuclei and bounded 
by the basement membrane. The gastric endodermal lining of the zooids is composed of 
elongate cells of closely similar nature to those occurring in Sporadopora. The mouth 
appears, when closed, as a crucial slit ; four main canals usually lead from the base of the 
zooid cavity to the ccenosarcal meshwork. 
Growth by Budding.—Fresh zooids are added to the colony by means of buds arising 
from the surface layer of the ccenosare at points where this is joined by offsets of the 
superficial canals of the ccenosarcal* meshwork. Such a bud is represented in Plate 
IV. D. The part of the superficial layer immediately surrounding the bud is depressed, 
and forms the sac of the zooid. 
Gonophores.—Only female examples of Errina labiata was obtained for examination. 
1 Uber den Bau und die Entwicklung von Cordylophora lacustris, Leipzic, W. Engelman, 1871, Taf. vi. fig. 10. 
