456 MR. H. N. MOSELEY ON THE STRUCTURE OF THE STYLASTERIDH5. 
Z ooids. 
Dactylozooids. — The dactylozooids and their sacs in Allopora profunda are so 
closely similar in form and structure to those of Stylaster densicaidis, that they need 
no further description. 
Gastrozooids. — The sacs of the gastrozooids in the present species differ from those 
in Stylaster densicaidis in being of smaller diameter in proportion to the dimensions of 
the pore cavities, and in being held in place by means of the radial offsets already 
described. It is possible that the wall of the sac of the gastrozooid lies nearer to the 
wall of the gastropore in the recent condition of the coral than is represented to be 
the case in Plate 39, G Z, and in Plate 44, fig. 12; but all the spirit specimens 
examined yielded a similar result when decalcified. The sac of the gastrozooid is, as 
usual, a reflection of the surface layer of the ectoderm. In the contracted condition it 
forms a long tubular cavity, somewhat narrowed in the region just above the gastro- 
zooid and at the mouth, and dilated towards the centre. A t its mouth, the marginal 
fold of the sac rises in the form of a flattened dome, somewhat above the level at 
which the openings of the sacs of the dactylozooids commence. 
The gastrozooids are very deeply seated at the bottoms of their sacs. They are 
dome-like in form, with expanded bases. A whorl of tentacles, set on at some distance 
from the summit of the dome, marks the commencement of the large rounded hypostome. 
The tentacles are twelve in number, and are set on in a single whorl. They are 
elongate-ovoid in form. From the base of the zooid a series of radially disposed large 
canals pass outwards to be distributed, as in Stylaster densicaidis, a certain number of 
their branches forming a tortuous mesh work, offsets from which pass to join those of 
the gastrozooid of the adjacent system. 
The structure of the zooid clyco-sy stems is clearly displayed in Plate 44, fig. 12, 
which is, in some respects, somewhat diagrammatic, but is taken from an actual 
transverse section. The section is taken above the level of the gastrozooid, which 
hence does not appear. The sac of the gastrozooid is, however, seen in section, 
together with its radial supports. The dactylozooids seen in section show the three 
layers of tissue of which they are composed, viz., ectoderm, basement membrane and 
muscular layer, and endoderm ; and sections of their styles are introduced to show the 
position of these. The two finer reticulations of the coenosarcal meshwork, inner and 
outer, are also well seen, with the larger canals in the interval between them, which at 
this height- in the wall of the system are confined to the interspaces between the 
dactylozooids. 
Gonophores. — Male examples only were obtained of the present species. The 
ampullae are covered by the surface layer of the ectoderm, and the superficial reticula- 
tions of the coenosarcal meshwork. Within, they contain a sac (Plate 39, G) in which 
are developed two or three gonophores of an ovoid form, which are attached to offsets 
of the coenosarcal canals, and which show the usual elements characteristic of the 
various stages in the development of spermatozoa in the family, which elements are 
