MR. H. N. MOSELEY ON THE STRUCTURE OF THE STYLASTERIDAE. 
431 
two or three such tabulae are present in a single gastropore, placed at successively 
deeper intervals. In some instances, two tabulae occur close together in a pore, one 
above the other. These tabulae are so excessively thin that I considered them at first 
to be membranous, but I have been unable to dissolve them by the use of very strong 
alkalis, and I am now convinced that they are calcareous. They do not seem to occur 
in all the gastropores, and I have not observed them in any instance in the dactylo- 
pores. The dactylopores vary much in size, as will be seen from the figures. 
Spheroidal cavities occur excavated in the corallum at a very slight depth from 
the surface. These contain the gonophores in the recent state of the coral, and 
may be called ampullae. They are in this genus entirely buried beneath the surface, 
whereas in most genera of Stylasteridae they project above it often to a very 
conspicuous extent. They communicate with the exterior when mature, by means of 
small slitdike apertures placed at the bottoms of small irregularly shaped depressions 
which are to be seen with some difficulty scattered over the coral surface (Plate 35, 
fig. 2, G G). Only male specimens of Sporadopora have been obtained as yet. No 
doubt, in the case of ampullae containing female gonophores, a comparatively wide 
opening in the surface of the corallum is formed to allow of the escape of the fully 
formed planula. 
The actual tissue of the corallum must be in Sporadopora and in most other 
Stylasteridae excessively dense and compact, since the masses formed by it, although, 
as described, excavated by canals in all directions, are heavy. 
In the older parts of the stems and their bases, the corallum appears to become 
compact and stony, and crystalline in fracture by obliteration of the canals and pores. 
In some specimens, portions of the surfaces of the stems which have once been dead 
have undergone rejuvenescence by the spreading of a thin layer of living coral over 
them from adjacent healthy regions. 
The dead coralla are overgrown by a Flustra and other Bryozoa, and form bases 
of attachment to large masses of other Stylasteridae, such as Errina labiata. 
Since the calcareous mesh work is closer at the surface of the corallum, its meshes 
must necessarily become enlarged by re-absorption as growth proceeds. Cavities also 
such as those of the ampullae must be filled up as the corallum grows. The irregular 
cavities existing beneath the ampullae in some cases, as shown in Plate 35, fig. 1, 
probably represent spaces occupied in an earlier condition of the coral by gonophores. 
Sometimes also old ampullar cavities remain unfilled up, situate beneath the more 
superficial and active ones. 
The tissue of the corallum is very like that of Millepora in histological structure, 
but appears somewhat more granular in texture, and less fibro-crystalline than it. 
Soft structures of Sporadopora dichotoma. (Plate 36.) 
Coenosarc . — The tortuous canals and pores by which the coralla of all the 
Stylasteridae are traversed, are occupied in all the genera alike in the living 
MDCCCLXXVIII. 3 Iv ? 
