38 THE VOYAGE OF H.M.S. CHALLENGER. 
Spheroidal cavities occur excavated in the ccenosteum at a very slight depth from the 
surface. These contain the gonophores in the recent state of the coral, and may be 
called ampulle. They are in this genus entirely buried beneath the surface, whereas in 
most genera of Stylasteride they project above it often to a very conspicuous extent. 
They communicate with the exterior when mature by means of small slit-like apertures 
placed at the bottoms of small irregularly shaped depressions which are to be seen with 
some difficulty scattered over the coral surface (PI. II. fig. 2, GG). Only male specimens 
of Sporadopora have been obtained as yet. No doubt, in the case of ampullz containing 
female gonophores, a comparatively wide opening in the surface of the ccenosteum is formed 
to allow of the escape of the fully formed planula. 
This actual tissue of the ccenosteum must be in Sporadopora and in most other 
Stylasteridee 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 ccenosteum 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 ccenostea are overgrown by a /lustra and other Bryozoa, and form bases of 
attachment to large masses of other Stylasteridee, such as Evrrina labiata. 
Since the caleareous meshwork is closer at the surface of the ccenosteum, its meshes 
must necessarily become enlarged by reabsorption as growth proceeds. Cavities also 
such as those of the ampullz must be filled up as the ccenosteum grows. The irregular 
cavities existing beneath the ampullz in some cases, as shown in Plate XXXV. 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 super- 
ficial and active ones. 
The tissue of the ccenosteum is very like that of Mi/lepora in histological structure, but 
appears somewhat more granular in texture, and less fibro-crystalline than it. 
Soft structures of Sporadopora dichotoma (P1. I1.). 
Cenosarc.—The tortuous canals and pores by which the ccenostea of all the Stylasteridee 
are traversed, are occupied in all the genera alike, in the living condition of the coral, by 
a series of meshworks of correspondingly branching, twisting, and anastomosing canals, 
which compose the coenosare or common body of the compound organism in each case. 
In Sporadopora only a comparatively thin layer on the surface of the coral is occupied 
by living soft structures. hese living structures are separated from the non-living 
deeper masses of the ccenosteum by the action of acids, and then appear as a sheet of soft 
