REPORT ON CORALS — HYDROCORALLIN^E. 63 



general plane of the flabellum. This tendency is, however, to a large extent obscured 

 by irregularities. One face of the nabellum, viz., that rendered convex by the curving 

 of the whole mass, is entirely devoid of cyclo-systems ; whilst a considerable number are 

 scattered over the surface of the branches on the concave face. As the branches thicken 

 by growth of coenenchym, the cylindrical masses of the cyclo-systems become buried, and 

 only their free ends remain in view as the mouths of pore systems on the surfaces 

 of the branches. Even these mouths become partially overgrown in the active 

 regions of the coral, and in the older parts of the stem frequently obliterated. The 

 cyclo-systems consist of a deep gastropore, provided with a style, and surrounded by 

 from twelve to sixteen dactylopores. The dactylopores are provided with a small hirsute 

 style, as in Stylaster densicaulis. 



A diagrammatic view of a cyclo-system, as seen from above the mouths of the 

 pores, is given in Plate II. fig. 13. The styles are supposed to be brought into view by 

 deep focussing of the lens. The form and arrangement of the pores are almost exactly 

 similar to that already described as occurring in Stylaster. 



The very small ampulla3 are spherical cavities, which are usually entirely sunk 

 beneath the surface, but sometimes near enough to it in situation to raise upon it very 

 small conical elevations, which easily escape notice, and are present only here and 

 there. The ampullae are present in abundance in the walls of the pore systems and at 

 their bases. 



Soft structure of AUopora profunda (PL VI.). 



Ccenosarc. — A surface layer of ectoderm covers the surface of the coral, as in Stylaster 

 densicaidis, and is reflected into the pores to form the sacs of the zooids. The 

 ccenosarcal canals form a fine superficial reticulation at the surface of the coral, beneath 

 the surface layer, and spring from a deeper meshwork of larger canals which, as in the 

 Stylaster already described, have a mainly longitudinal course within the thickness of 

 the walls of the pore systems, parallel to the axes of the systems, and lead, almost 

 directly from the bases of the dactylozooids with which they anastomose to the large 

 canal offsets given off at the periphery of the bases of the gastrozooids. At the inner 

 surface of the gastropore are finer canals springing from this main meshwork, and from 

 these spring a series of offsets which pass in a direction radial to the axis of the gas- 

 tropore, to abut on and become united with the outer surface of the sac of the 

 gastrozooid. 



The radial offsets are disposed irregularly, at unequal distances from one another, and 

 at all heights in the gastropore (PI. VI. ER). The inner ends of the radial offsets are 

 often enlarged where they abut on the wall of the sac of the gastrozooid, and they are 

 often forked at their outer extremities, where they spring from the ccenosarcal meshwork. 



