68 



My material consists of the caliculate, basal part represented in fig. 10 on 

 plate XXII, which is attached to a piece of coral by a tough basal plate ; and of 

 some loosely joined fragments of the tubular, lateral wall of the sponge-body. 



In the wall of the slightly laterally compressed basal calyx some irregu- 

 larly distributed, circular' or oval apertures with smooth margins, about 1 mm. 

 wide, are met with. The uniformly convex outer side of the calyx is covered 

 with a dermal membrane through which an irregular network of stout skeletal 

 strands is visible. On the inner surface one sees a slightly raised reticulation 

 corresponding to this network, with pit-like depressions of varying breadth in 

 the meshes. Some of these pits lead down to the parietal apertures mentioned 

 above. 



The basal plate is as hard as stone and also laterally slightly compressed. 

 In it the same well-known, dense skeletal reticulation as in the basal part of all 

 other sessile EuplectellidsR is met with. The stout spicules composing it, which 

 are wholly glued together by silica or joined by synapticula only, can be distinctly 

 made out in this network. 



The supporting skeleton-net of the body-wall, which grows up from this 

 dense basal reticulation, is loose and has pretty large meshes. It is chiefly 

 composed of stout and smooth, usually curved or angularly bent oxydiactines 

 l'5-2 cm. long and 100-200 ^ thick. These thick principalia are accompanied 

 and closely surrounded by numerous slender diactines of the same length. The 

 spicular fibi'es thus composed are joined, either by simply overlying one another 

 or by the formation of numerous synapticula, to form a network with strongly 

 elongated meshes. The firmness of the junction of the fibres increases towards 

 the base of the sponge. It is greatest in the rigid basal plate. 



Between the slender, fibrous diactines, hexactines with short, smooth rays 

 of similar thickness are found pretty frequently. More rarely triactines and 

 pentactines are met with. All these spicules are, in the lower part of the sponge, 

 glued together by secondarily apposed masses of silica. 



Oxyhexactines, two opposite rays of which are usually vertical to the surface, 

 are met with everywhere in the parenchyme. Their rays are slender^ about 

 150 /" long, basally smooth and usually rough or covered with small tuoercles in 

 their distal thirds. More rarely the rays are rough, tuberculous or even covered 

 with spines in their entire length. 



Scattered throughout the choanosome great numbers of those remarkable 

 oxystauraster microsclere pai'enchymalia are met with, which have been described 

 by Ijima in Regadrella oJclnoseana. These spicules consist of four main-rays 

 each of which bears four (more rarely 5 or 6) terminal branch-rays. The four 

 main-rays are equal, lie in a plane, and together form a rectangular cross ; they 

 are 3 H- thick and about 10 ^ long, smooth, basally cylindrical and terminally 



