19 



it gradually passes into the lateral surface of the conical sponge. This terminal 

 face is covered by a tough skin and has irregular depressions which give it a 

 somewhat folded appearance. A slight prominence, situated excentrically, cor- 

 responding to the upper end of the spicule- bundle of the peduncle arises from it. 

 The o-reater part of the square-meshed skeleton-net of the dermal membrane has 

 been lost ; only in a few places it is still clearly distinguishable. The gastral 

 membrane covering the terminal face of the sponge is well preserved but strongly 

 compressed. It appears velvet-like. It is to be noted that large and conspi- 

 cuous, curved or abruptly-bent oxydiactines, 6-15 mm. long, over .500/^ thick and 

 extending longitudinally, are exposed to view in those parts of the external 

 surface where the dermal layer has been lost (pi. XVII, f. 3). Closer investiga- 

 tion shows that these large and strong curved spicules are pretty abundant in the 

 parencbyme generally, and particularly just below the dermal membrane. 



The most important macrosclere parencliymalia are the oxydiactines. These 

 are mostly aggregated in bundles, more rarely isolated, and very abundant through- 

 out the interior. They are slender, straight or slightly curved, and 300-400 ^ 

 long, rarely longer. As in other Hyalonema species they are either quite smooth, 

 that 'is destitute of a central inflation, or they have a thickening or two or four 

 well defined protuberances in the middle. 



Between these spicules sparsely scattered, smooth oxyhexactines of various 

 size, 500-800 /^ in diameter, are met with. Stout and smooth oxypentactines of 

 similar size also occur. These appear as regularly arranged hypodermalia, lying 

 below the outer surface and supporting the dermal membrane. Under the 

 gastral membrane there are no such spicules. 



In the central part of the body, particularly in the vicinity of the upper end 

 of the spicule-bundle forming the peduncle, which is imbedded in the body 

 of the sponge, not infrequently smooth amphityles or tylostyles occur. ^ These 

 resemble in length and in general character the ordinary oxydiactines, the inflated 

 ends of which vary in shape but are never sharply defined. 



Of the microsclere parenchymalia I shall first describe the oxyhexactines. 

 These occur in different regions of the sponge in varying numbers. They mea- 

 sure 120-140 /^ in diameter and their rays are fairly stout, nearly smooth, sharp- 

 pointed and terminally shghtly curved or angularly bent. In the walls of the 

 subdermal cavities and some of the incurrent canals those spicules are very 

 numerous, and form, like true canalaria, a continuous layer. They also appear to 

 occur scattered, but less frequently, in the parenchyme. Here they may possibly 

 occupy the walls of the smaller canals. 



Oxypentactine dermal pinules cover the strands of the external network in 

 <rreat numbers. Their four basal rays, which form a rectangular cross, are of 

 medium thickness, 40 Mong, terminally pointed and finely granular. The free 



