HYALONEMA (OONEMA) CRASSIPINULUM. 333 



which are the dermal, are continuous and fairly smooth. The upper surface, 

 which is the gastral, now appears rugose. In life wide cavities, separated by 

 upright walls, probably occupied the upper part of the interior. Reticulate 

 pore-sieves are observed on some parts of the surface. Indications of flagel- 

 late chambers about 140 n in diameter were noticed in some of the sections. 



The colour in spirit is Hght dirty brown. 



A small colony of Palythoa polyps is attached to the upper part of the 

 stalk. 



The skeleton. A fur composed of distal rays of large pinules covers the 

 whole sponge. The gastral pinules, particularly those on the pore-sieves, are 

 very large, the dermal considerably smaller. Very numerous large micramphi- 

 discs lie in and on the surface. Microhexactines, paratangentially extending 

 amphioxes, and the lateral rays of pentactines occur just below the lateral rays 

 of the superficial pinules. Some hexactine and abundant rhabd megascleres, 

 very numerous microhexactines, a few monactine microhexactine-derivates, 

 canalar pinules, and amphidiscs are found in the interior. The internal amphi- 

 discs are of four kinds: — 1, very scarce large macramphidiscs; 2, not numer- 

 ous small broad-anchored macramphidiscs; 3, very scarce small macramphi- 

 discs; and 4, very numerous micramphidiscs. It is possible, but not probable, 

 that 1 and 3 are foreign spicules. Numerous acanthophores for the most part 

 diactine and tetractine occur in the basal part of the sponge-body. The canalar 

 pinules are rare, and found only here and there in the canal-walls. In the walls 

 of some of the canals masses of micramphidiscs are observed. The remnant 

 of the stalk consists of a few stout and several slender spicules. 



In the superficial part of the coenenchym and in the lateral and oral walls 

 of the individual polyps of the Palythoa, spicules occur in large numbers; these 

 are similar to the smaller and stouter acanthophores of the basal part of the 

 sponge. 



The gastral superficial pinules have a distal ray 250-1130 ix long (measured 

 in the case of the curved ones along their chord). The length frequency-curve 

 of the distal ray has two distinct elevations, at about 600 and 8.50 p. This 

 indicates that two kinds of gastral pinules, a large and a small, should l)e dis- 

 tinguished. 



The large gastral pinules (Plate 92, figs. 1-4, 20, 22, 23), which greatly 

 preponderate in the reticulate pore-sieves, are all pentactine. Their distal ray 

 is straight or, comparatively very frequently, curved in its distal part. The 

 curvature is usually not great but sometimes very marked. In one of these 



