THE SPONGES. 37 



mostly 3-5 mm. apart; more closely crowded in the upper part of the 

 sponge, where the interval is 2 mm. to 0.75 mm. On both dermal and 

 gastral surfaces, the small apertures of the numerou ' canals, 0.5 mm. and 

 less in diameter, give the sponge a porous appearance. 



The gastral surface is smootli, and the dermal surface, which is without 

 prostalia, exhibits no elevations, except that as in other species of the 

 genus the coarse skeletal bundles project. These latter bundles pursue 

 a nearly longitudinal or somewhat oblique course, converging toward the 

 lower end of the fragment, where there are some cases of anchylosis. 

 Elsewhere there is no, or only the feeblest anchylosis. The obliquely 

 transverse bundles on the gastral surface are not large enough to cause 

 elevations of the gastral membrane. In the uppermost part of the body 

 the transverse arrangement of these bundles is more marked than 

 elsewhere. 



The spiculation agrees with that of R. phoenix as described by Schulze 

 (1887, p. 84; 1895, p. 34; 1899, p. 20) and Ijima (1901, p. 265), except 

 in a few details. And the close resemblance to R. phoenix possibly indi- 

 cates that the specimen represents a late stage in the development of that 

 species. 



The principal diacts, smooth and tapering to a point at each end, bent 

 at the middle or more evenly curved in bow-like shape, reach a diameter 

 of 300 ju, and a length of 30 mm. There are abundant smaller sizes down 

 to 12 mm. x 170 /x, below which still smaller spicules with the character- 

 istic shape down to 6.5 mm. x 90 /x are found. 



The slender cylindrical comital diacts of various lengths are mostly 

 6-8 /x thick. They are swollen in the middle, and usually with subtermi- 

 nally roughened ends, which are often but not always enlarged. Similar 

 diacts, 6-30 /x thick, constitute the smaller bundles or lie loose in the par- 

 enchyma. Other small parenchymalia, intermediate between the diact 

 and hexact condition, with cylindrical rays rounded at the ends, are also 

 found. The tauact and stauract forms are the commonest. 



The comital diacts are not cemented together over the principalia, and 

 the latter are only loosely combined to form bundles. Many of the prin- 

 cipal diacts lie scattered through the parenchyma, unassociated in bundles. 

 Some of these are without comitalia, although in general so provided. To 

 form a long bundle the ends of succeeding diacts overlap, and become 

 covered with a continuous sheath of comitalia. Very commonly 4 or 5 



