70 CALYCOSILVA CANTHARELLUS. 



distally by the superficial membrane containing the paratangential pinule-rays, 

 proximally by another perforated membrane or, to speak more correctly, a net- 

 work of paratangential trabeculae, containing the paratangential rays of the 

 (hypodermal and hypogastral) pentactines. The subdermal (Plate 5, figs. 1, 4f) 

 and subgastral (Plate 5, figs. 1, 4b) cavities extend below this membrane or 

 network. These are identical in shape, 300-600 ^i high (radial dimensions), and 

 traversed by radial columns connecting their roof with their floor. Each of these 

 columns consists of a proximal ray of a (hypodermal or hypogastral) pentactine, 

 enveloped in a mantle of soft tissue. In the formation of many of them also the 

 distal end of a transverse choanosomal rhabd takes part. The columns are on 

 an average 250 fx apart, and usually 30-40 n thick. Numerous fine, thread-like 

 trabeculae arise from the columns and join to form close reticulations which sur- 

 round them like trellis-work. Above and below these reticulations are very 

 extensive, and join to form continuous networks extending along the roof and 

 floor of the cavity. In the middle they appear to be less extensive. In the sec- 

 tions large empty spaces are observed between the trellis of trabeculae surround- 

 ing the columns in this region. I think it quite likely that in life these cavities 

 are also traversed by trabeculae, and am inclined to ascribe their emptiness in 

 the sections (Plate 5, figs. 1, 4) to the trabeculae having here been torn and lost 

 through shrinkage when the sponge was captured and preserved. 



The floor of the subdermal and subgastral cavities is traversed by bundles 

 of rhabds (Plate 5, figs. 1, 4c, f) and perforated by numerous apertures. These 

 are more or less circular, both on the dermal and the gastral side, and in the best 

 preserved specimens (parts) are sometimes 1.5 mm. wide. In specimens (parts) 

 not so well-preserved and more strongly shrunken some of them attain a diameter 

 of 3 mm. (Plate 4, fig. 20). On the gastral side their distance from each other 

 nearly equals their diameter, on the dermal side they are farther apart. The 

 apertures on the lower, dermal side lead into the afferent, those on the upper, 

 gastral side into the efTerent canals. The afferent and effei'ent canals are, in 

 well-preserved parts of the plate-like body proper of the sponge, 0.75-1.5 mm. 

 wide, and extend in a direction more or less vertical to the surface (Plate 5, figs. 

 1, 4, 16). Their length is on the whole proportional to their width. The widest 

 reach to within a short distance of the floor of the (subdermal or subgastral) 

 cavities on the opposite side. The stalk is hollow, with an eccentric, not axial 

 cavity, and walls, which in the middle of the stalk of the specimen of C. c. var. 

 helix are 2.5 mm. thick on one side and 0.7 mm. on the other. Vertical, appar- 

 ently efferent canals of considerable width (Plate 5, fig. 16) leading up to the 



