CALYCOSILVA CANTHARELLUS. 
73 
tudinal rhabds. On reaching the body proper of the sponge this hollow sheaf 
of rhabds opens out. in a calyculate manner and divides into numerous rhabd- 
bundles (Plate 5, figs, le, 4e, 16), which extend in the floor of the subdermal 
cavities paratangentially and more or less radially towards the margin of the 
plate-like sponge-body. Occasionally anastomosing they here form a kind 
of loose paratangential network with radially elongated meshes. 
On the gastral side, in the floor of the subgastral cavity, a similar network 
of preponderantly radially extending rhabd-bundles (Plate 5, figs, lc, 4c) is 
observed. 
Besides these paratangential rhabd-bundles in the floors of the subdermal 
and subgastral cavities numerous isolated rhabds and loose bundles of them, 
situated obliquely or transversely (Plate 5, figs. Id, 4d), are found in the choano- 
some. The ends of many of the transverse rhabds adhere to proximal rays of 
hypodermal and hypogastral pentactines. In the centre of the sponge-plate, 
near its junction to the stalk, some oblique rhabds, similar to these but very 
much larger, have been observed (Plate 5, fig. 16). 
At the point of junction of the stalk to the body proper of the sponge some 
long and slender diact.ines with actines enclosing an angle of about 90° (ortho- 
monaenes) have been observed in C. c. var. helix. 
The hexact.ines lie scattered rather irregularly in the choanosome. The 
thickness of their rays and the size of their spines are subject to considerable 
variations. The shortest rayed and most strongly spined are found in the 
centre of the body at its junction with the stalk. Towards the margin of the 
sponge-plate the rays of the hexactines become more slender and less spiny. 
Tetract.ine and triactine hexactine-derivates have been found in small 
numbers, chiefly in C. c. var. megonychia. The diact.ine hexactine-derivates 
are not numerous, and have been observed only in C. c. var. simplex in the 
region of the junction of the stalk to the body proper of the sponge. 
The gastral and dermal surfaces of the body proper and the surface of the 
stalk are uniformly covered by a dense pinule-fur (Plate 2, figs, la, 8a, 13a; 
Plate 4, figs. 21-24; Plate 5, figs, la, g, 4a, g, 11a, g, 16a, g). The two kinds of 
pinules, with long, well-developed, and pointed proximal ray, and with short, 
rudimentary, rounded proximal ray, which are not, or hardly at all, connected 
by intermediate forms, are quite indiscriminately scattered, and although the 
former are relatively more numerous on the body and the latter predominate on 
the stalk, both kinds appear everywhere to be intermingled. ’Apart from the 
dermal pinules of the body being on the whole slightly larger and having slightly 
