HYALONEMA (OONEMA) BIANCHORATUM PINULINA. 
311 
The polyps lie in excavations of the sponge-body just large enough for them. 
Their distal ends are flush with the surface of the sponge. In life, when 
expanded, they probably protruded more or less beyoryl its surface. These 
polyps form groups within which they are about 4.5 mm. apart (Plate 83 , fig. 
60). The coenenchym-like mantle enclosing the upper end of the stalk, which 
has been referred to above, may have formed part of a colony of polyps similar 
to those in the body of the sponge. Some of the polyps in the sponge-body which 
I examined bore a short thread-like protuberance on their lower (inner) end. 
Probably all the polyps of a group, possibly all the polyps of the whole sponge, 
are connected by such threads. I did not make sure of this, however, because 
for this purpose it would have been necessary to cut up the fine and unique 
specimen. 
The pinules (Plate 82 , figs. 21-34; Plate 83 , fig. 45b). The dermal pinules 
of the upper and middle-parts of the body in both specimens resemble, as radial 
sections show, the gastral pinules, but differ from the dermal pinules on the 
basal part of the sponge, the latter being larger and having distal rays with more 
divergent spines. In the spicule-preparations of different parts of the surface 
besides the pinules shown by the sections to be truly proper to the region in 
question, I always found a few others; in the spicule-preparations of the gastral 
membrane and the upper and middle-parts of the dermal membrane were typi- 
cally basal spicules; and in the spicule-preparations of the basal part of the 
dermal membrane were pinules of the type found in situ on the upper parts 
of the sponge. 
The principal dimensions of the pinules are tabulated on p. 312. 
The gastral pinules (Plate 82 , figs. 29, 30; Plate 83 , fig. 45b) and the dermal 
pinules on the upper and middle-parts of the spo?ige (Plate 82 , figs. 22, 31-33) are 
nearly always pentactine, very rarely hexactine. Their distal ray is straight 
and 120-280 n 1 long. It ends with a terminal cone free from spines. Its proxi- 
mal part is also spineless, and it arises with a trumpet-shaped extension from the 
cross formed by the lateral rays. Farther up the distal ray becomes thinner, 
and it attains its minimum thickness at a distance of about 30 n from its base 
(the centrum of the spicule). Beyond that it again becomes thicker. At its 
thinnest point the smooth proximal part of the distal ray is 7-11 n thick. The 
basal thickening is variable. The distal ray of a typical upper dermal pinule is 
17 jj. in diameter at its thickened base, 30 n higher up, and 11/^ at its thinnest 
point. The whole of the distal ray, with the exception of its proximal and distal 
1 This and the following measurements refer to the pinules of both specimens together. 
