72 
CALYCOSILVA CANTHARELLUS. 
helonychhexasters (in C. c. var. helix only) ; and plumicomes (exceedingly scarce 
in C. c. var. meg onychia). 
In the body proper of the sponge all the spicules are isolated and free. 
In the stalk the ordinary choanosomal rhabds are joined to form a dictyonal net- 
work to which also a few hexactines may be attached. 
In C. c. var. simplex (B) the skeleton-net of the stalk (Plate 5 , figs. 3b, 10) 
closely surrounds the hyalonematid root-tuft spicule (Plate 5 , figs. 3, 10a) 
which forms the base of attachment. The thinner distal end of this envelope, 
which corresponds to the lower end of the stalk, consists of a network with 
beams 12-35 n thick, and irregularly triangular or polygonal meshes, on an 
average about 100 n wide. In this network main longitudinal and secondary 
transverse beams cannot be distinguished. Farther on, towards the upper end 
of the stalk, the network becomes more regular and more and more distinctly 
composed of longitudinal main beams (15-65 n thick, usually 20-45 /*), joined 
by short, transverse connections to a ladder-like structure. In consequence 
of the main beams not being quite parallel, and the transverse beams very irregu- 
larly distributed, the meshes of this part of the network are very unequal in size, 
5-50 n and more broad, 30-200 n and more long. However different their 
size may be, in shape and position these meshes are very much alike, always 
elongated, oval, or rectangular with strongly rounded corners, and arranged with 
their long axis extending longitudinally. In some parts of this network the 
beams are smooth, in others covered by small, low, sharp spines. At the upper 
end of the stalk the transverse connections become less numerous and the net- 
work dissolves itself into a sheaf of longitudinal rhabds. 
Ends of the rhabds taking part in the formation of the net in many places 
freely protrude from it. These free rhabd-termini, which are rather scarce 
below, but become quite frequent above, are blunt-pointed or rounded, and 
just below the end, for a distance of 50-70 /*, densely covered with fairly large 
spines. In the blunt-pointed ones the end itself is free from spines. In the 
terminally rounded ones the spines cover the end also. The spined part below 
the end, particularly in the blunt-pointed forms, is considerably thickened, club- 
shaped, and measures 15-28 /j. in transverse diameter. 
The skeleton-net in the stalk of C. c. var. helix (Plate 5 , figs. 5, 7) is similar, 
but smooth and still more ladder-like. Its beams are 10-53 m, usually 20-40 n, 
the free ends of the rhabds taking part in its formation, 15-30 n thick. At the 
upper end of the stalk the transverse beams become scarcer and the character- 
istically tubular network dissolves itself into a hollow sheaf of isolated longi- 
