EEPORT ON THE TETRACTINELLIDA. 
Ixxxv 
hispidation may result, the hispidating spicules may or may not differ from those which 
are confined to the interior of the sponge, the latter will be spoken of as “ somal ” 
spicules when they are common to the whole sponge body, the former may be 
distinguished as hispidating spicules, a term commonly employed by Carter. 
Over special areas the hispidation may become more pronounced, and to these areas 
it may be restricted ; thus arise rooting spicules and fibres, basal fringes, fringes of the 
oscular margin, of the vestibules, and so forth. 
Radical Spicules. — The sponge may be seated immediately on the surface of the sea- 
floor, and the rooting (radical) spicules descend directly into the underlying ooze, either 
separately or as continuations of the somal spicular fibres ; they terminate either freely 
and separately (Fig. XIII., a), or in a densely tangled and matted accumulation, which 
serves as a basis of support and in size rivals the sponge itself (Fig. XIII., h). 
On the other hand the sponge may be supported some distance above the ooze by 
the radical fibres which form slender pillars supporting the sponge above, and below 
Pig. XIII. — Modes of attachment of Sponges to the sea-bottom, a, Tetilla euplocamus, rooted by a mesh of spicules in the 
ooze ; 6, Cinachyra harhata, seated on a basal mass of tangled spicules ; c, Thenea wymllii, supported by stems of 
radical spicules terminating in a basal mass lilie that of h; d, Tetilla casula, supported by a parachute-like arrangement 
of radical spicules. 
terminating as in the last-mentioned instance by splaying out and matting together into 
an almost solid tangle (Fig. XIII., c) [Thenea ivyvilli, p. 74). 
In one instance [Tetilla casula, Carter) the margin of the flat base of a hemispherical 
sponge is produced into a dense rigid fringe of radical spicules which extend outwards 
and downwards, giving a parachute-like form and support to the sponge (Fig. XIII., d). 
Cloacal Spicules. — The oscular margin is frequently produced into a thin tube, the 
walls of which are traversed longitudinally by spicules arranged palisade fashion in a 
spicule fringe or tube [Tetilla, Cinachyra, Thenea). In two species among the 
Stellettidse the oscular margin is produced into a remarkable cloacal tube provided 
with a special skeleton, an account of which will be found under the description of 
Trihrachium schmidtii (p. 154), and Disyringa dissimilis (p. 161). In some of the 
Stellettidse [Pilochrota), minute oxeas occur fringing the oscular margin in the same 
