360 



REVISIOI'I OF THE MONAXONID SPONGES, 11., 



ed by Lendenfeld, in the fact that its margin is not prolonged 

 upward into a tube, but is level with the surrounding surface. 

 The oscular canals are arranged in a manner conforming with 

 the general symmetry (Pl.xx., fig.4) : a few run upwards 

 axially from the stalk, separated from one another only by 

 thin partitions, while the remainder — which start from differ- 

 ent points quite close beneath the surface — traverse the sponge 

 radiately, in such manner as to come into parallelism with the 

 axial direction before the oscula are reached. 

 Other canals also occur, each of which is 

 continuous with the lumen of a fistula. 



As far as can be judged from the incom- 

 plete specimens of the typical form of the 

 species, the arrangement of its canals is much 

 the same as in the variety. (The probability 

 is that the canals, which connect with the 

 fistulfe, are inhalant in function). 



The structure of the skeleton also is very 

 similar in both forms, except that, in the 

 root-like processes of the type, the main 

 skeleton consists almost entirely of stout 

 longitudinal fibres (50 to 200 /x in diameter) 

 closely arranged like the strands of a rope; 

 while, in the peduncle of the variety, the 

 corresponding fibres are much more widely 

 separated, and the intervening spaces are oc- 

 cupied by a renieroid, for the most part uni- 

 spicular, reticulation, similar to that which 

 is general throughout the body of the sponge. 

 Phlceodictyon ramsayi. rphe fibres of the roots or peduncle, as the 

 case may be, continue into the body of the 

 sponge and spread dendritically through it, at a considerable 

 average distance apart ; here and there, they are connected by 

 cross-fibres. Between the fibres, as already indicated, the 

 skeleton consists of a renieroid reticulation. The fibres are 

 composed of very closely packed, parallel spicules, which, 

 apparently, are held together by a minute quantity of spongin. 



Fig. 



