476 " THETIS " SCIENTIFIC RESULTS. 



and terminate at the surface in a complex network. The main 

 fibres are composed of loosely arranged spicules — about 8 or 12 in 

 a row — and are held together by a small amount of horny matter; 

 they are about 0'05 mm. in diameter and 0-25 to 0-3 or more 

 apart. The secondaries have three or four spicules in a row, and 

 the connecting fibres are mostly unispicular. 



The mesh is square or oblong ; near the surface it becomes 

 somewhat irregular, and the mesh is regulated by the length of 

 the spicules. The latter consist of oxea of two sizes, 0'14 by 

 0-013 mm., 0-11 by GOOimra. Slightly cur\ed bidentate chelse 

 are present in moderate quantities; size 001 6 mm. 



DESMACIDON HISPIDOSA, sp. nov. 



(Plate xliv., fig. 17.) 



Station 44. 



Sponge with a well developed attachment base ; the main axis 

 is 140 mm. high and gives off three or four lateral branches, some 

 of which are coalescent ; all are more or less compressed in the 

 plane of branching, except at the tips, and measure about 5 or 

 10 mm. in their greater and from 3 to 7 mm. in their lesser 

 diameter. The primaries give rise to a series of secondary 

 branchlets which are in various stages of development. General 

 surface — where the ectoderm is intact — porous and minutely 

 conulose, elsewhere with a strongly hispid aspect and a rather 

 loose or open network of stoutish fibres. Texture firm, tough 

 and scarcely compressible. Colour greyish-Vjrown. 



Skeleton consisting of a series of somewhat stoutish primary 

 fibres, which are centrally plexoid, and give off at irregular 

 intervals many secondaries, and as the surface is approached 

 they terminate in subradiating tufts of fine fibres in theectosome 

 and form some of the minute conuli as well as giving the denuded 

 surface its hispid appearance ; the connecting fibres are very 

 slender, numerous, and render the description of the network or 

 mesh difficult ; disregarding the finer fibres, the mesh may be 

 described as rhomboidal, oblong, or elongate, each space being 

 occupied by a miniature spider-like web of slender fibres. 



Megascleres : — straight or slightly curved oxea, cylindrical to 

 within about three or four diameters of the acute points ; these 

 spicules are densely packed in the main fibres ; in the secondaries 

 they are biserial, and in the finer fibres mostly uniserial or absent. 

 Size from 0-18 to 0-2 mm. by 0008 mm. to O-Ol mm. 

 ^Microscleres : — sigmata very variable in size and shape, ranging 

 from 0-015 to 0-12 mm. in length ; they are abundant throughout 

 the sponge. Chelse have not been observed. 



