1/6 



ISAO IJIMA. 



are well in evidence, though not in numerical predominance over the pcn- 

 tactins. In other words, the dcrmalia arc generally mostly pentactine. Ir- 

 respective of their being pentactine or hexactine,the dcrmalia measure in the 

 length of tangential rays from about So/i up to 120//, l$oji, 175/i, 230^ or 

 even 290^ in different individuals, the proximal ray being about as long as, 

 or either somewhat longer or shorter than, the tangentials of the same 

 spicule. In a single case (Sc. Coll. sp. No. 279) of Sagami Sea specimens, 

 certain large pentactine dermalia, amongst others of much smaller dimen- 

 sions, were found to possess exceptionally long proximal ray, which, mea- 

 suring fully 600/2 in length, extended nearly right through the entire thick- 

 ness of the sponge wall. 



In pentactine dermalia there usually exists a low swelling or a knot in 

 place of the atrophied distal ray. In some other dermalia the knob is pro- 

 longed to a short stumpy peg, and in still others this may be slightly swol- 

 len towards the outer end and may here bear a few short spiny processes. 

 The last condition leads over to those cases of hexactine dermalia in 

 which the distal ray has, so to say, fairly started on the way of as- 

 suming, but has not yet quite reached, a plumose state of develop- 

 ment, and on that account may well be designated subpiumose. 

 In some of the specimens the subpiumose distal ray never ex- 

 ceeds So/u or even half that in length, thus presenting quite a stunted 

 appearance. In still other specimens the same ray is found to reach a 

 length of 130^, 150/* or even 1S5/Z ; in these cases the shaft slightly thickens 

 distally, remains smooth or only sparsely tubercled in the proximal half of 

 its length, and then commences to bear short, obliquely distally directed 

 spines, which more distally grow somewhat longer but are neither so long 

 nor numerous as to give to the parts a decidedly feather-like appearance. 

 The above subpiumose or imperfectly feather-like state of the distal rays 

 represents about the highest limit of development reached by hexactine 

 dermalia or pinules in the great majority of the specimens. An exception 

 to the rule was found in the single case of a specimen from Közushima (Sc. 

 Coll. Sp. No. 552), in which some, but by no means all, of the hexactine 



