80 ART. 1. — I. IJIMA : HEXACTINELLTDA, III. 



distinguish every one of the genera in question from the Caulo- 

 phacidœ {cß\ above), while at the same time it seems to bring 

 them within the diagnostic scope allowable for the Rossellidie. 



F. E. Schulze ('gg, p. 101) looks upon the absence of a 

 pinidar distal ray to dermalia as the principal family- character of 

 the Hossellidre. Not that Kossellid dermalia should always lack 

 a distal ray, but he in fact includes, and quite rightly I believe, 

 the hexactinic form within the range of their legitimate variation, 

 with the restriction that the one necessarily distally directed ray 

 in such hexactins should not be pinularly developed but simple 

 and similar in appearance to the other rays. Thus, in Aphorme 

 horrida F. E. Sen.''' ('gg, p. 41), and in a manner also in 

 Trichasterina borealis F. E. Sch, ('oo b, p. 103), the dermalia 

 are said to be hexactins, while cases of other Rossellids with 

 well-developed hexactins occurring sporadically among the dermalia 

 are by no means rare (e. g., Rossella nuda Tops., R. racovitzce 

 Tops., Rhabdocalyptns tener F. E. Sch., Acanthascus platei F. 

 E. Sch.). I have expressly referred to the above point because 

 the dermalia of the Rossellidœ were originally considered to be 

 always without a distal ray (Chall. Rep., pp. 129, 374) in contrast 

 to those of the Asconematidre, — a fact which apparently has had 

 influence in maintaining the status quo of the latter group. 



* I must say that the small slender-rayed " oxy hexactins," taken by F. E. Schulze 

 for the dermalia of Apharme hmrkia, are probably not real hexactins but oxyhexasters of 

 hexactinose shape. I was strengthened in this belief on viewing under the microscope a 

 preparation of the type-specimen, kindly shown me by Professor F. E. Schulze. The real 

 dermalia of the species seem to be the stauractins called by him the hypodermalia, while 

 these seem to be really represented in the large pentactins occurring as prostalia. A part 

 of the hexactinose oxyhexasters had apparently secondarily taken up a position outside the 

 dermal layer, a process probably analogous to the shifting of Euplectellid floricomes to the 

 extreme outer end of dermalia. Notwithstanding the above fiicts, it is plain that F. E. 

 ScnULZE is at one with me in the idea that forms with entirely hexactinic dermalia may 

 be taken up under the Rossellidre, if other characters permit it. 



