16 K. MITSUKUllI : STUDIES ON 



are of different sizes in different parts of the body. Those in the 

 dorsal perisome (textfig. 2 h, c) are as a whole larger than those in 

 the ventral perisome ; the largest are found in the basal conical warts 

 of the dorsal papillae (length of the arm measming from 0.12 to 

 0.23 mm.). The dorsal surface between the basal conical warts of 

 the papillae is strewn much more sparsely than in the warts witli 

 smaller and generally simple triradiate spicules (length of the arm 

 measuring from 0.07 to 0.08 mm.). The calcareous spicules in the 

 ventral perisome {d) are on the whole much smaller than those 

 in the dorsal perisome and are also much more sparse (with 

 arms 0.02 — 0.05 mm. long). Quadriradiate spicules are found 

 in the dorsal papilla above the basal conical warts, but never 

 in any considerable number. In papillae which are drawn out 

 to a fine point there is no terminal disk. In those which are only 

 soniewhat contracted at the top, calcareous deposits are crowded 

 and give an appearance as if they formed " a sort of a 

 terminal disc " (Theel) ; but there probably exists no actual 

 disk. In ventral pedicels triradiate spicules are sparse and 

 a terminal disk is distinct. Tlie supporting rods (/, g) in them 

 have both ends pointed (0.43 — 0.65 mm. long). In dorsal 

 papillae (c) their ends are enlarged and perforated, not pointed 

 (about 0.5 mm. long). Spicules in the tentacles are somewliat 

 like those in the dorsal papillae but smaller (0.11 — 0.22 mm. 

 long). 



Genital tubes in two bundk'S. Stone-canal single, running 

 directly in front of, and along with, the genital duct attached to 

 the dorsal body-walk Polian vesicles in one specimen three, of 

 which two are slender and tube-like, and one large and vesicle- 

 like. The large vesicle and one of the slender ones were attached in 

 the left ventral interradius, and the remaining slender one in the 



