16 K. MITSUKUIU : STUDIES ON 



arc of ilillc'i'e'ut sizes in dilUTciil parts ol' thu body. Tlioso in the 

 dorsal jK'i-isumu (tcxtli,!::. '2 b, c) are as a wlioio larger t.li;i.u those in 

 the Ventral perisoini^ ; tlu- largest are found in the basal conical warts 

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

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

 the pnpillae is strewn much more S})arse!y tlinn in tiie warts with 

 smaller and gent'rally simple triradiate spicules (length of the arm 

 racasurhig from 0.07 to O.OS mm.). The calcareous spicules in the 

 ventral perisome (r/) are on the whole much smaller than those 

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

 arms 0.02 — 0.05 nun. long). (()uadriradiate spicules are found 

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

 in any considerabk' numlier. In j)ajiillae which are drawn t)ut 

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

 somewhat contracted at the top, calcareous deposits are crowded 

 and give an appearance as if tluy formed *' a sort of a 

 terminal disc "' (Tukel) ; but (here probably exists no actual 

 disk. In venlral pi'dicels triradiate spicules are sparse and 

 a terminal tlisk is distinct. 'J'he supporting rods (./', //) in them 

 have botli ends pointed (0.43 — 0.(55 inm. long). In dorsal 

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

 (about 0.5 nun. long). Spicules in the tentacles arc somewhat 

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

 long). 



Genital tubes in twt) bundles. Stone-canal single, running 

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

 the dorsal body-wall. Polian vesicles in one si)ecimeu three, of 

 which two are slemler 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 



