294 HIROSHI OHSHIMA 
case was reported by Clark (8, 1901, pp. 168-70) in another 
brooding form, Psolidium nutriens. The young had the 
five primary tentacles just indicated and a pair of pedicels, 
which latter were very remarkable in size and apparently served 
to attach them to the inner skin of the mother’s back. It is 
interesting to note that in such a form characterized by the 
degenerated state of the mid-ventral radial canal and its appen- 
dages in contrast to a comparatively stronger development. of 
the lateral ventral ones, the first appearing pedicels still belong 
to the former and attain such a remarkable degree of develop- 
ment. 
15. YounNG. 
In the post-larval stage which I call young, five more tentacles 
are added to the primary five, the pedicels increase by degrees, 
and, moreover, retractor muscles, respiratory trees, genital 
organs, &e., appear, so that a mimature adult Cucumaria 
is now formed. 
This stage has been known in many cases. Danielssen 
and Koren (11) first described and figured the young of 
C. frondosa. Among others the following imstances may 
be enumerated: C. glacialis by Mortensen (82), 
C. crocea by Ludwig (28), MacBride and Simpson 
(27), Thyone rubra by Clark (8), C. saxicola by 
MacBride (25, 1912, Pl. i, fig. 41; 26, Text-fig. 402), 
C.ijimai, C. lamperti and Thyone imbricata by 
the present writer (88, 1915). Besides these, young referable to 
Cucumaria were reported from the Antarctic Seas by 
MacBride (25, pp. 3-7; Pl. i, fig. 3; Pl. ii, figs. 5-8) and 
Mortensen (84, 1913, p. 87; Pl. xu, figs. 6, 7). 
From want of materials in consecutive series, I am compelled 
to leave untouched many important problems in connexion with 
the origin of several organs. I give here only some points 
of my observations. 
Stone-Canal.—The pore-canal which has in the preceding 
stage been distinctly seen lyimg in the dorsal body-wall has 
1 Tdentified doubtfully with C. lactea. 
