204 HIROSHI OHSHIMA 
antero-ventral in position, the other smaller and on the left 
dorsal side stretching posteriorly (Pl. 9, figs. 17, 18, le, re). 
The former corresponds with the left enterocoele of other echino- 
derms, while the latter, although situated at first on the left 
dorsal side, is the right enterocoele. Selenka (45, p. 171) 
noticed in C. planci that the peritoneal vesicle (enterocoele) 
divides, immediately after being separated from the vascular 
vesicle (hydrocoele), into two ellipsoid vesicles lying on the right 
and left sides of the gut respectively. Likewise in H. tubu- 
losa the enterocoele which stretches behind and below the gut 
divides into two vesicles which lie symmetrically on each side 
of the gut. ; 
Stomodaeum.—The stomodaeum is formed by an en- 
circling of the slit-like depression and a sinking down of the 
included area. It contains a thin lumen, extending parallel to 
and below the external surface, which opens through a narrow 
orifice to the exterior (Pl. 8, fig. 164; Pl. 9, fig. 184, st). 
The syncytium (sy) extending over the stomodaeum grows 
between the hydrocoele and enterocoeles to form a solid cell- 
mass running backwards to jom with the gut. The gut is of 
a single layer of cells but very thick, leaving a narrow lumen 
inside (PI. 9, fig. 18 B, 9). 
12. Douronaria. 
The doliolaria, or barrel-shaped stage, is reached about at 
the fortieth to the fiftieth hour, i.e. on the third day. This is 
characterized by the acquisition of three transverse ciliary 
bands on the posterior half of the body, the appearance of 
rudiments of the pedicels, and the further development of the 
five primary tentacles and radial canals. This stage lasts until 
the fourth day or even the eighth day or more." 
The larva measures above 500 in length, and swims usually 
immediately beneath the surface of the water, being either vertical 
or oblique in position. Cilia beat usually towards the posterior 
! My own culture showed no evidence of changing into the pentactula- 
stage even on the eighth day, when I had to leave Misaki and could not 
follow any further changes, 
