914 HIROSHI OHSHIMA 
was found as a small blunt outgrowth produced at the point of 
closure. 
From the table on p. 215 the followime features may be 
summarized : 
1. Of the five primary tentacles the one situated in the left 
dorsal interradius appears last (nos. 1-4). 
2. To the four tentacles and one mid-ventral radial canal the 
right dorsal radial canal is first added (nos. 2-4). 
3. The left dorsal radial canal appears at about the same time 
as the appearance of the fifth tentacle, after which the right 
ventral radial canal follows immediately (nos. 5-7). 
4, The appearance of the left ventral radial canal is still 
later (no. 10). 
5. The appearance of the Polian vesicle in some cases precedes 
the closure of the rmg canal (nos. 8, 9, and 12), and in others 
it is later (nos. 6, 11, 18, and 15). 
6. The formation of the axial sinus also in some cases 
precedes the closure of the ring (nos. 8, 9) and in others it 1s 
later (nos. 6, 11). 
7. The closure of the rmg takes place in most cases after five 
radial canals have all appeared. 
Stomodaeum.—Now the position of the stomodaeum 
can be determined by the establishment of the mid-ventral 
radial canal. It hes in front of the first ciliary band, and at about 
30° to the left of the sagittal plane. The ectoderm covermg the 
interior of the atrial cavity is pushed up by the growing tentacles, 
forming an epidermal covering for the latter (PI. 9, fig. 25, at). 
The orifice is often found plugged up by the left ventral tentacle 
which lies nearest to the stomodaeum (Text-fig. 5, t;). Newth 
(36, p. 684) noticed the asymmetrical position of the stomodaeum, 
while Ludwig (22, p. 610) observed the same fact but inter- 
preted it erroneously. He was of the opinion that the larval 
symmetry plane is not coincident with that of the adult, and 
thought that the left ventral tentacle stands nearest to the 
mid-ventral line. 
Simultaneously with the growth of the primary tentacles 
and the diminution of the pre-oral hood, the stomodaeum 
