220 HIROSHI OHSHIMA 
The deposits formed in the wall of the axial sinus consist of 
a loose basket-work, which forms a short tube opening on both 
ends surrounding the stone-canal. There is another opening 
which is directed dorsad, corresponding to the thin-walled part 
of the vesicle. Ludwig (28, p. 27) noticed a similar structure 
in the pentactula of Cucumaria parva, with a wide open- 
ing directed anteriorly. 
TExtT-FIG. 5. 
mp------F> 
Seventh-day metadoliolaria. Right-side view to show calcareous 
deposits. x 100. cd = deposit of integument; cr = rudiment 
of calcareous ring ; en = enterocoele ; g = gut; mp = axial sinus ; 
p= papilla on the tip of tentacle; pr= pre-oral hood; ¢t, = 
tentacle. 
Those which appear at the bases of the tentacles are a delicate 
netted ring, giving off a pair of anteriorly-directed pointed 
processes at each radius. These represent the rudiments of 
the radial segments of the calcareous rng. It has been shown 
by Ludwig (22, p. 611; 28, p. 27) and Clark (7%, p. 67) 
that the calcareous ring is first represented by five radial seg- 
ments. In C. echinata it does not consist of five separate 
pieces but of a continuous ring, as stated above. 
