202 HIROSHI OHSHIMA 
His fig. 228 resembles very much what I observed in 
C. echinata in a corresponding stage. 
Ludwig (22, p. 605) observed in the third-day larva of 
C. planci that the hydro-enterocoele had separated from the 
rest of the archenteron, and again divided into the hydrocoele 
and two enterocoele vesicles. Some larvae were somewhat 
younger, and in them the hydro-enterocoele was still in con- 
nexion with the archenteron. In these statements he seems to 
have been unable to give the time and sequence of the separations 
of those vesicles. Selenka was of the opinion that the hydro- 
enterocoele, at first as long as it is connected with the gut, lies 
on the dorsal side of the latter, but shifts to the left side about 
the time when the separation sets in. Ludwig observed, 
contrary to Selenka, that it had been lying on this side from 
the beginning. I agree with Ludwig on this point. 
Newth (86, p. 685) could not be sure about the breaking 
off of the archenteron in C. saxicola and C. normani, 
bemg only able to say that the water-vascular system, the 
posterior (perivisceral) coelom, and the gut are separated from 
successive regions of the archenteron in the order named, begin- 
ning at the anterior end. In C. normani the separation of 
the enterocoele was complete by the middle of the third day, 
though in some individuals the hydro-enterocoele connexion 
was not then broken. 
The hydrocoele then increases in breadth again, stretching 
round the right side of the body, and its free anterior margin 
begins to divide into lobes, which are indistinct at first but 
rapidly become distinct processes. ‘These changes as well as 
those of the enterocoele to be mentioned below vary very 
much according to different individuals. The following state- 
ments seem, however, to represent what is most frequently met 
with. 
Hydrocoele.—tIn the beginning three lobes are formed 
(Pl. 9, fig. 17, hy). The first is narrow, situated at the left 
anterior corner, the second is broad, formed of the greater part 
of the anterior margin of the hydrocoele, and the third is again 
narrow, situated on the right ventral edge of the hydrocoele 
