THE DEVELOPMENT OF ASTERINA GIBBOSA. 351 
septum dividing the two portions of the ccelom from each other 
become again closed during the metamorphosis. 
The left hydroccele has become much more sharply separated 
from the anterior coelom than in the last stage, though in the 
region of the third lobe the hydroceele still opens widely into 
the anterior ccelom (P1.19, figs. 388—41; Pl. 20, figs. 44—46). 
We saw that the pore-canal in Stage B originated a little to 
the left of the middle line; now, however, owing to the in- 
creasing predominance of the left side, it is shifted to the right 
of the median plane (pe., fig. 44). The stone canal (séc., figs. 
45 and 46) arises as a groove along the anterior face of the 
transverse septum forming the hinder wall of the anterior 
celom. The central portion of this groove soon becomes closed 
to form a canal, opening at one end into the hydroceele between 
lobes 1 and 2 (fig. 46), and at the other into the anterior ceelom 
(fig. 45); and this opening is in this stage entirely inde- 
pendent of the opening of the pore-canal. 
I have referred more than once to the predominance of the 
organs of the left side. This is strikingly shown in the stage 
we are considering by the narrowness of the right posterior 
ceelom as compared with the left. Already in Stage B we have 
seen that the left posterior ccelom has begun to sweep round 
to the right on the ventral side of the right posterior ccelom ; 
this occurs more and more, and in the stage we are considering 
in the most ventral sections (fig. 41) the right posterior coelom 
is entirely absent. The left not only passes under it, but toa 
certain extent interposes between its anterior portion and the 
gut (figs. 39 and 40), and here opens freely into the anterior 
celom! (fig. 40) by the secondary ventral communication de- 
scribed above. This portion of the left ceelom we may call its 
right ventral horn ; it plays a most important part in the meta- 
morphosis, and it is marked /‘p’c’. in all the figures. 
Ludwig failed entirely to recognise the left posterior ceelom 
1 T may anticipate a little by informing the reader that the anterior ccclom 
gives rise to the axial sinus of the adult ; a space which opens to the exterior 
by the pore-canal and into the left hydroccle (water-vascular ring) by the 
stone-canal. 
