THE DEVELOPMENT OF ASTERINA GIBBOSA. 369 
divided into distinct rounded lobes lined by cylindrical epi- 
thelium (rhy.), in all respects similar to those of the left, and 
the rudiment opens by a narrow but distinct slit into the 
anterior celom. This larva also exhibits another very common 
abnormality, which I do not in the least understand ; this con- 
sists of the breaking up of the gut epithelium into a mass of 
cells having the appearance of mesenchyme, which choke up 
the lumen, but leave the walls almost denuded of epithelium, 
consisting chiefly of the basement membrane. This curious 
change can take place at any stage from the commencement of 
the differentiation of the ceelom, up to young adults a month 
old: in one such specimen it affected the pyloric ceca. As to 
what its meaning is, I confess I am entirely in the dark. 
Figs. 87 and 88 represent a most remarkable larva. The 
development of the left posterior coelom would indicate that it 
had reached Stage E, but the left hydroccele consists only of 
four lobes, and is poorly developed. There are two rudiments 
of a hydrocele on the right side; the more ventral has three 
distinct lobes lined by cylindrical epithelium (7’hy’., fig. 88), 
and opens by a distinct opening into the anterior coelom; the 
more dorsal is perfectly normal (rhy., fig. 87); but, as if 
to emphasise the fact that, in spite of the presence of the 
other rudiment, it does in fact represent a hydroccele, we find 
in connection with it a second small stone-canal and pore- 
canal (p’c’. st’. c.). The relation of these to the right hydro- 
coele may seem unusual; instead of the canal (conjoined stone 
and pore-canal) leading from the hydroceele to the anterior 
ccelom and thence to the exterior, it appears to lead from the 
anterior ceelom to the hydrocele and thence to the exterior. 
This apparent difference may be reconciled with the arrange- 
ment on the left side by observing the angle which stone- 
canal and pore-canal make with one another. Woodcut 8, p. 
370, shows that this is an acute instead of an obtuse angle, and 
hence that stone-canal and pore-canal have coalesced laterally ; 
Woodcut 2 shows for the sake of comparison the normal stone- 
canal and pore-canal and their relationship to the left hydro- 
cele and the axial sinus or anterior celom. 
