THE DEVELOPMENT OF ASTERINA GIBBOSA. 34.7 
thickened ridge with long cilia, which is the locomotor organ 
of the larva, and is the first thing to disappear in the meta- 
morphosis. 
Stage C is the point which we have now reached, and it is 
characterised by the appearance of this disc for fixation. 
Ludwig compares the larval organ to the non-ciliated processes 
of the Asterid larva, the Brachiolaria. This larva appears to 
be merely a further stage in the development of the well- 
known Bipinnaria, from which it differs in the development of 
three stalked papille from the apex of the preoral lobe, which 
are presumably used forattachment. These papillearise between 
the anterior dorsal and the anterior ventral arms of the Bipin- 
naria: one of them is median and more dorsally situated than 
the other two, and to this arrangement Ludwig compares the 
occasional bifurcation of the ventral lobe of the larval organ of 
Asterina. Now, however, that we know the function of the 
adhesive disc, it is, in all probability, this which is to be com- 
pared to the papillee of the Brachiolaria; and the larval organ 
with its long cilia (compare Pl. 27, figs. 133—135) in all proba- 
bility represents some portion of the ciliated bands of the 
Bipinnaria. Garstang (6) has, in fact, recently described a 
Bipinnaria in which the dorsal arm of the preoral lobe exe- 
cutes muscular movements in the same way as Ludwig asserts 
for the Asterina larva. I repeat, however, that the latter can 
swim by ciliary action alone, without any muscular move- 
ment. 
The internal changes which have occurred between Stages B 
and C are numerous and important. We have already referred 
to the appearance of the stomodzum or larval cesophagus. 
About the same time the primary madreporic pore is formed ; 
it arises by a pocket of the ccelom slightly to the left! of the 
mid-dorsal line, meeting a thickening of the ectoderm (fig. 
26, mp.) and a perforation taking place. The pocket of the 
coelom is called the “ pore-canal” (pe., fig. 26), and is lined 
by cylindrical ciliated cells. By this time the two posterior 
1 This position is not shown in fig. 26; the figure represents a section which 
was rather oblique. 
