THE DEVELOPMENT OF ASTERINA GIBBOSA. 363 
future star-fish are decidedly oblique to one another, being 
closely apposed posteriorly, but anteriorly separated by the 
thick base of the stalk. We see also that a lateral shift of the 
arm rudiments has commenced, No. V having passed beyond 
the hydroccele lobe No. 5, and so also in the case of the others. 
A second pair of rudiments of tube-feet has grown out from 
each lobe of the hydroceele, so that they are now 5-partite. 
Figs. 62—69, Pl. 21, are taken from a most instructive series 
of sections of a larva of this age, and are intended to give a 
clear conception of its internal anatomy. We are struck at 
once by the great reduction of the stalk, although ventrally 
(fig. 66) the stalk ccelom still communicates with the axial 
sinus. In fig. 65 we see the last trace of the secondary ventral 
communication between the left posterior ceelom (/p’c’) and 
the axial sinus a’ (anterior coelom) just closing. The secondary 
dorsal opening persists much longer, but fig. 63 shows us that 
it also is beginning to be closed. Comparing figs. 64 and 65, 
we see that the adult cesophagus has acquired two lateral out- 
growths, one directed anteriorly, the other posteriorly ; there is 
also a third horn directed dorsally, which of course cannot be 
seen in the sections. Fig. 67 shows how the oral ccelom (07.c.) 
now half encircles the adult esophagus. As to the arm rudi- 
ments, the most interesting thing is to notice the wide separa- 
tion of No. V from the hydrocele lobe No. 1. When the 
intervening tissue shrinks, a change which involves a reduction 
in size of the axial sinus (compare a.’, Pl. 22, figs. 75 and 76) , 
the metamorphosis will be complete. The incipient shift of the 
other rudiments is seen, especially in the case of Nos. II and 
III, the latter falling between lobes 3 and 4. 
By a continuation of the processes referred to above, viz. 
the constriction of the base of the stalk, the increasing 
flexure of the body on it, and the continued growth of the 
hydrocele and left posterior coelom, we soon reach Stage G, 
which is represented in Pl. 18, figs. 17 and 18. We notice the 
great reduction of the stalk (which is now usually directed 
downwards almost at right angles to the disc, though the 
extent of the angle between the two varies) and the completion 
