DEVELOPMENT OF AX APODOUS HOLOTHURIAN 
501 
rior end; at the narrowed posterior end, they are less distinct but 
seem to be confined to the sides and ventral surface ; their general 
arrangement is like that found in the auricularia of Labidoplax. 
The uniform covering of cilia seems to have disappeared with the 
development of these bands. There is still no mouth but the 
blastopore remains open. The hydrocoel clearly shows the begin- 
nings of the five primary tentacles and less distinctly the first 
rudiments of the ^'secondary outgrowths." On the pore-canal, 
the thin-walled swelling, regarded as the remains of an ^'anterior 
coelom" is very conspicuous. Near the blastopore are several 
minute, discoidal calcareous bodies. At this stage, the larva of 
Chiridota is rather strikingly intermediate between the correspond- 
ing stage of Labidoplax fSemon, '88, pi. 6, fig. 3) and that of 
Synaptula (Clark, '98, pi. 11, fig. 15). ^\Tlile the external form 
is unlike either, the ciliated bands and calcareous particles resem- 
ble those of Labidoplax, and the general appearance and arrange- 
ment of the inner organs correspond to what is seen in Synaptula. 
In the absence of a mouth at this stage, Chiridota is quite unique. 
A very few larvae, a little beyond the stage just described, were 
found in a small adult at Port Antonio in 1897. The hydrocoel 
was beginning to encircle the foregut, the primary tentacles were 
very conspicuous and the secondar>^ outgrowths were correspond- 
ingh' large. These larvae are peculiar because, in spite of this 
development of the hydrocoel, the uniform ciHation of the body 
still persists and cihated bands cannot be distinguished. 
A large proportion of the larvae found, both at Port Antonio 
and in Bermuda, were well beyond this stage and have the appear- 
ance shown in fig. 3. Four ciliated bands are commonly present, 
though the most anterior is hard to make out and may be wanting; 
the other three are not of uniform width or density at all points, 
but seem to be best developed ventrally. The hydrocoel has com- 
pleted its growth around the foregut and the primary tentacles 
are very conspicuous, completely over-shadowing the secondary 
outgrowths which have developed ver}' little. The polian vessel 
is very evident in the left ventral interradius. The "anterior 
coelom " on the pore-canal has reached its maximum development. 
The right and left coelomic vesicles have coalesced and the result- 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 9, NO. 3, 
