irifi K(fimnnilosa (and doubtless many olhrr Opliiurids), in which 

 also the larval skeleton has disappeared completely, no trace of the Plu- 

 leus-fonn remaining. In these latter larva* ciliated rings are Formed, as in 

 the barrel-shaped larva- of C.omatnlids and Dendrochiroles, and in the 

 pupa-stage of other Holothurians. 



The existence of a true pupa-stage in Opliiurids was first shown by 

 C.aswell (irave 1 ). (Very likely the larva, in which the rearrangement of 

 the vibratile band into an indication of rings was observed by (irave. was 

 a species of the type described here as Ophioplulcus opnlcntus). My own 

 observations in the main agree with those of (irave, however, differing 



l-'i^. Hi'J. A. Ophioplntrii* Mrlxi-liiiikti/li (after M e t sc h n i ko fl ); 15. Ophiopl. Clapari'dci (after 

 C.laparede: modified so as lo represent Ihr larva in ventral view); ('.. Ophiopl. elongatus 



(;d'liT K roll 11). 



from them in some minor points. I find the rings less distinctly indicated 

 than shown by (irave. which may, however, be due to my not having ob- 

 served the metamorphosing larvae in the same lateral position as that in 

 which they are represented indrave's fig. <S, but from the ventral or dorsal 

 side. The anterior "ring" I have not found to be complete, but it may very 

 well be so in a later stage of metamorphosis such as that figured by (irave, 

 the stages in which I have noticed this rearrangement of the vibratile band 

 being less advanced (1M. XXIX, Fig. .'i: PI. XXX, Fig. 2). 1 have been 

 aide lo ascertain that the anterior band of the "pupa"-slage is derived 

 directly from the preoral band of the larva. Another interesting fact is 

 that in some cases, at least, the vibralile band of the poslerolaleral arms 

 in an advanced stage of metamorphosis coalesces in the midline of the 

 larval body, below the developing Ophiurid; how far this is a general rule 

 remains to be ascertained. 



') Caswell Grave. On the oceurrence anmiif; Kchinodernis of larv;r with cilia arranged 

 in transverse rings, with a suggestion as to their signilii-ance. Hiol. Bulletin. V. 1903. p. 17.">. 



