112 HIROSHI OH8HIMA 



Kight : echiiius-rudiuiont well developed. iJornal pore 

 remaining at its original position on the right of the mid-dorsal 

 line, no shifting towards the latter taking place. 



[Case B.] Eunnstrom, 1912 (23), pp. 7-10, 'no. 5'; 

 1918 (26), pp. 420-4, Taf. xiv, figs. 12-lG. 



Left : hydrocoele not formed, anterior coelom remaining 

 rudimentary. Amniotic invagination formed as only a shallow 

 depression, and afterwards disappearing. Pedicellariae present, 

 the dorsal one being already formed while the ventral one was 

 indicated by accumulated cells. 



Bight : anterior coelom consisted of two portions, one being 

 the axial sinus connuunicating with stone-canal and the other 

 representing the madreporic vesicle (' pulsating organ '), which 

 displayed infrequent and irregular pulsation. The dorsal 

 pore was not at first formed, though an ectodermal groove 

 indicated it. After some days a pore opened anew, and the 

 madreporic vesicle began to pulsate more frequently and 

 regularly than before. The stone-canal became split into two 

 parts, one short and still connuunicating with the hydrocoele 

 whilst the other was longer and opened freely into the coelom.^ 

 Thiese two then degenerated and a new stone-canal appeared, 

 so that the hydrocoele regained its connnunication with the 

 exterior. The hydrocoele produced two diverticula, one of the 

 ordinary size and the other much larger. The amniotic invagina- 

 tion was not formed, but instead of it there were two ectodermal 

 pits. These the author at first (23) interpreted as rudiments 

 of the primary pedicellariae, but afterwards (26) corrected 

 his former view and called them ' spine invaginations ' (see 

 p. 138). 



In other classes of Echinoderms, Auriculariae wdth the 

 hydrocoele on the right side only were noticed by Miiller 

 many years ago (19, pp. 101, 109, Taf. v, fig. 1). From com- 

 munications with Dr. Th. Mortensen I have learnt that 

 he found among the larvae of Ophionotus hexactis 

 two specimens which had a right hydrocoele only. I here 



1 ■ Cavite generale ' aud ' Korperhohle ' in the original descriptions. 

 Under these terms the posterior coelom is probably meant. 



