no HIROSHl OHSHIMA 



normal young. All tho sets of primary unpaired and first- 

 paired tentacles, pedicellariae, pointed and square-ended 

 spines, were formed precisely as in the young which had 

 metamorphosed from normal larvae. It was hoped that 

 they would develop further to the stage when the asymmetrical 

 arrangement of the organs, above all the peculiar coil of the 

 intestine, would be more pronounced. Unfortunately, however, 

 they were all lost after ten days, probably b(*ing destroyed by 

 a tiny Gasteropod which had been carelessly put into the jar 

 together with some C'orallinae. 



Internal Structures. — So far as the internal anatomy 

 of the larva is concerned, the following short account is all 

 we can learn. The transverse sections of the larva (Text- 

 fig. 2) are exactly the mirror-images of those of normal larvae, 

 so that one cannot distinguish them from sections of a normal 

 larva mounted upside down. An eleven-day-old larva has the 

 pore-canal {j)c) still distinctly opening on the right side of the 

 mid-dorsal line (dj)), a madreporic vesicle (mv) lying close to 

 the canal, situated at its median side but without any com- 

 munication whatever with it. The canal then leads to the 

 thin-walled axial sinus (ax) which lies close to the oesophagus 

 (oe). The stone-canal (st) comiects the axial sinus and the 

 hydrocoele just as in the normal case. The hydrocoele (hy) 

 situated on the right side of the stomach (g) has just begun 

 to produce lobes, and an amniotic invagination {am) has 

 already appeared. No traces of hydrocoele, stone- and pore- 

 canals were found on the left side. From want of material 

 it is not known on which side of the posterior coelom the 

 genital stolon w^ould be formed. 



Thus, w^ith doubtful exception of the pedicellariae and genital 

 stolon, the internal organs as w-ell as the external characters 

 showed perfectly the inverse situs in every detail, so far as 

 I could examine. With regard to the pedicellariae and genital 

 stolon I refrain from expressing a definite opinion. We may 

 expect to find some aberrant types as might be suggested 

 from fm'ther descriptions of double-hydrocoele larvae. 



Similar cases previously known. — So far as I am 



