120 HIROSHI OHSHIMA 



two kinds of abnormalities we may first examine those known 

 cases of double-hydrocoele and other abnormal larvae, and 

 then c(msider the behaviom* of individual organs and the 

 interrelations to be found between them. 



I. Hydrocoeles formed on both sides. 



(a) Right hydrocoele and its associated structures more or 

 less incomplete. 



[Case 1.] Strong ylocentrotus lividus. Runn- 

 strom, 1912 (23), pp. 3-5, ' no. 2 ' ; 1918 (26), pp. 417-18, 

 Taf. xiii, figs. 8 a, h. Reared at Monaco. 



Left : anterior coelom large, divided into three regions : 

 first, the ampulla to which the stone-canal opens ; second, the 

 main body of the axial sinus extending transversely to the 

 right and communicating with th(^ third region, the madreporic 

 vesicle. The last-named vesicle exhibited no pulsating move- 

 ment. Pore-canal and dorsal pore lacking. Stone-canal and 

 hydrocoele well developed, the latter produced into five lobes. 

 Amniotic invagination deeper than normal. 



Right : anterior coelom smaller than that of the left, 

 with pore-canal given out towards the epidermis, without, 

 however, an opening to the exterior. Stone-canal shoA\'ing 

 a sign of degeneration, its anterior end beginning to be absorbed. 

 Hydrocoele smaller than that of the left side. Amniotic 

 invagination did not form on this side. Posterior coelom 

 produced into an anterior process, which probably corresponds 

 with genital stolon. 



[Case 2.] Strongylocentrotus lividus. Runn- 

 strom, 1912 (23), pp. 5-7, ' no. 3 ' ; 1918 (26), pp. 413-14, 

 Taf. xiii, fig. 4, Reared at Monaco. 



Left : anterior coelom large, consisting of two regions, one 

 on the left, connected with stone-canal, the other on the right, 

 corresponding with madreporic vesicle. The latter became 

 later separated from the former, and was not seen pulsating. 

 Pore-canal absent. Stone-canal and hydrocoele well developed, 

 the latter produced into five lobes. Amniotic invagination 

 formed but remaining totally undifferentiated. 



