120 TIIROSIII OHSHIMA 



No asymmetry in shap(^ of tho stomach was to \)(' found. 

 The unpaired spine appeared at the hind end on the median 

 hne. The larva hved for forty-six days and was at the end of 

 that period very near to metamorphose, hut was missed 

 suddenly, and hence no further information on the internal 

 structures could be obtained. 



[Case 20.] Echinus miliar is. Culture 9, ' treated '. 



The larva was found and killed when it was fifteen days old. 

 The flattened axial sinus, pore-canal, stone-canal, and lobed 

 hydrocoele developed nearly symmetrically on each side. Only 

 on the right side the pore-canal ended in a solid cell-mass, 

 and no dorsal pore opened. Amniotic invaginations formed 

 on both sides, the right one being smaller than that of the left 

 side. No madreporic vesicle found. 



(d) Two hydrocoeles formed on one side. 



[Case 21.] Echinus miliaris. MacBride, 1918 (15), 

 p. 339. Reared in London. 



There were formed two hydrocoeles on the right side due to 

 the splitting of the hydrocoele bud which had been formed at 

 the hinder end of the anterior coelom. One of them normally 

 developed and had associated with it an amniotic invagination. 

 The other, smaller and situated posteriorly to it, also possessed 

 well-developed lobes. There was, however, no amniotic 

 invagination for the smaller hydrocoele. 



II. Hydrocoele formed on the left side only as 

 in normal larvae, but some abnormalities 

 found in other associated structures. 



(a) Amniotic invaginations on both sides. 



[Case 22.] 8trongylocentrotus lividus. Runn- 

 strom, 1912 (23), p. 7, 'no. 4'; 1918 (26), pp. 414-15, 

 Taf. xiii, figs. 5, 6. Reared at Monaco. 



Left : anterior coelom extending along dorsal side to the 

 right to form a canal, which had no external opening. It 

 seems, however, that an opening existed in an earlier stage. 

 Stone-canal ending blindly at the posterior end. Hydrocoele 

 isolated, with five lobes, and a blind canal sent towards the 



