264 s. GOTO; 



Epigastric enterocœl=a portion of the right posterior 

 enterocoel of larva. 



Secondary posterior enterocœl=(left posterior enterocœl + 



right posterior enterocœl) of larva — epigastric 



enterocoel. 



The anterior cœlom is still very spacious, though much less so 

 than in any of the preceding stages, and the plane containing the 

 hydrocœlic pouches makes an angle of ahout 70° witli the sagittal 

 plane, as may be seen from Fig. 18. Hand in hand with this change 

 of tlie position of the plane, the curve formed ))y tlie hydrocœlic 

 pouches has approached more nearly to a circle, and the first and fifth 

 pouches are found on the right side of the body (Fig. 1 8 a &/). Xeither 

 pouch, however, has assumed its final position yet, as may be seen 

 from Fiir. 18, or from the following: formula, 







s 



m 



in which the Arabic numerals represent the liydrocœlic pouches and 

 the iioman tlie arms of the star, while the members of the two series 

 are placed in positions corresj)onding to what occurs in nature, as seen 

 from the aboral side. 



The pore-canal opens into the dorso-posterior corner of the anterior 

 enterocœl, and the stone-canal makes with it a distinct an «le» 



