enterocoeles .Fig,4.hy. The cavity of this pouch, 

 which is the rudiment or the hydrocoele, is in wide 

 communication with the archenteron. 



From the wall forming the convex side of the 

 hydrocoele there are, even at this early stage in 

 its formation, five outgrowths which arc th-s begin- 

 iiigs of radial canals of the adult ophiuran.Fig,4, 

 1,2,3,4 and 5 . 



The whole hydrocoele is curbing round to the 

 right to encircle the oesophagus which latter is mak- 

 ing its first appearance in this stage as a shallow 

 but definite pit in the central part of the ventral 

 ectodermal wall .Fig ,4, oe . 



To avoid confusion the hydrocoele was spoken 

 of above as arising from the archenteron but, as will 

 be seen in th? transverse section(Fig,5,)tafcen in a 

 plane posterior to the origin of the hydrocoele, a 

 differentiation is taxing place in the archenteeon 

 which enables us to distinguish in it the- rudiments 

 of two structures, the posterior enterocoeles and 

 the stomach. By a longitudinal circular furrow the 

 archenteron is being cut horrizontally into a large 

 ventral pouch, the posterior enterocoeles, pe. , and 

 a smaller dorsal one, the stomach, s. This stomach 



