rudiment bends around the posterior end of the post- 

 erior enterocoelo pouch and opens to the exterior 

 through the blastopore ,Fig,4,b, 



It is from the left side and anterior end or 

 the ventral pouch that the hydrocoele grows out hence 

 the confirmation of BURYS statement that it arises 

 from the left posterior anterocoele in ophiurids. 



In most echinoderms the postc-rior enteroeoeles 

 originate as paired structures and if the statements 

 of BURY and HcBRIDS ar: correct A that the left post- 

 erior enterocoelo or the larva forms the hypogastric 



. cavity of the adult and the right posterior 

 enterocoelo goes to form the epigastric coelom"^: 

 then, according to this, the largs ventral pouch 

 which I regard as the fused right ana left poster- 

 ior enteroeoeles ^really represents the left only be- 

 cause it takes no part in the formation of the epi- 

 gastric body cavity of the adult ophiurid but does 

 pass directly into the hypogastric. 



The origin oi 1 the epigastric enterocoelo is 

 discussed in the description of "C" in which stage 

 its rudiment is first found over" the stomach. 



lily reason for the 'ventral pouch of "B" as the 



A 



fused right and left posterior enteroeoeles is that 



