258 



s. GOTO ; 



liiere is another portion of the hody cavity wliich remains to be 

 described in stage C ; it is the " Centralbhitgeflecht " of Ludwig ['<S2], 

 the " dorsal organ " of Vmvy ['95], l)nt which has clearly been shown 

 by MacHride ['96] to be a, portion of the enteroctel. The latter author 

 calls it " oral coelom " ; but as tliis tenn lias been applied to the left 

 enterocœl in crinoids, I prefer to call it, from the position whicli it 

 occupies in the star, " periœsophageal enterocicl." It arises as a bud 

 from the dorso-dextral anterior end of the left posterior enterocol in a 

 stage between 15 and C ; it is at first a solid rod of cells but afterwards 

 acquires a lumen. In stage C (Figs. 19 & 22, PI. XX) it is a tubular 

 structure opening at one end into the left posterior enterocol at the 

 place above specified and ending blindly on the left side of the caixliac 

 portion of the stomach at about J the distance between the ventral 

 and dorsal sides. It is irregularly curved, and proceeds from its origin 

 at first dextrad then slightly anteriad and then sinistro-ventrad and 

 posteriad ; it therefore encircles at this stage about ^ or ])erhaps \ of the 

 stomach on the left side. It appears very conspicuous in cross sections 

 at about the level of the pore-can;d, in the mesenchyme lying between 

 the left posterior enterocu'l, the stomach, and the rudiment of the 

 water- vascular system (Figs. 19 & 22). 



In stage C the rudiment of tlie stone-canal is f:)rmed. It begiris 

 as a thickened elongated patcli of tlie peiitoneal epithelium on the dextro- 

 dorsal wall of the left anterior enteroc(el, contiguous to the inner open- 

 ing of the pore-canaJ (Fig. 20, PI. XXI). The thickened patch assumes 

 the form of a furrow which subsequently closes into a canal, the closure 

 commencing next the inner o])eningof the pore-canal, but leaving it un- 

 touched ; so that if one were to look at the inner opening of the pore- 

 canal from inside the anterior enterocœl, one would see it become some- 

 what elongated with the first formation of the rudiment of the stone 

 canal, and then as the latter becomes closed there would be two openings, 



