174 



THE NEMERTINI 



relatively short extent ; it has only a feebly developed muscular 

 coat, and differs histologically from the enteron, which is directly 

 continuous with it. In the Metanemertini, however, this foregut 

 is much longer and divisible into the following regions : (1) A 

 narrow, buccal tube passing from the mouth as far as, or beyond 

 the brain ; (2) a dilated " stomach" ; and (3) a narrow " pylorus 



N 



Pelagonemertes rollestoni, Moseley, dorsal view (from Perrier, after Moseley). A, anus; C, 

 cerebral ganglion ; D, intestinal caecum ; G, rhynchocoel ; I, intestine ; m, longitudinal 

 muscles ; N, lateral nerve trunk ; 0, ovaries ; P, proboscis, partially everted ; t, circular 

 muscles ; V, lateral blood-vessel. 



tube " ; both lined by gland cells (Fig. XII.). This last region opens 

 into the enteron on its dorsal surface, so that there is a longer or 

 shorter ventral " caecum " (m) differing in no way from the midgut 

 itself. This caecum may, like the latter, be produced on each side 

 into a series of diverticula. This caecum originally communicates 

 with the exterior by means of the blastopore ; when this closes, the 

 stomodaeum, having arisen some little way in front of it (Lebe- 

 dinsky), joins the enteron on its dorsal surface; whereas, in other 



