STRUCTURE OF EARTHWORM ALLIED TO NEMERTODRILUS. 561 



Fig, 7 represents one of the longitudinal trunks seen in 

 longitudinal section ; it runs for the greater part of its course 

 in the thick layer of gelatinous tissue Avhich bounds the longi- 

 tudinal muscles below ; at the implantation of the setse it 

 passes up into the muscular layer itself. These vessels, as 

 will be seen from the figure, have a somewhat undulating 

 course ; they are occasionally diverted by a large blood-vessel. 

 I have not shown in this figure many branches passing 

 from the longitudinal trunk, because these were not visible, 

 except at a, in the section of which it is a drawing. At 

 N the duct of a nephridium is seen to join the longitudinal 

 vessel. In the anterior segments of the body the ducts of the 

 nephridia pass down in close contact with the hinder septum 

 of their segment to join the integumental network ; in the 

 posterior segments, as is shown in fig. 7, they are not in 

 such close relation to the septum. 



A connection of the nephridia with the pharynx 

 occurs in this earthworm. The ventral wall of the pharynx, 

 as in other Oligochseta, is formed of but little more than the 

 lining epithelium ; the dorsal wall, on the contrary, is extremely 

 thick, owing to the mass of muscles which overlie the epi- 

 thelium. Here and there the epithelium of the ventral 

 pharyngeal wall gives off very short tubular diverticula 

 which are connected with nephridial tubules ; these same 

 nephridial tubules can be traced in the other direction into the 

 longitudinal vessels of the body-wall and so to the exterior 

 (fig. 15). 



An opening of nephridia into the stomodseal region of the 

 alimentary tract in earthworms was first discovered by myself 

 in Acanthodrilus multiporus; subsequently Spencer 

 found numerous nephridial apertures into the pharynx in 

 Megascolides. 



In fig. 15, the opening of a tubule into the ventral side of 

 the pharynx is shown ; these apertures are not numerous, and 

 appear to be regularly paired ; the epithelium of the pharynx 

 dips down, its cells gradually getting shorter ; the nephridium, 

 into which this short diverticulum opens, forms a coil within a 



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