STRUCTURE OF EARTHWORM ALLIED TO NEMERTODRILUS. 555 



lines of the cells were not in every case so clear. Compara- 

 tively few of the cells contained agglomerations of secreted 

 spherules. The worm which furnished the material for the 

 section described here was immature ; but it must not be inferred 

 from this that the activity of the glandular cells surrounding 

 the nephridia does not commence until the animal is fully 

 mature ; in the youngest individual which I have been able 

 to study the cells in question were crowded with spherules. 

 Their activity is evidently intermittent. 



In fig, 11 are represented three successive nephridia from 

 the post-clitellar region, belonging to as many segments. 

 The nephridia themselves are opaque white bodies, broader 

 towards the middle line of the body as there represented ; on 

 the upper surface it is quite easy to see, even without using a 

 lens, a single loop which appears darker than the surrounding 

 tissue on account of the thinness of its walls. This part of 

 the nephridium will be referred to in connection with the 

 minute structure of the glands. A narrow tube leading from 

 the broad end of the nephridium and perforating the septum 

 traced in the funnel, situated in the segment in front, is quite 

 easy to make out; so is another tube which passes direct to 

 the body-wall in front of the ventral pair of setae ; this tube is 

 the external duct of the nephridium. Anyone who was con- 

 tented, as were some of the earlier investigators, with dissec- 

 tion only^ would be satisfied that in such a drawing as fig. 11 

 the nephridium was sufficiently displayed. The nephridium 

 itself is shown, the funnel and the duct leading to the exterior. 

 But there is apparently no external orifice corresponding to the 

 place where the duct appears to perforate the body-wall on 

 its way to the exterior. 



In examining the body of the worm with a lens I did not 

 succeed, as already mentioned, in discovering the nephridio- 

 pores, which are generally quite easily visible, even without a 

 lens. 



This failure to find the nephridiopores was at once accounted 

 for when I examined a fragment of the cuticle stripped off and 

 mounted in a drop of water. 



