ON THE DEVELOPMENT OF LINGULA ANATINA. 59 



part of the nephridial funnel and finally reaches the body wall 

 in the angle where the lateral and ventral body walls meet. 

 The right wing takes a little different course from the left, 

 owing to the fact that the posterior part of the nephridium is 

 separated from the ventral body wall by the intestine. The wing 

 at first runs dorsal to the intestine and thence passes over to the 

 ventral lip of the nephridium. It is finally attached anteriorly 

 to the place where the ventral body wall meets the lateral one, 

 while posteriorly the attachment is shifted a little dorsally by the 

 presence of the intestinal mesentery. 



The intestinal mesentery (PL VI., Fig. 87, PI. VII., Figs. 

 100, 115, int. mes.) suspends the intestine from the lateral and 

 posterior body wall for a short distance. 



The latter two mesenteries seem to be formed, respectively 

 by the folding of either the visceral, or the parietal layer of the 

 mesoblast, though I have not been able to study their formation. 

 (Cf. p. 56-57.). 



The gastro- parietal band is of quite a different nature from 

 any other mesentery. Strictly speaking it is not a mesentery at all, 

 but only a lifting up of the peritoneum, in which some tendon- 

 like cells have been produced. These cells are easily recognized by 

 their stronger refractivity. In dorsal view (PL V., Fig. 80, and 

 PL VI., Figs. 83, 84, gst. pr. bd.) the band appears to divide the 

 body cavity into the small anterior, and the large posterior, parts, 

 though in reality both parts communicate freely with each other, 

 as the band is still a low ridge. The baud begins from the 

 ganglion, turns backward and, passing along the anterior part 

 of the otoeysts, stops short at the median part which is occupied 

 by a highly glandular epithelium. I will here lay stress upon 

 the fact that the band is quite independent of the otoeysts. This 



