554 H. LYSTER JAMESON, 



to develop to any considerable thickness. I regret that I have been 

 unable, owing to the state of preservation of my material, to make 

 any observations upon the peri-intestinal sinus discovered by Rietsch in 

 Bonellia and Thalassema. I can however determine the presence of such 

 a structure, and am convinced that it is no t, in this species, continuous 

 with the blood vascular ring which embraces the hinder part of the 

 crop. Pigmented cells are often to be seen in the walls of the in- 

 testine. 



The epithelium of the intestine (Figs. 18, 19 and 20) is simple 

 in comparison to that of the crop. I cannot detect cilia except in 

 the ciliated groove and secondary groove, but this may be due to the 

 defective state of preservation. The epithelium consists of columnar or 

 thread-like cells, the free ends of which broaden out into a pavement 

 (Fig. 18 ep. c). They have a dark cuticular margin, an elongated nucleus 

 (ep.n) and granular contents, and stain more deeply than the interstitial 

 glandular and basal cells. Their free ends show a tendency to pro- 

 ject as processes into the cavity of the intestine, which give the epi- 

 thelium an irregular surface. Between these cells lie oval or bottle- 

 shaped cells (Fig. 18 gLc), with round, less deeply staining nuclei (gl.n) 

 and lightly staining contents , resembling the simplest type of gland 

 cells seen in the crop. Many of them are seen to open out by narrow^ 

 ducts between the columnar cells. The deeply staining glands, which 

 characterize the oesophagus and crop, are absent from the intestine. 



In horizontal sections of this epithelium which cut the expanded 

 surfaces of the columnar cells (Fig. 20) we get a pavement -like 

 mosaic of the latter {ep. c), between which the necks of the glands 

 can be seen opening-out (gl). Such horizontal sections as cut the cells 

 at a lower level show the columnar cells forming a nieshwork round 

 the circular sections of the glands (Fig. 19). 



The epithelium of the collateral intestine is composed of low 

 cells which are not much higher than tliick. So far as I can see there 

 are no glands here. Glands are also apparently absent from the 

 ciliated groove and the secondary groove. 



The coecum, which marks the termination of the intestine, 

 generally contains the brown amorphous matter already noticed in 

 Th. neptuni and erythrogrammon. Its walls are muscular, and the 

 epithelium is low, flattened and pavement-like. 



From the coecum to the anus runs the rectum, about 5 — 7 mm 

 long, into which the anal vesicles open ventro-laterally by two ciliated 

 openings. I have nothing to add on the structure of these vesicles. 



