COE: NEMERTEANS OF WEST AND NORTHWEST COASTS. 137 



organs. The basement layer is homogeneous, except a's it is trav- 

 ersed by extremely delicate fibers which pass from the underlying 

 layers to the integument. 



The body parenchyma, or gelatinous tissue, is reduced to a mini- 

 mum, being found only to a slight extent around the lateral blood 

 vessels, nephridia, and the basal portions of the immature genital 

 glands. 



Cephalic glands are completely wanting as in most related 

 species. The rhynchodaeum, however, is lined with a layer of 

 columnar glandular cells. There are no other glands in the head 

 beneath the integument. 



Alimentary canal. — The mouth, situated immediately behind the 

 brain, is of comparatively large size. In the living worm the 

 esophagus can be seen to be divided into two distinct portions, the 

 anterior of which is clearer and less opaque than the posterior. As 

 shown in PI. 5, figs. 47, 49, the mouth opens into a wide esophageal 

 cavity which has smooth walls, and which continues backward about 

 two thirds the distance to the brown band, or about half way from 

 the mouth to the lateral sense organs. This esophageal cavity is 

 lined with the usual columnar ciliated and glandular cells, the former 

 being the more superficial and covered with numerous short cilia. 

 The esophagus proper opens directly into a posterior esophageal 

 cavity, or stomach (PI. 5, fig. 47, s^), which is considerably longer 

 than the anterior cavity, and which is lined with a very different 

 sort of epithelium. The line of demai'cation between esophagus 

 and stomach is indicated in PI. 5, fig. 47, by the letters e.o. 



Anteriorly the stomach cavity is of about tlie same diameter as 

 the esophagus, but in the region of the thickening of the internal 

 circular muscles (PI. 5, fig. 47, a) it becomes reduced to a compara- 

 tively narrow tube, and posterior to these muscles enlarges again to 

 more than its former diameter. Its walls are more or less folded 

 and wrinkled, especially on the ventral side, where the epithelium 

 is thicker than elsewhere (PI. 7, fig. 55; PI. 9, fig. 61). In longi- 

 tudinal sections of the region posterior to the thickening of the 

 circular muscles the ventral wall of the stomach appears to be 

 thrown up into conspicuous folds (PI. 9, fig. 61). These are not 

 permanent pouches, however, but temporary folds of the epithelial 

 lining only. When the body is extended these apparent pouches 

 become much reduced or disappear completely. The same is true 

 of the still more conspicuous intestinal folds. 



