148 bulletin: museum of compaeative zoology. 



first there are a few straggling fibers only, but farther back they 

 increase in numbers until they form the enormously thick layer of 

 internal circular muscles. This layer, then, would represent merely 

 a great development and ventral prolongation of the proboscis 

 sheath musculature. The character of the layer is the same as is 

 seen m the proboscis sheath in the intestinal region ; that is, circu- 

 lar fibers interlaced with those which run longitudinally. 



Between the rhynchocoel and the esophagus is a musculature con- 

 sisting of a dorsally placed sheet of circular fibers, and a ventral 

 layer of longitudinal muscles. These longitudinal muscles are 

 evidently homologous with the massive muscle-bundle found in the 

 same position in Carinomella (p. 129). These layers are most 

 distinct in the anterior esophageal region, and practically disappear 

 when the internal circular muscles become most massive. 



The rhynchocoel is of greatest diameter in the anterior portion of 

 the esophageal region (PI. 13, fig. 81), narrows greatly in the 

 nephridial region (PI. 13, fig. 82), and widens abruptly again at the 

 point where the internal circular musculatiire ceases. 



Alimentari/ canal. — Mouth situated behind brain and jirovided 

 with thick, folded lips, and a highly columnar ciliated epithelium, 

 as in the related species. Esophageal canal is extremel}' short, and 

 becomes very narrow in region of greatest thickening of inner 

 circular muscle and just before opening into the broad intestinal 

 canal, with its deep lateral diverticula. But even in this short 

 distance the esophagus is divided into two distinct chambers (PI. 

 12, fig. 76), which are clearly distinguished in the living worm. 

 The anterior chambei', or eso])hagus proper, leads directly from 

 mouth, and is opaque whitish and has a glandular aj)pearance in 

 life. It presents a distinct constriction before opening into the 

 posterior esophageal cavity, or stomach. The two chambers are 

 well marked, both anatomically and histologically, in the mounted 

 sections. 



The anterior chamber is litied with highly columnar ciliated and 

 glandular cells, the former having comparatively short cilia, and the 

 latter a rather homogeneous secretion, as described forCARiNOMELLA 

 (p. 137), while the stomach has a much thinner epithelium, with 

 fewer and longer cilia and with peculiar granules of secretions in 

 the gland cells, as is also described for Carinomella (p. 138). The 

 epithelium of both chambers is similar to that described by Miss 



