24 BULLETIN: MUSEUM OF COMPAKATIVE ZOOLOGY. 



ing of the latter, and in some species both these openings are 

 united in a broad atriura. Usually, however, the esophagus branches 

 out directly from the ventral wall of the rhynchodaeum. 



From its point of origin, which may be near the tip of the snout 

 or back nearly to the brain, the esophagus passes posteriorly as a 

 narrow tube beneath the ventral brain commissure, behind which it 

 abruptly enlarges into a broad chamber, the stomach (Text-fig. G). 

 The epithelium of the esophagus is thin and composed mainly of 

 ciliated cells, although gland cells also occur in comparatively small 

 numbers. The ciliated cells are covered with closely placed but 

 short cilia. 



Stomach. — The stomach (Text-figs. 8, 6, 15, 16, 17, 19), situated 

 immediately behind the brain, is broad, with greatly convoluted walls 

 and lined with a thick layer of ciliated and glandidar epithelium very 

 similar to that described for the heteronemerteans. Posteriorly the 

 stomach continues into a long narrow tube, the pylorus, situated 

 immediately ventral to the proboscis sheath. 



Pylorus. — This tube (PL 20, fig. 121) does not open into the 

 anterior end of the intestine, or mid gut, but passes a considerable 

 distance backward and opens through the dorsal wall of the intes- 

 tine, often far back of its anterior end. The anterior portion of 

 the intestine, therefore, extends forward beneath the pylorus and 

 ends blindly anteriorly, forming the intestinal caecum. The histo- 

 logical features of the pylorus resemble those of the stomach except 

 that the epithelial cells are shorter and consist of a much larger pro- 

 portion of ciliated cells, the gland cells almost disappearing at its 

 posterior end. 



Intestine. — The broad intestinal canal is provided with deep 

 lateral pouches and with histological elements very much like those 

 described for the Heteronemertea. 



Intestinal caecum. — The blind portion of the intestine extending 

 forward beneath the pylorus exhibits the same morphological and 

 histological structure as the intestine proper. In many species of 

 Amphiporus and in other genera the caecum extends anteriorly 

 beneath the stomach, and its pouches often reach as far forward as 

 the dorsal border of the brain lobes. The lateral pouches of the 

 caecum (PI. 20, fig. 121) are usually more slender than those of the 

 intestine proper and extend laterally in the parenchyma beside the 

 pylorus and proboscis sheath and above the lateral nerves. They 



