Chaetoptei'us Variopedatus. 493 



The Digestive Tract. — The digestive tract of the adult Chsetop- 

 tenis forais a comparatively straight tube except in the middle region 

 of the body where it forms several convolutions. Its greatest diam- 

 eter is reached in the middle of the body, but in the posterior region 

 it diminishes slightly in calibre. 



The large mouth and broad buccal funnel have been described 

 as being located at the anterior end of the anterior region. At the 

 inner end of its dorsal lip the mouth communicates with a tubular 

 esophagus which is usually flattened from right and left sides so 

 that, in sections, its lateral walls lie parallel and nearly touch one 

 another. The flattening is produced chiefly by the presence of the 

 muscular partitions of the setigerous segments. The flattened esoph- 

 agus occupies nearly the whole dorso-ventral space within the 

 anterior portion of the anterior region (Fig. 15). Throughout the 

 posterior portion of this region it is circular or elliptical in trans- 

 verse sections. Posteriorly, and in the vicinity of the ninth setigerous 

 segment, the esophagus becomes dilated considerably so that it 

 becomes tubular. Here it becomes differentiated into a glandular 

 and a ciliated epithelium (Fig. 16). The epithelium of the ventral 

 half of the esophagus consists of tall, ciliated columnar cells whose 

 nuclei lie at their free ends. In this respect the cells are like those 

 in the middle and fore parts of the esophagus and the buccal funnel. 

 In its dorsal half the epithelium of the esophag-us is thrown into 

 folds. Many of its cells are glandular. The nuclei are located 

 toward their proximal ends. The glandular portion begins in the 

 dorsal wall of the esophagus immediately back of the ninth setigerous 

 segment as a small group of cells. It gi-adually spreads out so that 

 it occupies the dorsal half of the esophagus (Fig. 17) at a point 

 midway between the posterior border of the ninth setigerous seg- 

 ment (eleventh of the anterior region) and an imaginary line 

 joining the bases of the notopodia of the twelfth segment 

 (first of the middle region). Immediately anterior to the bases of 

 these notopodia the glandular portion ends blindly as a small cylin- 

 drical sac which lies dorsal to and parallel with the esophagus (Fig. 

 18). Within the lumen of the glandular portion, whose length is 

 about equal to that of the cylindrical fsecal masses discharged by the 



