1907.] NATURAL SCIENCES OF PHILADELPHIA. 119 



The intestine (fig^5. 7 and 8, int.) takes its rise from the posterior 

 portion of the stomach, dorsad of the median axis of the animal, whence 

 it runs caudad to the anus in a nearly straight course, with but a slight 

 sigmoid flexure. Like the stomach and oesophagus, it is lined through- 

 out its course with long cilia. The anus, as already described, opens 

 at the posterior termination of the trunk, just dorsad of the caudal 

 process. The outer diameter of the intestine in its middle portion 

 is about one-half of that of the stomach, but is contracted both at its 

 junction with the stomach and at the anus. The intestinal wall is 

 approximately 3 /.i in thickness and composed of a single layer of cells 

 which vary much in form, from a flattened squamous type to the 

 cubical. This irregularity in the form of the constituent cells of the 

 intestinal wall is associated with an irregularity in the contour of its 

 inner surface, the latter being raised into numerous longitudinal ridges 

 rather irregularly arranged, most numerous and attaining their gi*eat- 

 est height midway between stomach and anus, and disappearing near 

 the two latter points. The cells themselves present the same cyto- 

 logical characters as those of the oesophagus, namely, a thin cuticle, a 

 narrow subcuticular border, a layer of end knobs, from which arise 

 the long cilia, and a clear and transparent cytoplasm, enclosing an 

 ovoid nucleus with a karyosome. 



The musculature of the alimentary canal is very slight, aside from 

 that of the proboscis and the few fibres which accompan}^ the preoral 

 transverse commissure. The latter are to be reckoned with those of 

 the alimentary canal, since they serve to draw together the lateral 

 halves of the mouth. No traces were found of the radiall}' arranged 

 muscles about the mouth described by Korschelt (1882). The largest 

 and most evident muscles are comprised in two small groups, one on 

 either side of the A-ertical limb of the oesophagus, passing from its 

 lateral walls to the body wall on either side (fig. 3, (rs.m.). These 

 serve, as do similar muscles in annelids and other forms, to dilate the 

 oesophagus. A iew muscle fibres encircle the oesophagus at irregular 

 intervals, and are only visible in longitudinal sections, where they 

 appear as black points on the outer surface of the oesophageal wall. 

 Some of these are represented in fig. 23. It is possible that such 

 fibres are present also on the stomach and intestines, but I have not 

 been able to satisfy myself of their presence. There is however, 

 encircling the posterior end of the intestine a very short distance 

 anterior to the anus, a muscle composed of one fibre, which thus 

 serves as a sphincter ani (fig. 8, int.m.). 



The glands occurring in the epithelium of the alimentary canal have 



