446 Illinois State Lahnroforif of Natund History. 



The pharynx extends through somites II and III, and its 

 dorsal and ventral walls are of about equal thickness. The 

 oesophagus extends backwards into VI, where the epithelium 

 gradually assumes the character of that of the intestine. In 

 VII the alimentary tract increases in diameter, and the intes- 

 tine may be regarded as commencing in that somite. Septal 

 glands are present in IV and V, those of the latter somite 

 being the smaller. Coelomic corpuscles are very numerous 

 in the ccelomic spaces not otherwise filled. They are spherical 

 and mostly without granular contents, although some contain 

 a few rather large spherical granular bodies. 



The circulatory system cannot be studied in the living 

 worm because of the opacity due to the numerous corpuscles, 

 and our knowledge of it is chiefly derived from a study of 

 transverse and longitudinal sections. The dorsal and ventral 

 vessels do not divide in the anterior region of the body to 

 form supra- and sub-intestinal trunks. In the posterior part 

 of each of somites VII-X a pair of large lateral vessels, or 

 "hearts," is present, connecting the dorsal and ventral ves- 

 sels directly, without giving off branches to the body wall as 

 is the case in Ilijodrilus. These vessels are approximately 

 equal in the somites mentioned. The diameter of the lateral 

 vessels of VI is only about one fifth as great as that of the 

 corresponding vessels of VII. 



The nephridia have been studied with reference to charac- 

 ter and arrangement in but three individuals, and in these 

 only in the anterior twenty somites. These organs first 

 appear in VIII, but in VIII, IX, and somites posterior to XI 

 only one nephridium is present in each somite, and that is in 

 the left side of the body in all cases observed. In sexually 

 mature individuals nephridia are absent in X and XL The 

 ventral vessel lies in the left side of the body, and is closely 

 invested by the expanded glandular part of each nephridium, 

 the relation between them being much like that described by 

 Goodrich as existing in J^erDiiculus pi'l-osus ('95, p. 258). 

 The nephridium enlarges almost immediately behind the 

 anterior septum, forming a mass of considerable size, through 

 which the duct passes in a tortuous course, finally leaving the 



