4B0 Illi)iois State LnJinratorii <if Nutural History. 



basis of this description show uniformity throughout in the 

 position of the various reproductive organs. 



There are four pairs of setae in each of the setigerous 

 somites, the interval between the dorsal and ventral bundles 

 of one side of a somite being five sevenths as great as that 

 between the two ventral bundles and one half as great as that 

 between the two dorsal bundles of the same somite. The 

 setffi are of the ordinary sigmoid form, without a cleft at the 

 outer extremity, and are somewhat variable in length, but 

 average about .2 mm. There are no genital settt. 



The brain consists of two lateral masses, each with its 

 longest axis dorso-ventral, the two being connected by a stout 

 fibrous commissure. The surface layer of each mass, except 

 in the ventral region, consists of a thick layer of nerve cells. 

 The commissures extending to the ventral cord and the large 

 nerve trunks leading to the prostomium are given off from 

 the ventral side of the lateral masses. 



No marked peculiarities have been noticed in the alimentary 

 tract. There is a gradual transition from pharynx to intestine 

 without any well-marked intermediate ctsophagus. The 

 anterior part of the pharynx is capacious, with a dorso- 

 ventral diameter considerably greater than the lateral one. 

 The ventral wall of the pharynx is quite thin, while a thick 

 glandular wall extends over the dorsal, and somewhat more 

 than half over the lateral, region. Toward the posterior 

 part of the pharynx the dorso-ventral diameter decreases, as 

 does also the extent of the thin ventral wall, and in the 

 anterior part of IV the walls are uniform in thickness and 

 circular in outline. The thickened part of the pharyngeal 

 wall is ciliated. Chloragogue cells first appear in the sixth 

 somite. There are no pharyngeal glands, but there are a 

 few deeply staining cells on some of the muscular strands in 

 a few anterior somites. On the anterior face of septum 

 VI/VII and on both faces of septum VII/YIII are borne 

 rather small masses of cells which do not stain very deeply. 

 They may correspond to the septal glands of some OligocJueta. 

 In that part of the body containing the reproductive organs 

 the lateral diameter of the intestine is greatly reduced (PI. 



