Species of North American Oligochceta. 403 



The ventral half of the wall is very thin and without 

 cilia. In somite V the walls of the alimentary tract 

 become nearly uniform in thickness and ciliated through- 

 out. The lumen in this somite is quite narrow. In the 

 following- somites the intestine is sacculated. Beginning 

 with the seventh somite it is invested by a nearly con- 

 tinuous sheath of blood, outside of which is the layer of 

 chlorag'ogue cells. The muscles connecting the pharynx 

 with the body wall are very weak and few in number 

 (Fig. 11). There is no glandular tissue forming pharyn- 

 geal and septal glands. There is a similar absence of 

 such glands in Eclipidrilus frigldus Eisen ('95, Eisen, 

 p. 86). A few deeply-staining cells are situated on some 

 of the blood vessels of the region, but none upon the 

 pharyngeal muscles. 



My knowledge of the circulatory system of this species 

 is very imperfect, owing chiefly to lack of opportunity 

 for studying the worms in the living state. The ventral 

 vessel is forked near the septum V | VI. None of the vas- 

 cular trunks connecting the dorsal and ventral vessels 

 are especially enlarged. In the anterior part of each of 

 a few of the anterior somites a pair of vessels invested 

 by gland cells connects the ventral vessel with the dor- 

 sal part of the intestinal sinus; while in the posterior 

 part of the somite a pair of slender vessels without in- 

 vesting gland cells and having a somewhat tortuous 

 course connects the dorsal and ventral vessels. " pair 

 of these connecting vessels from somite X extends back- 

 ward through several somites, being closely associated 

 with the reproductive oi-gans contained therein. In the 

 posterior part of the worm there are two pairs of lat- 

 eral vessels in each somite; one situated anteriorly, the 

 other, posteriorly. Both paii's branch off from the dor- 

 sal vessel, from which they extend laterad, each vessel 

 closely following the body wall. They are similarly in- 

 vested by gland cells, and have short creeal diverticula, 

 but the vessels of the posterior pair, unlike the anterior, 

 unite with the ventral vessel. 



