452 Illinois State Laboratory of Natural History. 



diameter of the body, after a short course, empty into the 

 ventral vein." 



Figure 9 of Plate II in Stoic's paper is a diagrammatic 

 representation of the circulatory system in the anterior part 

 of I. coccineus. Through some typographical error that part 

 of the description of plates dealing with this figure is headed 

 Bothrioneuron vejdovskyanum, and is thus somewhat confus- 

 ing. A comparison of this figure with that of the correspond- 

 ing organs of Vermiculus jiilosus (Goodrich '95, PI. XXVI., 

 Fig. 5) and Hhizodrilus lacteus (PI. XL., Fig. 8) will readily 

 suggest a common derivation for the different types. For 

 convenience in making such comparison Figures 9 and 10 of 

 Plate XL. have been prepared from the figures by Goodrich 

 and Stole. 



Embolocephalus mtdtisetosus n. sp. 



AVorms of a species of Tubificidce not hitherto described 

 are found in great abundance in the vegetable debris at the 

 bottom of Flag Lake, and are occasionally met with in the 

 vegetation along the banks of the Illinois River and the bot- 

 tom-land lakes in the vicinity of Havana. 



Well-extended individuals are 19 to 35 mm. in length. At 

 the time of sexual activity a few somites at the anterior end, 

 including the reproductive organs, are much enlarged, the 

 diameter of the worm in this region being then two and a half 

 or three times that of the remainder of the worm. In a rather 

 large specimen the diameter in the region of the tenth somite 

 is .8 mm., that of the middle of the worm is .3 mm., and at a 

 distance from the posterior end equal to one fourth the length 

 of the body the diameter is .2 mm. The number of somites 

 varies from 49 to 106 in specimens examined, but 75 to 80 

 is more common. The main part of the body is of a dark 

 grayish color, but the posterior end-is lighter and less opaque. 

 A sheath formed in part of foreign particles cemented together 

 envelops the anterior part of the body, making it quite opaque. 

 It adheres very closely to the surface of the worm and is 

 removed with great difficulty. It is wanting in the posterior 

 part of the body, which is extended into the open water and 



