Illinois Oligochceta. 451 



the blood is conducted to the ventral vessel through two pairs 

 of vessels in each somite, of which the posterior pair is the 

 larger. In V. limosus, recently described from Japan by 

 Hatai('98, p. 110), the same general relation exists between 

 these lateral vessels and the body wall, except that there is 

 but one pair of lateral branches of the ventral vessel in each 

 of the somites referred to, and that there is a slight differ- 

 ence in the number of somites in which such vessels occur. 

 Goodrich ('95, p. 262) regarded this condition of the circu- 

 latory system as distinguishing' Vermiculus from all other 

 Tubificidte. The circulatory system of Ilyodrilus coccineus, 

 as described and figured by Stole ('88, p. 15, Tab. II., Fig. 9), 

 seems to constitute a very interesting mtermediate type 

 between that of Vermiculus and such forms as Bhizodrilus. 

 As Stoic's paper is unfortunately written in Czech, it has 

 been inaccessible to most students of the Oligochceta. 

 Through Mr. L. F. Miskovsky, of Oberlin College, I have 

 been so fortunate as to obtain a very careful translation of 

 this admirable paper, and quote here that part which treats 

 of the vascular arches of Ilyodrilus. 



"In the following segments, i. e., in the fourth to the ninth 

 inclusive, the dorsal artery is united with the ventral always 

 through one pair only of lateral arteries, which issue before 

 the posterior septum of each somite from the dorsal artery 

 and gradually swell behind until in the last three of the 

 named segments they assume the largest proportions, resem- 

 bling thus the swelled lateral arteries (so-called hearts) which 

 are found in the remaining genera of the Tubificida. The 

 lateral arteries here described do not, however, open simply 

 into the ventral artery. Each one of the lateral arteries 

 approaches closely to the lateral diameter of the body and 

 sends several branches into the integument. The branches 

 running through the integument form in each segment an 

 elegant vascular network which is connected through numer- 

 ous anastomoses with the plexuses of the other segments. 

 The sanguineous fluid after coursing through this integument- 

 ary network returns into the ventral vein through two special 

 veins, which, issuing out of the integument from the lateral 



