Illinois Oligochteta. 449 



dorsad of a line connecting the ventral bundles of one side. 

 The interval between the two spermathecal pores is about 

 one fourth of the circumference of the body. The sperma- 

 tozoa in the sperm athecae are present in loose masses. No 

 signs of spermatophores have as yet been found. 



A pair of elongate tubular glands is present in IX, their 

 openings being in close relation to the peculiar genital setae 

 of that somite (PI. XL., Fig. 6). In the specimen previously 

 referred to as having genital setae on X similar to those on 

 IX, a pair of such glands is also present in X, having similar 

 relations to the setae of the somite. These glands are about 

 equal in length to the somite, and their diameter, which is 

 nearly uniform throughout their length, is about one eighth 

 the diameter of the somite. The diameter of the lumen is 

 about .01 mm. and the walls are .03 mm. in thickness. The 

 wall consists of two layers of cells, the outermost being very 

 thin and composed of flattened epithelial cells, while the 

 inner layer is formed of relatively large glandular cells, 

 largest at their distal ends, in which the nucleus is com- 

 monly situated. The openings of these glands and the asso- 

 ciated setae are on prominent rounded elevations of the ventral 

 wall of the somite (PI. XL., Fig. 6) and in line with the ventral 

 setae of adjacent somites. On the summit of these elevations 

 the hypodermis is modified as it is in the genital papilla' of 

 some earthworms ; for example, Diplocardia and Allolobophora. 



For the sake of greater convenience in the comparison of 

 11. lacteus with other forms Igive the following summary of 

 its more important characters : 



The number of somites is 215-365. 



All the setae are uncinate except the genital ones, which are 

 of two kinds, one form in IX and the other in XI. 



The clitellum extends from the middle of X to the posterior 

 part of XII. 



Coelomic corpuscles are very numerous. 



Supra- and sub-intestinal vessels are wanting, and the 

 lateral vessels or "hearts," which connect the dorsal and ven- 

 tral vessels in VII-X, are enlarged, nearly uniform in size, 

 and do not give off branches to the body Avail. 



