210 PROF. W. B. BENHAM ON AQUATIC [ISToV. 3, 



The clitellum envelops the body, and extends over three seg- 

 ments, from the middle of x. to the middle of xiii, (PI. XXIV. 

 fig. 1). 



The male pores are near the posterior margin of segment xi. and 

 lie outside the line of ventral chsetaj, which in this segment are 

 modified to form a bundle of copulatory bristles. 



The oviducal pore is at the anterior margin of segment xii., 

 practically intersegmental, and further laterad than the male 

 pores. 



The spermathecal pores are close to the anterior boundary of 

 segment x. 



Internal Anatomy. 



The pharynx, in segment iii., is provided with the usual dorsal, 

 ciliated pouch, wdience radiating muscles pass to the body-wall. 

 The oesophagus is quite narrow ; the chloragogen cells begin in 

 segment vi. ; the gut suddenly enlarges in the tenth segment, 

 and food occtirs there consisting, amongst other things, of diatom- 

 valves ; this intestinal region is thereafter wide, but septally 

 constricted. 



The Vascular System. — The dorsal vessel is distinct throughout 

 the body ; it is connected with the ventral vessel by undulating 

 commissurals in each of the segments ii. to x., while the dorsal 

 vessel bifurcates in the first segment, and each branch passes 

 forwards into the prostomium, bends downwards and backwards to 

 unite to form the ventral vessel in segment ii. 



Of the commissxu-al vessels, those in segments vii. and viii. are 

 slightly larger and less extended than the rest ; they, however, 

 are not dilated to form " hearts " such as occur in Limnodrilus 

 and other Tubificids (PI. XXIY. fig. 2). A pair of vessels passes 

 backwards on the sperm-sacs to segment xvii., but as to the exact 

 origin of them, or whether there is a second pair supplying the 

 ovisacs (as in Branchiura coccinea), I am unable to ascertain. 

 Nor can I state whether any of the commissurals connect with 

 the supra-intestinal vessel which is present in at least part of this 

 region. I have not been able to detect any integumental vessels, 

 either in sections, or in the glycerine and potash preparations. I 

 do not think they exist. 



Ihe, Reproductive System (P\. XXIV. fig. 8). — The testes, ovary, 

 and oviducts are in the positions usual in this family. 



There are two pairs of sperm-sacs, one in segment ix., the other 

 extending through segments xi. to xvii. and constricted by each 

 septum through which it passes, while segment x. is filled with loose 

 masses of developing spermatozoa, not enclosed in a special sac. 

 Large ova, contained in an ovisac, occupy segments xvi., xvii., 

 xviii., in one specimen ; but in another, in which the sperm-sacs 

 are not so extended, the ovisac is not so far back. 



The condition of the male efierent apparatus is the most 

 interesting feature of this new genus. 



The sperm-funnel, on the hinder wall of segment xi., is flat and 



