826 MR. F. E. BKDDARD ON [NoV. 3, 



Megnscolex, and which undoubtedly occurs in other ERithwnrms, 

 coupled with their absolute independence of the vas-deferens funnels, 

 is, I think, sufficient to show that my determination is correct. 



The vasa deferentia, instead of uniting to form a single tube, as 

 appears to be the case in the majority of Earthworms, remain 

 obviously distinct from each other for the whole of their course ; 

 they pass down close to tiie ventral pair of setae, but to the outside 

 of them, and in certain regions, at any rate, are not very firmly fixed 

 to the body-wall ; their walls are supplied with abundant blood- 

 capillaries. On referring to Perrier's description of the anatomy of 

 Acanthorlrilus, I find that he figures the vasa deferentia in A. 

 urujulatus ' as being composed of two widely separated tubes. 



The prostate glands are two pairs, each connected with one of 

 tlie four male genital apertures ; each consists of a thick-walled 

 glandular tube variously coiled upon itself, and terminating in a 

 narrow muscular duct which has a nacreous glitter. In A. multiporus 

 (PI. LIII. fig. 2) the mesenteries in the neighbourhood of the pro- 

 states are arranged in a somewhat radiating fashion as bands of 

 nacreous-looking fibres, which are attached at one extremity to the 

 ventral body-wall, close to the apertures of the prostate ; they 

 perhaps serve as special " cremaster " muscles. With each of the 

 male generative apertures is connected a thin-walled muscular sac 

 containing a number of long penial setse, hooked at their extremity, 

 but not ornamented in the way that is often found in Acanthodrilus. 

 There is therefore nothing remarkable in the male generative 

 system of this species, except in the fact that the apertures are situ- 

 ated within the clitellum instead of behind it ; it is, with the 

 exception of this relation of its aperture to the clitellum, precisely 

 similar to the male generative system of other Acanthodrili, even to 

 the numbers of the segments on which the vasa deferentia open. If 

 systematists are unwilling to include this species within the genus 

 Acanthodrilus, it cannot, at any rate, be placed far from it, certainly 

 not in a distinct group. 



In describing the external characters of these worms, it should 

 have been mentioned that the male apertures are situated upon the 

 summits of conspicuous papillae ; transverse sections through this 

 region of the body-wall show that the papillae are the result of the 

 more elongated form of the epidermic cell surrounding the apertures 

 of the generative ducts; the cells which cover the papillae are from 

 three to four times the length of the cells that are found elsewhere, 

 but are similar to them in their structural characters. In A. dissi- 

 milis the duct of the prostate gland comes into close relation with 

 the genital setae ; the latter are of course homologous with the 

 ordinary locomotor setae, and simply replace them upon the genital 

 segments. 



Each of the two genital setee corresponding to each genital 

 aperture is contained in a separate sac, which is lined by a continua- 

 tion of the epidermis, and communicates with the exterior by a 

 se])arate orifice. There are of course numerous accessory setae, which 



' Loc. cit. pi. ii. fig. 18. 



