hhpokt on the oll(;ocileta — hexham. 261 



Intehxal Anatomy : — 



Rpjirodnctlvi' St/stem. — The structure of the male efferent 

 Hj)paratus is very peculiar. A pair of testes lies in segment xi., 

 on the anterior septum ; the sperm funnel is simple, and the 

 sperm duct after piercing the septum xi./xii., passes hackwards in 

 a .slightly undulating course on the mesial side of a large muscular 

 sac, into the neck of which it opens (PL xlvii., lig. 15). 



The muscular sac in segment xii. was very conspicuous in the 

 t'ntire specimen, as it is filled with ripe spermatozoa. It is nearly 

 cylindrical, l)ut curved, so that it is convex dorsally ; its rounded 

 free extremity is directed forwards and rests close hehind the 

 septum xi./xii., while posteriorly, after curving downwards as it 

 approaches the middle of the segment, hecomes rather narrowei-, 

 to form a short " neck." This now opens into a small, suh- 

 spherical chamber through its mesial wall. This cliamber, which 

 may be termed the " penial chamber,"' in its turn cKinmunicates 

 with the exterior by a comparatively small pore on the ventral 

 surface of segment xii. (PI. xlvii., fig. 14). 



The structure of these parts is as follows: — The "muscular sac" 

 is lined by a fiat epithelium, in which nuclei can only be distin- 

 guislied here and there, surrounded by a thick coat of circular 

 muscle-fibres (PL xlvii., fig. 16). There is no glandular 

 covering, and no gland opening into this sac. The 

 sperm duct has the usual structure, and opens into the 

 narrow neck of the preceding near tlie (jpening of tlie 

 latter into the "penial chamber" (PL xlvii., fig. 15). Tlie 

 short " common duct " thus formed does not differ in 

 structure from the rest of the sac. At the point of entrance of 

 the sperm duct, the cilia project into the sac (PL xlvii., fig. 16). 

 The subspherical " penial chamber" appears to be a,n invagination 

 of the epidermis, it is lined by an epithelium, which over the 

 greater part of the outer hemisphere is similar to tiie epidermis, 

 but the wiiole of the mesial surface of the wall, as well as the 

 apex and part of the outer wall, is lined by a layer of tall glandu- 

 lar cells (PL xlvii., fig. 17). The wall is, fui'ther, provided with a 

 thin coat of circular and longitudinal muscles, as well as " retractor 

 nmscles " connected with the body wall. The structui-e of this 

 chamber suggests that it is capable of protrusion, and on one side 

 of the body, the common duct (or neck of the muscular sac) is it- 

 self pushed forward into tlie cavity of the " penial chamber " (PL 

 xlvii., fig. 17) in such a way as to suggest a " penis " such as 

 exists in some species of Phreodril its (P. albus, P. lacuxtris), but of 

 much smaller dimensions. 



In segments xi. and xii. are masses of developing spermatozoa ; 

 the former segment is filled by them, the latter only partly so. 



