Walter Ritchie 317 



Just where this tube which forms the attachment between the two 

 halves of the testis enters the more posterior body, another longer tube 

 arises from the cavity. This tube is the vas deferens (vd). Each vas 

 deferens is at first a narrow tube, which later swells out and ultimately 

 unites with the vas deferens of the other testis, to form the common or 

 ejaculatory duct (cd), leading to the internal sac (is) and the median 

 lobe (ml). 



This attachment of the glandular bodies of the testes is most in- 

 teresting, as it would seem to indicate that the sperms produced in the 

 more anterior body would have to pass through a part of the other body 

 at least, before entering the vas deferens. 



At the point where each vas deferens begins to swell out, the duct of 

 the accessory gland (ag) opens into it. This gland, at its beginning, is 

 much convoluted and ends blindly. A little further along each, vas 

 deferens, another tube, the seminal vesicle (sv) opens into it. This tube 

 at its beginning is narrow; but for about a third of its length, prior to 

 entering the vas deferens, it is much swollen and usually coils twice. 



The common or ejaculatory duct (cd), at first a fairly wide tube, 

 becomes more delicate and at last becomes hidden to view, ensheathed 

 in a wide membranous tube (st) which is attached by muscles to the dorsal 

 anterior surface of the median lobe (ml). In its course the common duct 

 (cd) passes from the ventral side of the abdomen to the dorsal, and after 

 passing through the ensheathing membranous tube (st), empties itself 

 into the internal sac (is). 



Passing into the membranous tube along with the common duct are 

 two bundles of tracheae, which, later, enter the internal sac over the 

 surface of which they ramify. 



The internal sac into which the common duct empties itself is at first 

 a much swollen tube, but latterly it thins out and enters the chitinous 

 median lobe (ml) through the median foramen (Fig. 18 a, mf), terminating 

 at the median orifice (mo) (see Figs. 16 a and 18 d). 



The membranous tube (st) ensheathing the ejaculatory or common 

 duct, and the internal sac, do not lead straight to the median orifice but 

 bend several times in their course. The course of the internal sac with 

 its various bends can be followed in Fig. 16 a. 



At several points on the inner (external when exserted in the act 

 of copulation) walls of the internal sac there are present chitinous 

 structures which form the armature (see Fig. 16). On the swollen portion 

 of the internal sac, i.e. between the termination of the membranous tube 

 ensheathing the common duct and the first bend on the sac, there are 



Ann. Biol, vn 21 



