1887.] ANATOMY OF EARTHWORMS. .383 



well-developed muscular coat (fig. 11, i) ; the lining epithelium is 

 ciliated throughout. 



The terminal apparatus of the male generative system in Eudrilus 

 is extremely unlike what is found in other Earthworms. It has been 

 already partly described by Perrier and by myself; but these 

 descriptions refer only to the rough anatomy of the organs, and not 

 to the minute structure. With regard to one point there is some 

 discrepancy between Perrier's account and my own, and that is the 

 termination of the vasa deferentia. These tubes, as already stated, 

 are remarkable for the fact that they possess a thick muscular coat, 

 which is wanting in the vasa deferentia of other Earthworms ; the 

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

 do in the majority of Lumbricidse (in all except AcanthodrVus), 

 remain distinct and open separately into the terminal region of the 

 prostate gland, M. Perrier has figured {I. c. pi. ii. fig. 26, a) a single 

 vas deferens opening into the muscular sac of the penis in Eudrilus 

 decipiens ; and there are no statements in his paper which would lead 

 to the inference that in the two other species there was a difference 

 in respect of these organs. Towards their distal extremity the vasa 

 deferentia increase notably in diameter {cf. figs. 1, 16). 



In Eudrilus boyeri I found the important difference in the vasa 

 deferentia and in their relation to the terminal apparatus that has 

 been just referred to, and which is fully described and figured in my 

 paper upon that species; and I am now in a position to state that in 

 Eudrilus sylvicola the arrangement of these organs is precisely similar. 

 This fact renders it probable, in my opinion, that the structure of 

 the terminal apparatus of the male sexual organs in Eudrilus gene- 

 rally is closely similar to that of E. sylvicola, which is now to be 

 described in detail. 



On opening the body of the worm the conspicuous prostate glands 

 are to be seen, which extend back from their opening into the bursa 

 copulatrix of the 17th segment for some way. M. Perrier rightly 

 points out the nacreous appearance of this organ, which only resembles 

 the prostate gland of other Lumbricidae by its position : — " mais qui 

 ne presente en aucune fa90u I'aspect glandulaire de ces dernieres." 

 An investigation of the structure ot this sausage-shaped body 

 shows very plainly that it is of a glandular nature and that it 

 resembles in many points the prostate glands of other Earth vAorms. 

 The glandular nature of the organ is, however, masked by the very 

 great development of its muscular layers, which give to it the pecu- 

 liar nacreous appearance which is so characteristic. A study of the 

 organ by means of transverse sections (see Plate XXXIII., fig. 13) 

 shows that these muscular layers together form a coat of very 

 considerable thickness ; by far the greater part is occupied by the 

 longitudinal fibres, the transverse fibres forming a very delicate 

 layer within these. The glandular tissue of the organ is di\-ided 

 into two layers, which agree very closely in structure with the 

 prostate glands of Acanthodrilus, and also present an unmistak- 

 able resemblance to the epidermis of the clitellum. The inner row 

 of cells which surround the lumen of the gland are narrow, elon- 



26* 



