DESCRIPTIONS OF GENERA AND SPECIES 683 



MIOHAELSEN (11) J ; and, more recently still, I have been able to add to our knowledge 

 of the genus by the study of well-preserved examples of a fourth species from Lagos, 

 West Africa (39). 



Neither LEVINSEN nor MICHAELSEN were able to fix the systematic position of this 

 Annelid. My own observations have shown conclusively that it is a member of 

 the family Geoscolicidae. 



The most salient character of the genus is the possession of long penial processes 

 arising from the body at about the eighteenth segment. The function of these 

 processes is, of course, only a matter of conjecture at present ; it appears likely that 

 they serve to hold the worms together during sexual congress. These ' penes ' are 

 furnished with suckers on one surface and with modified setae arising from the bottom 

 of these pit-like suckers. These organs are richly supplied with blood-vessels, and 

 this fact led LEVINSEN to regard them as being respiratory organs as well as penes ; 

 as the structure of these processes is excessively glandular this is sufficient to account 

 for a rich vascular supply without going so far as to assign an additional function 

 to them. Underneath the epidermis with which the penis is covered by an irregular 

 layer of pyriform glandular cells with long processes which are the ducts of these 

 uni-cellular glands ; the ducts open between the epidermic cells ; the rest of the 

 penis is occupied by muscular fibres and the blood-vessels. There axe, however, a few 

 tubes which have the strongest possible resemblance to nephridia ; they are not 

 connected with the nephridia of the segment of which the penes are outgrowths. 

 The vas deferens runs in this penis ; it opens on to the exterior at about the middle 

 of the organ. As in Acanthodrilus annectens these tubes do not lie freely within 

 the body cavity, but run deep within the musculature of the body ; immediately 

 after they arise from the funnel they plunge into the thickness of the body-wall. 

 This is one of the more remarkable features in the structure of the reproductive 

 organs ; another peculiarity is the total absence of spermathecae. MICHAELSEN, who 

 was the first to point out the fact, suggests that it may have something to do with 

 the aquatic habit of the worms. He instances Criodrilus as being also devoid of 

 these pouches ; but there are, of course, many other aquatic Oligochaeta which have 

 spermathecae as well as some purely terrestrial forms which have them not. 



I have not been able to detect a clitellum in the species investigated by myself; 

 neither is there any mention of it in any other paper dealing with the genus. The 

 example of Moniligaster teaches us to be careful in asserting the absence of this 

 characteristic Oligochaetous organ ; otherwise it might be suggested that the presence 

 of the long penes would render the function of a clitellum rather difficult, and that 



1 I have not incorporated MICHAELSEN 's latest paper (161. 

 4 S 2 



