1917.] Fauna of the Chilka Lake : Oligochaeta. 489 



The abnormal position of the dorsal vessel is not mentioned by either author ; it 

 is shown lying against the side of the intestine in Moore's figure. It is said to be on 

 the right side in M. limosus by Nomura (7). 



Ditlevsen implies, and his figure shows, that the two male ducts do not unite 

 before entering the spermiducal chamber ; nor is there any reference to the widening 

 to the duct which I have called the atrial chamber; this latter,, however, is visible in 

 the figure. 



There can, I think, be little doubt that Moore's specimens are specifically identi- 

 cal with those here described ; but I am inclined to agree with him that further infor- 

 mation may necessitate a separation between Ditlevsen' s worm and his own. As to 

 the generic name that should be employed; Benham (1, 2), uniting Rhizodrilus and 

 M ' onopylephorus , uses the former; Michaelsen (5), while accepting the union, prefers 

 the name M onopylephorus ; Nomura (7) gives reasons for retaining the two genera as 

 distinct. A revision of all the forms described under these two names is, as Michael- 

 sen says (loc. cit.), required, along with that of related genera ; for the present the 

 most convenient course seems to be to retain the name under which the worm has 

 already twice been described. 



A thorough revision would also probably indicate the homologies of the various 

 parts of the male efferent apparatus with the successive segments of the tube in other 

 genera. At present there is an extraordinary amount of confusion : Ditlevsen calls 

 the whole tube, from the funnel to its termination in the median pit on the ventral 

 surface, " Samenleiter " (=vas deferens); the pit itself, following Goodrich, he 

 names " spermiducal chamber " (using the English words). Moore uses the term 

 " sperm reservoir" for the portion of the duct which is covered by high peritoneal 

 cells, "ejaculatory duct " for the short succeeding portion, and " median bursa" for 

 the pit on the surface ; the term " penis sac " is employed for the dilatation which I 

 have called f ' atrial chamber." There is, however, no such dilatation of the " sperm 

 reservoir" as would lead one to suppose that it is capable of acting as such, nor did 

 I find spermatozoa in this portion of the duct; while the epithelium of the " penis 

 sac" is so high that the passage would be altogether obliterated by the eversion or 

 even by any considerable protrusion of the terminal portion of the apparatus ; the 

 utmost that could happen, apparently, would be some slight protrusion of the papilla 

 on the roof of the " median bursa," sufficient, perhaps, to bring this level with the 

 surface of the body. Nomura, in describing M. limosus, uses the term " atrium " for 

 the portion of the duct which is covered by high peritoneal cells, " atrial duct " for 

 the short portion which succeeds, and "lateral horn of the spermiducal chamber ' ' for 

 what I have called the "atrial chamber." Michaelsen, in M. africanus, includes 

 under the term l( atrium " the atrial duct of Nomura ; in this species there is appar- 

 ently no separate ff atrial chamber,' ' the upper part of the deep li Kopulationstasche' ' 

 (spermiducal chamber, median bursa) representing the united atrial chambers of such 

 forms as M. parvus, glaber, limosus, etc. ; but on other grounds (spermathecae in seg- 

 ment ix, presence of penial setae) it seems probable that M. africanus ought to be 

 considered as belonging to another genus. Most authors seem to confine the term 



