16 MR FRANK E. BEDDARD ON THE 



peritoneal in nature ; at first, as Bergh has shown, the spermatheca consists only of an 

 ingrowth of epidermis with a peritoneal layer, somewhat thickened, lying outside it ; out of 

 this latter are formed the muscles as well as the peritoneal layer of the mature sper- 

 matheca ; it does not, therefore, follow that a distinct peritoneal epithelium separates 

 from the ccelom structures which have had an ectodermic origin. Reference may also be 

 made to the description of the immature atrium of Moniligaster contained in this paper. 

 I am therefore not yet convinced that the glandular cells packed among the muscles in 

 the atrium of Desmogaster are to be looked upon as part of the lining epithelium. 



As to the position of the testes and ovaries, this point of difference must apparently 

 be dropped, now that we have Rosa's genus Desmogaster added to the Moniligastridse ; 

 the position of the gonads and of the other parts of the female apparatus is quite normal 

 in Desmogaster. But we have still the remarkable fact that the vasa deferentia open on 

 to the segment next to that which contains their internal aperture ; even when they are 

 doubled this takes place. The double condition may perhaps be regarded as the older, 

 as it occurs in most Oligochseta, though not to so complete an extent as in Desmogaster. 

 Dr Rosa, however, is not correct in implying, as I understand him (p. 369), that two 

 external pairs of apertures is a unique feature ; the same occurs in Phreoryctes, the atria 

 having almost completely vanished ; and Phreoryctes is certainly not an "Earthworm," 

 though it is, as I have pointed out, hardly excluded from that group by Rosa's definition. 



Dr Rosa admits the great peculiarity of the sperm sacs in the Moniligastridse, upon 

 which I have omitted to lay sufficient stress in this paper. The remarkable way in which 

 the sperm sac is, as it were, suspended in the middle of the dissepiment is unlike any- 

 thing that occurs in any earthworm, though certainly not leading towards any condition 

 observable in the " Limicolse." 



It is, moreover, impossible in sections of M. Bamvelli to state with any certainty 

 which segment the sperm sacs belong to ; in Desmogaster Rosa's figure indicates the same 

 difficulty. 



The remarkable partial obliteration of a segment (the XHIth) which Michaelsen 

 has lately described in Nemertodrilus griseus, suggest that something of the same kind 

 may have occurred in the Moniligastridse, the supposed sperm sacs may be all that is 

 left of the calom belonging to the segment which contains the testes. This is of course 

 no more than a suggestion ; but the varying position of essential organs in the Oligochseta 

 requires, as I point out in a forthcoming number of the Quarterly Journal of Micro- 

 scopical Science, some possibility of the intercalation or excalation of segments at the 

 head end. 



This suggestion is supported by the absence of trabeculse in the sperm sacs of Monili- 

 gaster and Desmogaster.* 



The correspondence between external and internal metamerism in Desmogaster is 

 a little difficult to follow ; between the last thickened septum and the dissepiment which 



* " L'interno della vesicola seminale non presenta un intreccio di fibre, ma solo una rete lassa di sanguigni," &c. 

 (Rosa, p. 376). 



