Cambkox. — Kfpliridiinn of Miioiidrilus rosae Beddard. 



The position of the iirst paii' of nephridioporeji cletierNes particular notice. 

 <)s it has been recorded hitherto for only a few other species. Each pore 

 is at the extreme anterior margin of the 2nd se.ument, just l)ehind the inter- 

 segmental groove, and slightly external to the furrow which limits the back- 

 ward prolongation of the prostomium which crosses the 1st segment. 



It has occurred to me that perhaps this groove alongside the base 

 of the prostomium may have some fimction in connection with the ne- 

 phridium. It is evident that the secretion dischaiged from the nephridio- 

 pore would readily flow^ along the groove which would lead it on to the food 

 while this was being takeii into the mouth. How far is this association of 

 a, ■■ tanylobic " prostomium with a pepto-nephridium at the hinder end of 

 the furrow wides})read '. 



The only figure that 1 have been able to find showhig this position is in 

 Benham's acctiunt of Neodrihfs monocystis, where it occupies the same 

 position as I have here described. But he also notes that in Playiochaeta 

 pHiidala the " vestigial "' nepln-idium of the 3rd segment opens by a pore 

 in this position. 



A few other instances may be noted here, for it is stated as a general 

 iiiie in earthworms that the first nephridiopore lies in the 3rd segment. 



nep.cL. 



nc.pv. 



ch..v. 



ch.d. 



Fig. 2. 



-A dorsal and a ventral iK-plu-idium, as .seen by opening the worm in the mid- 

 dorsal line. Drawn from Mcioridrilus uliginosus, in which the caecum of 

 the ventral nephridial bladder is longer than that of M. rome. though the 

 nephridia are. in general, very similar. 



Beddard (P.Z.S., 1887) states that in Thunniodrilns iiidiehni (p. 154) and 

 in Phdellus (Cryptodrilns) fletcJieri (p. 544) the first poie lies in the 2nd 

 segment, as it does too in Anplophihis (Eisen) and one or two others. Bur 

 it seems that little attention has been paid to details of this kind. 



The dorsal shifting of the anterior pores has also been noted by Eisen 

 for Deltania. where the nephridiopores ncnmally lie in front of the 3rd 

 chaota, but the three anterior pores are in line with the 4th. He notes 

 similar facts for Phoeiucodrilus. 



Bourne states that in Moiiilifjaster (irdiidis the fiist seven poies (those 

 of Segments iii to ix) lie dorsad of the normal position, which is in line witli 

 the outer {i.e., dorsalmost) chaeta of its segment. Indeed, it appears that 

 this shifting occurs in various genera. 



The Nephridia. — On the worm being opened, the nephridia are Setni t<> 

 be arranged in two series, corresponding to the extcn'ual pores. Those 



