NEW GENERA AND SPECIES OF EARTHWOKMS. 253 



terminating in a blunt rounded extremity, projects apparently 

 out of the mouth, and might easily be mistaken for a prosto- 

 mium if the worm were in a poor state of preservation. 



This structure, however, differs from the prostomium of 

 nearly all other Oligochseta : in Sutroa, for example, which 

 possesses a long prostomium, the buccal lobe is simply pro- 

 longed; this is also the case with the few Naids that have a 

 long prostomium. In the earthworm described in the present 

 paper the conical process which looks like a prostomium arises 

 within the buccal cavity . The examination of a series of trans- 

 verse sections (fig. 1) shows that it is a process of the tissues 

 lying outside the epithelium of the buccal cavity, which is 

 covered by a layer of epithelium continuous with that of the 

 buccal cavity. In such a series of sections the process in question 

 appears first of all as lying freely within the buccal cavity ; it 

 is covered with a layer of tall, closely packed epithelial cells. 

 The interior of the process contains a few muscular fibres and 

 a number of large nerve-twigs. Further back the process is 

 seen to lie in a diverticulum of the buccal cavity, which it 

 nearly fills. Further back still the epithelium lining this 

 diverticulum becomes continuous with the epithelium covering 

 the process. This occurs just above the cerebral ganglia. It 

 is evident from the structure of this process that it can be 

 everted and retracted ; containing as it does nerve-filaments 

 arising from the cerebral ganglia, it probably serves as a tactile 

 organ. The only other earthworm which is provided with an 

 organ that is at all comparable to this process is Rhino- 

 drilus ; Perrier, however, states that the anterior "^^ tentacle''' 

 of Rhinodrilus has no relation to the digestive tract: it is 

 simply a process of the body. But Vaillant^ remarks of the 

 same species, "D'apres mes notes, ce ne serait pas une veritable 

 trompe, mais une extroversion de la partie anterieure du tube 

 digestive, elie paraissait entouree a la base par la bouche, 

 ornee d'une sorte de levre frangee.'^ My own description- of 



' " Annelides," in * Suites a Buffon/ t. iii, p. 190, foot-note. 

 ^ "Oa tiie Structure of a New Genus of Lumbricidse (Thamnodrilus)," 

 •Proc. Zool. Soc.; 1887- 



