NEW ENGLISH GENUS OF AQUATIC OLIGOCH^TA. 159 



ordinary clitellar cells. Although, superficially, the clitellum 

 appears to cease at this spot, yet transverse sections show that 

 the characteristic ceils are continued across the ventral surface, 

 but are only one or two rows deep. 



It may be mentioned that in Bhinodrilus this clitellum is 

 visibly "complete" in its anterior region, but apparently "in- 

 complete " posteriorly. 



In the mature worm, where the clitellum is most fully de- 

 veloped, I could find in sections no lateral chaetse, although 

 the ventral ones are distinct enough ; I believe they are, in fact, 

 here absent. But whether they are absorbed or whether they 

 drop out is, I believe, a matter of speculation. I am inclined 

 to think that they drop out. At any rate, in sections of a 

 worm which had passed its maturity, and in which the clitellar 

 cells are degenerating (fig. 20), giving thus the appearance of a 

 subepidermic connective tissue, I find the lateral chsetse very 

 small ; they appear to be newly formed, and do not by a long 

 way perforate the body-wall. 



II. The Internal Anatomy. 



§ With regard to the alimentary tract little need be said. 

 There is no gizzard, not even a thickening of wall ; a fairly 

 sharply marked division occurs been oesophagus and intestine. 

 The latter commences in Somite ix, where the gut suddenly 

 enlarges ; and a change in the epithelium, as well as in charac- 

 ter of the wall, is noticeable. The oesophagus has a fairly thick 

 wall ; the lining epithelium, which is considerably folded, con- 

 sists of tall, ciliated cells. The wall of the intestine is thinner, 

 the epithelium much lower, less folded, and the cilia shorter. 

 The end of the oesophagus projects, valve-like, into the intes- 

 tine, and here the change in the epithelium is well seen, the 

 cells of this portion of oesophagus being taller than elsewhere. 

 There is no typhlosole in the intestine, nor calciferous glands 

 to the oesophagus. 



The buccal region occupies, as will be seen from the figs. 

 12, 13, about two somites. The pharynx is short, and pro- 



