ON THE ANATOMY OF ALLURUS TETRAEDRUS. 369 



my own of the gizzard of Urochseta. The intestine has a 

 typhlosole. 



The buccal cavity (see fig. 10) occupies the first three 

 segments. The pharynx lies in 4, 5, and 6. 



The oesophagus, from the middle of Segment 10 to the end 

 of Segment 14, is furnished with a structure which corresponds 

 with the calciferous glands of Lumbricus and other earth- 

 worms; the oesophagus is here rather wide, and the lateral 

 region is much folded ; these longitudinal folds (fig. 2 ca ) 

 are quite continuous from segment to segment ; there is no 

 question of any separation into distinct glands. This arrange- 

 ment is possibly to be regarded as a primitive one. 



The epithelium of the oesophagus, which differs in character 

 from that which covers the lateral folds, is very distinctly 

 ciliated in the segment where the folds are developed (fig. 2 a.). 



In segment 10, at the junction of the anterior section of 

 the oesophagus with that part which has just been described, 

 is a short diverticulum on either side ; this diverticulum marks 

 off the non-ciliated anterior region of the oesophagus, which 

 also differs from the ciliated region in the shape of its cells. 

 They are not quite so tall and narrow as the ciliated cells. In 

 all these particulars the diverticulum agrees in structure with 

 the anterior section of the oesophagus. 



The crop occupies the 15th and 16th segments. 



With regard to the nervous system, I may mention that 

 the cerebral ganglia are in the 4th segment (fig. 10), and that 

 the ventral nerve-cord has cells along its whole length. 



Nephridia. — These organs consist for the most part, as in 

 the Oligochseta generally, of a series of "drain-pipe" cells; 

 as in Lumbricus and other genera, the calibre of the inter- 

 cellular duct, and of the cell which contains it, is at first less 

 than it becomes afterwards. Fig. 11 is a transverse section 

 through a nephridium which illustrates this fact; a are the 

 smaller drain-pipe cells, n the larger. The nephridium is sur- 

 rounded by a number of peritoneal cells (p.) ; these are oval in 

 form, the protoplasm appeariug almost homogeneous and have 

 a darkly staining nucleus. The larger drain-pipe cells n' appear 



