68 ME. F. E. BBDDARD ON THE ANATOMY AND 



surface in the way shown in fig. 3, PL XV. The portion of the duct which lies 

 beyond (above) the aperture evidently corresponds to the vesicular diverticulum of the 

 more anterior nephridia. 



The large size of the nephridia (J inch) rendered it quite easy to inflate the duct by 

 means of a blow-tube, and to make sure of the connection between the duct and the 

 diverticulum, though this was sufficiently obvious without. 



The upper portion of the wide muscular duct of the segmental tubes in this region 

 of the body is thickly covered by a layer of large cells filled with round, clear bodies of 

 a brownish tint ; these were so numerous as to obscure the nucleus altogether. The 

 presence of these cells gives a yellowish colour to that part of the nephridium where 

 they exist, the rest being almost colourless. These cells appear to be simply modified 

 cells of the perivisceral cavity; they are also extremely abundant on the intestine, 

 where their occurrence has been long known in the common Earthworm. It is very 

 remarkable to find them only covering the nephridia of the posterior half of the body, 

 and absent from the more anterior series in Microchceta. In fig. 3, PI. XV., are 

 displayed some of the nephridia of the posterior region of the body ; the distribution 

 of the " chloragogic " cells is indicated by the dotting on the terminal section of 

 the nephridium ; below this region, which ends very abruptly, are hardly any traces of 

 these cells, only a few being visible here and there. The statement that these peculiarly 

 modified perivisceral cells are absent also from the anterior series of nephridia does not 

 of course imply that these latter have no peritoneal covering. 



The nephridia of Microchceta are, on the whole, similar to those of other Earth- 

 worms, but differ by the disproportionate development of the terminal muscular portion 

 of the organ, and also by its large diverticulum. A similar diverticulum is figured by 

 Gegenbaur in Samiris ^ 



In certain of the anterior segments of the body there are a number of structures 

 developed near the orifice of the segmental organs which have some interest in connec- 

 tion with the much debated question of the homologies between the nephridia and the 

 copulatory pouches. 



These are represented on fig. 4 of PI. XV., and more highly magnified in fig. 6. 

 In the thirteenth segment is a single minute whitish body about the side of a millet- 

 seed ; this body is a csecal pouch witli muscular walls opening on to the exterior of the 

 body in front of the nephridium. In the succeeding segment there are four of these 

 pouches arranged as in the figure, the two innermost being partly fused ; in segment 

 fifteen the disposition of these pouches is entirely similar, except that the two 

 innermost are connected together at their upper instead of at their lower extremities ; 

 finally, in segment sixteen there is only a single pair of these pouches corresponding 

 to the innermost pair of the two segments immediately antecedent. 



' "Ueber die sogcnannten Eespirationsorgane der Kegenwurmer," Zeitsckr. f. wiss. Zool. Bd. 1852. 



