554 FRANK E. BEDDARD. 



is very common among the terrestrial Oligochseta, viz. a sepa- 

 ration of the nephridia into two series, an anterior and a 

 posterior; this is seen, among other forms, in Pontodrilus 

 and in Microchseta. In the segments occupied by the 

 spermatheca, viz. in Segments 13 — 17,^ no trace of nephridia 

 could be detected in a dissection. I am disposed to refer 

 this partial obliteration of the nephridia in this region of 

 the body (we shall see immediately that they have not abso- 

 lutely disappeared) to the enormous development of the 

 spermathecal sac, which occupies most of the available space; 

 the case is, in fact, analogous to that of many aquatic forms 

 in which the nephridia disappear with the appearance of the 

 genital organs. 



Each nephridium (fig. 11,/.) has a funnel lying, as usual, 

 in the segment anterior to that which bears the external 

 pore. The nephridia of the posterior segments are enve- 

 loped by a mass of peritoneal cells ; such at least appears 

 to be the nature of the very peculiar tissue illustrated in 

 fig. 10, c. I may remark here that both Heliodrilus and 

 Hyperiodrilus have a similar investment to the nephridia. 

 A covering of this kind which is simply an exaggeration of the 

 ordinary peritoneal layer is very characteristic of the aquatic 

 Oligocheeta, but it has before now been recorded in earth- 

 worms; it was first described in an earthworm by Perrier in 

 Pontodrilus. 



In sections of Libyodrilus which have been stained with 

 borax carmine this mass of cells is very deeply coloured ; the 

 staining fluid has, however, chiefly aff'ected not the protoplasm 

 of the cells, but innumerable spherical particles with which 

 they are crowded. Among these deeply-stained spherules are 

 masses of others, rather larger, which are not stained at all 

 (cf. fig. 6, c'.). The cells were not, however, always found 

 to be loaded with the products of their activity; occasionally 

 the nephridial tube is embedded in a mass of deeply-staining 

 cells, of which the nuclei were very conspicuous ; the out- 



1 There was sonic variation, probably due to different stages of maturity, 

 in the number of segments from which nephridia were apparently absent. 



