STRUCTURE OF EARTHWORM OF GENUS DIAOH/ETA. 167 



interrupted in the middle line^ as shown in the figure (fig. 15) ; 

 a number of muscular fibres of different appearance from those 

 out of which the circular muscular layer is formed ; they are 

 of less diameter, and not composed of a bundle of closely 

 united fibrils. These few fibres are shut off in a compart- 

 ment which runs completely round the segment^ and which is 

 partially divided up by a fine network in the meshes of which 

 lie the individual fibres. This peculiar specialisation was to be 

 seen in the anterior segments of the body commencing with 

 the vith ; it is possibly this which gives rise to the appearance 

 of annulatiou already referred to as seen in the anterior 

 segments. 



§ Nephridia. 

 The nephridia do not seem to differ much from those of 

 D. Thomasii. The first six segments are occupied by a large 

 pair of nephridia, which differ much in minute structure from 

 the ''mucous glands ^^ of Urochseta, although agreeing with 

 them in being very much larger than the following nephridia; 

 the apertures of these nephridia appear to be upon the ivth seg- 

 ment, and all the following segments are provided with a pair. 

 The external apertures are placed very far forward in the seg- 

 ments, quite in the intersegmental furrow j they are furnished 

 with the remarkable cup-like structure (fig. 14) at their 

 external aperture, which has hitherto been only found in 

 Urochseta; it seems to be clear that the structures are 

 muscular, and perform the office of a sphincter; the muscular 

 fibres are chiefly disposed in a radial direction, but outside 

 is a thin layer of circularly disposed fibres, which, though 

 fewer, are thicker than the radial fibres, and may be of equal 

 strength. 



§ Alimentary Tract. 



There are two noticeable peculiarities about the alimentary 

 canal of this earthworm : the first is the presence of a large 

 thin-walled crop of equal diameter with the gizzard, into 

 which it opens immediately ; the gizzard itself is situated in 



