240 DISCOVERY REPORTS 



zation ; parasites (Anoplophryina) are not uncommon in the alimentary canal of these 

 worms, but they do not occur in any extraordinary numbers, and the degree of parasiti- 

 zation would pass without comment if found in specimens of Enchytraeids from our 

 own shores. 



Are all the above-mentioned forms of degeneration at bottom one — a form which 

 comes on at the end of life, which is sometimes introduced by (or is an extension of) the 

 normal post-maturity degeneration of the genital organs, sometimes by the changes in 

 the alimentary canal? 



VARIATION IN FORM OF THE NEPHRIDIA IN THE 



ENCHYTRAEIDAE 



In seeking for characters on which to base specific distinctions in the Enchytraeidae 

 the form of the nephridia has been much used — e.g. the size of the anteseptal portion of 

 the organ, which may consist of the funnel only, or may comprise more or less of the 

 glandular part in addition ; the shape of the postseptal ; the length of the duct relatively 

 to that of the postseptal; its direction — downwards, forwards, or backwards; and 

 especially the place of origin of the duct — -at the hinder end, or from some place on the 

 under surface nearer or further from the hinder end. 



I have previously (1922) drawn attention to the variability of some of these characters ; 

 and the following notes, made in the course of examining the sections (all longitudinal) 

 of some of these worms, seem to confirm what I then wrote. The only really fixed 

 feature of the nephridia seems to be the size of the anteseptal relatively to that of the 

 postseptal portion. 



In a specimen of Lumbricilliis maximiis, in one organ the duct left the hinder end of the 

 postseptal and passed backwards and then downwards to the surface ; in a neighbouring 

 segment the duct left the under surface of the postseptal some distance in front of the 

 hinder end, passing thence first forwards and then downwards and backwards. Similar 

 variations in the place of origin of the duct are found in Marionina aestuum (see the 

 description of this worm, post). 



In Enchytraeus albidus, in consecutive preclitellar segments, the nephridial duct was 

 seen in one to come off at the middle of the length of the nephridium, in the other from 

 the hinder end ; in other preclitellar segments it came off from the under surface in front 

 of the hinder end — about one-third of the length of the postseptal from the hinder end ; 

 while behind the clitellum it left the postseptal at the posterior end. The duct may pass 

 backwards, backwards and downwards, nearly directly downwards, or downwards and 

 forwards, all in four consecutive segments. 



The shape of the postseptal, as seen in sections, depends on the direction in which it 

 is cut. It seems (in L. maxirmis) to be considerably flattened from above downwards, 

 and hence appears broadly oval in a more or less frontal series, narrow and elongated in 

 a sagittal series. 



