1885.] NEW-ZEALAND EAUTHWORMS. 823 



mentioned, the setse are in four series of pairs, the nephridia 

 similarly alternate in position from segment to segment (woodcut, 

 fig. 2). There does not, however, appear to be any rei^ularity in this 

 alternation : sometimes the nephridiaof five or six consecutive segments 

 open bv the same series of setae on both sides of the body. In other 

 segments there is an asymmetry of the nephridia of the two sides of the 

 body : for example, the left-hand gland may open by the dorsal, while 

 the right-hand gland opens by the ventral pair of setae ; occasionally 



Fig. 2. 



Acanthodrilus novcB zelandice. — A portion of the body viewed from the side. 

 n, nephridial pores ; s, setae of ventral pair. 



there is a regular alternation coupled with absolute symmetry in the 

 position of the nephridial pores. Moreover, no two individuals of 

 either species that I examined were exactly alike in these respects ; 

 and it was impossible to distinguish one species from the other by 

 the position of the nephridial pores ; occasionally the nephridia, one 

 or both, were found to coincide at the same series of setae as the 

 male and female genital ducts, but in no case did I observe a 

 similar coincidence of nephridium and spermatheca. 



Another point of interest in connection with the nephridia of these 

 two species has not been recorded by Perrier in Plidellus : tlie two 

 seriesof nephridia, dorsal and ventral, show other indications besides the 

 varying position of their apertures of being the vestiges of two com- 

 plete series ; in every instance it was found possible to dislinguish 

 the nephridia of each series by morphological differences. In all the 

 nephridia the muscular portion which forms the distal extremity of 



