ON A NEW HISTRIOBDELLID. 317 • 



appear probable that there are two pairs of canals in this 

 anterior region in the female. In the male, on the other 

 hand, there is no such evidence of division, the pair of 

 nephridia which branch in the head being traceable back- 

 wards, without change in the direction of the cilia, nearly as 

 far as the bases of the second cirri, at which point they bend 

 inwards and terminate in the coelora near the middle line. 

 In some specimens each tube seemed to end in a loop, in 

 others this was clearly not the case ; a difference in the 

 degree of contraction may have been the cause of this dis- 

 crepancy. In all cases the posterior part of the canal, from 

 the point where it begins to bend inwards, has comparatively 

 thick granular walls. The extremity of each is not funnel- 

 like, but is enlarged into a rounded knob which has the 

 appearance of having a narrow cleft on it ; but I am not 

 certain of the existence of a coelomic aperture. The two 

 knob-like ends lie in a compartment of the coolom, bounded 

 by the stomach above and tlie ventral nerve-cord below, and 

 at the sides by a pair of fibrous partitions passing vertically 

 from the stomach to the ventral wall of the body. 



In the fourth segment the nephridia are probably repre- 

 sented in the female by the oviducts, in the male by the vasa 

 deferentia. 



In both sexes a pair of nephridia, which begin in the fifth 

 segment (in a loop in the male), run backwards through the 

 caudal region at the sides of the intestine, and terminate 

 close to the anus. The direction of movement of the cilia in 

 these is from behind forwards. 



The arrangement of these canals, though to some extent 

 partaking in the metamerism of the body, is not strictly a 

 metameric one, there being apparently only three pairs in 

 the male and four in the female. 



Ciliary flames have not been observed, and, I think I may 

 say positively, do not occur in any part. 



To judge from Foettingei''s description and figures, there 

 is an important difference between Histriobdella and Stratio- 

 drilus as regards the excretory system. " Ces canaux ue se 



