230 Proceedings of the Royal Society of Victoria. 



duct piisses to the exterior where it opens on the fourth annulus 

 of each segment, and resembles in its marginal position the land 

 leeches of Japan described by Whitman. 



With regard to the structure of the excretory duct it may 

 be said that circular muscles occur along the whole of its lenath. 

 In this respect it resembles Nephelis as described by Graf.^ The 

 muscles are smaller than those of the body wall, but as far as 

 I can make out they do not increase in number or size at the 

 nephridio-pore, which may account for the difficulty, in fact the 

 impossibility, of detecting the openings on the external surface. 



In addition to those which are present along the whole length 

 of the duct, a special and very strongly marked group of fibres 

 forming a distinct sphincter is present where the duct passes out 

 from the vesicle. 



So far as their relative size is concerned there is not the 

 strongly marked difference in size between the sphincter muscles 

 and those of the body wall such as Graf describes as obtaining in 

 the case of Hirudo, nor, except so far as size is concerned, does 

 there appear to be any difference in the structure of the two 

 in Phihiemon. 



I regret that I am unable to refer to tlie paper by H. Bolsius, 

 mentioned by Graf in his article on the Sphincter of the Terminal 

 Vesicle of Hirudo medicinalis. Evidently the sphincter described 

 by Bolsius occurring at the entrance of the duct from the terminal 

 vesicle is similar to that found in Pbihemon, in which case the 

 sphincter is formed of a group of circular muscle fibres somewhat 

 smaller than those of the body wall but of the same size as the 

 circular muscles surrounding the rest of the duct. 



In a dissection it can be seen that the 1st and 17th pairs 

 of nephridia lying in segments YI. and XXII. respectively differ 

 in appearance from the others. The anterior (1st) is a pinkish 

 white oval mass lying one on each side of the oesophagus towards 

 the dorsal surface, and is much more compact than those of the 

 other segments. The excretory duct from its vesicle runs up in the 

 circular muscles and opens (Fig. 2) on the sixth annulus between 

 the fourth and fifth pairs of eyes— that is on the last annulus of 

 segment IV., there being no external opening in segments V. or 



1 Jouni. of ilorijholoy:y, vol. ix., 1S04, p. 485. 



