BY S. .1. JOHNSTON. 729" 



sucker. There is a short u'sopliagus, 0()8 nun. lonj;-. Tlie in- 

 testinal limbs run at first anteriorly, as far as the oral sucker, and 

 then run backwards, in a straight or slightly wavy course, to the 

 extreme posterior end of the body. Looss(8) says, of //. mquans 

 Lss., that these forwardly running loops are caused by the con- 

 tracted state of the body; but I cannot agree with this, in regard to 

 the similar loops found in the two species of Harmostomum de- 

 scribed in this paper, but regard them as very characteristic and 

 peculiar features of their alimentary canal. My specimens show 

 no signs of unusual contraction, and there seems to be no reason 

 why the slight, but inevitable contraction brought about by ordi- 

 nary methods of fixing and preserving, should cause this peculiar 

 feature in these worms and their relations, but in no others. 



The excretory system is peculiar, and corresponds, in its main 

 features, to that of //. leptostomum Olss., described by Looss (9, 

 p. 168). The median, undivided part of the excretory vesicle, 

 opening at the posterior end of the body, is very short, only 0-16 

 mm. long; but it divides into two branches that run to the level of 

 the oral sucker, and, bending round, course back once more to the 

 posterior end, giving off numerous capillary branches, that end in 

 flame-cells, along their whole length; but the flame-cells are more 

 numerous at the anterior end than elsewhere. A special feature of 

 these vessels, which Looss, in the case of H. leptostomum Olss., 

 regards as branches of the vesicle itself rather than ordinary col- 

 lecting tuljcs, is that, for part of their course, they possess little 

 patches of cilia projecting into their lumen. 



The genital pore is situated on the ventral surface, in the middle 

 line, just in front of the anterior testis. The testes, which are 

 large oval bodies lying in the posterior third of the body, seem 

 to be characteristically placed, the anterior with its long axis trans- 

 versely or slightly obliquely across the body, while the posterior has 

 its long axis lying directly longitudinally in regard to the body of 

 the worm. They are equal in size, and measure 0-57 mm. x 0'46 

 mm. The ovary, which lies between them, and is sometimes slightly 

 overlapped by them, is also oval in shape, with its long axis trans- 

 versely placed. Tlie vasa deferentia come off from the middle of 



