1913.] 'J^'. Southwell : Parasites from Fish. 93 



being broadly rounded and the anterior extremity being pro- 

 duced into a rather long, thickened, acute projection with a 

 rounded extremity. The thickening is apparently due to the 

 presence of the cirrus sac. This projection shows a marked 

 tendency to curve ventrally and assume a position at right 

 angles to the body. The oral sucker is situated somewhat vent- 

 rally, at the extreme anterior. In the largest specimen (referred 

 to as c) the diameter of the sucker was "7 mm. In the same 

 specimen the ventral sucker was situated 7 mm. from the anterior 

 extremity and had a diameter of i mm. with extremely thick mus- 

 cular walls. The genital aperture is situated midway between the 

 oral and the ventral suckers and had a diameter of "85 mm. The 

 aperture of the excretory apparatus is situated posteriorly and is 

 median. In mature specimens the testes can be seen as opaque 

 milky-white globular bodies, r mm. in diameter, situated one on 

 each side, and slightl}^ posterior to the ventral sucker. The vitel- 

 line glands are conspicuous as darkish masses aggregated on the 

 posterior dorsal surface and disposed principally round the posterior 

 termination of the two rami of the gut. These two rami stand out 

 prominently as a pair of black sinuous tubes having a diameter 

 of I mm., and running from the anterior to the extreme posterior 

 end of the worm, where they terminate blindly. They occup}" a 

 considerable part of the middle f rds of the length and breadth of 

 the worm. The uterus is just visible as a delicate sinuous tube 

 starting from the posterior end, running along the posterior 

 laterally-directed loop of one ramus of the intestine, across to the 

 laterally directed loop of the other ramus of the intestine, etc., to 

 the genital aperture. Under magnification the tissue of the para- 

 site presents a granular appearance. 



Digestive system. — The mouth is situated at the base of 

 the oral sucker and leads directly into a stout muscular pharynx. 

 The oesophagus is exceedingly short and divides immediately into 

 the two rami forming the intestine. Bach branch runs at first 

 straight towards the lateral margin of the worm and, rounding the 

 ventral sucker laterally, runs ventrally to the posterior end in the 

 form of a continuous letter S. The two rami do not lie symmetri- 

 cally. The centrally directed loop of one ramus is situated opposite 

 the laterally directed loop of the other ramus. The disposition of 

 the coils of the uterus round these loops will be noted later. The 

 two rami of the intestine extend to the extreme posterior extremit}^, 

 where they terminate blindl}', close to each other. The wall of the 

 intestine is pigmented with very dark brown, almost black, and is 

 minutely, annularly rugose throughout its length. 



■Excretory system. — Unless sections are made the gross details of 

 this system cannot be made out, except perhaps in the living worm, 

 and not always then. 



The excretory aperture is situated at the posterior margin of 

 the worm and is median. This aperture leads into a more or less 

 globular or c^dindrical contractile vesicle. From this vesicle the 

 excretory duct runs forward a little distance and then bifurcates. 



