S2 Mr. W. Nicoll on lh<^. 



tMul. Tt is api'Voxiniatcly {jlobular, ami luis a diameter of 

 •33 mm. \>itli a circular aiurturc. 



The aliment, rv sy.stciu is fairly typical. The |)rc|)liarynx 

 is shorter than in Steph. cest'icillus, being only -17 mm. long. 

 The pharynx is large and almost horsc>hoe-shai;ed, with the 

 convexity directed backwards; it measures 'SI x "IG mm. 

 The ocsophaijus is extremely sljort. The diverticula extend 

 to the posterior extremity, and are wide and irregularly 

 dilated. The bifurcation occurs just a little in front of the 

 ventral sucker. 



The testes are situated in the postericir third ot" the body, 

 one behind the other in the middle line. In shape they are 

 ovoid, and have a greatest diameter (longitudinal) of '38 mm. 

 The ovary lies directly iu front, almost median or a little to 

 the right, aud is less than the testes ('21 mm). The vitelline 

 glands are lateral, extending from the posterior ced of t! c 

 body to a short distaucc behind the ventral sucker ; they 

 consist of small compact follieles. 



There are very few ova (l/), but they are of large size, 

 measuring •087-091 mm. x 014-053 mm. The shape is 

 unusual, pointed at one end and truncated at the other*. 

 The uterus lies entirely betwccu the ovary and the ventral 

 sucker, aud is confined laterally by the intestinal diverticula. 

 There is a long club-shaped penis-sac extending some 

 distance behind the ventral sucker, though not so elongated 

 as in btejjh. cesticillus. The posterior portiou is occupied by 

 a large ovoid vesicula seminalis. There is a considerable 

 pars prostatica. The genital aperture is median, directly in 

 front of the ventral sucker. 



It is evident that this species diffirs very considerably 

 from already known forms, lu the first place the body is 

 much less elongated, and the suckers are proportionately 

 further apart aud larger. The cephalic spines, besides being 

 more numerous than in any other species, are dift'erently 

 disposed, those in the anterior row being shorter than those 



* Three ova were ol)serve<i lying within the ventral sucker. This 

 recalls a condition already noted (Ann. & Mag. Nat. llist. (7) xvii. p. 520) 

 in a para!=ite inhabiting the cloaca of Lams aryentatus. The suppisition 

 which I then hazarded seems to be strengtheutd by this case. iJolh are 

 forma lising in the terminal portion of the gut of their host, and the 

 possibility suggests itself that in both the ova may be retained for some 

 time within the ventral sucker in order to pi event their being excreted 

 in too immature a condition. Many form.-< having a similar habitat 

 display adaptations in the ova, having apparently the .same end in view. 

 The precocious development of eye-.spots in several species and the 

 ciliated embryos in Lliatomum viviparum, C)l~son (from ti.e end-gut of 

 Pleuronectid fishes), are illustrative cases. 



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