Dr. Johnston on Entozoa. 435 



Desc. The body is about three lines long, oblong-ovate 

 when at rest, but extensible and mutable to a considerable de- 

 gree, not much compressed, of a brown colour varying in in- 

 tensity and more or less clouded, smooth, somewhat transpa- 

 rent. Mouth subterminal, placed under the narrower end, 

 circular, edentulous, with a thickened lip : the ventral sucker 

 about a line backwards, larger, encircled with a prominent 

 plain rim : posterior extremity obtuse, thickened, wrinkled 

 and opake, with a small emargination in the middle. 



This worm has that degree of transparency which allows 

 the viscera to be seen through the skin, but to trace their 

 figures and disposition it is necessary to compress the body 

 slightly between plates of glass. The mouth (fig. 5, a.) is ca- 

 pable of being shut close or dilated to a considerable width, 

 the aperture assuming, in the change, sometimes a circular 

 and sometimes a triangular figure, but it is not susceptible of 

 being protruded beyond the surface. The powerful sphincter 

 encircling it enables the animal to apply the orifice very closely 

 and firmly to the surface of the stomach of the fish it infests. 

 The oesophagus is extremely short. From each side of it there 

 proceeds, nearly at right angles, an intestine (i) very narrow 

 at its origin, but suddenly dilating, it trends, in a flexuous 

 curve, towards the sucker (s), whence it proceeds down the 

 body in nearly a straight course and ends in a cul-de-sac near 

 the posterior extremity. This intestine is filled with a colour- 

 less liquid, and, as the liquid does not escape on pressure 

 from the mouth, but undulates backwards and forwards, we 

 are led to infer that a valvular apparatus at the origin of the 

 intestine prevents its efflux. The lower half of these intestinal 

 tubes is plaited transversely. Returning to the oesophagus we 

 observe an organ (t), apparently continued from it down the 

 middle of the neck, and dilating into a pear-shaped sac of a 

 faint reddish colour, situated anteriorly to the sucker. This 

 sac is supposed to be a testicle, with what degree of probabi- 

 lity I am not prepared to say. The ovary or oviduct forms a 

 greatly convulated opake thread, which occupies principally the 

 centre of the body between the sucker and the tail : the infe- 

 rior end of it seems to be connected in some way with the 

 thickened tail of the worm, although I have not been able to 



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