STUDIES OS THE ECTOPAEASITIC TREMATODES OP JAPAN. 27 



shoe shape seemingly on the dorsal but morphologically on the ventral 

 side of the body, and are hemispherical in shape. The wall consists, 

 as in the preceding cases, of prismatic, refractive fibres set closely 

 against one another, and is bomided on aU sides by a cuticular mem- 

 brane. This membrane is chitinously thickened into band-shaped 

 strips in an antero-posterior direction (PL XV, fig. 8). The 

 wall of each sucker is again divided in two, each half crescent- 

 shaped in cross-section, and separated from the other by an in- 

 tervening zone of mesenchyma, in which a single, strong, hollow, 

 chitinous piece of semicircular shape and provided with a hook at 

 one end lies imbedded (PL XV, figs. 8 & 9). The inner half of the 

 wall is smaller than the other. There is no distinct marginal mem- 

 brane, but the investing membrane presents a fold all round at a short 

 distance from the mouth of the sucker (fig. 8). 



In the natural position, the hooked end of the semicircular 

 chitinous piece is directed towards the anterior end of the body ; and a 

 strong bundle of muscular fibres is attached to the other end of the 

 piece. Besides this, detached fibres are also attached to the lateral 

 margin of the suckers. 



The remaining pair of suckers, which are much smaller,- is 

 situated at the extremities of the bifurcations of the caudal appendage 

 which constitutes such a salient feature of this genus. Each sucker 

 has the shape of a water-melon with a constriction at the posterior 

 part ; and its mouth is very narrow (PL XV, fig. 2). Its cavity is 

 also very narrow ; but the wall is very thick, and consists entirely of 

 a connective tissue interspersed with nuclei, which are more abundant 

 in the posterior portion of the sucker (PL XV, figs. 1 and 2). The 

 fibres of the connective tissue are mainly arranged radially, and form 

 an irregular network. The wall is bounded towards the mesenchyma 

 by a thin, cuticular membrane, and its inner surface is lined by the 



