STUDIES OX THE ECTOPARASITIC TREMATODES OF JAPAN. 5 



It is sharply pointed at the anterior end, very broad in the middle 

 portion, presents a constriction at a short distance from the posterior 

 end, again broadens out, and then suddenly diminishes in breadth, 

 so that at this part the lateral borders form the two equal sides 

 of a very flat isosceles triangle with its apex directed posteriad, and 

 have generally been designated as the posterior border. There is 

 however a small notch at the apex. 



In Oclocotijle (PI. IX) and OnchocoUjlc (PI. X^^), the body is com- 

 paratively much thicker, and tlie cross-section presents in some parts 

 almost a circle. In Octocotijlc, the caudal disc is not distinctly dis- 

 tinguishable from the rest of the body, the suckers being borne simply 

 on the ventro-lateral margins of the posterior portion (PI. IX, fig. 7). 

 In fig. 1 on PI. IX, the caudal disc is apparently set off from the 

 remaining portion of the body by a sudden diminution of breadth ; but 

 this has been caused by the specimen having been killed under the 

 pressure of a cover-slip, and the body proper having been aljnormally 

 flattened in consequence. In fresh specimens or in those killed free, 

 there is no such distinct boundary. In (Jnchocolijli', on the other hand, 

 the caudal disc is distinctly marked off from the anterii^r part by a, 

 constriction, and bears, as is well known, a subcylindrical appendage 

 projecting from its anterior end on the dorsal side of the body. The 

 end of this appendage, which bears a pair of suckers (mistaken by 

 Taschen berg for the terminal vesicles of the excretory system, see 

 p. 28) and a pair of hooks, is in my o[)inion to be regarded as the 

 posterior end of the body, with the body bent a little obli(|uely on itself 

 towards the dorsal side, so that the suckers have come to lie apparently 

 on the dorsal side. In proof of this view, it may l3e mentioned (1) 

 that the two surfaces of the appendage and the caudal disc are seen, 

 in serial sections, to be directly continuous with the dorsal and ventral 

 surf ices of the body ; (2) that there is a pair of hooks at the end of 



