STUDIES OX THE ECTOPARASITIC TEEMATODES OF JAPAN'. 221 



front of the suckers, and unite in the median line just in front of the 

 innermost of the larger pair of suckers. Common genital opening a little 

 in front of the antei'ior end of the median pair of intestinal trunks. 

 Ovary in the median line, at about the middle of the whole length of 

 the body, long, bent on itself like a loop, with numerous secondary con- 

 volutions, and with the open end of the loop directed backwards. The 

 oviduct arises from the end of the right arm of the loop, thence proceeds 

 backwards and towards the right, and after receiving the genito-intes- 

 tinal canal turns backwards, and then making one or two convolu- 

 tions, turns dorsad, and is continued into the ootyp, which is tolerably 

 long, and lies with its length directed obliquely in an antero- 

 posterior direction. Uterus taking a course as in H. acuta. Genito- 

 iniestinal canal arisina: from about the middle of the whole course of 

 the oviduct, enlarged into a voluminous receptaculum seminis, from the 

 anterior end of which the small convoluted canal proceeds forwards 

 and towards the right, and finally opens into the inner trunk of the 

 intestine. Vitellarium extending from the level of the vaginal opening 

 to a short distance behind the posterior end of the testes. Paired yolk- 

 ducts asymmetrically disposed with respect to each other ; that of the 

 right side arising from the vitellarium on the same level with the 

 opening of the genito-intestinal canal into the intestine. The 

 aiTangement of the paired yolk-ducts with respect to each 

 other and to the unpaired yolk-ducts as in H. acuta. The 

 impaired yolk-duct opening into the oviduct side by side with 

 the genito-intestinal canal, but not so closely as in H. acuta. 

 Vaginal opening dorsal, a short distance behind the common 

 genital opening ; the single vaginal canal soon dividing into 

 two, which are disposed as in H. acuta and become continuous 

 each with the paired yolk-duct of the same side. Testes numerous, 

 of moderate size, posterior to the ovary, and ending a little in 



