STUDIES OX TUE ECTOPAKASITIC TUEM.VToDES OF JAPAN. 243 



half of the ljo:Iy proper. Ociltict ari.sui!:^ fr(3:ii the ventral side of the 

 ovary; thence proceeding forwards and towards the left it is continued 

 into the ootyp at about the plane of tlie liinder end of the penis. 

 Uterus of moderate length, running parallel to the penis, and opening 

 to the exterior just behind the opening of the genital atrium. 

 Vitcllarium occupying neary all those portions of the body left vacant 

 by the other internal organs, extending from the anterior nearly to 

 the posterior end of the body, and also occupying the whole dorsal side 

 of the median region enclosed by the intestinal trunks. Fai red yolk- 

 ducts formed by the union of two large ducts coming from the anterior 

 and posterior regions of the vitellarium on each side of the body, or l)y 

 the union of a hu'ger number of smaller ducts ; proceeding at right 

 angles to the long axis of the body, and forming by their union a large 

 yolk-reservoir at the front end of the ovary just on the left side of 

 the median line. Unpaired yolk-duct short, proceeding dorsally from 

 the 3-olk-reservoir and opening into the oviduct. Ycujinal openiiKj a 

 little behind that of the uterus, nearer the median line ; vaijlwd canal 

 proceeding l^ackwards and inwards at first with a slight winding 

 or two, but reaching the plane of the yolk-reservoir it makes some 

 complicated convolutions and after being enlarged into a seminal recep- 

 tacle, finally opens into the yolk-reservoir. Testes rather small, very 

 numerous, of an irregular shape and more or less lobed, not confined 

 to the median region of the body but extending on both sides a 

 little less than two-thirds the distance between the lateral margins of 

 the body and the intestinal trunks, and in the latter regions reaching 

 from the hinder end of the anterior suckers to the front end of 

 the posterior sucker ; the whole area occupied l)y the testes thus 

 assuming somewliat the form of a cross-section of a biconcave lens. 

 Vas deferens formed by the union of a certain number of vasa efferentia 

 at the posterior, left corner of the ovary, thence proceeding forwards 



