STUDIES OX THE ECTOPABASITIC TREMATODES OF JAPAN. (57 



but as their course is always more or less winding, they are not seen 

 in cross-sections exactly between the intestine and the ventral nerve, 

 but are often situated more on one side, right or left, as the case may 

 be. One of the two main vessels, the larger one, opens to the exterior 

 mostly with an extremely small pore in the anterior part of the body 

 on the dorsal side, close to the lateral border. This is also the case in 

 Onchocottjle, the paired terminal sacs described by Taschenberg'^ 

 being, as already stated, nothing else than the suckers. In Microco- 

 tijle, I have not been able to observe the excretoi'y vessels in specimens 

 mounted in toto, and therefore have not drawn them in the figures : 

 but I could always recognize the two main vessels in serial cross- 

 sections. In this gedus, the excretory openings are situated nearly on 

 the same level Avith the genital opening : in M. elegans it is 5 sections 

 (each = 10 u), and in M. caudata 10 sections in fit-ont of the genital 

 opening ; while in M. sebastis it opens on the same level with it. 

 Lorenz speaks of a small papilla on which the excretory vessel 

 opens ; but I have not observed any in my sections. In this genus, 

 there is no distinct terminal sac, the vessel presenting just a perceptible 

 enlargement before it opens to the exterior. In Dididoplwm also, the 

 excretoi'y openings are nearly on the same level with the common 

 genital opening : c. g., in Diclid. sessilis it is about 7 sections (eachn: 

 10 fi) behind it ; but in this genus there is a tolerably large, egg- 

 shaped terminal sac (PI. X, fig. 5), which opens directly to the exterior. 

 In Axlnc, Onchccotyle, and Hexacotyle, the excretory openings are at 

 some distance in front of the common genital opening, and the two 

 main vessels present each only a slight enlargement before opening to the 

 exterior. In Monocotyle, there is a large terminal sac of an ellipsoidal 

 form, which communicates with the exterior by means of a short 

 canal proceeding from its dorso-lateral border a little before the middle 



1). Tasohenberg— Weitere Beitriige, p. 13. 



