126 S. GOTO. 



triangularis I have not been able ,to observe the vagina, since I had 

 only a single specimen of this species ; but its presence is scarcely to 

 be doubted. 



In Hexactyle also, the vagina opens to the exterior on the dorsal 

 side of the body in the median line, a short distance behind the com- 

 mon genital pore on the ventral side (PL XIII, figs. 1 & 4; PI. XII, 

 fig. 6); and its internal surface is armed with numerous chitinous, 

 conical teeth similar to those of Axine (PL XII, fig. 6; PL XIV, 

 fig. 3). The connective tissue around it presents a very different aspect 

 from that of the remaining parts of the body, and is exceedingly com- 

 pact and refractive. It is somewhat yellowish iu the fresh state, and 

 remains totally unstained with carmin or haematoxylin. In fact it is 

 of the same nature as the tissue that surrounds the vagina in Axine 

 and the terminal portion of the vas deferens in Microtyle reticulata and 

 Onchocotijle ; but it is far more compact, so that it appears as if it were 

 somewhat chitinous. In the genus under consideration the vagina is 

 surrounded by numerous, circular muscular fibres; moreover from the 

 chitinous cuticle that lines its cavity numerous muscular fibres take 

 rise and radiating in all directions and ramifying each into a 

 number of fibres, are at last inserted into the investing membrane 

 of the body (PL XIV, fig. 3). These muscular fibres are evidently 

 the retractores vaginae. The vagina soon divides into two canals, the 

 canales vaginales, which, as in the cases already described, proceed on 

 the inner side of, and parallel to, the trunks of the intestine, and open 

 into the paired yolk-ducts. In accordance with' the asymmetry in 

 this genus of the yolk-ducts of the two sides, already mentioned, the 

 vaginal canal of the left side is longer than that of the right (PL XIII, 

 figs. 1 & 4; PL XIV, figs. 1 & 7). 



From the above description the paired origin of the vagina in 

 Microcotyle, Axine, and Hexacotyle is, I believe, beyond question. 



