STUDIES ON THE ECTOPAEA.SITIC TEEMATODES OP JAPAN. J43 



tissue; while in M. sehastis the transition is more gradual. , Moreover, 

 in the latter species there are numerous large, vesicular nuclei close 

 around the mass, each of which is surrounded by a sparse quantity of 

 finely granular protoplasm gradually fading away towards the periphery, 

 just as in M. caudata. In M. cJwVi (PI. V, fig. 4) and M. sciaenae (PL VI, 

 fig. 2) there is at the dorsal end of the genital atrium a cup-shaped or 

 bag-shaped organ, the wall of which is completely set off from the 

 surrounding tissue by a membrane, and is composed of refractive, 

 prismatic fibres exactly similar in optic properties to the fibres that 

 have been described in the suckers of Axine, Microcotyle, Qctocotyle, and 

 some other genera. In M. chiri this organ is, as already mentioned, 

 hemispherical in shape, and is separated from the cavity of the genital 

 atrium by a layer of connective tissue; moreover,, the external limiting 

 membrane of the organ reveals, on careful examination, on its outer 

 side a transition of its substance into the fibrous connective tissue 

 around. In M. sciaenae it is cyliridrical in shape, and appears 

 U-shaped in longitudinal sections, and forms the wall of the 

 posterior part of the genital atrium. For reasons already . stated 

 I am not able to make any definite statement on this head 

 concerning M. tnincata and M. reticulata ; but the latter species 

 seems to resemble closely M. sehastis in tliis respect ; while in the 

 former !:;pecies the compact, refractive mass of connective tissue is 

 more elongated in form. In Axine the compact connective tissue 

 already described around the terminal portion of the vas deferens is 

 continued on around the genital atrium. 



A genital atrium similar to those above described in most species 

 of Microcotyle seems, to judge from the figures and description of 

 Leuckart,'^ to be present also in Distomum heterophycs. As in this 

 endoparasite, so in Microcotyle I believe the genital atrium can be 



1). Leuokart— Die Parasiteu des Menschen. 2. Au&. -p. iOl et infra. 



