0N r A NEW SPECIES OF MALACOBDELLA (M. JAPONICA). 107 



having diverticula. The anus opens dorsally nearly at the center of 

 the acetabulum. 



The rhynchocceloni of the present species differs greatly from that of 

 ill", grossa by being short (pl. VII, fig. 1). v. Kennel says : the structure 

 in the latter species "bis zum letzten Drittel des Köpers deutlich sichtbar 

 bleibt," and " sondern jene (Biegungen des Darmes) manchmal schneid- 

 end bis gegen das Hinterende des Thieres hin, wo sie sich bei macros- 

 copischer Betrachtung verlieren." Bükger remarks also : " Malacobdel- 

 la ist mithin eine Angehörige der Holorhynchocœlomier." Thus 

 in M. grossa it is obvious that the rhynchoccelom reaches the posterior 

 end of the body, but the Japanese species is never a " Holorhyncho- 

 cœlomier." The rhynchoccelom extends in the first two-thirds of the 

 body and its posterior extremity is macroscopically distinctly observed. 

 Different from M. grossa, a microscopical examination shows that it does 

 not extend farther backward than can be observed from the surface. It is 

 slightty winding, being situated on the dorsal side of the digestive canal, 

 but does not follow the curvature of the latter precisely (fig. 1). The 

 proboscis, which has nearly the same length as the sheath, is 

 distinguished into the anterior long glandolar portion and the posterior 

 short bulb-like cavity, followed by n strong retractor. The wall of the 

 bulb is much thinner than that of the anterior division. The inner 

 epithelium consists of low cylindrical cells, without glandular elements, 

 and is not "ganz flaches Pflasterepithel" as v. Kennel noticed. 

 The retractor muscle is a strong bundle of longitudinal muscle fibres, 

 which reaches the hind end of the rhynchoccelom. Its posterior ex- 

 tremity not only reaches the narrow end of the latter, but passing through 

 its wall enters the parenchymatous tissue surrounding it and is soon 

 reduced in bulk. Of the termination of the retractor fibres of il/, grossa, 

 it is said that they, after passing through the end of the rhynchoccelom, 

 rise dorsad to be affixed to the muscular body wall, but the case is 

 quite different in the present species. Instead of proceeding dorsad, 

 they bend rather ventrad, and no connection with the muscular body 

 wall is observed, except their crossing the dorso-ventral fibres, and 



