ON A NEW SPECIES OF MALACOBDELLA (m. JAPOXICA.) \0d 



derived directly from the laterals as in the young specimen, but there 

 seems to be various interplaced canals. It gives off in its course several 

 anastomosing branches of various sizes, and such branches are connect- 

 ed laterally to those, which are derived from the laterals and occupy 

 the lateral portions of the body (fig. 3, net. v.). In the anterior and 

 middle regions the vessel can more or less distinctly be discriminated 

 from its branches by its position under the rbynchocœlom, though it is 

 often obscured in the middle region, where it makes strong windings 

 and have large branches. In the anal region, however, it is im- 

 possible to trace the vessel as a single canal as in the anterior region, 

 for it becomes slender connecting canals, traversing between the two 

 large vessels (fig. 5, d. v.) above the intestine, and does not take the 

 median position. These two vessels are continuations of those which 

 are observed in other portions on the side of the dorsal vessel, being 

 fused together with the latter at several points (fig. 4, d. v.). 

 Laterally these two vessels are continued to a network of small canals, 

 situated in the lateral part of the body, as in the anterior part (fig. 

 4 & 5, net. ic). At the end of the body they are united into a single 

 canal and the lateral networks nearly disappear. Such a single canal 

 divides, however, into two, immediately in front of the anus, and each 

 branch enters the acetabulum to communicate with the lateral of its 

 own side, and forms two curved vessels (fig. 4, ac. v.), which run 

 along the edge of the acetabulum. Besides the horizontal windings, the 

 two large vessels above stated make in their posterior portion strong 

 vertical undulations along the sides of the digestive canal, approaching 

 very near the lateral (fig. 4, /. v.), which is situated on the ventro- 

 lateral edge of the intestine, yet there are only a few direct con- 

 nections between the laterals and the large vessels in consideration. 

 In the anterior region, some of the branches of the dorsal vessel always 

 run among the muscular fibres of the proboscis sheath, and com- 

 municate at several points with the dorsal itself. These branches 

 already exist in young specimens, whose vascular system is furnished 

 with only' a few anastomosing branches in the tip of the head. The 



