BY S. J. JOHNSTON. 301 



The lateral, vaginal swellings are formed by a large number of 

 papillfe, perforated by fine canals(Fig.28), which, after a very 

 short course, open into a fairly wide sperm-reservoir(Fig.23), 

 situated, one on each side, just under the swellings. From these 

 reservoirs, a wide vaginal tube on each side runs backwards and 

 inwards, to open into the anterior lateral yolk-duct. On one 

 side only, in the specimens sectioned, was the vaginal tube filled 

 with sperms; that on the other side was empty. 



The yolk-glands are very extensively developed, stretching from 

 a level just behind the pharynx, right back into the caudal disc. 

 They consist of a large number of oval, closely-packed follicles, 

 and stretch across the whole dorsal surface of the body, except in 

 those cases where the uterus is loaded with eggs. When this is 

 the case, the uterus occupies the middle area of the dorsal surface, 

 and the yolk-glands are pushed to the sides, for a part, at least, 

 of their course(Figs.24, 25). The anterior and posterior lateral 

 yolk-ducts, on each side, join at a level just behind the ovary, to 

 form two transverse ducts which run inwards and unite to form 

 a large yolk-reservoir that lies behind the ovary. A single duct 

 from this reservoir opens into the oviduct near the ootype. The 

 geni to-intestinal canal enters the oviduct close to the opening of 

 the yolk duct, and runs, first posteriorly, then, bending sharply, 

 it proceeds transversely across the body, in a gently curved 

 course, to open into the intestine on the same side, i.e., the right 

 (Fig.27). 



The wall of the canal passes obliquely through the wall of the 

 intestine, and projects a little into the lumen(Fig.2), so that a 

 kind of valve is formed, which would prevent substances passing 

 from the intestine into the canal. 



The eggs are oval, bright yellow in colour, large and thick- 

 shelled, 0-206 mm. long, by 0-095 mm. broad; not so large as the 

 size {0-22-0-24 x 016 mm.) given by Braun(4, p.499) for the eggs 

 of P. integerrivium. 



Literature, 2, 4, 17, 27, 28, 30, 35, 75, 79, 93, 104, 105. 



