736 ON SOME TREMATODK PAItASITES, 



length. The testes, which lie in the middle line, one behind the 

 other, are very large, 1-69 mm. long by 59 mm. broad, roughly 

 erescentic or S-shaped, witli an irregular, indented outline. The 

 ovary is rounded or oval in shape, with a smooth outline, much 

 smaller than the testes, close in front of the anterior, and a little 

 to one side (the right) of the middle line. The ducts of the testes 

 run forwards, laterally placed, one on each side of the uterus, then 

 dorsal to the ventral sucker; they join at the base of the cirrus- 

 sac, and immediately enter the S-shaped vesicula seminalis. The 

 cirrus-sac is a muscular-walled, pear-shaped body of considerable 

 size; the prostate cells lie in its parenchyma surrounding the proxi- 

 mal part of tlie ejaculatory duct, into which their fine ducts open. 

 The oviduct leaves the ovary on its dorsal aspect, and soon gives 

 off Laurer's canal, which, after a short curved course, opens on 

 the dorsal surface near the middle line. Just distal to its junc- 

 tion with Laurer's canal, the oviduct expands into the ootype, and 

 here the duet of the yolk-reservoir opens into it. The next portion 

 of the female duet is frequently filled with sperms, and is the re- 

 ceptaculum seminis uterinum. The " shell-gland " or gland of 

 Melilis, is a lai'ge mass of elongated cells with fine duets opening 

 into the ootype. Not only the ootype, but also the yolk-reservoir 

 and Laurer's canal lie embedded in this mass of gland-cells. There 

 is no receptaculum seminis. The uterus, which is comparatively 

 very short, lies in the middle field of the body between the ovary 

 and the ventral sucker, being disposed in several transversely 

 placed coils, which do not reach laterally the intestinal limbs. The 

 final part of its course, lying dorsal to the ventral sucker, is fairly 

 straight. The vagina or metraterm has its muscular walls only 

 moderately developed. 



The follicles of tlie yolk-glands are small (0-069 x 0'056 ram.), 

 and exceedingly numerous. They form compact masses, lying, at 

 first, at the sides of the body, but, at the level of the posterior 

 testis, they begin to spread over to the middle, and beliind the 

 testes they fill up the whole field, forming a complete layer under 

 the surface of the body (Fig. 3). Anteriorly, they do not extend 

 beyond the posterior edge of the ventral sucker. There is a longi- 

 tudinal yolk-duct on each side, lying near the outer side of the 



