350 WILLIAM NICOLL. 



the outside of tlie oral sucker, but is apparently absent from 

 the ventral sucker. Within this is a much thicker layer of 

 muscles having mainly a longitudinal direction. Numerous 

 transverse fibres stretch across the body, especially in the 

 anterior region. 



The genital organs exhibit many features of peculiar 

 interest. The testes are two comparatively large bodies 

 measuring "55 — '60 mm. in diameter, situated not very far 

 from the posterior end of the animal. They are placed, side 

 by side, almost, in some cases quite, touching each other, 

 and practically on the same level. The obliquity, if any, is 

 very slight, the left testis being possibly a little in advance 

 of the right. They are compressed dorso-ventrally ; the 

 outline is roughly circular or polygonal, there being from six 

 to eight distinct, though not very deep, lobes on each. The 

 ovary lies a short distance in front of the testes, almost 

 median or very slightly to the left of the middle line. Its 

 outline is a regular oval, the long axis being transverse ; its 

 section is also oval, the long axis again being transverse. It 

 is smaller than the testes, from which it is separated by part 

 of the uterus, and measures 'SS by "25 mm. The yolk glands 

 are not of very great extent. They consist of a series of 

 unequal-sized follicles on each side of the body, extending 

 from the ventral sucker to the testes. Anteriorly they are 

 situated, close to the outer side of the intestinal diverticula. 

 They retain this position throughout the greater part of their 

 extent, but posteriorly they cross the diverticula veutrally, 

 and a few follicles are to be found on the inner side near the 

 testes. From this point the yolk-ducts run obliquely towards 

 the middle line in a narrow strip of connective tissue lying 

 between the testes and the median trunks of the excretory 

 system. The shell gland is of large size, lying close to the 

 ovary, dorsal and behind it. There is a small globular recep- 

 taculum seminis situated between the testes. Laurer's canal 

 is present. 



The vasa deferentia occupy a somewhat dorsal position in 

 the body. They are not symmetrically situated, one being 



