134 PRACTICAL PAEASITOLOGY 



placed diagonally in the middle line in front of the testes. The testes, in 

 this parasite, are deeply indented, the anterior gland invariably showing 

 four, the posterior gland five, lobes. The excretory bladder, which runs 

 in an S-shape between the testes, is nearly always distended in O.feli- 

 neus. In the lancet-fluke it is rarely seen, as it collapses in the fixed and 

 coloured specimen. When visible, however, it appears as a straight 

 tube running from front to back. In both species, the position of the 

 yolk-glands is exterior to that of the stomach-tubes, and in the fluke 

 of the cat the yolk-glands are both absolutely and relatively longer 

 than in the lancet-fluke. In the fluke of the cat they extend, rather 

 across than lengthwise of the body, and are united in groups which 

 are only visible in specimens in which contraction is slight. In the 

 lancet-fluke, the follicles of the yolk-glands are rounded and they are 

 not arranged in groups. The course of the uterus is not the same in 

 both species. In the fluke of the cat it is restricted to the field 

 bounded by the stomach-tubes ; it runs across this field in folds, which 

 extend forwards from the ovary to the ventral sucker, leaving the 

 hinder third of the body space entirely free. In the lancet-fluke, the 

 uterus commences in the neighbourhood of the ovary and runs in close 

 transverse folds (which occasionally extend beyond the central field) 

 backwards, until it reaches the hinder edge of the body. Here it 

 makes a turn towards the front, throwing out shorter folds towards 

 the sides, until it reaches a position between the ovary and the 

 posterior testis, whence it passes between the testes and, after forming 

 a few more folds in the neighbourhood of the ventral sucker, it finally 

 reaches the surface of the body close to the cirrhus pouch. If we 

 imagine the uterus free from folds, it would run directly from back to 

 front in 0. felineus, while in D. lanceatum it would take a U-shaped 

 course, the one branch (called " descending") extending in a backward 

 direction until it merges into the " ascending " branch, which runs 

 forward to the genital opening. The two branches are largely dis- 

 tinguishable by the difference in colour of the eggs which they contain. 

 The descending portion of the uterus contains the young eggs, which 

 are a light brown in colour and which become gradually darker until, 

 in the ascending branch, they are a brown-black. The difference in 

 shape between the eggs of the two species should be carefully noted 

 (figs. 32, 33). Another point of dissimilarity lies in the nature of the 

 male sexual organs. D. lanceatum possesses a distinct organ of 

 copulation, the cirrhus with the cirrhus pouch ; while in 0. felineus 

 this function is fulfilled by the terminal portion of the vas deferens, 

 which, as it is usually filled with spermatozoa, is easily made out close 

 to the ventral sucker. 



The points of difference which have been described between the 

 lancet-fluke and the fluke of a cat, may be taken as characteristic of 



