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undergoes farther development, has a considerable progeny of 

 its own, which escape and are known as cercarise ; here follows 

 under certain conditions, a separate existence not fully traced 

 out, but each cercarise can enter the viscera of a vertebrate, 

 when, in the liver, it attains its final development in the full 

 grown and sexually mature fluke. Let preparation No. 2 

 (in which only a portion of the uterus is shown) be 

 examined under the microscope, and the number, and dense 

 packing of the eggs be observed, we shall then be astounded 

 at the capabilities of increase made manifest, and no longer 

 wonder at the rapid spread of this parasite. 



From this knowledge of the reproduction of the fluke, we 

 may fairly deduce the following conclusions : — 



First. That the immediate progeny of the Fasciola is 

 innocuous to vertebrates, for certain metamorphoses or alter- 

 nations of generation must be passed through before it can 

 develope into the mature animal. 



Second. That the eggs (being provided with a hard shell) 

 having passed out of the Fasciola, may be blown about the 

 country and not develope until they meet with favorable con- 

 ditions. 



Third. That an estate may have the reputation of being per- 

 fectly free from fluke and yet the germs may be there in 

 myriads, ready to develope when favourable conditions arise, 

 may be through an overmoist season, may be through increase 

 in moUuscan life, may be through subtle influences not yet 

 explored. 



Fourth. That on a comparatively dry estate, having the 

 marshes well drained, the disease will never be very serious, 

 unless the seasons happen to be peculiarly mild and moist. 



Fifth. That molluscan, or aquatic insect life is necessary to 

 the development of the ciliated embryo, but it is not known 

 how long this embryo can live without moisture ; yet it has 

 been proved that infusorial life generally will bear extreme 

 dessication and yet survive. 



Sixth. That the offspring of flukey sheep are not born diseased; 

 but in consequence of the systems of the parents being dis- 

 ordered, the offspring may be more predisposed to attacks of 

 the worm, than those born of healthy sheep. 



It is stated in a report on fluke, which recently appeared in 

 the newspapers, that " when once a sheep becomes the host of 

 flukes it is doomed, as the parasite will continue in the liver 

 ducts until the life of the animal be exhausted." This does 

 not appear to be the fact, for I have it not only on the author- 

 ity of Cobbold, that the entozoon after entering the liver ducts, 

 passes into the biliary outlet, thence into the intestinal canal, 

 and is so expelled ; but also from the observation of practical 



