. Principles of economic zoo?logy. Zoology, Economic. 36 BRANCH PLATYHELMINTHES The trematodes are hermaphroditic, and the development may be either with or without a metamorphosis. The Liver-fluke (Fig. 23) is parasitic in sheep. The eggs pass down the bile-ducls of the sheep into the intestine, and from there to the exterior, when the embryo escapes by the separating of the lid, or operculum, from the egg-shell. The ciliated larva swims about in the water or remains in the damp vegetation until it comes in contact with a pond or land snail (Fig. 24). It then bores into the body of the snail,
. Principles of economic zoo?logy. Zoology, Economic. 36 BRANCH PLATYHELMINTHES The trematodes are hermaphroditic, and the development may be either with or without a metamorphosis. The Liver-fluke (Fig. 23) is parasitic in sheep. The eggs pass down the bile-ducls of the sheep into the intestine, and from there to the exterior, when the embryo escapes by the separating of the lid, or operculum, from the egg-shell. The ciliated larva swims about in the water or remains in the damp vegetation until it comes in contact with a pond or land snail (Fig. 24). It then bores into the body of the snail, where it develops into a sporocysi (Fig. 25), which produces rctlice. These rediw possess a mouth, a pharynx, an intestine, and an opening for the escupc of the young, which are internally produced. According to the season, these young are cennriae or redid, several generations of which may follow before the cercariw appear. The cercariw are adapted for aquatic Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Daugherty, Lewis Sylvester, 1857-; Daugherty, L. S. , Mrs. , 1859-. Philadelphia, London, W. B. Saunders
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