244 



ZOOLOGY 



SECT. 



for a little time in the uterus ; eventually it is discharged, and, 

 passing down the bile-ducts of the Sheep into the intestine, 

 reaches the exterior with the faeces. Active development only 

 begins at this stage, and, three to six weeks later, a portion of 

 the egg-shell at one end becomes separated off as a sort of 

 lid or operculum, and gives exit to the contained embryo. This, 

 the ciliated embryo or miracidium (Fig. 190, A), is a somewhat 

 conical body covered all over with vibratile cilia, and with two 



past 



Fig. 190.— A—D. Development of Fasciola hepatica. A, ciliated larva ; 

 B, sporocyst, containing redise in various stages of development ; C, 

 redia, containing a daughter redia, and cercarise ; D, fully developed 

 cercaria. 6. o/>. birth opening ; ent. enteron of redia ; eye. eye-spots ; 

 gast. gastrula stage of redia ; germ, early stages in the formation of 

 cercarias ; int. intestine of cercaria ; mor. morula stage in the develop- 

 ment of cercarise ; oss. oesophagus ; or. su. oral sucker ; pap. head-papilla 

 of ciliated embryo ; ph. pharynx ; proc. processes of redia ; vent. su. 

 ventral sucker. (After Thomas.) 



spots of pigment, the eye-spots (eye), near the broader or anterior 

 end, which is provided with a triangular head-lobe (pap.). There 

 is an imperfectly developed intestine and a pair of flame-cells, 

 each with a fine canal opening on the surface. The rest of 

 the interior is filled with a mass of germ-cells. The ciliated 

 larva swims about in water, or moves over damp herbage 

 for a time, and perishes unless it happens to reach a Pond-snail, 



