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 fseces. 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 operctUum, 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 



pafi 



<rr3555 



D 



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

 B, sporocyst, euntaiiiing rediiy in various stages of development ; C\ 

 redia, containing a daughter redia, and cercarife ; Z), fully developed 

 cerearia. 6. oti. birth opening ; ent. enteron of redia ; eye. eye-spots ; 

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

 oeroarias ; int. intestine of cerearia ; mor. morula stage in the develop- 

 ment of cercariffi ; as. oesophagus ; or. su. oral sucker ; pap. head-papula 

 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 cihated 

 larva swims about in water, or moves over damp herbage 

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



