DISTOMATOSIS — LIVER FLUKE DISEASE — LIVER ROT. 



207 



varies with the temperature, a ciUated embryo {miracidium) is developed. 

 At a temperature of 20° to 26° C. the miracidium may be formed in ten 

 days to three weeks ; at a temperature of 16° C. the development takes 

 two to three months; at 38° C. it ceases entirely. Experiments have 

 shown that as long as these eggs remain in the dark the miracidium will 

 not escape from the egg-shell ; accordingly it will not escape during the 

 night. When exposed to the light, however, or when suddenly brought 



Fig. 148.— Embryo of the 

 common liver fluke {Fas- 

 ciola hepatic a), having into 



. a snail. X 370. (After 

 Thomas, 1883, p. 285, 

 Fig. 4.) 



Fig. 149. — Sporocyst 

 of the common liver 

 fluke which has de- 

 veloped from the 

 embryo, and con- 

 tains germinal cells. 

 X 200. (After 

 Leuckart, 1889, p. 

 109, Fig. 67 B.) 



Fig. 150.— Sporocyst 

 of the common liver 

 fluke, somewhat 

 older than that of 

 Fig. 149, in which 

 the germinal cells 

 are giving rise to 

 rediae. X 200. (After 

 Leuckart, 1889, p. 

 109, Fig. 67 C.) 



into contact with cold water, the organism bursts the cap from the 

 egg-shell, crawls through the opening, and becomes a — 



(c) Free-swimining ciliated miracidium (Fig. 148). — As already stated, 

 this organism is entirely different from its mother. It measures about 

 0*15 mm. long; is somewhat broader in its anterior portion than in its 

 posterior portion ; on its anterior extremity we find a small eminence, 

 known as a boring papilla ; the exterior surface of the young worm is 

 covered with numerous cilia, which by their motion propel the animal 

 through the water ; inside the body we find in the anterior portion a 

 simple vestigial intestine and a double ganglionic mass provided with a 

 peculiar pigmented double cup-shaped eye-spot ; in the posterior portion 



