J24 TREMATODES. PHYLUM PL AT YHELMINTHES 



Fig. 88.— The life-histoiy of a liver fluke.— After Thomas. 



I DcvcloninK embryo in egg-case ; 2. free-swimming ciliated embryo ;3. sporocyst ; 3a. sheU of LimncBa 

 ■ <r«SS£ ;T ivision of sporocyst which sometimes occurs ; 5. sporocyst with redi^ formmg withm it 



6. redia wi'th'cercariae forming within it ; 7- tailed cercaria ; 8. young fluke. 



from the yolk glands, and spermatozoa. The material of the shell 

 is a quinone-tanned protein similar to the sclerotin of insects 

 (p. 227). The animal is probably as a rule self-fertilised. 



