842 TREMATODA. 



PLATE XII 



Life History of a Trematode. 



Fig. 1. — Fertilised ovum, ciliated embryo, sporocyst, redia, cercaria 

 (developed as an internal bud in the interior of the 

 sporocyst or redia), encysted form, fluke. 



Ovum of Distoma Hepaticum (mag.) 

 Fig. 2. — Observe the shell opening by a lid, and the embryo 

 escaping through the opening. 



Ciliatei) Embryo of Distoma Hepaticum. 



Fig. 3. — Observe the cilia, the cross-like eye spot, and the large 

 touch papilla projecting from the broad anterior end. 



Sporocyst (mag.) 



Fig. 4. — Observe the ciliated coat cast off, the internal buds 

 developing into cercariae, and the alimentary canal 

 without an anus. A highly organised sporocyst is 

 called a redia. 



Tailed Cercaria. — Fig. 5. 



Amphibtomum Conicum. 



Fig. 6. — Observe the conical form, the anterior and posterior sucker, 

 the alimentary canal without an anus, and the much 

 ramified Avater vascular system. 



Organisation of Distomum Lancbolatum. 



Fig. 7. — Observe the lanceolate form, oral sucker (0. S.), ventral 

 sucker (V. S.), the bifurcating alimentary canal (A. C), 

 the testes (T.), uterus and female organs, and the water 

 vascular system (W. V. S.). 



Distomum Hepaticum. 



Fig. 8. Natui-al size. Near the anterior end the ventral sucker is 

 shown. 



DIPTERA. 



Gastrophilus Equi. 



Fig. 9. — Male and female (nat. size). 

 Fig. 10. — The larva or bot. 



Fig. 11. — The pupa from which the fly has emerged. 

 Fig. 12. — Part of the stomach of a horse, with larvae (bots) living 

 in its interior. 



TEACHEAKIA. 



Pentastomum T^nioides. 

 Fig. 13. — Internal organs. 



Pentastomum Denticulatum. — Fig. 14. 



