TREMATODES 183 



seminis present; the uterus is a long tube, containing eggs; yolk glands 

 either branched or compact: parasitic as adults in the intestine and 

 other hollow organs of vertebrates; over 1,700 species, the family rela- 

 tionships of which are as yet more or less obscure. 

 Key to the genera of Distomata here described: 



Oi Hermaphroditic distomes. 

 &i Ovary in front of testes. 

 Ci Uterus does not extend back of testes. 

 di Intestinal trunks with lateral projections ; ovary and testes branched. 



1. Fasciola 

 dj Intestinal trunks without lateral projections. 



ei Genital pore back of acetabulum 2. Paragonimus 



€2 Genital pore not back of acetabulum, 

 /i Mouth surrounded by spines. 



ffi A single row of spines 3. Echinostoma 



g^ A double row of spines 4. Stephanochasmus 



/a No spines around the mouth. 



^1 Excretory vesicle winds between the testes 5. Ampiiimerus 



g^ Excretory vesicle does not wind thus 6. Azygia 



C2 Uterus extends back of testes. 



di Mouth surrounded by 6 long papillae 7. Bunodeba 



ds No such papillae. 



61 Intestinal trunks reach to about the middle of the body. 



/i Yolk glands branched and in middle area of body 8. Rexifer 



/z Yolk glands compact and at end of body 13. Microphallus 



62 Intestinal trunks reach the rear end of body, 

 /i Genital pore near front end of body. 



gi Genital pore near pharynx ; in lungs of frogs and toads. 



9. Pneumongeces 



g^ Genital pore in front of oral sucker .10. Cephalogonimus 



fi Genital pore near acetabulum ; yolk glands compact and lobate. 



^1 Testes 2 in number 11. Gorgoderina 



^2 Testes 9 in number 12. Gorgodera 



62 Ovary behind testes. 



Ci Hinder end of body not telescopic 14. Halipegus 



C2 Hinder end telescopic 15. Hemiurus 



hs Ovary between the testes 16. Clinostomum 



C2 Unisexual distomes 17. Schistosoma 



1. Fasciola L. Body broad and leaf-like, covered with minute 

 spines and with a short conical anterior end at the base of which is the 

 acetabulum; intestine, excretory vesicles, and genital glands richly 

 branched; genital pore in front of acetabulum: in liver of herbivores; 

 about 4 species. 



F. hepatica L. Liverfluke. Length 18 to 50 mm.; width 4 to 13 

 mm.; conical anterior end distinctly set off; body thin and flat: in the 

 gall passages of cattle, sheep, man, and other animals, causing 

 liver rot, which is often very fatal to herds; intermediate host a snail of 

 the genus Lymnaea ; cosmopolitan, but rare in America, except in southern 

 Texas, in Florida, and a few other places. 



