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II. REPRESENTATIVE PLATHYELMINTHES 



Class TREMATODA 



IMPORTANT REFERENCES 



In addition to the general works of Braun, Leuckart, Neumann, Railliet, 

 et al., see, Benham, '03; Braun, '89; Gamble, '96; Loos, '94; Stiles, '04; 

 Ward, '04. 



Order MONOGENEA 



Almost exclusively ectoparasites. With more than two suckers 

 and often with hooks. Development direct and without change 

 of host. Take as an example : 



Polystomum integerrimum — Lives in bladder of frogs. 



Description — Mature fluke .5cm. long by .15cm. wide, flattened, 

 with four eye spots on anterior end. Alimentary canal bifurcate, 

 the two branches connected by many cross-canals. Six suckers at 

 posterior end and between them attachment hooks. 



Life history — Eggs laid in water by protrusion of body of the 

 parent through urinary aperature of the frog. About 1000 eggs in 

 ten days. After about six weeks free swimming ciliated larva hatches, 

 but perishes if it does not meet a tadpole within twenty-four hours. 

 If fortunate, attaches to gills of the tadpole, loses cilia, and remains 

 eight to ten weeks, forming suckers from behind forwards. When 

 tadpole transforms the Polystomum enters oesophagus, passes down 

 intestine and enters bladder of the frog. Said to require three years 

 to reach sexual maturity. 



Diplozoon paradoxum — Well named, for one of the most puzzling 

 of animal forms. Adult X-shaped organism made up of two fused 

 individuals. Eggs on gills of various small fish give rise to ciliated 

 larvae which, if they succeed in attaching to a minnow develop into 

 a larval form long known independently under generic name Diporpa. 

 These Diporpa develop and mature sexual organs only by conjuga- 

 tion in pairs. Fuse at point of contact and within each complete 

 sets of genitalia develop. 



