AILMENTS AND DISEASES 



occurred. They are present in all bodies of water and a careful observa- 

 tion of catches of freshwater fishes will almost always reveal some affected 

 with the postules or tumors produced by these protozoan parasites. 



Infusoria. This section of the Protozoa includes orders which con- 

 tain many parasitic genera. The countless host of Infusoria is divided 

 into 3 classes, 13 orders and 306 genera; of which 286 recognized species 

 occur in rivers and other freshwater, 76 species in pond water, 1 5 in marsh 

 water, 4 in ditch water, 13 in bogs, 17 in standing and stagnant water, and 

 I in spring water; while 80 species occur on or among aquatic plants, 35 

 in and on entomostraca, 16 in and on frogs, toads and salamanders, 14 in 

 molluscs, 5 in and on polyps and sponges, 4 in earthworms and tubifex, 

 18 in aquatic insects, and 4 are parasitic in and on fishes. These are the 

 following: — 



IcHTHYOPHTHiRiiD^. Thcsc Infusoria are probably the most frequent 

 and general forms of freshwater fish parasites. Small raised white spots de- 

 velop on the skin, which increase to larger blotches, spread over the sides, 

 head and fins, until the fish assumes the appearance of being dotted with 

 white and covered with slime. These extend to the mouth and oesophagus 

 and enter the ^ills, when the fish wastes away from loss of appetite, difficulty 



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