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PROTOZOOLOGY 



filament, varies in number from one to four. Except in the family 

 Myxidiidae, in which one polar capsule is situated near each of the 

 poles of the spore, the polar capusles are always grouped at one end 

 which is ordinarily designated as the anterior end of the spore. Below 

 or between (in Myxidiidae) the polar capsules, there is almost always 

 a sporoplasm. Ordinarily a young spore possesses two sporoplasm 

 nuclei which fuse into one (autogamy) when the spore becomes 

 mature. In Myxobolidae there is a glycogenous substance in a vacu- 



FiG. 243. Sporogony in Myxosoma catostomi, X2130 (Kudo), a, sporont 

 or pansporoblast; b-h, development of two sporoblasts within the spo- 

 ront; i, a nearly mature spore; j-1, views of spore. 



ole which stains mahogany red with iodine and is known as the 

 iodinophilous (iodophile) vacuole. 



The Myxosporidia are exclusively parasites of lower verte- 

 brates, especially fishes. Both fresh and salt water fishes have been 

 found to harbor, or to be infected by, Myxosporidia in various 

 regions of the world. A few occur in Amphibia and Reptilia, but no 

 species has been found to occur in either birds or mammals. When 

 a spore gains entrance into the digestive tract of a specific host fish, 

 the sporoplasm leaves the spore as an amoebula which penetrates 

 through the gut-epithelium and, after a period of migration, enters 



