CNIDOSPORIDIA, MYXOSPORIDIA 649 



supporting tissues of salmonid fish, is known to be responsible for the 

 so-called "twist disease" (Plehn, 1904), which is often fatal espe- 

 cially to young fishes and occurs in an epidemic form. Henneguya 

 salminicola invades the body muscles of various species of Pacific 

 salmon and produces opaque white cysts, 3-6 mm in diameter; it is 

 thus responsible for the so-called "tapioca disease" of salmon (Fish, 

 1939). Kudoa thyrsites (p. 655) attacks the body muscle fibers of the 

 barracouta in which the infected muscles become liquefied. This con- 

 dition is known as "milky barracouta" or "pap snoek" and may 

 affect as much as 5 per cent of the commercial catches (Willis, 1949). 

 Taxonomy (Gurley, 1894; Thelohan, 1895; Auerbach, 1910; Kudo, 

 1920, 1933); development (Kudo, 1920; Naville, 1927, 1930; Noble, 

 1944); species from North America (Gurley, 1894; Mavor, 1915, 

 1916; Davis, 1917; Kudo, 1920-1944; Jameson, 1929, 1931; Meg- 

 litsch, 1937-1947a; Fantham et ah, 1939, 1940; Noble, 1939, 1941; 

 Rice and Jahn, 1943), from South America (da Cunha and Fonseca, 

 1917, 1918; Nemeczek, 1926; Pinto, 1928; Guimaraes, 1931), from 

 Europe (Thelohan, 1895; CSpede, 1906; Auerbach, 1910, 1912; 

 Parisi, 1912; Jameson, 1913; Georgevitch, 1916-1936; Dunkerly, 

 1921; Petruschewsky, 1932; Jaczo, 1940); from Asia (Fujita, 1923, 

 1927; Chakravarty, 1939, 1943; Chakravarty and Basu, 1948). 

 The Myxosporidia are divided into three suborders: 



Largest diameter of spore at right angles to sutural plane; with 1 polar 

 capsule on each side; sporoplasm without iodinophilous vascuole. . 

 Suborder 1 Eurysporea 



Spore spherical or subspherical with 1, 2, or 4 polar capsules; sporoplasm 

 without iodinophilous vacuole. .Suborder 2 Sphaerosporea (p. 651) 



Sutural plane coincides with, or is at an acute angle to, largest diameter 

 of spore; 1, 2, or 4 polar capsules; sporoplasm with or without iodino- 

 philous vacuole Suborder 3 Platysporea (p. 655) 



Suborder 1 Eurysporea Kudo 



Spores laterally expanded; coelozoic in marine fish, except one species. . 



Family 1 Ceratomyxidae 



Spores less laterally expanded; in freshwater fish; histozoic or coelozoic. . 



Family 2 Wardiidae (p. 651) 



Family 1 Ceratomyxidae Doflein 



Spores are laterally prolonged and therefore sutural diameter is 

 smaller than width; 2 polar capsules at anterior margin; one on 

 each side of sutural plane; in one genus the spores contain three polar 

 capsules and the spore membrane is composed of three shell-valves. 



Genus Ceratomyxa Thelohan. Shell-valves conical and hollow, 



