CNIDOSPORIDIA, MYXOSPORIDIA 521 



pfeifferi. Myxosoma cerebralis which attacks the supporting tissues 

 of salmonoid fish, is known to be responsible for the so-called "twist 

 disease," which is often fatal, especially to young fishes and which 

 occurs in an epidemic form. 



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. 523) 



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. 526) 



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. 522) 



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. 



Genus Ceratomyxa Thelohan. Shell-valves conical and hollow, 

 attached on bases; sporoplasm usually not filhng intrasporal cavity; 

 in gall-bladder of marine fish. Numerous species. 



C. mesospora Davis (Fig. 247, a). In the gall-bladder of Cestracion 

 zygaena; spores 8m in sutural diameter and 50-65ai wide. 



C. hopkinsi Jameson (Fig. 247, h, c). In the gall-bladder of Paro- 

 phrys vetulus, Microstomus pacificus and Citharichthys xanthostigmus; 

 trophozoites disporous; spores 5. 7-7. 5m in sutural diameter and 28.8- 

 39m broad. 



Genus Leptotheca Thelohan. Shell-valves hemispherical; in gall- 

 bladder or urinary bladder of marine fish and one in amphibians. 

 Numerous species. 



L. ohlmacheri (Gurley) (Fig. 247, d-j). In the uriniferous tubules of 

 kidney of frogs and toads; spores 9. 5-1 2m in sutural diameter and 

 13-14. 5m wide; with 2 uninucleate sporoplasms. 



Genus Mjrxoproteus Doflein. Spores pyramidal with or without 

 distinct processes at base of pyramid; in urinary bladder of marine 

 fish. 3 species. 



M. cordiformis Davis (Fig. 249, a). In the urinary bladder of Chae- 

 todipterus faber; spores 12 m by 10-1 1m. 



