744 ORDER: MICROSPORIDIIDA 



of the infected cells. The central part of the nodule is occupied by 

 pansporoblasts measuring 12 by 7 microns, and groups of sixteen spores 

 enclosed by a capsule. Each group is developed from one pansporo- 

 blast. The spores, which are ovoid, measure 5 by 2-5 microns. This 

 genus is evidently closely related to Thelohania, with which it may be 

 identical. 



Genus: Plistophora Gurley, 1893. 



The Microsporidiida belonging to this genus are found in fish. They 

 produce small white nodules in the tissues. The pansporoblast gives rise 

 to more than sixteen spores. 



Plistophora typicalis Gurley, 1893. — This parasite occurs in the 

 stickleback and other fresh-water fish, in which it gives rise to whitish 

 nodules in the muscles. These are 25 to 35 microns in diameter. Each 

 pansporoblast gives rise to numerous (more than sixteen) ovoid spores, 

 which eventually fill the nodules. Other forms are P. sttgoynyice of 

 Stegomyia fasciata {Atdes argenteus), and P. simulii of larvse of Simulium. 



Genus: Cocconema Leger and Hesse, 1921. 



The Microsporidiida belonging to this genus are characterized by their 

 spherical spores, which resemble cocci (Fig. 318). Leger and Hesse (1921) 

 have described four species from aquatic larvse or worms. 



C. micrococcus occurs in the fat body of the larvse of Tanyjnis setiger. 

 The spore has a diameter of 1-8 to 2 microns. 



C. polyspora occurs in the same host and in the same situation, but the 

 spores are larger, varying in diameter from 2 to 3-2 microns. 



C. octospora, the spores of which have a diameter of 2-1 microns, is 

 found in the intestinal epithelium of larvse of Tanytarsus sp. 



C. slavinae with spores 3 microns in diameter, occurs in the intestinal 

 epithelium of the aquatic worm, Slavina appendiculata. 



Kudo (19246) recognizes two other species — C. stempelli and C. miyairii. 



Genus: Mrazekia Leger and Hesse, 1916. 



The members of this genus produce cylindrical spores which, in addition 

 to a polar filament, possess a manubrium, which may be regarded as the 

 thickened proximal part of the filament (Fig. 317). The manubrium 

 occupies the central axis of the spore, and the filament is coiled round it. 

 Both the manubrium and filament are extruded. When spore formation 

 takes place, a single uninucleate cell or pansporoblast gives rise to one, 

 four, eight, or sixteen spores. 



M. caudata Leger and Hesse, 1916. — This species is parasitic in the 

 lymphocytes of aquatic worms of the genera Tubifex and Limnodrilus. 



