tubular organelle, the polar filament (or a rudiment thereof). 

 Upon ingestion by a suitable host, the polar filament uncoils 

 and extrudes with extreme rapidity from the spore, remaining 

 attached anteriorly. The sporoplasm is expelled through 

 the polar filament, which apparently evaginates as it ex- 

 trudes from the spore. If the spore is near the gut wall 

 and is properly oriented, the wall is penetrated by the 

 violently extruding filament and the sporoplasm is injected 

 into a host cell as though by a hypodermic syringe. There 

 it multiplies and develops in direct contact with the host 

 cytoplasm, there being no parasitophorous vesicle. After a 

 large number of vegetative parasites have been produced by 

 cycles of multiplicative development (merogony) , they trans- 

 form into sporonts , or cells which give rise to spores after 

 a set number of divisions characteristic of the species 

 (sporogony) . 



Sprague (1977), considering the protozoa a polyphyletic 

 group, assigned the microsporidia to a new phylum, Microspora, 

 consisting of two classes, Rudimicrosporea and Microsporea. 

 The typical microsporidia, including the subject of this 

 dissertation, are assigned to the order Microsporida, one 

 of the two orders of Microsporea (Levine et al. , 1980). 



