MICROSPORIDIA^ — PARASITIC IN MOSQUITOES 165 



visible. Three different views of a stained spore in a smear 

 preparation are shown in figures 53 to 55, which exhibit the spiral 

 course plainly. 



The sporoplasm occupies the posterior portion of the spore. 

 In fixed preparations, a clear space appears around its side (figs. 

 48 to 55). Two nuclei occur, one large vesicular body, usually 

 with one or two karyosomes, is located close to the capsule, and 

 the other is near the posterior extremity of the spore, as was 

 stated before. 



As to the structure of the spore of Microsporidia, observations 

 of various investigators differ to a greater or less extent. These 

 will be briefly reviewed below, although the writer ('16, '20) has 

 already discussed them in his previous papers. 



A more or less generally accepted conception of the structure 

 of the microsporidian spores was proposed by Mercier ('08 a^ 

 '09) for Thelohania giardi. He observed that the spore is cov- 

 ered with a bivalve shell, each valve developing from a uninu- 

 cleate parietal cell; that the spirally coiled filament is contained 

 in a polar capsule which has its nucleus; that the girdle-shaped 

 sporoplasm with at first two, later four nuclei, surrounds the polar 

 capsule, and that a vacuole is present at each pole of the spore. 

 With this view, on the whole, Schroder ('09), Stempell ('09), 

 Fantham and Porter ('12, '14), Strickland ('13), Kudo ('16), 

 and others in other Microsporidia, agree, although their observa- 

 tions differ in details. 



On the other hand, Schuberg ('10) noticed in the spore of 

 Plistophora longifilis that the girdle-shaped sporoplasm (which is 

 ring-like in cross-section) contains only a single nucleus; that 

 the filament is coiled directly under the shell, mostly in the pos- 

 terior portion of the intrasporal space; that the nuclei observed 

 by other investigators are none other than the metachromatic 

 granules. The same view has been maintained by Weissenberg 

 ('11, '13), Omori ('12), and Debaisieux ('13, '15). 



Leger and Hesse ('16) described an interesting group of Micro- 

 sporidia under the generic name of Mrazekia. The spores are of 

 cylindrical form and have an entirely different structure from 

 other known genera. The polar filament is differentiated into 



