736 ORDEE: MICROSPORIDIIDA 



cytoj)lasmic bodies containing one or more nuclei, and multiplying by 

 binary fission or multiple segmentation. Large numbers of spores also 

 occur in the cells, and these often have the appearance of yeasts, cocci, or 

 bacilli, from which they may be difficult to distinguish, unless there is an 

 opportunity of causing extrusion of the polar filament. The presence of 

 the polar capsule and the extrusion of its filament can be rendered evident 

 by treating the spores with irritating fluids such as dilute acid, iodine 

 solution, or perhydrol, or by pressure between slide and cover-glass. In 

 the fresh condition, the filaments are best seen by dark ground illumina- 

 tion (Fig. 30). They may be stained by the silver nitrate methods 

 employed for demonstrating spirocheetes. Owing to the small size of the 

 spores of the majority of Microsporidiida, their detailed structure is difficult 

 to make out, while the varying efiect of different fixatives accounts for 

 the great diversity of the accounts which have been given. Stempell 

 (1909) described the spore of Nosema bombycis {¥ig. 312). He believed 

 that the polar capsule was an elongated body occupying the length of the 

 spore, and that the infective agent was in the form of an equatorial band 

 of cytoplasm surrounding the polar capsule in the space between it and 

 the spore wall. This cytoplasm was described as containing four nuclei. 

 Many observers have adopted Stempell's views regarding the structure of 

 the spore. Schuberg (1910), working with Plistophora longifilis, stated 

 that the polar filament was coiled on the inner surface of the spore wall, 

 and that the infective agent was in the form of a circular band of cytoplasm 

 containing a single nucleus. He maintained that a definite polar capsule 

 did not exist. Leger and Hesse (1916a), in the case of the- spores of 

 P. macrospora, N. bombycis, and other forms, described the polar capsule 

 as a large sac-like body occupying the greater part of the interior of the 

 spore, and the infective agent as a small mass of cytoplasm in a clear space 

 at the posterior end of the spore. The polar filament was coiled within 

 the polar capsule. The band of cytoplasm described by other observers 

 appeared to be nothing more than the retracted and distorted polar 

 capsule itself, and the supposed nuclei in it optical cross-sections of the 

 coiled filament. Kudo (1920) found that the spores of Stempellia magna, 

 which, on account of their large size, were very suitable objects of study, 

 were constructed as Leger and Hesse maintained (Fig. 313). The spores 

 of the genus Mrazekia, as described by Leger and Hesse (1916), are formed 

 on the same plan, with the exception that the proximal part of the polar 

 filament is thickened as an axial manubrium (Fig. 317). As regards the 

 minute structure of the smallest spores (Cocconema, Toxonema, Spirillo- 

 nema), nothing is known (Fig. 318). 



It is probably safe to assume that the spores of Microsporidiida have a 

 large polar capsule occupying the bulk of the interior of the spore, and 



