MICROSPOKIDIA — PARASITIC IN MOSQUITOES 169 



extremity through which the filament is extruded. This is not 

 the case with the present form. 



When the spore of the form under discussion is subjected to 

 mechanical pressure, it extrudes its polar filament from the 

 rounded, not from the truncate extremity. This has been dis- 

 tinctly demonstrated by staining the pressed spores by Fon- 

 tana's mixtures (figs. 73, 74). One or two granules usually une- 

 qual in size are generally found in the empty spore membrane. 

 These granules are most probably the nuclei of the sporoplasm 

 which have already been mentioned (compare fig. 69 with figs. 

 70 to 72). 



All of these observations lead the writer to consider the struc- 

 ture of the spore of Thelohania illinoisensis as follows : Inside of 

 the comparatively thick spore membrane, a large polar capsule 

 occupies about two-thirds of the intracapsular cavity, the remain- 

 ing space is partly filled with the sporoplasm which contains 

 one or two nuclei of unequal size. Thus on the whole, the 

 structure of the spore of the present form is similar to that of the 

 spore of Thelohania magna. 



The length of the filament extruded by means of mechanical 

 pressure and stayied with Fontana's mixtures varies from 60 to 

 97)U. The filament is more or less thicker than that of Nosema 

 bombycis (Kudo, '13, '16), or of N. baetis (figs. 113, 114). The 

 difference in length of the polar filament may be attributed 

 partly to the unequal effect of the pressure upon the spores, but 

 mainly is due to the fact that the filament is of various length in 

 different spores as can be seen in each spore before the filament 

 extrusion. The writer stated already that in fresh spores the con- 

 tents appear either to be uniformly granulated or to contain a 

 clear space near the center (figs. 62, 63). This diversity in the 

 appearance of the contents depends upon the length of the fila- 

 ment developed inside. When the filament is well developed and 

 fills the cavity of polar capsule, the spore does not show any clear 

 space (fig. 62). On the other hand, if the polar filament is not 

 well developed or short, it does not occupy the entire capsular 

 cavity, but leaves a clear triangular space near the posterior end 

 of the capsule. Usually the filament seems to be coiled in from 



