MICROSPOKIDIA — PARASITIC IN MOSQUITOES 173 



Multiple or delayed binary fission was not observed, which 

 besides binary fission is a very common process in the genus 

 Nosema. 



Young rounded sporonts become elongated and the protoplasm 

 condenses either toward one end or to the center of the sporont 

 (figs. 94 to 99). In most cases it assumes a girdle shape at the 

 middle of the spore, which shows a ring form in cross-section. 



The polar capsule seems to become differentiated nearly in the 

 center of the spore, best seen in spores stained with Fontana's 

 mixtures (figs. 109 to 112). A nucleus for the spore membrane 

 was not observed. Young spores (figs. 104, 105) are shghtly 

 larger than the mature ones (figs. 107, 108). .These two stages 

 show different affinities toward stains. Heidenhain's iron hema- 

 toxylin stains young spores usually dark black, leaving a small 

 clear space near the narrow tip, where a median longitudinal line 

 was seen (fig. 104), while the smaller and mature spores are 

 stained very faintly, even without differentiating the nucleus 

 (fig. 107). Giemsa stains the former uniformly pinkish, with a 

 centrally located deep red mass which appears in various forms 

 (fig. 105), but the latter is stained very faintly, exhibiting only a 

 blue mass near the center (fig. 108). 



One might think that these two forms correspond to the mac- 

 rospore and microspore, respectively, which have been reported 

 to occur in several other forms. It is, however, the writer's 

 opinion that they only differ in development, as various inter- 

 mediate forms between them show the gradation from the larger 

 and younger spores to the smaller and mature ones. 



The mature spore is 3 to 4/x in length and 1.5 to 2.5 /j, in breadth. 

 The polar filament, extruded and studied by exactly the same 

 method used for the two other forms, was 94 to 135/^ in length 

 (figs. 113, 114). 



The structure of the spore seems to be similar to that of Nosema 

 bombycis (Stempell, '09, and Kudo, '16), which was proposed as 

 the representative of the second type of microsporidian spores 

 (Kudo, '20). When mature the spore becomes covered with a 

 comparatively thick membrane which prevents the stains from 

 acting upon its contents. The polar capsule occupies the 



