MICROSPORIDIA 329 



visible, but the sporoplasm is indistinct. As to the presence of a 

 polar capsule and the position of the sporoplasm, opinions vary 

 even in those supposed to be one and the same species. 



The fundamental characteristic of the microsporidian spore is 

 the presence of a single polar filament (two in dicnidea). In a few 

 species with large spores, it is visible in life (as in St cm pell ia 

 magna), but ordinarily the polar filament is only to be noted when 

 extruded from the spore. When extruded, it is conspicuous in that 

 it is extremely fine and long. In an extreme case such as in Plis- 

 tophora longifilis, it reaches a length of 500 microns. The polar fila- 

 ment is of uniform thickness throughout. In genus Mrazekia, 

 however, it apparently is made up of two portions : a more or less 

 thick basal rod-like structure ("manubrium") and the other uni- 

 formly fine filament. In the other genera, the end with which the 

 filament is attached to the spore is thickened to form a basal 

 granule ("Polkorper," Zwolfer, 1926; "corp polaire," Debaisieux, 



1928). 



The end from or near which the polar filament becomes extruded 

 is ordinarily known as the anterior end, while the opposite the 

 posterior end. If the spore is pyriform in form, the narrow end is, 

 as a rule, the anterior end. 



MATERIAL 



The MICROSPORIDIA are typically cytozoic. Recently, Weissen- 

 berg (1926) found that Nosema himicleatum develops in the non- 

 cellular ground substance of the tiuiica elastico-muscularis of the 

 mid-gut of Tipiila gigantca (larva) and this seems to be the only 

 known form which attacks intercellular space of the host's tissue. 

 Up to the present, there have been known two species of micro- 

 SPORiDiA which attack every tissue of the host. They are the well- 

 known Nosema homhycis and A^ nonagrio! parasitic in the larva, 

 pupa and adult of Nonagria typJicu (Schwarz, 1929). Aside from 

 these two species, the microsporidian species appear to be confined 

 in a few tissues and the majority of species attack only the cells of 

 a particular tissue. 



In the case of a mild infection, no macroscopic changes appear 

 on the host's body. When the infection is very severe, conspicuous 

 changes are to be noted in the host's body. In small aquatic 

 arthropods, the heavily infected animals will easily be detected as 

 suffering from microsporidian infection by an opacity which is 



