330 RESEARCH IN PROTOZOOLOGY 



characteristic. The pathological changes of the host body due to 

 severe microsporidian infections, which had been known up to 

 1924, have been summarized elsewhere, to which the reader is 

 referred (Kudo, 1924:35-40). 



As to the sources of material for a laboratory study, larvae of 

 various genera and species of mosquito may be conveniently ob- 

 tained. Other dipterous larvae, as, for example, Simulhim larvae, 

 and crustaceans such as Cyclops or Gammariis, are also excellent 

 material to study. Examination of the gut of a number of honey- 

 bees will in most cases result in finding Nosema apis. In the locaH- 

 ties where the silkworms are raised, one finds, even at the present 

 day, little difficulty in discovering some larvae infected by Nosema 

 bombycis, the most widely studied microsporidian. Among the fish, 

 North American smelt (Osmerns mordax) has been found to be 

 a frequent host to Glugea sp. (probably hertwigi). This micro- 

 sporidian forms cysts in various parts of the intestine of the host. 

 As to the known microsporidia and their hosts, the reader is re- 

 ferred to Kudo (1924). 



METHODS 



The methods described for myxosporidia also hold good on the 

 whole for microsporidia. Seen under a low magnification, micro- 

 sporidian spores appear uniform in size, shape and appearance, are 

 highly refractive and are as a rule heavier than other matter pres- 

 ent in the field so that they are always found in the lowermost 

 focal plane. A clear space or vacuole may be found in many species 

 at one pole of the spore, but it cannot be depended upon as a 

 characteristic of a microsporidian spore, since a similar appear- 

 ance has been recognized in the spores of haplosporidia or in 

 yeast cells. To casual observers, certain protophyta may some- 

 times appear as microsporidian spores. Mercier distinguishes a 

 microsporidian spore from a yeast cell by staining . with Ziehl's 

 fuchsin followed by decoloration with a weak sulphuric acid solu- 

 tion. The former then remains bright red, while the latter become 

 colorless. Sturtevant reported that the pollen grains of corn con- 

 tained oval starch granules similar in size and appearance to the 

 spores of Nosema apis. In such a case, an addition of iodine solu- 

 tion would reveal the real nature of the object. 



The most important characteristic of the microsporidian spore is 

 the presence of the polar filament which can be extruded compara- 



