MICROSPORIDIA 341 



while to undertake a careful infection experiment by inoculation 

 to establish a definite fact. 



9) Viability of the microspondian spore. As to how long the 

 microsporidian spore would live under various circumstances, a 

 number of experiments have been carried on by several investiga- 

 tors of Noscnia bombycis and of N. apis. In both cases, the results 

 were obtained by feeding healthy larvse or bees with the treated 

 spores mixed with the food material. Spores of Noseiiia bombycis 

 contained in dried moths may retain their life for over a year if 

 kept at room temperature, while fermentation in the fecal matter 

 of the silkworm larvse destroys the spores w^ithin about two 

 months. White (1919) carried on a number of experiments with 

 Nosemu apis and obtained interesting results. 



Viability of the microsporidian spores of the species which 

 attack aquatic animals has not been studied at all. In this con- 

 nection, mention must be made of the interesting observation of 

 Goodrich (1928). A number of glass bowls in which Ganmiarus 

 pidex suffering from infection of Thelohania miilleri were kept, 

 were washed (but not steriHzed) and later used for rearing of 

 Ganinianis cJicvrcuxl which had been bred in the laboratory for 

 at least three or four generations. Some of the latter were found 

 to have become infected by the microsporidian, which fact could 

 only be explained by assuming that the spores of Thelohania 

 miilleri which had been formed in Gammarns pule.v survived for 

 at least six months and most likely thirteen months or more to 

 become the source of infection. 



10) Problems concerning the emergence of the sporoplasm as 

 the ama^bula. Although there had been a number of attempts to see 

 the changes which the spore undergoes when it is introduced 

 into the body of a new host animal, it was Stempell (1909) who 

 first succeeded in making out a more or less complete life-history 

 of the well-known microsporidian, Nosema bombycis. According 

 to this investigator, the mature spore has four nuclei in its sporo- 

 plasm. When the spore enters the host's gut, the polar filament is 

 extruded under the action of the digestive fluid and later becomes 

 detached completely from the spore. Through this foramen, the 

 sporoplasm which leaves two of its four nuclei behind, creeps out 

 of the spore membrane to become an amoebula in which two nuclei 

 fuse into one. This uninucleate amoebula ("planont") multiplies 

 actively by a binary fission or budding. It is capable of amoeboid 



