340 RESEARCH IN PROTOZOOLOGY 



is improbable. Mattes thought of this and also wondered if the 

 spores had first to pass through certain carriers as was suggested 

 by some of the former workers on microsporidia. The determina- 

 tion of factors which favor infection rests upon the work of 

 future investigators. 



8) Problems concerning other modes of infection. Besides in- 

 fection through the alimentary canal, infection of ovarian eggs 

 which occurs in numerous species (Kudo, 1924), would result 

 in the hereditary infection of the next generation. This has clearly 

 been established in Nosema bombycis since Pasteur's investigation. 

 Marchoux, Salimbeni and Simond (1903) observed that Plis- 

 tophora stcgomyice is transmitted through ovarian eggs of the host, 

 Acdcs cegypti. Chatton and Krempf (1911) considered that since 

 Octosporea muscce-domesticce is found in the yolk of ova of the 

 host fly, the infection may be transmitted through the germ cells. 

 Schwarz (1929) has recently shown with her beautiful study 

 that the ovarian ^gg of the imago of Noimgria typhce was found 

 infected by the vegetative stage of Nosema nonagrice, which are 

 massed near the central portion of the infected ^gg. It seems pos- 

 sible that here also the young embryo may become infected in a 

 way similar to that of Bombyx' mori. 



In the opinion oi those who failed to obtain positive results by 

 experimental feeding with proper spores, there must be other 

 modes of infection. One of these is the direct entrance of mature 

 spores through the wounds. In the case of the silkworm, one fre- 

 quently finds wounds which develop at the time of molting on 

 the body surface, particularly of the prolegs. It was often sug- 

 gested that the spore may gain entrance to the body through such 

 wounds. It is, however, improbable that this occurs, since the 

 spore is immobile and so far it is not known to germinate in the 

 body-fluid of the host larva, although Sasaki (1897) reported that 

 he saw the emergence of the sporoplasm from the spore which 

 had been placed in the "blood" of silkworm larvae. In inoculation 

 experiments which, certain workers claimed, were successful in 

 bringing about positive infection, there is always a great possibiHty 

 that the spores gained entrance through the alimentary canal. As 

 he failed in the experimental infection of Ephestia larvae by feed- 

 ing the spores of TJielohania epJiestice, Mattes (1928) suspected 

 that the stings of the ichneumon-flies did not cause new infection, 

 but failed to obtain results by a few experiments. It seems worth 



