156 R. KUDO 



METHOD OF INVESTIGATION 



The study has been carried on fresh material, stained smears, 

 and section preparations. Fixation and staining are practically 

 the same as those (Kudo, '16) which were proved to be satisfac- 

 tory for the study of Nosema bombycis. Schaudinn's corrosive- 

 alcohol-acetic-acid mixture gave the best result, combined with 

 Giem^a's stain, followed by acetone dehydration, and by mount- 

 ing in cedar oil, Delafield's hematoxylin or Heidenhain's iron 

 hematoxylin, counterstained with orange G. or eosine. For the 

 extrusion of the polar filament, the writer has employed solely 

 the pressure method (Kudo, '13), as perhydrol could not be 

 obtained, which reagent, had it been used would have disclosed 

 distinctly the mechanism of the filament extrusion because of 

 the very large dimensions of one of the forms described here 

 (Kudo, '18). For staining the extruded polar filament, Fontana's 

 mixtures for staining Spirochetes were found to be well fitted as 

 before. This method brings out not only the polar filament, but 

 also the polar capsule of the spore as is stated later. 



Experimental infection of the larvae of Culex pipiens by No- 

 sema baetis failed to bring out any positive results. The experi- 

 ment will be repeated as soon as the writer obtains the material. 



THELOHANIA MAGNA KUDO, PARASITIC IN CULEX PIPIENS 



The larvae of Culex pipiens were collected on October 3 and 6, 

 1919, from a small pool filled with stagnant and muddy sewage 

 water located on the side of the shallow stream in the drainage 

 ditch near Crystal Lake at Urbana, Illinois. The larvae, as 

 well as the pupae and adults which metamorphosed later from 

 the larvae kept in the laboratory, presented the characters of 

 Culex pipiens, as descibed by Howard, Dyer, and Knox ('15). 

 On October 3, fourteen larvae and five pupae, and on the 6th, 

 twenty-four larvae and eighteen pupae were obtained from the 

 same pool, and were kept alive in glass jars in the laboratory. 

 These larvae presented somewhat variable appearances, although 

 they did not show any marked difference in their activity. Some 

 of the larvae appeared to be more opaque whitish, with more or 



