332 RESEARCH IN PROTOZOOLOGY 



tain that the species helongs to Thelohania. But the generic and 

 especially specific determination will be accomplished only after a 

 careful study of section and smear preparations. 



It should be noted here that the difference in the length of ex- 

 truded polar filament possesses httle value in taxonomic considera- 

 tion, since various methods cause different degrees of filament- 

 extrusion. 



As to fixatives, those that have been mentioned for myxospor- 

 IDIA are commonly and satisfactorily used. Debaisieux (1928) 

 believes that Bouin's mixture is good for the vegetative stages 

 and Schaudinn's fluid for stages in sporogony and the spore, since 

 the latter is too violent and hence destructive to the vegetative 

 form. If the material is abundant, it is wise to fix it with various 

 fixatives. 



The sections should on the whole be thinner (2-6//) than those 

 for MYXOSPORiDiA and are more important than in the case of the 

 latter, as the developmental stages of the parasite are to be made 

 out with certainty by studying them only. 



Stained spores are noticeably smaller than fresh spores, due 

 partly to the shrinking through fixation and partly to the similar 

 refractivity of the spore membrane and Canada balsam. For this 

 reason, one must use care here also as in myxosporidia in com- 

 paring the dimensions of the spores under observation with those 

 of the spores of known species which have been observed under 

 various circumstances. 



Whether preserved spores can extrude their polar filaments or 

 not has not been thoroughly investigated. The writer treated the 

 spores of Noseina bombycis with ten and thirty per cent alcohol 

 for sixteen hours, and found that some of the spores extruded their 

 filaments upon addition of perhydrol or application of mechani- 

 cal pressure. 



PROBLEMS 



i) Tlie strucHire of the spore. Concerning the structure of the 

 microsporidian spore, a great diversity of opinion prevails. Appar- 

 ently there are several reasons for this state. In the first place, the 

 microsporidian spore is, as a rule, minute and covered by relatively 

 thick spore membrane which hinders a clear view of its contents. 

 Secondly, various fixing and staining methods do not give uniform 

 results even in one and the same species. On the other hand, the 



