518 



PROTOZOA 



Inoculation experiments, according to these authors, show rabbits to 

 be slightly susceptible, inasmuch as the organisms cause slight fever 

 and remain for a long time in the blood without apparent harm. 



The mode of infection, the authors think, is probably through the 

 bite of ticks, members of the genus Dermacentor. These results have 

 not yet been corroborated. On the contrary, some good authorities 

 state that the bodies described by Wilson and Chowning as organisms 

 are artifacts, and that there is no evidence to show that the disease in 

 question is caused by a protozoan. 



Cnidosporidia. 



Subclass: Neosporidia. 



Order: Cnidosporidia. 



Suborder: Microsporidia. 



The Cnidosporidia, or, as the whole group is still sometimes called, 

 the myxosporidia, is one of the most populous and abundant groups 

 of the sporozoa, showing great structural variation as well as divergence 

 in mode of life. Nevertheless the members have as a group the follow- 



FlG. 158 



Nosema bombycis : 1 to 5, spore formation ; 6, infected follicle of testicle ; 7, spores ; a, b, fresh ; 

 c, d, treated with nitric acid. The acid causes them to swell up and increase in size by at least a 

 half, at the same time making the polar capsule distinct. In d the filament is extruded. (After 

 Balbiani.) 



ing well-marked characteristics: The trophozoite is amoeboid; spore 

 formation begins at an early period and proceeds continuously during 

 the growth of the trophozoite; the spores are produced endogenously 

 i. e., within the protoplasm of the trophozoite, and each spore always 

 possesses one or more very distinctive structures, "the polar capsules." 

 The Cnidosporidia are habitants of fishes, reptiles, arthropods, and 

 some other classes of animals. 



The microsporidia infest especially arthropods, causing often most 

 virulent epidemics. The most interesting member of this group is 



