176 R. KUDO 



As Hesse saw the presence of polysporous sporonts, the species 

 may possibly belong to another genus and not to Nosema. 

 Auerbach ('10) placed this form into the genus Glugea. 



The writer, therefore, thinks that the Microsporidian under 

 consideration has not been observed before, and names it Nosema 

 baetis. 



THE EFFECT OF THE PARASITES UPON THE HOSTS 



As far as the observations up to the present are concerned, the 

 adipose tissue is the only seat of infection in any of these three 

 forms. 



In the larvae of Culex pipiens, the fat bodies composing the 

 general lining of the body wall and those lying freely in the body 

 cavity are heavily infected. The intermuscular adipose tissue 

 remains uninfected. This naturally explains why the infected 

 larvae were as active as the normal ones. 



Two cases of the presence of Thelohania illinoisensis were 

 studied only in smears; they do not furnish any data to be dis- 

 cussed here. 



In the nymphs of Baetis sp., infected with Nosema baetis, the 

 adipose tissue did not escape infection in any part of the body. 

 The muscular tissue in most cases was pushed aside by the 

 immense growth of the entire infected fat bodies, and showed 

 atrophy or poor development even though the effect was indirect. 

 In sections of a normal nymph, there are not only greatly vacu- 

 olated adipose cells, but also wide clear spaces in the body cavity 

 between tissues. In sections of heavily infected nymphs, how- 

 ever, the space of the body cavity was almost entirely filled 

 with greatly distended adipose cells which, when the animal was 

 alive, appeared as opaque white masses. The degeneration and 

 the dislocation of the muscular tissue and consequently less mus- 

 cular activity would plainly explain why the infected nymphs 

 were less active and more easily caught in the aquaria than 

 the healthy ones. 



Aside from such a form as Nosema bombycis which attacks 

 every non-chitinous tissue of Bombyx mori, the great majority 

 of Microsporidia are confined to a particular tissue of the host. 



