MICROSPORIDIA PARASITIC IN MOSQUITOES 177 



Among insects, the adipose tissue is known as the most common 

 seat of infection. This pecuhar natm'e of Microsporidia does 

 not seem to have been explained. In almost all cases Micro- 

 sporidia were successfully transmitted from one host to another 

 by artificial infection per os. So it is strange to find uninfected 

 epithelial cells of the digestive tract, through or between which 

 the amoeboid sporoplasm must have passed into the body cavity 

 to reach the adipose tissue after having left the spore membrane 

 in the lumen of the alimentary canal. 



The nucleus of the infected host cell of Culex pipiens becomes 

 hypertrophied. The nucleus of the normal fat body is usually a 

 small, irregularly outlined, rounded body with a largest diameter 

 less than 8/j, and is compactly filled with deeply staining chro- 

 matic granules (fig. 59). The nucleus of heavily infected host 

 cell, however, becomes considerably hypertrophied, the diameter 

 reaching from 25 to 30/x (fig. 60). It also becomes vesicular and 

 contains deeply staining irregular chromatic masses which are 

 connected with one another and with the nuclear membrane. It 

 further shows one or two large masses. 



The infected adipose tissue of the Baetis nymph contained 

 numerous hypertrophied nuclei (figs. 116, 117), much larger in 

 number than the normal ones (fig. 115). Apparently dividing 

 nuclei have more frequently been observed in infected than in 

 normal tissue (fig. 117). The nucleus of the normal cell varies 

 from 4 to 10m in diameter, while those of the infected cells reach 

 25m in diameter. The large chromatic masses in the latter stain 

 less deeply by Giemsa than those small ones in the former. 



Although the nucleus of the host cell is not actually infected by 

 the parasites, its hypertrophy has been noticed in several cases 

 of the microsporidian infection. One of the most striking cases 

 was reported by Schuberg ('10) in the testicular cell of Barbus 

 fluviatilis infected by Plistophora longifilis. 



Abnormal mitotic divisions of the nucleus of fat body due to 

 microsporidian infection were reported by Mercier ('08) and 

 Debaisieux ('13). The active amitotic division of the nucleus, 

 distinctly noticeable in the present case, is most probably caused 

 by the parasites, and further, may be considered as a reaction 

 of the host cell against the parasite. 



