NOSEMA. 353 



into the epithelium, and the germ is safely poured out there 

 through the tubule of the filament, protected on the way from 

 the digestive ferment of the canal. The viscous fluid is the 

 amcebula itself. The view previously held of regarding the 

 polar filament as an attachment apparatus is thus con- 

 tradicted. 



Pathogenicity. — The organism causes a widespread disease, 

 in silkworms, known as pebrine, or by various other names in 

 different countries. In India it is locaUy known as Cota. 

 The disease spreads among the host-larvse and to the offspring 

 through the ova, causing disastrous epidemics and entailing 

 huge economic loss to the silkworm industry. The outbreak 

 of such disastrous epidemics in France and other countries 

 of Europe, in the middle of the last century, led Pasteur to 

 make his classical researches into the nature of the disease 

 and the mode of its control. 



Lightly infected larvae do not show definite symptoms, but 

 the heavily infected ones move about sluggishly, lose their 

 appetite, grow slowly, and succumb to death before pupation. 

 The cocoons spun by the infected larvee are very thin and 

 poor in quaHty. In advanced stages of the disease irregular- 

 shaped dark brown or black spots appear over the surface of 

 the host-body, particularly on the posterior ventral side. 

 The internal organs show a milky-white appearance due to 

 the presence of a large number of spores. 



The eggs of the host may become infected while developing 

 in the infected ovaries of the female moth, or the spores may 

 be taken by the host-larvse into their digestive tract with 

 contaminated food. The fsecal matter of the infected host- 

 larvse is the most dangerous source of infection, as the con- 

 tained spores are easily spread over the mulberry leaves on 

 which the silkworms feed. The disease can, however, be 

 controlled by eliminating both sources of infection. Infected 

 eggs and all stages of the host-insect showing the least sign 

 of infection must be destroyed as soon as possible by frequent 

 and careful inspection. 



Hutchinson (1920) has made a study of the disease as it 

 occurs in India. He has shown that pebrine spreads rapidly 

 in Indian silk farms and is a much more acute problem 

 than in Europe. He has further shown that light infections 

 can be identified by dissecting out the gut of the moth and 

 examining the posterior part of the colon, where fight infections 

 are usually located. A far greater proportion of infected 

 moths can thus be detected than by the Pasteur method. 



Habitat. — ^All tissues of eggs, larvse, pupse, and imagos of 

 Bonibyx morii Fabricius, 



SPOK. 2 A 



