MICROSPORIDIA 



III 



to spare no tissues ; they form pansporoblasts, with or without envelopes, 

 in the interior of their body, which then grows still further, or the latter 

 is completely occupied by the pansporoblasts ; generally each pansporoblast 

 develops a great number of spores, rarely as few as four or eight. The spores 

 are remarkably small, are usually oval or pear-shaped, and surrounded by a 

 comparatively thick shell which probably always consists of two halves. 

 At one pole, the anterior one, there is always one pole-capsule with a 



FIG. 54, a, Section through 

 the abdominal wall of a silk- 

 worm, whose epithelial cells 

 contain Microsporidia (Nosema 

 bombycis) ; b, a spore the con- 

 tents of which are escaping ; 

 c e, sporulation stages. (After 

 Balbiani.) 



c. d. 



projectile filament, only observable by means of reagents. For this reason 

 some authors, since this fact has become known, have included the micro- 

 sporidia as Glugeida or as cryptocyst myxosporidia of the Blatter. The 

 spores, moreover, contain the " amosboid-germ," the exit of which from 

 the spore Balbiani had already seen. 



J/The manner of infection as regards the silkworms is well known ; it 

 occurs through the ingestion of the spores which reach the food already 

 contaminated by the excrements of infected silkworms ; probably an 



FIG. 55. Nosema bombycis, Naeg. Spores treated with 

 nitric acid, thus rendering the polar capsule perceptible, and 

 the filament has protruded itself from the one spore. (After 

 Thelohan.) 



increase of the parasites within the infected host takes place in some way 

 as yet unknown to us. This leads to the enormous infection of all the 

 tissues and organs that is so frequently observed, and to which the silk- 

 worms succumb ; or, on the other hand, the chrysalis stage and the 

 formation of cocoons is omitted because the salivary glands are also 

 attacked. When the infection is less extensive the silkworms not only 

 become pupae, but the moths emerge, 'and often deposit infected eggs, so 

 that the disease may also be congenital. Fortunately, however, eggs may 

 be recognised as infected under the microscope, as Pasteur has shown, 

 and as the little caterpillars may transmit the disease to healthy ones 

 they are therefore promptly destroyed. 



