NOSEMA. 351 



294. Nosema bombycis Nageli. (Fig. 174.) 



Nosema bombycis, Nageli, 1857, p. 760. 



Panhistophyton ovatum, Lebert, 1858, pp. 149-86. 



Pebrine corpuscles, A. de Quatrefages, 1860, pp. 1-638 ; Pasteur, 

 1870. pp. 1-327. 



Microsporidie, Balbiani, 1884, pp. 150-68. 



Pebrine corpuscles, Wood-Mason, 1887, pp. 1-3 ; Pfeiffer, 1888, 

 pp. 469-86. 



Glugea bombycis, Thelohan, 1894, pp. 1425-7 ; 1895, pp. 357-8. 



Nosema bombycis, Labbe, 1899, pp. 106-7. 



Glugea bomJjycis, Toyama, 1900, pp. 1—40. 



Nosema bombycis, Minchin, 1903, p. 297 ; Leger & Hesse, 1907, 

 p. 6 ; Stempell, 1909, pp. 281-358 ; Minchin, 1912, pp. 411, 

 413-14, fig. 172; Omori, 1912, pp. 108-22; Kudo, 1913, 

 pp. 368-71; 1916, pp. 31-51; 1918, pp. 141-7; 1924 c, 

 pp. 69-76, figs. 1-39 ; fig. 757, text-figs. B2, D. 

 ^NosemM bombycis, Hutchinson, 1920, pp. 177-245, pis. i-xxvi. 



Nosema bombycis, Wenyon, 1926, p. 736, fig. 313 ; Knowles, 1928, 



pp. 324-30, figs. 72-5. 

 '\Nosemxi bom,bycis, Iyengar, 1929, p. 140. 



Nosema bombycis, Reichenow, 1929, pp. 1088—90, figs. 1085—9 ; 

 Kudo, 193i, p. 320, fig. 137, a, b ; Reichenow, 1935, p. 389, 

 fig. 43. 



Spore egg-shaped, with the anterior end somewhat narrower 

 than the other. It contains two vacuoles, one near the anterior 

 and the other near the posterior end. The single polar capsule 

 lies axially in the spore, occupying its whole length, and contains 

 a long polar filament wound spirally in its interior. The sporo- 

 plasm forms a cytoplasmic girdle round the polar capsule, 

 separating the two vacuoles and placed slightly nearer the 

 anterior pole of the spore. It contains at first a single nucleus 

 which later divides into two and then into four. When the 

 spores are ingested by a silkworm, the polar capsule ruptures 

 in the lumen of its gut, and the polar filament is extruded, 

 attaching the spore to an epithelial cell. This explosion of the 

 polar capsule can be artificially brought about by treating the 

 spores in some infected material with dilute acids or iodine 

 solution, or even by pressure between coversHp and the shde. 

 When germination of the spore takes place, the sporoplasm 

 or amoebula creeps by amoeboid movement along the polar 

 fiJament to an epithelial cell, which it invades. The planonts 

 multiply by binary fission (fig. 174, A), become distributed 

 throughout the body, enter tissue-cells, and become meronts (B). 

 These meronts are spherical or oval in shape, and divide 

 actively by fission (0) or by multiple division (D). The host- 

 cell finally becomes completely filled with schizonts. Each 

 meront ultimately develops into a spore {E). The spores are 

 set free by the disintegration of the host-cells, and are taken 

 with the food into the digestive tract of another host-larva, 

 where the two nuclei of the spore divide once, giving rise to 

 four nuclei (F). The polar filament is extruded (G) and later 



