740 ORDER: MICROSPORIDIIDA 



DETAILED DESCRIPTION OF CERTAIN GENERA AND SPECIES. 



Genus: Glugea Thelohan, 1891. 



The members of this genus are typically parasites of fish, but they 

 occur also in reptiles, frogs, and worms. Their characteristic feature is 

 that they occur as multinucleate plasmodia, as a rule embedded in or 

 infiltrating the tissues. The ovoid spores are produced from pansporo- 

 blasts, which are separated in vacuoles in the multinucleate plasmodium. 

 Sometimes they occur free in the body-cavity spaces. In this respect 

 they resemble the Myxosporidiida (Fig. 304, D). 



Glugea anomala (Moniez, 1887). — This is a parasite of the tissues and 

 organs of various fresh-water fish, chiefly the sticklebacks (Gasterosteus), 

 on the skin of which it gives rise to white nodules. On section such a 

 nodule is seen to have a fibrous capsule, within which is a multinucleate 

 cytoplasmic body. The central part of the nodule is occupied by numerous 

 ovoid spores, and these are also present in vacuoles in the peripheral cyto- 

 plasmic part. There are also present a number of large nuclei, which appear 

 to be the nuclei of the tissue cells which have been almost completely 

 destroyed. The spores are ovoid, and measure, as a rule, from 4 to 4*5 

 by 3 microns (Fig. 381, i). The polar filament may be 150 microns long. 



Germs : Nosema Nageli, 1857. 



This genus includes Microsporidiida, which in the vegetative phase 

 resemble the members of the genus Thelohania. The uninucleate pan- 

 sporoblast by a complicated process of development gives rise, however, 

 to a single spore. 



Nosema bombycis Nageli, 1857. — This parasite, which is the best- 

 known member of the genus, gives rise to the notorious silkworm disease. 

 Its life-history was studied by Stempell (1909). The infection is com- 

 menced by the small amoeboid body which escapes from the spore after its 

 ingestion by a silkworm Bomhyx mori (Figs. 312 and 314). It multiplies in 

 the intestine. The resulting parasites, which are uninucleate, pass between 

 the epithelial cells into the hsemocoele space, and thence into the various 

 tissues of the body, including the ovary. These stages were called planonts 

 by Stempell. They eventually enter the cytoplasm of cells and become 

 meronts, which multiply by binary fission, gemmation, or schizogony. 

 The products of this multiplication are often arranged in rows like a string 

 of beads. After the cytoplasm of the cell is exhausted, the uninucleate 

 forms become transformed into spores. Four nuclei are formed in each, 

 and two of these with some of the cytoplasm form the spore capsule, while, 

 of the two remaining, one takes part in the formation of the terminal 



