MICROSPORIDIA 



473 



spore in structure, but which is mostly obscure in vivo, because 

 of the minuteness of the object. 



When such spores are taken into the digestive tract of a specif- 

 ic host (Fig. 219), the polar filaments are extruded and perhaps 

 anchor the spores to the gut-epithelium. The sporoplasms emerge 

 through the opening after the filaments become completely de- 

 tached. By amoeboid movements they penetrate through the in- 

 testinal epithelium and enter the blood stream or body cavity and 

 reach their specific site of infection. They then enter the host 

 cells and undergo schizogonic multiplication at the expense of the 



Fig. 219. The life-cycle of Stempellia magna, X800 (Kudo), a, b, ger- 

 mination of spore in the mid-gut of culicine larva; c-k, schizogony; 

 1-p, sporont formation; q-t, formation of 1, 2, 4, and 8 sporo blasts; 

 u, sporoblast; v-x, development of sporoblast into spore. 



latter. The schizonts become sporonts, each of which produces a 

 number of spores characteristic of each genus. Some spores seem 

 to be capable of germinating in the same host body, and thus the 

 number of infected cells increases. When heavily infected, the 

 host animal dies as a result of the degeneration of enormous num- 

 bers of cells thus attacked. Such fatal infections may occur in an 

 epidemic form, as is well known in the case of the pebrine disease 



