414 



THE PROTOZOA 



Fio. 172. Diagram of the life-cycle of Nosema bombycit. All the stages to the left 

 of the dotted line are passed within a single cell, in which the parasite goes 

 through its sporogony after active multiplication by schizogony. 1, 2, Spores 

 showing the division of the two nuclei of the sporozoite ; 3, 4, germination 

 of the spore, showing first the extrusion of the polar filament, and then the 

 escape of the sporozoite, which leaves two nuclei behind in the empty sporo- 

 cyst and comes out with two nuclei ; 5, uninucleate planont ; 6, multiplication 

 of the planont by fission ; 7, 8, planonts, the latter entering the host-cell ! 



[Continued at foot of p. 415. 



