104 PHYLUM PROTQZOA THE SIMPLEST ANIMALS. 



oval or spherical cell with a nucleus. It lives a quiescent 

 life within the host cell, growing and absorbing nourishment 

 until the resources of the cell are exhausted. 



Life history. The coccidium enters the host cell as a 

 minute sickle-shaped body, pointed at the anterior end, and 



FIG. 47. Life history of Coccidium. After Schaudinn. 



I. Sporozoite; 2. Sporozoite entering a cell and becoming a trophozoite; 

 3-4. Schizont, forming merozoites ; 5. Merozoites entering another 

 cell ; 6 a . Merozoite forming macrogamete ; 6^. Merozoite forming 

 microgametes ; 7. Free microgamete ; 8-9. Fertilisation of macrogamete 

 by microgamete ; 10. Zygote within oocyst ; n. Formation of spores 

 within oocyst ; 12. Spores forming sporozoites. 



more blunt posteriorly. This is the Sporozoite stage of the 

 life history; it is liberated from a cyst (oocyst) when the 

 latter is swallowed by the centipede in its food. When 

 freed in the gut the sporozoite progresses by forward gliding 

 movements, alternating these by flexions, bending itself like 







