THE TELOSPORASIDA AND THE COCCIDIA PROPER 



161 



Fig. 24. Life cycle of the chicken coccidium, Eimeria tenella. A sporozoite (1) enters 

 an intestinal endothelial cell (2), rounds up, grows, and becomes a first gen- 

 eration schizont (3). This produces a large number of first generation mero- 

 zoites (4), which break out of the host cell (5), enter new intestinal endothelial 

 cells (6), round up, grow, and become second generation schizonts (7, 8). 

 These produce a large number of second generation merozoites (9, 10), which 

 break out of the host cell (11). Some enter new host intestinal endothelial 

 cells and round up to become third generation schizonts (12, 13), which pro- 

 duce third generation merozoites (14). The third generation merozoites (15) 

 and the great majority of second generation merozoites (11) enter new host 

 intestinal endothelial cells. Some become microgametocytes (16, 17), which 

 produce a large number of microgametes (18). Others turn into macrogametes 

 (19, 20). The macrogametes are fertilized by the microgametes and become 

 zygotes (21), which lay down a heavy wall around themselves and turn into 

 young oocysts. These break out of the host cell and pass out in the feces (22). 

 The oocysts then sporulate. The sporont throws off a polar body and forms 4 

 sporoblasts (23), each of which forms a sporocyst containing 2 sporozoites 

 (24). When the sporulated oocyst (24) is ingested by a chicken, the sporo- 

 zoites are released (1). (Original) 



the basement membrane and then pass 

 thru it into the lamina propria. Here 

 they are engulfed by macrophages and 

 carried by them to the glands of Lieber- 

 kuhn. They then leave the macrophages 

 and enter the epithelial cells of the glands, 



where they are found below the host cell 

 nucleus, i.e. , on the side away from the 

 lumen. We do not know how common this 

 method of penetration is among the coc- 

 cidia; Van Doorninck and Becker (1957) 

 first found it in E. necatrix of the chicken. 



