SPOROZOA 



471 



times) esophagus, intestines, and ceca; and terminating fatally 

 in the majority of cases as a result of a series of combined factors, 



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Z 



13 



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Fig. 209. Coccidium tenellum, life-cycle: 1, Mature encysted Coccidium; 

 2, division into four sporoblasts; 3, sporoblasts elongated and spindle-shaped; 

 4, two sporozoites have developed in each sporoblast; 4 a, the cyst ruptured 

 and the sporoblasts and the sporozoites escaping; 5, epithelial cell of the in- 

 testinal tract; 5 a, 5 6, 5 c, 6, 6 a, stages in development within the cell, the 

 schizont stage; 7, schizont dividing to form merozoiites; 7 a, cell and schizont 

 ruptured and merozoi'tes escaping. These again infest the epithelial cells and 

 may repeat the cycle 5-7 a. Others produce the sexual stages 8 and 8 a to 11; 

 8, 9, infection of a cell with a merozoite and development of the macrogamete; 

 10, cell ruptured, exposing the macrogamete; 8 a, infection of a cell with a 

 merozoite and development of the microgametocyte; 9 a, formation of the 

 microgametes; 10 a, liberation of the microgametes; 11, fusion of the micro- 

 gamete with the macrogamete; 12, 13, 14, 15, development of the mature 

 encysted coccidium (Cole, Hadley, and Fitzpatrick). 



including probably the toxic action of microorganisms growing on 

 the mucous membranes, mechanical obstruction to swallowing 



