582 PROTOZOOLOGY 



oocysts are fed to chickens, the sporozoites emerge from the oocysts 

 and spores, in as early as 20 hours and are found on the surface of 

 the caecal mucosa. Toward the end of the second day, growing 

 trophozoites are found in the gland epithelial cells; they undergo 

 schizogony (Fig. 249, sch 1 ) by the middle of the third day. A single 

 first generation schizont is estimated to produce about 900 pyriform 

 merozoites which measure 2-4 /x by 1-1. 5/x and occur in the gland 

 lumen (we 1 ). As these merozoites invade the epithelial cells of the 

 fundi of the glands and become trophozoites, the infected host cells 

 increase in size, become rounded and no longer form a continuous 

 layer (tr). These trophozoites (Fig. 250, sch) grow to much greater 

 dimensions (up to as much as 45m in diameter) than those of the 

 first generation and multiply into merozoites (me 2 ) by the fifth day. 

 These merozoites are much larger and more elongated than those 

 of the first generation and measure 16m by 2/x. The haemorrhage in 

 the affected mucosa which begins usually with the growth of the 

 second generation trophozoites, increases in volume so that by the 

 fifth day after infection, a great portion of the mucosa sloughs off, 

 which coincides with the liberation of the merozoites. The merozoites 

 formed in the host cells located in the deeper part of the mucosa are 

 unable to become free and appear to grow into multinucleate forms 

 (ret sch). When the liberated merozoites enter epithelial cells, most 

 of them develop into macrogametocytes (ma) and microgametocytes 

 (mi), while comparatively small numbers become trophozoites and 

 form by budding a few, large third generation merozoites (me 3 ). 

 Mature oocysts (oo) are found on seven to eight days after infection. 

 Eimeria species in chicken (Tyzzer, 1929, 1932; Henry, 1931a); eco- 

 nomic importance (Foster, 1949; Brackett and Bliznick, 1950) ; path- 

 ological changes (Tyzzer, 1929, 1932; Mayhew, 1937); statistical 

 study of infections (Fish, 1931); mortality of hosts (Mayhew, 1933); 

 killing oocysts (Fish, 1931a); control measures (Andrews and Tsuch- 

 iya, 1931; Andrews, 1933); comparative oocyst production (Brackett 

 and Bliznick, 1950); in wild fowls (Haase, 1939). 



E. mitis Tyzzer (Fig. 248, I). In the anterior small intestine of 

 chicken; oocysts subspherical; 16.2m by 15.5m; sporulation in 48 

 hours (Tyzzer, 1929). 



E. acervulina T. (Fig. 248, m). In the anterior small intestine of 

 chicken, and in California quail (Henry); oocysts oval, 17. 7-20. 2m 

 by 13. 7-16. 3m; sporulation in 20 hours; associated with serious 

 chronic coccidiosis (Tyzzer, 1929). Effect on host (Moynihan, 1950). 



E. maxima T. (Fig. 248, n). In the small intestine of chicken; oo- 

 cysts oval, 21.5-42.5m by 16.5-29.8/x (Tyzzer, 1929). 



