"GROUSE DISEASE"— COCCIDIOSIS 239 



The nucleus of the trophozoite is approximately central in position, or sometimes 

 to one side, and at first contains scattered granules of chromatin. It then becomes 

 somewhat vesicular (Figs. 8-11), and gradually the chromatin collects into a central 

 karyosome, lying within the nuclear sap (Fig. I2a). The position of the karyosome, 

 however, is not always centrally fixed ; it may lie to one side of the nucleus (Figs, 

 S, 10). 



The growth of the trophozoite naturally affects that of the host-cell. The 

 protoplasm of the latter becomes more and more tenuous, great hypertrophy of the 

 host-cell occurring. This condition is maintained for some time, and finally a limit 

 is reached and atrophy sets in, the nucleus of the host-cell then appearing as a 

 small, often crescentic mass (Figs. 10, 14) to one side of the film (Fig. 12) that 

 represents the host-cell. A clear space often intervenes between the parasite and 

 the enveloping epithelial film (Figs. 9, 11, 12). 



The trophozoite, having attained its full size (some 10/x to 12^ in diameter) 

 within the host-cell, proceeds to divide, and the result of its division is to increase 

 the number of parasites within the host. This stage in the existence of Eimeria 

 aviuin is known as the schizont (agamont), and the method of multiplication is 

 termed schizogony. 



The schizont (Fig. 12) is a more or less spherical parasite. At first it is uni- 

 nucleate (Fig. 12a), but soon its nucleus begins to fragment (Fig. 126). The division 

 of the nucleus of the schizont is of the nature of multiple fragmentation gchizo- 

 rather than of a series of binary fissions of the nucleus and karyosome ^°°^'" 

 (Figs. 13-18). The parasite is very small, and it is not easy to follow the cytological 

 details, even under the best and highest powers of magnification. Some of the 

 portions of chromatin in multiple fragmentation may sometimes appear connected 

 by thin strands (Fig. 13) for a short period, but the fragments soon travel to the 

 periphery of the schizont. The small daughter masses of chromatin, at first 

 homogeneous, gradually show diflferentiation, becoming minutely vesicular with a 

 dot of chromatin usually to one side (Figs. 14-16), but occasionally central. Thus 

 the nuclei of the future merozoites are forming their karyosomes early. 



The daughter nuclei having migrated to the periphery of the mother cell 

 (Fig. 16), the cytoplasm of the schizont concentrates around them, forming small 

 ovoid masses (Figs. 18, 19). The daughter-forms so produced are the merozoites 

 (agametes) which measure 6^ to 10/x in length. They gradually acquire a vermiform 

 shape, and arrange themselves around the remains of the protoplasm of the mother 



