COCCIDIOSIS 125 



is not enough. The parasite needs to complete its 

 own development and to assume a form capable of 

 passing to a new host, otherwise the race would come 

 to an end. Consequent on the physiological neces- 

 sities of the parasites, as well as to a reaction against 

 them on the part of the host, certain trophozoites 

 cease to become schizonts, but their latent poten- 

 tialities are aroused, and sexual differentiation begins. 



FIG. 28 DIAGRAM OF LIFE-CYCLE OF EIMERIA (CoccmiuM) AVIUM 



B-H, Illustrate the asexual reproduction (schizogony) of E. avium. 

 Epithelial host cells diagrammatically outlined. I-L, Illustrate 

 the production of sexual forms (gametogony). N-T, Illustrate 

 spore formation (sporogony). A, Sporozoite or primary in- 

 fecting germ, which penetrates the epithelial cell of the 

 duodenum of the host. B, Sporozoite curving on itself before 

 becoming rounded within the host cell. C, Young, growing 

 parasite. D, Fully grown parasite (trophozoite). E, Schizont, 

 with numerous daughter nuclei peripherally arranged. (Seen 

 in transverse section.) F t Schizont showing further differentia- 

 tion of merozoites. G, Merozoites, arranged like segments of 

 an orange, about to issue from host cell. H, Free merozoites. 

 /, $ , Young macrogametocyte with coarse granules. /, , 

 Young microgametocyte, with fine granules. /, 9 > Growing 

 female mother cell, showing chromatoid granules. /, 3 , Micro- 

 gametocyte, with nucleus divided to form a number of bent, 

 rodlike portions, the future microgametes. K, . , Macro- 

 gamete which has formed a cyst wall for itself, but has left a 

 thin spot for the entry of the microgamete. K, $ , Micro- 

 gametocyte, with many biflagellate microgametes about to 

 separate from it. L, Fertilization. One microgamete is shown 

 penetrating the macrogamete, while other male cells are near 

 the micropyle, but will be excluded. M, Fertilization. The 

 male pronucleus is lying above the female chromatin. The 

 other microgametes have degenerated outside the oocyst. N, 

 Oocyst (encysted zygote), with contents filling it completely. 

 0, Oocyst, with contents concentrated, forming a central 

 spherical mass. Many such cysts seen in infected cgecal drop- 

 pings. P, Oocyst, with four nuclei. Q, Oocyst, segmented to 

 form four round sporoblasts. (As seen in fresh preparations.) 

 R, Oocyst with four sporoblasts, which have grown oval and are 

 becoming sporocysts. S, Oocyst with four sporocysts, in each 

 of which two sporozoites have formed. T, Free sporocyst or 

 spore in which the sporozoites have assumed the most suitable 

 position for emergence 



