1911] 



on Grouse Disease. 



19 



Fig. 1. — Diagram of the life-cycle of Eimeria (Coccidium) avium. 



A-B illustrate the asexual reproduction (schizogony) of Eimeria {Cocci- 

 dium:) avium ; I-L illustrate the formatton of sexual forms (gametogony) of 

 E. avium ; N-T show the formation of the oocysts (cysts) and sporocysts 

 (spores) of E. avium (sporogony) ; A, sporozoite or primary infecting germ, 

 which is penetrating an 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 ; E, parasite (schizont) 

 with its nucleus divided (seen in transverse section) ; F, parasite forming 

 merozoites, i.e. daughter forms of the dividing parasite ; G, group of mero- 

 zoites, arranged like the segments of an orange ; H, free merozoites. I 9 , 

 young female mother cell with coarse granules ; I S , young male mother 

 cell with fine granules ; J ? , growing female mother cell ; J S , young males 

 beginning to form in mother cell ; K ? , female gamete that has formed a 

 cyst-wall for itself, but left a thin spot for the entry of the male ; K S , fully 

 formed males attached to their mother cell ; L, union of S and 9 : one 

 male only unites with the female, the others are excluded ; M, further stage 

 in fertilization ; N, fertilized oocyst (cyst) with its contents filling it ; O, 

 oocyst (cyst) with contents forming a central mass : many such cysts are seen 

 in the droppings of infected grouse : P, oocyst (cyst) showing first stage in 

 division into four ; Q, oocyst with four daughter spores forming ; R, obcyst 

 with four fully formed sporocysts (spores) ; S, cyst with four sporocysts 

 (spores), in each of which two sporozoites are formed ; T, free sporocyst in 

 which the sporozoites have taken up the most suitable position for emergence. 



c 2 



