"GROUSE DISEASE "-COCCIDIOSIS 249 



(PI. xxxvi., Figs. 47, 48 ; Text-Fig. 1, K ?). This oocyst-wall is formed while the 

 parasite is within the epithelium. 



Fertilisation (Figs. 47, 48; Text-Fig. 1, L) occurs the process has been watched 

 in life and the micropyle is then closed (Figs. 49-51 ; Text-Fig. 1, M). The 

 fertilised oocyst (Text-Fig. 1, N) then passes into the lumen of the gut and is voided 

 with the faeces of the Grouse. The further development of the oocyst largely 

 depends on climatic conditions. Under the influence of warmth and moisture, the 

 contents of the oval oocyst (PI. xxxvi., Fig. 52; PI. xxxvu., Figs. 61, 62, 64) shrink 

 away from the poles and become a rounded, central mass (Figs. 65, 77, 78 ; Text- 

 Fig. 1, 0). The nucleus rapidly divides into two (PL xxxvi., Fig. 56) then four 

 (Fig. 54 ; Text-Fig. 1, P) ; each nucleus has protoplasm segregated around it 

 (PL xxxvi., Fig. 55 ; PL xxxvu., Figs. 67, 70 ; Text-Fig. 1, Q), a wall is secreted, and 

 the net result is that four sporocysts (Figs. 58, 71-76 ; Text-Fig. 1, R) are produced 

 within the oocyst. Within each sporocyst two sporozoites gradually differentiate 

 (Figs. 58-60, 71-76 ; Text-Fig. 1, S), and when the sporocyst (Text-Fig. 1, T) is 

 ingested by a new host, the sporozoites creep out of the sporocyst softened by the 

 pancreatic juice of the new host and proceed to attack the epithelium of the gut, 

 producing thereby the primary infection of the bird. 



The main differences between Eimeria avium (Silvestrini and Rivolta) and E. 

 schubergi (Schaudinn) may be briefly summarised : 



(1.) E. avium is smaller than E. schubergi. 



(2.) The merozoites of E. avium are arranged "en barillet," those of E. 



schubergi "en rosace." 

 (3.) Precocious encystment of E. avium occurs before fertilisation. This is 



not the case with E. schubergi. 

 (4.) Fertilisation in E. avium is micropylar; in E. schubergi a cone of 



reception is formed by the macrogamete. 

 (5.) The macrogamete of E. avium contains much more deeply staining 



reserve food-material than that of E. schubergi, thereby increasing the 



difficulty of minute examination of the parasite. 

 (G.) The cysts of E. avium are oval, those of E. schiibergi are round. 



V. THE EFFECT OF EIMERIA AVIUM ON THE HOST. 



The effect of Coccidiosis on the Grouse may now be considered briefly, fuller 

 details regarding the symptoms of the disease and its effects being given in the 

 article relating to experimental Coccidiosis. 1 



1 Vide Part II. p. 252. 



