258 



THE GROUSE IN HEALTH AND IN DISEASE 



each micro-gametocyte gives rise to many minute, motile microgametes, the male 

 elements (Fig. 2). Fertilisation (Fig. 3) occurs through a micropyle left in the wall 

 with which the macrogamete invests itself, and the fertilised oocyst so produced, 

 passes out through the much damaged epithelium into the lumen of the gut and 

 thence to the outside. The epithelium of the duodenum and cseca is sometimes 



Text Fig. 2. 



Figs. A-F. 



Stages in the development of the oocysts of Eimeria avium, as 

 seen in fresh preparations. 



A. Oocyst (encysted zygote) with protojilasm coiupletely filling it. 



B. Older oocyst with zygote contents forming a central sphere. Many such 



cysts are found in infected cteca and infected fieces of Grouse. 



C. Oocyst with four nuclei, about to form sporoblasts. 



D. Oocyst with four round sporoblasts. 



E. Four ovoid sporocysts within oocyst. 



F. Fully mature oocyst with four sporocysts, each containing two sporozoites, 



entirely denuded by the action of the many parasites that infest it, and the sub- 

 mucosa also is sometimes infected by the Eimeria. 



The contents of the oocyst, at first filling the interior (Text-Fig. 2, A), gradually 

 contract (Text-Fig. 2, B), towards the centre, or occasionally towards one pole, and 

 then divide (Text-Fig. 2, C) into four round masses (Text-Fig. 2, D) known as 

 sporoblasts. Each sporoblast becomes an oval sporocyst (Text-Fig. 2, E) while still 

 within the oocyst, and within each ripe sporocyst two sporozoites or germs are 

 developed. Consequently each oocyst gives rise to eight sporozoites (Test- 

 Fig. 2, F). 



