"GROUSE DISEASE "—COCCmiOSIS 259 



A certain amount of variation, as exhibited by the oocysts of ^. avium, has 

 been noticed by Morse (1908) in the coccidian parasite of " white diarrhoea" of 

 fowls, where the oocysts are round to oval, and from 12m to 25^1 in diameter. The 

 oocysts of E. avium in Grouse, which is identical with the parasite found in " white 

 diarrhoea " of fowls, also vary among themselves. Usually the oocysts are oval 

 (PI. xxxviir., Figs. 4-8), but a series of varying sizes and shapes can readily be found 

 (Figs. 8, 11, 12, 14), while round oocysts also occur (Fig. 11). The exact shape 

 and size of the oocyst is determined by the space in the cell available for the 

 development of the macrogamete, and should not be insisted upon as a specific 

 character, for where many parasites are aggregated together in a limited area of 

 epithelium, the macrogametes and oocysts are small, while in areas of the gut 

 but poorly parasitised, large oocysts preponderate. Nutrition of the parasite has 

 obviously a great influence on both its size and its propagative power. 



In some cases the gut- wall is extremely thin and tender ; in other birds this^ 

 effect is not marked. Inflammatory patches may be seen at intervals, particularly 

 in the caeca, and the cagca usually are enlarged. At the ileo-csecal junction, where 

 a recurrence of schizogony and sporogony occurs, much degenerated epithelium is 

 present in the gut contents, and this epithelium contains both schizonts and 

 gametocytes. 



The large intestine of chicks infected with Coccidiosis sometimes shows 

 inflammatory patches, and blood may be present in the rectal contents. The 

 rectum itself seems rarely to be attacked by E. avium, though its contents usually 

 contain oocysts. 



The kidneys, spleen, liver, and gall-bladder of birds suflering from Coccidiosis 

 never contained Eimeria, though the spleen and gall-bladder were sometimes 

 enlarged. Examination of the generative organs has shown no stage of E. avium 

 so far, though it is possible that eggs may become contaminated during their 

 passage through the cloaca of the mother. The young chicks then might be 

 hatched in contact with infectious material, and so acquire Coccidiosis early in life. 

 Eight days old Grouse chicks were the youngest naturally infected chicks that I 

 examined. The period of eight to ten days is the one determined roughly by my 

 experiments as being required for the complete developmental cycle of E. avium 

 in fowls and pigeons, from the time of ingestion of the oocysts to the excretion 

 of the maximum number of oocysts of the second generation. 



Many bacteria are present naturally in the gut of the Grouse, and their active 

 movements can be well seen, especially in the ceecal contents of freshly killed 



