330 THE GROUSE IN HEALTH AND IN DISEASE 



the disease known as "blackhead" in turkeys, 1 is now generally considered to be 

 a stage in the life-history of a Coccidium. 



(d) Sporozoa Gregarinda. 



MONOCYSTIS sp. 



Spores of a gregarine, almost certainly a species of Monocystis, were occasion- 

 ally found in the contents of the gut of a few Grouse from the Lowlands of Scot- 

 land and the North of England. The spores present much the same features as 

 those commonly occurring in the earthworm, and show the same pseudo-navicellar 

 appearance. The spores seem to pass through the alimentary canal of the Grouse 

 intact. The Grouse acquire the spores accidentally by way of their food (though 

 earthworms are not common on many Grouse moors), and the spores have no ill 

 effect on the birds. Probably the internal heat of the bird's body aids in the 

 development of the sporozoites within the sporocysts, though the spores are not 

 acted on externally by the digestive juices of the host. 



Uninjured spores of gregarines have been observed by L. Pfeiffer in the 

 alimentary tract and fseces of various birds. 



APPENDIX. 



NOTE ON THE GROUSE-FLY, ORNITHOMYIA LAGOPODIS. 



The relation of the Grouse-fly, Ornithomyia lagopodis, to the Grouse has been 

 to some extent a matter of conjecture. Though the Grouse-flies are often found 

 clinging to or concealed among the feathers of the birds, the biology of the fly was 

 uncertain, and it was not known definitely whether the flies obtained blood from 

 the Grouse or not. Having dissected several hundreds of Grouse-flies in an 

 endeavour to find developmental stages of some of the Protozoa infecting Grouse, 

 and possibly parasites natural to the fly itself, I append the following notes on 

 the insect that may be of interest. 



Regarding the food of the Grouse-fly, the insect sucks the blood of the Grouse. 

 Blood in all stages of digestion has been obtained from the gut of the fly. 

 Nucleated red cells of Grouse blood, which show no sign of digestion, are found in 

 the red fluid in the crops of recently fed flies taken from Grouse, while on a few 

 occasions leucocytes also have been observed. The stomach, and particularly the 



'Since the above was written, Drs Cole and Hadley have published a memoir on "blackhead" in 

 turkeys in America, showing that the pathogenic agent is a Coccidium (Eimeria avium). See Bulletin 141 of 

 the Rhode Island Agricultural Experiment Station. 



