1910.] MORPHOLOGY OF EIMERIA AVIUM. 673 



resistant spores adapted for life outside the l)ody of tlie host. 

 The spores so formed are the means of spreading the parasite 

 and lead to the infection of fresh hosts. The two phases were 

 formerly considered to belong to separate parasites ; but the 

 occui-rence of alternation of generations in the life-cycle of 

 Coccidia was first suggested by R. Pfeifier in 1892, conjugation 

 was discovered in Coccidia by Schaudinn and Siedlecki (1897), 

 and the complete life-cycle was demonstrated with a wealth of 

 morphological and cytological detail in the celebrated memoir of 

 the late Dr. Schaudinn (1900) on Eimeria {Coccidium) schubergi, 

 parasitic in the gut of the centipede Lithohius forficatus. 



Coccidia have been recorded from most of the great groups of 

 the Metazoa, but very few Coccidian life-histories have been 

 investigated completely. 



Dr. Leiper, while working on helminthiasis in gi'ouse in May 

 1 909, noticed the occurrence of Coccidian cysts in large numbers 

 in the gut of many grouse-chicks, with concomitant enteritis, 

 very often pi-oving fatal. The Coccidian cysts are oval and, at 

 first sight, might easily be mistaken for eggs of worms. Leiper 

 suggested that coccidiosis was a factor in " grouse disease," 

 especially in young bii'ds. Through the courtesy of Lord Lovat 

 I was enabled to spend a few days early in June 1909 on a Scotch 

 moor to investigate coccidiosis in grouse chicks *. Previously we 

 had noticed, at various times, the occurrence of Coccidian cysts 

 in adult grouse, but not in large numbers. 



I have much pleasure in expressing my thanks to Lord Lovat, 

 Dr. A. E. Shipley, Dr. E. A. Wilson, Dr. Hammond Smith, and 

 Dr. Leiper for aiding my researches by procuring material for me, 

 and to Professor Nuttall, in whose laboratory much of my Work 

 was done. I would also thank Mr. A. S. Leslie for placing me in 

 communication with correspondents, and to members of the Grouse 

 Disease Inquiry and many correspondents I am also indebted. 



In this paper I wish to recoixl my researches on the morphology 

 and life-history of Eimeria avium, more especially as it occurs in 

 the grouse. I would point out that the length of time at my 

 disposal for these researches has been limited, only one season 

 being available to me for procuring material, and I have had 

 several other investigations to consider during the period, so that 

 I was not able to give undivided attention to the elucidation of 

 the Protozoa of grouse. However, the complete life-cycle of 

 Eimeria avium., responsible for the dwindling of grouse broods in 

 spring, is here set forth for the first time, so far as I am aware. 



II. The Generic Names Eijieiua axd Coccidium. 



Unfortunately, owing to the rule of priority, the generic name 

 Coccidiam (Leuckart 1879) no longer holds, but is replaced by 

 that of Eimeria (A. Schneider 1875). I am in sympathy witli 



* The numlicr of jrvnusL' chicks ilviiii;- of cdccidiosis on tlie moors is iiol rM>ily 

 stimiitod, for the chicks die in the heather, and their tiny corpse^ arc nircly found. 



