l')8G 1>I!. II. H. KAXTilAM OX THE [MtlvS, 



has been watchi'tl in life — ;ui(l the micropyle is then closed 

 (ti.ys. 49-51 ; text-fig. (55, M). The fertilised oiieyyt (text-fig. 05, N) 

 then passes into the lumen of the gut and is voided with the fa?ces 

 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. LVII. fig. 52, 

 PI. LYIII. figs. 61, 62, 64) shi-ink away from the poles and 

 become a rounded, central mass (figs. 65, 77, 78 ; text-fig. 65, O). 

 The nucleus rapidly divides into two (PI. LVII. fig. 56), then four 

 (fig. 54 ; text-fig. 65, P) ; each nucleus has protoplasm segregate 

 around it (figs. 55, 67, 70 ; text-fig. 65, Q), a wall is secreted, and 

 the net residt is that four sporocysts (figs. 58, 71-76; text- 

 fig. 65, R) aie produced within the oocyst. Within each 

 s[)orocyst, two spoi'ozoites gradually difterentiate (figs. 58-60, 

 71-76; text-fig. 65,8), and when the sporocyst (text-fig. 65, T) 

 is ingested by a new host, the sporozoites creep out of the 

 spoi'ocyst softened by the pancreatic juice of the new host and 

 proceed to attack the epithelium of the gut, producing thereby 

 the pi'imarv infection of the bird. 



The main difiei'ences between Eimeria avmm (Silvestrini and 

 Rivolta) and E. schaheryi (Schaiulinn) may be briefly sum- 

 marised : — 



1. E. avium is smaller than E. schaherg'i. 



2. The merozoites of E. aviitm are ai'iaiiged ' en barillet,' 



those of E. schubergi ' en rosace.' 

 ^}. Pi-ecocions encystmeut of E. avmm occurs before fertili- 

 sation. This is not the case with E. schubergL 



4. Fertilisation in E. aviitm is micropylar ; in E. schnhergi 



a cone of reception is fornied by the maci'Ogamete. 



5. The macrogamete of E. avium contains much more deeply 



staining i-eserve food-material than that of E. schnhergi, 

 thereby increasing the difliculty of minute examination 

 of the parasite. 



6. The cA'sts of E. avium are oval, those of E. schuhergi are 



round. 



VI. Thk Ekfect of EiMi-miA aviim ox tiik Host. 



The efi'ect of coccidiosis on the gi-ouse may now be considered 

 briefly, fuller details regarding the symptoms of the disea.se and 

 its ettects being given in my paper relating to experimental 

 coccidiosis (P.Z^S. 1910, pp. 708-722). 



External effects. — The chief external e\ iilence of cocci<liosis is 

 the pale colour and great fluidity of the ca-cal (soft) droppings of 

 the grou.se, the pale tint being due to myriads of oocysts and the 

 condition being that of diarrhwa. Sportsmen and keepers have 

 noted diarrluea as a symptom of " grouse disease." A similar 

 di.sea.se in fowls is known among poultry-men as "white 

 <linn-lm\i." As the Cocci iliai\ parasites cause great denudation 



