(572 DR. U. B. FAXTUAM OX THE [^laj 3, 



1. The ]\Ior])liolooy and Li t'c-Hi story of FAnier'm (Coccidiuni) 

 avium : a Sporozoon causing a fatal flisoase among 

 Tonng Grouse. By H. B. Fantham, D.Sc.Lond., 

 B.A.Oantab., AJi.oiS., F.Z.S., Christ's College, (^ani- 

 hridge, Assistant to the Quick Professor of Biology, 

 Cambridge, and Protozoologist to the Grouse Disease 

 Inquiiy. 



[Received April 5, 1910.] 

 (Plates LV.-LYIIL* and Text-figure 65.) 



Contents. 



Page 



I. Introduction 672 



II. The Generic Names J?/»ie>'/a and Cofr/fZ(H»i 673 



III. Methods 674 



IV. Morphology 674 



(a) The j'oung, growing- Parasite 675 



(b) Schizogony 676 



(c) Gametogony 678 



JNIacrogametocyte and macrogaiuete 678 



Microgametooyte and microgauietes 680 



(d) Fertilisation 680 



(e) Sporogony 681 



V. Summary of the Life History 683 



VI. The effect of ^. a y»<m on the Host 686 



VII. Concluding Remarks 688 



References to Literature 688 



Explanation of Phites 690 



t I. IXTKODUCTIOX. 



The subject of this memoir is a microscopic, protozoal parasite, 

 which infests the lining epithelium of the alimentary canal of 

 grouse. It belongs to the Coccidia, a group of parasitic Protozoa 

 many of which are known to occur in the digestive tracts of 

 both Vertebrates and Invertebrates. These mintite organisms 

 i-eprodnce by means of I'esistant spore.s\ and lielong to that class 

 of the Protozoa known as the Sporozoa. The Coccidia are of 

 economic impoi-tance, inasmuch as they destroy the mucous 

 membrane of the intestine of the host, thereby setting up 

 enteritis which is accompanied by diarrhcea, and very often 

 has a fatal effect upon the unfortunate animal harbouring the 

 parn.sites, e.specially if the host be young. 



8uch a disease — tenned coccidiosis — has long been known in 

 rabbits, and is often fatal. Occasionally coccidiosis occurs in 

 man. The life-history of a Coccidian parasite is complicated. 

 There are two pha.ses in the life-cycle: — (i) a multiidicative phase 

 within tlie cells of the gut-epithelium of the host, and (ii) a re- 

 productive pha.se leading, after a sexual act, to the formation of 



* For explanation of tlie Plates see p. 690. 



