ZOOLOGY 



in certain birds it has been found that their presence is the cause of various 

 feverish affections. The various forms of malaria in man have been proved to 

 be due to the presence in the blood-corpuscles of the patient of parasites 

 belonging to this order. The malaria-parasites, the history of which has been 

 carefully worked out, pass through a life-cycle comparable to that of Coccidium 

 described above. In the trophozoite stage (Fig. 66, A^-O) they live as amoeboid 



-^ssmel 



Fio. 66.— Life-History of Malaria Parasites. A-G, parasite of quartan fever, showing 

 development of trophozoite in a blood-corpuscle and the formation of inerozoites ; H, 

 gametocyte of the same ; I-M, parasite of tertian fever to the formation of the merozoites ; 

 N, gametocyte ; 0-T, crescentic gametocytes of Laverania ; PS, formation of micro- 

 gametes or sperms ; V- W, maturation of megagamete or ovum ; X, fertilisation ; Y, zygote. 

 a, zygote enlarging in stomach of mosquito ; b-e, passing into the body-cavity ; /, g, develop- 

 ment of the contents into a mass of sporozoites ; k, sporozoites passing into the salivary 

 glands. (From Calkin's Protozoa, after Ross and Fielding Ould.) 



intracellular parasites in the interior of the coloured corpuscles of their host. 

 Here they multiply by schizogony — the products (merozoites) entering other 

 corpuscles. Some of the merozoites when they become established in the interior 

 of the corpuscles develop into rounded or crescentic bodies which become the 

 gametocytes (H, N, 0, T). In order that the life-cycle may be completed, it is 

 necessary that the parasite at this stage should be taken into the interior of a 



