88 



ZOOLOGY 



SECT. 



converted into either micro- or mega-gametocytes. Each of the former (h, j) 

 gives rise by division to a number of narrow biflagellate microgametes or 

 sperms. Each of the megagametocytes (e, /), after a process of the nature of 

 maturation, forms a single rounded megagamete (ovum). When this becomes 

 fertilised by the penetration into it of a single microgamete, the resulting body 

 (zygote or oosperm) divides to form a varying number of cells each enclosed in 



B 



FIG. 67. Life-history of Malaria Parasites. A-G, parasite of quartan fever, showing 

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

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

 N, gametocyte ; O-T, crescentic gametocytes of Laverania ; P-S, formation of micro- 

 gametes or sperms; (J-W, maturation of megagamete or ovum; X, fertilisation; F, 

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

 /, g, development of the contents into a mass of sporozoitcs ; h, sporozoites passing into 

 the salivary glands. (From Calkin's Protozoa, after Ross and Fielding Quid.) 



a resistant cyst (k). These give rise to spores with a firm, chitinous spore- 

 membrane, each containing two or more falciform young or sporozoites (I). 

 The cyst destroys the cell as it grows, and thus becomes free in the cavity by 

 which the epithelium is lined. The spores may thus pass out to the exterior, 

 and, if taken into the digestive canal of a new host, may liberate the now 

 active sporozoites, which may penetrate into epithelial cells (a) to become the 

 trophozoites with which the cycle began. 



