lo Gtiide to Insects and Ticks 



8. — The mei'ozoites become free in the blood-plasma by the 

 disintegration of the red corpuscle (lig. 1, e). Each merozoite 

 invades a red blood-corpuscle, and develops into amoebula, rosette, 

 and further merozoites, as explained in the preceding models. 



9, 10. — After several cycles of amoebula, rosette, and 

 merozoites, a merozoite on entering a red corpuscle grows into a 

 sexual form which may be crescentic (fig. 1,/). 



11. — The crescent increases at the expense of the corpuscle, 

 and male crescents become distinguishable from female crescents, 

 as explained in models 12 and 15. The crescents undergo no 

 further change in human blood, but when blood containing 

 crescents is sucked by a female anopheline mosquito, the crescents 

 undergo development. 



12. — The male crescent (fig. 1, _r/) is shorter and more rounded 

 than the female crescent. It has clearer protoplasm and a larger 

 nucleus, and the pigment granules are more scattered. 



13, 14. — The male crescent becomes spherical and the nucleus 

 multiphes. 



15. — The female crescent (fig. 1, It) has denser protoplasm and 

 a smaller nucleus than the male, and the pigment granules are in 

 the middle part of the crescent. 



16, 17, 18.— The female crescent becomes spherical, and, after 

 extruding two small cells (? polar bodies) in succession, becomes 

 the macrogamete or ovum, and is ready for fertilisation. 



19. — The male sphere shoots out four, five or six slender pro- 

 cesses (microgametes or sperms) consisting mainly of nuclear 

 material (fig. 1, i). The remainder of the sphere plays no further 

 part in the life-history. 



20. — A microgamete is attracted by, and enters into an ovum 

 (fig- 1. ])■ 



Fig. 1. — Life Histoey of the Organism op Pernicious Malaria. 



«, malarial germ or sporozoite, as introduced into the blood of man by a female 

 anopheline mosquito at the time when it is sucking blood ; 6, sporozoite after entry into a 

 blood-corpuscle of man ; c, growth of the sporozoite into an amoebula ; (7, division of the 

 amoebula to form merozoites ; e, liberated merozoites ; /, growth of a merozoite into a 

 crescent; f/, free male crescent; h, free female crescent; i, male cell with projections, 

 which lengthen and are set free as sperms ; j, fertilisation of an ovum by a sperm ; fc, ferti- 

 lised egg as an active motile vermicule ; I, sphere formed from the enlarged vermicule, after 

 this has bored through the stomach-wall of the mosquito ; m, portion of the sphere or cyst 

 at a late stage of development, containing countless needle-shaped spores, which, when the 

 cyst bursts, escape as sporozoites into the organs of the mosquito's body, and pass through 

 the salivary glands into the proboscis, and so infect a man bitten (i.e. pricked) by the 

 mosquito, a-l are enlarged 3, .500 diameters ; m is drawn to a smaller scale of magnification. 



