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28 penetrate the red corpuscles, and multiply. After eight to ten days their progeny can be seen as malaria parasites of the type corresponding to those of the man on whom the infecting mosquito had originally fed. Schaudinn, by diluting blood with blister serum and introducing into the mixture the salivary glands of a malaria-infected mosquito, was enabled to witness the entrance of the sporozoites into the red corpuscles.

The complete cycles (Fig. 15), therefore, both intra and extracorporeal, of the endocorpuscular blood parasites of man and birds can now be described. Using the most generally adopted zoological terms, and commencing with the youngest phase, these parasites may be described as entering the blood corpuscles as sporozoites. Growing at the expense of the hæmoglobin they become pigment and, on reaching maturity, develop either into (a) schizonts (the segmenting body rosette body), or into (b) gametocytes (crescents, spherical bodies of tertians or quartans). (a) The schizonts, after concentration of hæmozoin, divide into a number of naked segments or merozoites, which, on the breaking down of the enveloping blood corpuscle, escape into the blood plasma and enter fresh blood -corpuscles; thus completing the endogenous cycle and providing for the multiplication of the parasite in the vertebrate host. The process of reproduction in this the asexual cycle is called schizogony.

(b) The gametocytes, or gametes, as they are usually termed, belong to the exogenous or sexual cycle passed in the bodies of particular species of mosquito. They are of two kinds: male (hyaline crescents or spheres) and female (granular crescents or spheres). The male gametocyte emits several microgametes (flagella), one of which, breaking away, enters and impregnates the single macrogamete of which the female gametocyte consists. The product is a zygote, which, acquiring locomoting powers, becomes an oökinete, and transfers itself from the lumen to the wall of the