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I] consequence of its growth, protruding on the surface of the insect's stomach like a wart or wen (Fig. 13). Meanwhile, important changes take place in the interior of the parasite, which has now acquired a spherical contour and has attained the stage of development to which the term oöcyst is applied. Nucleus and protoplasm divide into a number of spherular daughter cells, around which, attached by one end like the spines on a porcupine, a vast number of minute (16 $$\mu$$), slender, spindle-shaped, nucleated bodies are ultimately formed. At a later stage the spherules disappear, leaving the

Fig. 13.—Stomach after infection with proteosoma.

spindles (sporozoites) loose in the capsule, which is now packed to bursting point. In about a week—sooner or later according to atmospheric temperature, which has a great influence on the rate of development of the parasite—the capsule ruptures and collapses, discharging its contents into the body cavity of the mosquito.

In the salivary gland: sporozoite or infective stage.—From the body cavity of the mosquito the spindle-shaped sporozoites pass, probably by way of the blood, to the three-lobed salivary glands lying one on each side of the fore part of the thorax of the insect (Figs. 11, m, and 14, B). These glands communicate with the base of the mosquito's proboscis by means of a long duct, around the radicles of which the clear, plump cells of the gland are arranged. The