Fig. 81.—Stages of development of pernicious or malignant tertian parasites in the intestine of Anopheles macultpennis. (After Grassi.) a, macrogametocyte (crescent) still attached to human blood corpuscles; b, macrogametocyte (sphere) half an hour after ingestion by the mosquito; c, microgametocyte (crescent) attached to the blood corpuscle; d, microgametocyte (sphere) half an hour after ingestion; the nucleus has divided several times; e, microgametes attached to the residual body (polymitus stage).
Fig. 82.—Oökinete of the malignant tertian parasite in the stomach of Anopheles maculipennis, thirty-two hours after ingestion of blood. (After Grassi.)
If the gametocytes, which are globular, or in the pernicious or malignant tertian parasite crescentic (fig. 81), gain access to the intestine of an Anopheline,[199] they mature. The macrogametocytes extrude a part of their nuclear substance (fig. [80], 13a, 14a) and thereby become females or macrogametes. The microgametocytes, on the other hand, undergo repeated nuclear division, preparation for this being made apparently whilst in the blood of man. This results in the formation of threadlike bodies which move like flagella and finally detach themselves from the residual body (fig. 80, 13b, 14b). These are the males or microgametes[200] (fig. 80, 15b).
Fig. 83.—Section of the stomach of an Anopheles, with cysts (oöcysts) of the malignant tertian parasite. (After Grassi).
Copulation takes place in the stomach of the Anopheline (fig. [80], 16). A microgamete penetrates a macrogamete and coalesces with it. The fertilized females elongate very soon and are called oökinetes or “vermicules” (figs. 80, 17; 82). They penetrate the walls of the stomach, pierce the epithelium (fig. 80, 18, 19), and remain lying between it and the superficial stratum (tunica elastico-muscularis). Then they become rounded and gradually develop into cysts which grow larger and are finally visible to the naked eye, being called oöcysts (figs. 80, 20-24; 83). Their size at the beginning is about 5 µ, the maximum that they attain is 60 µ, only exceptionally are they larger.