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Rh Hæmogregarines are found in all classes of vertebrates, and are especially common in reptiles, amphibia, and fishes, but are also found in certain mammals, such as dogs, cats, rats, and the jerboa. They are sausage-shaped bodies with a large central nucleus, and lie encapsuled in the red blood-cells or even in the leucocytes (H. canis and H. muris). They are not

amœboid and no melanin is produced. The sporont, which is the form seen in the peripheral blood, is liberated from the corpuscle as a free vermicule, much resembling a small gregarine in appearance and in its gliding movements. Schizogony does not proceed in the blood, but, as in the case of the subtertian malaria parasite, in some internal organ—in



the bone marrow in some animals; but in the case of H. jaculi of the jerboa, and H. muris of the rat, in the liver cells (Fig. 245.) A number of merozoites are produced; this number varies. Two distinct types of merozoites are formed within different cells. In one type they are numerous and slender, and are then termed micromerozoites; in the other they are few in number and stout, and are then called macromerozoites. The former, re-entering red cells, are destined to