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946 breaks up into a number of small forms or merozoites; finally the leucocyte bursts, setting free the merozoites, which, entering red blood-corpuscles, assume once more the typical shape of the sporonts. The male sporont is easily distinguished from the female by the larger size of its nucleus and by the faintly staining properties of its protoplasm.

3. The genus of Daneliewsky must be carefully distinguished from the leucocytic hæmogregarines to which allusion has already been made. The leucocytozoa are elongated oval bodies (Fig. 251), parasitic in the blood of birds. They modify the shape of the host cell, generally a mononuclear leucocyte. Male and female forms are recognized; in the latter the protoplasm takes on a deep stain; no

Fig. 251.—Leucocytozoon neavei. (After Neave.) From the guinea-fowl.

pigment is formed, Schizogony takes place in the spleen of the bird. Exflagellation and fertilization of the gametocytes occur exactly as in the malaria parasite, but their method of transmission and the definitive host are still unknown.

4. The genus consists of a number of minute oval or rod-like organisms, several of which are often contained in the one red blood-corpuscle. No pigment is produced, but the corpuscle is destroyed, the hæmoglobin set free and ultimately excreted by the kidneys of the host.

The best-known piroplasm is Babesia bovis (or bigemina), the parasite of red-water fever of cattle.

Piroplasma caballi causes biliary fever in horses; Pircplasma (Babesia) bovis, red-water or Texas fever in cattle; Piroplasma canis (Fig. 252), malignant jaundice in dogs; while Piroplasma mutans is apparently a harmless parasite in the blood of African cattle.

The typical piroplasma is a pear-shaped body dividing by a process of budding, and is found in the red corpuscles of oxen, of sheep, and of a number of wild animals.

The genus Piroplasma has, for convenience' sake, been divided into a number of subgenera of doubtful validity.