424 ZOOLOGY. 



When full-grown the trophozoite is spherical and almost 

 as large as the corpuscle, and it proceeds to divide by 

 schizogony. The nucleus divides, the daughter nuclei 

 travel to the surface, and the protoplasm divides into a 

 corresponding number of rnerozoites surrounding a small 

 mass of residuary protoplasm which contains all the pigment 

 granules (fig. 207, 9). During the schizogony the corpuscle 

 disintegrates, and it is this destruction of the corpuscles 

 which is so harmful to the host. The merozoites are set 

 free in the blood, and the residuary protoplasm is disinte- 

 grated, its pigment being scattered and afterwards deposited 

 in the spleen, liver, lungs, kidneys, and brain. 



3. Conjugation. By repeated schizogony the number 

 of parasites increases by geometrical progression like the 

 Coccidia in an infected epithelium until a very large 

 number of the corpuscles are destroyed : the only check is 

 the action of the leucocytes, which destroy the merozoites. 



When the host is becoming exhausted certain tropho- 

 zoites develop into gametocytes as in Coccidium. In Lave- 

 rania malariae the gametocytes are like curved sausages, 

 exceeding in length the diameter of the corpuscle the 

 remains of which are seen in the hollow of the gametocyte 

 (VIII. a, VIII. b). These are known as crescents and are 

 very characteristic of pernicious malaria. In the male 

 crescent the pigment granules are scattered, in the female 

 they are aggregated round the nucleus. The crescents 

 appear to originate in the spleen and bone-marrow, but 

 when fully developed they are found in the superficial 

 blood-vessels. They afterwards become oval, then spherical, 

 and free themselves from, the remains of the blood cor- 

 puscle. They do not get beyond the spherical stage in the 

 human blood, and may be transferred to the stomach of 

 the mosquito as crescents, or ovals, or spheres. 



The development of the gametocytes and the process of 

 conjugation take place in the stomach of the mosquito. 

 In the male gametocyte (fig. 2 11, IX. a.) the nucleus breaks 

 up and the daughter nuclei pass to the surface of the 

 gametocyte. Then, as in Coccidium, each of the several 

 nuclei becomes elongated and with a small quantity of 



