382 H^MOPROTEUS COLUMB^ [CH. 



into merozoites. Each nucleus, together with a small mass of 

 cytoplasm, becomes separated off, and thus, in the inside of the 

 cyst, hundreds of merozoites are formed (Fig. 87, ig) . The cysts, 

 together with the leucocyte that contains them, then rupture, 

 and the merozoites are set free in the blood stream of the pigeon 

 about 26 days after the bite of an infected insect (Fig. 87, 20). 



The merozoites then invade the red blood corpuscles and 

 develop into the typical halteridium forms that are found in the 

 circulating blood (Fig. 87, i-j), and these are incapable of any 

 further development within the body of the pigeon. Accord- 

 ingly there is no cycle of schizogony such as occurs in the case 

 of the malarial parasites, but after the completion of develop- 

 ment within the leucocytes in the internal organs, the merozoites, 

 as soon as they have entered the red blood corpuscles, develop 

 into the sexual forms, male and female. 



The appearance of the male and female gametocytes of 

 HcBnioproteus is practically the same as that of the corres- 

 ponding stages of Plasmodium. The macro-gametocytes stain 

 intensely and contain a large amount of reserve food material 

 in the form of granules, whilst the micro-gametocytes are 

 much lighter and almost free from granules. 



When taken into the stomach of the invertebrate host the 

 gametocytes escape from the red cells and give rise to the 

 gametes. The macro-gamete is a large rounded body containing 

 a single nucleus near the middle of the cytoplasm (Fig. 87, ja). 

 The nucleus of the micro-gametocyte (Fig. 87, ^.h) breaks up into 

 a number of small particles arranged in pairs, and each pair, 

 together with a small quantity of cytoplasm, becomes separated 

 off in the form of an elongate vermiform micro-gamete. 

 These swim about until they come in contact with a ripe 

 macro-gamete when fertilization takes place, the result of the 

 fusion being an ookinete. The liberation of the micro-gametes 

 and the process of fertilization may be observed by placing a 

 small quantity of infected blood on a glass sHde and watching 

 it under the microscope. Probably as a result of the diminu- 

 tion in temperature, the ripening of the gametes and fertih- 

 zation take place in the same way as if the blood had been 

 ingested into the stomach of its invertebrate host. 



