HAEMOSPORIDIA 609 



12-24 or more merozoites; multinucleate schizonts about 8-9m in 

 diameter; haemozoin granules in loose masses; merozoites about 1.5m 

 long. Gametocytes: Time required for development of ringform into a 

 mature gametocyte is estimated to be about four days; smoothly 

 rounded body, occupying almost whole of the enlarged erythrocytes; 

 brown haemozoin granules numerous. Macrogametocytes are about 

 9-10/j. in diameter, stain more deeply and contain a small compact 

 nucleus; microgametocytes are a little smaller (7-8/x in diameter), 

 stain less deeply and contain a less deeply staining large nucleus. 

 This species is said to invade reticulocytes rather than erythrocytes 

 (Kitchen, 1938). Boyd (1953a) distinguished five series of erythro- 



> 



e f g h j 



Fig. 260. Plasmodium falciparum, X1535 (Original), a, three ring-forms 

 in an erythrocyte; b, a somewhat grown schizont in an erythrocyte with 

 Maurer's dots; c-f, growing and schizogonic stages, g, h; merozoite for- 

 mation; i, macrogametocyte; j, microgametocyte. 



cytic organisms on the basis of nuclear and cytoplasmic character- 

 istics. The organisms of series A give rise by schizogony to organisms 

 of series B or D which in turn produce series C (microgametocytes) 

 or series E (macrogametocytes). Onset of infection is said to occur 

 usually when the parasite density is less than 100 per mm 3 (Boyd, 

 1944). Incubation period (Boyd and Stratman-Thomas, 1933c, 

 1934) ; concentration of organisms (Ferrebee and Geiman, 1946) ; im- 

 munity (Boyd and Stratman-Thomas, 1933a, b; Boyd and Kitchen, 

 1936a; Boyd, 1947); susceptibility (Boyd and Stratman-Thomas, 

 1933c, 1934). 



The benign malaria fever parasite is the commonest and the most 

 widely distributed species in the tropical and subtropical regions as 

 well as in the temperate zone. It has been reported as far north as the 

 Great Lakes region in North Ameria; England, southern Sweden and 

 northern Russia in Europe; and as far south as Argentina, Australia, 

 and Natal in the southern hemisphere. Generally speaking this spe- 



