304 Sporozoa 



tinue the exoerythrocytic cycle after invasion of blood cells occurs. Exo- 

 erythrocytic schizonts, in such species as Plasmodium gnlUnaceum (56), 

 may be of two kinds, macroschizonts and microschizonts. The latter pro- 

 duce many micromerozoites (100-1000 or so) which enter erythrocytes. 

 The macroschizonts produce a smaller number (64 or less, in P. relictum) 

 of macromerozoites which enter cells other than erythrocytes. In experi- 



Fig. 6. 21. Malarial parasites in birds: A, B. Exoerythrocytic stages of 

 Plasmodium relictinn and P. gallhiaceum in phagocytes (after Coulston and 

 Huff). C-G. Erythrocytic stages of Plasmodium elongatum, Feulgen prep- 

 arations (after Chen): trophozoite (C), schizont with 14 nuclei and a small 

 pigment granule (D), and merozoites (E), x4050; microgametocvte with 

 elongated nucleus and pigment (F), macrogametocyte (G), x3375. 



mental avian infections, exoerythrocytic stages often appear after inocu- 

 lation of erythrocytic forms. 



Exoerythrocytic stages of Plasmodiida develop mainly in lymphoid- 

 macrophage cells (cells of the "reticulo-endothelial system"), although 

 their localization varies from species to species. In Haemoproteus, the 

 parasites occur mostly in endothelial cells of visceral capillaries, especially 

 in the kidney, liver, lungs, and sjjleen. Plasrnodiutn elongatum. has been 



