94 MANUAL OF HUMAN PROTOZOA 



liberated into the blood plasma and enter erythrocytes, the 

 ring forms reappear in the peripheral blood. 



Gametocytes 



The gametocytes develop from the ring form in the 

 internal organs, especially the spleen and bone marrow. 

 Mature gametocytes which appear in the peripheral blood 

 and therefore are present in ordinary blood smears, are 

 characteristically crescentic or sausage form ("crescents") 

 and have an important diagnostic value. They are about 

 10-12m by 2-3n. The macro- and micro-gametocytes may be 

 distinguished as follows: 



4. Plasmodium ovale Stevens 1922 



This is considered as the cause of mild tertian or Ovale 

 tertian fever which appears to be confined to Africa and 

 Asia (Philippine Islands and India). The validity of the 

 species is still disputed among malariologists. Its schizog- 

 ony is completed in about 48 hours and its morphological 

 characters resemble both P. vivax and P. malariae. The 

 whole schizogony and gametocyte formation occur in the 

 peripheral blood. 



Schizonts 



1. Ring forms. They are similar to those of P. vivax and 

 P. malariae. Schiiffner's dots appear early (Fig. 25, l). 



