SPOROZOA 1109 



In practice it is not unusual to find parasites of different ages 

 in the same film, as some individuals seem to develop in advance 

 of others; in this case, however, there will not be much difference 

 in their appearance. When extreme difference of age is noted in 

 films it is probable that there have been several different inoculations, 

 producing double or triple infections with quotidian or irregular 

 fever curves, and such cases are not uncommon. 



As all the forms so far described belong to the schizogenous 

 cycle, they may be called schizonts, or trophozoites of the schizo- 



I 



FIG. 154. PLASMODIUM VIVAX. (Army Med. School Collection, Washington, D.C.) 



geiious cycle. The sporogenous cycle begins in man and is com- 

 pleted in the mosquito. The earliest sexual forms noted were the 

 so-called "spheres," large adult parasites, first seen in wet prepara- 

 tions, which did not segment with the schizonts. They are now 

 called gamctocytes and after the disease has lasted some time are 

 found in films made at all stages of the fever; that is, they are 

 incapable of further development until taken into the stomach of 

 the mosquito. The possibility of parthenogenesis will be referred 

 to later. In appearance they are round or oval, and m this fever 

 may be twice the si/e of the red cell. As a rule a narrow margin 

 of red cell is visible after Romaiiowski stains, although the gamete 



