<正> The effects of nitroquine on the sporogony of Plasmodium yoelii werestudied with electron microscope.The drug was given by feeding female mosqui-toes directly in the form of mixture with sucrose solution.Scanning electronmicroscopic studies revealed that the oocysts were smaller and markedly degener-ated.Surface of the oocysts was rough and uneven.Under transmission electronmicroscope

the cytoplasm of the affected oocysts contained vacuoles.Mitochondrial and nuclear membrane was damaged.The number of residualbodies increased.Formation of sporoblast did not occur in most of the affectedoocysts.The nuclear membranes of the degenerated sporozoites became thick-ened and the density of nucleus matrix markedly decreased.The results indicatedthat nuclei and the membrane system were mainly affected.