The developments of Plasmodium yoelii yoelii in nude and normal mice are different.In nude mice theascending slope of infection rate of RBC is slow,the date of death is obviously postponed,the schizont rateis low,the number of nuclei per schizont is less,the percentages of multiple—infected red blood cell and ga-metocytes is higher than that in the normal animals.These development characteristics are dependent on theimmunlolgieal stage of the host.