Abstract
The complete life cycle of "Plasmodium" kochi has been worked out in the monkeys Cercopithecus aethiops and C. mitis. This study shows that the organism is not a Plasmodium but belongs to the genus Hepatocystes of the family Haemoproteidae. A redescr. of the sp. is given. Asexual as well as sexual reproduction on the part of the organism occurs in the monkey and enables the maintenance of a consistent low-grade infection over long periods of time. No vector by which the organism is transferred from monkey to monkey has as yet been identified, but is thought to be some arthro-pod.