Abstract
Apparently healthy 45 newborn Cynomolgus monkeys (Maraca f ascicularis) were examined for the persistence and disappearance of the hyaloid artery by using an opthalmoscope. On the day of birth, the hyaloid artery was observed in all the newborn animals. Between 21 and 45 days of age, the hyaloid artery faded without exception. The persistence of the hyaloid artery in the newborns and its disappearance during an early period of life can be regarded as a normal phenomenon in the developmental process of infant cynomolgus monkeys.