Abstract
Electron microscopic studies of C57Bl black mice, from 10 days in utero to 3 days post partum, revealed that the formation of premelanosomes and melanosomes occurred both in neural crest cells and in electron lucent cytoplasmic processes found in the peripheral portion of the neural tube of an embryo 11 days in utero. From these results, it was postulated that some neural crest cells and presumed neuroblasts possessing those processes manifest the ability of melanosome formation at about 11 days in utero, and then might become melanoblasts or dermal melanocytes moving into the surrounding mesenchymes.
The process of the melanosome formation seemed to be divided into three stages, namely, a thin-fibered stage, thick-fibered stage and a mature stage, these stages being similar to those which MOYER (1963) showed in the retinal pigmented epithelium of mice fetuses. The thin-fibered stage was usually found to be unassociated with the Golgi apparatus.
