An ontogenetic study of the central nervous system is an important tool for the under- standing of its morphological and morpho-functional relations. Numerous qualitative results on the ontogenesis of the visual system can be found in the literature, but there are only very few quantitative results fulfilling the following parameters: (1) samples of sufficient size; (2) measurements considering results of stereology; (3) evaluation and interpretation performed with sound biomathematical methods; (4) quantitative of the shrinkage caused by the histological technic. The first three results independent demands can be fulfilled by using available computerized stereological and biomathe- matical methods (Kretschmann and Wingert, 1968, 1969a, b, c, 1971; Wingert, 1969; Zilies and Wingert, 1972; Zilies et al., 1976a, c, d). The interdisciplinary cooperation between morphologists and mathematicians makes possible the analysis of the volume growth, the number of nerve-and glial cells in a whole brain region (Schleicher et al., 1975a, b; Zilies and Wingert, 1973a, b; Zilies et al., 1974, 1975a, b), the semi-automatic analysis of the nucleolar diameters in nerve cells (Zilies et al., 1976b) and computer aided compartment analysis with the point- counting method (Zilies et al., in press b). Tupaia belangeri, an interesting animal for neurobiologists, was the experimental animal of choice because it combines the advan- tages of a small brain (conducive to rapid processing) with many characteristics of the of the primate brain.