The fresh volumes of the Nucl. mediales et laterales habenulae of 52 male white mice aged between 17 and 60 days of ontogenesis have been determined. The data of both nuclei have been fitted by a sum of logistic functions. There is an increasing component and a decreasing component. The degree of maturity and its differential quotient have been discussed. The Nucl. medialis habenulae belongs to those structures of the central nervous system developing extremely early, the Nucl. lateralis habenulae belongs to those structures of the central nervous system developing extremely early, the Nucl. lateralis habenulae belongs to those structures developing early. It has been pointed out, that there is a complex heterochrony of regional development in the brain. There have to be more quantitative analyses.