[Ecological niches and morphometric development of visual centers in primates]

Volumes of the lateral geniculate body and the tractus opticus from 12 species of Prosimians and 10 species of Simians were examined. The progression indices of the lateral geniculate Body do not differ significantly neither between Prosimians and Simians nor between diurnal and nocturnal Primates. Therefore, they cannot be considered as a criterion for phylogenetic development or for eco-ethological adaptations such as activity cycles. The progression indices of the tractus opticus, however, are higher in diurnal than in nocturnal Primates. The two-groups discriminant function based on the progression indices of the lateral geniculate body and the optic tract serves to establish a line which separates nocturnal from diurnal Primates. The lack of any correspondance in the progression of these two brain structures may be explained by the differential development of magnocellular and parvocellular layers of the lateral geniculate body.