[Cytoarchitecture of the principle diencephalic visual centers in the embryo and the chicken Gallus domesticus L. Experimental study].

The effects of the bilateral removal of the optic vesicle on the cytoarchitectonics of the main diencephalic visual centres of Gallus domesticus L. embryos and chicken have been studied from the 10th, day of incubation until the 15th, day after hatching. - Without afferent optic pathways there is no significnat change in cellular components of nucleus lateralis anterior, nucleus geniculatus lateralis ventralis, nucleus griseus tectalis, nucleus rotundus and nucleus pretectalis principalis. When these centres have specific organization, one may observe a spatial distribution of neurons different from that of unoperated chickens. - Whereas the nucleus ectomamillaris disappears early, the nucleus superficialis synencephali is not differentiated. the nucleus geniculatus lateralis dorsalis, reduced in size, shows an alternation of cell constitution even if cytoarchitectonics appears to be similar to that of unoperated chickens. A comparison of these results with those on tectum opticum by authors brings up the question of the exact nature of retino-thalamic connections and of their morphogenetic role. If morphogenetic influence appears to be certain on some structures it seems to be limited on others.