Adult specimens of Xenopus laevis (Daudin) were operated by unilateral ablation of the tectum opticum and their midbrain was examined 1 to 7 months afterwards. The following conclusions were drawn from the results: 1) The regeneration takes place from undifferentiated cells located in the ependymal layer of the controlateral tectum opticum rather than from the ependyma of the homolateral torus semicircularis. 2) The new formed elements line to the regenerated meninx and, by multiplication and migration, they close the mesencephalic ventricle. When this contact with the meninx is not established, the ependymal layer folds itself and forms soprannumerary ventricles. 3) Afterwards, newly formed fibres reach the restituted area. At the same time the regenerated elements start to differentiate and migrate towards the periphery. Thus, 7 months after the operation the regenerated structure is constituted of white matter, differentiated neurons and ependyma. Nevertheless, the restitutive process is not yet at an end, as is demonstrated by the mitoses still present in the tissue.
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Con il contributo del Ministero per i Beni e le Attività Culturali