In a previous paper by one of us (Filoni and Oberti, 1968), the poor regenerative capacity of the optic tectum in adult specimens of Xenopus laevis was reported. The right optic lobe had been removed by suction; since this technique causes connectival proliferation at the healing site, it was decided to repeat the experiment by operating the animals in two different ways to ascertain the effective regenerative power of the midbrain. The right optic lobe of adult Xenopus laevis was removed either with surgical instrument, or by cauterization, and the animals were sacrificed 150-210 days after the operation. The results were the following:
1) The cauterization produces a great amount of connective tissue, which certainly interferes with the regenerative process;
2) After surgical ablation, the connectival proliferation is irrelevant; in spite of this, the regeneration which follows presents the same characters as that which follows cauterization. Both result in the formation of a reduced optic lobe.
Thus, the previously obtained results are fully confirmed: the regenerative capacity of the midbrain of adult Xenopus laevis is low and it never ends in a complete restitution of the ablated side. Only a small number of nerve cells and fibers are newly-formed.