[Influence of brain grafts on growth restoration of snail (Helix aspersa) deprived of the midbrain].

Microsurgical removal of the mesocerebrum from the brain of juvenile snails stopped their growth whereas intracerebral implantation of desheathed cerebral ganglia (CG) re-established it. When the animals were grafted with CG from very young snails growth was much more stimulated than with CG from donors of the same age or from adults. Furthermore, young CG of juvenile fast growing specimens of the large species (Helix aspersa maxima) induced a higher growth rate than the CG of the ordinary small garden snails (Helix aspersa aspersa). Labelling of the neural grafts with the vital fluorescent dye fast blue enabled us to follow the repopulation of the lesioned area of the brain of the host during the functional integration of the implanted neurons into the circuits that control growth in snails.