Attività proliferativa nel romboencefalo di Anfib[icaron] anuri ed urodeli durante il periodo larvale

Abstract

The mitotic activity in the germinal laycr of the hindbrain was studied in larvae of anouran and urodelan Amphibians. The mitotic activity does not cease till a month after metamorphosis; therefore the number of the nerve cells in the Amphihian hindhrain is determined late. The proliferation of the dorsal half (alar lamina) is consistently higer than that of the ventral half (basal lamina); this differential mitotic activity can be explained supposing that the morphogenesis and the growth of the neural tube are supported chiefly by the activity of the alar lamina. The differences in the mitotic activity of the germinal layer between anouran and urodelan Amphibians arc due to the regulative processes of the development of the examined species. The mitotic patterns of the alar lamina show in most respects contrasting features, which have been correlated with the different ecology of those Amphibians; i.e. the peak observed in the Anouran is related to the development of the nervous centers functionally connected with terrestrial life (cerebellum), on the contrary in the Urodelan it is related chiefly to the growth of the central nervous system.