Persistence of the nervus terminalis in adult bats: a morphological and phylogenetical approach.

The presence of the terminalis system in adult bats is demonstrated by light microscopical investigation of several species of Microchiroptera. In late embryonic and fetal stages of the mouse-eared bat (Myotis myotis) the compact central terminalis ganglion gradually differentiates into a three-dimensional network of cord-like ganglia and fiber bundles. Rostrally the terminalis system is in immediate contact with the medial-most fila olfactoria; caudally terminalis rootlets attach near the border between the olfactory bulb and the septum of the brain. With respect to the findings presented here it seems likely that all mammals develop a terminalis system in early ontogenesis and retain it until the adult stage. However, considerable differences concerning the number of persisting neurons may be found among some mammalian orders.