Development of the Epithalamus in Alligator mississippiensis.

The epithalamus is present in all vertebrates where it is a central part of the dorsal diencephalic conduction system whose functions are critical for survival. The epithalamus consists of both nuclei and tracts. Studies on the development of the epithalamus in amniotes (reptiles, birds, and mammals) based on cytoarchitecture have commonly been part of a larger report on the embryogenesis of the diencephalon. Of these, observations on the epithalamus of reptiles are few with limited descriptions and figures. The present analysis fills this gap in knowledge by examining the development of the epithalamus in one group of reptiles, Alligator mississippiensis, using stains for cells and fibers. The time of origin and subsequent development of the nuclei and the tracts that course through the epithalamus were determined. These data provide a basis for future studies and for comparisons with other amniotes.