The organization of the hippocampus of the fence lizard: a light microscopic study.

The hippocampus of the fence lizard (Sceloporus undulatus) is composed of two laminated regions that are readily distinguishable on the basis of position and perikaryal size in Nissl preparations: the small-celled (Hsc) and the large-celled (Hlc) hippocampal divisions. Based upon cellular and fibrillar characteristics, the layers of the Hsc are: (1) the superficial plexiform layer; (2) the cellular layer; (3) the deep plexiform layer; (4) the layer of deep fibers, or alveus; and, (5) the ventricular ependyma. The layers of the Hlc are: (1) the tangential layer; (2) the molecular layer; (3) the pyramidal layer; (4) the deep plexiform layer; (5) the alveus; and, (6) the ventricular ependyma. The neurons of each hippocampal layer were grouped into classes based upon somal position and appearance, and dentritic and axonal arborization patterns in Golgi sections. Neurons of the Hsc are more numerous and pleomorphic than those of the Hlc. Data do not suggest an intrinsic organization that closely parallels that found in the mammalian hippocampus.