THE ACCESSORY OPTIC-SYSTEM IN THE FROG, RANA-PIPIENS - AN ELECTRON-MICROSCOPIC STUDY OF THE RETINAL AFFERENTS UTILIZING THE ANTEROGRADE TRACER BIOCYTIN

The retinal afferents to the basal optic nucleus in the frog, Rana Pip iens, were labeled anterogradely with biocytin and subsequently studie d at the electron microscopic level. Labeled synaptic terminals in the nucleus varied in size from 0.5 mu m to 2.0 mu m and made symmetric s ynaptic contacts with large and small dendrites, although very rare ax ospinous and axosomatic contacts were also demonstrated.