OPTIC NERVE FIBRE COUNTS AND RETINAL GANGLION CELL COUNTS DURING DEVELOPMENT OF XENOPUS LAEVIS (DAUDIN)

Abstract

An account is given of the development of the optic nerve in Xenopus laevis (Daudin). The stages studied were 35, 38, 46, 52, 58, immediately post‐metamorphosis (66), the juvenile of six months from metamorphosis and the adult. Fibre counts were made from complete electron micrograph montages for all the stages investigated including the adult. Corresponding ganglion cell counts were made from sections prepared by light microscopic histology from stage 46 upwards. The large increase found in the ganglion cell population during development was also found in the optic nerve fibre counts. There was an approximate 1 : 1 relationship between the optic nerve fibres and the retinal ganglion cells. The number of fibres increased from less than 1,000 (stage 35) to 59,000 (six‐month‐old juvenile). The older adult animal possessed fewer unmyelinated fibres than the six month old juvenile, but twice as many myelinated fibres, so producing a smaller total number. It seems that the process of myelination continues well into adult life. © 1971 The Physiological Society