THE EVOLUTION OF METAMORPHOSIS IN AMPHIBIANS

A survey is provided of the external transformations that coincide with metamorphosis or a water‐to‐land transition, and of transformations during water‐to‐land transition in the retinal projection, the brain stem, the lateral‐line system, and the inner ear of amphibians. Among the three orders of amphibians, the frogs are characterized by more pronounced transformations during the water‐to‐land transition than are the other two orders. Some of the progressive and regressive changes in the sensory and nervous system are presented and a scenario is suggested for the evolution of these transformations among amphibians. Suggestions that metamorphosis in frogs can recapitulate the water‐to‐land transition of ancestral amniotic vertebrates are refuted. Copyright © 1990 John Wiley & Sons, Inc.