The ontogeny of the eye of Dermophis mexicanus is typical of that of most vertebrates, though components of accommodation never develop. The pattern of retention of extrinsic muscles varies. Morphological evidence indicates that the eye is a functional photoreceptor in virtually all species examined, with an intact retina and optic nerve. Caecilians (Amphibia, Gymnophiona) have been reported to have ‘vestigial’ eyes, to lack some or all of the extrinsic eye muscles and their nerves, and to utilize eye muscles and glands, or derivatives of them, to effect movement of the tentacle, a chemosensory structure unique among vertebrates.
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