The Eyelids and Spectacle in Geckos

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Abstract
Summary.: The eye‐coverings of three species of geckos belonging to the genera Coleonyx, Stenodactylus and Ptenopus have been studied by means of serial sections. In Coleonyx true eyelids and probably a small nictitating membrane are present and there is no brille or spectacle. The relationships of these structures to the cornea, Harderian gland ductules and lachrymal canaliculi are essentially similar to those in Lacerta, and conform to the characteristic saurian pattern. In Stenodactylus and Ptenopus a brille is present, and is surrounded by prominent extra‐brillar fringes. These structures are very extensive in Ptenopus and contain muscle fibres. The relationship of these fringes to the ductules of the Harderian gland and to the lachrymal canaliculi which open into the subbrillar space indicates, however, that the fringes cannot be regarded as homologous with the eyelids of other lizards. By demonstrating that true eyelids and a brille are not found in association, these findings are regarded as evidence for the palpebral origin of the brille in geckos which is therefore homologous with that in snakes.