Modification of the Ectoderm in Sphenodon

Abstract

IN a recent publication1, attention has been directed to the occurrence of a peculiar modification of the outer layer of the ectoderm of the chorion (and choriogenous ectoderm) of Sphenodon (Reptilia, Rhynchocephalia) to produce very large cells with well-marked boundaries, domed free edges and large nuclei. These modified cells show particularly clearly in preparations stained with borax carmine, in which the cells tend to assume a characteristic yellow–orange colour. These cells were first observed by Dendy2 and Schauinsland3, who were working independently on the embryology of Sphenodon. They applied the term ‘teloderm’ to the tissue, a term previously used by Mehnert4 to describe tissue to which the term ‘epitrichial layer’ more properly applies5.