The skin of the lancelet, Amphioxus lanceolatus, was investigated with the aid of the electron microscope and some histochemical techniques. It was shown that the single type of epidermal cells is capable of performing several activities. These cells produce and attach a thin mucous surface layer and it is also suggested that a primitive form of keratinization occurs in them. Furthermore they may produce pigment granules and serve as glycogen stores. A thin lamina below the epidermal cells cements their basal surfaces and is itself basally anchored in the underlying corium with the aid of an elaborate system of processes. The corium fibre layer in most cases rests upon a single fibrocyte layer. It is at irregular intervals penetrated by bundles of fibres which originate as branches of the corium collagen fibres.