Abstract Epidermal secretory cells of fishes are of two types, one type elaborating proteinaceous material and the other type secreting mucus. Epidermal toxins (crinotoxins and venoms) are produced by the protein-elaborating cells. Venoms appear to have evolved from crinotoxins. Crinotoxic fishes tend to have reduced squammation. Both crinotoxic and venomous fishes often adopt a sedentary or station-keeping mode of life.