In addition to those usually mentioned in textbooks on comparative anatomy, the anuran skin contains, in many species, a layer situated between the stratum compactum and the stratum spongiosum which is acellular and which has a selective tinctorial affinity for Alizarine, haematoxylin, Alcian Blue and ionized iron. The indications are that this layer consists of acid mucopolysaccharides and calcium. This layer is most prominently developed in the more differentiated anuran families. It is almost entirely absent in the aquatic species but predominantly present in the terrestrial forms. Presumably this layer plays an important part in the defence mechanism of the Anura against desiccation.