cularization of respiratory surfaces in amphibians have shown considerable differences existing among species in the intensity of vascularization of the skin, lungs, and mouth, as well as in the length of capillaries vascularizing each of these surfaces per gram of body mass. In some species the number of lung capillaries predominates over that of the skin, while in others the number per gram of body mass is nearly the same (Bombina bombina, metamorphosed individuals of Ambystoma mexicanum). In small species the skin contains the majority of all respiratory capillaries (Leiopelma hochstetteri, Triturus cristatus, T. alpestris). In the early developmental stages of amphibians, the skin contains the greater number of respiratory capillaries. The mouth in most of the amphibians investigated constituted hardly 1 percent of all respiratory capillaries (Czopek and Szarski, 1954; Czopek, Pugaczewska, and Sopocko, 1954; Czopek, 1955; Czopkowa and Czopek, 1955; Broda, 1956; Strawiniski, 1956; Czopek, 1957). It may be surmised that the vascularization of respiratory surfaces in Triturus vulgaris is similar to that in T. cristatus and alpestris. In the breeding season the richly vascularized tail-fin, particularly well developed in males, could be expected to produce an increase of the role of gas-exchange through the skin. This supposition is confirmed by the investigations carried out by Bannikov (1948), who examined the survival ability of breeding and normal specimens of T. vulgaris and cristatus placed in water and deprived of atmospheric oxygen. His experiments showed that breeding specimens were able to survive in water longer than non-breeding ones and that males survived longer than females. The aim of the present study was to investigate the vascularization of respiratory surfaces in breeding and non-breeding specimens of T. vulgaris.