_Necturus maculatus_ s. _Menobranchus lateralis_.–The eyes are functional, being covered by the thin transparent skin. The limbs, although short, are well developed, and have four fingers and four toes. The whole animal, which reaches the length of one foot, is quite smooth and slimy, brown with irregular dark, blackish spots and patches, which frequently form a dark lateral band extending from the mouth to the tail. The latter, which measures about one-third of the whole length, is strongly compressed, carries a thick dorsal and ventral fin, and is rounded off at the end. The skin of the throat forms a strongly-marked transverse fold. The thick stalks of the gills are brown, while the numerous and delicate fringes are dark red in life; beneath and behind them are two gill-clefts. _N. maculatus_ is found in the eastern half of the United States, chiefly the eastern part of the basin of the Mississippi and the Canadian lakes. {133}These creatures are rather dull; they remain mostly at the bottom of the water, more or less concealed in the weeds or between rocks during the daytime. Mine, which are kept in a roomy, light-coloured tank, lie motionless, with their gills spread out transversely. Every now and then the gills contract suddenly and become pale, whereupon they are filled again with blood. Very rarely they rise to the surface, but tiny air-bubbles are let out more frequently, especially when the animals are disturbed. Then the gills collapse, are laid flat against the neck, and the creature darts about with quick, eel-like motions. At night they leave their hiding-places, swim about or creep along the ground with slow, undulating movements, the limbs being scarcely used, in search of food, which in their wild state consists of rather large Crustacea, small fishes, worms, insects and frogs. They are most voracious, and absolutely indifferent to cold. The spawning takes place in the months of April and May. _Proteus anguinus._–The fore- and hind-limbs are fully developed, but possess only three fingers and two toes. The eyes are completely hidden beneath the opaque skin. This peculiar creature is restricted to the subterranean waters of Carniola, Carinthia, and Dalmatia. The vast caves of Adelsberg not far from Trieste are especially celebrated for the occurrence of the "Olm," the German name of this animal. The river Poik, a moderate mountain-stream, but a large, fierce torrent during the rainy season, disappears into the limestone-hills, and rushes through enormous stalactite-grottoes, most of which have been only partially explored, until several miles farther on it reappears on the surface. There, deep down below the surface, in absolute darkness, in an almost constant temperature of about 50° F. is the home of _Proteus_.