_S. atra._–The Alpine Salamander differs from the Spotted Salamander by its uniform black colour and smaller size, which averages between 7 and 5 inches. It is restricted to the Alps of Europe, from Savoy to Carinthia, at from 2000 to as much as 9000 feet elevation, living with predilection near waterfalls, the spray of which keeps the neighbourhood moist, or in mossy walls, in the shade of forests near brooks, or under flat stones on northern slopes. The most interesting feature of this species is that it produces only two young at a time. These are nourished at the expense of the partially developed eggs in the uterus, and they undergo their whole metamorphosis before they are born. By far the best and most complete account of this mode of propagation has been given by G. Schwalbe.[58] The length of the ripe embryos is about 45 mm.; they lie mostly bent up, with their heads and tails turned towards the head of the mother. The gills are beautiful, delicate red organs, the first pair being generally directed forwards and ventralwards, the second upwards, the third backwards; they are longest when the creature is about 32 mm. long, while there is still much yolk present. At this stage the gills are so long as to envelop nearly the whole embryo. There is rarely a second embryo in the same uterus, and an extra foetus is generally smaller, frequently a monstrosity not fit to live; it is probable that it is not used as food, but that it is expelled at parturition. The embryo passes through three stages, (1) still enclosed within its follicle and living on its own yolk, (2) free within the vitelline mass which is the product of the other eggs, (3) there is no more vitelline mass, but the embryo is possessed of gills 10-12 mm. in length, and is still growing. During the {120}second stage the yolk is directly swallowed by the mouth. The walls of the maternal uterus are rather red. The exchange of nutritive fluid takes place through the long external gills, which thereby function in the same way as the chorionic villi of the Mammalian egg. Each gill contains a ventral artery and a dorsal vein, each of which looks like the midrib of a pinnate leaf; there is also a fine nerve and a weak bundle of striped muscular fibres. Each gill-filament receives a capillary artery which extends to the epithelium of the tip, where it turns into a capillary vein. The epithelium of these filaments, which are full of blood, is ciliated, the resulting current being directed from the base towards the tip. In older larvae this ciliation becomes restricted to the tips. The body of the gills is furnished with flat epithelium, these non-ciliated portions alone are closely appressed to the uterine wall, and it is here that the exchange of gas takes place between mother and larva. The nutrition takes place through the gills, as they are bathed by the yolk-mass.