The MUTE SWAN (_Cygnus olor_), the species so frequently seen in this country living upon our ornamental water in a state of semi-domestication, and sometimes described by writers as the "Tame Swan" (_Cygnus mansuetus_) is, in its wild state, an inhabitant of Northern Europe and Northern Asia, more especially of Eastern Siberia, and is easily recognisable by the callous protuberance at the base of its bill. Its body is elongate, its neck extremely long and slender, and its bill, which is nearly of the same length as the head, of a red colour, surmounted at its base with the black knob-like protuberance above alluded to. The plumage of the adult is white, that of the young grey, or occasionally white. The eye is brown, the beak red, while the bridles and protuberance at the base of the beak are black; the feet brownish or pure black. This bird is seventy inches long, and one hundred inches broad; the length of the wing is twenty-seven inches, and of the tail ten to eleven inches; the female is not quite so large. Brehm is of opinion that the Polish Swan (_Cygnus immutabilis_) of Yarrell, is merely a variety of the above species, but the following extract from a paper, read by Yarrell before the Zoological Society, will give our readers that naturalist's reasons for maintaining that these birds are not identical, although in their appearance, habits, and mode of life, they closely resemble each other. "The London dealers in birds," he says, "have long been in the habit of receiving from the Baltic a large Swan which they distinguish by the name of the Polish Swan. During the severe weather of January, 1838, several flocks of these Polish Swans were seen pursuing a southern course along the line of our north-east coast, from Scotland to the mouth of the Thames, and several specimens were obtained. The circumstance of these flocks being seen without any observable difference in the specimens obtained, all of which were distinct from our Mute Swan; the fact also that the Cygnets, as far as we observed, were of a pure white colour like the parent birds, and did not assume at any age the grey colour borne for the greater part of the first two years by the young of the other species of Swans; and an anatomical distinction in the form of the cranium, which was described by Mr. Pelerin in the _Magazine of Natural History_, induce me to consider this Swan as a distinct species, and in reference to the unchangeable colour of the plumage, I proposed for it the name of _Cygnus immutabilis_."