The peculiar structure of the feet in the arboreal races is evidently adapted to a life amongst the branches of trees: the outer toe can be directed backwards like a thumb, enabling them to grasp the boughs as with a hand. If, leaving the trackless gloom of the forest, we approach the sylvan scenery of the surrounding country, the "bosky woods" and isolated trees, or the sparse undergrowth of bushy shrubs, we find innumerable forms that have their feet contrived for _perching_ only. These INSESSORIAL races, called also PASSERES, from their general resemblance to sparrows, live upon insects, fruit, and grain; but those with strong beaks live more exclusively upon grain, and those with slender beaks upon insects. The proportional length of their wings is as variable as their habits. They have four toes, generally so disposed that there are three in front and one behind; sometimes all four in front. Their legs are slender, and they hop rather than walk. The forests and the trees, the bushes and the brakes, the thickets and the hedgerows, being thus provided with appropriate denizens, we turn our attention to the level ground; and here we find species as obviously designed for a terrestrial existence as were the preceding groups for a residence among the branches. The terrestrial or GALLINACEOUS birds live principally upon the ground. Their body is large and heavy, and their wings short and rounded, so as to be but ill adapted to prolonged flight. They have three toes in front, which are united at their base by a short fold of the skin, and their hinder toe is affixed above the level of the rest. In many species the male is provided with formidable weapons in the shape of _spurs_. To this order belong the turkeys, pheasants, and barn-door fowls. Their legs are thick, strong, and muscular, their toes short and powerful. They always prefer running to flying, and, indeed, will rarely take to their wings, except when compelled to do so by the urgency of the occasion. If any doubt could be entertained as to the terrestrial character of the gallinaceous birds, there can be none whatever as to those distinguished by the name of CURSORES or runners. The principal characteristic of the cursorial race consists in the undeveloped condition of their wings, which are quite disproportioned to the size of their body. In some cases these rudimentary wings are but imperfectly furnished with feathers, and seem only to be used after the manner of sails, to catch the wind, and thus assist in running. The living species form two families, of one of which the Ostrich, and of the other the Apteryx, is the type.