in the wing, sometimes in some other organ. The sequence of plumage affords abundant evidence of this. But that is another story. So much for the "intensive" study of the wing. A brief reference must now be made to the constantly repeated statement that nestling birds are "taught" to fly by their parents. There is no evidence whatever to support this belief: and much that goes to show its improbability. Failing more suitable sites, sand-martins will often elect to build their nests in the crevices of the masonry of bridges. From the mouth of this substitute for a burrow is often a sheer drop of many feet to the stream below. When the nestlings, fully fledged, leave their nursery for the first time they must either "fly" from the moment they take the first plunge from the masonry, or die. Failing to make the appropriate movements of the wings nothing can save them from a watery grave. There can be no "teaching" to fly. Indeed, death no less certainly awaits every house-martin when it plunges into space from the edge of the nest. The appropriate wing-movements, necessary to produce flight, in short, are "instinctive." Those with defective instincts are forthwith killed by falling to the ground. They leave no offspring to inherit their defects. Perhaps the most convincing evidence of all as to the "instinctive" nature of flight, in nestling birds, is furnished by the mound-birds, of the Malay Region and Eastern Australia. These extraordinary birds lay their eggs in heaps of decaying vegetable-matter, or in the soil near hot springs; and there leave them to their fate. They lay very large eggs, it is to be noticed, so large that the growing chick finds nourishment enough within the egg to enable it to pass the ordinary nestling stage while still within the shell. By the time it emerges it has both grown and shed its first coat of nestling-down, and has developed long wing-quills. Having burst its prison walls it wriggles its way up through the loose earth, to the light of day, ready to fight its way in the world unaided. Here, then, there can be no question of "teaching" the young to fly.