Not only does a brook assume different aspects, according to the individuality of the spectator, but every brook has its individuality, and so have its banks. Often the brook "plays many parts," as in Burns' delightful stanza, which seems to have rippled from the poet's brain as spontaneously as its subject. Sometimes, however, as near Oxford, it flows silently onwards with scarcely a dimple on its unruffled surface. Over its still waters the gnats rise and fall in their ceaseless dance. The swift-winged dragon-flies, blue, green, and red, swoop upon them like so many falcons on their prey; or, in the earlier year, the mayflies flutter above the stream, leaving their shed skins, like ghostly images of themselves, sticking on every tree trunk near the brook. On the surface of the brook are seen the shadow-like water-gnats, drifting with apparent aimlessness over the surface, but having in view a definite and deadly purpose, as many a half drowned insect will find to its cost. Under the shade of the willows that overhang its banks the whirligig beetles will gather, sociably circling round and round in their mazy dance, bumping against each other in their swift course, but glancing off unhurt from the collision, protected from injury by the stout coats of mail which they wear. They really look like unskilful dancers practising their "figures" for the first time. They, however, are not engaged in mere amusement, but, like the water-gnats, are absorbed in the business of life. The naturalist knows, when he sees these creatures, that they do not form the hundredth part of those which are hidden from human eyes below the surface of the little brook, and that the whole of the stream is as instinct with life, as if it had been haunted by the Nipens, the Undines, and the host of fairy beings with whom the old legends peopled every river and its tributaries. They are just as wonderful, though clad in material forms, as any water spirit that ever was evolved from the poet's brain, and have the inestimable merit of being always within reach whenever we need them. I will venture to assert that no fairy tales, not even excepting those of the "Arabian Nights," can surpass in marvel the true life-history of the mayfly, the frog, the newt, and the dragon-fly, as will be narrated in the course of these pages. I may go even farther, and assert that there is no inhabitant of the brook and its banks whose biography and structure are not full of absorbing interest, and will not occupy the longest life, if only an attempt be made to study them thoroughly.