There comes periodically to this country a bird of the starling kind, known as the rose-coloured pastor. It has the back, breast, and sides of an exquisite pale pink; and it is perhaps this bright plumage which prevents it from establishing a residence here. In its continental haunts the bird is observed to affect trees or shrubs bearing rose-coloured flowers, such as the blossoms of the pink azalea, among which the birds more easily escape notice. This is an instance of what is known as adaptive or protective coloration, which we need not go abroad to observe. The struggle for existence among plants and animals is a hard one, and every point gained in the direction tends to survival. The modification in the forms and colours of insects, and the successful shifts thereby made to elude their enemies, provide the striking facts of the case. Birds modify and rearrange the colours of their plumage, adapt the coloration of their eggs, and the structure and material of their nests, all to the same end. We know that the more highly organised flowers have changed form and colour to satisfy their insect visitors, while the insects themselves have modified their organs so as to enable them the better to visit certain flowers. In Sumatra Mr. Wallace found a large butterfly, its upper surface of a rich purple and with a broad bar of deep orange crossing each wing. The species is found in dry woods and thickets, and when on the wing is very conspicuous. Among the bush and dry leaves the naturalist was never able to capture a specimen; for, however carefully he crept to the spot where the insect had settled, he could never discover it until it suddenly started out again. But upon one occasion he was fortunate enough to note the exact spot where the butterfly settled, and, although it was lost sight of for some time, he at length discovered it close before his eyes. In its position of repose it exactly resembled a dead leaf attached to a twig. So in our own country we may observe that the purple emperor butterfly affects certain of the brightly coloured wild geraniums, upon which, in repose it is almost impossible to detect it. The brown-spotted fritillaries of our birch woods also offer examples of this class, it being difficult to detect them against the fungus-pitted leaves of every shade of brown and dun and yellow. VII. HOW THE WORLD IS FERTILISED.