Nevertheless, though animals have other means of recognition, the distinctive markings are, without doubt, the prime means of knowledge. Who, that has seen a peacock spread his glorious plumes like a radiant glory, can doubt its fascination? Who, that has wandered in America, and watched a male humming-bird pirouetting and descending in graceful spirals, its whole body throbbing with ecstasy of love and jealousy, can doubt? Who can even read of the Australian bower-bird, lowliest and first of virtuosi, decorating his love-bower with shells and flowers, and shining stones, running in and out with evident delight, and re-arranging his treasures, as a collector does his gems, and not be certain that here, at least, we have the keenest appreciation, not only of colour, but of beauty--a far higher sense? It has been said that butterflies must be nearly blind, because they seldom fly directly over a wall, but feel their way up with airy touches. Yet every fact of nature contradicts the supposition. Why have plants their tinted flowers, but to entice the insects there? Why are night-blooming flowers white, or pale yellows and pinks, but to render them conspicuous? Why are so many flowers striped in the direction of the nectary, but to point the painted way to the honey-treasures below? The whole scheme of evolution, the whole of the new revelation of the meanings of nature, becomes a dead letter if insects cannot appreciate the hues of flowers. The bee confines himself as much as possible to one species of flower at a time, and this, too, shows that it must be able to distinguish them with ease. We may, then, take it as proven that the power of discriminating colours is possessed by the lower animals. [Illustration] [7] Pl. I., Figs 1-3. [8] Pl. II., Figs. 1-3. CHAPTER V. THE COLOUR SENSE. The previous considerations lead us, naturally, to enquire in what manner the sense of colour is perceived.