The production of black and white, then, being the acme of colour production, we should expect to find these tints largely used for very special purposes. Such is actually the case. The sense organs are frequently picked out with black, as witness the noses of dogs, the tips of their ears, the insertion of their vibrissæ, or whiskers, and so on; and white is the most usual warning or distinctive colour, as we see in the white stripes of the badger and skunk, the white spots of deer, and the white tail of the rabbit. Colour, then, as expressed in definite tints and patterns, is no accident; for although, as Wallace has well said, "colour is the normal character," yet we think that this colour would, if unrestrained and undirected, be indefinite, and could not produce definite tints, nor the more complicated phenomenon of patterns, in which definite hues are not merely confined to definite tracts, but so frequently contrasted in the most exquisite manner. As we write, the beautiful Red Admiral (_V. atalanta_) is sporting in the garden; and who can view its glossy black velvet coat, barred with vividest crimson, and picked out with purest snow white, and doubt for an instant that its robe is not merely the product of law, but the supreme effort of an important law? Mark the habits of this lovely insect. See how proudly it displays its rich decorations; sitting with expanded wings on the branch of a tree, gently vibrating them as it basks in the bright sunshine; and you know, once and for all, that the object of that colour is display. But softly--we have moved too rudely, and it is alarmed. The wings close, and where is its beauty now? Hidden by the sombre specklings of its under wings. See, it has pitched upon a slender twig, and notice how instinctively (shall we say?) it arranges itself in the line of the branch: if it sat athwart it would be prominent, but as it sits there motionless it is not only almost invisible, _but it knows it_; for you can pick it up in your hands, as we have done scores of times. It is not enough, if we would know nature, to study it in cabinets. There is too much of this dry-bone work in existence. The object of nature is _life_; and only in living beings can we learn how and why they fulfil their ends. Here, in this common British butterfly, we have the whole problem set before us--vivid colour, the result of intense and long continued effort; grand display, the object of that colour; dusky, indefinite colour, for concealment; and the "instinctive" pose, to make that protective colour profitable. The insect _knows_ all this in some way. How it knows we must now endeavour to find out.