Imagine for a moment the chances of life possessed by a bright scarlet animal among the snow-fields of Greenland, and one can see at once the absolute necessity for this unvarying protective coloration. Even a royal duke would scarcely venture to approve of flaring red uniforms under such conditions. All the conspicuous creatures get immediately weeded out by their carnivorous enemies, owing to their too great obtrusiveness and loudness of dress; while those alone survive which exactly conform to the fashionable whiteness of external nature. So, too, in the desert every bird, lizard, grasshopper, butterfly, and cricket is uniformly dressed in light sand-color. The intrusive red or blue butterfly from neighboring flowery fields gets promptly eaten up by the local bird, whose plumage he can not distinguish from the sand around it. The intrusive scarlet or green bird from neighboring forests finds the bread taken out of his mouth by the too severe competition of his desert brethren, who can steal upon the native grasshoppers unperceived, while he himself acts upon them like a red danger-signal, and is as sedulously avoided by the invisible insects as if he meant intentionally to advertise in flaming posters his own hostile and destructive purpose.
In short, sand-haunting creatures are and always must be necessarily sand-colored.
A few tropical flat-fish, however, living as they do among the brilliant corals, pink sea-anemones, gorgeous holothurians, and banded shells of the Southern seas, are beautifully and vividly spotted and colored with the liveliest patterns. In this case the necessity for protection compels the fish to adopt the exactly opposite tactics. All those young beginners which happen to show any tendency to plain brown coloring are sure to be recognized as fish, and get promptly eaten up among their bright surroundings; only those which look most like the neighboring inedible and stinging nondescripts stand any chance of escaping with their precious lives. A Quaker garb which would easily pass unobserved in the murky English Channel would become at once conspicuous by contrast among the brilliant organisms of Amboyna or Tahiti. This beautifully proves the relativity of all things, as philosophers put it. Ordinary people express the same idea in simpler language by saying that circumstances alter cases.
Most of our English flat-fish lie consistently on one side, and that the left; they keep their right eye always uppermost. But the turbot and the brill reverse this arrangement, having the left side on top and colored, while the right side is below and white. Two other fish, known as the fluke and the megrim, but not received in polite society, follow the example of their fashionable friends in this respect. But in no case are these habits perfectly ingrained; now and then one meets with a left-sided sole or a right-sided turbot, which looks as though a great deal were left to the mere taste and fancy of the individual flat-
