[CHAPTER XVI.]
Conclusions.
W
WE have now, more or less fully, examined into the system of colouration in the living world, and have drawn certain inferences from the facts observed.
It appears that colouration began—perhaps as a product of digestion—by the application of pigment to the organs of transparent creatures. Supposing that evolution be true—and, if we may not accept this theory there is no use in induction whatever—it must follow that even the highest animals have in the past been transparent objects. This was admirably illustrated by Prof. Ray Lankester in a lecture on the development of the eyes of certain animals, before the British Association meeting at Sheffield, in which it was shown that the eyes commenced below the surface, and were useful even then, for its "body was full of light."
Granting this, it follows that the fundamental law of decoration is a structural one. Assuming, as we do, that memory has played a most important part in evolution, it follows that all living matter has a profound experience in decorating its organs—it is knowledge just as anciently acquired, and as perfectly, as the power of digestion. This colour was produced under the influence of light—so it is even in opaque animals.
With a knowledge so far reaching, we might expect that even in opaque animals the colouring would still follow structural lines, and there should still be traces of this, more or less distinct.
This is precisely what we do find; and, moreover, we sometimes get a very fair drawing of the important hidden parts, even where least expected, as in a cat's head, a snake's body, a dragon-fly's thorax, a spider's abdomen, a bird's skull.
But if animals thus learned to paint themselves in definite patterns, we might expect that when called upon to decorate for the sake of beauty certain parts not structurally emphatic, they would adopt well-known patterns, and hence arose the law of repetition.
But with wider experience came greater powers, and the necessity for protection arising, the well-known patterns were enlarged, till an uniform tint is produced, as in the Java pig, or some repeated at the expense of others, as in the civets. But so ingrained is the tendency to structural decoration that even where modification has reached its highest level, as in the leaf-butterflies, some trace of the plan that the new pattern was founded on is recognisable, just as the rectangular basis can be traced in the arabesque ornaments of the Alhambra.