I will pluck a scale from this brilliant silvery surface. Its hinder, or free edge, is beset with fine flexible crystalline points, arranged in many successive rows, overlapping each other. The front, or attached edge, is cut in a scolloped pattern, the extremities of undulations that radiate from a common point behind the centre. The whole surface, except the hinder portion that is studded with imbricated points, is covered with an immense multitude of fine concentric lines, which follow the form of the general outline. These are marks of successive increase; for every one of the lines is the margin of a lamina, the aggregation of which makes up the thickness of the scale. The laminae can be separated by long maceration in water; and then we see that they are laid one on another in regular order, the uppermost being the smallest, and the first formed; the last made, which is the largest, being now in contact with the skin. [Illustration: SCALE OF GILTHEAD.] Every scale is therefore a document, on which is indelibly written the record of a multitude of processes, all effected in the past history of the fish. The successively deposited laminae are exactly analogous to those of calcareous substance in the shell of the bivalve;[81] and the evidence is of exactly the same character as what we lately read off from the valve of the _Dione_. But, just as in that example, too, the overruling fact of recent creation precludes our deduction of time from the evidence, since it proves the development to have been prochronic. I see yonder a more terrific tyrant of the sea than the Sword-fish. It is the grisly Shark (_Carcharodon_). How stealthily he glides along, cutting the glittering surface of the sea with his dorsal, and now and then protruding just the tip of the upper lobe of his caudal in the wake of the other! Let us go and look into his mouth; for neither animals nor elements present any impediments to these investigations of ours. Is not this an awful array of knives and lancets? Is not this a case of surgical instruments enough to make you shudder? What would be the amputation of your leg to this row of triangular scalpels, each an inch and a half in diameter? moved, too, by these powerful muscles?