The Life of the Fish 9 



or blue pigments, or coloring matter, on its scales or on its head 

 or fins, this pigment being absorbed when the mating season is 

 over. This is not true of the sunfish, who remains just about 

 the same at all seasons. The male and female are colored 

 alike and are not to be distinguished without dissection. If we 

 examine the scales, we shall find that these are marked with fine 

 lines and concentric striae, and part of the apparent color is due 

 to the effect of the fine lines on the light. This gives the bluish 

 lustre or sheen which we can see in certain lights, although we 

 shall find no real blue pigment under it. The inner edge of each 

 scale is usually scalloped or crinkled, and the outer margin of 

 most of them has little prickly points which make the fish seem 

 rough when we pass our hand along his sides. 



The Lateral Line. Along the side of the fish is a line of 

 peculiar scales which runs from the head to the tail. This is 



FIG. 4. Ozorthe dictyogramma (Herzenstein). A Japanese blenny, from Hakodate: 

 showing increased number of lateral lines, a trait characteristic of many fishes of 

 the north Pacific. 



called the lateral line. If we examine it carefully, we shall see 

 that each scale has a tube from which exudes a watery or 

 mucous fluid. Behind these tubes are nerves, and although not 

 much is known of the function of the tubes, we can be sure that 

 in some degree the lateral line is a sense-organ, perhaps aiding 

 the fish to feel sound-waves or other disturbances in the water. 

 The Fins of the Fish. The fish moves itself and directs its 

 course in the water by means of its fins. These are made up of 

 stiff or flexible rods growing out from the body and joined to- 

 gether by membrane. There are two kinds of these rays or rods 

 in the fins. One. sort is without joints or branches, tapering to 

 a sharp point. The rays thus fashioned are called spines, and 

 they are in the sunfish stiff and sharp-pointed. The others, 



