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8 The Life of the Fish 
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 stric, and part of the apparent color is due 
to the effect of the fine ines 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 
Fic. 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, 
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