8 The Life of the Fish 



But to be known of his own kind is good for the sunfish, and 

 we may imagine that the black ear-flap with its scarlet edge 

 hel>s his mate and friends to find him out, where they swim on 

 his own level near the bottom. Such marks are called recognition- 

 marks, and a great many fishes have them, but we have no 

 certain knowledge as to their actual purpose. 



We are sure that the ear-flap is not an ear, however. No 

 fishes have any external ear, all their hearing apparatus being 

 buried in the skull. They cannot hear very much: possibly a 

 great jar or splash in the water may reach them, but whenever 

 they hear any noise they swim off to a hiding-place, for any dis- 

 turbance whatever in the water must arouse a fish's anxiety. 

 The color of the live sunfish is very brilliant. Its body is cov- 

 ered with scales, hard and firm, making a close coat of mail, 

 overlapping one another like shingles on a roof. Over these is a 

 thin skin in which are set little globules of bright-colored matter, 

 green, brown, and black, with dashes of scarlet, blue, and white 

 as well. These give the fish its varied colors. Some coloring 

 matter is under the scales also, and this especially makes the 

 back darker than the lower parts. The bright colors of the sun- 

 fish change with its surroundings or with its feelings. When it 

 lies in wait under a dark log its colors are very dark. When it 

 rests above the white sands it is very pale. When it is guarding 

 its nest from some meddling perch its red shades flash out as it 

 stands with fins spread, as though a water knight with lance at 

 rest, looking its fiercest at the intruder. 



When the sunfish is taken out of the water its colors seem to 

 fade. In the aquarium it is generally paler, but it will sometimes 

 brighten up when another of its own species is placed beside it. 

 A cause of this may lie in the nervous control of the muscles 

 at the base of the scales. When the scales lie very flat the color has 

 one appearance. When they rise a little the shade of color seems 

 to change. If you let fall some ink-drops between two panes of 

 glass, then spread them apart or press them together, you will 

 see changes in the color and size of the spots. Of this nature is 

 the apparent change in the colors of fishes under different con- 

 ditions. Where the fish feels at its best the colors are the richest. 

 There are some fishes, too, in which the male grows very brilliant 

 in the breeding season through the deposition of red, white, black, 



