274 



PRACTICAL ZOOLOGY 



are arranged in oblique rows on the fish's body and overlap each 

 other like the shingles on the roof of a house (Fig. 155). In such 

 fish as the gar pike (Fig. 163, C) the scales are very thick and 

 strong and diamond-shaped (Fig. 158, B); very few animals are 

 able to penetrate such an armor. Sharks and rays (Figs. 161 and 

 162) possess a covering of toothlike scales (Fig. 158, A), which 

 actually develop into teeth in the mouth region. The spines 

 of some fishes develop from scales, and bony plates such as those 



of the sturgeon (Fig. 163, 

 A) have a similar origin. 

 COLOR. The colors of 

 the fish are more impor- 

 tant as a protection than 

 the scales since they tend 

 to conceal the animal 

 amid its surroundings. 

 The red, orange, yellow, 

 and black pigments pres- 

 ent in the skin (Fig. 159) 

 may give the fish these 

 colors or else blend to 

 form other colors. The structure of the scales may also produce 

 certain colors due to reflection and iridescence. 



Usually the colors are arranged in a definite pattern consisting 

 of transverse or longitudinal stripes and spots of various sizes. 

 Coral-reef fishes have long been famous for their brilliant colors, 

 and many fresh-water fishes of the temperate zone exhibit 

 bright hues distributed so as to form striking and intricate 

 patterns (e.g. the rainbow darter). A few fish are able to change 

 their colors so as to match the bottom on which they lie; this is 

 true of the flounder (Fig. 171). 



Sensations. Fishes possess all of the five senses, but the 

 sense organs differ somewhat frcm those of land animals. 



The eyes (Fig. 155, e) are usually without lids, since the water 

 keeps the eyeball moist and free from foreign matter. The pupil 



FIG. 159. Pigment bodies in the skin of 

 a fish. (After Cunningham.) 



