HAIBS, FEATHERS, AND SCALES. 



19 



line. Along each side, in most fishes, may be observed a 

 line, known as the lateral line, formed by scales of peculiar 

 form. They are commonly more bony than the other 

 scales, and are pierced by a tubular orifice for the escape 

 (as is generally supposed, though this has been denied) of 

 a mucous secretion, which is poured out from glands be- 

 neath, and thus flows over the body for the double purpose 

 of protecting the skin from the macerating influence of 

 the surrounding water, and of diminishing friction in 

 swimming. 



Let us now look at some scales of the cycloid kind. 

 The great majority of our fishes are clothed with such as 

 are of this description. This dead Gold-fish shall give us 

 examples. The three scales in the upper row are from 



SCALES OF GOLD-FISH. 



the lateral line, the left-hand one (a) taken just behind the 

 head, the second (b) near the middle of the body, and the 

 right-hand one (c) near the tail. Of the lower row, the 

 first (d) is from the back, the second (e) from the middle 

 c 2 



