154 NEW ZEALAND NATURE-STUDY BOOK 
side by side and close together. The mouth is small, 
having both jaws furnished with fine pointed teeth. There 
are two pectoral fins immediately behind the gill slits. 
The dorsal and anal fins are prolonged into a fringe 
running completely round the body. 
Development of Fish. The upper and under 
surfaces correspond to the two sides of the body, as 
shown by the presence of the lateral line and the horizontal 
Fig. 101.—The Flounder. 
position of the tail: that is, the animal spends its life with 
one side of its body uppermost. When newly-hatched, the 
young fish are spindle-shaped and swim about near the 
surface, back uppermost, but, as they grow older, they 
become broader and thinner, assuming a shape which 
renders it difficult to maintain an upright position. They 
are for this reason gradually compelled to lie on one side, 
and ultimately lose the power altogether of maintaining 
the normal position. 
Movement of Eye. When the fish is young, the eyes 
are one on either side of the head. As the animal grows 
older, however, and swims on its side along the bottom, the 
