ADAPTATIONS OF FLAT-FISH 47 



In fact, a flat-fish, which begins life as a round fish, 

 balancing vertically, slips on to its right or left side, 

 which then becomes the colourless under surface, 

 whilst the other side is converted into a variably 

 tinted upper surface. The eye belonging to the side 

 upon the sea-bottom has rotated owing to a twist 

 of the orbit to the upper surface, upon which both 

 eyes thus appear to lie, and the animal, though flapping 

 through the water by vertical instead of horizontal 

 strokes, is still using its muscles relatively to itself 

 as they were employed before rotation. 



The skates and rays attain their flattened shape 

 by compression of the more rounded body seen in 

 sharks and dogfish, and by an enormous extension 

 of the first pair of fins to form the wings, which, grow- 

 ing and fusing with the body, give rise to that diamond 

 shape so characteristic of the skates. These fins are 

 now the chief organs of locomotion, and suitably so, 

 since they are specially adapted to a vertical move- 

 ment such as the skate requires, whilst the somewhat 

 slender tail gives the propulsion necessary for forward 

 movement. 



The attempts that fish have made from time to 

 time to walk and fly are of great interest. Many 

 balance themselves on their two pairs of fins and 

 grub or nose about the rocks under water ; but owing 

 to the unjoin ted nature of their limbs, this attitud 

 is extremely difficult to maintain on land. Yet 

 here and there shore-fish have adapted themselves 

 to a temporary land life. The gobies that swarm on 



