44 MARVELS OF FISH LIFE 
when divided with a knife down the back from the 
snout to the tip of the tail, the two halves are similar 
in their structure, and in the organs they contain, the 
wing-like fins on either sides being the modified pectoral 
fins, which have extended along each border. 
The flat fish, on the other hand, has been flattened 
from side to side, so that when divided in a similar 
manner the back with its muscles would be in one half, 
and the organs of digestion in the other half. Later, 
when considering the plaice, we shall see how this fish 
starts life as a rounded larva, then becomes flat, and 
falls over on its side. 
Flattening and coloration are not the only means of 
assisting the ray in the struggle for existence. The 
sting-ray is armed with a murderous barb, near the end 
of the tail, with which he is able to inflict a terrible 
wound; the torpedo ray is able to paralyse fishes by 
giving them an electric shock, and all rays possess sharp 
spines on their backs. The thornback ray is particularly 
well armed with these spines, hence its name. 
