HOW A BIRD FEEDS. 45 



other organ of the body, is capable of being slowly 

 but surely modified and changed like clay under 

 the thumb of the potter. Sometimes this change 

 is one of progression, the tongue becoming more 

 and more complex and more and more perfectly 

 fitted for its peculiar purpose : sometimes it is 

 rather one of suppression as the tongue becomes 

 less and less in size, in proportion as the need 

 for its existence decreases, till at last, as in our 

 cormorant and gannet, only a mere vestige of it 

 is left. For it is a fact that so soon as an organ 

 ceases to be useful, so soon as it ceases to work, 

 its fate is sealed and slowly but surely it is re- 

 moved from the body, or remains an insignificant 

 vestige by which all men may measure the dis- 

 tance which it has fallen. 



We cannot do more here than examine a few 

 of the more remarkable tongues. 



Take the common duck for instance, a bird 

 familiar to us all. The tongue in this bird is very 

 thick and fleshy, and provided on each side with 

 little horny plates, and at its tip with a kind of 

 horny spoon. The horny bristle-like plates at 

 the side fit into similar horny plates w^hich form 

 a sort of fringe round the inner edge of the beak ; 

 the purpose of these plates is to form a sort of 

 strainer, by which the bird is enabled to strain 

 off the water which it takes in with its food. 

 The arrangement of these plates suggests that of 

 the whalebone in the mouth of the whale, and are 

 used for a precisely similar purpose. These 

 plates are best seen in one of our fairly common 

 wild ducks, called the shoveller. In this bird 

 they are of great size. 



