THE TONGUES OF BIRDS. 



1019 



able that the barbs make their appearance at, or shortly after, the time 

 the bird leaves the nest, when the young cease to be fed and begin to 

 feed themselves, but a little positive evidence in the shape of speci- 

 mens is needed to settle the question. 



In birds with shorter tongues than those just described the changes 

 during growth are, naturally, not so marked; but even in tongues like 

 those of the chimney swift and screech owl there is a very obvious 

 difterence between the tojigue of the embryo, or nestling, and that of 

 the adult. 



The question of growth with its change of form connected with 

 change of food, or in the manner of getting it, is worthy of careful con- 

 sideration, but perhaps the most interesting problem presented by the 

 tongues of birds is whether underlying the infinite modifications of 

 the tongue are certain definite forms which may be of use in classifica- 

 tion, or whether these forms are all cases of adaptation to particular 

 kinds of food. 



The evidence seems to point plainly in the latter direction, but what 

 is needed is a large collection of carefully sifted and assorted facts. 



Fig. 13. 



