420 A HISTORY OF BIRDS 



of the mechanism of the beak have not yet been completely- 

 worked out ; but suffice it to say when the pterygoids are 

 thrust forward the movement is passed on to the palatines, and 

 these by their forward movement thrust the upper jaw upwards 

 by its hinge. The under side of the hook of the jaw is tra- 

 versed by fine striations, having a characteristic arrangement 

 in different groups. These impart a roughness to the beak 

 useful in holding slippery and hard-shelled seeds. In the 

 small Parrakeets, e.g., Melopsittacus undulatus (Budgerigar) this 

 beak, as is well known, is very small and inconspicuous. From 

 this we may pass through a gradually increasing series to the 

 huge beak of the Macaws, terminating in the enormous jaws of 

 the Black Cockatoo {Microglossus aterrimus). This bird, says 

 Wallace, " has a rather . small and weak body, long weak legs, 

 large wings, and an enormously developed head . . . armed 

 with a sharp-pointed hooked bill of immense size and strength. 

 . . . The tongue is a curious organ, being a slender fleshy 

 cylinder of a deep red colour, terminated by a horny black 

 plate, furrowed across and somewhat prehensile. ... It eats 

 various fruits and seeds, but seems more particularly attached 

 to the kernel of the kanary-nut, which grows on a lofty forest 

 tree {Canarium commune), abundant in the islands where this 

 bird is found ; and the manner in which it gets at these seeds 

 shows a correlation of structure and habits which would point 

 out the ' Kanary ' as its special food. The shell of this nut is 

 so excessively hard that only a heavy hammer will crack it : 

 in shape it is somewhat triangular and the outside is quite 

 smooth. The manner in which the bird opens these nuts is 

 very curious. Taking one endways in its bill and keeping it 

 firm by a pressure of the tongue, it cuts a transverse notch by 

 a lateral sawing motion of the sharp-edged lower mandible. 

 This done, it takes hold of the nut with its foot, and biting off 

 a piece of leaf retains it in the deep notch of the upper mandible, 

 and again seizing the nut, which is prevented from slipping by 

 the elastic tissue of the leaf, fixes the edge of the lower 

 mandible in the notch, and by a powerful nip breaks off a 

 piece of the shell. Again taking the nut in its claws, it inserts 

 the very long and sharp point of the bill and picks out the 

 kernel, which is seized hold of, morsel by morsel, by the ex- 

 tensile tongue. Thus every detail of form and structure in 



