414 A HISTORY OF BIRDS 



and elastic organ to move away the mass of soil surrounding 

 the whole beak, a mechanism has been evolved whereby the 

 tips only of the jaws are opened sufficiently wide to allow of 

 the worm being grasped. The mechanism in question is simple, 

 and may be briefly described as follows : The beak of the 

 Snipe is formed by the elongation of the premaxilla and the 

 extension forwards of the narial fossa to within a short distance 

 of the tip of the beak. Thus is formed an upper and a lower 

 pair of lateral rods of great slenderness and elasticity. By the 

 contraction of muscles attached to the quadrate bones the pair 

 of inferior bars are thrust forwards, and this results in forcing the 

 tip of the beak upwards. The relaxation of the muscle brings 

 the curled-up tip down again so as to close upon the worm and 

 hold it securely until brought to the surface. This form of 

 beak, seen in perfection in the Snipes and Woodcocks, ap- 

 parently had its origin in the short bill seen in the Dunlin, 

 Stints and Sandpipers, for example. 



Few groups of birds show the influence of the quest for food 

 more admirably than the members of the Goose tribe, using 

 this term in its widest sense. The most ancient of this group 

 is undoubtedly represented by the Screamers of South America 

 (p. 48). The beak of these birds resembles that of a Fowl in 

 shape, and is used similarly for picking up seeds and other 

 vegetable matter on land, varied with succulent water-plants 

 obtained when on the water. These birds, as we have re- 

 marked, are probably the ancestors, or near allies of the 

 ancestors, of the Goose tribe, and, it may be remembered, 

 though aquatic in habits, have no webs to the toes. The next 

 stage in the evolution of the more typical Anserine bird we 

 get in the Black and White Goose, or Semi-palmated Goose 

 (Anseranas), wherein the toes are half-webbed, and the beak 

 has assumed a Goose-like form, having the edges of the jaws 

 provided with horny lamellae ; while the tongue has become 

 thick and fleshy and fringed with horny processes. The de- 

 velopment of this peculiar form of tongue, and of the horny 

 processes along the jaws, enable the bird to avail itself of the 

 rich stores of food in the shape of insects and other organisms 

 which teem in the water. These are captured by taking large 

 quantities of water into the mouth and expelling it by means of 

 the fleshy tongue, the lamellae of the jaws acting as a rough 



