ADAPTATIONS 427 



their food whole, and of large bulk, it becomes reduced to a mere 

 nodule, as in the Cormorant and Gannet. This vestigial con- 

 dition, however, is not correlated with this particular method of 

 feeding, since in the Stork, Ibis and Spoon-bill, which feed on 

 small animals, this organ is equally degenerate, so that the prob- 

 able explanation of its decay in such forms is to be attributed 

 to lack of use. In the majority of cases adaptation to the needs 

 of the animal is clearly traceable. Thus among raptorial birds 

 which feed on living prey the tongue is fleshy and somewhat 

 spoon-shaped, and this is true also of the Owls, while in their 

 allies the N ight-jars it is quite degenerate. In the Carrion-feeding 

 Vultures again we meet with the same parallels, since in both the 

 Old and New World types, which are certainly not nearly related, 

 we find a tongue of a perfectly unique shape in that it is long, 

 trough-like, and provided along its upper edges — which are turned 

 inwards — with well-defined serrations. So far, however, there 

 are no recorded observations to show how this peculiar tongue 

 is used. Similarly, the Anserine birds and the aberrant Stork 

 {Phcenicopterus), have developed tongues of a very remarkable 

 character obviously in response to their peculiar feeding habits. 

 Presenting numerous minor variations of shape among different 

 genera of Ducks and Geese, it is in nearly all extremely thick and 

 fleshy, fringed along the sides with fine lamellae or horny teeth, 

 as the case may be ; the lamellae occur in Surface-feeding Ducks, 

 the horny teeth in the Geese and Swans which feed on weeds. 

 In the fish-eating Ducks, as the red-breasted Mergansers, the 

 tongue is less fleshy, provided with fine bristle-like lamellae 

 along each side, and with horny conical papillae over the dorsal 

 surface, and these serve to hold the slippery prey ; but the tip 

 of the tongue in all these Anserine birds is horny and scoop- 

 shaped. 



The tongue is rarely protrusible in birds, and only in those 

 which, like certain mammals, use this organ instead of the jaws 

 for the capture of prey. Coated with a sticky saliva secreted 

 by an enormous pair of glands situated on each side of the 

 head, this organ is thrust out into the midst of colonies of ants 

 and withdrawn covered with victims. By this means the bird 

 is enabled to secure the largest possible amount of food with 

 the least possible labour. With an ordinary insect diet when 

 the prey is secured one at a time, such an arrangement would 



