150 TROPICAL NATURE, AND OTHER ESSAYS. 



American and Asiatic species ; and it thus becomes a 

 valuable character indicating the radical distinctness of 

 the two groups, a distinctness confirmed by other 

 anatomical characters. 



On the other hand, peculiarities of organization which 

 seem specially adapted to certain modes of life, are 

 often diminished or altogether lost in a few species of 

 the group, showing their essential unimportance to the 

 type, as well as their small value for classification. 

 Thus, the woodpeckers are most strikingly characterised 

 by a very long and highly extensible tongue, with the 

 muscles attached to the tongue-bone prolonged backward 

 over the head so as to enable the tongue to be suddenly 

 darted out ; and also by the rigid and pointed tail which 

 is a great help in climbing up the vertical trunks of 

 trees. But in one group (the Picumni), the tail becomes 

 quite soft, while the tongue remains fully developed ; 

 and in another (Meiglyptes) the characteristic tail 

 remains, while the prolonged hyoid muscles have almost 

 entirely disappeared, and the tongue has consequently 

 lost its peculiar extensile power ; yet in both these cases 

 the form of the breast-bone and the character of the feet, 

 the skeleton, and the plumage, show that the birds are 

 really woodpeckers ; while even the habits and the food 

 are very little altered. In like manner the bill may 

 undergo great changes ; as from the short crow-like bill 

 of the true birds-of-paradise to the long slender bills of 

 Epimachinse, which latter were on that account long 

 classed apart in the tribe of Tenuirostres, or slender- 

 billed birds, but whose entire structure shows them to 

 be closely allied to the paradise -birds. So, the long 

 feathery tongue of the toucans differs from that of every 



