LONG-LEGGED BIRDS. 383 



of wing has from above and from below, enable it to 

 act with equal force in its upward and its downward 

 stroke, and thus perform with more efficiency its fin- 

 like function. The birds of this group are slow and 

 unwieldy, with little capacity of motion either in the 

 air or upon land ; but their organisation is as admirably 

 fitted to their habit as that of any other birds ; and 

 they are curious, as forming the last link between the 



Patagonian Penguin. 



birds which, as a class, are more typically inhabitants 

 of the air, and those vertebrated animals which are 

 permanently dwellers in the waters, and cannot carry 

 on the process of respiration in the free air. 



STERNA OF LONG-LEGGED AND LONG-WINGED BIRDS. 



Among the long-legged or long-winged birds which 

 find their food near the waters, in fresh water or in the 

 sea, there is a resemblance in the sternum, but there is 

 also a gradation which may be traced, from the agami, 

 which may be considered as among the least aquatic of 

 the whole, to the cormorants and gannets, and perhaps 

 even to the gulls and terns. This sternal structure 

 does not of course, in birds of such varied forms and 

 habits, accord with the classification which is usually 

 made of them on the structure of their bills and feet ; 



