WINGS AND FEET 



sequence they have been able to retain large 

 wings for aerial flight. That they can develop 

 great speed under water and are very expert 

 fish-catchers is well known. 



The other line of evolution, the subaqueous 

 flight by anterior propulsion, or by the use of 

 the wings alone, reaches its height in the 

 penguins, and probably in the extinct great 

 auk, two birds widely separated genetically 

 but converging to the same result in this par- 

 ticular. Both birds in developing speed under 

 water by the use of the wings, reduced them 

 in size to the proportions of seal's flippers, 

 most markedly so in the case of the penguins, 

 thereby showing that large wings are not only 

 unnecessary, but even a hindrance in suba- 

 queous flight. In attaining this end they were 

 obliged to sacrifice aerial flight. This the 

 penguins were able to do owing to the absence 

 of land mammals in their antarctic breeding 

 grounds. The same conditions existed for the 

 greak auk at its chief breeding place in this 

 country on Funk Island, until the arrival of 

 that most destructive land mammal, the white 

 man. 



The diving petrel of the Straits of Magellan 



199 



