INTRODUCTION 



The reason for this state of things is that there is 

 no food of any description to be had inland. Ages 

 back, a different state of things existed : tropical 

 forests abounded, and at one time, the seals ran 

 about on shore like dogs. As conditions changed, 

 these latter had to take to the sea for food, with the 

 result that their four legs, in course of time, gave 

 place to wide paddles or " flippers," as the penguins' 

 wings have done, so that at length they became 

 true inhabitants of the sea. 



Were the Sea-Leopards* (the Adelies' worst 

 enemy) to take to the land again, there would be a 

 speedy end to all the southern penguin rookeries. 

 As these, however, are inhabited only during four 

 and a half months of the year, the advantage to 

 the seals in growing legs again would not be great 

 enough to influence evolution in that direction. At 

 the same time, I wonder very much that the sea- 

 leopards, who can squirm along at a fair pace 

 on land, have not crawled up the few yards of ice- 

 foot intervening between the water and some of 

 the rookeries, as, even if they could not catch 

 the old birds, they would reap a rich harvest among 

 the chicks when these are hatched. Fortunately 

 however they never do this. 



* Sea-Leopard = Stenorhinchus leptonyx. 



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