ADAPTATION FOR THE INDIVIDUAL 9 1 



study of adaptation, the more likely we are to find 

 changes which have but little bearing on the safety of 

 the individual. They work for the good of the entire 

 species, sometimes to the distinct disadvantage of the 

 individual. The King Salmon may make its long run 

 to the headwaters of our western rivers, deposit its 

 eggs, have them fertilized, and then float down to 

 death. But it does not die before abundant prepara- 

 tion has been made for the continuance of the race. 

 Such adaptation for the good of the species will be 

 considered in the next chapter. 



The first and most important struggle any animal 

 has to enter is the never-ending battle for its food. 

 Occasionally there is a similar straining after the air 

 it breathes. But ordinarily air is sufficiently abundant, 

 except to animals living in the water, where the sup- 

 ply is always more or less restricted and easily be- 

 comes exhausted. But food is the constant need of 

 every organism, and most creatures die for lack of it. 

 In this struggle the animal is pitted against those of 

 his own kind, rather than against those of other spe- 

 cies. Even his brother is his enemy, for he desires 

 the same food. In many a nest of birdlings one of 

 them fails to reach its development simply because the 

 parent either is unable to find or it cannot carry 

 enough food to satisfy all the hungry mouths in the 

 same nest. Before the nestlings are ready to take 



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