354 THE STRUGGLE FOR EXISTENCE 



and meet with less unfavorable surroundings. Thousands of 

 the cotl's eggs never hatch and thousands of the young cod 

 die from disease, while others are killed; so that but a few 

 hnally Ijeconie full grown. Tlie question naturally arises, 

 how tlo any reach matvu-ity and live? 



After long years of [latient observation, a law kno^^^l as 

 the "sur-vival of the fittest" has been enunciated and ap- 

 parently esta]>lishcd. The tadpole and the young codfish 

 that could swim tlie fastest and had the strongest jaws were 

 best able to ])rocure food and most likely to survive. All 

 animals that are best fitted to meet their surroundings are 

 the ones that are most apt to live. In other wortls, these 

 are the jitteM riniDuils, and it is these that reach maturity. 



Adaptations to surroundings. — AVherever we may go to 

 ol:)serve animals, we shall find that the surviving ones are 

 those best adaptetl to their surroundings. For example, a 

 tiger with its short hair could not withstand the climate of 

 the polar regions so well as the polar jjear with its long, 

 shaggy coat. The common toad could not exist on the 

 deserts of the great Soutliwest, but the horned toad antl the 

 Gila monster [jrefer these regions liecause the}' are adapted 

 to them. 



Moreover, animals are being constantly modified and 

 molded to suit their changing environments. We do not 

 often recognize these changes because they are slight and 

 very gradual; nevertlK>less, they amount to a great deal in 

 a long series of years. For examjile, many insects liave 

 be(^n known to change from one kind of food jtlant to an- 

 other after the foiiuer liad been destroyeil. The same 

 sjjecies of insects and reptiles often dilTer greatly in color 

 when living u|)on different colored ]ilants or upon earth of 

 dilTerent shades, pi'ol)ably to gain i)ro(ection from their 



