284 NATURAL HISTORY. 



(4) Some of the variations which occur in the in- 

 dividuals composing any species, are favourable to the 

 species; some are unfavourable. That is to say, some 

 variations will either help the individual to obtain more 

 food, or to keep himself warm, or render him less 

 liable to fall a prey to his natural enemies, or will 

 otherwise help him in the struggle for existence. On 

 the other hand, some variations will keep the individual 

 back in the race for life, and will increase the difficulty 

 which all individuals have in maintaining their exist- 

 ence. It follows from this, that in any given species 

 of animals or plants those individuals which are born 

 into the world in the possession of any favourable 

 variations are, cceteris paribus, likely to be preserved; 

 while those having unfavourable variations are likely 

 to go to the wall and to be stamped out. 



This law is what Mr Herbert Spencer has called the law 

 of the ' Survival of the Fittest,' or what Mr Darwin has 

 called ' Natural Selection.' This last name is in allusion 

 to the fact that the action of 'Nature' that is, the 

 aggregate of natural forces is to insure the 'selection,' 

 out of the young of any species, of all those individuals 

 which are 'fittest' for their surroundings. These young 

 are preserved, while those not possessing any such 

 favourable variations, and therefore not so well fitted 

 for their surroundings, are weeded out and perish. The 

 operation of the law may be illustrated by the imaginary 

 example of the Giraffe, which Mr Darwin has himself 

 used as illustrating the action of natural selection, and 

 which was previously taken as illustrating Lamarck's view 

 as to the action of external conditions upon the structure 



