ARTIFICIAL AND NATURAL SELECTION 49. 



instance, the pedigrees of race-horses are kept with 

 most scrupulous care, and enormous prices are paid 

 for horses for breeding purposes. So it is with pigs, 

 poultry, dogs, and cattle, and in the improvements 

 effected in fruits and flowers. Not only are good 

 characters inherited, but bad ones also, and even 

 diseases and malformations, such as insanity, gout, 

 short-sight, cataract, and colour-blindness, among 

 men. 



F- The Influence of Environment. — We have 

 seen that the struggle for existence results in the 

 survival of the fittest. Now, if the conditions remain 

 permanent there is no reason to suppose that the 

 race would alter, for the fittest now would be so a 

 thousand years hence, provided the external con- 

 ditions did not change in the meantime. Variations 

 would no doubt occur, but as none of these would 

 confer an advantage, they would not be preserved. 

 In a very few cases this is so, but constant change is 

 the rule. For instance, consider the change effected 

 in Australia by the arrival of civilised man with his 

 dogs, horses, &c, resulting in the aboriginal inhabit- 

 ants, human and animal alike, being killed off by 

 competition. Man's influence is no doubt great ; but 

 other influences are still more potent. 



Here we derive much assistance from the evidence 

 afforded by geology, which tells us that, as regards 

 the earth we live in, things were not always as we 

 find and know them now. The marks on boulders 

 and deposits of glacial mud and clay, show that these 

 boulders have been brought from afar, that their 

 only possible means of transit was by glaciers, and 



D 



