SPECIFIC CHARACTERS. 221 



much importance as to cause its possessor to live 

 under circumstances when other individuals die ; or 

 to flourish better and so leave more offspring. This 

 fact is too frequently overlooked. When the fact of 

 the great struggle for existence is recognized, it be- 

 comes plain that those animals best fitted to the 

 struggle will have the best chance of surviving and 

 of producing their kind. It soon becomes imagined 

 from this that the very slightest usefulness in an 

 organ is enough to bring it under the powerful influ- 

 ence of natural selection. But this can hardly be 

 true; for natural selection acts by life and death, 

 and a variation must be of some considerable im- 

 portance to cause the survival of its possessors and 

 the destruction of individuals not possessing it. It 

 is beyond credulity to believe that the microscopic 

 sculpturings on the hair of the rabbit are of enough 

 importance to cause their perpetuation by selection. 

 There can be no doubt, therefore, that many charac- 

 teristics are of so little use that natural selection 

 can have had no influence in causing their develop- 

 ment. It is difficult enough to believe that the com- 

 plicated functional organs of the body have been de- 

 veloped through countless stages, each of which is of 

 sufficient use to its possessor to cause its exclusive 

 preservation ; and much less is it possible to con- 

 ceive that the various characteristics of the morpho- 

 logical species were developed in this way. 



The only other suggestion for meeting these cases 

 is by what is called correlated variation. The organ- 

 ism is bound together in such a way that when one 

 part varies other parts have also a tendency to 



