46 THE THEORIES OF EVOLUTION 



the others and enable it to survive when others 

 perish. \ 



This is what Spencer describes as "the survival of 

 the^flttest." Darwin calls this phenomenon "natural 

 selection." Nature selects among the various indi- 

 viduals, "as breeders do among domestic animaTs~or 

 agriculturists among cultivated plants, certain speci- 

 mens presenting in the highest degree the characters 

 deemed worth preserving. Such individuals are 

 / mated and made to breed to the exclusion of others 

 and the character desired becomes more and more ac- 

 [ centuated and finally constant and hereditary. A 

 V new race or a new species has been created. 



Darwin observed very carefully the transforma- 

 tions undergone by the various domestic races under 

 the influence of artificial selection. His attention 

 was drawn to a group of animals lending themselves- 

 peculiarly well to that kind of observation— domestic 

 pigeons. 



Pigeon breeding is a very old science which was 

 already practised in ancient Egypt; it was also very 

 common in the Roman Empire and the pedigrees of 

 certain breeds were accurately established. At the 

 courts of some Asiatic rulers, pigeons were raised by 

 the thousands. Thus, in the course of many cen- 

 turies and through different processes, races and va- 

 rieties were created which present a differentiation 

 more deeply marked than that existing between cer- 



