PREFATORY XOTE 27 



two organisms, not even two germ cells, 

 are ever quite alike. 



Modern studies have given a new 

 meaning to the word ancestor, the bearer 

 of potentialities, and each new individual 

 is a complex of potentialities drawn 

 from different sources. Thus, by selection 

 and consolidation of successful variants, 

 accompanied by separation from the 

 mass, most of the species or kinds of 

 animals and plants we find in nature 

 have been produced. 



"Nature," says Burbank, "has time 

 without limit, but man has immediate 

 need for better and still better food, 

 houses and clothing, and our present 

 state of civilization depends largely upon 

 the improvements of plants and animals 

 which have consciously and half-con- 

 sciously been made by man, and future 

 civilization must more and more depend 

 upon scientific efforts to this end." 



