CHAPTER III 



THE FACTORIAL THEORY OF HEREDITY AND 

 THE COMPOSITION OF THE GERM PLASM 



The discovery that ^Mendel made with edible 

 peas concerning heredity has been found to ap- 

 ply everywhere tliroiighout the plant and 

 animal kingdoms — to flowering plants, to in- 

 sects, snails, Crustacea, fislies, ampliibians, 

 birds, and mammals (including man). 



There must be something that these widely 

 separated groujDs of jjlants and animals liave 

 in common — some simple mechanism per- 

 haps — to give such definite and orderly series 

 of results. There is, in fact, a mechanism, 

 possessed alike by animals and plants, that ful- 

 fills every requirement of ]Menders principles. 



The Cellular Basis of Orgaxic Evolution 

 AND Heredity 



In order to appreciate the full force of the 

 evidence, let me first pass raj^idly in review a 



89 



