1 66 HEREDITY AND EVOLUTION IN PLANTS 



with, explains and illustrates all the facts connected with 

 the following branches of the subject: ist, the system of 

 natural affinities; 2d, the distribution of animals and 

 plants in space; $d, the same in time . . . 4th, the 

 phenomena of rudimentary organs." And Wallace goes 

 on to show, in detail the bearing of the law upon each of 

 the four points enumerated. 



FIG. 76. Alfred Russel Wallace (1823-1913). Co-discoverer, with 

 Darwin, of the principle of natural selection. Noted student of geo- 

 phical distribution. 



A quotation from Darwin is also pertinent here: "It 

 is ... obvious," said Darwin, "that the individuals of 

 the same species, though now inhabiting distant and 

 isolated regions, must have proceeded from one spot, where 

 their parents were first produced for, as has been explained, 

 it is incredible that individuals identically the same should 

 have been produced from parents specifically distinct." 



121. Mutation and Discontinuous Distribution. Read- 

 ing Darwin's statement in the light of the mutation theory 



