Process of Evolution 221 



characters are produced. These recombinations occur in 

 the same general way in the lower and the higher organisms. 



This formation of new combinations of the primary hered- 

 itary substances is then the general feature of mating. It 

 is this of which we were in search when we asked: Is there 

 any general result of mating, comparable with the produc- 

 tion of energy as the general result of the taking of food? 

 Mating is a process of forming new combinations of the 

 primary hereditary materials. 



As a result of these new combinations, the organisms pro- 

 duced are very diverse in their hereditary characters. In 

 the infusorian some are weak and unenduring; the things 

 combined do not work to'gether harmoniously ; they die out. 

 Others are strong and vigorous ; they persist and multiply. 

 In other organisms similar differences appear, along with di- 

 versities in respect to all possible hereditary characteris- 

 tics. Thus mating steadily changes the face of organic na- 

 ture, continuously producing new combinations, some of 

 which are extinguished, while others flourish. 



This process is greatly assisted in the lower organisms by 

 the fact that after a set of new combinations is produced by 

 mating, each combination is multiplied greatly by vegeta- 

 tive reproduction, which does not make a change in the 

 grouping. Thus each combination is given an opportunity 

 to meet many diverse external conditions, with some of which 

 it may work in harmony; further, the number of possible 

 diverse combinations which may result from the next period 

 of mating is greatly increased. 



This continued formation of new combinations is the 

 great corrective of the uniformity which would result from 

 more rigid laws of heredity. In general, no one can predict 

 what combinations will actually result from a given mating, 

 for the number possible is much greater than the number 



