THE GREATER PROBLEMS OF HEREDITY 217 



due directly to Natural Selection, and, if not, whether it is not 

 possible to formulate a rational theory to account for its occurrence, 

 whether under the conditions in which life exists variations can be 

 other than spontaneous, whether the power of growing under the 

 stimulus of use is not just as much an adaptation as the power of 

 repairing damaged parts under the stimulus of injury, whether the 

 effect of conjugation is to mix parental characters as marbles are 

 mixed or to blend them as colours are blended, and what in the 

 one case or the other is the function, the utility, of- the mixing, and 

 above all to ask themselves whether adaptation is due wholly to 

 the direct action of Natural Selection or in large part also to 

 retrogression occurring in the complete absence of selection. 



356. These are the greater problems of heredity. It is very 

 possible that the solutions I have ventured to suggest are 

 erroneous, but I am very sure that evidence exists which should 

 enable us, if only we think clearly, closely, and comprehensively 

 enough, to solve them, and that very much of this evidence may 

 be obtained from a study of human beings. To that study we 

 will now proceed. 



