110 DARWINISM AND HUMAN LIFE 



other words, a new unit character of a beetle or 

 of a shepherd's purse two experimentally tested 

 instances does not blend when its possessor is 

 crossed with the original type. It is not swamped 

 by intercrossing, but reappears in its integrity in 

 a definite proportion of the succeeding generations. 

 Already in actual practice in wheat-growing it is 

 being found that selected single ears breed true, 

 and that no further selection is needed. 



The attractiveness of the mutation theory is so 

 great that we must be particularly cautious in our 

 acceptance of it. It would relieve the difficulties 

 that many naturalists have in believing that the 

 apparent big lifts and qualitative changes which 

 the history of organic life implies have arisen by 

 the natural selection of minute individual fluctua- 

 tions. It would make more intelligible the dis- 

 continuity of many species, if we found reason to 

 believe in their saltatory origin. It need hardly 

 be said that the origin of the mutation would 

 remain a mystery, for the mutation theory is not 

 a theory of mutations. It will be interesting if 

 evidence accumulate to show that the Proteus 

 leaps as well as creeps, if future generations look 

 back to Darwin as the naturalist who saw nature 

 moving by small steps, while Dr. Vries caught a 

 glimpse of her dancing ! 



ORIGIN OF VARIATIONS. In regard to the difficult 

 question of the origin of variations, we must not be 

 impatient to answer until our knowledge of their 

 nature has greatly increased. We must still confess, 

 with Darwin : " Our ignorance of the laws of varia- 

 tion is profound. Not in one case out of a hundred 

 can we pretend to assign any reason why this or 

 that part has varied." And again he said : 



