4O Heredity and Eugenics 



descendants become so different from their progenitors 

 that man assigns them to distinct races. 



Now I am inclined to think that Darwin was on the 

 whole nearer the truth than the mutationists. They have 

 perceived a half-truth and perceived it more clearly than 

 did Darwin, but in scrutinizing this they have lost sight of 

 the larger picture which he saw. Darwin saw that new 

 races arise in two ways, and I shall attempt to show that 

 he was right. 



First let us discuss the Minerva-like method of evolu- 

 tion, the birth of new races in a day, a method of great 

 theoretical interest and practical importance. What is 

 known about this method of evolution is commonly called 

 Mendelism, after Gregor Mendel, an Austrian monk of the 

 last century. Mendel was a school teacher who studied 

 as well as taught, and fortunately for us he studied from 

 the book of nature more than from other books. He 

 thought clearly about the things he saw, but wrote little. 

 Indeed we wish that he had written more, but perhaps if 

 he had done so he would have thought less well. Like most 

 profound thinkers, he was in advance of his day, so that 

 when he spoke, the "wise men" of the time failed to under- 

 stand him. The "wise man" to whom Mendel hoped to 

 make his ideas plain was the great German botanist, Karl 

 Naegeli, to whom Mendel wrote a number of letters about 

 his studies of plant hybrids. Naegeli failed to grasp the 

 important point in Mendel's work, and the letters were for- 

 gotten until Mendel's fame had become world-wide. Then 

 they were hunted up and published. Naegeli 's failure 

 to understand Mendel is after all not surprising; Mendel's 

 thinking was in advance of his time. Several biological 

 principles now considered commonplaces were then un- 



