382 Evolution by Jumps 



Sixth, a mutation that affects the time of ripening or 

 maturing would have an immediate advantage in securing 

 an isolation from the parental form (that is, a physiological 

 isolation) . Under the theory of selection such a radical de- 

 parture from the parental character would be a disadvantage. 



Criticisms of de Vries 



Some of the new forms which jumped out of the seed- 

 beds were certainly distinct from any evening primroses 

 previously observed or described, either in Europe or in 

 America, the original home of the whole group. They were 

 distinct enough from other known forms to be considered 

 " good " species. They reproduced themselves constantly 

 and consistently. Other new forms, however, showed in 

 breeding experiments that they were not constant, or that 

 they were not capable of reproducing themselves. These 

 facts suggested the probability of a hybrid origin. Conse- 

 quently de Vries and his findings were exposed to the most 

 severe criticisms. 



The CEnothera lavtarckiana form, which de Vries took 

 to be the parent type, was not to be found in this country, 

 although related forms were present in abundance. On the 

 other hand, an American botanist, Bradley M. Davis, was 

 able to produce a lamarckiana synthetically! That is to 

 say, by crossing other species of the same genus, he obtained 

 forms like those that de Vries had used as the basis of his 

 experimental evolution. These results in America were taken 

 by many to indicate that the lamarckiana was really a hy- 

 brid, and could therefore yield the many other forms by 

 virtue of the segregation which we have seen to be char- 

 acteristic of the offspring of hybrids (see page 239) . Davis 

 actually obtained, by inbreeding his hybrids, a number of 

 new combinations of ancestral characters, plants resembling 

 some of the ** novelties " which de Vries had found in his 

 cultures. These findings threatened to discredit the muta- 

 tion theory which de Vries had so laboriously built up. 



