188 HEREDITARY CHARACTERS 



mutations. Mutations, according to de Vries himself, are 

 far more limited than would be gathered from the utter- 

 ances of his followers. His conception apparently is, that 

 mutations form that particular class of variations from 

 which new species or sub-species are suddenly produced. 

 On his hypothesis evolution has proceeded entirely through 

 the selection of this particular class of variation, and he 

 holds that characters due to mutations would blend when 

 crossed, and would not be transmitted in the Mendelian 

 manner. There seems to be no material evidence for this 

 theory. It would of course be possible to say that when 

 two characters blended they had arisen as mutations, and 

 that when they segregated they had arisen as fluctuating 

 variations. There is more reason to suppose that individual 

 variations give rise to individual characters, and that 

 these in turn give rise to racial characters. Individual 

 characters tend to segregate, racial characters tend to blend 

 when crossed. There is not the slightest necessity to assume 

 two kinds of variations, though they may be large or small. 

 Were any obvious difficulty overcome by such an assump- 

 tion, there might be some excuse for making it. No such 

 difficulty exists. 



The new characters in a large variation are of course 

 individual characters, just as much as they are in a small 

 variation, so it is to be expected that the aberrations would 

 behave in a Mendelian manner. It has been shown experi- 

 mentally that this happens. It must be remembered that 

 when an aberration is crossed with an individual possessing 

 the mean characters of the race, natural conditions are inter- 

 fered with, and artificial conditions are at once produced. As 

 has already been pointed out, large variations must under 

 natural conditions generally throw the individual out of 

 harmony with its environment, and therefore such an indi- 

 vidual would tend to be eliminated. Also, as the character 

 is apparently transmitted in an alternative manner, if off- 

 spring were produced those that inherited it in a pure 

 form would also be under a disadvantage and tend to be 



