O w 



4-1 <V 



■"• c 



-a => 



^ > 



.iS O 



3 <U 



s i 



D-2 

 u 



Id 

 ^ u 



-5 bO 



'w <u 

 O j2 



<u 



•5 E 



^ O 



o Z 



D- 

 • -. oj 



c H 

 o . 

 'C -a 



H 



bo 

 C C 



s^ c n 



/^ « C 



^ C 



can effect an actual change in the gen- 

 otype under consideration. It is ob- 

 vious that this concept, which has 

 been completely acceptable up to this 

 time and which the biometricians 

 Weldon and Pearson have supported, 

 must hinder the acceptance of muta- 

 tions as something other than and as 

 important as fluctuating variation. 

 With all of the accumulated statistical 

 knowledge of heredity in populations 

 the acceptance of the mutation theory 

 was perhaps felt to be not necessary 

 for biology. I say "perhaps" here to 

 meet to a certain extent the objections 

 of biometricians. As for myself, the 

 magnificient experiments of Hugo de 

 Vries have proven the existence of 

 mutations beyond the shadow of a 

 doubt. 



It appears to be obvious from the 

 research results I have presented here 

 that the basis of the Galton-Pearson 

 Law, concerning the relationship be- 

 tween parents and offspring, is some- 

 thing other than that which has been 

 taken for granted up to now. The in- 

 dividual peculiarities of the parents, 

 grandparents, or any other ancestor, 

 has— insofar as my researches are con- 

 cerned—no influence on the average 

 characteristics of the offspring. It is 

 the g^-enotype of the line working in 

 intimate conjunction with the external 

 environment of a specific locality at a 

 particular time that determines the 

 average characteristics of an individ- 

 ual. The "line" is accordingly "com- 

 pletely constant and highly variable," 

 as de Vries has so clearly shown in a 

 similar situation, although apparently 

 in a paradoxical fashion. - 



At the same time, it must not be 

 implied that the pure line will be ab- 

 solutely constant. 



First there is the possibility that se- 

 lection of fluctuating variants through 

 very many generations can eventually 

 shift the genotype of a line. This has 



Die Mutationstheorie, vol. 1, p. 97. 



23 



