EUGENICS AND EDUCATION 135 



ment, belongs to the domain of modificability, the non-hereditary varia- 

 bility. 



It is clear that Johannsen by means of his investigations, has come to the 

 phaenotype and genotype notions. 



Johannsen confined his first investigation to the comparison of charac- 

 teristics of two generations. Afterwards, however, he continued the cul- 

 tivation of pure lines for many years, in order to see whether it was possible 

 to attain a selection of minus-, respectively plus-variants by means of con- 

 tinued cultivation. The result was negative. 



The question whether pure lines are invariable in the sense of once for all 

 unchangeable is something else. This does not need to be absolutely the 

 case: new hereditary variations can arise as mutations. This was also 

 observed by Johannsen on a single occasion. 



The work of Johannsen in connection with pure lines has, as already 

 mentioned, the same foundation as that of Mendel. While Mendel studied 

 heredity by crossing, Johannsen did so with pure lines. Both based their 

 investigations on the view of the independence of the hereditary charac- 

 teristics. 



Very important is the analysis of the curve of Quetelet, the experimental 

 proof that material, the variability of which can be expressed by the curve 

 of Quetelet, can be constructed from many hereditary variations, each with 

 its own variability. The unity of material, of which the variability can be 

 represented by the curve of Quetelet is seeming. 



The significance of this result, that there are hereditary variations, must 

 be instilled in the consciousness of every paedagogue. Here we see the value 

 of natural ability. Education learns this from eugenics: Much is innate; 

 the innate is largely bestowed by heredity. Education must develop 

 that which is inborn in man. Therefore, at the basis of the problem of 

 education lies the question of the possibility of education. 



Education is the result of natural ability and environment. The more 

 extensive the pedigree is known, the more clearly is the significance of 

 heredity. 



The fact of heredity might lead to fatalism: 



There is, however, also the possibility of modification. The same 

 phaenotype can have a different genotype as basis. We therefore need not 

 assume too quickly that the less gifted cannot, as a result of exertion and 

 guidance, attain the higher. 



On the basis of the knowledge of nature, we must guide the development 

 of every individual. 



This is of enormous value for the happiness of mankind. 



