PROBLEM OF NURTURE AND NATURE 37 



It is hard to conceive a paragraph of the same length more full 

 of evidence of complete ignorance of the methods used in modern 

 science for comparing correlated variates! Yet it goes out as the 

 opinion of the President of a Society which is endeavouring to spread 

 the scientific doctrines of Eugenics among the people ! Major Darwin 

 begins by stating that it is needful to have a common unit of measure- 

 ment in order to compare two variates. To begin with we are not 

 comparing two things, but we are comparing the influence of two 

 things on a third, i.e. the intensity of a certain environmental influence 

 and the intensity of a certain somatic character in the parent, say, on 

 the intensity of the somatic character in the offspring. Yet Major 

 Darwin tells us we cannot do this because we cannot measure these 

 things in the same unit ! How suavely yet forcibly Sir Francis Galton 

 himself would have ridiculed such ignorance in high places as is passed 

 by the Editor of this Eugenics Journal ! We can see him now telling 

 us how the intensity of each character could be measured by its grade, 

 and how the problem turned on whether the same change in grade in 

 the environment and in the parental somatic character produced 

 greater or less change in the grade of the filial somatic character. 

 When we inquire whether inter-racially stature is more closely related 

 to cephalic index or to eye colour, are we to be met by the statement 

 that these characters cannot be compared because they cannot be 

 measured in a "common unit," and are we then to be told that it is not 

 "wise to use words in scientific literature without endeavouring to attach 

 a definite meaning to them?" Every trained statistician knows that 

 each character is measured in the unit of its own variability in what 

 he tenns its standard-deviation 1 , and that this standard- deviation 

 provides him with a measure of the frequency of each value of the 

 variate in question. It seems to me that the only correct sentence 

 in this paragraph, is the author's statement that he himself has no 

 idea what unit is "common" to heredity and environment. 



But our author continues: 



"Take any quality, and we find that the human beings composing 

 any community differ more or less considerably as regards that quality. 

 Now we can measure the correlation between the differences shown in 

 this quality and the differences of environment to which the members 

 of the community in question had previously been exposed 2 . This is 



1 Of course he may or does need other constants to help in the description of the 

 frequency. 



* loc. cit. p. 153. 



