38 SOME Rl-t I'M MI -INTERPRETATIONS OF THE 



one correlation. Then we can also measure the correlation coeffin. m 

 t.itluT and son, as regards the quality in question. I Im- 

 is a second corn lation; and if we are told that the relative influence 

 of environment and heredity is measured by the ratio between these 

 two correlation coefficients, we certainly do thus get a clear conception 

 of what is meant 1 ." 



But has the writer really obtained a clear conception of what such 

 coefficients of correlation mean, when in the next paragraph he 

 continues : 



"Imagine an ideal republic, in some respects similar to that 

 designed by Plato, where not only were all the children removed 

 from their parents, but where they were all treated exactly alike. 

 In these circumstances none of the differences between the adults 

 could have anything to do with the differences of environments, and 

 all must be due to some differences in inherent factors. In fact the 

 environment correlation coefficient would be nil, whilst the hereditary 

 correlation coefficient might be high 2 ." 



Could any better evidence be adduced that the President of the 

 Eugenics Education Society did not know what a coefficient of 

 correlation meant at that date? The coefficient of correlation for the 

 environment might be anything from i to + i ; the only obvious 

 fact would be that you could not find its value, except in the form 

 o/o, from an environment, which entirely precluded any occurrence of 

 variation. How again Sir Francis would have smiled at the notion 

 that the coefficient of correlation for a constant environment must be 

 nil. Why should we follow such advice as that given by the President 

 of the Society to avoid as far as possible "such phrases as the relative 

 influence of heredity and environment," when on his own showing he 

 does not in the least appreciate the methods by which this relative 

 influence is measured? 



Then Major Darwin continues: 



"Surely what we want to know is how we can do most good 

 whether by attending to reforms intended to affect human surroundings, 

 or to reforms intended to influence mankind through the agency of 

 heredity. But does this ratio [that of the environmental and hereditary 

 correlation] give us any sure indication of the relative amount of 

 attention which should be paid to these two methods of procedure ? " 



1 This seems to contradict the writer's previous assertion that two things are 

 incomparable, if they have not a "common unit"' 



1 I wrote at once to Major Darwin pointing out the error of such a statement and 

 he withdrew it in the next number of his journal. But the harm done by an article 

 of this kind cannot be reversed by correcting a single misstatement out of many. 



