4 
Editorial 
without mathematical conceptions ; even so Faraday's mind worked in the case of 
electro-magnetism. But as eveiy idea of Faraday allows of mathematical defini- 
tion, and demands mathematical analysis in its modern statement, so every idea 
of Darwin — variation, natural selection, sexual selection, inheritance, prepotency, 
revei'sion — seems at once to fit itself to mathematical definition and to demand 
statistical analysis. Nor was the statistical conception itself entirely wanting in 
Darwin's work. The Ci'oss and Self-Fertilisation of Plants forms a splendid col- 
lection of statistical observations and experiments which offers many points of 
departure for further statistical research*. That Darwin's mind did not work 
easily in mathematical lines is, perhaps, best evidenced in the passage of a letter of 
1857 to Sir John Lubbock written when Darwin was dealing with the statistics of 
varieties in species as deduced from Floras : 
You have done me the greatest possible service in helping me to clarify my brains. If I am 
as muzzy on all subjects as I am on proportion and chance, — what a book I shall produce ! 
{Life, II. p. 104). 
But that he realised the importance of the statistical method for his investiga- 
tions is evidenced not only by this very passage, but by several others. Thus 
considering the variation of our common species he writes in 1846 : 
Andrew Smith once declared he would get some hundreds of sjjecimens of larks and sparrows 
from all pai-ts of Great Britain, and see whether, with finest measurements, he could detect any 
proportional variations in l)eaks or limbs, etc. This point intei'ests me from having lately been 
skimming over the absurdly opposite conclusions of Gloger and Brehm {Life, ii. p. 35). 
Andrew Smith indeed missed the opportunity of being a veritable biometric 
pioneer ! 
Elsewhere Darwin recognises the importance of determining the variability of 
skeletons by measuring limbs {Life, ll. p. 50). But, perhaps, the strongest 
evidence of his consciousness that biometry oflfers the only possible solution of 
problems of inlieritance occurs in the words : 
I write now to say that I have been looking at some of our mongrel chickens, and I should 
say one iveek old would do very well. The chief point which I am, and have been for years, very 
curious about, is to ascertain whether the young of our domestic breeds differ as much from each 
other as do their parents, and I have no faith in anything short of actual measurement and the 
Rule of Three {Life, ii. p. 51). 
These words prove fully Darwin's consciousness not only of the need of 
measurements, but also of arithmetical work upon such data in the case of 
heredity. They may well serve as a motto for Biometrika and for all biometri- 
cians : / liave no faith in anything short of actual measurement and the Rule of 
Three. 
It is not a mere formal clothing of biological conceptions with mathematical 
symbols that is here indicated, or that we are considering, when we say that all 
* See for example Mr G. U. Yule's use of Darwiu's data in his recent memoir "On the Association 
of Attributes in Statistics," Phil. Trans. Vol. 194, A., 258. 
