16 Walter Frayik Raphael Weldon. 1860—1906. 
outline. Naturally he turned first to those methods of proof, morphological and 
embryological, which were being pursued by the biological leaders of the period, 
and it was only with time that he came to the conclusion that no great progress 
could be attained by the old methods. We have already seen that even before the 
appearance of Natural Inheritance, Weldon's thoughts were turning on the 
distribution of variations and the correlation of organic characters. He was being 
led in the direction of statistical inquiry. The full expression of his ideas is well 
given in the first part of the " Editorial " with which Biometrika* started : 
" The starting point of Darwin's theory of evolution is precisely the existence of those 
differences between individual members of a race or species which morphologists for the most 
part rightly neglect. The first condition necessary, in order that any process of Natural 
Selection may begin among a race, or species, is the existence of differences among its members ; 
and the first step in an enquiry into the possible effect of a selective process upon any character 
of a race must be an estimate of the frequency with which individuals, exhibiting any degree of 
abnormality with resjject to that character, occur. The unit, with which such an enquiry must 
deal, is not an individual but a race, or a statistically representative sample of a race ; and the 
result must take the form of a numerical statement, showing the relative frequency with which 
various kinds of individuals composing the race occur." 
It was Francis Galton's Natural Inheritance that first indicated to Weldon the 
manner in which the frequency of deviations from the type could be measured. A 
mere catalogue of exceptional deviations seemed to him of little value for the 
study of Natural Selection. But this description of frequency was only the first 
stage. How did selection leave the distribution ? and How was the intensity 
of selection to be measured ? naturally arose as the next problems. These 
problems led at once to the even greater question of the influence of selection on 
correlation. What is the relation between organs in the same individual, and how 
is this changed, if at all, by the differentiation of species, or at least by the 
establishment of local races ? Nor could the problem of evolution be complete 
without ascertaining the manner in which deviations were inherited. The modern 
biometric methods of discussing these problems, if very far from fully developed, 
were at least suggested in Galton's great work, and that book came as a revelation 
not only to Weldon, but to others who were preparing to work on similar lines f. 
In Plymouth, 1890, Weldon started his elaborate measurements on the 
Decapod Crustacea and soon succeeded in showing that the distribution of varia- 
tions was closely like that which Quetelet and Galton had found in the case of man. 
So far as the present author is aware, the paper "The Variations occurring in certain 
Decapod Crustacea I. Grangon vulgaris" (13) was the first to apply the methods 
of Galton to other zoological types than m&n\. In this paper Weldon shows that 
different measurements made on several local races of shrimps give frequency 
distributions closely following the normal or Gaussian law. In his next paper, 
* Vol. I. p. 1. 
t The present writer's first lecture on inheritance was given on March 11, 1889, and consisted of an 
exposition and amplification of Galton's theory. 
X Galton had dealt with the weights of sweet pea seeds, Merrifield with the sizes of moths, but they 
had not published fitted frequency distributions. 
