PROGRESS OF THE RACE 285 
tendency to degenerate can be combated and changed 
into an upward bias? In order to discover such a 
means it is needful to gather all possible information 
with regard to the primary factors of organic evolution 
in the human race—that is to say, variation and 
heredity. Galton was the first to show that the laws 
of variation and heredity in man are closely similar 
to the same laws in other organisms. He showed, too, 
that mental and moral characters are inherited just 
as strongly as physical characters—a fact which is 
by no means so generally appreciated as it should 
be, in spite of the further evidence adduced by Prof. 
Karl Pearson. 
Many people believe that the progress of the race 
can be directly and permanently affected by improve- 
ments in education and the amelioration of social 
conditions. It is certain that the qualities of any 
person— health, character, efficiency, and so forth, 
depend upon his environment and upbringing, as well 
as upon his hereditary endowments. It is therefore 
necessary, before we proceed farther, to arrive at some 
estimate of the relative importance of inherent qualities 
and of education—of nature and nurture respectively. 
Practically the only piece of good evidence upon this 
point is one which we owe to the researches of Galton. 
Galton’s data are derived from the history of twins. 
Now, human twins are of two kinds. One of these 
kinds corresponds to the young of those animals which 
normally bear two or more at a birth, each being 
derived from a separate ovum, whilst the second kind 
is the result of the development of two embryos from 
