548 STRUCTURE AND LIFE HISTORIES 
method), or we may employ the experimental method. The 
method of biometry enables us to deal with a larger number 
of individuals, but the material studied is usually a mixed 
population, whose history is only imperfectly known, the 
conditions are more complex, and little if at all under 
control. By the experimental method it is not necessary 
to deal with such large numbers; we may choose carefully 
pedigreed material about the history of which we have 
more or less accurate knowledge, and we may greatly 
simplify and control the conditions under which we make 
our observations. The largest advance toward the solu- 
tion of the problems of inheritance has been made by the 
experimental method, in the form first employed success- 
fully by Gregor Mendel". This method will be briefly 
explained in the next chapter. 
