86 BIOMETRY 
Having selected a particular character for investiga- 
tion, we must make a quantitative estimate of its 
development in each member of a fair sample of 
individuals which show the character in question. 
What is to be understood as a fair sample was well 
expressed by Quetelet when he wrote that statistics 
must be collected without any preconceived ideas, 
and without neglecting any numbers. We shall find 
that in this point the biometrical method differs 
from the method introduced by Mendel, since in the 
latter careful discrimination of data is an essential 
feature. 
The quantitative determination of a character may 
be made either by counting or by measurement. 
That is to say, we must proceed by measurement if 
the character we are dealing with is one of size or weight, 
and by counting if the character shows a series of 
numerical values of its own—e.g., if it is such a 
character as the number of veins in a leaf or the 
number of stigmatic bands on a poppy capsule. 
Before we make any determinations we ought to be 
quite certain that we are dealing with the same 
character in each individual, and that the individuals 
themselves are truly comparable with one another. 
Thus we might make a series of measurements of a 
particular bone in a particular limb of a particular 
race of human beings with some assurance that we 
should be dealing with homogeneous material. 
Our measurements or countings will fall either 
naturally or artificially into groups. In the case of 
countings the groups are naturally limited by the 
