BIOMETRICAL METHODS 79 



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 



