no BIOMETRY 



ticular line, and not to the mean value of the general 

 population. 



The case is indeed precisely similar to the supposed 

 example of a mixture of races of peas, which was made 

 use of as an illustration at the beginning of the present 

 chapter. In other words, a pure line consists of a 

 group of individuals which has a normal variation of 

 its own, and the offspring of which by self-fertilization 

 breed true to the type of their own particular group, 

 and show no regression towards the type of the general 

 population to which the group belongs. 



If we were to carry on this conception to the case of 

 bisexual inheritance, we should find that the different 

 pure lines would become crossed and confused together 

 in a way which would be very difficult to disentangle. 

 There is no reason to doubt that statistical treatment 

 of such a population would yield similar results to 

 those actually obtained by biometricians from the 

 data at their disposal ; and we may notice that a for- 

 tuitous mixture of a considerable number of pure 

 lines, having slightly different types, would admirably 

 ulfil the conditions we have seen to be necessary in 

 the case of material, to which methods based upon 

 the theory of chance are to be applied. The phe- 

 nomena which follow upon the crossing together of 

 two or more pure lines still remain to be worked out, 

 but it is not unlikely that they will be found to con- 

 form to those laws of heredity associated with the 

 name of Mendel which are explained in Chapter VII. 

 If this should be found to be the case, it is not im- 

 possible that the theory of pure lines, in combination 



