90 NATURAL INHERITANCE. [chap. 



of Like Parents ; (6) those who are the progeny of 

 Unlike Parents. Next we write the statures of the 

 individuals in each Fraternity under the form of 

 M + (±D) (see page 51), where M is the mean stature 

 of the Fraternit3 7 , and D is the deviation of any one of 

 its members from M. Then we marshal all the values 

 of D that belong to the group a, into one Scheme of 

 deviations, and all those that belong to the group b 

 into another Scheme, and we find the Q of each. If it 

 should be the same, then there is no greater diversity 

 in the a Group than there is in the b Group, and such 

 proves to be the case. I applied the test (see Table 10) 

 to a total of 525 children, and found that they were no 

 more diverse in the one case than in the other. I 

 therefore conclude that we have only to look to the 

 Stature of the Mid-Parent, and need not care whether 

 the Parents are or are not unlike one another. 



The advantages of Stature as a subject from which the 

 simple laws of heredity may be studied, will now be 

 well appreciated. It is nearly constant in the same 

 adult, it is frequently measured and recorded ; its dis- 

 cussion need not be entangled with considerations of 

 mania o-e selection. It is sufficient to consider the Stature 

 of the Mid-Parent and not those of the two Parents 

 separately. Its variability is Normal, so that much use 

 may be made of the curious properties of the law of 

 Frequency of Error in cross-testing the several con- 

 clusions, and I may add that in all cases they have 

 borne the test successfully. 



