vii.] DISCUSSION OF THE DATA OF STATURE. 105 



parents, partly from his ancestry. In every population 

 that intermarries freely, when the genealogy of any man 

 is traced far backwards, his ancestry will be found to 

 consist of such varied elements that they are indistin- 

 guishable from a sample taken at haphazard from the 

 general Population. The Mid- Stature M of the remote 

 ancestry of such a man will become identical with P ; 

 in other words, it will be mediocre. To put the same 

 conclusion into another form, the most probable value 

 of the Deviation from P, of his Mid- Ancestors in any 

 remote generation, is zero. 



For the moment let us confine our attention to some 

 one generation in the remote ancestry on the one hand, 

 and to the Mid-Parent on the other, and ignore all 

 other generations. The combination of the zero Devia- 

 tion of the one with the observed Deviation of the other 

 is the combination of nothing with something. Its 

 effect resembles that of pouring a measure of water 

 into a vessel of wine. The wine is diluted to a con- 

 stant fraction of its alcoholic strength, whatever that 

 strength may have been. 



Similarly with regard to every other generation. 

 The Mid-Deviation in any near generation of the 

 ancestors will have a value intermediate between that 

 of the zero Deviation of the remote ancestry, and of the 

 observed Deviation of the Mid-Parent. Its combination 

 with the Mid-Parental Deviation will be as if a mixture 

 of wine and water in some definite proportion, and not 

 pure water, had been poured into the wine. The process 

 throughout is one of proportionate dilutions, and the 



