558 THE AMERICAN NATURALIST [Vol. LI 



tion on which the present method of measuring kinship is 

 based, the fact that A and B happen both to be inbred in 

 respect to X, does not make them any more closely related 

 to each other than if they were not so inbred. It may be 

 of interest in this connection to point out, not as adding 

 to the scientific exactitude of the position here taken, but 

 as indicating what the common sense of men who have 

 given thought to the subject of consanguinity has been, 

 that the position here adopted that in detenuining degree 

 of kinship a common ancestor counts but once as such, 

 appears to be exactly in agreement with the position of 

 both the canon law and the civil law on the same point. 



The second point in regard to which criticism might 

 seem to be possible is the method of referring the in- 

 breeding or relationship to the ancestral generations. In 

 all of these Studies the inbreeding or relationship is re- 

 ferred to the generation of the more remote (from the 

 propositus) of the two appearances in a pedigree of a 

 repeated ancestor. The logic of this procedure, rather 

 than the reverse, is found in the circumstance that the 

 fact of inbreeding (or kinship) does not establish itself 

 until the more remote reappearance is reached. Thus it is 

 impossible to know that a mating is of uncle and niece 

 until the grandparental generation is reached. 



a is the uncle of x, the common ancestors being b and c, 

 but this fact is not known until the second ancestral 

 generation is reached. The only logical method of rep- 

 resenting these facts exactly in a numerical way would 

 seem to be to say, in effect, that up to and including the 

 first ancestral generation of a and x there is no evidence 

 that these individuals are at all related, and therefore 



