520 



THE AMERICAN NATURALIST [Vol. XLYIII 



These percentages are quantities of a good deal of 

 interest. They measure the degree in which King Melia 

 Eioter 14th 's sire and dam were related to each other. 

 Community of ancestry is the basis of kinship. 



Percentages derived in the way shown above, from 

 cross pedigree elimination tables, I propose to call co- 

 efficients of relationship, and to designate by the letter 

 K, with appropriate sub-numbers referring to the genera- 

 tion. These relationship coefficients are, with some limita- 

 tions, independent of the inbreeding coefficients in the 

 values they may take, though 'the two will usually be cor- 

 related to some degree. It is, however, possible to have a 

 high value of Z with jff = 0. 



The most important feature of the relationship coeffi- 

 cients is found in their genetic implications. This can be 

 indicated best by an illustration. Let us consider the case 

 of the maximum possible degree of inbreeding with K = 0. 

 This will be found when the sire and the dam are each 

 inbred to the highest possible degree (continued brother 

 X sister mating) but are in no way related to each other. 

 Such a case would be afforded, for example, if a Jersey 

 bull, the product of continued brother X sister mating, 

 was bred to a Holstein cow, which was also the product 



