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THE AMERICAN NATURALIST [Vol. XLYII 



with a view to an analysis of the effects of inbreeding, 

 though undertaken at greater or less length by a number 

 of men including Lehndorff, von Oettingen, Bruce Low, 

 Hocsch, Chapeaurouge, Bunsow, Stranz and others, has 

 not led to results characterized by the precision or the 

 definiteness or the quality of getting at fundamentals de- 

 manded in the present state of the science of genetics. 



The lack of precision and fundamental character in the 

 studies alluded to is not primarily to be attributed to any 

 inherent defect in the material. In the breeding of all of 

 the domestic animals inbreeding has been practised; in 

 many instances to a very marked degree. Further the 

 manner in which the inbreeding has been done (the types 

 of relationship-matings) exhibits a most intricate diver- 

 sity, from which different types may be picked out for 

 analysis in any reasonable quantity. The records are 

 accurate within their limitations, to a high degree. 

 Probably no experimentalist's records of descent are 

 more accurate, considering the relative numbers involved 

 in the two cases. 



The real need, I venture to think, has been for an ap- 

 propriate and valid method of pedigree analysis, which 

 possessed generality, and could on that account he de- 

 pended on to give com) (arable results when applied to 

 two (or more) different pedigrees. Specifically, there 

 seems not to have been worked out any adequate general 

 method of measuring quantitatively the degree of in- 

 breeding which is exhibited in a particular pedigree. 

 Without such a measure it is clearly impossible to pro- 

 ceed far in the analysis of the kinship aspect of in- 



particular case, and to show by illustrations the manner 

 in which these coefficients may be computed. I shall en- 

 deavor to show that the method is (a) unique, in the sense 

 that the values obtained in any particular instance can 

 only be affected by the degree or amount of inbreeding 



