No. 562 ] 



THE PROBLEM OE INBREEDING 



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which lias been practised in the line of descent under con- 

 sideration and (b) general, in the sense that it is equally 

 applicable to all pedigrees and to all degrees and types of 

 inbreeding. 



Preliminary Definitions 



In attempting any general analysis of the problem of 

 inbreeding from the theoretical standpoint one is con- 

 fronted with the necessity for a definition of inbreeding, 

 which shall be at once precise and general, that is, such as 

 to include all of the many diverse ways in which this sort 

 of breeding may be practised. A great number of defini- 

 tions of the concept "inbreeding"' have been proposed in 

 the literature of genetics. I shall not attempt to review 

 these definitions here, since to do so would serve no use- 

 ful purpose in the present connection. A careful con- 

 sideration of them is bound, I think, to lead one to the 

 conclusion that they have been, in general, ha^ed on 

 grounds of practical expediency, rather than critical 

 biological analysis. 



Clearness and simplicity of thinking will be gained by 

 approaching the problem de novo. Leaving aside for the 



