THE 



AMERICAN NATURALIST 



Vol. XLVIII September, 191U No. 573 



STUDIES ON INBREEDING. V 



Inbreeding and Relationship Coefficients 1 

 Dr. RAYMOND PEARL 

 University of Maine 



In the discussion of inbreeding coefficients contained in 

 a series of recent papers from this laboratory 2 no mention 

 has been made of an important consideration which arises 

 in connection with such coefficients. The further problem, 

 to which we may now turn, may be stated in the follow- 

 ing way. 



The pedigree of an individual consists of two halves. 

 One of these halves is made up of the sire and his an- 

 cestors ; the other of the dam and her ancestors. Follow- 

 ing the conception of inbreeding set forth in detail in the 

 earlier papers of this series it is plain that the values of 

 the coefficients of inbreeding for a particular pedigree are 

 composed of the following elements. 



1. The occurrence of the same individual animals more 

 than once on the sire's side of the pedigree only. 



2. The occurrence of the same individual animals more 

 than once on the dam's side of the pedigree only. 



1 Papers from the Biological Laboratory of the Maine Agricultural Ex- 

 periment Station, No. 69. 



2 Pearl, R., "Studies on Inbreeding. I. A Contribution Towards an 

 Analysis of the Problem of Inbreeding," Amek. Nat., Vol. XLVII, pp. 

 577-614, 1913; "The Measurement of the Intensity of Inbreeding," Me. 

 Agr. Expt. Sta. Bui, 215, pp. 123-138, 1913. Pearl, B., and Miner, J. B., 

 "Studies on Inbreeding. III. Tables for Calculating Coefficients of In- 

 breeding," Me. Agr. Expt. Sta. Ann. Bept. for 1913, pp. 191-202, 1913. 



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