132 MODES OF RESEARCH IN GENETICS 



grow larger with each case of the mating of rela- 

 tives. Since the case is cited here merely for 

 illustration of method, four generations only are 

 considered. 



II. INBREEDING AND RELATIONSHIP COEFFI- 

 CIENTS 



In the discussion which has preceded no 

 mention has been made of an important con- 

 sideration which arises in connection with the 

 analysis of inbreeding by means of the coefficients 

 described. This further problem, to which we 

 may now turn, may be stated in the following 

 way: 



The pedigree of an individual consists of two 

 halves. One of these halves is made up of the 

 sire and his ancestors ; the other of the dam 

 and her ancestors. Following 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 ele- 

 ments : 



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. 



3. The reappearance of animals which appear 



