132 MAINE AGRICUIvTURAL, KXPERTMENT STATION. TQIJ- 



descent the unit rather than the individual. This system is 

 used in the above pedigree as an illustration of method, al- 

 though only 4 ancestral generations are here considered. While 

 each individual animal which is eliminated because of previous 

 appearances in a lower ancestral generation is marked with an 

 X, those at the apex of a line of descent are marked with a 

 cross within a circle. These latter are all that need to be 

 counted directly. Their elimination automatically eliminates 

 their own ancestors. Thus the bull Sisera's Stoke Pcgis first 

 appears in the second ancestral generation as the sire of Davy 

 Stoke Pogis. He next appears (here marked with a cross 

 within a circled in the same generation as the sire of Peg 

 Weaver. He will, by the general rule for coefficients of in- 

 breeding, not be counted as a "different" ancestor the second 

 time in this generation. But this automatically eliminates his 

 two parents in the third ancestral generation, his four grand- 

 parents in the fourth generation, and so on until in the twelfth 

 generation 1024 ancestors of Sisera's Stoke Pogis will be so 

 eliminated. The same consideration applies in every other like 

 case. 



Practically then the method of dealing with a pedigree of 

 this sort is first to go through and indicate in a distinctive way 

 every primary^ reappearance of individuals. Then form a table 

 on the plan of Table 3, the character of which is so obvious as 

 not to need detailed explanation. 



This table is to be read in the following way : Because of 

 the reappearance of Sisera's Stoke Pogis in the 2nd ancestral 

 generation Bess Weaver has i fewer ancestors in that genera- 

 tion than she would have had in the entire absence of inbreed- 

 ing; 2 fewer in the 3rd generation and so on. The totals of the 

 columns of this table are the values, for each generation, of 



* By "primary" reappearance in the pedigree is meant a reappearance 

 as the sire or dam of an individual which has not itself appeared before 

 in the lower ancestral generations. Thus Patrick Fawkes makes a 

 primary reappearance in the fourth ancestral generation as the sire of 

 General Kelly, a bull which is not found in any generation below the 

 third. 



