f,90 



THE AMERICAN NATURALIST [Vol. XLVII 



Zj = iM|.-_6) =81 . 25 , 



and so forth. 



The values of the successive coefficients for parent X 

 offspring breeding for 16 ancestral generations are given 

 in Table II. 



TABLE II 



Values of the Successive Cokffk ikxts of Inbreeding in the Case of 

 Continued Parent X Offspring Mating 



By comparison of this table with Table I it is evident 

 that while the increase in intensity of inbreeding is not 

 so rapid in the first few ancestral generations by this 

 parent X offspring type of breeding as with the brother 

 X sister type, by the time the tenth ancestral generation 

 is reached the values are for practical purposes the same. 



The curve of inbreeding for continued parent X off- 

 spring breeding is shown in Fig. 1. 



Illustration III. First-Cousin X First-Cousin Breeding 

 As a third illustration may be taken the case of con- 

 tinued cousin mating. Such breeding represents the next 

 step in decreasing intensity of inbreeding beyond the 

 parent X offspring type. 



In this pedigree it will be seen that in each mating the 

 sires of the individuals bred together are brothers. In 

 other words, each individual is mated with its first- 

 cousin. 



