496 



Journal of Agricultural Research 



Vol. IV. No. 6 



Tabi,]^ XVII. — Sizes of litters in which offspring and sires and paternal grandsires are 

 born {from data excluded in making Tables XII and XIII) 



DATA ON ANIMALS WITH A "COMPLETE AMERICAN" PEDIGREE 



What we shall mean here by a "complete American" pedigree is a 

 case where the offspring have parents and grandparents American-bom, 

 so that we have records as to whether these ancestors were born in states 

 I, 2, or 3. Statements are frequently made about the effects of climate 

 on fertility ; therefore we have thought that it would be of some interest to 

 select from the total group of offspring that subgroup whose grandparents 

 as well as parents are American-bom. This requires that three generations 

 at least be American bom.' Further, the total subgroup of breeders who 

 import a great deal may form a class that differs significantly in the 

 handling of sheep from the totality of breeders who do not import. 



This restriction to cases of "complete American" pedigree has brought 

 our total number of cases down to only a little over one-third of the 

 number treated in Tables I to XIV, but it seems worth while to present 

 the tables showing corresponding frequencies of those with "complete 

 American" pedigrees and to make some comparisons. 



Any pedigree that has any grandparent not American-born is called 

 an "incomplete" pedigree. It is, of course, incomplete in that we have 

 no record as to whether a grandparent was born single, in twins, or in 

 triplets. 



TABLES FOR SIRES, DAMS, AND OFFSPRING WITH A 

 AMERICAN" PEDIGREE 



'COMPLETE 



Table XVIII (A) corresponds to Table 1(A). Here we find for the 

 correlation between the sum of numbers in litters in which sire and dam 

 are born and the number in corresponding litters in which offspring are 

 born, r = o.i29±o.oii. 



This coefficient is greater than that for the total population by 0.041, 

 and this difference is just about three times its probable error. Hence, it 

 is doubtful whether the difference is significant. 



' Wallace, A. R. Darwinism 



p. 154. London, iS 



