No. 534] FECUNDITY IN THE DOMESTIC FOWL 339 



The results indicate the effectiveness of this method 

 of selection. It should be understood, of course, that 

 only those pedigree lines are included in the high line 

 averages which uniformly in each generation show high 

 fecundity. A similar consideration applies to the low 

 line averages. 



Let us now consider briefly the question of the effec- 

 tiveness of selection within the genotype. According to 

 the "pure line" concept we should not expect selection 

 of high or low individuals belonging to the same geno- 

 type to produce any effect, except in cases where segre- 

 gation has occurred and the selected individuals are 

 really gametically different, though having the same 

 pedigree. An example of this sort has been given in the 

 case of line D61D168 (cf. p. 331, supra). The ineffective- 

 ness of selection within the line when something of this 

 sort does not occur is illustrated by line D56D407. In 

 the F, generation in this line there were four birds, of 

 which three were good layers and one was a poor layer. 

 Two of the good layers and the poor layer were bred. 



