l68 MAINE AGRICULTURAL EXPERIMENT STATION. I9II. 



except ill cases where segregation 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. 165, supra). The ineffectiveness 

 of selection within the line when something of this sort does 

 not occur is illustrated by line D56D407. In the Fi 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 



— f- — ;\- — -^i 



.A- ^ 



«-00 00-01 01-02 02-03 



03-04 04-05 05-06 06-07 07-08 08-09 

 i.AYINO YEAR 



Fig. 84. Showing the effect of selecting high and low fecundity on a 

 genotypic basis. The solid Une denotes means of all "high lines ;" the 

 dotted line means of all "low lines." Up to 1907-08 the attempt had been 

 to increase egg production by breeding merely from the highest layers, 

 regardless of pedigrees. In 1907 and subsequent years the attempt has 

 been to isolate genotypes of high and low fecundity which shall breed 

 true, each to its own type. 



the poor layer were bred. Large families were reared in F2 and 

 Fs. The average results in the three generations are given in 

 the following table. 



