150 MAINE AGRICULTURAL EXPERIMENT STATION. I9II. 



types of the several lines, are however, quite different. We may 

 consider these genotypes to be given by the small letters, a, b, c, 

 ^> ^> f, 9- It is seen that three of the lines have genotypes cor- 

 responding closely to the general flock average 130. Two geno- 

 types are well above the general average of the flock, and two 

 others below. Now the basic idea of the pure-line concept as 

 here applied is that if, for example, two individuals of line A 

 are bred together, the average productivity of the offspring will 

 be approximately a (say 197 eggs) regardless of the tgg record 

 of the particular female bird bred. That is, it is to be expected 

 that the average productivity of the progeny of a female of 

 line A with an tgg record at x (say 80 eggs) and of a female 

 with a record at y (say 240 eggs) ivill he the same provided 

 both are mated to male birds from the same line as themselves, 

 that is, the A line. 



The same idea may be illustrated in another way. It is to 

 be expected that in such a population as that illustrated in the 

 diagram the average tgg production of the daughters of 200- 

 tgg hens will be as indicated in the following table: 



If a "200-egg" hen comes from — 



The probable 

 average pro- 

 duction of 

 her daughters 

 will be about — 



The A line, and is mated with an A line male .... 

 The B line, and is mated with a B line male .... 

 The C line, and is mated with an C line male. . . . 

 The D line, and is mated with a D line male .... 

 The E line, and is mated with a E line male. . . . 

 The F hne, and is mated with an F line male. . . . 

 The G line, and is mated with a G line male .... 



197 

 162 

 134 

 130 

 125 

 88 

 58 



Similarly we have according to the pure-line concept the fol- 

 lowing expectation regarding the progeny of poor producers : 



If a "75-egg" hen comes from — 



The probable 

 average pro- 

 duction of 

 her daughters 

 will be about — 



The A line, and is mated with an A line male . 

 The B line, and is mated with a B hne male. 

 The C line, and is mated with a C line male . 

 The D line, and is mated with a D hne male . 

 The E line, and is mated with an E line male . 

 The F line, and is mated with an F line male . 

 The G line, and is mated with a G line male . 





197 

 162 

 134 

 130 

 125 

 88 

 58 



