BREEDING POULTRY FOR EGG PRODUCTION. 169 



Effect of Selection of Good and Poor Winter Layers in the Same 



Line, D56D407 

 Generation Fi F2 F3 



Mean winter record of good layers and their progeny 76.0 46.7 35.57 

 Mean winter record of poor layers and their progeny 26.0 52.0 36.75* 



It is evident that selection within the line here was quite 

 without effect. 



Another example of the same thing from line D31D447 may 

 be given by way of further illustration. In this line there was 

 in the Fi generation a family of ten daughters. Of these some 

 were very good and some were poor layers. All were bred. 

 The mean results are shown in the next table. 



Effect of Selection of Good and Poor Winter Layers in the Same 



Line, D31D447 

 Generation Fi F2 F3 



Mean winter record of good layers and their progeny 62.5 23.75 22.00 

 Mean winter record of poor layers and their progeny 32.0 28.75 1475 

 Here again it is plain that selection within the line was with- 

 out effect. Many more examples of the same sort might be 

 given from the records did space permit. In general there is 

 no evidence whatever that the selection of individuals of differ-- 

 ent laying records, but belonging to the same fecundity geno- 

 type, produces any definite or permanent eff'ect whatever. 



DISCUSSION AND CONCLUSIONS. 



Taking into consideration all the facts which have come out 

 of this study, one is led to the following view as to the compo- 

 sition of a flock of fowls in respect to fecundity. Iri the aver- 

 age flock we may presume that there will probably be repre- 

 sented a number of fecundity genotypes, some high, some low, 

 and some intermediate or mediocre. In an ordinary flock these 

 genotypes will be greatly mixed and intermingled. Further, 

 the facts in hand indicate that the range of variation in fecun- 

 dity within the genotype is relatively very large, nearly as great, 

 in fact, as in the general population. Thus while fecundity 

 genotype means may be and usually are perfectly distinct, there 



* If one family of four birds, which ought not in fairness to be 

 included here because they were extremely inbred (brother-sister mat- 

 ing) in connection with another experiment, is excluded this average be- 

 comes 49.0. 



