34 FECUNDITY IX THE DOMESTIC FOWL 



of birds laying 200 or more eggs in the year. This experiment was con- 

 tinued until the end of 1908. The selection, be it understood, was based on 

 the egg record alone, and no account was kept of pedigrees or of genotypes. 

 Every female with a record higher than 150 eggs in the year was used as a 

 breeder regardless of whether her high fecundity was genotypic or phseno- 

 typic. 



The results of this selection experiment covering a period of nine years 

 have been fully reported elsewhere. 7 Here it needs only to be said that the 

 net outcome of the experiment was to show that there was no steady or 

 fixed improvement in average flock production after the long period of selec- 

 tion. There was no permanently cumulative effect of the eight (in the last 

 year) generations of selected ancestry. So far from there having been an 

 increase there was actually a decline in mean egg production concurrent 

 with the selection, taking the period as a whole. During parts of the selec- 

 tion period, however, as for example the years 1899-1900 to 1901-02, inclu- 

 sive, and the years 1902-03 to 1905-06, inclusive, an improvement from 

 year to year was to be noted, but in each case the flock dropped back in 

 intervening years. This is an important point, the meaning of which is 

 now clear. The flock average from year to year depended largely upon 

 whether the breeders oj the year before had had their high fecundity genetically 

 represented or only somatically. In some years the selection was fortunate 

 in getting nearly all the breeders from good (i. e., "high production") 

 genotypes or from good combinations of genes. In other years just the 

 opposite thing happened: the high layers chosen as breeders came from 

 low genotypes or combinations of genes. The general upshot was that 

 while the selection of high layers merely as such was systematic year after 

 year the result attained in the general flock production was entirely 

 haphazard and uncertain. This is exactly what would be expected on 

 the genotype hypothesis, but not on the "statistico-ancestral." 



TABLE I 

 MEAN WINTER (NOVEMBER i TO MARCH i) EGG PRODUCTION DURING THE SELECTION 



EXPERIMENT 



Year Mean Winter 



Production 



1899-1900 41.03 



1900-01 37-88 



1901-02 45.23 



1902-03 26.01 



1903-04 26.55 



1904-05 35-04 



1905-06 40.66 



1906-07 21.44 



1907-08 15.92 



7 U. S. Dept. Agr. Bur. Anim. Ind., Bui. 1 10, Parts I and II, 1909 and 1911. Zeitschr. 

 f. indukt. Abst. u. Vererb.-Lehre, Bd. 2, 1909, pp. 257-275. 



