SPECIAL REPORT FOR YEAR I912. 21 



and (b) a study of pedigree records of poultry at once dis- 

 covers pedigree lines (in some measure inbred of course) in 

 each of which a definite, particular degree of fecundity con- 

 stantly reappears generation after generation, the 'line' thus 

 'breeding true' in this particular. 



3. A careful experimental analysis of the inheritance of 

 fecundity in both pure bred and cross-bred fowls has demon- 

 strated the following unexpected and practically important 

 facts, viz. : 



High egg productiveness may be inherited by daughters from 

 their sire, independent of the dam. This is proved by the 

 numerous cases presented in the detailed evidence where the 

 same proportion of daughters of high fecundity are produced 

 by the same sire, whether he is mated with dams of low or of 

 high fecundity. 



High productiveness is not inherited by daughters from their 

 dam. This is proved by a number of distinct and independent 

 lines of evidence, of which the most important are: (a) con- 

 tinued selection of highly fecund dams does not alter in any 

 way the mean egg production of the daughters; (b) the pro- 

 portion of highly fecund daughters is the same whether the 

 dam is of high or of low fecundity, provided both are mated 

 to the same male; (c) the daughters of a fecund dam may 

 show either high fecundity or low fecundity, depending upon 

 their sire; (d) the proportion of daughters of lozv fecundity 

 is the same whether the dam is of high or of low fecundity 

 provided both are mated to the same male. 



A low degree of fecundity may be inherited by the daughters 

 from either sire or dam or both. 



These results receive their best interpretation through the 

 application of Mendel's law of inheritance. A detailed dis- 

 cussion of the matter will be found in Bulletin 205. They 

 make possible a definite system of breeding for high produc- 

 tion, in which success is assured if the guiding principles are 

 carefully followed. The most notable practical feature of the 

 work is to demonstrate the very great importance of the male 

 bird in breeding for increased production. The goal of the 

 practical breeder must be to get a strain of birds in which the 

 males carry the hereditary factor for high productiveness in 

 pure form. 



