106 POULTRY BREEDING AND MANAGEMENT 



necessary if the highest results are to be secured in pro- 

 duction. 



It should not be assumed from, this experiment that 

 crossing of different breeds is always necessary to secure 

 vigor. The same result may be secured by crossing different 

 strains of the same breed, in other words by outcrossing. 



Mode of inheritance. Granting that the fact of trans- 

 mission of high egg-laying has been demonstrated, there 

 remains the further question as to the mode of inheritance. 

 Does it come about all at' once according to the Mendelian 

 law of dominance and recessiveness, or is it an achievement 

 that comes bit by bit after years of patient selective breed- 

 ing? Is high egg production a sex-limited affair in its in- 

 heritance? Is it inherited from the dam and dam alone, 

 or does it come through the sire and sire alone ? 



So far as the Oregon investigations have gone, the results 

 do not bear a Mendelian interpretation. They do not show 

 that high egg production is either dominant or recessive to 

 low production. When high producers were mated to sons 

 of high producers the daughters were neither all high nor 

 all low producers. Mating high producers together, the 

 daughters did not equal the production of the parents on 

 the average. When low producers were mated the daugh- 

 ters did not take after either or both of the parents, but 

 showed a higher egg production than the dams or sires' 

 dams. In the one case there is a pulling down, in the other 

 a pulling up to a general level. Apparently the daughters 

 do not take the characteristics of the mother to the exclusion 

 of the sire's mother, or the reverse. 



It appears as though high egg production is the accumu- 

 lated result of the selection of high production breeding 

 stock carried on for many generations. The breeder, how- 

 ever, will make rapid progress in reaching the high standard 

 in proportion as he is successful in identifying the excep- 



