SELECTION. 193 



In the practice of poultry-breeding, several systems have 

 been proposed for judging an animal's value as a breeder by 

 mere inspection. Some of these systems are very elaborate. 

 For one of these systems it is claimed by the inventor, that by 

 adding and multiplying certain proportions of a male bird, it is 

 possible to find out how many eggs the animal would have laid 

 in a year if it had been a hen! 



The usual system of selection for egg-production in poultry is 

 based on the records of females exclusively. Hens are valued as 

 breeders according to the number of eggs they lay, and male 

 birds are selected with respect to the quality of their mother. 

 It is impossible for reasons of economy to keep the laying 

 hens separate, a system of trap-nesting is resorted to, to make it 

 possible to count the number of eggs laid by each hen. From 

 the records of the Maine experiment-station it can be seen, that 

 the number of eggs laid by an individual hen, is an unsatisfac- 

 tory guide to her qualities as a breeder. It is obvious, that a 

 system which would valuate the breeders according to the qual- 

 ity of their off-spring, would be vastly superior. 



As all the pullets of a certain season have to be hatched with- 

 in a short period, this means that the number of daughters 

 one can hope to raise from one hen in a season is very limited, 

 certainly below ten. A system of selecting poultry for egg-pro- 

 duction which would be based on a comparison of the quality 

 of groups of daughters of individual hens, would necessitate 

 keeping the records of a very great number of small groups sep- 

 arate, and would be as impossible as the usual system of trap- 

 nesting. On the other hand, a system based on a comparison of 

 the groups of daughters from individual fathers is wholly 

 practicable. 



All that is necessary according to this system, is to hatch the 

 eggs from each pen of one male and several females separately, 

 and to house the pullets from these eggs in separate pens. This 

 permits of counting the average number of eggs laid per hen in 

 the progenies of individual fathers, and thus to select the 

 group whose father had the most advantageous genotype. Sev- 



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