110 POULTRY BREEDING AND MANAGEMENT 



not mean that all individuals of the flock are bred up to 

 the same level of production. It is not a leveling process. 

 The gulf between the high and the low individuals is not 

 bridged by selective breeding. The experiments indicate 

 that breed improvement, so far as egg production is con- 

 cerned, means the raising of the standard of production of 

 the individual. In other words, variability does not de- 

 crease with improvement in production. There are fewer 

 poor layers as a result of selection and more good ones, but 

 the range between the high and the low remains practically 

 the same. In the case of the Barred Plymouth Rocks the 

 mean of production moved up from between 61 and 80 in 

 the first year to between 161 and 180 in the sixth year. 

 In the case of the Leghorns and crosses, practically the same 

 law is shown. 



Breed improvement, therefore, depends upon raising the 

 mean or average production at the same time as the maxi- 

 mum production is raised. This is what happened in the 

 Oregon experiments. The maximum individual production 

 was raised each year while the average of the flock was also 

 raised. As the average production of the flock is raised, 

 the probabilities are that individual high records will in- 

 crease in like manner. The true breeder, therefore, will 

 ignore a fixed standard of production and breed for a pro- 

 gressive increase, and no one can yet say what the maximum 

 production of the hen is. (See page 111.) 



Hen's Potential Capacity. That the conditions under 

 which a hen lives affect her egg yield and determine, in a 

 measure at least, her degree of fecundity, is a truth dis- 

 cussed elsewhere. This is supported by investigations 

 made by Pearl as to the number of oocytes (eggs) in the 

 hen's ovary. It is apparently not from lack of eggs or 

 oocytes in the hen that the egg yield is low, for the count 



