IMPROVING EGG PRODUCTION BY BREEDING. 221 



logical variable which it is desired to measure — namely the 

 maximum innate ability of the individual to produce eggs — 

 than the record over any longer period. 



The first of these points has never been in dispute. Regard- 

 ing the second there has been a good deal of doubt on the part 

 of some students of trap-nest records. They argue that be- 

 cause they find novi^ and then a case which seems to them an 

 exception to the general rule that the pullet winter production 

 is correlated with total production, that therefore winter pro- 

 duction is not a reliable measure of fecundity. It is pointed 

 out that a bird which produces no eggs, for example, in her 

 pullet winter period sometimes makes a very high two year or 

 three year record.^ This may certainly happen but it has no 

 particular bearing on the general point at issue. These seems 

 to be a misunderstanding or confusion of thought more or less 

 widely prevalent with reference to what it really is that one 

 wants to measure by means of trap-nest or milk scale, as a 

 guide to breeding orperations. I may perhaps make the point 

 here clearer by concrete illustration. Any poultryman knows 

 that by damp, dark, unventilated houses, unpalatable and im- 

 proper good, fed in insufficient amount he can prevent the 

 finest laying strain in the world from producing many eggs. 

 Yet clearly no one would accept a trap-nest record made under 

 such circumstances as measuring the bird's inherent capacity 

 as a layer. What it is really desired to know about, however, is 

 just this inherent capacity. One wants to be able to know, that, 

 for example hen A is a good layer, while hen B is a poor layer, 

 when both are under the absolutely most favorable circum- 

 stances for egg production in every particular, so that full 

 opportunity shall be given for every innate inherited potentiality 

 to come to actual, visible expression. But plainly the longer 

 the time unit chosen for the record, the more impossible it 

 becomes even measurably to approach the continued realization 

 of the "absolutely most favorable conditions" for egg produc- 



\ 



^But why . stop at two or even three years ? Every single one of the 

 arguments to the effect that a three year record is a "better" measure of a 

 hen's fecundity than her pullet winter record, can, with even greater force, 

 be used to defend the thesis that a twenty year record is a "better" meas- 

 ure than a three year one, hens having been known to produce eggs up to 

 that age. 



