Nos. 618-619] EGG PRODUCTION 313 



elapsing between the first egg and March 1, is such that 

 the same number of eggs may result from a variation in 

 either one of these factors. If a flock of birds all begin 

 to lay about the same time of year, but vary greatly in the 

 rate at which they lay, a body of data superficially the 

 same as that produced by a flock of birds laying at a 

 fairly uniform rate but varying greatly in the time at 

 which they begin to lay might readily result, especially if 

 the variability of each set of factors (rate or maturity) 

 was very much alike. Radically different sets of data 

 would result only if the variability belonged to quite dif- 

 ferent types. The birds that make unusually high winter 

 records are those that start early and lay at a good rate 

 throughout the winter. A poor record, on the other hand, 

 results either from a low rate combined with a long period 

 of production (the date of first egg coming early in the 

 fall) or from high rate and a short period of production, 

 since the date of first egg comes late in the winter. 



A late date of beginning egg production may be the 

 result of late hatching or of delayed maturity. That is, 

 an early-maturing bird if hatched too late may lay no 

 more eggs than a late-maturing bird hatched early in the 

 spring. Thus, the actual record of a bird is the result of 

 the influence of several factors, themselves very variable, 

 and gives much the same result as though a much larger 

 number of factors were involved. 



Pearl has spoken of two production factors, L l and L 2 , 

 but has not, so far as I know, assigned either to the two 

 chief factors concerned in winter egg production, viz., 

 rate and age at first egg, nor does the context indicate any 

 such sense. At first sight it might seem possible that one 

 of these factors is a factor for early maturity, the other 

 for rate; for according to Pearl's theory both factors 

 must be present to secure high production, since the L x 

 factor in the homozygous condition does not make a high 

 producer. So far as can be seen, there is no objection 

 to assigning one of Pearl's two factors to rate. Some diffi- 

 culties are encountered, however, in assigning maturity 



