870 EXPEBIMENT STATION RECOBD. [Vol. 37 



of the same flocks. These studies are based on six flocks of White Leghorn 

 hens ranging from nine to three years old and all descendants of a common 

 flock. 



The authors conclude that " environmental factors influence the records of 

 the pullet year more than that of later years and influence flocks making low 

 records more than those making high ones. Flocks of Leghorns with approxi- 

 mately the same yearly laying records will show the same distribution through- 

 out the season regardless of whether the records were made in the first, second, 

 or third year of production. Where a flock makes a low record the curve of 

 distribution will be lower throughout than that of a high-laying flock, and. 

 except for environmental fluctuations, the two curves will be practically parallel. 



" Where the high and low layers of the same flock are compared, the low 

 layers tend to fall off in production a little faster in the later part of the first 

 season so that the first-year curves gradually separate toward the end. This 

 was less noticeable in second-year production. High layers and low layers of 

 the first and second years showed almost perfect agreement in distribution, 

 with the curve of the low layers uniformly lower than that of the high layers 

 or the difference slightly widening toward the ends. The distribution of pro- 

 duction does not seem to be at all affected by age up to three years at least, 

 but total production affects distribution regardless of age. . . . 



" Winter egg production of flocks is more variable than annual production. 

 This variation seems to be closely correlated with environmental factors. 

 Flocks that made low winter records their first season made high ones the 

 second, and vice versa. The flocks that made low records the first winter 

 made higher three-year records than the high first-year flocks." The correla- 

 tion between the first-winter production and that of later years averagetl about 

 0.25. This correlation is le.ss for the high first-year flocks than for the low 

 ones. The higher the production of an individual the greater the percentage of 

 this production that will be made in the "winter" period regardless of age. 



The correlation between winter production (November 1 to February 28) 

 and total production of the same year, as shown by 18 flock records from 1907 

 to 1912. inclusive, average«l 0..5848. This correlation was found to doorcase 

 slightly with age. the averages for the six years being 0.632.^ between the first 

 winter and first year, 0.5862 between the second winter and second year, and 

 0.5351 between the third winter and third year. 



" The winter period as used does not seem correctly to represent a biolojjical 

 entity, but is made up of the end of one period and the beginning of another. 

 There does not appear to be any foundation for the assumption of a division of 

 the laying period into units. It appears that there is a fairly definite ' pro- 

 ductive rhythm ' that not only affects annual production, but even influences 

 the seasons so that a high fall production will be followed by a low spring one, 

 and vice versa. 



"The date of hatching when kept within a two-month period within the 

 months of March, April, and May did not appear to affect total production in 

 three years. The time between hatching and laying, while varying consider- 

 ably under different environmental conditions, affected the total production In 

 three years. The latest maturing pullets were always poorer producers." 



Egg-production data from other sources are tabulated and discussed, from 

 which it is noted that " the distribution of production of Iveghorns in other 

 flocks, including egg-laying contests, was found to agree with the corresponding 

 curves from the Utah flocks. The distribution of production in the general- 

 purpose breeds was found to be quite different from that of the Leghorns. 

 The curves of the general-purpose breeds reached their maximum early in the 

 aeason and then rapidly fell off again to very moderate production, from which 



