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THE AMERICAN NATURALIST [Vol. LII 



measurement, since March 1 serves as a convenient cal- 

 endar date, near the end of the winter cycle. Still more 

 recently the same workers have suggested that even a 

 shorter period would be desirable, because it is held that 

 a hen only reaches her highest possibilities under favor- 

 able conditions. Recently the Utah Station (Ball, Tur- 

 pin and Alder, '14) has suggested that for Leghorns the 

 records be kept for three years, since hens that lay poorly 

 the first year often lay much better during the second 

 or third. Eice, however, ('13) has published data on 

 this point, which show that such birds are the exception 

 rather than the rule. 



A year, however, may be considered to be a natural 

 unit. During this period the whole cycle of seasonal 

 changes is gone through with. Moreover, this period 

 bears a definite relation to the bird's life cycle, for its 

 beginning may be taken to correspond to the beginning 

 of egg production in the fall, while its close roughly corre- 

 sponds to the cessation of egg production the next fall, 

 usually coinciding with the onset of the fall moult, 

 though, of course, in some individuals, the biological year 

 exceeds 365 days. Thus, the year would seem to mark a 

 pretty definite period in the life of the bird as to her in- 

 nate capacity for egg production. In this paper we have 

 used both winter and annual periods as measures of pro- 

 duction, as the necessities of the moment required. 



There are some objections to each of the two common 

 methods of determining the point at which the year 

 begins. If the year begins with the first egg of each indi- 

 vidual, the differences in age at which the first egg is 

 produced are neglected. If a given point in the year is 

 chosen and the production of all individuals within a year 

 from this date recorded, differences in time of hatching 

 are neglected. Possibly a more satisfactory method 

 would be to take 365 days from the beginning of egg pro- 

 duction in each flock of equal age, or else from the aver- 

 age date at which production begins. 



The terms "high producer 1 ' and "low producer" are 



