No. 614] 



EGG PRODUCTION 



67 



Barred Plymouth Rocks, while another is characteristic 

 of my Rhode Island Reds. 



The data in this paper are obtained from a flock of 

 220 March and April hatched pullets placed in the laying 

 houses in the fall of 1913, together with the data on winter 

 egg production from the flock (numbering 482 pullets) 

 placed in the laying houses in the fall of 1915, although 

 the composition of this flock was not the same as that of 

 1913-14, because it had been altered by the addition of 

 several other strains in order to overcome the unsatis- 

 factory vitality of the original flock. The addition of 

 new blood apparently increased the variability in some 

 respects as shown by the statistical constants (cf. Figs. 

 1 and 2, also 10 and 10a) . The winter production of the 

 flock of 1914-15 was decidedly poor and apparently not 

 normal, probably due largely to environmental condi- 

 tions, and hence data from this flock have not been used. 



It is impossible within the limits of this paper to pre- 

 sent detailed data on all points discussed. To the reader 

 who is unfamiliar with egg records, it may be said that 

 an inspection of the records reveals the essential nature 

 of the problems. 



The original flock came mainly from one of the leading 

 showroom strains of the country, to which were added a 

 few individuals from another showroom strain. Neither 

 strain, so far as known, had been especially bred for egg 

 production, nor had any of the strains added in 1915. 



Ways of Measuring Egg Production 

 It has been customary in times past to determine a 

 hen's egg production by her record expressed in the num- 

 ber of eggs per year, the year usually running from No- 

 vember 1 through the succeeding October 31. At other 

 times the first-year record of the hen has been taken as 

 the time unit, beginning with her first egg and running 

 365 days therefrom. More recently, the Maine Exper- 

 iment Station has used the period beginning with the first 

 egg of a pullet and extending to March 1 as the unit of 



