302 MAINE AGRICULTURAL EXPERIMENT STATION. I915. 



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Fig. I. Graph showing the course of mean winter egg production be- 

 tween the years 1899 and 1915. The solid lines and circles give the total 

 flock means. The two straight lines, fitted by the method of least 

 squares to the observed flock means, have the equations 3;=43.655 — 2.181X, 

 3;=i7,070-|-4.i48.r. The open circles and broken (dash) line give the 

 means of the lines selected for high winter production between the 

 years 1908 and 1915. The dotted line and open circles give the mean 

 winter production of the lines selected for low production between the 

 years 1908 and 1912. 



2. Frotn the beginning of the experiment through the laying 

 year 1907-08 the general trend of mean production was down- 

 ward, with minor fluctuations from year to year. In othv-r 

 words during the period in which the system of breeding was 

 mass selection for high production without progeny test there 

 was no change of the mean in the direction of the selectioi":. 

 The fluctuations in mean production during this period were, 

 in the main, due probably to two sets of causes: (a) environ- 

 mental differences in different years acting at one point or an- 

 other in the Hfe history of the birds; (b) random fluctuations 

 in the genetic constitution of the male birds used as breeders in 

 successive years, brought about because of the ignorance cf 

 the breeder, in the absence of any individual progeny testing 

 plan, of the ability of any particular male to transmit high fe- 

 cundity to his daughters. 



