114 MASS. EXPERIMENT STATION BULLETIN 211. 



Changes in Age at which First Egg is laid. 

 Early in the history of these experiments it became evident that, on 

 the average, those birds that laid the largest number of eggs before March 

 1 were those that began laying first. As the average age at which the first 

 egg was laid was eight months, it was evident that either the pullets must 

 be hatched early to get them mature early in the fall, or else they must 

 grow and develop faster. Early maturity, therefore, was made the chief 

 aim ofthe breeding program, with the results shown in Table II and Fig. 9. 

 Changes in mean date of first egg, Fig. 5, vary directly with changes in 

 mean age at first egg. Integral curves are given in Fig. 14, frequency poly- 

 gons in Fig. 15 (page 119), and their constants in Table III. Note that 



100 =»=5^v^ — ^^-»^...r-~-*X_ 1912-13 



^-\^ I9I3-U 



'•x^'^^ I9I4-15 



80 "-.^X \ W \ 1915-16 



O 



60 



\\ \ •• \ \. \ ,., 1917-18 



Y.'>\\ \ \ I9I8-'I9 



V-- ^^ \ \ \ \ 



V . 



E GGS 



Fia. 10. — Integral Curves showing the Percentage of Each Flock having an Annual 

 Production as Great as that indicated, or Greater. 



One zero in 1917-18 is not shown. In 1912-13 no allowance is made for November pro- 

 duction as in Table II. The curve for 1913-14 is that of the 59 birds kept through 

 the year. (See Table II.) 



apparently something more than a sifting out of an early maturing strain 

 has occurred, as indicated by the mean and range for 1918-19, Fig. 15. 



Earlier maturity uncovered, or at least was associated with, more evi- 

 dence of the winter pause than appeared earlier, so that the gain in pro- 

 duction was not as great as was anticipated. As indicated below, progress 

 is being made in reducing the length of the pause, so that, eventually, 

 continuous production throughout the winter is expected. 



Since 1917 no attempt has been made to lower the age at first egg. 

 The basis of selection has been the same in each year since 1917. (See 



