312 THE A ME RICA X XA TEh\ 1 LIST [VOL. LII 



vigor were put into a laying house in October. The egg- 

 production curve is shown by the continuous line in Fig. 

 17. It bears a strong resemblance to that of the Maine 

 Station for 1912-13 and that of our flock for 1913-14. 

 There was in addition to the 39 pullets a smaller lot- 

 hatched April 27. The curve for both lots combined is 

 shown by the dotted line in Fig. 17. Again the curve is 

 essentially like the 1913-14 curve for Khode Island Eeds. 

 The writer would be glad to study the original stock in 

 more adequate fashion, but the amount of time, labor 

 and equipment required are so great that the end in view 

 did not seem to warrant the expense. 



Since Pearl has not discussed the question of age at 

 first egg from the present standpoint, the possibility must 

 not be overlooked that the factor of maturity may play an 

 important part in his results. In a recent paper (Pearl, 

 '16) he states that in a good laying strain the pullets 

 mature at five or six months on the average. Quite a dif- 

 ferent state of affairs exists in our Rhode Island Eeds, 

 where the average age is much higher, about 8^ months 

 for the entire flock. It is clear, however, from the discus- 

 sion that the factor of maturity does not influence his 

 results to any considerable extent. 



Since the two principal internal factors responsible in 

 most cases for the number of eggs produced by a pullet 

 during the winter are, first, the date of the first egg, and 

 second, rate, similar sets of data may result from vari- 

 ability in either of the two factors. Now the date of the 

 first egg is dependent in part on the time of year the bird 

 is hatched, and in part on differences in maturity. The 

 former factor is under control and can be used to elimi- 

 nate differences in maturity. Eate has already been dis- 

 cussed in another place, but it should be noted that it 

 may be modified by such definite factors as broodiness, 

 or the presence or absence of cycles, as well as other 

 physiological factors that appear to be innate but which 

 can not be named at present. The combined effect of 

 rate and date of first egg, or better the length of time 



