436 Journal of Agricultural Research voi. v.no. lo 



It will be noted that the Barred Plymouth Rock means are higher 

 throughout than are the total flock means. This merely signifies that 

 in the total flocks are included many crossbred birds carrying low fecun- 

 dity genes. 



Turning to the coeflicients of variation, which measure the relative 

 variabiUty, it is seen that in every case but one (total flock, 191 1) the 

 coefficient is lower for the March i than it is for the 300-day measure. 

 The diflterences are, in the single instances taken by themselves, usually 

 not statistically significant, having regard to the probable errors; but 

 the general trend is unmistakably in the direction of a lower relative 

 variability of the production to March i, indicating again that this is 

 a somewhat better measure of the winter cycle than the production to 

 300 days of age under the conditions prevailing in this work. 



SUMMARY 



In this paper quantitative evidence is presented which shows, with 

 flocks of poultry having average hatching dates falling somewhere within 

 the month of April, that — 



(i) The correlation between the egg production to March i of the 

 pullet year as one variable and the egg production up to the time when 

 the individual is 300 days of age as the second variable is extremely high. 



(2) The mean production to March i is, in general, higher than the 

 mean production to 300 days of age. 



(3) The production to March i is a relatively less variable measure 

 (as indicated by the coefficient of variation) than the production to 300 

 days of age. 



(4) The conclusion that the 300-day production would be a better 

 measure of the winter cycle of fecundity than the production to March 

 I is not warranted by the facts. Whatever superiority there is of one 

 of these measures over the other is entirely in favor of the production 

 to March i. We may therefore conclude that the use, in the writer's 

 investigations on fecundity, of the record of egg production to March i 

 ■of the pullet year as a measure of the winter cycle of production is fully 

 justified by a critical examination of the facts. The justification for the 

 employment of the winter cycle of production as an index of innate 

 fecundity capacity or ability is a distinct and separate problem which 

 has been discussed at length in earlier papers. 



LITERATURE CITED 

 (i) Brown, Wil. 



1914. Report of second twelve months poultry laying competition, 1913-1914, 

 at Harper Adams Agricultural College, Newport, Salop. In Field 

 Exp. Harper Adams Agr. Coll. Newport, Salop, Joint Rpt. 1914, p. 7- 

 81. 



