384 



THE AMERICAN NATUBALIST 



[Vol. LIII 



it was decided to compute all increase or decrease in egg- 

 weight, for each individual, from the mean weight of the 

 first ten eggs laid at the beginning of the first laying year 

 of that particular bird. And, in order to translate the 

 differences into comparable terms, the increase or de- 

 crease was calculated as a percentage increase or as a 

 percentage decrease above or below the mean weight of 

 those first ten eggs. Consequently, the percentage of in- 

 crease or decrease in mean weight for all April eggs, 

 over or under the mean weight of the first ten eggs laid, 

 was ascertained in the case of each bird in the flock ; and 

 the same data were derived for the September produc- 

 tion. It is upon the analysis of these raw data"^ that the 

 appended computations rest. In the succeeding para- 

 graphs it is therefore the aim of the writer to demon- 

 strate the following point : that the higher percentages of 

 increase in mean egg-weight, reckoned at the periods of 

 the weight maxima, are so closely correlated with higher 

 production for the first laying year, that, by the method 

 to be presented, a flock of hens may be divided into 

 groups characterized respectively by higher, medium and 

 lower producing ability ; and that this method is effective, 

 whether the computations are based upon the vernal or 

 the autumnal weight maxima. 



IV 



We may first concern ourselves with computations 

 based upon the mean weight of the April eggs, including 

 the eggs of the entire month; and it is scarcely necessary 

 to resort to formal correlation tables to demonstrate the 

 point involved. The simpler methods may be employed: 

 (1) Dividinu- tlie bird^ on tlio basis of annual production 

 above or l)i'l()w llio flock -in(\'in and then computing the 

 percentage of iirt incivn^*' or decrease in mean egg- 

 weight; (2) dividinu ^'r.K into l;imii|k Imsed upon 

 percentages of ik i Mu .-ni (\<rg- 



scope. They will ^ i.iii ■ , invosti^ration 



which is still in progress. 



