76 



THE AMERICAN NATURALIST 



[Vol. LII 



amount of homogeneity in the flocks in respect to rate of 

 production as described below. 



Graphs showing the age at first egg for the flocks of 

 1913-14 and 1915^16 are shown in Figs. 1 and 2. The 

 former (Fig. 2) is unimodal and has a narrow base, the 

 shape of the curve indicating a high degree of homo- 



geneity in the flock. As might be expected from the na- 

 ture of the data (which is affected by the environment in 

 only one direction, i. e., toward a retardation of the age 

 at first egg) the lower part of the right-hand side slopes 



