SIZE, SHAPE AND PHYSICAL CONSTITUTION OF THE EGG. II 3 



random sample from other birds of the same strain, there is 

 nevertheless a high degree of variation among them. This 

 variation is appreciable in every egg character but the several 

 characters show it in decidedly different degrees. The means 

 of the individual coefficients of variation are given in Table i. 



TABLE I. 



Shozmng the Mean of the Indimdual Coefficients of Variation 



for each Egg Character. 



Mean of the Individual Coefficients 

 Egg Character. \ of Variation. 



Shell weight 



Yolk weight. . . . . 

 Albumen weight. 



Egg weight 



Length 



Breadth 



10.43 

 9.84 

 6.43 

 6,36 

 3.32 

 2.38 



The purpose of the present part of the paper is to investigate 

 further this variation among the eggs of the individual. 



The data collected in the present investigation offer material 

 for the study of the following phases of this variation in the 

 eggs of the individual. First the variation due to the age or 

 maturity of the bird, second that due to the seasonal distribu- 

 tion of the laying, third that due to the general physiological 

 conditions, i. e., health of the bird, fourth variation due to the 

 tendency of the birds to lay in litters and fifth that related to 

 the tendency to lay in smaller groups or clutches. 



I. THE VARIATION RELATED TO THE AGE AND MATURITY OE THE 



BIRD. 



The data used in this study are the measurements taken on 

 all the eggs laid by each of the twelve birds which lived and 

 continued to lay through two years. To illustrate certain points 

 it is possible to supplement this with the data on the eggs of 

 other birds which did not complete their second year. 



The progressive change in egg weight associated with the 

 maturity of the bird is shown by the monthly mean egg weight. 

 In the case of each individual the egg weight at the end of the 

 second year is decidedly greater than at the beginning of the 

 first year. From the beginning of laying until the beginning of 

 the first breeding season the eggs increase rapidly in size. From 

 this time on the weight of the egg is subject to quite perceptible 



