SIZE, SHAPE AND PHYSICAL CONSTITUTION OF THE EGG. 113 
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 1. 
Showing the Mean of the Individual Coefficients of Variation 
for each Egg Character. 
Egg Character. 
Mean of the Individual Coefficients 
of Variation. 
Shell weight 
10.43 
Yolk weight 
9.84 
Albumen weight 
6.43 
Egg weight 
6.36 
Length 
3.32 
Breadth 
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 OF 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 
2 89026 
