120 MAINE AGRICULTURAL EXPERIMENT STATION. I 914 . 
increase with the age of the bird but the fluctuations a**e much 
greater than in the case of yolk weight. Since the weight 0£ 
each of the parts increases with the age of the bird the weight of 
the egg must show this relation also. In the case of the yolk 
weight we have seen that the rate of increase is quite precisely 
logarithmic. The fluctuations from this type are small. Albu- 
men weight shows a tendency to this type of increase but cer- 
A 
tain fluctuations are very great. The increase in shell weight 
is not logarithmic. The weight of the whole egg shows an 
increase in weight distinctly logarithmic although less precisely 
so than yolk weight. 
The different nature of the physiological processes involved 
in the formation of the parts of the egg affords ample basis 
for an independent variation. The weight of the yolk is deter- 
mined by the amount of yolk deposited while it is within the 
ovarian follicle. The albumen weight depends upon the amount 
of secretion of the albumen glands of the entire oviduct, while 
the weight of shell depends only upon the secretions of the 
shell forming glands of the uterus. It is conceivable that a 
disturbance of the processes involved in the formation of one 
part of the egg may have little or no effect on the processes 
involved in the formation of the other parts. The results given 
above indicate that the factors which determine the size of 
the yolk are less disturbed by temporary conditions than are 
those which determine the amount of albumen and shell secre- 
tion. 
2. VARIATION RELATED TO THE SEASON OE THE YEAR. 
Yolk weight and albumen weight show in general similar sea- 
sonal variations. Both parts increase in weight from the begin- 
ning of the fall laying to the beginning of the breeding season 
in February or March. This increase is proportionately greater 
in albumen weight than in yolk weight. At the beginning of the 
breeding season the yolk weight increases while the albumen 
weight either remains constant or decreases. The yolk weight 
remains nearly constant during the breeding season and the 
following summer, but the albumen weight tends to fall off 
especially as the molt is approached. Thus the proportion of 
yolk in the eggs during the spring and summer is larger than 
during the fall and early winter. 
