120 MAINE AGRICULTURAL EXPERIMENT STATION. I914. 



increase with tlie age of the bird but the fluctuations are much 

 greater than in the case of yolk weight. Since the weight of 

 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- 

 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 wnnter. 



