SIZE, SHAPE AND PHYSICAL CONSTITUTION OF THE EGG. 135 
fowl. The data on which it is based are the measurements of 
all of the eggs laid by twenty-two Barred Plymouth Rock birds. 
For thirteen of these birds records were taken on every egg 
laid up to the end of the second laying year. For the remainder 
records were taken covering the eggs of the first laying year. 
The thirteen birds which were alive at the beginning of their 
second adult molt were killed at that time. The more impor- 
tant results of the investigation may be summarized as fol- 
lows : 
i. The Individuality of the Eggs of the Same Bird. 
1. The individuality of a bird is expressed in each physical 
character of her eggs. 
2. This individuality is more pronounced in respect to the 
size than the shape of eggs and also in respect to the weight of 
albumen and shell than weight of yolk. 
3. There is a tendency for the several egg characters to be 
related to each other in such a way that when the eggs of an 
individual are large they are both long and broad and each of 
the parts is large; but the hens which lay large eggs lay eggs 
with a smaller proportion of yolk than hens which lay small 
eggs. Also individuals may show a decided tendency to vary 
from the flock type in quite different degrees in different 
characters. 
4. The eggs of an individual tend to be either uniform or 
variable in all the egg characters but certain individuals may 
be variable in certain egg characters and uniform in others. 
5. An individual is in general less variable than the race in 
respect to egg characters; but certain individuals may show a 
variation in an egg character which is relatively as great as the 
variation in the race. Also certain egg characters (particularly 
yolk weight) show a decided tendency to. approach the race 
variation in several individuals. 
6. The factors which bring about the individuality in re- 
spect to egg characters are too complex for analysis from the 
data at hand. 
II. Correlation of Egg Characters. 
1. Each egg character is related to every other egg char- 
acter, but different pairs of characters show a decidedly differ- 
