212 
Journal of Agricultural Research 
Vol. XXVIII, No. 3 
of the egg in the cycle. ” The author (29) has shown that in the domestic fowl 
albumen weight is more highly correlated with egg weight than is yolk weight, 
while yolk weight is more highly correlated with egg weight than is shell weight. 
Also, the component parts of the egg contribute in different degrees at different 
times of the year toward the total egg weight. Increase in the size of yolk appar¬ 
ently is a direct effect of the analogous increase in the size of the body. 
Finally, there is reported to be in pigeons a correlation between egg weight and 
yolk weight, a point which is not adequately demonstrated in the presentation 
of the material, and there seem to be significant correlations between both egg 
weight and yolk weight and sex. 'In the case of the domestic fowl, there is also 
a correlation between egg weight and yolk weight, in the material of this study 
found to be r=0.804± 0.014, but there is no correlation between egg weight and 
sex, as shown in Table VII. 
6. THE RELATION OF YOLK WATER CONTENT TO SEX RATIO 
In an analysis of all possible factors which might affect the sex ratio, that of 
the water content of the yolks of eggs might reasonably be supposed to be of 
minor importance. But since in an extensive series of investigations with another 
class of birds the factor of yolk water content is assumed to be of considerable 
significance, it is well to test the application of the theory in the case of the 
domestic fowl. 
Table X .—Showing the relation between yolk water content and sex ratio 
Class 
Produc¬ 
tion 
Average 
weight 
fresh 
yolk 
Average 
weight 
dried 
yolk 
Water 
Sex ratio 
1.... 
0-20 
Grams 
16.09 
Grams 
8.21 
Per cent 
48.97 
62.91±1.44 
2 ..... 
21-40 
16.26 
8.42 
48,15 
50.05 
57.46±1.88 
3......... 
41-60 
18.32 
9.16 
45.00±2.04 
4__........ 
61-80 
19.81 
9.88 
50.13 
44. 61±0.69 
5..... 
81-100 
18.94 
9.73 
48.62 
37.65±1. 00 
6 ...-. 
101-120 
18.91 
9.39 
50.34 
32. 20dtl. 15 
With two exceptions, there seems to be a slight increase in the percentage of 
water contained in the yolks as production increases, but the differences between 
any two classes are very small indeed and may not be significant. The slightly 
higher percentages of water content occur during the periods of production 
when more females than males are produced. But in the case of pigeons the 
reverse seems to be the case and two comments by Riddle (46, 47) deserve special 
notice. 
The fifth correlation relates to the percentage of water in eggs of spring and autumn, and in the two 
eggs of a clutch. These figures for one series of analyses are given on the chart (3) last examined. They 
show a higher water content for the eggs of the spring (male producers) as compared with the eggs of autumn 
(female producers); indeed each pair of eggs from the first of the season onward has a slightly higher moisture 
value than the pair that follows it. The analyses further show a higher percentage of water in the first 
egg of the clutch than in the second in all cases. If the results of my 800 analyses all ran as smoothly as 
do the 8 of this series, there would be no doubt of a perfect correlation of high moisture values with small 
eggs; i. e., with male producing eggs—both small eggs of season and small eggs of individual clutches. But 
the results are not thus uniform and smooth. There are some series which seem seriously to depart from 
the order noted above. These can not be discussed here. We can, however, record our own belief that 
the situation in the ehart is, in the main, indicated by the moisture determination. (46, pp. 402-408 ). 
Chart III, referred to above, is the same as Table VII in the 1917 publication, 
of which Riddle says (47, p. 836): 
Two additional methods of determining the amount of water in the yolks, give a satisfactory confirma* 
tion of the conclusion that the male-producing ovum contains a higher percentage of water than does the 
female-producing ovum. 
