224 
Journal of Agricultural Research 
Vol. XXXI, No. 3 
EXPERIMENTAL DATA 
In Table I is shown, for each of the four groups of birds, the rela¬ 
tionship between the weight of eggs from which males were hatched 
and the weight of the eggs from which females were hatched. In 
the case of the eggs from the Barred Plymouth Rock yearling hens, 
those giving rise to males have a slightly lower mean weight than the 
eggs giving rise to females, but in the other three cases the reverse 
is true. In no case, however, is the difference in weights significant, 
the differences with their probable errors being 0.34 ± 0.55, 0.60 ± 0.42, 
0.44 ±0.48, and 0.48 ±0.34 gm. 
This situation is in harmony with the results obtained by the 
senior writer 2 in the case of eggs from 30 Barred Plymouth Rock 
pullets mated to Brown Leghorn males, and by both authors 3 in 
the case of eggs from 153 Barred Plymouth Rock females mated to 
Rhode Island Red males. It seems, then, that selection of hatching 
eggs according to weight can not be expected to affect the sex ratio 
of chicks hatched therefrom. 
Table I. — Relationship between the mean weight of eggs producing males and the 
mean weight of eggs producing females in each of four groups; and the relation¬ 
ship of the mean weight of eggs producing males and females, respectively , between 
the yearling hen and pullet groups of each breed 
Group 
Number 
Mean weight 
of eggs 
from which 
males were 
hatched 
Number 
Mean weight 
of eggs 
from which 
females were 
hatched 
Difference 
Rhode Island Red yearlings i_ 
66 
Gm. 
59.88±0.36 
49 
Gm. 
59.54±0.41 
0.34±0.55 
Rhode Island Red pullets... 
59 
56.61± . 30 
54 
56.01± . 30 
. 60± .42 
Difference_ 
3.27=t . 47 
3.53± . 51 
Barred Plymouth Rock yearlings_ 
63 
59.91± . 30 
49 
60.35± .37 
. 44± . 48 
Barred Plymouth Rock pullets_ 
123 
57.93± . 24 
106 
57.45± . 24 
.48± .34 
Difference... 
1.98± .38 
2.90± .44 
Table I shows, for each of the two breeds, in the case of eggs giving 
rise to males and females, respectively, the difference in weights of 
eggs from yearling hens and from pullets. In both breeds the eggs 
from yearling hens were considerably heavier than the eggs from 
pullets. In the Rhode Island Reds, the difference in the weights of 
eggs giving rise to males is 3.27 ±0.47 gm. in favor of the eggs from 
the yearling hens, and the difference in the weights of eggs giving rise 
to females is 3.53 ±0.51 gm. in favor of the yearling hens. In the 
Barred Plymouth Rocks, the difference in the weights of eggs giving 
rise to males is 1.98 ±0.38 gm. in favor of the yearling hens, and the 
difference in the weights of eggs giving rise to females is 2.90 ±0.44 
gm. In each case, the difference is considerably more than three 
times its probable error, and it is seen, then, that in both breeds the 
yearling hens laid significantly heavier eggs than the pullets. 
The weights of the chicks of each sex from each of the four groups 
of birds are shown in Table II. In each of the four groups the mean 
weight of the females is lighter than that of the males, but in no 
2 JULL, M. A. THE RELATION OF ANTECEDENT EGG PRODUCTION TO THE SEX RATIO OF THE DOMESTIC 
fowl. Jour. Agr. Research 28:199-224. 1924. 
3 Jull, M. A., and Quinn, J. P. the shape and weight of eggs in relation to the sex of chicks 
in the domestic fowl. Jour. Agr. Research 29:195-202. 1924. 
