Apr. 19,1924 Relation of Antecedent Egg Production to Sex Ratio 221 
SUMMARY 
1. In the case of the domestic fowl, there is found to be a significant negative 
correlation between antecedent egg production and the sex ratio. 
2. The sex ratio of the three yearly populations is 48.41 ±0.47* 
3. The sex ratio, based on families of 10 or more, for the normal hatching 
season, is 48.82 ±0.80. 
4. With the annual egg production divided into classes of 20 eggs each, the 
sex ratio, based upon antecedent production, is as follows: 0-20, 62.91 ±1.44; 
21-40, 57.46±1.88; 41-60, 45.00±2.04; 61-80, 44.61 ±0.69; 81-100, 37.65±1.00; 
101-120, 32.20±1.15. 
5. The correlation between antecedent egg production and sex ratio is 
—0.704±0.037. 
6. The correlation between season and sex ratio is —0.165±0.076, and is 
probably incidental. 
7. There is no apparent correlation between egg weight and sex ratio. 
8. There is no apparent correlation between yolk weight and sex ratio. 
9. There is no apparent correlation between yolk water content and sex ratio. 
10. The feeding and general management of the birds having been practically 
identical for the three years, it is obvious that general environmental conditions 
have not affected the sex ratio. 
11. The variation in the sex ratio in relation to egg production can not be 
accounted for on the basis of prenatal mortality. 
12. There is no indication of reversibility of sex, this possibility having been 
tested by using the dominant sex-linked barring character of Barred Plymouth 
Rocks with the recessive plumage color character of Brown Leghorns. 
13. It is apparent that male-producing zygotes are produced in excess of 
female-producing zygotes during the early period of egg production and that as 
egg production increases female-producing zygotes tend to be produced in excess. 
14. An hypothesis is developed to account for differential maturation, which 
in turn would account for the modified sex ratios. 
LITERATURE CITED 
(1) Atwood, H., and Weakley, C. E., Jr. 
1917. CERTAIN CHARACTERISTICS OF HEN EGGS. W. Va. Agr. Exp. Sta. 
Bui. 166, 35 p. 
(2) Boring, A. M., and Pearl, R. 
1917. SEX STUDIES. IX. INTERSTITIAL CELLS IN THE REPRODUCTIVE 
organs of the chicken. Anat. Rec. 13: 253-268, illus. 
(3) - 
1918. sex studies, xi. hermaphrodite birds. Jour. Exp. Zool. 25: 
1-47, illus. 
(4) Cole, L. J., and Lippincott, W. A. 
1919. the relation of plumage to ovarian condition in a barred 
Plymouth rock pullet. Biol. Bui. 36: 167-182, illus. 
(5) Crew, F. A. E. 
1923. STUDIES IN INTERSEXUALITY. II. SEX-REVERSAL IN THE FOWL. 
Proc. Roy. Soc. [London] (B) 95: 256-278, illus. 
(6) - and Huxley, J. S. 
1923. THE RELATION OF INTERNAL SECRETION TO REPRODUCTION AND 
GROWTH IN THE DOMESTIC FOWL. I. EFFECT OF THYROID FEED¬ 
ING ON GROWTH RATE, FEATHERING, AND EGG PRODUCTION. Vet. 
Jour. 79: 343-348. 
