Apr. 19 , 1924 Relation of Antecedent Egg Production to S ex Ra tio 213 
Not only is the degree of correlation between yolk water content and sex not 
shown, which in 800 analyses should be readily demonstrable, but the records 
of percentages of water content of yolks are given for one female only. The 
records as given in Chart III and Table VII show 8 determinations, 2 for the 
month of May, 1912, 4 for the month of July, 1 for November, and 1 for Decem¬ 
ber. Finally, it would appear that more data are necessary, in the case of the 
domestic fowl at least, before a correlation may be said to exist between yolk 
water content and sex ratio. 
DISCUSSION 
Concerning this study, the situation seems to be as follows: (1) The sex ratio 
decreases from considerably above fifty in the early period of egg production to 
considerably below fifty in the advanced period of egg production; (2) there 
is no indication of reversibility of sex; (3) there is no indication of a modification 
of the sex ratio through external agencies, such as management and feeding of 
the laying stock; (4) prenatal mortality does not account for the different sex 
ratios observed; (5) a differential hatching rate of the sexes does account for 
the different ratios observed, inasmuch as it has been established that the rela¬ 
tive proportion of male-producing to female-producing zygotes changes in rela¬ 
tion to antecedent egg production; (6) the most reasonable explanation to 
account for the changes in the proportion of male-producing to female-producing 
zygotes seems to be differential maturation of the chromosome complexes. 
1. THE SEX CHROMOSOMES IN THE DOMESTIC FOWL 
In the case ofitheyomestic fowl Guyer (21) described an X chromosome in the 
male, and in subsequent observations he (22) confirmed the original descrip¬ 
tion. Guyer’s observations, however, indicate that functionally the male is 
homozygous, which is in keeping with the apparent homozygosity of the male 
and the heterozygosity of the female demonstrated by breeding tests, when 
sex-linked characters are involved. Hance (24) has shown that the chromosome 
number falls within the limits of 30 to 34 and that in the male there are 2 simi¬ 
lar chromosomes corresponding in shape and size to the largest unmated chromo¬ 
some of the female chromosome complex. The results of both Guyer and Hance 
are in agreement in demonstrating that the male fowl is homozygous and the 
female heterozygous for sex, as the phenomena of sex-linked inheritance in the 
domestic fowl demand. * 
2. SEX RATIO DETERMINATIONS IN THE DOMESTIC FOWL 
As a result of this study it has been found that the sex ratio of the domestic 
fowl, based on families of 10 or more, for the normal hatching season is 48.82± 
0.80. The sex ratio based upon annual production has been found to be 
48.41 ±0.47, which is in very close agreement with the sex ratio determined 
for the normal hatching season. But it has also been shown that the first eggs 
a pullet lays tend to produce a high proportion of males and that as production 
increases the male ratio decreases. 
There are few other statistics demonstrating the sex ratio in the domestic 
fowl. Darwin (7, p. 252) was probably the first to record the proportion of 
sexes on sufficient numbers to indicate reliability. In 1,001 Cochins reared 
during eight years by Stretch, as reported by Darwin, the sex ratio was 48.64,. 
but no reference is made as to whether the proportion of sexes as given was 
determined at hatching time or as the fowls approached maturity. The first 
edition of the “Descent of Man” was published in 1871, and it is highly improba- 
