Apr. 19,1924 Relation of Antecedent Egg Production to Sex Ratio 
207 
mortality between period Nos. I and II. Some other explanation must be found 
for the differential sex ratio existing between the two periods. 
Is there a differential hatching rate of the sexes in the two periods? Appar¬ 
ently so, as shown by a comparison of the Rc?H and the Ref columns in Table 
III. The percentage of males hatching, Ref H, is higher in every case than the 
percentage of males in the total population, Ref. In period No. I, Ref H =62.02 
±0.74, while in period No. II, Ref H =52.09±0.89. The difference with its prob¬ 
able error is 9.93 ±1.16 and is equally as significant as the difference in sex ratios 
between the two periods, 7.05 ±1.22, as indicated previously. It may be said, 
therefore, that the difference in the mean sex ratios between the two periods is 
affected primarily by the greater absolute number of males produced in the 
first period. 
These observations lead to the conclusion that the differential sex ratio existing 
between the period from the commencement of laying to the end of February 
and the period of the normal hatching season can not be accounted for by a 
differential prenatal mortality but is accounted for by a differential hatching 
ratio based upon absolute numbers of the sexes produced. Such a situation 
rests upon a genetic or physiological interpretation. 
3. THE RELATION OF EGG PRODUCTION TO THE SEX RATIO 
The nature of the results considered so far suggest a possible correlation 
between egg production and the sex ratio. In order to ascertain if such is the 
case the records were gone over carefully and families of 10 or more were selected 
from each mating, based upon the antecedent egg production. The families 
were so selected as to eliminate the influence of prenatal mortality as much as 
possible, in order that each sex ratio determined might represent the highest 
possible proportion of its total population. The families were grouped into six 
representative classes, based upon the antecedent egg production. The six 
classes include those hens which laid from 0 to 20, from 21 to 40, from 41 to 60, 
from 61 to 80, from 81 to 100, and from 101 to 120 eggs, respectively, prior to 
selection of the families on which sex ratios were determined. (See Table VI.) 
Table VI .—Showing the relation between antecedent egg production and sex ratio 
Class 
Antece¬ 
dent pro¬ 
duction 
| Average 
antece- 
j dent pro- 
| duction 
! 
( . 
Embryos 
dying 
before 
twelfth 
day 
Females 
Males 
Sex ratio 
Differences 
1__ 
0-20 
i 
4.79 
25 
102 
173 
62.91±1.44 
5.45±2. 61 
2... 
21-40 
27.86 
! 
19 
94 
127 
57.46±1.88 
12.46d=2. 77 
3... 
41-60 i 
1 47.85 
! 
18 
165 
135 
45.00±2.04 
0.39±2.15 
4... 
61-80 
69. 45 
12 
108 
87 
44.61=fc0.69 
6.96±1.21 
5.... 
81-100 
88.92 
16 
101 
61 
37.65±1.00 
5.45=hl. 52 
6...... 
101-120 
114. 50 
8 
80 
38 
32. 20±1.15 
There are four cases in which the sex ratio deviates considerably from the 
normal of 48.82 ±0.80, namely, classes 1, 2, 5, and 6. In none of these cases is 
the number of embryos dying before sex could be determined great enough to 
account for the deviation in the sex ratio. Furthermore, in the first two cases 
the numbers of dead embryos would have to be added to the numbers of females 
and in the last two cases they would have to be added to the numbers of males. 
