Apr. 19,1924 Relation of Antecedent Egg Production to Sex Rat io 
205 
The percentage of embryos dying before the twelfth day is of sufficient 
magnitude in any population so that if they were all of the same sex and if they 
were added to the deficient sex based on the observed ratios each observed ratio 
would be reversed. 
In Table IV the data for periods Nos. I, II, and III are arranged to show the 
sex ratios required in the embryos dying before the twelfth day to produce an 
equality of sexes in the total population, based on families of 10 or more. On 
this assumption, the results in the last column of Table IV show that for the 
three periods there would have to be a successive increase in the percentage of 
males in the embryos dying before the twelfth day. Period No. Ill shows an 
extremely high assumed sex ratio of embryos dying before the twelfth day, 
far higher than could reasonably be expected, particularly in view of other 
evidence presented. Moreover, the assumed ratios of embryos dying before the 
twelfth day for periods Nos. I and II are each considerably different in value 
from the observed ratios of embryos dying after the eleventh day. 
Table IV.— Showing the sex ratios required in the embryos dying before the twelfth 
day to produce an equality of sexes in total population , based on families of 10 
or more 
Period No. 
Embryos dying 
after eleventh day 
Chicks hatched 
Observed 
sex ratios 
of em¬ 
bryos dy¬ 
ing after 
eleventh 
day 
Observed 
sex ratios 
of chicks 
hatched 
Distribution of em¬ 
bryos dying be¬ 
fore twelfth day 
to produce an 
equality of sexes 
in total popu¬ 
lation 
Assumed 
sex ratio 
of em¬ 
bryos 
dying 
before 
twelfth 
day to 
produce 
an equal¬ 
ity of 
sexes in 
total 
popula¬ 
tion 
Females 
Males 
Females 
Males 
Females 
Males 
I .. 
II . 
III..... 
146 
169 
° 338 
109 
120 
a 197 
207 
310 
338 
337 
47.74 
46.52 
a 36.82 
62.02 
52.09 
196.50 
120.00 
103.00 
102.50 
142.00 
244.00 
34.28 
54.20 
70.31 
a Includes all embryos developing up to and after twelfth day, since during this period no chicks were 
allowed to hatch. 
It is obvious, therefore, that the number of embryos dying before the twelfth 
day is high enough in any population so that if a sufficient majority of the embryos 
were of one sex the mean sex ratio might be restored to approximate equality. 
The interesting feature in connection with such a supposition is that in period 
No. I the differential death rate would have to be considerably in favor of female 
survivals, since Rc?= 55.87±0.98, while in period No. II the differential death 
rate would have to be in favor of male survivals, since RS =48.82 ±0.80.* But 
the data in Table III show that the percentages of male embryos which died 
after the eleventh day in both periods are about the same, Re? D=47.74±2.02 
and Rc?D=46. 52±1.71. In other words, this means that from the time sex 
could be determined to hatching time there is a relatively higher death rate of 
females in both periods. Therefore, the higher death rate of females before 
hatching can not account for the absolute differences in the observed sex ratios 
between periods Nos. I and II. 
In the left half of Table V the embryos dying before the twelfth day are dis¬ 
tributed in such a way as to produce sex ratios of equality, and in the fifth column 
there are given the assumed ratios of these dead embryos. The assumed death 
rate of these embryos is in striking contrast with the observed death rate of the 
embryos dying after the eleventh day, as shown in the fifth and sixth columns of 
