206 
Journal of Agricultural Research voi. xxvm, No. 3 
Table V. Since there is no valid reason for supposing a death rate in the sexes 
of embryos dying before the twelfth day different from a death rate in the sexes 
of embryos dying after the eleventh day, it may be concluded accordingly that 
the death rate in the embryos dying before the twelfth day apparently does not 
affect the mean sex ratio differently from the death rate in embryos dying after 
the eleventh day. In the right half of Table V there are shown the calculated 
sex ratios when the death rate of the embryos dying before the twelfth day is 
assumed to be the same as for the embryos dying after the eleventh day. A 
comparison of the figures in the last two columns of Table V would indicate a 
relative difference in the percentage of males produced in period No. I as com¬ 
pared with period No. II. 
Table V .—Showing the results obtained when the embryos dying before twelfth day 
are distributed to produce an equality of sexes and on the basis of the observed 
sex ratios of embryos dying after the eleventh day; based on families of 10 or more 
Period No. I.—From the Commencement of Laying to the End of February 
Year 
Em¬ 
bryos 
dying 
before 
twelfth 
day 
Distribution of 
embryos dying 
before twelfth 
day to produce an 
equality of sexes 
As¬ 
sumed 
sex ratio 
of em¬ 
bryos 
dying 
before 
twelfth 
day 
Ob¬ 
served 
sex ratios 
of em¬ 
bryos 
dying 
after 
eleventh 
day 
Distribution of 
embryos dying 
before twelfth 
"day on basis of 
observed sex ratio 
of embryos dying 
after eleventh day 
Calcu¬ 
lated sex 
ratio 
Ob¬ 
served 
sex ratio 
Females 
Males 
Females 
Males 
1919-20. ... 
126 
89.00 
37.00 
29.36 
41.97 
73.42 
52.58 
53.95 
59.70 
1920-21.. 
75 
48.00 
27.00 
36.00 
50.00 
37.50 
37.50 
54.53 
56.69 
1921-22... 
98 
59.50 
38.50 
39.28 
47.00 
51.94 
46.06 
52.00 
52.80 
Total.. 
299 
196.50 
102.50 
34.28 
47.74 
156.26 
142. 74 
53.66 
55.87 
Period No. II.— Normal Hatching Season, March and April 
1919-20--.- 
143 
62.50 
80.50 
56.29 
45.91 
77.35 
65.65 
46.91 
47.34 
1920-21.. 
32 
23.50 
8.50 
26.56 
49.18 
16.26 
15. 74 
53.28 
53.97 
1921-22.. 
87 
34.00 
53.00 
60.92 
48.13 
45.13 
41.87 
47.76 
47.68 
Total. 
262 
120.00 
142.00 
54.20 
46.52 
150.12 
111.88 
47.48 
48.82 
Is there a differential death rate in the embryos dying after the eleventh day? 
Considering the data in Table III, it will be observed that the percentage of male 
embryos is lower in every case, except for the year 1920-21, in periods No. I and 
II, than the mean sex ratio. Pearl (44, V • 4&4) found the sex ratio of the dead 
embryos for the years 1916 and 1917 to be 48.3 ±0.77. As between Pearl's 
ratio and the ratio for period No. I in Table III, the difference with its probable 
error is 0.56 ±2.16, and as between Pearl's ratio and the ratio for period No. II 
in Table III, the difference with its probable error is 1.78 ±1.87. Nevertheless, 
the data in Table III seem to show that in period No. I the death rate in embryos 
dying after the eleventh day does account to a slight extent for the high mean 
sex ratio, Ref =55.87±0.98. But the same interpretation can not be placed 
upon the data in period No. II, since the death rate is practically the same as 
in period No. I, but the mean sex ratio is considerably lower, Ref = 48.82±0. 80. 
In period No. I, Ref D =47.74±2.02, while in period No. II, Ref D =46.52±1.71. 
The difference with its probable error is 1.22 ±2.65 and is, therefore, of no sig¬ 
nificance. In other words, there is practically no difference in the known prenatal 
