204 
Joumal of Agricultural Research voi. xxvm, No. 3 
to the close of the normal hatching season. The matter of bagging and record¬ 
ing the eggs individually on the nineteenth day of incubation in preparation for 
hatching requires considerably more time and trouble than simply removing 
the eggs from the incubators on the nineteenth day for dissecting all chicks in 
the shell. This is the only reason that no actual hatching was allowed to take 
place after the hatching season was over. It is realized now, however, that the 
death rate of each sex for the season subsequent to the normal hatching season 
might have some significance, and it is anticipated that data on this point will 
be made available in the near future. 
Table III shows for the two periods (No. I), from the commencement of laying 
to the end of February, and (No. II) the normal hatching season, Mareh and 
April, (1) the number of embryos dead before the twelfth day and in which sex 
was not determined, (2) the per cent these constitute of the total number of 
embryos, both dead and hatched, i. e., of fertile eggs, (3) the number of female 
embryos dead between the eleventh day and hatching, (4) the number of male 
embryos dead, (5) the number of females hatched, (6) the number of males 
hatched, (7) per cent males in embryos dead after eleventh day, (8) per cent 
males in chickens hatched, (9) per cent males of all sexes determined. 
Table III.— Showing the relation of prenatal mortality to the sex ratio , based on 
families of 10 or more 
Period No. I.—From the Commencement of Laying to the end of February 
Year 
Embryos dy¬ 
ing before 
twelfth day 
Embryos dying 
after eleventh 
day 
Hatched 
Sex ratio 
of embryos 
dying after 
eleventh 
day 
Sex ratio 
of chicks 
hatched 
Sex ratio 
Num¬ 
ber 
Percent 
of all 
em¬ 
bryos 
Fe¬ 
males 
Males 
Fe¬ 
males 
Males 
1919-20. 
126 
31.97 
47 
34 
61 
126 
41.97dt3.98 
67.38dbl. H 
59.70±2. 02 
1920-21.. 
75 
32.33 
27 
27 
41 
62 
50.00±3. 74 
60.19±1. 24 
56.69±1.53 
1921-22__ 
98 
20.78 
72 
48 
105 
150 
47. 00±1.43 
58.82±1.06 
52.80rbl. 18 
Total_ 
299 
27.20 
146 
109 
207 
338 
47. 74±2. 02 
62. 02±0. 74 
55.87dt0.98 
Period No. II.— Normal Hatching Season, March and April 
1919-20.. 
143 
29.73 
65 
45 
113 
115 
45. 91=t2. 88 
50.44±1. 04 
47. 34rfc0. 83 
1920-21.... 
32 
14.48 
31 
30 
56 
72 
49.18±2.14 
56. 25±1. 67 
53.97±2.16 
1921-22.. 
87 
17.74 
73 
45 
141 
150 
48.13±2. 53 
51. 55±1. 51 
47.68±0. 93 
Total.. 
262 
21.87 
169 
120 
310 
337 ! 
I 
46. 52±1. 71 
52.09±0.89 
48. 82±0. 80 
Taking Table III as a whole, four things stand out prominently: (1) The 
percentage of embryos dying before the twelfth day fluctuates from year to yea r 
in both periods, but for each year the percentages are lower in period No. II than 
in period No. I; (2) with the exception of the year 1920-21, there were slightly 
fewer males than females that died after the eleventh day in period No. I as com¬ 
pared with period No. II, the percentages for the two periods being respectively 
47.74±2.02 and 46.52±1.71; (3) in every case there were more males than 
females that hatched, but for period No. I the proportion was much higher than 
for period No. II, i. e., 62.02±0.74 as compared with 52.09±0.89; (4) in each 
year in period No. I the percentage of males of all sexes determined was relatively 
high, that for the period as a whole being 55.87±0.98, while in each year except 
1920-21 in period No. II the percentage of males was below fifty, that for the 
period as a whole being 48.82 ±0.80. 
