Apr. is, 1924 Relation of A ntecedent Egg Production to Sex Ratio 
209 
Crew and Huxley ( 6 ) in a study of the sex ratios in the-Fx generation of a 
Rhode Island Red male Light Sussex female cross observes that as the season 
advanced the sex ratio decreased. During the spring months, February to 
June, the sex ratio was 50, while during August and September, the sex ratio 
was 42.62. The authors state as their opinion that “It is likely that this repre¬ 
sents a significant seasonal difference, * * In view of the results deter¬ 
mined in the present study, however, it seems probable that the modification 
in sex ratio obtained by Crew and Huxley can be explained on the basis of 
antecedent egg production. 
4. THE RELATION OF EGG WEIGHT TO SEX RATIO 
It is quite conceivable that there might be a correlation between egg production 
and egg weight, and if such were the case then there would also be a correlation 
between egg weight and sex ratio. If such a correlation were manifest, however, 
it might or might not be significant. 
The author {28), in a study of rates of growth in Barred Plymouth Rock 
chicks, observed a significant difference in the weights of eggs from which the 
females were obtained as compared with the weights of eggs from which the 
males were obtained. It should be explained here, however, that the only egg 
weights taken into consideration were those producing the chicks on which 
growth rates were determined, the records for analysis being selected at the con¬ 
clusion of the growth period. The weights of the eggs in which embryos died 
and the weights of the eggs producing chicks which died prior to the termination 
of the period of growth studied were not considered. Moreover, it is observed 
that in the relatively small population of chicks used in the growth study, 38 
females and 38 males, there were only 3 families of 10 or more. The difference 
in the weight of eggs producing the two sexes, 2.06±0.67, can not be considered 
as evidence bearing on the problem in this study where the weights of eggs pro¬ 
ducing the two sexes throughout the first year of production have been consid¬ 
ered, including the sexes which died between the eleventh and the twenty-first 
days and the sexes which hatched. 
It has been noted previously that for the production years 1920-21 and 1921-22 
all eggs were weighed daily as produced, and for each mating the weights have 
been grouped on the same basis of classification as used in Table VI. The 
average weights have been determined for the groups 0 to 20, 21 to 40, 41 to 
60, 61 to 80, 81 to 100, and 101 to 120 eggs, as produced. Not every group for 
each mating consisted of 20 eggs. One hen after a long rest might lay 12 eggs 
in 15 days and then might not lay again for another month. In such a case the 
average weight of the 12 eggs was determined and allocated to the proper group, 
according to the antecedent production. Where hens laid more or less continu¬ 
ously for a long period, then the production for that particular period was divided 
into groups of approximately 20 eggs each. A number of hens laid more than 
120 eggs, but the average weights of eggs beyond this production have not been 
taken into consideration because the numbers of sexes determined were so small 
as to prevent a true mean sex ratio being determined. The average weights 
classified as indicated are shown in Table VII. 
Table VII .—Showing the relation between egg weight and sex ratio 
Class 
Antecedent 
production 
Average 
egg weight 
Sex ratio 
0- 20 
21- 40 
41- 60 
61- 80 
81-100 
101-120 
Grams 
51.80±0.70 
53.91±0.69 
55.70±0. 59 
55.15±0. 52 
55.18±0. 57 
53.12±0. 52 
62.91±1.44 
57.46±1.88 
45.00±2.04 
44. 61 ±0.69 
37. 65±1.00 
32. 20±1.15 
