210 
Journal of Agricultural Research 
Vol. XXVIII, No. 3 
It is apparent from Table VII that the average egg weight increases as egg 
production increases, until about 60 eggs are laid. Then the average egg weight 
drops slightly until about 100 eggs are laid, after which there is a more marked 
drop. 
In a study of the nature and causes of changes in egg weight in relation to 
annual production in 40 Barred Plymouth Rock pullets, the author (30) has 
shown that the earlier in life laying commences the lower is the mean weight of 
the first 10 eggs laid and the lower is the mean weight of the total production. 
He has also shown that increase in egg weight is analogous to increase in body 
weight of the birds laying the eggs, and that the earlier in life laying commences 
the later in life both maximum body weight and maximum egg weight are 
attained. In another study, the author 4 has shown that the later in life laying 
commences the more nearly do the first eggs laid approach the mean egg weight 
of the total annual production. In other words, among the 59 Barred Plymouth 
Rock pullets under consideration, it has been shown that those commencing to 
lay as late as the month of December laid approximately as large eggs at that 
time as any other time during the first year of production. In view of these 
observations and in view of the correlation between antecedent production and 
sex ratio demonstrated to exist in connection with the birds used in this study, 
it is hardly to be expected that there should exist any significant correlation 
between egg weight and sex ratio based on annual production. 
In Table VII it is shown that there is not more than 4 per cent difference 
between the average weights o£ any two contiguous groups, and it is hardly 
conceivable that such a slight difference should have any significance in this 
study, particularly since the percentage differences do not follow a regular 
order, whereas the sex ratios tend to decrease somewhat regularly. Taking into 
consideration the differences with their probable errors, it is evident that there 
is no significant relation between egg weight and antecedent egg production and 
certainly no correlation between egg weight and sex ratio. This point should be 
comparatively easy to demonstrate, however, if the weights of the eggs giving 
rise to the two sexes are considered. 
Table VIII.— Showing the relation between weights of eggs giving rise to females 
and males, respectively, and sex ratio 
i 
1 
Class ! Production 
i 
i 
Average egg weight 
Difference 
Sex ratio 
Females 
Males 
I 
1 . j 0- 20 
2 ... 21-40 
3 . 1 41- 60 
4 . J 61- 80 
5 .....| 81-100 
6 .....] 101-120 
j 
Grams 
51.37±0.95 
54. 25±0.48 
54.64±0. 36 
55. 64±0. 51 
54. 56±0. 99 
52.18=bl. 21 
Grams 
51.45±0.98 
54.32db0.52 
53.93±0.29 
55.40dt0.42 
54.00±1.12 
53. 24dhl. 03 
0.08±1.36 
0.07±0.71 
0.71±0.46 
0.24±0.66 
0. 56±1.49 
1.06±1. 59 
62.91±1.44 
57.46rbl. 88 
45.00±2.04 
44.61±0.69 
37. G5±l. 00 
32. 20±1.15 
The difference in weights between the eggs producing the two sexes are not 
regular, when the production classes are compared. For instance, in the first, 
second, and sixth classes the average weights of the eggs giving rise to males 
are slightly in excess of the average weights of eggs giving rise to females, while 
in the third, fourth and fifth classes the reverse is true. Furthermore, the differ¬ 
ences in weights between the sexes are relatively slight and are not at all signifi¬ 
cant. It may be concluded, therefore, that there is no correlation between egg 
4 Jull, M. A. Increase in egg weight in relation to time laying commences. Amer. Nat. (In 
press.) 
