688 
Journal of Agricultural Research 
Vol. XXXI, No. 7 
2 eggs were set, both of which hatched, giving a hatching percentage 
of 100, while in the shape-index class 63.00 to 64.99 3 eggs were set, 
2 of which were fertile and of which only 1 hatched, giving a hatching 
percentage of 50 for the fertile eggs. That is, a difference of 1 chick 
m absolute numbers hatched made a difference of 50 per cent of the 
fertile eggs that hatched. 
In Table II all eggs set have been grouped in classes differing by 
greater increments of shape index than is shown in Table I, the 
shape-index classes being divided into three groups, low (61.00 to 
68.99), medium (69.00 to 76.99), and high (77.00 to 84.99). 
Table II. — Incubation results of eggs for groups of low, medium, and high shape 
index classes 
[Eggs laid by 24 Barred Plymouth Rock pullets] 
Shape index 
Number 
set 
Infertile 
Died 
early 
Died 
late 
Hatched 
Per cent of 
fertile eggs 
hatched 
61.00 to 68.99..... 
51 
2 
5 
17 
27 
55.10±7.68 
69.00 to 76.99_____ 
835 
78 
83 
179 
495 
65.39± .63 
77.00 to 84.99__ 
367 
35 
33 
78 
221 
66.60±2. 75 
Of particular interest in Table II is the per cent of fertile eggs 
hatched in each of the three groups. The low shape-index group 
shows a hatching percentage of 55.10 ±7.68, the medium shape-index 
group 65.39 ±0.63, the high shape-index group 66.60 ±2.75. The 
difference in hatchability between the low and medium groups is 
10.29 ±7.70 and is therefore not significant. The difference in 
hatchability between the medium and high groups is. 1.21 ±2.82, 
and also is not significant. The difference in hatchability between 
the low and high groups is 11.50 ±8.16, and is not significant. It 
may be concluded, therefore, that so far as the eggs of the flock as a 
whole are concerned there is no relationship between the shape of 
an egg and its hatching quality. 
To determine the relation between mean shape index and hatch¬ 
ing quality within the individual, the data were regrouped in Table 
III and sf low for each pullet the number and mean shape index of 
the eggs whose embryos died in shell and of the eggs which hatched. 
The eggs whose embryos died early and those whose embryos died 
late have been grouped together, because in several cases tne num¬ 
bers of each were too small to be considered separately. More¬ 
over, the factor of importance is to determine the relationship in 
respect to mean shape index between the eggs which failed to hatch 
ana those which hatched, the infertile eggs not being taken into 
account. 
