
The amount of pigment deposited in the shell seems to 
be positively correlated with hatehability. Godfrey (1947) ob- 
served that in New Hampshire chickens and White Plymouth Rock 
chickens extremely lightecolored eggs hatched poorly in compari- 
son with medium and dark brown ones. This observation was 
corroborated by Funk and Forward (1949) in New Hampshire chick-~ 
ens, who found the per cent hatchability of dark brown, medium 
and light brown eggs to be 74.1, 70.0 and 55.0 per cent re- 
spectively. Embryonic mortality during the first 18 days of 
incubation and also during the hatching period was greater in 
light brown eggs. 
The rate of evaporation also reduced hatchability in 
most cases; evaporation is regulated by the shell texture or 
porosity of the shell. Hays and Spear (1951) found in experi-= 
ments with eggs of Rhode Island Red chickens that the weight loss 
to 17 days of incubation varied between 6.5 and 12 per cent with- 
out affecting hatchability; losses greater than 12 per cent 
lowered hatchability considerably. The hatchability obtained 
in his experiments was 71 to 92 per cent with losses between 
6.5 and 12 per cent, and 49 to 67 per cent with losses between 
13 and 18 per cent. 
Rauch (1952) showed that the mean pore diameter in 
shells of eggs producing hatched chicks was less than in shells 
from non=hatching eggs. The pore size for shells of hatched 
chicks was between 9.4 and 10.1 u.,those for shells of non- 
hatehing chicks was between 12.0 and 21.8 u. 
7. Miscellaneous factors. 
Olsen and Haynes (1949) conducted studies on freshly 
laid eggs to determine the effect of certain abnormal character-~- 
istics on fertility and hatchability. Four per cent of the 
48,000 eggs had one of the following characteristics. The hatch- 
ability of fertile eggs showing these characteristics was as 
follows: small eggs, 80.0 per cent; large blood spots, 71.5 
per cent; extra large eggs, 70.8 per cent; misplaced air cells, 
68.1 per cent; misshapen eggs, 48.9 per cent; cracked eggs, 
53.2 per cent; eggs with poor shells, 47.3 per cent; loose air 
cells, 32.4 per cent. The average hatchability for reference 
control eggs was 87.2 per cent. 
Fertility and hatchability may be affected by sub- 
stances toxic to the embryo entering into the components of the 
egg. Polin et al. (1961) found that the concentration of 
Glycarbylamide, a medicant used for the prevention of coccidiosis 
in chickens, in the egg white increased with increasing levels 
of the drug in the feed until a maximum concentration averaging 
12.9 ug. per gram at dietary levels of 0.10 per cent. fhe 
drug was fed to 10 White Leghorn females and to one rooster, at 
levels between .02 and 0.16 per cent during 21 days. Concentra- 
tion of 0.08 and 0.16 caused a significant decrease in 
30 
