B06 FORMATION OF THE EGG AND CHICKEN 
Another peculiar condition which is often interesting to the 
uninitiated is the presence of a perfectly formed egg within another 
egg. This is due to the fact that, by the contraction of the ovi- 
duct, the completed egg has been forced back into the albumin- 
secreting section of the duct after being coated by the shell liquid. 
It remains there until it is met by another yolk, when the two 
pass together through the uterus, or shell-forming part of the ovi- 
duct, and the entire mass receives another shell. 
Extremely small eggs are common at the beginning or end of a 
laying period; this is in part due to a diminution in the size, hence 
in the lessened secreting power, of the oviduct. 
y Double yolk 
/ t 
\ 
Fig. 147,—Abnormal eggs shown in comparison with a normal one. The elongated 
form is due to the contraction of the oviduct. 
Distorted and misshapen eggs are accounted for by a diseased 
condition of the lower part of the oviduct and an accompanying 
contraction which prevents the expansion necessary when the egg 
leaves the oviduct and enters the cloaca; consequently, it is forced 
through a small opening and, as the shell is soft, is compressed 
into peculiar or elongated shape. These malformations are largely 
the effects of domestication, and are rare when the flock receives 
proper care and feeding (Fig. 147). 
Fertile Eggs.—Every egg, whether fertile or not, contains the 
female germ, which, however, cannot develop or grow until it has 
been fertilized by the male germ. The latter is contained in a 
