CHAPTER Vi 
INCUBATION 
The differences in the process of reproduction in birds and 
mammals is frequently misunderstood. The laying of the 
bird’s egg is not analogous to the birth of young in mammals. 
The female, whether bird or beast, forms a true egg which 
must be fertilized by the male sperm cell before the offspring 
can develop. In the mammal, if fertilization does not occur, 
the egg which is inconspicuous, passes out of the body and is 
lost. If fertilized, it passes into the womb where the young 
develops through the embryonic stages, being supplied with 
nourishment and oxygen directly by the mother. 
In the bird, the egg, fertilized or unfertilized, passes out 
of the body and, being of conspicuous size, is readily observed. 
The size of the egg is due to the supply of food material which 
is comparable with that supplied to the mammalian young 
during its stay in the mother’s womb. 
The reptiles lay eggs that are left to develop outside of the 
body of the mother, subject to the viscissitudes of the environ- 
ment. The young of the bird, being warm blooded, cannot de- 
velop without more uniform temperature than weather condi- 
tions ordinarily supply. This heat is supplied by the instinc- 
tive brooding habit of the mother bird. 
Fertility of Eggs 
In a state of nature the number of eggs laid by wild fowl 
are only as many as can be covered by the female. These are 
laid in the spring of the year, and one copulation of the male 
bird is sufficient to fertilize the entire clutch. Under domes- 
tication, the hen lays quite indefinitely, and is served by the 
male at frequent intervals. The fertilizing power of the male 
bird extends over a period of about 15 days. 
For most of my readers, it will be unnecessary to state that 
the male has no influence upon the other offspring than those 
which he actually fertilizes within this period. The belief in 
the influence of the first male upon the later hatches by an- 
other male is simply a superstition. 
The domestic chicken is decidedly polygamous. The com- 
mon rule is one male to 12 or 15 hens, I have had equally 
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