velop, the bird turns to the nest and to
the mate who is to share with her all this beautiful life. When the mate
has been chosen, both prepare the nest to receive the eggs, which will
soon be ready. It is during this period that the fertilizing fluid is
placed in the lower end of the egg-duct, whence the fertilizing cells,
by their power of motion, quickly make their way to the egg, which has
just begun its journey down the oviduct and is as yet without a shell.
The shell-less egg is well known to most country children, as hens often
lay one; and this will always happen where there is not lime enough in
the food of the poultry.

After the egg is fertilized it continues its slow journey down the
oviduct, which enlarges to accommodate it. At first the egg consists of
the yolk alone. This grows to its full size before it leaves the ovary.
The yolk in short _is_ the egg. But there is not enough food material in
it for the development of the bird, so as it passes down the egg-duct it
becomes coated by the so-called "white" of the egg, which is a substance
secreted from the lining of the egg-duct and is not alive, as is a
certain part of the yolk. It is merely stored-up food like that in the
morning-glory seed, for this egg is the seed of the bird. At the lower
end of the egg-duct there is secreted a limy liquid which covers the
shell-less egg and hardens, making the shell. So finally the fertilized
egg has its shell and is ready to be laid. When this time comes, the
bird seeks her nest, and the egg is laid or born, and lies warm and
living, like a jewel in the nest.

It is hardly necessary to add that the fertilizing cells in the male
bird have an origin similar to that of the ova. The testicles and their
ducts are too small to be easily seen in the young bird and in the
winter-time, but can be seen during reproductive activity. The male bird
can usually be told from the female by differences in color and plumage,
but where this is not the case the two sexes cannot be told apart
without actually killing and dissecting the birds, so very simple are
the generative organs.

The ripening of the reproductive elements in the bird occurs in the
spring of the year, and is always with a few exceptions accompanied by
the instinct of nest-making. The birds instinctively and joyfully
prepare the home for their young at this time, both parents joining to
make the pretty structure. With the child the higher emotions which
always accom