At the outset the
under portion of the body appears insignificant in comparison with the
upper portion. Of the two ducts that lead from the heart, the one
proceeds towards the circumjacent integument, and the other, like a
navel-string, towards the yolk. The life-element of the chick is in
the white of the egg, and the nutriment comes through the navel-string
out of the yolk.
When the egg is now ten days old the chick and all its parts are
distinctly visible. The head is still larger than the rest of its
body, and the eyes larger than the head, but still devoid of vision.
The eyes, if removed about this time, are found to be larger than
beans, and black; if the cuticle be peeled off them there is a white
and cold liquid inside, quite glittering in the sunlight, but there is
no hard substance whatsoever. Such is the condition of the head and
eyes. At this time also the larger internal organs are visible, as
also the stomach and the arrangement of the viscera; and veins that
seem to proceed from the heart are now close to the navel. From the
navel there stretch a pair of veins; one towards the membrane that
envelops the yolk (and, by the way, the yolk is now liquid, or more so
than is normal), and the other towards that membrane which envelops
collectively the membrane wherein the chick lies, the membrane of
the yolk, and the intervening liquid.
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