The yolk and the white are diverse not only in colour but also
in properties. Thus, the yolk congeals under the influence of cold,
whereas the white instead of congealing is inclined rather to liquefy.
Again, the white stiffens under the influence of fire, whereas the
yolk does not stiffen; but, unless it be burnt through and through, it
remains soft, and in point of fact is inclined to set or to harden
more from the boiling than from the roasting of the egg. The yolk
and the white are separated by a membrane from one another. The
so-called 'hail-stones', or treadles, that are found at the
extremity of the yellow in no way contribute towards generation, as
some erroneously suppose: they are two in number, one below and the
other above. If you take out of the shells a number of yolks and a
number of whites and pour them into a sauce pan and boil them slowly
over a low fire, the yolks will gather into the centre and the
whites will set all around them.

Young hens are the first to lay, and they do so at the beginning
of spring and lay more eggs than the older hens, but the eggs of the
younger hens are comparatively small. As a general rule, if hens get
no brooding they pine and sicken. After copulation hens shiver and
shake themselves, and often kick rubbish about all round them-and
this, by the way, they do sometimes after laying-whereas pigeons trail
their rumps on the ground, and geese dive under the water.
Conception of the true egg and conformation of the wind-egg take place
rapidly with most birds; as for instance with the hen-partridge when
in heat. The fact is that, when she stands to windward and within
scent of the male, she conceives, and becomes useless for decoy
purposes: for, by the way, the partridge appears to have a very
acute sense of smell.