Eggs are not symmetrically shaped at both ends: in other
words, one end is comparatively sharp, and the other end is
comparatively blunt; and it is the latter end that protrudes first
at the time of laying. Long and pointed eggs are female; those that
are round, or more rounded at the narrow end, are male. Eggs are
hatched by the incubation of the mother-bird. In some cases, as in
Egypt, they are hatched spontaneously in the ground, by being buried
in dung heaps. A story is told of a toper in Syracuse, how he used
to put eggs into the ground under his rush-mat and to keep on drinking
until he hatched them. Instances have occurred of eggs being deposited
in warm vessels and getting hatched spontaneously.

The sperm of birds, as of animals in general, is white. After
the female has submitted to the male, she draws up the sperm to
underneath her midriff. At first it is little in size and white in
colour; by and by it is red, the colour of blood; as it grows, it
becomes pale and yellow all over. When at length it is getting ripe
for hatching, it is subject to differentiation of substance, and the
yolk gathers together within and the white settles round it on the
outside. When the full time is come, the egg detaches itself and
protrudes, changing from soft to hard with such temporal exactitude
that, whereas it is not hard during the process of protrusion, it
hardens immediately after the process is completed: that is if there
be no concomitant pathological circumstances. Cases have occurred
where substances resembling the egg at a critical point of its
growth-that is, when it is yellow all over, as the yolk is
subsequently-have been found in the cock when cut open, underneath his
midriff, just where the hen has her eggs; and these are entirely
yellow in appearance and of the same size as ordinary eggs. Such
phenomena are regarded as unnatural and portentous.