64 
BIBD-LIFE. 
view of investigating its structure ; so we will avail our¬ 
selves of the one easiest obtained and best known, that of 
the domestic fowl. Let us try, first of all, however, to 
explain clearly its origin. 
As is well known, the vivification of a germ is caused 
by the most intimate connexion of the two sexes, this 
germ having remained for a long time previous in a 
normal condition. After this vivification has taken place, 
one of the almost countless little globules contained in 
the ovary separates itself from among the rest, and 
gradually grows to the size of the future yolk. In the 
meantime it has absorbed from the blood all those mate¬ 
rials which form the yolk, or has itself become the yolk 
of the future egg. The yolk having arrived at its full 
growth, the membrane, in which it is enveloped and by 
which it has hitherto remained attached to the ovary, 
breaks away and forms at once the covering of the 
spherical body, which is composed principally of casein, 
sulphur, iron, lime, and fatty matter. It now falls 
into the oviduct, the coats of which exude the white, 
or albuminous portion of the egg; and winds slowly 
through the same. At the same time the white secreted 
(a compound of fat, grape-sugar, common salt, phosphoric 
acid and earths) next attaches itself closely to the 
revolving sphere; and thus arise the so-called “ chalazse” 
between which, at the point of separation of the yolk 
from the ovary, the germ lies. In the lower portion 
of the oviduct other deposits are secreted, differing in 
character from those in the upper portion, which form 
two leather-like membranes lying closely one over the 
other, excepting at the blunt end of the egg, where 
they are separated by an air-cell; over these, again, 
is deposited the last secretion of the duct, a chalky 
