The Dog, like all animals, save the very lowest (and further inquiries
may not improbably remove the apparent exception), commences its
existence as an egg: as a body which is, in every sense, as much an egg
as that of a hen, but is devoid of that accumulation of nutritive
matter which confers upon the bird's egg its exceptional size and
domestic utility; and wants the shell, which would not only be useless
to an animal incubated within the body of its parent, but would cut it
off from access to the source of that nutriment which the young
creature requires, but which the minute egg of the mammal does not
contain within itself.
The Dog's egg is, in fact, a little spheroidal bag (Fig. 12), formed of
a delicate transparent membrane called the 'vitelline membrane', and
about 1/130 to 1/120th of an inch in diameter. It contains a mass of
viscid nutritive matter--the 'yelk'--within which is inclosed a second
much more delicate spheroidal bag, called the 'germinal vesicle' (a).
In this, lastly, lies a more solid rounded body, termed the 'germinal
spot' (b).
The egg, or 'Ovum,' is originally formed within a gland, from which, in
due season, it becomes detached, and passes into the living chamber
fitted for its protection and maintenance during the protracted process
of gestation.
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