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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. 13), 
formed of a delicate transparent membrane called the vitelline 
membrane, and about ;4, to ~4;th 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, hes a more 
solid rounded body, termed the ‘ germinal spot’ (0d). 
Fic. 18.—A. Egg of the Dog, with the vitelline membrane burst, so as to give 
exit to the yelk, the germinal vesicle (@), and its included 
spot (0). 
B.C. D. E. F. Successive changes of the yelk indicated in the text. 
After Bischoff. 
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 main- 
tenance during the protracted process of gestation. Here, 
