2 
STRUCTURE OF THE EGG. 
another office, which is not possessed by hair or fur. They aid the creature in progression, 
and enable it to raise and to sustain itself in the atmosphere. Towards the promotion of this 
latter function the entire structure of the body and limbs is obviously subservient, and even in 
the comparatively rare instances where the bird— such as the penguin, ostrich, or the kiwi- 
kiwi— is destitute of flying powers, the general idea of a flying creature is still preserved. 
The fuller and more technical description of the Birds runs as follows. They are vertebrate 
animals, but do not suckle their young, nourishing them in most instances with food which 
lias been partially macerated in their own digestive organs, and which they are able to disgorge 
at will, after a manner somewhat similar to that of the ruminating quadrupeds. The young 
aie not pioduced in an actively animated state, but inclosed in the egg, from which they do 
not emerge until they have been warmed into independent life by the effects of constant 
warmth. Generally, the eggs are hatched by means of the natural warmth which proceeds 
from the mother bird ; but in some instances, such as that of the tallegalla of Australia, the 
eggs are placed in a vast heap of dead leaves and grass, and developed by means of the heat 
which is exhaled from decaying vegetable substances, and which is generated to such an 
extent that in some cases, such as a wet haystack, it actually sets the seething mass on tire. 
Urged by a like instinct, the common -species of snake deposits its eggs in secret spots, such as 
dunghills and hotbeds, and there leaves them to be hatched by the constantly generated warmth. 
An analogous process has long been in vogue among the Egyptians for the hatching of young 
poultry by artificial heat, and has been, in comparatively recent years, introduced into this 
• country. 
When the egg is first produced, the future chicken is merely indicated by a little germ- 
spot, barely the size of a single oat-grain, and does not attain the power of breathing atmos- 
pheric air, and receiving nourishment into its mouth, until a period of many days has elapsed. 
To watch the gradual development of the young chick is a most interesting experiment, and one 
which is full of suggestive instruction, There is but little difficulty in the matter, even in the very 
earliest stages of incubation, for the structure of the egg is so wonderfully balanced, that in 
order to view the little germ-spot it is only necessary to lay the egg on its side and remove 
a portion of the shell, when the germ will be seen lying immediately under the aperture. In 
whatever way an egg may be turned, the germ-spot invariably presents itself at the highest 
point, provided only that the egg be laid on its side, and that the living principle has not been 
extinguished, for life, however undeveloped, seems always to aspire. As the chick increases 
in size, the manipulation becomes easier, but it is always better to immerse the egg in water or 
other transparent liquid before removing the shell, and to keep it submerged during exam- 
ination. 
There are few objects which will better repay investigation than the young bird in its 
various stages of development. It is wonderful to see the manner in which a living creature 
is gradually evolved from the apparently lifeless substances that are contained within an egg. 
The being seems to grow under our very gaze, and we arise from the wondrous spectacle with 
an involuntary feeling that we have been present at a veritable act of creation. To describe 
fully the beautiful process in which a chick is elaborated out of the germ-spot would occupy 
very many pages, and cannot be attempted within the compass of the present work. Briefly, 
however, the order of events is as follows : 
When a newly laid egg is opened, it is found to contain a mass of substance which is 
popularly divided simply into “ white” and “yolk,” but when examined more closely, by 
placing it under water and carefully removing the shell, its contents are found to be very 
elaborately disposed, so as to meet the object for which it was formed. Immediately within 
the shell lies a semi-transparent and tolerably strong membrane, composed of two distinct 
layers, pressed closely to each other for the greater portion of its extent, but separated at the 
widest end of the egg, and containing between the layers a supply of atmospheric air to satisfy 
the requirements of the young chick. This space gradually increases as the young bird 
becomes more developed. Within this membrane lies the “white,” a liquid albuminous sub- 
stance, which is also disposed in two distinct layers, that which is nearest to the shell being 
rather thin and fluid, while the inner layer is comparatively thick, tenacious, and very 
