Young birds begin their development within an eggshell. The young chick lives three weeks in the shell before it sees the light of day. If we study an egg that has not been incubated, opening the shell carefully on the upper side, we find upon the surface of the yolk a little circle somewhat smaller than the end of a lead pencil. This circle is the germ. The germ of an egg in this condition is nothing more or less than the young chick asleep. The warmth of the maternal body or of the incubator is all that is necessary to awake this sleeping organism and start its life processes. As soon as it wakes up and begins its development, it builds its body step by step, using the materials provided for this building by the maternal organism. These materials consist of proteins, fats, and salts. From the egg albumen, the egg oil and the egg salts the body of the chick is developed to the condition with which we are all familiar as it leaves the shell when it is hatched. Such a chick possesses all the kinds of tissue which it will ever possess. It has a bony skeleton; it has muscles, glands, and nervous system; it has connective tissue and rudimentary feathers. It possesses special sense organs, and all of these organs and tissues are able to perform their normal functions. The process of growth and repair and of active work have already been thoroughly established, yet the bird has to the date of its hatching received no other food than that contained within the egg at the time incubation began.