The chief organs of the bird are now established, and the later development may be sketched more briefly. By the end of the ninth day (Fig. 193) the white of the egg is almost used up; the yolk, however, is still large, and is connected with the chick’s body by the narrow yolk-stalk. It thus appears that the white is not directly absorbed by the chick, but is first taken up by the yolk and afterwards passed on by the yolk blood-vessels which run to the heart. By this time, too, the allantois has spread at least halfway round the inside of the shell, that a supply of oxygen adequate to the increased needs of the animal may be obtained from the air. The chick has now a characteristic bird-like appearance; the beak has appeared; feathers have begun to sprout; the neck is long and slender; and the segments of the limbs, including the fingers and toes, are well defined. About the fourteenth day the chick turns so as to lie lengthwise in the shell, with its head near the broad end. The yolk-sac dwindles in size, and at last, about the twentieth day, it is drawn into the interior of the body. Now the chick becomes restless, and—usually on the twenty-first day—thrusts its beak through the inner shell-membrane into the air-chamber at the broad end of the egg. For the first time it draws refreshing air into its lungs, and is stimulated to break the shell by a knob on its beak, and to creep out into the world. [Pg 295] 54. THE EDUCATION AND LATER GROWTH OF THE CHICK.[18] 1. Hatching.—On the 20th or 21st day of incubation remove three or four eggs from the clutch under the hen, and keep them in a warm cosy place so that you may watch the process of hatching. Can you hear the chick tapping the inside of the shell? Could it have been taught to tap? Which part of the shell cracks first? When the shell has cracked, can you hear the chick chirping? Could it have been taught to chirp? Imitate the chirp and listen for a response. Keep the newly-hatched chicks in a warm, soft place. How soon do they recover from the exhaustion of hatching? Do the chicks show a liking for warm corners? Are they afraid of being touched gently? 2. Locomotion.—How soon do the chicks begin to run about? Do they stumble upon obstacles, or do they avoid or leap over them? Do they use their wings in running, or in jumping down a small step? Put a chick into a basket, and lower the basket quickly through the air, being careful not to let the chick fall out. Does it move its wings? How?