9. Point out the chief differences between the wing of a bird and that of a bat.
10. Explain how the barbs of a quill feather are attached to one another. Describe a feather at the time when it is forcing its way through the skin. (1905)
11. What peculiarities distinguish feathers which aid in flight from feathers which merely prevent loss of heat? (1906)
12. Describe the wing of a bird, both as to skeleton and as to external appearance. Compare the skeletal parts with those of the corresponding structures in a Mammal. (1908)
CHAPTER XVI.
THE DEVELOPMENT AND EDUCATION OF THE CHICK.
52. A HEN’S EGG.
Obtain three or four hen’s-eggs, and make the following observations upon them:
1. External appearance.—What is the colour of the egg? What is its shape? How does the shape differ from that of a cricket ball or other sphere? The shape of an egg is said to be ovoid. [What is the difference between an ovoid and an oval?] Measure, with a tape, the length and breadth of the egg, and also its distance round, (i) in the direction of its greatest length, (ii) in the direction of its greatest width. What advantages has this shape? Could a hen sit so comfortably upon her eggs if they had sharp corners? Put an egg upon the table and roll it gently. Does it roll in a straight line? Does it roll far before coming to rest? Compare the rolling of a cricket ball or other sphere. Is it an advantage that an egg is not likely to roll far, or in a straight line? Why?