Page:First course in biology (IA firstcourseinbio00bailrich).pdf/377

 consists of an upper portion, the carapace, and a lower portion, the plastron. How are the other regions covered? What is the shape of the head? Is the mouth at the front, or on the under side? Where are the nostrils? Are the motions of breathing visible? Is there a beak or snout? Do the jaws contain teeth?

Do the eyes project? Which is thinner and more movable, the upper or lower lid? Identify the third eyelid (nictitating membrane). It is translucent and comes from, and is drawn into, the inner corner of the eye. It cleanses the eyeball. Frogs and birds have a similar membrane. The circular ear drum is in a depression back of the angle of the mouth. What other animal studied has an external ear drum?

The tortoise has a longer, more flexible neck than any other reptile. Why does it have the greatest need for such a neck? Is the skin over the neck tight or loose? Why?

Do the legs have the three joints or parts found on the limbs of most vertebrates? How is the skin of the legs covered? Do the toes have claws? Compare the front and hind feet. Does the tortoise slide its body or lift it when walking on hard ground? Lay the animal on its back on a chair or table at one side of the room in view of the class. Watch its attempts to right itself. Are the motions suited to accomplish the object? Does the tortoise succeed?

What are the prevailing colors of turtles? How does their coloration correspond to their surroundings?

What parts of the tortoise extend at times beyond the shell? Are any of these parts visible when the shell is closed? What movements of the shell take place as it is closed? Is the carapace rigid throughout? Is the plastron?