5. Snake charming.

6. Famous poisonous snakes and their habits.

7. The characteristics and habits of alligators.

8. The characteristics and habits of marine turtles. How they differ from pond turtles.

9. For what is each of the following noted? Where does it live? The terrapins? the horned toad? the Gila monster? the chameleon? the gla.s.s snake?

10. Reptiles of former (geological) times compared with those of the present.

11. Care of eggs and young. Swallowing of young by snakes.

12. Food of snakes. Defend the proposition that non-poisonous snakes are beneficial and should not be killed wantonly.

13. Investigate and write an account of the economic value of reptiles.

#D. STUDIES OF BIRDS#

#Vertebrates specialized for Flight#

The Living Pigeon

_Materials._

Living pigeons in cages, and, if practicable, other birds such as chickens, canaries, and sparrows.

_The Body._

1. What divisions of the body are present? Compare the relative size of these divisions with that of other vertebrates studied. Can you account for the great increase in bulk of the trunk over the other divisions? How do you account for the longer neck?

_Flight._

2. What is the shape of the body? How is the body made smooth? To what is the shape and smoothness adapted? (Recall the appearance of a plucked pigeon or chicken.)

3. Observe the size of the wings by measuring their width and spread (measured from tip to tip when outspread). Where on the body are they attached? How is this point of attachment advantageous? What is the shape of the upper surface of a wing when spread? of the lower surface? How is this shape advantageous in flight?

4. Where are the largest and strongest feathers? How are they arranged with respect to each other: (a) to prevent air pa.s.sing through on the down stroke of the wing? (b) to permit folding?

5. What is the shape and width of the tail when outspread? when folded? In what way does the tail a.s.sist in flight?

_Walking and Perching._

6. Identify the parts of the leg as in the frog. (See study of frog.) With what exoskeletal structures is each part covered? How many toes are there? Does the pigeon walk on its foot or on its toes? Where is the ankle joint?

7. The bird's legs are arranged to support the body. How is this brought about? Compare with the lizard and frog in this respect.

8. Explain how the legs are adapted (a) to preserve the balance of the body, and (b) for perching. Are they well or poorly adapted for locomotion? Explain. For what other purposes are the legs sometimes used?

_Feeding and Drinking._

9. What is the form and character of the jaws of the pigeon (called the beak)? Offer food, and watch the pigeons eat. How does a pigeon seize and swallow food? Does it chew the food? Locate the crop. If the pigeon chewed its food, would it have a crop? Why? How does a pigeon drink? How does the chicken drink?

_Respiration._

10. What parts move in breathing?

11. Compare roughly the body temperature (by touch) of man, the pigeon, and the frog. Which has the highest temperature? which the lowest? How can you account for the higher temperature of the bird?

(Which of the three must be able to endure long-sustained effort?

What is the effect on your own body of long-continued effort?)

_Sense Organs._

12. Identify the eyes, ears, and nostrils, and describe their location. What are the advantages in having the eardrum at the bottom of a ca.n.a.l? Is there any disadvantage? What is the probable function of the inner thin eyelid? How does it work?

13. Investigate the power of response of the special senses. Which seems to be the most alert? State the experiments which you used and your reasons for your answers to this question. Which senses are most serviceable in finding food? in protecting against enemies?

_Protection._

14. In what different ways are feathers protective to the bird? Study the arrangement of the feathers to find how protection is increased in this way. How do the feathers and parts of feathers which lie next the body differ from those which are on the outer surface? What parts of the body are unprotected by feathers? How are these protected, if at all?

15. Note the flexibility of the neck. Through what part of the arc of a circle can the pigeon turn its head? How is this especially important to birds?

16. What means of defense has the pigeon when attacked?

_Summary._

1. Make a list of the important adaptations of the pigeon, (a) to flight, (b) to feeding, (c) to perching, and (d) to protection.

2. Which is the most highly specialized, the fish, frog, snake, or bird? Give reasons for your answers.

3. In what various ways are feathers of use to the bird?

_Suggested drawings._

a. Side view of the head.

b. A foot.

c. A wing.

d. Side view of the pigeon.