_Questions._

1. Briefly describe the exoskeleton, if there is one.

2. What region or regions are clearly segmented?

3. How much of the body is covered by a carapace?

4. Has it segmented appendages? Cla.s.sify the appendages as to their use.

5. Are the cephalo-thorax and abdomen equally developed? If not, which is more developed?

6. How many antennae has it? Are the eyes stalked, or are they sessile?

7. What organs of respiration has it? Where are they attached?

8. How many thoracic appendages has it, if any?

9. What methods of locomotion does it use?

_Summary._

1. Does this animal seem to be adapted to life on land or in water, or both? Give your reasons for your opinion.

2. What characteristics are common to all the crustacea you have studied?

3. REVIEW AND LIBRARY WORK ON CRUSTACEA

1. What are arthropods?

2. Give the cla.s.ses of arthropods with an example of each.

3. What are the distinguishing characteristics of the cla.s.s crustacea?

4. In what respects are most of the appendages of the crayfish h.o.m.ologous, _i.e._ alike in the plan of structure? Which do you consider the simplest, and why do you? Which do you consider the most specialized, and why?

5. Which somite of the crayfish is without appendages? How many somites are there in a crayfish's body, if each somite bears only one pair of appendages, as many scientists believe? How many of these are in the head; thorax; abdomen?

6. Compare the nervous system of the crayfish with that of the earthworm as regards efficiency. Upon what do you base your answer?

7. Name two points in which earthworms and crayfishes are alike. Name three in which they differ.

8. How are crayfishes caught for market? Where do those sold in Chicago usually come from? How are they shipped?

9. Compare the young forms of a crayfish and a crab.

10. Describe any five different crustacea.

11. Describe the work done by the United States government and by the state governments to protect and to perpetuate the lobster. Why is it thought necessary to do this?

12. Discuss the process and the advantages and disadvantages of molting, as seen in the crustacea.

13. Name two advantages in having such a sh.e.l.l as crustacea have.

Name two disadvantages. On the whole, is such a sh.e.l.l favorable to an animal's chances of success or is it not?

14. Give the curious myth about goose barnacles.

15. What crustacea are parasitic? Give an account of one.

16. Why are barnacles cla.s.sed among crustacea? Where were they once cla.s.sed? Why may they be considered degenerate, even though not parasitic? How do they manage to succeed? What is their economic importance? How are their effects checked or prevented?

17. Describe some of the odd means of self-protection shown among crustacea.

18. Describe a compound eye. Give two theories as to what can be seen with a compound eye. Why do we not know, instead of theorizing?

19. What is the economic value of the very small crustacea?

20. Discuss the value to man of the various forms of crustacea.

CHAPTER V

ADAPTATIONS FOR PROTECTION FROM ENEMIES

#A. THE EXOSKELETON#

1. THE CLAM--A TYPE OF MOLLUSCA

_To Show the Effect of a Heavy Exoskeleton_

_Materials._

Living clams in aquaria, with enough moist sand to cover the clams, preserved clams, sets of matched clamsh.e.l.ls, a few sh.e.l.ls with the hinge unbroken, evaporating dishes, hydrochloric acid.

_Definitions._

_Mollusca_, a branch of the animal kingdom including those animals with soft, unsegmented bodies, inclosed in two folds of skin known as the mantle. They are often called sh.e.l.lfish as most of the forms have a sh.e.l.l.

_Lamellibranchiata_ or _Pelecypoda_, names given to the cla.s.s of Mollusca to which the clam belongs. The former term refers to the broad, flap-like gills and the latter to the hatchet-like foot.

_Valve_, one of two parts of the clamsh.e.l.l.