How To Study Living Animals

Review and Library Exercise on Cœlenterates

1. What are the characteristics which distinguish cœlenterates herunterladen?

2. Give the classes of cœlenterates, with the characteristics and an example of each.

3. What enables a hydra to stick to a support by its foot herunterladen?

4. What are the processes in a hydra by which food is captured, swallowed, and digested?

5. What is the chief fact of interest about Hydra viridis microsoft office kostenlos downloaden vollversion deutsch chip?

6. Why do hydras reproduce all summer by budding and in the late fall by eggs?

7. What change would have developed a hydra and its offspring into a plant-like colony instead of into a group of individuals?

8. Why are ctenophores more easily seen in the night than other cœlenterates are?

9. What relations may exist between hydroids and hydro-medusæ?

10. What are the advantages of a sedentary life? Of a locomotory one?

11. What is meant by the expression “alternation of generations”? Which animals are likely to develop alternation of generations, sedentary ones or locomotory ones? Why?

12. Give at least two differences between hydro-medusæ and true jellyfishes.

13. In the association between a hydractinia colony and a hermit crab, what advantages are derived by the hydractinia? by the crab? Define symbiosis. Give another illustration of it.

14. How are new coral colonies started? How are large colonies formed?

15. What are the conditions of life under which corals can grow vigorously?

16. Where are corals most abundant?

Note.—Show by coloring the regions on a blank map of the world.

17. How may corals form a reef? Why do they, as a rule, form a reef instead of adding directly to the mainland?

18. Give Darwin’s theory regarding the way a coral atoll may have been formed.

19. Where are fossil corals found in abundance? What does their presence prove?

20. What is polymorphism? Give an illustration. What may be a disadvantage of polymorphism? What may be an advantage?

21. In what ways is this group of economic importance?


To show cells associated even more closely than in cœlenterates, forming tissues and systems of organs.

A Study of Earthworms