1. How large is an individual specimen in the form you are studying? If the form is colonial, how large is the colony or portion of a colony you are studying? Estimate the number of individuals in it. Is the colony free-swimming or attached? If attached, to what is it usually fastened? 2. Compare the individual you are studying with a hydra, as to size and shape of the body, the location of the mouth, and the size, number, and arrangement of the tentacles. 3. Is there a skeleton? If so, describe it. What appears to be its use? In corals, notice the radiating partitions. 4. Has the specimen any nettle cells? If so, where are they located? 5. Are all the polyps of the colony alike? If not, how many kinds are there? How do they differ? What is each kind best fitted to do? What is the probable result of this differentiation? 6. What kinds of reproduction, if any, does the specimen you are studying show? Find out from books what other forms of reproduction are sometimes used by this animal. _Suggested drawings._ a. At least one drawing of each cœlenterate you study. Summary of the Comparative Study of Cœlenterates 1. How may polyps in colonial forms differ from polyps which live singly? 2. What variations in methods of reproduction are shown in this group? 3. Which of the polyps you have studied shows the greatest differentiation? In what ways? 4. What characteristic do you find common to all the cœlenterates you have studied? Review and Library Exercise on Cœlenterates 1. What are the characteristics which distinguish cœlenterates? 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? 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? 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?