257 



QUESTIONS ON THE CCELENTERATA. 



1. By what structural features are Coel en terata separated from other 



primaiy divisions of the animal kingdom ? 



2. Contrast the two sub-kingdoms, Protozoa and Ccelenterata. 



3. Describe the typical structure of a thread-cell. 



4. Compare the classes, Hydrozoa and Actinozoa. 



5. Describe the structure of Hydra. How does the ' poly pi te ' of 



this genus differ from that of the non-budding forms of the 

 Corynidse ? 



6. Define the terms, 



a. ' hydrotheca ' ; 



b. ' hydrophjdlium ' ; 



c. 'hydrocyst.' 



7. In what order of Hydrozoa do ' nematophores ' occur ? Describe 



the structure and position of these appendages. 



8. Describe the structure of a ' nectocalyx.' How does this organ 



differ from an ' umbrella ' ? 



9. Describe the structure and relations of the nectocalyces in 



Diphyes, and state how the same parts are modified in 

 Praya, 



10. In what Physophoridse are nectocalyces absent? 



11. Briefly describe the modifications of the cceuosarc, and relative 



attachment of its appendages, in the following genera of 

 Physophoridse : 



a. Physophora; 



b. Stephanomia; 



c. Apolemia; 



d. Athorybia; 



e. Velella. 



