COMPARISONS. 



With columns for Sea-urchin and for Starfish, answer 

 the following questions: 



(1) Of what is the skeleton composed? 



(2) Are spines present upon the outside of the body? 



(3) Can you speak of the parts as being radiately ar- 

 ranged? 



(4) Can you also speak of them as bilateral? 



(5) Do you find in both ampullae and ambulacra? 



(6) Does the nervous system surround the mouth? 



(7) Is there a body-cavity? 



(8) Is there a madreporite and a stone-canal? 



(9) Do you find radial canals? 



Read the whole section on Echinoderma (pp. 273 to 285). 



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