ECHINODERMATA 221 



3. Construct a table of parallel columns one for each of 

 the five living classes and contrast them as to: (i) general 

 form of body including symmetry, (2) manner of motion, (3) 

 position of mouth and anus, (4) position of madreporic body, (5) 

 character of digestive tract, (6) differences in the spines and other 

 skeletal structures, (7) the position and character of the ambu- 

 lacral feet, (8) habitat and food, (9) parts repeated in the anti- 

 meres. 



4. Report on the habits, appearance, and abundance of 

 crinoids in geological time. 



5 . The origin and development of the water- vascular system. 



6. Compare the figures of the various classes as illustrated 

 in your reference texts and mark the degree of variation. 



