ECHINODERMATA. 215 



(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 ambulacral feet, (8) habitat and food, (9) 

 parts repeated in the antimeres. 



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. 



7. What evidences can you find for the statement that the 

 ancestors of the present Echinoderms may have been bilateral 

 forms ? 



