34 STUDIES OF ANIMAL LIFE. 



5. Make a diagrammatic drawing of a cross-section of 



the earthworm (4 cm.). 



6. Make a similar drawing to illustrate H 4. 



7. Make a drawing to illustrate H 5. 



8. Make a drawing to illustrate H 6. 



9. Make a diagram of the circulatory system. 



Li, Sugg-estive Questions. 



1. Why cannot earthworms survive drying '? 



2. What becomes of earthworms in dry weather ? 



3. What becomes of them in winter ? 



4. How do earthworms enrich the soil ? 



5. Do they injure plants or animals ? 



6. What is the earthworm's protection from its ene- 



mies? 



7. Where are the new somites added as the earthworm 



grows ? (Compare on three worms the number 

 of somites anterior to the girdle with those pos- 

 terior to it.) 



8. If an earthworm were obliged to live in water, what 



modifications in its make-up would be necessary ? 



9. Why is the elongated type of body of the earthworm 



better adapted to differentiation and higher or- 

 ganization than the radiate type of the Hydra ? 

 10. What advantage is there in the double-tube plan of 

 body of the earthworm over the single-tube plan 

 of the Hydra ? 



3. A MARINE ANNELID "WORM. 

 A. The Body. 



1. Identify the anterior and posterior ends. 



2. How can you tell the ventral surface from the dorsal 



surface ? 



