64 A GUIDE FOR THE STUDY OF ANIMALS 



particular time rather tlian at another ? Why does " the early bird 

 catch the worm " ? 



g. What enemies do earthworms have ? How are they protected 

 against these enemies ? 



10. If you have found egg capsules when collecting worms, describe 

 them. 



External Morphology of Earthworms 



Materiak. 



Preserved earthworms, the larger the better. 



Observations. 



1. In what respects are the dorsal and ventral surfaces 

 alike .' In what respects different .'' Why ? 



2. Why are the right and left sides alike } 



3. In what respects are the two ends alike .-' In what 

 different .? Why > 



4. How many somites are there from the anterior end to 

 the girdle .'' How many under the girdle .' How many 

 from the girdle to the posterior end .■' 



5. Where are the setse located in a somite .' How are 

 they distributed over the body .■' 



Suggested drawings. 



a. An earthworm, dorsal aspect. 



b. An earthworm, ventral aspect. 



c. An outline diagram of a cross section, to show the lo- 



cation of the setae, the blood vessels and the alimen- 

 tary canal. 



Internal Morphology or Anatomy 



Materials. 



(i) Preserved earthworms, as large as you can obtain. 

 (2) Cross sections of earthworms. (3) Longitudinal sec- 

 tions of earthworms. 



