PHYLUM ARTHROPODA 325 



of many soft-bodied animals otherwise unknown from that ancient 

 period. Aysheaia appears to have been a marine, peripatus-like animal. 

 If this current view proves correct, then although the Onycophora 

 share characteristics with both the annelids and the arthropods, and are 

 often intermediate structurally, they would not be considered an evolu- 

 tionary link but a third surviving branch of an ancient and possibly 

 much diversified group of segmented organisms. 



Questions 



1. Compare diagrammatic body segments of an arthropod and a polychaete annelid. 



2. Which Hmbs put food into the mouth in each of the four arthropod subphyla? 



3. When did each of the subphyla develop terrestrial forms? 



4. Describe the nauplius larva. 



5. W'hat is a pleopod? 



6. List the sense organs of a crayfish and give their locations. 



7. Describe what happens to food from the time it is captured until its nutrients are 

 absorbed in the crayfish. 



8. Compare the circulatory systems of arthropods and annelids. 



9. What are the locomotor organs of Daphnia? 



10. Contrast centipedes, millipedes and insects. 



11. W'hat is a pulvillus? 



12. Compare the excretory systems of Cambarus and Periplaneta. 



13. What is the functional significance of the characteristic that separates the Neoptera 

 from the Paleoptera? 



14. Describe complete metamorphosis. 



15. What is a pollen basket? 



16. Give the life cycle of the honeybee. 



17. What animal has two respiratory systems? 



18. Discuss the relation of the Onycophora to the arthropods. 



Supplementary Reading 



Insect Natural History by Imms is a readable account by one of our foremost ento- 

 mologists. 1 he paperbound Maeterlinck, The Life of the Bee, and Crompton, The Life 

 of the Spider, are excellent life studies. Of the many manuals for insect identification, the 

 paperbound Insects by Zim and Cottam is adequate for the beginner, containing pictures 

 of many common species. 



