CLIMAX OF THE ANIMAL KINGDOM— PHYLUM CHORDATA 307 



Subphylum III. Cephalochorda (Gr. kephale, head; chorde, cord; the 

 notochord extends forward into the head). Example, Amphioxus. 



Subphylum IV. Vertebrata (L. vertebratus, jointed; refers to the 

 jointed condition of the vertebrae). Example, frog. 



REVIEW QUESTIONS 



1. Tell how the chordate nerve cord gets its tubular shape in embryonic de- 

 velopment. 



2. What is a notochord and where is it found? 



3. Why do we say that a post-anal tail is a chordate characteristic when there 

 are important members of this phylum, such as man, that do not have a tail? 



4. Why is a study of the embryo of great importance in the classification of the 

 chordates ? 



5._ Compare the chordates with higher invertebrates with respect to blood 

 circulation. 



6. Why are the sea squirts placed in the chordates? 



7. In what ways is Amphioxus like a true vertebrate ? 



8. What fundamental difference is there between Amphioxus and a true verte- 

 brate ? 



9. Compare the structure and position of skeletons in vertebrates and inverte- 

 brates. 



10. Name some vertebrates with well developed exoskeletons. 



11. Why is the term Vertebrata almost synonymous with Chordata? 



