MOLLUSC A — CEPHALOPODS 259 



parallel to plane of coiling. Label aperture, living chamber, 

 septa, siphuncle, muscle scars. 



3. How are the septa secreted ? Give a probable theory as 

 to the cause of their presence and equal spacing. 



4. What was the function of the muscles which caused the 

 scars upon the inside of the shell ? 



5. Describe the siphon ; its relation to the siphuncle. 



6. How does Nautilus creep? While creeping what is the 

 position of the funnel ? the coil of the shell ? How does it 

 differ in this respect from a gastropod like Helix ? 



7. What are the functions of the tentacles? What is the 

 hood ? its function ? 



8. Describe the hyponome; its function. How is its 

 presence indicated upon the shell ? 



9. What portion of the body secretes the shell? the 

 siphuncle ? 



10. What organs are located in the mantle cavity ? 



11. How does the animal breathe? 



12. Name two modes of progression of the animal. 



13. What is its food ? How caught and eaten ? 



14. Briefly describe the circulation of the blood. 



15. What waste products are there and how are these thrown 

 out of the body ? 



16. What are the principal differences between the nervous 

 systems of the cephalopod Nautilus and the gastropod Busy- 

 con? 



17. Describe the eye of Nautilus ; the otocyst. 



18. Are the sexes united or separate? 



19. What are sutures ? Examine them upon a fossil Nautilus. 



20. What is the direct cause of the coiling during the growth 

 of the shell ? 



21. What part of the mantle secretes the "mother-of-pearl" 

 of the shell ? What is the cause of its brilliant luster ? 



22. Label on the sketch 2, (c) the dorsal and the ventral por- 

 tions of the shell. How does it differ in this respect from gas- 

 tropods, e.g. Busycon and Helix ? 



General Survey of Class Cephalopoda 



Cephalopods are bilaterally symmetrical mollusks, with the 

 foot transformed into a crown of appendages surrounding the 



