THE LOWER VERTEBRATA. 211 



15. Describe the auditory organ of the dogfish. What 

 parts are added to this in the higher types ? 



16. (a) Give an account, with diagrams, of the brain of 

 the frog; () point out the most important differences 

 between it and the brain of the rabbit, (c) Describe the 

 superficial origin and the distribution of the third, (c?) of 

 the fifth, (e) of the seventh, (/) of the ninth, and (g) of the 

 tenth cranial nerves of the frog. 



17. Draw diagrams, with the parts named, of the ali- 

 mentary canal of (a) Amphioxus, (i) any Craniate ; (0) in- 

 dicate very shortly the principal structural differences 

 between the two. 



18. Describe, with a diagram, the circulation of Amphi- 

 oxus. Compare it with that of the Craniata. 



19. Compare the skull of the dog and the frog; especi- 

 ally in regard to the attachment of the jaw apparatus to 

 the cranium, and other points which distinctly characterize 

 the higher as contrasted with the lower Vertebrata. 



20. Describe the skeleton of the upper and lower jaw (a) 

 in the frog, (b) in the dog. Point out exactly what parts 

 corresponds with one another in the two animals compared, 

 (c) What bone in the dog is generally regarded as corre- 

 sponding to the quadrate cartilage of the frog ? 



21. Give an account of the limb skeleton of Scyllium, 

 Rana, and Lepus. 



22. Describe a transverse section across the pharyngeal 

 region of Amphioxus. 



23. Describe, with the aid of diagrams, the skull and 

 visceral arches of the dogfish. What are the essential 

 features of difference shown in the skull of the adult frog ? 



24. Describe and compare the aortic-arch system in 

 Lepus, Rana, and Scyllium. 



25. What are the leading characters in which Amphioxus 

 resembles and differs from Scyllium ? 



26. Give an account of the vertebral columns of Lopus 

 and Scyllium, pointing out in what respects the two re- 

 semble and differ from each other. 



