VERTEBRATES 103 



Sense Organs. 6. Identify the eyes, nostrils, and lat- 

 eral line. How many nostrils are there and where located ? 

 What is the position and extent of the lateral line ? 



7. Describe the location of the eyes. What is the shape 

 of the outer surface of the eyes ? Why this shape ? Can 

 the eyes be moved, i.e. can they be rotated, rolled, or re- 

 tracted .' From what direction might an enemy approach 

 without being seen ? How would such an enemy be de- 

 tected .'' 



Protection. 8. With what protective structures is the 

 body covered .■' Do they hinder the movements of the fish .■• 

 What are the advantages of the scale covering of fishes 

 over the shell covering of grasshoppers or crayfishes ? 



9. In what other ways are the fishes you are study- 

 ing protected against enemies 1 Since you cannot account 

 for the red color of goldfishes on the basis of use to the 

 fish, then how do you account for this bright color .'' 



The Body. 10. What is the symmetry of the fish .' Into 

 what regions is the body divided .'' 



Summary of the study of the living fish. 



Enumerate in one column .the different adaptations 

 which fit the fish for life in water and in a second column 

 state the special purpose of each adaption. 



The External Structure of the Fish 

 Materiab. 



Freshly killed or preserved fish in dishes or shallow 

 pans with enough water to prevent drying. Simple or 

 compound microscopes, forceps, and a bristle. 



Directions. 



Examine the fins and identify the membrane and the 

 supporting rods, or rays, of bone or cartilage. Notice 



