I02 A GUIDE FOR THE STUDY OF ANIMALS 



are of two kinds : those composed of bone and those com- 

 posed of cartilage. 



Lateral line, a sense organ extending along each side of 

 the fish in a line indicated by tubes or perforations in the 

 scales. 



Gills, respiratory organs adapted for taking oxygen from 

 the water. 



Operculum, the flaps covering the gills on each side of 

 the head. 



Pigment, a substance which gives color to an object. 



Observations. 



Locomotion, i. Watch the fishes in the large aquarium 

 and determine which fins are most used and how they are 

 used {a) in swimming forward, {b) in swimming upward 

 and downward, {c) in maintaining balance, {d) in remain- 

 ing at rest, and {e) in guiding the movements of the fish. 



2. What advantages are there to the fish (a) in the power 

 to open and close the dorsal and anal fins, (3) in having no 

 neck, and (c) in having a compressed form .? 



3. Enumerate the various ways by which the body of 

 the. fish is adapted to rapid movement through the water. 



Feeding. 4. What is the food of the fishes you are 

 studying .'' Feed them and watch them eat. Why is the 

 upper jaw often called a " hp " } What is the shape and 

 size of the mouth when opened in feeding .-' Does the fish 

 chew its food } Describe in detail the fishes' method of 

 feeding. 



Respiration. 5. Identify the opercula and the gill open- 

 ings. Watch the movements of the opercula and mouth, 

 and determine what movements are concerned in breathing 

 and their order. Describe in detail the circulation of water 

 used in breathing and how it is caused. 



