VERTEBRATES 107 



8. What is the direction of the water current through 

 the gill chamber ? Of what use are the gill rakers ? 



9. How are the gills protected ? 



Summary. 



Write a complete account of how the fish eats and how 

 it breathes. 

 Suggested drawings. 



a. A front view of the fish's face, with the mouth fully 

 open. 



6. A side view, as above. 



c. A ventral view of the head, with both gill-chambers 

 wide open and the gills separated from each other. Indi- 

 cate currents by arrows. 



d. A single gill. 



The Alimentary Canal and the Circulatory System of the Fish 

 Materials. 



Small fresh fish, shallow pans or dishes of water, forceps, 

 and scissors. 

 Directions. 



If the instructor has not opened the fish previously, this 

 is to be done by the student as follows : On the ventral 

 side, insert the scissors in the vent (in front of the anal fin) 

 and cut straight forward to a point between the opercula. 

 Care must be exercised in opening the chamber about the 

 heart ; this lies between the gill chambers. 



The various organs, so far as possible, should be carefully 

 drawn out and separated, in order that their structure may 

 be distinguished. 



The pupil should identify the following parts : — 



I. Body cavity, the entire internal space, divided by a 

 membrane, false diaphragm, into a large abdominal cavity 



