Pisces. 



77 



che kidney, lying anterior to the air bladder and dorsal to the 

 gullet. See if you can trace the kidneys to the urinary bladder. 



1 6. If the mouth and gill covers are not already widely 

 stretched, loosen one or both tacks and set them farther out. 

 Examine the branchiostegal membrane and its supporting rays. 

 Look into the mouth to see the relations between the gills, gill 

 covers, and gullet. Note also the position of the tongue. Cut 

 forward and inward on each side between the gills and the gill 

 covers till the two cuts meet in front of the tongue. Again 

 examine the gills from the front. Pull up the tacks and press the 

 ventral ends of the gills toward the roof of the mouth. Study the 

 action of the joints in the gills. What is the use of the gill rakers? 



Observe, where the gills unite above and below, patches of 

 closely set teeth, the superior and inferior pharyngeal teeth. The 

 bones supporting these teeth, above and below, are the pharyngeal 

 bones. Again depress and raise the lower ends of the gills, ob- 

 serving how the pharyngeal teeth are brought together. What is 

 the probable use of these teeth, and what is the work done by the 

 teeth previously examined ? 



Remove the gills by cutting the thin membrane back of them, 

 between the isthmus and their ventral ends ; above, cut close to 

 the base of the skull. 



17. Examine the bones in the posterior border of the gill 

 opening ; these are together called the pectoral arch. Cut away 

 the flaps of the body wall bearing the fins. 



1 8. Note also the bones supporting the pelvic fins; these are 

 considered as representing the pelvis. In the higher fishes the 

 pelvis is fastened to the clavicle ; in the lower fishes it is separate 

 from the rest of the skeleton and embedded in the flesh. How is 

 it in the specimen you are studying? Carefully remove the pelvic 

 fins, with the bones which support them ; examine and describe 

 them, after scraping away all muscles and other soft tissues. 



19. Hold the fish in the left hand, with its back up and its 

 head away from you ; insert the point of one blade of the scissors 

 at the base of the caudal fin and cut the skin forward, passing to 



