120 PISCES (the fish) 



nostrils, ear, eye, gills, fins, lateral line, and vent. Number 

 these points in your sketch and write these numbers and the 

 names below it. 



17. The Skin. With sharp scissors cut through the skin, 

 and with forceps peel off a portion of it so as to expose the flesh 

 or muscles. 



(1) Is the skin thick or thin? 



(2) How is it fastened to the flesh? 



(3) Use? 



18. The Muscles. 



(1) How are they arranged on the body? 



(2) Estimate what proportion of the whole fish is muscle. 



(3) Why so much muscle? 



(4) Are there any nerves in the muscles? Use? 



(5) Do you see any blood-vessels in the muscles? Use? 



19. The Respiratory Organs. 



(1) Raise the gill cover and count the gills. How many? 



(2) Color? 



(3) How are the gills connected with the mouth? 



(4) How many gill arches? 



(5) How many gill filaments on one arch? How many in 



all? Use? 



(6) What does the fish breathe? How does it obtain it? 



(7) How does the water, with the air mechanically mixed 



with it, pass over the gifls; from the mouth back 

 over the gills, or through the gill openings forward 

 and out at the mouth? 



B. Internal Morphology 



1. The Digestive Organs. Cut forward from the vent to 

 the gills and remove the muscles from one side of the body, 

 exposing the internal organs. Is the body-cavity large or 

 small? 



(1) Peritoneum. 



(a) Color? 



(b) Surface rough or smooth? Why? 



(c) Use? 



