CHAPTER X 



FISHES 



studied. 



Suggestions. — 



The behavior of a 



live fish in clear 



water, preferably in 



a glass vessel or an 



aquarium, should be 



A skeleton may be 



prepared by placing a fish in 



the reach of ants. Skeletons 



of animals placed on ant beds 



are cleaned very thoroughly. 



The study of the perch, that follows, will apply to almost any 



common fish. 



Movements and External Features. — What is the gen- 

 eral shape of the body of a fish ? How does the dorsal, or 

 upper, region differ in form from the ventral ? Is there a 

 narrow part or neck where the head joins the trunk? 

 Where is the body thickest ? What is the ratio between 

 the length and height ? (Fig. 209.) Are the right and left 

 sides alike ? Is the symmetry of the fish bilateral or 

 radial ? 



The body of the fisli may be divided into three regions, 

 — the head, trunk, and tail. The trunk begins with the 

 foremost scales ; the tail is said to begin at the vent, or 

 anus. Which regions bear appendages? Is the head 

 movable independently of the trunk, or do they move 

 together ? State the advantage or disadvantage in this. 

 Is the body depressed (flattened vertically) or compressed 



109 



