VERTEBRATES 

 THE FISH 



Perca sp. 



[Note. — These directions with but slight alterations will answer 

 for the study of any fish in the markets.] 



External Morphology. — (i) Straighten the fish out 

 in the dissecting pan and measure its longitudinal and lat- 

 eral axes. How does the dorsal differ from the ventral 

 side? How is the head joined to the body? How does the 

 right side differ from the left ? Animals that have the right 

 and left sides alike are said to be bilaterally symmetrical. 

 Has the fish perfect bilateral symmetry ? 



(2) How many iins are there? How are they arranged 

 with reference to one another? The fins at the anterior 

 end on the side are the pectoral fins. Examine one care- 

 fully. Of what does it seem to be composed? The spines 

 that run through it are called rays. Are all the rays bony? 

 Examine a piece that is not bony through the microscope, 

 low power. 



How is the fin attached to the body? Are all the fins 

 attachedin the same way? 



Draw pectoral fin (X2). 



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