Pisces. 



73 



along the posterior, outer border of the bony arch in which run 

 the blood tubes. Look on the inside of the gill cover for a red 

 spot, the false gill. 



8. Observe the arrangement of the scales. Pull out a scale and 

 study its shape and the radiating and concentric markings. Com- 

 pare its inner and outer surfaces, its anterior and posterior margins ; 

 make a drawing of it, naming its parts ; pull out a scale from a 

 black spot ; compare that part of its surface which was exposed 

 with the part overlapped by other scales ; scrape the portion that 

 was exposed ; thrust one point of the forceps under the hind edge 

 of a scale, and watch closely this edge, while slowly raising it, to 

 see that a thin skin covers it and passes on to the scale behind. 

 This thin outer skin is chiefly epidermis. In this epidermis lie the 

 black pigment cells which make the dark spots. A scale with a 

 smooth hinder border is a cycloid scale; if the hinder portion is 

 toothed or spiny, the scale is ctenoid. 



9. A raised line along the side is the lateral line. Remove 

 one of the scales on this line, and find what makes the line. Is 

 the line continuous? 



10. Make a drawing of the fish as seen from one side, naming 

 all the parts visible. Describe fully all the parts above noted, 

 including the general color and markings. 



Use Jordan's Manual of the Vertebrates for finding the names 

 of the fishes of your neighborhood. 



DISSECTION OF A FISH. 



Dissect on a board covered with paper. A few carpet tacks 

 will be needed. 



Hold the fish with its back in the palm of the left hand and the 

 tail toward you. Thrust the point of one blade of the scissors 

 obliquely forward through the body wall just in front of the anus, 

 and continue the cut forward half an inch. Now rest the fish on 

 its back and get hold of the edge of the cut with the forceps ; 

 as you cut forward in the middle line lift the edge of the body 

 wall to see that no internal organ is injured. When the pelvic fins 



