CHAPTER VI. 



THE FISH. 



Almost any kind of fish will do for this study. 

 These directions are written for the perch or the sun- 

 fish. 



1. Measure the length, from the tip of the snout 

 to the base of the tail. Measure the depth, the great- 

 est distance between dorsal and ventral sides ; width, 

 the greatest thickness from right to left ; length of 

 the head, from the tip of the snout to the tip of the 

 bony part of the flap on the side of the body. How 

 many times is the depth, the width, and the length of 

 the head, contained in the length of the fish? 



2. Find the caudal fin, at the tail ; the dorsal, on 

 the back ; anal fin, the single fin below. These are 

 the unpaired or median fins. 



3. The pectoral fins are, the front pair of paired 

 fins. The ventral fins are the hind pair of paired 

 fins. 



4. Study each fin. Find two kinds of fin rays, 

 and a membrane covering the rays. Is the membrane 

 double or single? 



5. The stiff, pointed rays are the spinous rays. 

 The others are the soft rays or jointed rays. How 

 many rays of each kind has each fin? D. III., 10, 

 means that the dorsal fin (D) has three (III.) spinous 

 rays, and ten (10) soft rays. So indicate the number 

 and kind of rays in each fin. 



6. Study the rays. Do they branch ? Draw care- 

 fully one of the soft rays. Sketch each fin. 



