BONY -FISH. 23 



How many fins can you find? How many are in pairs? 

 How many single? Are any in the median line of the 

 body? Is there a skeleton to the fins? Could you regard 

 a fin as a fold of the skin supported on soft or spiny rays? 



Of the median fins the caudal terminates the tail, the 

 dorsal is on the back, the anal is just behind the vent. 

 Are there two of any of these? Are the upper and lower 

 lobes of the caudal equal (homocercal) or unequal (hetero- 

 cercal] ? 



Can the paired fins be compared in position to your 

 own limbs? By feeling, ascertain if there be any solid 

 support in the body for either pair. How does this con- 

 dition compare with that in man? The anterior paired 

 fins are the pectorals; the posterior are the pelvic or ven- 

 tral fins. 



INTEGUMENT. On the trunk and tail are scales. Are 

 they regularly arranged? Are there scales on the head? 

 Do they extend on the fins? Is there any skin over the 

 scales? Is there skin on the head? Can you trace the 

 skin of the head into the mouth? Find dark pigment 

 spots on the body. Does the color belong to the scale or 

 to what? Settle by pulling out a scale. 



Notice the lateral line running along a row of scales on 

 either side of the body. Does it continue on the head? 

 Examine the scales with a hand-lens and see what causes 

 the line. Examine any scale with the hand-lens. Is its 

 margin regularly rounded (cycloid), or is it toothed or 

 spiny behind (ctenoid)? 



THE HEAD. How many eyes are there? Where are 

 they placed? Are they movable? Are eyelids present? 

 Notice in each eve the colored iris around the central 



*/ 



black pupil.* 



* Here as elsewhere in these directions color is given as in the 

 fresh fish. In preservative fluids colors change and fade. 



