Body Covering 25 



As ichthyologists put it, it is "naked." Some, like the com- 

 mon catfish, remain naked throughout life, but the great 

 majority decide to give up nakedness before they are very 

 old. The size at which they first clothe themselves varies. 

 The striped bass, for instance, is only half an inch long 

 when he succumbs to modesty, whereas the various salmons 

 and trouts range between one and two inches. In any case, 

 at the appointed length, the scales begin to appear, and the 

 so-called nuclei are formed under the skin, of such a size 



Hedd of Fish 



Surface of Skin 



Figure 5. DIAGRAMMATIC CROSS-SECTION OF SCALES AND 



SKIN 



that, just touching each other, they just about cover the fish. 

 The forward end of each scale is embedded in the dermis 

 (Figure 5), and the free after-end comes eventually to cover 

 the forward end of the scale next behind it, like the shingles 

 on a roof. This free end, which is the only part which we 

 see when we look at a fish, is very much smaller than the 

 covered part, so that by far the larger portion of each scale 

 is hidden from view. In the black-bass and its relatives, the 

 scale has radial furrows, and the exposed after-end is cov- 

 ered with tiny teeth, which is what makes the fish feel rough 

 to the touch. This type of scale is called ctenoid (meaning 

 comblike). In the trouts and salmons, the whole scale, in- 

 cluding the exposed after portion, is smooth, and is called 

 cycloid (Plate I). 



As the fish grows, he must continue to be covered by over- 

 lapping scales. This effect he does not achieve, as might be 

 expected, by adding to the number of his scales. The number 



