116 THE MICROSCOPE. Aug. 



but constant in form (fig. 15). By transmitted light these 

 are so transparent as to be hardly visible, but with re- 

 flected light, or the direct rays of the sun, they sparkle 

 like plates of polished steel. Each of these crystals is 

 constantly vibrating and quivering, and giving one the 

 impression that it is alive although taken from a fish 

 which has been dead some days. This motion is prob- 

 ably due to the vibrations of the water, but it gives that 

 beautiful play of light which we so much admire in the 

 Gold-fish, Silver-fish and others. Notice that in the highly 

 colored fish the exposed part of the scale is more trans- 

 parent than the other portion (fig. 5). 



The Ctenoid. — These scales have the same general 

 structure as the Cycloid except tha't at the exposed end 

 they are furnished with teeth arranged something like the 

 teeth in a comb. In some scales they are small and set 

 closely together as in the Perch (figs. 4 and 7, 5 diam.), 

 while in others they are larger and much farther apart, 

 as in the Sole (fig. 8, 8 diam.). 



In some scales the laminse show as concentric lines on 

 the outer part of the scale only, the interior being some- 

 what granular in appearance, as in figs. 4 and 10. The 

 scales on a single fish vary much in size and foi-m, figs. 

 9, 10, 11 and 12 (8 diam.) coming from the same fish, 

 — one that was sold in the market as a Flounder. Fig. 9 

 represents a scale from the ventral or white side. 

 Figs. 10, 11 and 12 represent those from the dorsai, and 

 fig. 11 one from near the tail. Fig. 5 (5 diam.) is 

 from near the tail of a Herring. Scales from the central 

 portion of the body of the Herring have somewhat the 

 same outline as shown in fig. 7. It is to be noticed in 

 fig. 8, Sole (8 diam.), that the radial lines look as though 

 they had been split in places and the spaces filled in 

 with a clear transparent substance, but this is not the 

 case. It is claimed that if a thin vertical section of a 

 scale of the carp, which is taken as a representative of 



