lilgure 25» Pilchard scale having three annuli, mounted in glycerine. 

 THIhen mounted in any liquid medium, particularly those with high 

 refractive index, pilchard scales become transparent and the surface 

 structure loses clarity of detail. This effect increases with time, 

 and after a few weeks, a scale so mounted becomes so transparent as 

 to be almost completely invisible , and can then be detected only by 

 dose scrutiny at a sharp angle. Body length of fish, 215 nmi.j 

 caught August 3, 1939. 



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