32 MARVELS OF FISH LIFE 



photograph was again taken by a front light, and he is 

 still revealed by his dark back and white under-surface. 

 The stone-like markings in themselves were insufficient 

 to conceal him. In the bottom illustration the fish 

 was photographed by a top light only, and now we see 

 how effectively the markings seen on a uniformly shaded 

 fish conceal him. 



The perch illustrates the value of reed-like markings, 

 for, in addition to his dark back and white under-surface, 

 he is crossed by five or more bars, as shown in the 

 illustration of a perch photographed in a tank by a 

 front light. When seen under natural conditions, the 

 dark back and white under-surface again become of a 

 uniform shade. This uniform shade in itself would 

 render the body of the perch conspicuous by interrupting 

 the reed scenery beyond. But the markings break up 

 the uniformly shaded body of the fish, and at the same 

 time merge with the pattern formed by the reeds. 



Water has a bluring effect, and when a perch is seen 

 through two or three feet of this medium, the bar mark- 

 ings do not appear to be on the fish at all, but to be 

 part of the reeds themselves. As a result, the eye of 

 the observer is not arrested by the form of the fish, 

 but is carried to the reeds beyond, and thus the perch 

 escapes detection. 



Thayer, the American artist and naturalist, in his 

 exceedingly interesting book " Concealing Coloration in 

 the Animal World," has brought into prominence this 

 principle, of how the dark back and lighter under-parts 



