22 MARVELS OF FISH LIFE 
shark and the seal so that they are not easily detected 
by the little fish, and his chances of surviving would be 
small were it not that he in his turn is shaded and 
coloured so as to afford him protection from these 
enemies. 
In order to describe the various concealing devices 
found in the fish world, I propose to take six fishes, 
differently shaped, coloured and marked, and to deal 
with each in turn; first, describing how they appear to 
us when seen out of the water, or in a tank or bowl, and 
then how they appear to other fish when seen in their 
natural surroundings. 
Let us start with the dace as an example of silvery- 
bodied fishes. When seen out of the water the back 
is dark, the under-surface white, and the sides a silvery 
colour. When seen in the water fish of this type be- 
come inconspicuous because of the fact that their bodies 
are perfect reflectors. 
A dace at the bottom of a dark, deep hole appears 
almost black, but should this fish swim straight up, 
his body would exactly reflect the shade and colours of 
the strata of water he passed through, until at the top 
he would be seen as a light greenish-blue shimmering 
form under the surface of the rippling water. If seen 
amongst dead sedges the dace is yellow, if amongst 
green weeds he appears to be green, and if the weeds 
are sufficiently near to his body each stem and leaf is 
reflected. 
As an illustration of how the dace reflects any par- 
