io ANIMAL LIFE UNDER WATER 



markings on the body of the fish.' On the 

 present occasion I take the opportunity of show- 

 ing rather an exceptional colour photograph of 

 the common brown trout. I hardly think it is 

 realised that such a highly pigmented fish as the 

 brown trout reflects to the extent shown in the 

 illustration. Concealment by reflection among 

 fishes is to a great extent due to the presence of 

 iridocytes in the skin of the fish. 



Under certain conditions many forms of sub- 

 aquatic life are equally well protected by 

 reflection from the fact that they are white. 



The reflecting power of a white object under 

 the water is shown by an experiment illustrated 

 on the colour plate opposite. 



An observation pond was allowed to become 

 overgrown with confervas. The pond was 

 emptied and the green growth removed from the 

 plate glass of the observation chamber ; a stick, 

 with squares of white cardboard attached, was 

 then stuck in the empty pond. The cards were 

 slightly tilted towards the bed of the pond. 

 Seen thus, the surface of the outside card re- 

 tained its whiteness, but as soon as clear water 

 was run into the pond this white card reflected 

 the green bottom as shown. In this experiment 



