16 ANIMAL LIFE UNDER WATER 



to resemble colour reflected from marine vegeta- 

 tion. 



Several red and brown seaweeds seen by 

 transmitted light appear red or brown, but when 

 seen against a dark background at various points 

 they reflect a brilliant bluish colour. One of the 

 plants to show this best is chondrus. In certain 

 positions the whole side of rock covered with 

 this seaweed flashes blotches and streaks of 

 bluish-purple light. 



Many forms of marine life which usually 

 inhabit rocky seaweed-covered areas show bluish- 

 purple markings, e.g. lobsters and crabs. The 

 swimming crab (Portunus puber) shows this par- 

 ticularly well, and in pools on the Cornish coast 

 I have frequently found a small brown anemone 

 with purple markings exactly the colour of the 

 purple light reflected from chondrus. 



The next point to be considered is " Flash." 

 When a reflecting body in the water turns so 

 as to catch the light from above, there is a flash 

 of white light. 



These flashes of light from the bodies of fish, 

 birds and lures have such an important bearing 

 on feeding habits under the water that I must 

 deal with "flash" in some detail. 



