66 PELAGIC FAUNA 



ton algae, referred to in other chapters, which forms the ultimate food of 

 all marine animals. Many small animals in these layers live directly on 

 this vegetable plankton; they are then devoured by other animals, these in 

 their turn serving as food for still larger animals. In the perpetual dark- 

 ness beyond the limits of light penetration is the "bathypelagic" region, 

 where only animals live. In the absence of plants these have to live on 

 other animals, and perhaps to some extent on bacteria, which recent 

 research suggests play a considerable part in the economy of the sea. By 

 means of this food chain the production of organic matter by plant plank- 

 ton, or phytoplankton, ultimately benefits even the bottom-living animals. 



Although the prime object of the Galathea Expedition was the study 

 of abyssal fauna, it followed as a matter of course that we should also 

 study pelagic animals. The results were impressive. We found many new 

 species and showed that many others have a much wider distribution 

 than had been supposed. 



The pelagic fauna is so diverse and embraces so many of the principal 

 groups of the animal kingdom that it will be possible to deal with only a 

 few of the most interesting of the animals found. The large gear which 

 we used fished much greater depths than ever before, bringing up crea- 

 tures from previously unknown regions. Whenever we could we also 

 fished for pelagic animals near the surface, especially in coastal waters, 

 where large-scale expeditions have not devoted much attention to the 

 pelagic fauna. 



Standing under the ship's awning gazing down at the clear blue water, 

 we saw little of the fauna which we knew to be there. We would catch a 

 glimpse of a brightly coloured sea-snake, or a jellyfish with beautiful colo- 

 ration. Flying-fishes being blue, we did not see them till they leapt from 

 the water and became airborne. Many surface animals seek shade from 

 the fierce light of the midday sun at lower depths, but though we knew 

 they were there we did not see them even in the morning or evening, as 

 they are more or less camouflaged. They may have many different colours: 

 brown, yellow, and reddish-yellow are common, and pursuers will be 

 deceived by striped and spotted coloration. But the predominant colour, 

 especially in the Tropics, is blue. Many are pellucid, so that only a few 

 of their organs, such as the eyes and the stomach, may be visible when 

 they are swimming. Most fishes have dark backs and silvery sides, colours 

 — or lack of colours — which presumably make them less conspicuous 

 and so protect them from their enemies. In the sea as everywhere in 

 nature the law of life is to eat and avoid being eaten ! 



Flying-fish are always interesting (Fig., p. 65). Occasionally we would 



