THE CIRCULATION OF MATTER 



composition of the sea -water, partly on the tempera- 

 ture and partly on the amount of sunlight. Careful 

 records show clearly that there is a close correspon- 

 dence between the number of bright sunny days and 

 the size of the catches of mackerel. Thus, if all 

 flesh is in the long run grass, all fish is in the long 

 run seaweed, animalcule, and the minute fragments 

 of seashore plants which form what we may call 

 "sea-dust." 



If we pass in imagination from the sunlit open sea 

 to the floor of the deep sea that strange, dark, 

 cold, silent, monotonous world we find that there 

 is not really any exception, although there are no 

 plants at all. We find that deep-sea fish feed on 

 deep-sea fish, and fish on crustacean, and crustacean 

 on worm, and worm on still smaller fry. But as 

 they cannot all be living on one another, we must 

 look for some outside source of supply. That is 

 to be found in the ceaseless shower of more or less 

 microscopic dying animals which sink down from 

 the surface waters overhead (where they feed in 

 part on microscopic plants) down, it may be, 

 through miles and miles of water, like snowflakes 

 on a quiet winter day. Again we see what is meant 

 by the circulation of matter. Again we see how 

 the world goes round. 



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